Post-deposition early-phase migration and retention behavior of radiocesium in a litter-mineral soil system in a Japanese deciduous forest affected by the Fukushima nuclear accident

Koarashi, Jun; Nishimura, Shusaku; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Takeuchi, Erina; Muto, Kotomi

Chemosphere, 165, p.335 - 341, 2016/12

https://doi.org/10.1016/j.chemosphere.2016.09.043

We established field lysimeters in a Japanese deciduous broad-leaved forest soon after the Fukushima nuclear accident to continuously monitor the downward transfer of Cs at three depths: the litter-mineral soil boundary and depths of 5 cm and 10 cm in the mineral soil. Observations were conducted at two sites within the forest from May 2011 to May 2015. Results revealed similar temporal and depth-wise variations in Cs downward fluxes for both sites. The Cs downward fluxes generally decreased year by year at all depths, indicating that Cs was rapidly leached from the forest-floor litter layer and was then immobilized in the upper (0-5 cm) mineral soil layer through its interaction with clay minerals. The decreased inventory of mobile (or bioavailable) Cs observed during early stages after deposition indicates that the litter-soil system in the Japanese deciduous forest provides only a temporary source for Cs recycling in plants.

Field test around Fukushima Daiichi Nuclear Power Plant site using improved Ce:Gd(Al,Ga)O scintillator Compton camera mounted on an unmanned helicopter

Shikaze, Yoshiaki; Nishizawa, Yukiyasu; Sanada, Yukihisa; Torii, Tatsuo; Jiang, J.*; Shimazoe, Kenji*; Takahashi, Hiroyuki*; Yoshino, Masao*; Ito, Shigeki*; Endo, Takanori*; et al.

Journal of Nuclear Science and Technology, 53(12), p.1907 - 1918, 2016/12

https://doi.org/10.1080/00223131.2016.1185980

The Compton camera was improved for use with the unmanned helicopter. Increase of the scintillator array from 44 to 88 and expanse of the distance between the two layers contributed to the improvements of detection efficiency and angular resolution, respectively. Measurements were performed over the riverbed of the Ukedo river of Namie town in Fukushima Prefecture. By programming of flight path and speed, the areas of 65 m 60 m and 65 m 180 m were measured during about 20 and 30 minutes, respectively. By the analysis the air dose rate maps at 1 m height were obtained precisely with the angular resolution corresponding to the position resolution of about 10 m from 10 m height. Hovering flights were executed over the hot spot areas for 10-20 minutes at 5-20 m height. By using the reconstruction software the -ray images including the hot spots were obtained with the angular resolution same as that evaluated in the laboratory (about 10).

Development of three-dimensional reactor analysis code system for accelerator-driven system, ADS3D and its application with subcriticality adjustment mechanism

Sugawara, Takanori; Nishihara, Kenji; Iwamoto, Hiroki; Oizumi, Akito; Tsujimoto, Kazufumi

Journal of Nuclear Science and Technology, 53(12), p.2018 - 2027, 2016/12

https://doi.org/10.1080/00223131.2016.1179600

In order to perform the parametric survey for an Accelerator-Driven System (ADS) core with the subcriticality adjustment mechanism, a new calculation code system, ADS3D, was developed on MARBLE which is a comprehensive and versatile framework for reactor analysis. ADS3D can calculate the transportation of neutrons, the burn-up performance and the fuel exchange by deterministic method in three-dimensional calculation models. The application of ADS3D was also presented for the neutronics design of the ADS core with the control rod. Through the neutronics calculation, it was shown that the maximum proton beam current was decreased from 20.5mA to 11.6mA by the installation of control rods.

Development of an extraction chromatography method for the analysis of Zr, Nb, and Mo in radioactive contaminated water generated at the Fukushima Daiichi Nuclear Power Station

Shimada, Asako; Kameo, Yutaka

Journal of Radioanalytical and Nuclear Chemistry, 310(3), p.1317 - 1323, 2016/12

https://doi.org/10.1007/s10967-016-5008-x

Impact hammer test of ITER blanket remote handling system

Noguchi, Yuto; Maruyama, Takahito; Ueno, Kenichi; Komai, Masafumi; Takeda, Nobukazu; Kakudate, Satoshi

Fusion Engineering and Design, 109-111(Part B), p.1291 - 1295, 2016/11

https://doi.org/10.1016/j.fusengdes.2015.12.040

This paper reports the impact hammer test of the full-scale mock-up of ITER Blanket Remote Handling system (BRHS). Since the BRHS, which is composed of the articulated rail and the vehicle manipulator which travels on the rail deployed in the vacuum vessel, is subjected to the floor response spectrum with 14 G peak at 8 Hz, evaluation of dynamic response of the system is of essential importance. Recently impact hammer testing on the full-scale mock-up of the BRHS was carried out to verify the finite element method seismic analysis and to experimentally obtain the damping ratio of the system. The results showed that the mock-up has a vertical major natural mode with a natural frequency of 7.5 Hz and a damping ratio of 0.5%. While higher structural damping ratios is predicted in a high amplitude excitation such as major earthquake, it was confirmed that the experimental natural major frequencies are in agreement with the major frequencies obtained by elastic dynamic analysis.

New remarks on KERMA factors and DPA cross section data in ACE files

Konno, Chikara; Sato, Satoshi; Ota, Masayuki; Kwon, Saerom; Ochiai, Kentaro

Fusion Engineering and Design, 109-111(Part B), p.1649 - 1652, 2016/11

https://doi.org/10.1016/j.fusengdes.2015.10.038

Recently we have examined KERMA factors and DPA cross section data in the latest official ACE files of JENDL-4.0, ENDF/B-VII.1, JEFF-3.2 and FENDL-3.0 in more detail and we found out the following new problems on the KERMA factors and DPA cross section data. (1) NJOY bugs and incorrect nuclear data generated KERMA factors and DPA cross section data of no increase with decreasing neutron energy in low neutron energy. (2) Huge helium production data caused drastically large KERMA factors and DPA cross section data in low neutron energy. (3) It seemed that NJOY could not adequately process capture cross section data in File 6, not File 12-15. (4) KERMA factors with the kinematics method are not correct for nuclear data libraries without detailed secondary particle data (energy-angular distribution data). These problems should be resolved based on our study.

Numerical study of sediment and Cs discharge out of reservoirs during various scale rainfall events

Kurikami, Hiroshi; Funaki, Hironori; Malins, A.; Kitamura, Akihiro; Onishi, Yasuo*

Journal of Environmental Radioactivity, 164, p.73 - 83, 2016/11

AA2015-0827.pdf:2.61MB

https://doi.org/10.1016/j.jenvrad.2016.07.004

We performed simulations using the three-dimensional finite volume code FLESCOT to understand sediment and radiocesium transport in generic models of reservoirs with parameters similar to those in Fukushima Prefecture. The simulations model turbulent water flows, transport of sediments with different grain sizes, and radiocesium migration both in dissolved and particulate forms. To demonstrate the validity of the modeling approach for the Fukushima environment, we performed a test simulation of the Ogaki Dam reservoir over a typhoon. We simulated a set of generic model reservoirs systematically varying features such as flood intensity, reservoir volume and the radiocesium distribution coefficient. The results ascertain how these features affect the amount of sediment or Cs discharge downstream from the reservoirs, and the forms in which Cs is discharged. Silt carries the majority of the radiocesium in the larger flood events, while the clay-sorbed followed by dissolved forms are dominant in smaller events. The results can be used to derive indicative values of discharges from Fukushima reservoirs under arbitrary flood events.

Measurements of -ray emission probabilities of Am and Np

Terada, Kazushi; Nakamura, Shoji; Nakao, Taro; Kimura, Atsushi; Iwamoto, Osamu; Harada, Hideo; Takamiya, Koichi*; Hori, Junichi*

Journal of Nuclear Science and Technology, 53(11), p.1881 - 1888, 2016/11

https://doi.org/10.1080/00223131.2016.1174167

-ray emission probabilities of Am and Np have been precisely measured with - and -ray spectroscopic methods. The activities of Am samples were determined by measuring alpha particles using a Si semiconductor detector. -rays emitted from the samples were measured with a planar type High-Purity Germanium (HPGe) detector. An efficiency curve of the Ge detector was derived with uncertainties of 0.7% from 50 to 1332 keV and 1.3% below 50 keV by combining measured efficiencies and Monte Carlo simulation. The -ray emission probabilities for the major -rays of these nuclides were determined with uncertainties less than 1.2%.

The Effect of azimuthal temperature distribution on the ballooning and rupture behavior of Zircaloy-4 cladding tube under transient-heating conditions

Narukawa, Takafumi; Amaya, Masaki

Journal of Nuclear Science and Technology, 53(11), p.1758 - 1765, 2016/11

https://doi.org/10.1080/00223131.2016.1158671

Magnetic structure of divalent europium compound EuGa studied by single-crystal time-of-flight neutron diffraction

Kawasaki, Takuro; Kaneko, Koji; Nakamura, Ai*; Aso, Naofumi*; Hedo, Masato*; Nakama, Takao*; Ohara, Takashi; Kiyanagi, Ryoji; Oikawa, Kenichi; Tamura, Itaru; et al.

Journal of the Physical Society of Japan, 85(11), p.114711_1 - 114711_5, 2016/11

https://doi.org/10.7566/JPSJ.85.114711

Development of probabilistic risk assessment methodology against extreme snow for sodium-cooled fast reactor

Yamano, Hidemasa; Nishino, Hiroyuki; Kurisaka, Kenichi

Nuclear Engineering and Design, 308, p.86 - 95, 2016/11

https://doi.org/10.1016/j.nucengdes.2016.08.006

This paper describes snow probabilistic risk assessment (PRA) methodology development through external hazard and event sequence evaluations mainly in terms of decay heat removal (DHR) function of a sodium-cooled fast reactor (SFR). Using recent 50-year weather data at a typical Japanese SFR site, snow hazard categories were set for the combination of daily snowfall depth (snowfall speed) and snowfall duration which can be calculated by dividing the snow depth by the snowfall speed. For each snow hazard category, the event sequence was evaluated by event trees which consist of several headings representing the loss of DHR. Snow removal action and manual operation of the air cooler dampers were introduced into the event trees as accident managements. Access route failure probability model was also developed for the quantification of the event tree. In this paper, the snow PRA showed less than 10/reactor-year of core damage frequency. The dominant snow hazard category was the combination of 1-2 m/day of snowfall speed and 0.5-0.75 day of snowfall duration. Importance and sensitivity analyses indicated a high risk contribution to secure the access routes.

LaBr -ray spectrometer for detecting B in debris of melted nuclear fuel

Koizumi, Mitsuo; Tsuchiya, Harufumi; Kitatani, Fumito; Harada, Hideo; Heyse, J.*; Kopecky, S.*; Mondelaers, W.*; Paradela, C.*; Schillebeeckx, P.*

Nuclear Instruments and Methods in Physics Research A, 837, p.153 - 160, 2016/11

https://doi.org/10.1016/j.nima.2016.09.015

Measurement of the isomer production ratio for the Cd()Cd reaction using neutron beams at J-PARC

Hayakawa, Takehito*; Toh, Yosuke; Huang, M.; Shizuma, Toshiyuki*; Kimura, Atsushi; Nakamura, Shoji; Harada, Hideo; Iwamoto, Nobuyuki; Chiba, Satoshi*; Kajino, Toshitaka*

Physical Review C, 94(5), p.055803_1 - 055803_6, 2016/11

https://doi.org/10.1103/PhysRevC.94.055803

Suppression of radiation-induced point defects by rhenium and osmium interstitials in tungsten

Suzudo, Tomoaki; Hasegawa, Akira*

Scientific Reports (Internet), 6, p.36738_1 - 36738_6, 2016/11

https://doi.org/10.1038/srep36738

Modeling of the evolution of radiation-induced defects is important for finding radiation-resistant materials, which would be greatly appreciated in nuclear applications. We apply the first principles method combined with kinetic Monte Carlo to indicate a mechanism to mitigate the effect of radiation by adding particular solute elements that change the migration dimension of interstitials in W crystals. The resultant mechanism is applicable to any body-centered-cubic (BCC) metals whose SIAs have one-dimensional (1D) motion and is expected to provide a general guideline for computational design of radiation-resistant alloys in the field of nuclear applications.

Age and speciation of iodine in groundwater and mudstones of the Horonobe area, Hokkaido, Japan; Implications for the origin and migration of iodine during basin evolution

Togo, Yoko*; Takahashi, Yoshio*; Amano, Yuki; Matsuzaki, Hiroyuki*; Suzuki, Yohei*; Terada, Yasuko*; Muramatsu, Yasuyuki*; Ito, Kazumasa*; Iwatsuki, Teruki

Geochimica et Cosmochimica Acta, 191, p.165 - 186, 2016/10

https://doi.org/10.1016/j.gca.2016.07.012

Iodine distribution, speciation, and isotope ratio (I/I) in both rock and groundwater phases were determined to investigate long-term migration of iodine in diatomaceous and siliceous shale. It was suggested that I is released to the ground water during the progress of the maturation of organic matter. Dissociated I could move toward the surface because of the upward water flow driven by the compaction during burial diagenetic process. Thus, iodine rich brine is created by integration of iodine released from underlying formations. Because of low affinity of I to solid phase, released I remains in solution phase, and the concentration of the iodine in the solution has been possibly increasing during sedimentation history.

Full operation of JAEA Naraha Remote Technology Development Center

Daido, Hiroyuki

Hozengaku, 15(3), p.20 - 25, 2016/10

Naraha Remote Technology Development Center is open for various users to contribute to recovery of the coast area of Fukushima as well as the decommissioning of Fukushima Daiichi Nuclear Power Station. The center is located within a distance of 20 km from the Fukushima Daiichi station. This is the first development center funded by the Government near the Fukushima Daiichi. Many people expect that the center plays a significant role to contribute to the decommissioning of Fukushima Daiichi and recovery of Fukushima area from the hazards. The author describe details of the facility and our plan.

Rapid measurement scheme for texture in cubic metallic materials using time-of-flight neutron diffraction at iMATERIA

Onuki, Yusuke*; Hoshikawa, Akinori*; Sato, Shigeo*; Xu, P. G.; Ishigaki, Toru*; Saito, Yoichi*; Todoroki, Hidekazu*; Hayashi, Makoto*

Journal of Applied Crystallography, 49(5), p.1579 - 1584, 2016/10

AA2016-0186.pdf:1.13MB

https://doi.org/10.1107/S160057671601164X

Nuclear heat supply fluctuation tests by non-nuclear heating with HTTR

Inaba, Yoshitomo; Sekita, Kenji; Nemoto, Takahiro; Honda, Yuki; Tochio, Daisuke; Sato, Hiroyuki; Nakagawa, Shigeaki; Takada, Shoji; Sawa, Kazuhiro

Journal of Nuclear Engineering and Radiation Science, 2(4), p.041001_1 - 041001_7, 2016/10

https://doi.org/10.1115/1.4034320

The nuclear heat utilization systems connected to High Temperature Gas-cooled Reactors (HTGRs) will be designed on the basis of non-nuclear grade standards in terms of the easier entry of chemical plant companies and the construction economics of the systems. Therefore, it is necessary that the reactor operations can be continued even if abnormal events occur in the systems. The Japan Atomic Energy Agency has developed a calculation code to evaluate the absorption of thermal load fluctuations by the reactors when the reactor operations are continued after such events, and has improved the code based on the High Temperature engineering Test Reactor (HTTR) operating data. However, there were insufficient data on the transient temperature behavior of the metallic core side components and the graphite core support structures corresponding to the fluctuation of the reactor inlet coolant temperature for further improvement of the code. Thus, nuclear heat supply fluctuation tests with the HTTR were carried out in non-nuclear heating operation to focus on thermal effect. In the tests, the coolant helium gas temperature was heated up to 120C by the compression heat of the gas circulators in the HTTR, and a sufficiently high fluctuation of 17C by devising a new test procedure was imposed on the reactor inlet coolant under the ideal condition without the effect of the nuclear power. Then, the temperature responses of the metallic core side components and the graphite core support structures were investigated. The test results adequately showed as predicted that the temperature responses of the metallic components are faster than those of the graphite structures, and the mechanism of the thermal load fluctuation absorption by the metallic components was clarified.

Statistical analysis using the Bayesian nonparametric method for irradiation embrittlement of reactor pressure vessels

Takamizawa, Hisashi; Ito, Hiroto; Nishiyama, Yutaka

Journal of Nuclear Materials, 479, p.533 - 541, 2016/10

https://doi.org/10.1016/j.jnucmat.2016.07.035

To understand neutron irradiation embrittlement in high fluence regions, statistical analysis using the Bayesian nonparametric (BNP) method was performed for the Japanese surveillance and material test reactor irradiation database. The BNP method is essentially expressed as an infinite summation of normal distributions, with input data being subdivided into clusters with identical statistical parameters (such as mean and standard deviation) for each cluster to estimate shifts in ductile-to-brittle transition temperature (DBTT). Clusters typically depend on chemical compositions, irradiation conditions, and the irradiation embrittlement. Specific variables contributing to the irradiation embrittlement include the content of Cu, Ni, P, Si, and Mn in the pressure vessel, neutron flux, neutron fluence, and irradiation temperatures. It was found through numerous examinations that the measured shifts of DBTT correlated well with calculated ones. Data associated with the same materials were subdivided into the same clusters even if neutron fluences were significantly disparate among the results. This indicates that slowly developing or late-onset embrittlement mechanisms were not evident in the present study.

The FeSe(cr) solubility determined by solubility experiments of Se co-existing with Fe

Doi, Reisuke; Uchikoshi, Keiji*; Beppu, Hikari*

Journal of Nuclear Science and Technology, 53(10), p.1554 - 1562, 2016/10

https://doi.org/10.1080/00223131.2015.1137245

To determine log K for FeSe(cr) dissolution reaction, solubility experiments of Se co-existing with Fe were performed. Temperature was maintained at 348 K. Se concentration as a function of equilibration periods indicated that Se concentrations were similar at different equilibration periods. Only FeSe(cr) was detected as the Se solid phase by XRD analysis of the equilibrated precipitates. and pH of the equilibrated suspensions ranged from -188.6 to -4.9 mV vs. SHE and 6.00 to 8.76, respectively. Se and Fe are thermodynamically stable in this region. Interpretations using SIT model showed that the relationship between and the measured concentrations could be interpreted well when in the following equation n = 0.500.01 and log K = -17.240.31 : 4FeSe(cr) = 4nFe + Se + (8n - 2)e. The logK value calculated from the available thermodynamic data agrees with that determined here.

Evaluation of neutron nuclear data on mercury isotopes

Shibata, Keiichi

Journal of Nuclear Science and Technology, 53(10), p.1595 - 1607, 2016/10

https://doi.org/10.1080/00223131.2016.1140599

Neutron nuclear data on mercury isotopes have been evaluated for the next version of Japanese Evaluated Nuclear Data Library general-purpose file in the energy region from eV to 20 MeV. Resolved resonance parameters of Hg were supplemented with the data which had not been considered in the previous library. Unresolved resonance parameters were obtained by fitting to the total and capture cross sections calculated from nuclear models. A statistical model code CCONE was applied to evaluate cross sections above the resolved resonance region. Compound, pre-equilibrium and direct-reaction processes were considered for cross-section calculation. Coupled-channel optical model parameters were employed for the interaction between neutrons and mercury isotopes except Hg. The present results reproduce experimental data very well, and are much better than the JENDL-4.0 evaluation. The evaluated data are compiled into ENDF-formatted data files.

Cross-section adjustment methods based on minimum variance unbiased estimation

Yokoyama, Kenji; Yamamoto, Akio*

Journal of Nuclear Science and Technology, 53(10), p.1622 - 1638, 2016/10

AA2015-0624.pdf:0.29MB

https://doi.org/10.1080/00223131.2016.1146637

On the basis of the minimum variance approach, the unified formulation for three types of the cross-section adjustment methods has been derived in a straightforward way without assuming the normal distribution. These methods are intended to minimize the variances of the predicted target core parameters, the adjusted cross-section set, and the calculated integral experimental values. The first and the second methods are found to be slightly different from the extended and the conventional cross-section adjustment methods based on the Bayesian approach with the normal distribution assumption, respectively. However, they become equivalent in some cases and results. The third method is a new method, which is necessary from the viewpoint of the symmetry of the formulation. The derivation procedure proposed in the present paper is potentially applicable to developing more sophisticated cross-section adjustment methods because of the less assumptions on the probability density function.

Dynamic behavior of secondary electrons in liquid water at the earliest stage upon irradiation; Implications for DNA damage localization mechanism

Kai, Takeshi; Yokoya, Akinari*; Ukai, Masatoshi*; Fujii, Kentaro*; Watanabe, Ritsuko*

Journal of Physical Chemistry A, 120(42), p.8228 - 8233, 2016/10

https://doi.org/10.1021/acs.jpca.6b05929

Low energy secondary electrons produced by an ionizing radiation in a living cell may involve in formation of complexed DNA damage. We performed theoretical study for numerical calculation of dynamic behavior of the electrons to imply a formation of radiation damage to DNA. The decelerating electrons are gradually attracted to their parent cations by the Coulombic force within hundreds of fs, and about 12.6 % of electrons are finally distributed within 2 nm from the cations. The collision fraction of the ionization and excitation within 1 nm from the cation was estimated to be about 40 %. From those analyses, we suggested a process of DNA damage that the secondary electrons may cause highly localized lesions around a cation in DNA molecule through additional dissociative electron transfer as well as the ionization or the excitation if the electrons are ejected from DNA. The localized damage may involve ultimately in biological effects such as cell death or mutation induction.

Photostimulated luminescence applicable to pre-screening of potassium-rich phases in chondritic breccias

Yokoyama, Tatsunori; Misawa, Keiji*; Okano, Osamu*; Minowa, Haruka*; Fukuoka, Takaaki*

Journal of Radioanalytical and Nuclear Chemistry, 310(1), p.81 - 89, 2016/10

https://doi.org/10.1007/s10967-016-4846-x

The identification of alkali-rich components in extraterrestrial materials along with their separation from other constituents is indispensable for subsequent cosmochemical and isotopic studies. This paper presents a simple pre-screening method for such materials by autoradiography using imaging plates (IPs), which is applicable to identification of mm-sized samples containing ca. 30 g of potassium in the Yamayo-74442 chondrite. The detection limit of IPs was 1 mBq of K under 49 days exposure. The method provides an opportunity to screen meteorite materials non-destructively and to inexpensively check potassium-rich areas and suitable for the K-Ca and K-Ar (Ar-Ar) age determinations.

Report for nuclear reaction data and uncertainties for radiation damage at IAEA Technical Meeting (TM)

Iwamoto, Yosuke; Konno, Chikara

Kaku Deta Nyusu (Internet), (115), p.24 - 32, 2016/10

http://www.aesj.or.jp/~ndd/ndnews/pdf115/No115-06.pdf

The technical meeting of nuclear reaction data and uncertainties for radiation damage was held at IAEA Headquarters in June 2016. This Meeting was organized to implement the recommendation of the IAEA Coordinated Research Project (CRP) "Primary Radiation Damage Cross Sections" to analyze the accuracy and consistency of the radiation damage-relevant nuclear data in the major nuclear data evaluations with the eventual goal of identifying the most reliable data and providing quantitative uncertainty estimates. Participants have considered the status of the primary nuclear data, such as reaction recoils spectra in the latest releases of nuclear data libraries, and the ways of deriving the damage quantities KERMA, dpa cross sections and gas production cross sections as well as the recipes for an assessment of their uncertainties. This report contains the contemporary view of the Meeting participants on these issues in the form of a consolidated set of statements and recommendations.

Laser for nuclear decommissioning and its application to maintenance of social infrastructure which is a part of resilience of Japan; Towards utilization of laser techniques under the severe environment and movable laser applications

Daido, Hiroyuki

Kensetsu Kikai, 52(10), p.53 - 58, 2016/10

Laser application for nuclear decommisioning and meintenance of social infrastracture is described.

Time-of-flight neutron Bragg-edge transmission imaging of microstructures in bent steel plates

Su, Y. H.; Oikawa, Kenichi; Harjo, S.; Shinohara, Takenao; Kai, Tetsuya; Harada, Masahide; Hiroi, Kosuke; Zhang, S.*; Parker, J. D.*; Sato, Hirotaka*; et al.

Materials Science & Engineering A, 675, p.19 - 31, 2016/10

https://doi.org/10.1016/j.msea.2016.08.037

Reduction on high level radioactive waste volume and geological repository footprint with high burn-up and high thermal efficiency of HTGR

Fukaya, Yuji; Nishihara, Tetsuo

Nuclear Engineering and Design, 307, p.188 - 196, 2016/10

AA2015-0894.pdf:0.58MB

https://doi.org/10.1016/j.nucengdes.2016.07.009

Reduction of High Level Waste (HLW) and footprint in a geological repository due to high burn-up and high thermal efficiency of High Temperature Gas-cooled Reactor (HTGR) has been investigated. A helium-cooled and graphite-moderated commercial HTGR was designed as a Gas Turbine High Temperature Reactor (GTHTR300), and the features are significantly high burn-up of approximately 120 GWd/t, high thermal efficiency around 50%, and pin-in-block type fuel. The pin-in-block type fuel was employed to reduce processed graphite volume in reprocessing, and effective waste loading method for direct disposal is proposed by applying the feature in this study. As a result, it is found that the number of canisters and its repository footprint per electricity generation can be reduced by 60% compared with LWR representative case for direct disposal because of the higher burn-up, higher thermal efficiency, less TRU generation, and effective waste loading proposed in this study for HTGR. For disposal with reprocessing, the number of canisters and its repository footprint per electricity generation can be reduced by 30% compared with LWR because of the 30% higher thermal efficiency of HTGR.

Prospect for application of compact accelerator-based neutron source to neutron engineering diffraction

Ikeda, Yoshimasa*; Taketani, Atsushi*; Takamura, Masato*; Sunaga, Hideyuki*; Kumagai, Masayoshi*; Oba, Yojiro*; Otake, Yoshie*; Suzuki, Hiroshi

Nuclear Instruments and Methods in Physics Research A, 833, p.61 - 67, 2016/10

https://doi.org/10.1016/j.nima.2016.06.127

A compact accelerator-based neutron source has been lately discussed on engineering applications such as transmission imaging and small angle scattering as well as reflectometry. However, nobody considers using it for neutron diffraction experiment because of its low neutron flux. In this study, therefore, the neutron diffraction experiments are carried out using Riken Accelerator-driven Compact Neutron Source (RANS), to clarify the capability of the compact neutron source for neutron engineering diffraction. The diffraction pattern from a ferritic steel was successfully measured by suitable arrangement of the optical system to reduce the background noise, and it was confirmed that the recognizable diffraction pattern can be measured by the large sampling volume with 10 mm in cubic for an acceptable measurement time, i.e. 10 minutes. The minimum resolution of the 110 reflection for RANS is approximately 2.5 % at 8 s of the proton pulse width, which is insufficient to perform the strain measurement by neutron diffraction. The moderation time width at the wavelength corresponding to the 110 reflection is estimated to be approximately 30 s, which is the most dominant factor to determine the resolution. Therefore, refinements of the moderator system to decrease the moderation time are important to improve the resolution of the diffraction experiment using the compact neutron source. In contrast, the texture evolution due to plastic deformation was successfully observed by measuring a change in the diffraction peak intensity by RANS. Furthermore, the volume fraction of the austenite phase was also successfully evaluated by fitting the diffraction pattern using a Rietveld code. Consequently, RANS was proved to be capable for neutron engineering diffraction aiming for the easy access measurement of the texture and the amount of retained austenite.

Corrosion properties of Zircaloy-4 and M5 under simulated PWR water conditions

Shibata, Akira; Kato, Yoshiaki; Taguchi, Taketoshi; Futakawa, Masatoshi; Maekawa, Katsuhiro*

Nuclear Technology, 196(1), p.89 - 99, 2016/10

https://doi.org/10.13182/NT16-54

Cladding material Zircaloy-4 is gradually replaced by M5 (Zr-Nb alloy) and other new Nb added Zirconium alloys which are expected to have long operating life. Corrosion tests on Zircaloy-4 and M5 were performed in various hydrogen concentrations in water to research corrosion properties of those alloys. Specimens were exposed under PWR conditions. Increase of oxide layer was analysed by weight gain and observation. Electro chemical impedance spectroscopy was performed to compare corrosion properties. And effect of dissolved hydrogen concentration on increase of oxide layer of M5 is smaller than that of Zircaloy-4. M5 is less affected by local uniformity of dissolved hydrogen concentration and is more suitable as PWR fuel cladding. Results of Electro chemical spectroscopy shows that structural significant difference existed in oxidizing reaction of Zircaloy-4 and M5.

Fission fragments mass distributions of nuclei populated by the multinucleon transfer channels of the O + Th reaction

Lguillon, R.; Nishio, Katsuhisa; Hirose, Kentaro; Makii, Hiroyuki; Nishinaka, Ichiro*; Orlandi, R.; Tsukada, Kazuaki; Smallcombe, J.*; Chiba, Satoshi*; Aritomo, Yoshihiro*; et al.

Physics Letters B, 761, p.125 - 130, 2016/10

https://doi.org/10.1016/j.physletb.2016.08.010

Development of risk assessment methodology against natural external hazards for sodium-cooled fast reactors; Project overview and margin assessment methodology against volcanic eruption

Yamano, Hidemasa; Nishino, Hiroyuki; Kurisaka, Kenichi; Okano, Yasushi; Sakai, Takaaki; Yamamoto, Takahiro*; Ishizuka, Yoshihiro*; Geshi, Nobuo*; Furukawa, Ryuta*; Nanayama, Futoshi*; et al.

Proceedings of 11th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operation and Safety (NUTHOS-11) (USB Flash Drive), 12 Pages, 2016/10

This paper describes mainly volcanic margin assessment methodology development in addition to the project overview. The volcanic tephra could potentially clog filters of air-intakes that need the decay heat removal. The filter clogging can be calculated by atmospheric concentration and fallout duration of the volcanic tephra and also suction flow rate of each component. In this paper, the margin was defined as a grace period to a filter failure limit. Consideration is needed only when the grace period is shorter than the fallout duration. The margin by component was calculated using the filter failure limit and the suction flow rate of each component. The margin by sequence was evaluated based on an event tree and the margin by component. An accident management strategy was also suggested to extend the margin; for instance, manual trip of the forced circulation operation, sequential operation of three air coolers, and covering with pre-filter.

Experimental investigation on characteristics of mixed particle debris in sedimentation and bed formation behavior

Sheikh, M. A. R.*; Son, E.*; Kamiyama, Motoki*; Morioka, Toru*; Matsumoto, Tatsuya*; Morita, Koji*; Matsuba, Kenichi; Kamiyama, Kenji; Suzuki, Toru

Proceedings of 11th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operation and Safety (NUTHOS-11) (USB Flash Drive), 12 Pages, 2016/10

This paper reports an experimental evaluation on debris bed formation characteristics in core-disruptive accidents cogitating the heterogeneous mixture of particles. In the present study, to appraise the characteristics, a series of experiments was accomplished by gravity driven discharge of solid binary mixtures of particles as simulant debris from a nozzle into a quiescent water pool in isothermal condition at room temperature. Currently, two types of spherical particles, namely Alumina and stainless steel with different diameter are employed to study the effect of key experimental parameters on bed mound shape. In experimental investigation both convex and concave mound shapes were perceived based on the effect of particle size and nozzle diameter. The present outcomes could be useful to validate numerical models and simulation codes of particulate debris sedimentation.

Event sequence assessment of tornado and strong wind in sodium cooled fast reactor based on continuous Markov chain Monte Carlo method with plant dynamics analysis

Takata, Takashi; Azuma, Emiko*

Proceedings of 13th Probabilistic Safety Assessment and Management Conference (PSAM-13) (USB Flash Drive), 10 Pages, 2016/10

A new approach has been developed to assess event sequences under external hazard considering a plant status quantitatively and stochastically so as to take various scenarios into account automatically by applying a Continuous Markov Chain Monte Carlo (CMMC) method coupled with a plant dynamics analysis. In the paper, a tornado and a strong wind are selected as the external hazard to assess the plant safety in a loop type sodium cooled fast reactor (SFR). As a result, it is demonstrated that the various scenarios where the order of the occurrence event and its occurrence time differs from each other can be assessed simultaneously as well as the statistical characteristics of plant parameter such as the coolant temperature. Furthermore, a weight factor is introduced so as to investigate the low failure probability events with a comparative small number of the sampling.

Improvement in quantitative performance of underwater laser-induced breakdown spectroscopy based on the understanding of laser ablation phenomena

Matsumoto, Ayumu

Reza Kako Gakkai-Shi, 23(3), p.222 - 231, 2016/10

no abstracts in English

Asymmetric structure of germanene on an Al(111) surface studied by total-reflection high-energy positron diffraction

Fukaya, Yuki; Matsuda, Iwao*; Feng, B.*; Mochizuki, Izumi*; Hyodo, Toshio*; Shamoto, Shinichi

2D Materials (Internet), 3(3), p.035019_1 - 035019_7, 2016/09

https://doi.org/10.1088/2053-1583/3/3/035019

no abstracts in English

How can interventions for inhabitants be justified after a nuclear accident?; An Approach based on the radiological protection system of the International Commission On Radiological Protection

Takahara, Shogo; Homma, Toshimitsu; Yoneda, Minoru*; Shimada, Yoko*

Hoken Butsuri, 51(3), p.147 - 159, 2016/09

https://doi.org/10.5453/jhps.51.147

no abstracts in English

Report on recent meetings of the young researchers association and the students association of the Japan Health Physics Society

Sakoda, Akihiro; Kataoka, Noriaki*; Ueno, Satoshi*; Matsuyama, Tsugufumi*

Hoken Butsuri, 51(3), p.191 - 195, 2016/09

https://doi.org/10.5453/jhps.51.191

This article briefly overviews two recent meetings (December 2015 and July 2016) of the Young Researchers Association and the Students Association of the Japan Health Physics Society.

The Transfer of radiocesium from the bark to the stemflow of chestnut trees () contaminated by radionuclides from the Fukushima Dai-ichi Nuclear Power Plant accident

Sasaki, Yoshito; Abe, Hironobu; Mitachi, Katsuaki; Watanabe, Takayoshi; Ishii, Yasuo; Niizato, Tadafumi

Journal of Environmental Radioactivity, 161, p.58 - 65, 2016/09

AA2015-0311.pdf:1.93MB

https://doi.org/10.1016/j.jenvrad.2015.12.001

We report the behavior of radiocesium on the tree bark and its transfer into the stemflow of chestnut in a forest in Fukushima. The radiocesium concentration is greatest in 2-cm stem, less in 5-mm stem, and least in the leaves. In the 2-cm stem, the radiocesium concentration of the bark was approximately 10 times that of wood. The average Cs-137 concentration of the dissolved fraction of stem flow was about 10 Bq/L; the pH was nearly constant at 5.8. A strong positive correlation was observed between the radiocesium concentration and the electrical conductivity of the dissolved fraction of stemflow; this result suggests that radiocesium and electrolytes have the same elution mechanism from the tree. Some of the particles in the particulate fraction of the stem flow was strongly adsorbed radiocesium.

Evaluation of neutron nuclear data on xenon isotopes

Rashid, M. M.*; Shigyo, Nobuhiro*; Ishibashi, Kenji*; Iwamoto, Nobuyuki; Iwamoto, Osamu

Journal of Nuclear Science and Technology, 53(9), p.1310 - 1320, 2016/09

https://doi.org/10.1080/00223131.2015.1105164

The neutron cross sections for stable Xe isotopes were calculated by nuclear reaction model code, CCONE and then compared with experimental information. The evaluation was made in the energy region from 1 keV to 20 MeV. The coupled-channels optical model was used to calculate the total cross section. The contributions of preequilibrium and direct processes in the statistical model calculations were considered to obtain reaction cross sections, -ray and particle emission spectra. The present evaluation can reasonably explain the experimental data of total, capture, (), () and () reactions. The obtained capture cross sections for Xe are smaller than the data of JENDL-3.2 in the energy region where the neutron spectrum of YAYOI has a large contribution. Hence, these results could improve the overestimation of C/E values found by the YAYOI experiment. The evaluated total () reaction cross section of Xe is in good agreement with experimental data. Therefore, the present data of Xe could provide relevant ones for KamLAND-Zen and EXO experiments.

Heat conduction analyses on rewetting front propagation during transients beyond anticipated operational occurrences for BWRs

Yonomoto, Taisuke; Shibamoto, Yasuteru; Satou, Akira; Okagaki, Yuria

Journal of Nuclear Science and Technology, 53(9), p.1342 - 1352, 2016/09

AA2015-0497.pdf:1.05MB

https://doi.org/10.1080/00223131.2015.1108882

Our previous study investigated the rewetting behavior of dryout fuel surface during transients beyond anticipated operational occurrences (AOOs) for BWRs, which indicated the rewetting velocity was significantly affected by the precursory cooling defined as cooling immediately before rewetting. The present study further investigated the previous experiments by conducting additional experimental and numerical heat conduction analyses to characterize the precursory cooling. For the characterization, the precursory cooling was firstly defined quantitatively based on evaluated heat transfer rates; the rewetting velocity was investigated as a function of the cladding temperature immediately before the onset of the precursory cooling. The results indicated that the propagation velocity appeared to be limited by the maximum heat transfer rate near the rewetting front. This limitation was consistent with results of the heat conduction analysis.

An Experimental study on natural circulation decay heat removal system for a loop type fast reactor

Ono, Ayako; Kamide, Hideki; Kobayashi, Jun; Doda, Norihiro; Watanabe, Osamu*

Journal of Nuclear Science and Technology, 53(9), p.1385 - 1396, 2016/09

https://doi.org/10.1080/00223131.2015.1121844

Decay heat removal by natural circulation is a significant passive safety measure of a fast reactor against station blackout. The decay heat removal system (DHRS) of the loop type sodium fast reactor being designed in Japan comprises a direct reactor auxiliary cooling system and primary reactor auxiliary cooling system (PRACS). The thermal hydraulic phenomena in the plant under natural circulation conditions need to be understood for establishing a reliable natural circulation driven DHRS. In this study, sodium experiments were conducted using a plant dynamic test loop to understand the thermal-hydraulic phenomena considering natural circulation in the plant. The experiments simulating the scram transient confirmed that PRACS started up smoothly under natural circulation, and the simulated core was stably cooled after the scram. Moreover, the experiments varying the pressure loss coefficients of the loop as the experimental parameters showed robustness of the PRACS.

Electronic structure of hydrogen donors in semiconductors and insulators probed by muon spin rotation

Shimomura, Koichiro*; Ito, Takashi

Journal of the Physical Society of Japan, 85(9), p.091013_1 - 091013_5, 2016/09

https://doi.org/10.7566/JPSJ.85.091013

Local structural analysis of half-metallic ferromagnet CrO

Kodama, Katsuaki; Ikeda, Kazutaka*; Isobe, Masahiko*; Takeda, Hikaru*; Ito, Masayuki*; Ueda, Yutaka*; Shamoto, Shinichi; Otomo, Toshiya*

Journal of the Physical Society of Japan, 85(9), p.094709_1 - 094709_5, 2016/09

https://doi.org/10.7566/JPSJ.85.094709

Atomic scale simulations of relationship between macroscopic mechanical properties and microscopic defect evolution in ultrafine-grained metals

Tsuru, Tomohito; Aoyagi, Yoshiteru*; Shimokawa, Tomotsugu*

Materials Transactions, 57(9), p.1476 - 1481, 2016/09

https://doi.org/10.2320/matertrans.MH201515

The effects of grain size and intragranular dislocation on yield mechanism and subsequent plastic deformation in ultrafine-grained (UFG) Al and Cu were investigated by large-scale atomic simulations. Polycrystalline atomic models with and without intragranular dislocation sources were used to elucidate the relationship between mechanical properties and defect texture. It is found that the intragranular dislocation plays a significant role in both incipient yield and grain boundary mediated dislocation nucleation. In addition UFG Cu yields earlier than UFG Al because partial dislocations in Cu are more likely to activate from grain boundaries, where the partial dislocation leaves deformation twin and secondary dislocation tends to move on twin boundary accompanied by the shift of twin boundary plane.

Influence of fluid viscosity on vortex cavitation at a suction pipe inlet

Ezure, Toshiki; Ito, Kei; Kameyama, Yuri*; Kamide, Hideki; Kunugi, Tomoaki*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 15(3), p.151 - 158, 2016/09

https://doi.org/10.3327/taesj.J15.023

no abstracts in English

JAEA's contribution for R&D and human resource development on implementing IAEA safeguards

Naoi, Yosuke; Oda, Tetsuzo; Tomikawa, Hirofumi

Nihon Genshiryoku Gakkai-Shi ATOMO, 58(9), p.536 - 541, 2016/09

Japan has been promoting nuclear energy research and development, and the use of nuclear energy for only peaceful purposes in accordance with Atomic Energy Basic Acts enacted in 1955. In order to ensure limited to their peaceful utilization, it has been performing a nuclear material accountancy and reporting it based on bilateral nuclear agreement (Japan and the United States, Japan and France, Japan and Canada and so on) before concluding the comprehensive safeguards agreement with the IAEA. After the conclusion of that in 1977, the Japanese national law had been revised. The nuclear material accountancy and its reports to the IAEA have been implemented based on the revised law. In 1999, Japan ratified the additional protocol. Then it has been responding a new obligation in the additional protocol. The correctness and completeness of the declaration of nuclear activities in Japan have been verified by the IAEA, and then the "broader conclusion" was given to Japan in 2004. There indicates no diversion or undeclared nuclear activities in Japan. Since then Japan has been obtaining the "broader conclusion" every year. In this report we will report the JAEA's contribution to the IAEA safeguards on technical research and development and human resource development.

GTHTR300 cost reduction through design upgrade and cogeneration

Yan, X.; Sato, Hiroyuki; Kamiji, Yu; Imai, Yoshiyuki; Terada, Atsuhiko; Tachibana, Yukio; Kunitomi, Kazuhiko

Nuclear Engineering and Design, 306, p.215 - 220, 2016/09

https://doi.org/10.1016/j.nucengdes.2016.02.023

The latest design upgrade has incorporated several major technological advances made in the past ten years to both reactor and balance of plant in GTHTR300. As described in this paper, these advances have enabled raising the design basis reactor core outlet temperature to 950C and increasing power generating efficiency by nearly 5% point. Further implementation of seawater desalination cogeneration is made through employing a newly-proposed multi-stage flash process. Through efficient waste heat recovery of the reactor gas turbine power conversion cycle, a large cost credit is obtained against the conventionally produced water prices. Together, the design upgrade and the cogeneration are shown to reduce the GTHTR300 cost of electricity to under 2.7 cent/kW h.

Spin excitations in optimally P-doped BaFe(AsP) superconductor

Hu, D.*; Yin, Z.*; Zhang, W.*; Ewings, R. A.*; Ikeuchi, Kazuhiko*; Nakamura, Mitsutaka; Roessli, B.*; Wei, Y.*; Zhao, L.*; Chen, G.*; et al.

Physical Review B, 94(9), p.094504_1 - 094504_7, 2016/09

AA2016-0252.pdf:2.18MB

https://doi.org/10.1103/PhysRevB.94.094504

The temperature and energy dependence of spin excitations in an optimally P-doped BaFe(AsP) superconductor (T = 30 K) were studied by using inelastic neutron scattering. Experimental results are consistent with calculations from a combined density functional theory and dynamical mean field theory, and suggest that the decreased average pnictogen height in BaFe(AsP) reduces the strength of electron correlations and increases the effective bandwidth of magnetic excitation.

Electrical conductivity through a single atomic step measured with the proximity-induced superconducting pair correlation

Kim, H.*; Lin, S.-Z.*; Graf, M.*; Miyata, Yoshinori*; Nagai, Yuki; Kato, Takeo*; Hasegawa, Yukio*

Physical Review Letters, 117(11), p.116802_1 - 116802_5, 2016/09

https://doi.org/10.1103/PhysRevLett.117.116802

no abstracts in English

Irradiation experiments of simulated wastes of carbonate slurry

Nagaishi, Ryuji; Motooka, Takafumi; Yamagishi, Isao

Proceedings of 2016 EFCOG Nuclear & Facility Safety Workshop (Internet), 6 Pages, 2016/09

BB2016-0884.pdf:1.24MB

Overflow of water from waste storage tanks of High Integrity Containers (HIC) in the multi-nuclide removal equipment (ALPS) was discovered at Fukushima Daiichi NPS in April of last year. The mechanism of overflow was not understood very much at that time. To elucidate that for chemical safety in the waste storage, irradiation experiments of simulated carbonate slurry by Co-60 -rays have been conducted in CLADS, JAEA in cooperation with TEPCO, TOSHIBA and KURITA. Hydrogen molecule was the main radiolytic gas product in the slurry, and its amount was enhanced by dissolved species of not only halide ions as seawater components but also carbonate ion as an additive for co-precipitation at a basic condition. The bubbles of molecules were further formed and almost held in the slurry without stirred. These sequentially led to the expansion of slurry, and then to its separation into the shrunk one and supernatant water, which was little accumulated without irradiated.

Establishment of technical basis to implement accident tolerant fuels and components to existing LWRs

Yamashita, Shinichiro; Nagase, Fumihisa; Kurata, Masaki; Kaji, Yoshiyuki

Proceedings of Annual Topical Meeting on LWR Fuels with Enhanced Safety and Performance (TopFuel 2016) (USB Flash Drive), p.21 - 30, 2016/09

Fuel rod, channel box, and control rod designed with new materials and concepts have been developed in Japan for increasing accident tolerance of LWRs. In order to efficiently and properly implement the accident tolerant fuels (ATFs) and the other components, it is necessary not only to accumulate fundamental and practical data but also to consider technology readiness, recognize knowledge gaps, and establish strategy for design and fabrication. The Japan Atomic Energy Agency (JAEA) has established the above "technical basis" and drafted a research plan towards implementation of the ATFs and components as a program sponsored and organized by the Ministry of Economy, Trade and Industry (METI). It is useful to take advantage of the experiences in commercial uses of zirconium-base alloys in LWRs and, therefore, JAEA has conducted this METI project in cooperation with power plant providers, fuel venders, research institutes and universities who have been involved in the development of the ATF materials. The present paper describes the main results of the project conducted to establish the technical basis of the ATFs and components.

Development of unstructured mesh-based numerical method for sodium-water reaction phenomenon in steam generators of sodium-cooled fast reactors

Uchibori, Akihiro; Watanabe, Akira*; Takata, Takashi; Ohno, Shuji; Ohshima, Hiroyuki

Proceedings of OECD/NEA & IAEA Workshop on Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation (CFD4NRS-6) (Internet), 11 Pages, 2016/09

For assessment of the wastage environment under tube failure accident in a steam generator of sodium-cooled fast reactors, a mechanistic computer code called SERAPHIM calculating compressible multicomponent multiphase flow with sodium-water chemical reaction has been developed. The original SERAPHIM code is based on the finite difference method. In this study, unstructured mesh-based numerical method was developed and introduced into the SERAPHIM code to advance a numerical accuracy for the complex-shaped domain including multiple heat transfer tubes. Validity of the unstructured mesh-based SERAPHIM code was investigated through the analysis of an under expanded jet experiment. The calculated pressure profile showed good agreement with the experimental data. Numerical analysis of water vapor discharging into liquid sodium was also performed. It was demonstrated that the proposed numerical method could be applicable to evaluation of the sodium-water reaction phenomenon.

Prediction of the effects of boron release kinetics on the vapor species of cesium and iodine fission products

Miwa, Shuhei; Yamashita, Shinichiro; Osaka, Masahiko

Progress in Nuclear Energy, 92, p.254 - 259, 2016/09

https://doi.org/10.1016/j.pnucene.2016.02.023

Cesium (Cs) and iodine (I) vapor species formed just after release from degraded fuels were predicted by means of the chemical equilibrium calculation with focuses on the effects of boron (B) release kinetics. Modified equations for the release kinetics of Cs, I and molybdenum (Mo) were utilized for evaluation of atmospheric dependences of their releases fractions. The release kinetics of B was evaluated considering the formation of iron (Fe)-B-O-H compounds. The release of B was enhanced above approximately 2250 K with the vapor species of CsBO under steam atmosphere, while the formation of CsBO was limited under steam-starvation atmosphere due to the much lower the release of B by the formation of low volatile Fe-B compounds. This limitation of CsBO formation would have resulted in a lesser formation of gaseous hydrogen iodine, HI, and a high volatile atomic I under steam-starvation atmosphere.

Comparison of C collected by precipitation and gas-strip methods for dating groundwater

Nakata, Kotaro*; Hasegawa, Takuma*; Iwatsuki, Teruki; Kato, Toshihiro

Radiocarbon, 58(3), p.491 - 503, 2016/09

AA2015-0781.pdf:0.96MB

https://doi.org/10.1017/RDC.2016.22

Dissolved inorganic carbon (DIC) for C analysis of groundwater is usually extracted by a gas-strip or precipitation method. In this study, the certainty of the two methods for C dating were confirmed. DIC and C concentrations obtained by the gas-strip method were close to the theoretically predicted C value. Conversely, the C value obtained by the precipitation method always showed higher values than the predicted values. The difference in C value between gas-strip and precipitation methods was assumed to arise owing to contamination of modern carbon used in the precipitation method. The applicability of the precipitation method for groundwater should be considered carefully according to the DIC, C concentration of groundwater and purpose of the study being conducted.

Evaluation of world population-weighted effective dose due to cosmic ray exposure

Sato, Tatsuhiko

Scientific Reports (Internet), 6, p.33932_1 - 33932_7, 2016/09

https://doi.org/10.1038/srep33932

After the release of the 2000 Report of the United Nations Scientific Committee of the Effects of Atomic Radiation (UNSCEAR2000), it became commonly accepted that the world population-weighted effective dose due to cosmic-ray exposure is 0.38 mSv. This conclusion was maintained in a recent version of UNSCEAR Report, UNSCEAR2008. However, these values were derived from approximate projections of altitude and geographic dependences of the cosmic-ray dose rates as well as world population. This present study hence re-evaluated the population-weighted annual effective doses and their probability densities for the entire world as well as for 230 individual nations, using a more sophisticated cosmic-ray flux calculation model in tandem with detailed grid population and elevation databases. The resulting world population-weighted annual effective dose was determined to be 0.32 mSv, which is smaller than the UNSCEAR's evaluation by 16%. These data improve our understanding of cosmic-ray radiation exposures to populations globally.

Optically transparent ferromagnetic nanogranular films with tunable transmittance

Kobayashi, Nobukiyo*; Masumoto, Hiroshi*; Takahashi, Saburo*; Maekawa, Sadamichi

Scientific Reports (Internet), 6, p.34227_1 - 34227_7, 2016/09

https://doi.org/10.1038/srep34227

Evaluation of internal stress in short-carbon-fiber reinforced plastics by transmission X-ray diffraction

Shimizu, Kenichi*; Koike, Yuki*; Yamada, Taiki*; Oharada, Kazuya*; Tanaka, Keisuke*; Shobu, Takahisa

Zairyo, 65(9), p.657 - 664, 2016/09

https://doi.org/10.2472/jsms.65.657

The internal stress in crystalline thermoplastics, polyphenylene sulphide (PPS), reinforced by carbon fibers of 30 mass% was measured by the diffraction method using synchrotron with energy of 12.3 keV. The stress in the matrix was determined by the sin2psi method with side-inclination optics of transmitted X-ray diffractions. Using skin-layer strips cut parallel, perpendicular and 45 degree to the molding direction of the injection molded plates, the matrix stress was measured under the uniaxial applied stress. The experimental values were at least qualitatively agreed with the prediction derived based on micromechanics. The quantitative difference between experiment and prediction is mainly due to the neglect of the distribution of fiber orientations in the micromechanics prediction. These residual stresses were caused by the mismatch of the thermal expansion coefficient between matrix and fibers.

Shielding technology for upper structure of HTTR

Ueta, Shohei; Sakaba, Nariaki; Sawa, Kazuhiro

Annals of Nuclear Energy, 94, p.72 - 79, 2016/08

https://doi.org/10.1016/j.anucene.2016.02.021

In the shielding design for the High Temperature Gas-cooled Reactor (HTGR), special attentions shall be needed to avoid neutron streaming, since helium gas as a coolant does not work for shielding. Japan Atomic Energy Agency has demonstrated the performance of shielding through testing operations of the High Temperature Engineering Test Reactor (HTTR) in order to establish design method for shielding of the Very-High-Temperature Reactor (VHTR) as a Generation-IV nuclear power system. As results of the test, it was confirmed that dose equivalent rates for neutron and -ray at on-operating acceptable areas were less than detection limit and as low as background, respectively. The measured dose at the stand-pipe room corresponded to the detection limit, and it was found that over 90% of dose derived from fast neutron. It was indicated that there was still a margin of factor 50 in addition to the design which excluded the safety factor. The measured dose rates showed good agreement with the predicted considering the control rod withdrawing effect. The knowledge on the design method and the demonstration of shielding by the HTTR will strongly contribute to realizing and optimizing the designs of future VHTRs.

Microscopic features of quartz and clay particles from fault gouges and infilled fractures in granite; Discriminating between active and inactive faulting

Niwa, Masakazu; Shimada, Koji; Aoki, Kazuhiro; Ishimaru, Tsuneari

Engineering Geology, 210, p.180 - 196, 2016/08

https://doi.org/10.1016/j.enggeo.2016.06.013

This study focused on microscopic features using particle size analysis, SEM and TEM and identified mineralogical and textural characteristics to improve our ability to discriminate between the active and inactive gouges. Particle size distribution analysis largely shows that fault gouge in an active fault, having the most abundant finer particles, experienced repetitive shearing whereas the inactive gouges did not. SEM examination of quartz particles shows that more particles retain their primary crystal structure in the active gouge than in the inactive gouges. In contrast, observation of very fine clay minerals using TEM shows the minerals in the active gouge are abraded and corroded in equal or higher degree as the aseismic gouges. Repetitive fault activities could result in the addition of new quartz particles from the granite with preservation of primary crystal structure, whereas relatively-soft clay minerals had been affected by abrasion and dissolution.

Recent progress of the energy-resolved neutron imaging system at J-PARC

Kai, Tetsuya; Shinohara, Takenao

Isotope News, (746), p.20 - 24, 2016/08

http://www.jrias.or.jp/books/pdf/201608_TENBO_KAI_SHINOHARA.pdf

no abstracts in English

Silver photo-diffusion and photo-induced macroscopic surface deformation of GeS/Ag/Si substrate

Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kondo, Keietsu; Yamazaki, Dai; Soyama, Kazuhiko; Ailavajhala, M.*; Mitkova, M.*

Journal of Applied Physics, 120(5), p.055103_1 - 055103_10, 2016/08

https://doi.org/10.1063/1.4959207

Analysis of fuel subassembly innerduct configurational effects on the core characteristics and power distribution of a sodium-cooled fast breeder reactor

Ohgama, Kazuya; Nakano, Yoshihiro; Oki, Shigeo

Journal of Nuclear Science and Technology, 53(8), p.1155 - 1163, 2016/08

https://doi.org/10.1080/00223131.2015.1096849

The power distribution and core characteristics in various configurations of fuel subassemblies with an innerduct structure in the Japan Sodium-cooled Fast Reactor were evaluated using a Monte Carlo code for neutron transport and burnup calculation. The correlation between the fraction of fuel subassemblies facing outward and the degree of power increase at the core center was observed regardless of the compositions. This indicated that the spatial fissile distribution caused by innerduct configurations was the major factor of the difference in the power distribution. A power increase was also found in an off-center region, and it tended to be greater than that at the core center because of the steep gradient of neutron flux intensity. The differences in the worth of control rods caused by innerduct configurations were confirmed.

Small-angle neutron scattering study of specific interaction and coordination structure formed by mono-acetyl-substituted dibenzo-20-crown-6-ether and cesium ions

Motokawa, Ryuhei; Kobayashi, Toru; Endo, Hitoshi*; Ikeda, Takashi; Yaita, Tsuyoshi; Suzuki, Shinichi; Narita, Hirokazu*; Akutsu, Kazuhiro*; Heller, W. T.*

Journal of Nuclear Science and Technology, 53(8), p.1205 - 1211, 2016/08

https://doi.org/10.1080/00223131.2015.1102100

Studies on electrochemical behavior of uranium species in choline chloride-urea eutectic for developing electrolytically treating method of uranium-bearing wastes

Ohashi, Yusuke; Asanuma, Noriko*; Harada, Masayuki*; Tanaka, Yoshio; Ikeda, Yasuhisa*

Journal of Radioanalytical and Nuclear Chemistry, 309(2), p.627 - 636, 2016/08

https://doi.org/10.1007/s10967-015-4625-0

As one of methods for recovering uranium from the uranium-bearing wastes, we have proposed the electrolytic deposition method using choline chloride-urea (CCU) which is known as an ambient temperature molten salt. More than 92% of uranium components in inactivated alumina and spent sodium fluoride adsorbent was dissolved into CCU solution. Cyclic voltammograms (CVs) of the solutions prepared by dissolving uranium-bearing wastes in CCU were measured in the potential range of -2.0 to 1.1 V (vs. Ag/AgCl). The one reduction peak was observed around -0.7 V for all solutions. Based on the results of CVs, bulk electrolyses of the solutions dissolving uranium-bearing wastes were also carried out at -1.5V at 80 C. The deposits were formed on a carbon electrode as cathode. Consequently, we confirmed that CCU is effective media for recovering uranium selectively from uranium-bearing waste.

The Role of bedding in the evolution of meso- and microstructural fabrics in fault zones

Ishii, Eiichi

Journal of Structural Geology, 89, p.130 - 143, 2016/08

https://doi.org/10.1016/j.jsg.2016.05.007

To investigate the role of bedding in the evolution of meso- and microstructural fabrics in fault zones, detailed microscopic, mineralogical, and geochemical analyses were conducted on bedding-oblique and bedding-parallel faults that cut a folded Neogene siliceous mudstone that contains opal-CT, smectite, and illite. An analysis of asymmetric structures in the fault gouges indicates that the secondary fractures associated with each fault exhibit contrasting characteristics: those of the bedding-oblique fault are R1 shears, whereas those of the bedding-parallel fault are reactivated S foliation. The bedding-oblique fault shows the pervasive development of S foliation, lacks opal-CT, and has low SiO/TiO ratios only in gouge, whereas the bedding-parallel fault exhibits these characteristics in both gouge and wall rocks. The development of S foliation and the lack of silica can result from local ductile deformation involving the sliding of phyllosilicates, coupled with pressure solution of opal-CT. Although such deformation can occur in gouge, the above results indicate that it may occur preferentially along bedding planes, preceding the formation of a gouge/slip surface. Thus, in sedimentary rocks that contain phyllosilicates and soluble minerals, bedding can influence the rheological evolution of meso- and microstructural fabrics in fault zones.

Neutron irradiation effect of high-density MoO pellets for Mo-99 production, 3

Ishida, Takuya; Suzuki, Yoshitaka; Nishikata, Kaori; Yonekawa, Minoru; Kato, Yoshiaki; Shibata, Akira; Kimura, Akihiro; Matsui, Yoshinori; Tsuchiya, Kunihiko; Sano, Tadafumi*; et al.

KURRI Progress Report 2015, P. 64, 2016/08

http://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2015/PR2015.pdf#page=73

no abstracts in English

Measurements of americium isotopes by activation method at KURRI-Linac

Nakamura, Shoji; Terada, Kazushi; Takahashi, Yoshiyuki*; Sano, Tadafumi*; Hori, Junichi*

KURRI Progress Report 2015, P. 69, 2016/08

http://www.rri.kyoto-u.ac.jp/PUB/report/PR/ProgRep2015/PR2015.pdf#page=78

Neutron capture cross section measurements has been conducted for Minor Actinides (MAs) under the research project entitled by "Research and development for Accuracy Improvement of neutron nuclear data on Minor ACtinides (AIMAC)". The present work selected two americium isotopes, Am and Am, were selected, and measurements were carried out by an activation method with neutron sources at KURRI-Linac. It was found that the neutron flux at the target positon was of the order of 10 (n/cms). The reaction rates of Am and Am were obtained by - and -ray measurements of the irradiated Am samples.

Photonic crystals fabricated by block copolymerization-induced microphase separation

Motokawa, Ryuhei; Taniguchi, Tatsuo*; Kumada, Takayuki; Iida, You*; Aoyagi, Shota*; Sasaki, Yusuke*; Kori, Michinari*; Kishikawa, Keiki*

Macromolecules, 49(16), p.6041 - 6049, 2016/08

https://doi.org/10.1021/acs.macromol.6b01190

Benchmark analyses of probabilistic fracture mechanics for cast stainless steel pipe

Hojo, Kiminobu*; Hayashi, Shotaro*; Nishi, Wataru*; Kamaya, Masayuki*; Katsuyama, Jinya; Masaki, Koichi*; Nagai, Masaki*; Okamoto, Toshiki*; Takada, Yasukazu*; Yoshimura, Shinobu*

Mechanical Engineering Journal (Internet), 3(4), p.16-00083_1 - 16-00083_16, 2016/08

https://doi.org/10.1299/mej.16-00083

Performance demonstration certification of non-destructive inspection for cast stainless steel (CASS) has been planned but the target flaw depth to be detected has not been determined yet in Japan. The target flaw size is closely connected to the allowable flaw size which is determined by flaw evaluation of the rules on fitness-for-service. For rational mitigation of the acceptable flaw size, application of probabilistic fracture mechanics (PFM) is one of the useful countermeasures compared with deterministic approach. In this paper, benchmark problems for a CASS pipe were proposed with intention applying and verifying PFM codes. As the fracture modes, fatigue crack extension, plastic collapse and ductile crack initiation were assumed. Six organizations participated in the benchmark analysis and failure probabilities from them were compared. As a result the failure probability of each problem showed good agreement and the code for application of CASS issue has been verified.

Surface analyses of cesium hydroxide chemisorbed onto type 304 stainless steel

Di Lemma, F. G.; Nakajima, Kunihisa; Yamashita, Shinichiro; Osaka, Masahiko

Nuclear Engineering and Design, 305, p.411 - 420, 2016/08

https://doi.org/10.1016/j.nucengdes.2016.06.023

Chemisorption is of main importance during a Severe Accident (SA) at a light water reactor, as it can influence fission products retention in the reactor vessel. Information on the distribution, composition and properties of such deposits can influence the decommissioning practice after a SA. Moreover such information can enhance the description of the chemisorption models applied in SA codes, consequently improving the source term assessment. This paper will present the results obtained from CsOH chemisorption experiments onto type 304 stainless steel samples, used as simulants of reactor structural materials. The samples post-analyses showed that CsOH will absorb onto the surface, reacting preferentially with Si impurities and forming a newly detected compound, CsFeSiO. From our results, it can be inferred that Si content in structural materials can determine the amount of radioactive Cs deposited onto the reactor vessel after a SA.

Analytical model for estimating the zenith angle dependence of terrestrial cosmic ray fluxes

Sato, Tatsuhiko

PLOS ONE (Internet), 11(8), p.e0160390_1 - e0160390_22, 2016/08

https://doi.org/10.1371/journal.pone.0160390

A new model called PARMA4.0 was developed to facilitate instantaneous estimation of not only omnidirectional but also angular differential fluxes of cosmic rays anywhere in Earth's atmosphere at nearly any given time. It consists of its previous version, PARMA3.0, for calculating the omnidirectional fluxes and several mathematical functions proposed in this study for expressing their zenith-angle dependences. The numerical values of the parameters used in these functions were fitted to reproduce the results of the extensive air shower simulation performed by Particle and Heavy Ion Transport code System (PHITS). The accuracy of PARMA4.0 was closely verified using multiple sets of experimental data obtained under various global conditions. This extension enlarges the model's applicability to more areas of research, including design of cosmic-ray detectors, muon radiography, soil moisture monitoring, and cosmic-ray shielding calculation.

Manifestation of chirality in the vortex lattice in a two-dimensional topological superconductor

Smith, E. D. B.*; Tanaka, Kaori*; Nagai, Yuki

Physical Review B, 94(6), p.064515_1 - 064515_13, 2016/08

https://doi.org/10.1103/PhysRevB.94.064515

no abstracts in English

Asymmetry dependence of reduction factors from single-nucleon knockout of Ne at 230 MeV/nucleon

Lee, J.*; Liu, H.*; Doornenbal, P.*; Kimura, Masaaki*; Minomo, Kosho*; Ogata, Kazuyuki*; Utsuno, Yutaka; Aoi, Nori*; Li, K.*; Matsushita, Masafumi*; et al.

Progress of Theoretical and Experimental Physics (Internet), 2016(8), p.083D01_1 - 083D01_7, 2016/08

AA2016-0230.pdf:0.16MB

https://doi.org/10.1093/ptep/ptw096

no abstracts in English

Utilization of Cs/Cs in the environment to identify the reactor units that caused atmospheric releases during the Fukushima Daiichi accident

Chino, Masamichi; Terada, Hiroaki; Nagai, Haruyasu; Katata, Genki; Mikami, Satoshi; Torii, Tatsuo; Saito, Kimiaki; Nishizawa, Yukiyasu

Scientific Reports (Internet), 6, p.31376_1 - 31376_14, 2016/08

https://doi.org/10.1038/srep31376

Ice VII from aqueous salt solutions; From a glass to a crystal with broken H-bonds

Klotz, S.*; Komatsu, Kazuki*; Pietrucci, F.*; Kagi, Hiroyuki*; Ludl, A.-A.*; Machida, Shinichi*; Hattori, Takanori; Sano, Asami; Bove, L. E.*

Scientific Reports (Internet), 6, p.32040_1 - 32040_8, 2016/08

https://doi.org/10.1038/srep32040

It has been known since decades that certain aqueous salt solutions of LiCl and LiBr readily form glasses when cooled to below 160 K. This fact has recently been exploited to produce a salty high pressure ice form: When the glass is compressed at low temperatures to pressures higher than 4 GPa and subsequently warmed, it crystallizes into ice VII with the ionic species trapped inside the ice lattice. Here we report the extreme limit of salt incorporation into ice VII, using high pressure neutron diffraction and molecular dynamics simulations. We show that high-pressure crystallization of aqueous solutions of LiCl5.6HO and LiBr5.6HO leads to solids with strongly expanded volume, a destruction of the hydrogen-bond network with an isotropic distribution of water-dipole moments, as well as a crystal to-amorphous transition on decompression. This highly unusual behavior constitutes an interesting pathway from a glass to a crystal where translational periodicity is restored but the rotational degree of freedoms remaining completely random.

Spacing between graphene and metal substrates studied with total-reflection high-energy positron diffraction

Fukaya, Yuki; Entani, Shiro; Sakai, Seiji; Mochizuki, Izumi*; Wada, Ken*; Hyodo, Toshio*; Shamoto, Shinichi

Carbon, 103, p.1 - 4, 2016/07

https://doi.org/10.1016/j.carbon.2016.03.006

no abstracts in English

Current status of Neutron Sciences at Research Reactor JRR-3

Takeda, Masayasu

Hozengaku, 15(2), p.31 - 34, 2016/07

no abstracts in English

Evaluation of neutron nuclear data on tantalum isotopes

Shibata, Keiichi

Journal of Nuclear Science and Technology, 53(7), p.957 - 967, 2016/07

AA2015-0199.pdf:0.39MB

https://doi.org/10.1080/00223131.2015.1083492

Neutron nuclear data on Ta have been evaluated for the next version of Japanese Evaluated Nuclear Data Library general-purpose file in the energy region from eV to 20 MeV. Resolved resonance parameters were selected from experimental data, while unresolved ones were obtained from nuclear model calculations. A statistical model code CCONE was applied to evaluate cross sections above the resolved resonance region. Compound, pre-equilibrium and direct-reaction processes were considered for cross-section calculation. Coupled-channel optical model parameters were employed for the interaction between neutrons and nuclei. Giant-dipole and pygmy resonance parameters for E1 -ray transition from tantalum isotopes were determined so as to reproduce measured -ray spectrum. The present results reproduce experimental data very well, and are much better than the JENDL-4.0 evaluation. The evaluated data are compiled into ENDF-formatted data files.

Evaluation of the intake of radon through skin from thermal water

Sakoda, Akihiro; Ishimori, Yuu; Tschiersch, J.*

Journal of Radiation Research, 57(4), p.336 - 342, 2016/07

https://doi.org/10.1093/jrr/rrw024

In general, the deposition of inhaled radon progeny on lung gives the largest dose when the dose evaluation is made for the so-called radon exposure. In this case, the dose from inhalation of radon itself is much lower than that from its progeny. Also, very little studies of the absorption of radon via skin have not been done so far. However, specific environments such as radon hot springs have the characteristics that radon concentration in water is significantly higher by a few orders than that in air. In the present study, a biokinetic model of radon into which its skin-absorption process was incorporated was developed to discuss the change in radon concentrations in tissues during and after bathing in thermal water. This derived dose was compared with other exposure routes from radon and its progeny.

Multi-band Eilenberger theory of superconductivity; Systematic low-energy projection

Nagai, Yuki; Nakamura, Hiroki

Journal of the Physical Society of Japan, 85(7), p.074707_1 - 074707_18, 2016/07

https://doi.org/10.7566/JPSJ.85.074707

no abstracts in English

Creation of research center related to decommissioning Fukushima Daiichi Nuclear Power Station

Kawamura, Hiroshi; Yamada, Tomonori

Kinzoku, 86(7), p.580 - 589, 2016/07

http://ci.nii.ac.jp/naid/40020893361

no abstracts in English

The Installation and the radiation protection of the optically stimulated luminescence reader with sealed beta source in the Toki Research Institute of Isotope Geology and Geochronology, Japan Atomic Energy Agency

Tokuyasu, Kayoko; Furuta, Sadaaki*; Kokubu, Yoko; Umeda, Koji

Nihon Hoshasen Anzen Kanri Gakkai-Shi, 15(1), p.80 - 87, 2016/07

http://doi.org/10.11269/jjrsm.15.80

An optically stimulated luminescence reader (Riso TL/OSL DA-20) was installed in Toki Research Institute of Isotope Geology and Geochronology (Toki-shi, Gifu Prefecture), Japan Atomic Energy Agency (JAEA) for dating the geological sample. An accumulated dose of the sample is obtained using the reader. Sealed beta source of strontium-90 is required to be mounted on the reader because repeated artificial irradiation is necessary for the accumulated dose estimation. However, there are not many introduction examples for the reader domestically, and the information as to radiation control of the reader is limited. We therefore report here the process of source loading on the reader and radiation control associated with the use of the source.

Gamma irradiation effects of image sensor for radiation-resistant camera

Takeuchi, Tomoaki; Otsuka, Noriaki; Tsuchiya, Kunihiko; Tanaka, Shigeo*; Ozawa, Osamu*; Komanome, Hirohisa*; Watanabe, Takashi*; Ueno, Shunji*

Nihon Hozen Gakkai Dai-13-Kai Gakujutsu Koenkai Yoshishu, p.391 - 394, 2016/07

no abstracts in English

Replacement of the glove box panel in Nuclear Fuel Reprocessing Facility

Masui, Kenji; Yamamoto, Masahiko; Kuno, Takehiko; Surugaya, Naoki

Nihon Hozen Gakkai Dai-13-Kai Gakujutsu Koenkai Yoshishu, p.25 - 30, 2016/07

no abstracts in English

Status of R&D of high-performance monitoring system under sever accident

Tsuchiya, Kunihiko; Takeuchi, Tomoaki; Komanome, Hirohisa*; Miura, Kuniaki*; Araki, Masanori; Ishihara, Masahiro

Nihon Hozen Gakkai Dai-13-Kai Gakujutsu Koenkai Yoshishu, p.375 - 378, 2016/07

no abstracts in English

Processes of silver photodiffusion into Ge-chalcogenide probed by neutron reflectivity technique

Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kawakita, Yukinobu; Ito, Takayoshi*; Kubota, Masato; Yamazaki, Dai; Soyama, Kazuhiko; Sheoran, G.*; Mitkova, M.*

Physica Status Solidi (A), 213(7), p.1894 - 1903, 2016/07

https://doi.org/10.1002/pssa.201533037

no abstracts in English

Theoretical model analysis of reactions on Be and C at incident energies up to 50 MeV

Nakayama, Shinsuke; Kono, Hiroshi*; Watanabe, Yukinobu*; Iwamoto, Osamu; Ogata, Kazuyuki*

Physical Review C, 94(1), p.014618_1 - 014618_9, 2016/07

https://doi.org/10.1103/PhysRevC.94.014618

Double-differential thick target neutron yields (TTNYs) from deuteron bombardment on thick Be and C targets are analyzed using the DEURACS (DEUteron-induced Reaction Analysis Code System). The calculated TTNYs reproduced the experimental ones quantitatively well in the incident energy range up to 50 MeV. In addition, it was found that the proton stripping reaction makes the most dominant contribution to neutron production. From the analysis, we conclude that the DEURACS is applicable to reactions and modeling of the stripping reaction is essential to predict neutron production yields accurately.

Development of seismic isolation systems for sodium-cooled fast reactors in Japan

Kawasaki, Nobuchika; Watakabe, Tomoyoshi; Wakai, Takashi; Yamamoto, Tomohiko; Fukasawa, Tsuyoshi*; Okamura, Shigeki*

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 8 Pages, 2016/07

http://doi.org/10.1115/PVP2016-63437

Sodium-cooled Fast Reactors (SFRs) have components with thinner walls as compared with light water reactors, although Japan is an earthquake-prone country. Thus, seismic isolation systems have been conventionally employed in SFR system design to reduce seismic forces on the systems in Japan. Implementation of seismic design in the reactor core and buckling design in the reactor vessel requires 8 Hz (or less) vertical frequency's isolation system being applied. This paper introduces three isolation concepts to achieve the frequency. The isolation systems, which enable vertical 8 Hz natural frequency, comprise thicker laminated rubber bearings (TRBs). By combining coned disk springs with TRBs, vertical natural frequency is in a range from roughly 3 Hz to 5 Hz. Combining pneumatic springs to RBs and adding the rocking suppression system, vertical natural frequency becomes under 1 Hz. All isolation systems need horizontal damping like oil dampers. A vertical 8 Hz isolation system with TRBs and oil dampers is under development in Japan as a principal isolation concept. The reasons of choosing this system are its simplicity and the number of developing issues. Since TRBs and oil dampers are basic isolation elements, they can be applied to other isolation systems. The response acceleration of 5 Hz vertical isolation is 50% of that of 8 Hz based on the analytical survey. A series of static tests of coned disk springs was carried out to confirm design equations. Based on these knowledge, 5 Hz vertical isolation system with TRBs and the coned disk springs can be designed. The response acceleration of 1 Hz vertical isolation is 10% of that of 8 Hz. A rocking suppression system was studied in the past, and the further simplification of this system is the largest challenge for this concept. These three isolation concepts are isolation candidates for SFRs in Japan. To obtain enough seismic margins for each plant site, these isolation systems need to be developed.

Development on rubber bearings for sodium-cooled fast reactor, 3; Ultimate properties of a half scale thick rubber bearings based on breaking test

Fukasawa, Tsuyoshi*; Okamura, Shigeki*; Yamamoto, Tomohiko; Kawasaki, Nobuchika; Hirotani, Tsutomu*; Moriizumi, Eriko*; Sakurai, Yu*; Masaki, Nobuo*

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 10 Pages, 2016/07

http://doi.org/10.1115/PVP2016-63397

Half-scale thick rubber bearing to investigate ultimate properties application for a Sodium-cooled-Fast-Reactor. The fundamental restoring-force characteristics of the thick rubber bearings has been already cleared through the static loading tests using a half-scale thick rubber bearing, 800 mm in diameter. However, variations of the restoring force characteristics and ultimate properties have not been obtained yet. The purpose of this paper is to indicate the variation of the stiffness and damping ratio concerning restoring force characteristics and the breaking strain or stress as ultimate properties through static loading tests using the half-scale thick rubber bearings.

Bayesian statistical analysis on chemical composition contributing to irradiation embrittlement at high fluence region

Takamizawa, Hisashi; Nishiyama, Yutaka

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 5 Pages, 2016/07

http://doi.org/10.1115/PVP2016-63822

It has been accepted that neutron irradiation embrittlement of reactor pressure vessel is caused by irradiation-induced formation of solute clusters (SCs) and matrix damages (MDs). In the present study, to analyze the contribution of chemical composition contained in SCs to irradiation embrittlement at high fluence region, statistical analysis using the Bayesian nonparametric (BNP) method was performed for Japanese PWR surveillance data. The significance of P, Si and Mn contents, which are not necessarily included in embrittlement correlations unlike the Cu and Ni content, was evaluated. The BNP method can learn the complexity of the statistical model itself from the input data and infer the predicted data with individual probability distribution of predict condition. The result suggested that irradiation embrittlement was most affected by the Si content at high fluence region.

Experimental study on ultimate strength of a ellipsoidal dished head plate under pressure on convex surface

Yada, Hiroki; Ando, Masanori; Tsukimori, Kazuyuki; Ichimiya, Masakazu*; Anoda, Yoshinari*

Proceedings of 2016 ASME Pressure Vessels and Piping Conference (PVP 2016) (Internet), 7 Pages, 2016/07

http://doi.org/10.1115/PVP2016-63147

no abstracts in English

Development of active neutron NDA techniques for nonproliferation and nuclear security, 2; Study on a compact NRTA system

Tsuchiya, Harufumi; Kitatani, Fumito; Maeda, Makoto; Kureta, Masatoshi

Proceedings of INMM 57th Annual Meeting (Internet), 6 Pages, 2016/07

From a viewpoint of nuclear safeguards and nuclear security, it has recently become important to develop a non-destructive assay (NDA) system that accurately determines the amount of special nuclear materials (SNMs) in various samples such as spent fuels, next generation MA-Pu fuels and fuel debris. One candidate of those NDA techniques is neutron resonance transmission analysis (NRTA). It relies on a neutron time-of-flight measurement and is a well-established method to apply for the accurate evaluations of nuclear data, including total cross sections and resonance parameters. The potential of NRTA to quantify SNM in complex materials has been already demonstrated by performing NRTA measurement at IRMM/GELINA under collaboration of JAEA and JRC. However, a present NRTA system usually has a large electron accelerator facility to generate intense neutrons, whereas this is very difficult to apply to various facilities that need to measure SNM. Therefore a compact NRTA system would be required for practical applications of quantifying SNM in a variety of samples. In order to realize a compact NRTA system, we are developing a prototype with a D-T neutron generator that has a pulse width of 10 s and an average maximum neutron yield ranging from n/s to n/s. Numerical calculations were used to optimize the system performance to quantify SNM and MA in spent and MA-Pu fuels. In this presentation, those numerical calculation results, together with a brief description of the prototype, are presented. In addition, we discuss a future prospect of a compact NRTA system equipped with a neutron source with a shorter pulse width (ex. 100 ns) and a more intense neutron yield.

Development of Pu standard material preparation and characterization technique in Japan

Okazaki, Hiro; Shibano, Koya; Abe, Katsuo; Sumi, Mika; Kayano, Masashi; Kageyama, Tomio; Mason, P.*

Proceedings of INMM 57th Annual Meeting (Internet), 7 Pages, 2016/07

The reference materials used for accountancy analysis by IDMS, referred to as LSD spikes allows to obtain accurate measurement results for a variety of nuclear materials under potentially difficult handling or measurement conditions. Because of expected difficulties in a stably long term supply of plutonium reference materials, which are the main source of plutonium for LSD spikes preparation, the JAEA's PFDC decided to evaluate the possibility of using domestically available MOX powders as a plutonium source material for LSD spikes. Therefore, PFDC started to separate, purify and characterize plutonium in MOX powders for plutonium reference materials (MOX-Pu) preparation that are suitable for source of LSD spikes in cooperation with the US DOE's NBL. The detailed preparation procedure of the latest MOX-Pu standard material and results of intercomparison for verification are presented.

Characterization study of four candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station (Interim report)

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Maeda, Makoto; Nauchi, Yasushi*; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; et al.

Proceedings of INMM 57th Annual Meeting (Internet), 10 Pages, 2016/07

Excavation damaged zone inferred by geophysical surveys on drift floor of Horonobe URL

Tokiwa, Tetsuya*; Aoyagi, Kazuhei; Fujita, Tomoo

Rock Mechanics and Rock Engineering; From the Past to the Future (EUROCK 2016), p.901 - 906, 2016/07

What's about "Fukushima Nuclear Accident Archive"

Kumazaki, Yui

Senmon Toshokan, (278), p.40 - 43, 2016/07

AA2016-0112.pdf:1.21MB

no abstracts in English

Non-destructive depth analysis of the surface oxide layer on MgSi with XPS and XAS

Esaka, Fumitaka; Nojima, Takehiro; Udono, Haruhiko*; Magara, Masaaki; Yamamoto, Hiroyuki

Surface and Interface Analysis, 48(7), p.432 - 435, 2016/07

https://doi.org/10.1002/sia.5939

XPS is widely used for non-destructive chemical state analysis of solid materials. In this method, depth profiling can be carried out by a combination with ion beam sputtering. However, the sputtering often causes segregation and preferential sputtering of atoms and gives inaccurate information. The use of energy-tunable X-rays from synchrotron radiation (SR) enables us to perform non-destructive depth profiling in XPS. Here, the analytical depth can be changed by changing excitation X-ray energy. In the present study, we examined methods to perform depth profiling with XPS by changing excitation energy and XAS by changing electron energy for detection. These methods were then applied to the analysis of native surface oxide layers on MgSi crystals. In this XAS analysis, the peak at 1843.4 eV becomes dominant when the electron energy for detection increases, which implies that Si-O or Si-O-Mg structure is formed as the surface oxide layer on the MgSi.

Importance of temperature control in surrounding environment during permeability test for measuring hydraulic constants of rock

Kato, Masaji*; Nara, Yoshitaka*; Fukuda, Daisuke*; Kono, Masanori*; Sato, Toshinori; Sato, Tsutomu*; Takahashi, Manabu*

Zairyo, 65(7), p.489 - 495, 2016/07

https://doi.org/10.2472/jsms.65.489

Rock masses serve a vital function as natural barriers for geological disposal of radioactive waste; therefore, information on rock permeability is essential. Highly accurate measurement of permeability requires understanding of how temperature changes in the surrounding environment influence measurement results. We performed permeability measurement under conditions with dramatic changes of temperature in the surrounding environment to investigate the influence of such changes on the experimental results. Measurement of permeability with no temperature change was also conducted as reference. All measurements were conducted using the transient pulse method, and the sample material used was Toki granite obtained from Gifu Prefecture in central Japan. We found that temperature changes in the surrounding environment remarkably affected the pressure in reservoirs upstream and downstream, the pressure difference between them, and the confining pressure; all increased when temperature increased for our experimental system. Notably, pressure difference was affected immediately. This difference directly relates to estimation of permeability.

Diffusion model considering multiple pore structures in compacted bentonite

Yotsuji, Kenji; Tachi, Yukio; Okubo, Takahiro*

CMS Workshop Lectures, Vol.21, p.251 - 257, 2016/06

https://www.clays.org/other-cms-publications-wrksh21/

We have developed integrated sorption and diffusion model (ISD model) for assessment of diffusion parameters consistent with sorption processes in compacted bentonite. The ISD model gives consistent consideration to porewater chemistry, sorption and diffusion processes in compacted bentonite. The diffusion component based on the electric double layer theory and the homogeneous pore model in the ISD model accounts consistently for cation De overestimation and anion exclusion in narrow pores. The current ISD model can quantitatively account for diffusion of monovalent cations and anions, however, the model predictions disagree with diffusion data for multivalent cation and complex species. To improve the applicability of the model, it is necessary to consider the atomic level interactions between solute, solvent or clay mineral, and try that we apply the current ISD model to heterogeneous pore structure. In this study we try the application of the current ISD model to multiple pore structure. As results of numerical analysis of these models, the salinity dependence of effective diffusivity for the multi-pore model is comparatively smaller than that for the homogeneous pore model and the current diffusion model is improved.