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Journal Articles

Estimation of hydrogen gas production at transient criticality in uranyl nitrate solution

Yoshida, Ryoichiro; Yamane, Yuichi; Abe, Hitoshi

Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.408 - 414, 2019/09

In a criticality accident, it is known that some kinds of radiolysis gases are generated mainly due to kinetic energy of fission fragments. Hydrogen gas (H$$_{2}$$) is one of them, which is able to initiate explosion. The rate of H$$_{2}$$ generation and its total amount can be estimated from the number of fission per second if its G value is known. In this study, it was tried to estimate G value of hydrogen gas (G(H$$_{2}$$)) by using the H$$_{2}$$ concentration measured as time-series data in Transient Experiment Critical Facility (TRACY) which was carried out by Japan Atomic Energy Agency. There was time lag in the measured H$$_{2}$$ concentration from its generation. To overcome those problems, measured profile of H$$_{2}$$ concentration was reproduced based on a hypothetical model and its total amount was evaluated. Based on the model, the obtained G(H$$_{2}$$) was 1.2.

Journal Articles

Characterization of phosphate cement irradiated by $$gamma$$-ray during dehydration

Irisawa, Keita; Kudo, Isamu*; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Nakazawa, Osamu

QST-M-8; QST Takasaki Annual Report 2016, P. 63, 2018/03

A solidification technique with minimized water content is being developed using a phosphate cement for safe storage of secondary radioactive wastes in the Fukushima Daiichi Nuclear Power Plant. To understand the applicability of the solidification technique for the actual secondary wastes, phosphate cement during dehydration was irradiated by $$^{60}$$Co $$gamma$$-ray. The G(H$$_{2}$$) for the phosphate cement decreased with time during dehydration, and was not detected after 7 days. Moreover, the $$^{60}$$Co $$gamma$$-ray irradiation during dehydration did not change the crystalline and amorphous phases of the phosphate cement.

JAEA Reports

Application of probability generating function to the essentials of nondestructive nuclear materials assay system using neutron correlation

Hosoma, Takashi

JAEA-Research 2016-019, 53 Pages, 2017/01

JAEA-Research-2016-019.pdf:5.71MB

Application of probability generating function for nondestructive nuclear materials assay system was studied. First, high-order neutron correlations were derived algebraically up to septuplet and basic characteristics of the correlations were investigated. It was found that higher-order correlation increases rapidly in response to the increase of leakage multiplication, crosses and leaves lower-order correlations behind, when leakage multiplication is $$>$$ 1.3 that depends on detector efficiency and counter setting. Next, fission rates and doubles count rates by fast neutron and by thermal neutron in their coexisting system were derived algebraically. It was found that the number of induced fissions per unit time by fast neutron and by thermal neutron, the number of induced fissions ($$<$$ 1) by one source neutron, and individual doubles count rates were possible to be estimated from Rossi-alpha combined distribution and measured ratio of each area obtained by differential die-away self-interrogation and conventional assay data.

Journal Articles

A Modelling study on water radiolysis for primary coolant in PWR

Mukai, Satoru*; Umehara, Ryuji*; Hanawa, Satoshi; Kasahara, Shigeki; Nishiyama, Yutaka

Proceedings of 20th International Conference on Water Chemistry of Nuclear Reactor Systems (NPC 2016) (USB Flash Drive), 9 Pages, 2016/10

In Japanese PWR, the concentration of dissolved hydrogen in the primary coolant is controlled in the range from 25 cc/kg-H$$_{2}$$O to 35 cc/kg-H$$_{2}$$O for suppression of water decomposition. However this concentration is desired to reduce for the purpose of radiation source reduction in Japan. So, the concentration due to water radiolysis in primary coolant was evaluated at lower hydrogen concentration by the water radiolysis model in consideration of $$gamma$$ ray, fast neutron and alpha ray due to the reaction $$^{10}$$B(n,$$alpha$$)$$^{7}$$Li. The results of evaluation showed that the water radiolysis was suppressed even if the hydrogen concentration was decreased to 5 cc/kg-H$$_{2}$$O. The effects of the different G-value and the rate constants of major reaction on the concentration of H$$_{2}$$O$$_{2}$$ and O$$_{2}$$ were studied under hydrogen addition. We also focused on the effect of the alpha radiolysis in boron acid water.

Journal Articles

Safety handling characteristics of high-level tritiated water

Hayashi, Takumi; Ito, Takeshi*; Kobayashi, Kazuhiro; Isobe, Kanetsugu; Nishi, Masataka

Fusion Engineering and Design, 81(8-14), p.1365 - 1369, 2006/03

 Times Cited Count:18 Percentile:77.84(Nuclear Science & Technology)

In a fusion reactor, high-level tritiated water of more than GBq/ml will be generated and stored temporally in the various areas. High level tritiated water decomposes by itself and generates hydrogen and oxygen, and becomes to tritiated hydrogen peroxide water, however, effective G-values from tritiated water are different from those obtained $$gamma$$-ray experiments in our previous report. Furthermore, tritiated water of about 250GBq/ml has been stored for several years safely and checked its characteristics. Using the above experiences, this paper summarizes safety requirements for storage of high-level tritiated water and discusses design issues of the safety storage system. Concerning gaseous species, storage tank should be maintained at negative pressure and purged periodically or constantly to dedicated tritium removal system. Specially, it is important that the G-value of high-level tritiated water is increasing with decreasing the tritium concentration. The pH and ORP (Oxidation Reduction Potential) of tritiated water have been also changed depending on the tritium concentration and maintained for more than several years in glass vessel. High-level tritiated water of more than GBq/ml was acid and became to be corrosive depending on the dissolved species. Large amount of tritiated water will be stored in the various tanks of stainless steel, therefore, it should be monitored so that the liquid situation is maintained not to be corrosive.

Journal Articles

Time-dependence of differential G-values of OH radicals in water under Ne ion radiolysis

Taguchi, Mitsumasa; Kojima, Takuji

JAEA-Review 2005-001, TIARA Annual Report 2004, p.181 - 182, 2006/01

The yields of OH radicals in water containing phenol have been investigated for several ten MeV/n C ion and Ne ion having the same LET value, as a function of the residual ion energy at the specific depth in water. In this study, beside such energy dependence, the dependence of reaction time of OH radical yield was examined by changing the concentration of phenol as solute. The defferential G'-values of OH radicals, those G-values per kinetic energy of ions increase with specific energy of Ne ions. The G'-value just after irradiation(1.5ns) is relatively high but become lower with reaction time to be the value (2.7) obtained for $$^{60}$$Co $$gamma$$-rays. It suggests the diffusion behavior of OH radicals locally induced in water.

Journal Articles

Application of EGS4 code to evaluation of specific absorbed fractions and S values for internal dosimetry

Kinase, Sakae

KEK Proceedings 2005-3, p.292 - 297, 2005/06

The EGS4 code was used for evaluating the absorbed fraction per unit mass of the target organ-specific absorbed fraction (SAF)- and the mean absorbed dose to the target organ per unit cumulated activity in the source organ (S value) for internal dosimetry. The SAFs and S values were evaluated on a mathematical phantom (MIRD 5 type phantom) and Japanese adult voxel phantoms (Otoko and Onago phantoms) developed at the Japan Atomic Energy Research Institute (JAERI). The evaluated SAFs and S values were compared with several published data in order to demonstrate the use of the EGS4 code for the internal dosimetry and investigate the influence of certain parameters, such as the organ masses, on SAFs and S values. It was demonstrated that the EGS4 code is useful in the evaluation of the SAFs and S values for the internal dosimetry. It was also found that the SAFs and S values for organ self-absorption depend on the organ masses and would be affected by differences in the structure of the human body.

Journal Articles

Role of low order rational $$q$$-values in the ITB events in JT-60U reverse shear plasmas

Neudatchin, S. V.*; Takizuka, Tomonori; Hayashi, Nobuhiko; Isayama, Akihiko; Shirai, Hiroshi; Fujita, Takaaki; Kamada, Yutaka; Koide, Yoshihiko; Suzuki, Takahiro

Nuclear Fusion, 44(9), p.945 - 953, 2004/09

The formation of internal transport barriers (ITBs) near q=3 surfaces in normal shear (NrS) discharges of JT-60U is known. In reverse shear (RS) JT-60U plasmas, the role of q minimum (qmin) equal to 3.5,3,2.5,2 was not obvious for ITB formation. ITB-events (non-local confinement bifurcations inside and around ITB) are found in various NrS and RS plasmas. Under sufficient heating power, ITB-events are seen at rational and not rational values of qmin. The space-time evolution of Te and Ti is similar, suggesting the same mechanism of Te and Ti transport. The temporal formation of strong ITB under passing of qmin=3 (after periodical improvements and degradations via ITB-events) in RS mode is presented. Under smaller power, ITB-events are observed only at rational values of qmin. In a weak RS shot, abrupt rise of Te is seen at qmin=3.5, while more cases of Ti rise are observed. The difference of Te and Ti evolutions seen regularly under the low power, suggests decoupling of Te and Ti transport.

Journal Articles

Role of low order rational ${it q}$-values in the ITB events in JT-60U reverse shear plasmas

Neudatchin, S. V.*; Takizuka, Tomonori; Hayashi, Nobuhiko; Isayama, Akihiko; Shirai, Hiroshi; Fujita, Takaaki; Kamada, Yutaka; Koide, Yoshihiko; Suzuki, Takahiro

Nuclear Fusion, 44(9), p.945 - 953, 2004/09

 Times Cited Count:15 Percentile:46.65(Physics, Fluids & Plasmas)

The formation of internal transport barriers (ITBs) near ${it q}$ =2,3 surfaces in normal shear (NrS) discharges of JT-60U and JET is known. In reverse shear (RS) JT-60U plasmas, the role of ${it q}$ minimum (${it q}$$$_{min}$$) equal to 3.5,3,2.5,2 is not obvious for ITB formation. In this paper, the effect of low rational ${it q}$ values on ITB-events in JT-60U NrS and RS plasmas is investigated. Under sufficient neutral beam power (${it P}$$$_{nbi}$$$$>$$8MW for 1.2-1.5MA/3.8T pulses), ITB-events are seen at rational and non-rational values of ${it q}$$$_{min}$$. The space-time evolutions of ${it T}$$$_{e}$$ and ${it T}$$$_{i}$$ are similar, suggesting the same mechanism for ${it T}$$$_{e}$$ and ${it T}$$$_{i}$$ transports. The temporal formation of stronger ITB under passing ${it q}$$$_{min}$$=3 (after periodical improvements and degradations via ITB-events) in RS H-mode with ${it P}$$$_{nbi}$$=8MW is presented. Under smaller power, ITB-events are observed only at rational ${it q}$$$_{min}$$ values. In a weak RS shot with ${it P}$$$_{nbi}$$=4MW, the abrupt rise of ${it T}$$$_{e}$$ is seen at ${it q}$$$_{min}$$=3.5, while more cases of ${it T}$$$_{i}$$ rise are observed. The difference between the ${it T}$$$_{e}$$ and ${it T}$$$_{i}$$ evolutions for the low power suggests the decoupling of ${it T}$$$_{e}$$ and ${it T}$$$_{i}$$ transports.

Journal Articles

Theoretical study on the alloying behavior of $$gamma$$-uranium metal; $$gamma$$-uranium alloy with 3d transition metals

Kurihara, Masayoshi*; Hirata, Masaru; Sekine, Rika*; Onoe, Jun*; Nakamatsu, Hirohide*

Journal of Nuclear Materials, 326(2-3), p.75 - 79, 2004/03

 Times Cited Count:12 Percentile:63.15(Materials Science, Multidisciplinary)

We have investigated the alloying behavior of g-uranium with 3d transition metals (TMs) using the relativistic discrete-variational Dirac-Fock-Slater (DV-DFS) method. The d-orbital energy (Md) as an alloying parameter well reproduces the alloying behavior of g- uranium metal with TMs: (1) in the case of a large Md value (Ti,V,Cr), the solubility of these TM elements in g-uranium becomes large; (2) in the case of a middle Md value (Mn,Fe,Co), the tendency to form a uranium intermetallic compound with these elements becomes stronger; (3) in the case of a small Md value (Cu), the alloying element is insoluble in g-uranium. The alloying behavior of g-uranium with TMs is also discussed in terms of other parameters such as electronegativity and metallic radius.

Journal Articles

Evaluation of S values for beta-ray emitters within the urinary bladder

Kinase, Sakae; Zankl, M.*; Funabiki, Jun*; Noguchi, Hiroshi; Saito, Kimiaki

Journal of Nuclear Science and Technology, 41(Suppl.4), p.136 - 139, 2004/03

The present study was performed to evaluate S values to the urinary bladder wall for several beta-ray emitters such as $$^{14}$$C, $$^{24}$$Na, $$^{32}$$P, $$^{60}$$Co, $$^{89}$$Sr, $$^{90}$$Sr, $$^{90}$$Y, $$^{91}$$Y, $$^{137}$$Cs, $$^{147}$$Pm and $$^{204}$$Tl for a MIRD 5 type phantom using Monte Carlo simulation. S values were also evaluated on the adult voxel phantoms developed at JAERI and were compared with those for the MIRD 5 type phantom. Furthermore, each of the S values was compared with those derived from the simple assumption (ICRP 30). Consequently, it was found that the absorbed dose to the urinary bladder wall for those radionuclides are not one-half of the absorbed dose in bladder content and largely depend on the mass of the urinary bladder wall. S values derived from the simple assumption were found to be conservative for beta-ray emitters within the urinary bladder.

Journal Articles

Evaluation of S values for beta-ray emitters in voxel phantoms

Kinase, Sakae; Zankl, M.*; Funabiki, Jun*; Noguchi, Hiroshi; Saito, Kimiaki

KEK Proceedings 2003-15, p.45 - 52, 2004/02

no abstracts in English

JAEA Reports

Establishment of X-ray reference fields for performance tests of radiation measuring instruments based on international standard(ISO4037-1)

Shimizu, Shigeru; Zhang, Q.; Kajimoto, Yoichi; Kawasaki, Tomokatsu; Fujii, Katsutoshi

JAERI-Tech 2003-095, 52 Pages, 2004/01

JAERI-Tech-2003-095.pdf:2.66MB

The International Standards ISO4037-1 of the International Organization for Standardization widely applied in the world to construct X-ray reference fields for performance tests of radiation measuring instruments. The application of the current JAERI's X-ray reference field constructed in accordance with the Japanese Standards should be limited for domestic purposes becase of the characterization technique different from the International Standards. Therefore,for application to international performance tests, X-ray reference fields in the narrow,wide and high air-kerma series based on the International Standards were established using the medium-hard X-ray generator of the Facility of Radiation Standards(FRS), JAERI. This report presents quality characterization, estimation of X-ray spectra of each dose units of the new FRS's fields,and comparison of the qualities and the X-ray spectra to those of the ISO's. The FRS's qualities show good agreement with ISO's: the reference fields should serve for performance tests for international radiation protection purposes.

Journal Articles

Theory of the Newcomb equation and applications to MHD stability analysis of a tokamak

Tokuda, Shinji; Aiba, Nobuyuki*

Journal of Plasma and Fusion Research SERIES, Vol.6, p.207 - 209, 2004/00

Recent progress in the theory of the Newcomb equation is reported. Emphasis is put on the analysis of external modes including peeling modes (high $$n$$ kink modes), where $$n$$ is the toroidal mode number. A theory for low $$n$$ external modes is developed so that it is also useful for the analysis of resistive wall modes.

Journal Articles

Inner layer problem for ideal MHD modes in a toroidal system

Tokuda, Shinji

Proceedings of 30th EPS Conference on Controlled Fusion and Plasma Physics (CD-ROM), 4 Pages, 2003/00

When we solve the eigenvalue problem associated with the two-dimensional Newcomb equation, we can identify the stability of a tokamak plasma against ideal MHD perturbations. The eigenvalue problem does not give the physical growth rate when the plasma is unstable. However, we can determine the growth rate by constructing a dispersion relation that gives the relation between the growth rate and the eigenvalue. It is expected that the dispersion relation provides an effective and fast method of stability analysis of MHD modes close to the marginal stability against ideal MHD perturbations, and the relation can be extended for non-ideal MHD modes close to the marginal stability.

Journal Articles

First measurement of the quadrupole moment in the 2$$_1^+$$ state of $$^{84}$$Kr

Osa, Akihiko; Czosnyka, T.*; Utsuno, Yutaka; Mizusaki, Takahiro*; Toh, Yosuke; Oshima, Masumi; Koizumi, Mitsuo; Hatsukawa, Yuichi; Katakura, Junichi; Hayakawa, Takehito; et al.

Physics Letters B, 546(1-2), p.48 - 54, 2002/10

 Times Cited Count:10 Percentile:51.83(Astronomy & Astrophysics)

A $$^{84}$$Kr beam was Coulomb-excited on a $$^{98}$$Mo target and a $$^{nat}$$Ta target. Six reduced matrix elements for 5 low-lying states were derived from the analysis using the least-squares code GOSIA. The quadrupole moment of the 2$$_1^+$$ was newly obtained. The measured quadrupole moment and the $$B(E2)$$ values are consistent with large-scale shell-model calculations which give a systematic description of $$N$$,=,50 isotones.

Journal Articles

Singular point analysis

Tokuda, Shinji

Purazuma, Kaku Yugo Gakkai-Shi, 78(9), p.913 - 924, 2002/09

An introductory review is given on recent developments in the methods for stability analysis of a toroidally confined plasma. Emphasis is put on the perturbation analysis of a magnetohydrodynamic system that has the marginally stable state as a terminal point of continuous spectra. We address ourselves to the asymptotic matching method pertinent to such a problem. The Newcomb equation and inner-layer equations are essential ingredients in the methods and the numerical methods for solving them are discussed.

Journal Articles

Operational status of superconducting resonators of the JAERI tandem-booster

Takeuchi, Suehiro; Matsuda, Makoto; Ishizaki, Nobuhiro; Tayama, Hidekazu; Iijima, Akihiko*; Yoshida, Takahiro*

Proceeding of 10th Workshop on RF Superconductivity (SRF 2001), p.591 - 593, 2001/00

no abstracts in English

Journal Articles

Development of whole energy absorption spectrometer for decay heat measurement

Maekawa, Fujio; Wada, Masayuki*; Ikeda, Yujiro

Nuclear Instruments and Methods in Physics Research A, 450(2-3), p.467 - 478, 2000/08

 Times Cited Count:6 Percentile:44.88(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Evaluation method of performance of siphon break value as core covering system for water-cooled test and research reactors

; Kumada, Hiroaki; Kaminaga, Fumito*

Nihon Genshiryoku Gakkai-Shi, 42(4), p.325 - 333, 2000/04

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

93 (Records 1-20 displayed on this page)