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Journal Articles

Criticality configuration design methodology applied to the design of fuel debris experiment in the new STACY

Gunji, Satoshi; Tonoike, Kotaro; Clavel, J.-B.*; Duhamel, I.*

Journal of Nuclear Science and Technology, 58(1), p.51 - 61, 2021/01

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

The new critical assembly STACY will be able to contribute to the validation of criticality calculations related to the fuel debris. The experimental core designs are in progress in the frame of JAEA/IRSN collaboration. This paper presents the method applied to optimize the design of the new STACY core to measure the criticality characteristics of pseudo fuel debris that simulated Molten Core Concrete Interaction (MCCI) of the fuel debris. To ensure that a core configuration is relevant for code validation, it is important to evaluate the reactivity worth of the main isotopes of interest and their k$$_{rm eff}$$ sensitivity to their cross sections. In the case of the fuel debris described in this study, especially for the concrete composition, silicon is the nucleus with the highest k$$_{rm eff}$$ sensitivity to the cross section. For this purpose, some parameters of the core configuration, as for example the lattice pitches or the core dimensions, were adjusted using optimization algorithm to find efficiently the optimal core configurations to obtain high sensitivity of silicon capture cross section. Based on these results, realistic series of experiments for fuel debris in the new STACY could be defined to obtain an interesting feedback for the MCCI. This methodology is useful to design other experimental conditions of the new STACY.

Journal Articles

A Simple and practical correction technique for reactivity worth of short-sized samples measured by critical-water-level method

Kitamura, Yasunori*; Fukushima, Masahiro

Nuclear Science and Engineering, 186(2), p.168 - 179, 2017/05

 Times Cited Count:1 Percentile:13.14(Nuclear Science & Technology)

An inconsistency between the reactivity worth of short-size samples measured by the critical-water-level (CWL) method and that conventionally analysed for validating the nuclear data and the nuclear calculation methods has been known. The present study investigated this inconsistency in terms of a simple theoretical framework and proposed a simple and practical technique for correcting the measured sample reactivity worth without making supplementary experiments. A series of Monte Carlo calculations that simulated typical sample reactivity worth measurement by the CWL method showed that this inconsistency is effectively reduced by the present correction technique.

JAEA Reports

Criticality safety evaluation for the direct disposal of used nuclear fuel; preparation of data for burnup credit evaluation (Contract research)

Yamamoto, Kento*; Akie, Hiroshi; Suyama, Kenya; Hosoyamada, Ryuji*

JAEA-Technology 2015-019, 110 Pages, 2015/10


In the direct disposal of used nuclear fuel (UNF), criticality safety evaluation is one of the important issues since UNF contains some amount of fissile material. The recent development of higher-enrichment fuel has enhanced the benefit of the application of Burnup Credit. In the present study, the effects of the several parameters on the reactivity of disposal canister model were evaluated for used PWR fuel. The parameters are relevant to the uncertainties of depletion calculation code, irradiation history, and axial and horizontal burnup distribution, which are known to be important effect in the criticality safety evaluation adopting burnup credit. The latest data or methodology was adopted in this evaluation, based on the various latest studies. The appropriate margin of neutron multiplication factor in the criticality safety evaluation for UNF can be determined by adopting the methodology described in the present study.

Journal Articles

CFD analysis

Takase, Kazuyuki; Misawa, Takeharu*

Supercritical-Pressure Light Water Cooled Reactors, p.301 - 319, 2014/12

no abstracts in English

Journal Articles

Subchannel analysis of 37-rod tight-lattice bundle experiments for reduced-moderation water reactor

Nakatsuka, Toru; Tamai, Hidesada; Akimoto, Hajime

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10

The subchannel analysis code NASCA was applied to critical power prediction of 37-rod tight-lattice bundle experiments which JAERI has been carrying out to confirm the thermal-hydraulic feasibility of the RMWR. The NASCA can yield good predictions of critical power for the gap width of 1.3 mm while the prediction accuracy of critical power deteriorated in case of the gap width of 1.0 mm. Predicted BT positions agree with the experimental results. Models in the code will be improved to consider the effect of the gap width based on further studies in the future.

Journal Articles

Critical power prediction for tight lattice rod bundles

Liu, W.; Onuki, Akira; Tamai, Hidesada; Akimoto, Hajime

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 5 Pages, 2005/10

In this research, the newest version of critical power correlation for tight-lattice rod bundles is proposed by using 7-rod and 37-rod bundle data derived in Japan Atomic Energy Research Institute (JAERI). For comparatively high mass velocity region, the correlation is written in local critical heat flux - critical quality type. For low mass velocity region, it is written in critical quality - annular flow length type. The correlation is verified by JAERI data and Bettis Atomic Power Laboratory data. It is confirmed the correlation is able to give good prediction for the effects of mass velocity, inlet temperature, pressure and heated equivalent diameter on critical power. The correlation is further implemented into TRAC code to analyze flow decrease and power increase transients. It is confirmed transient BT can be predicted within the accuracy of the implemented critical power correlation.

JAEA Reports

Benchmark analysis of KRITZ-2 critical experiments

Okumura, Keisuke; Kawasaki, Kenji*; Mori, Takamasa

JAERI-Research 2005-018, 64 Pages, 2005/08


In the KRITZ-2 critical experiments, criticality and pin power distributions were measured at room temperature and high temperature (about 245 degree C) for three different cores loading slightly enriched UO$$_{2}$$ or MOX fuels. For nuclear data testing, benchmark analysis was carried out with a continuous-energy Monte Carlo code MVP and its four nuclear data libraries based on JENDL-3.2, JENDL-3.3, JEF-2.2 and ENDF/B-VI.8. As a result, fairly good agreements with the experimental data were obtained with any libraries for the pin power distributions. However, the JENDL-3.3 and ENDF/B-VI.8 give under-prediction of criticality and too negative isothermal temperature coefficients for slightly enriched UO$$_{2}$$ cores, while the older nuclear data JENDL-3.2 and JEF-2.2 give rather good agreements with the experimental data. From the detailed study with an infinite unit cell model, it was found that the differences among the libraries are mainly due to the different fission cross section of U-235 in the energy rage below 1.0 eV.

Journal Articles

Evaluation of $$gamma$$-ray dose components in criticality accident situations

Sono, Hiroki; Yanagisawa, Hiroshi*; Ono, Akio*; Kojima, Takuji; Soramasu, Noboru*

Journal of Nuclear Science and Technology, 42(8), p.678 - 687, 2005/08

 Times Cited Count:4 Percentile:31.53(Nuclear Science & Technology)

Component analysis of $$gamma$$-ray doses in criticality accident situations is indispensable for further understanding on emission behavior of $$gamma$$-rays and accurate evaluation of external exposure to human bodies. Such dose components were evaluated, categorizing $$gamma$$-rays into four components: prompt, delayed, pseudo components in the period of criticality, and a residual component in the period after the termination of criticality. This evaluation was performed by the combination of dosimetry experiments at the TRACY facility using a thermoluminescent dosimeter (TLD) made of lithium tetra borate and computational analyses using a Monte Carlo code. The evaluation confirmed that the dose proportions of the above components varied with the distance from the TRACY core tank. This variation was due to the difference in attenuation of the individual components with the distance from the core tank. The evaluated dose proportions quantitatively clarified the contribution of the pseudo and the residual components to be excluded for accurate evaluation of $$gamma$$-ray exposure.

JAEA Reports

Rod displacement measurements by X-ray CT and its impact on thermal-hydraulics in tight-lattice rod bundle (Joint research)

Mitsutake, Toru*; Katsuyama, Kozo*; Misawa, Takeharu; Nagamine, Tsuyoshi*; Kureta, Masatoshi*; Matsumoto, Shinichiro*; Akimoto, Hajime

JAERI-Tech 2005-034, 55 Pages, 2005/06


In tight-lattice bundles with about 1mm gap between rods, a rod displacement might affect thermal-hydraulic characteristics. The inside-structure observation of the simulated seven-rod bundle of RMWR was made with the high-energy X-ray CT of JNC. The CT view assured that the rod position was almost the same as expected by design. In the heat transfer experiments, all thermocouples on the center rod showed almost simultaneous BT-induced temperature increase and on the same axial heights showed quite similar time-variation behaviors in the vapor cooling heat transfer regime. It showed that the effect of the geometrical asymmetry was small on the BT characteristics. The calculated critical power by subchannel analysis with the input of the CT measured rod position was smaller by about 5% than that with the designed rod position. It concluded that the error in the calculated critical power was attributable not to the asymmetry in the rod position, but to the models in the subchannel analysis code.

Journal Articles

Rod displacement effect on thermal-hydraulic behaviour in tight-lattice bundle based on X-ray CT measurement

Mitsutake, Toru*; Akimoto, Hajime; Misawa, Takeharu; Kureta, Masatoshi*; Katsuyama, Kozo*; Nagamine, Tsuyoshi*; Matsumoto, Shinichiro*

Proceedings of 4th World Congress on Industrial Process Tomography, Vol.1, p.348 - 353, 2005/00

An inside-structure observation of a tight-lattice 7-rod bundle was made, using the high-energy X-ray computer tomography(CT) apparatus. The two-dimensional configurations of all rods were obtained at seventy-six axial height positions over the whole length of the bundle. The measured results of the rod positions showed small rod position displacements, about 0.5 millimeters at maximum, from the lattice positions. Based on these measured rod position displacement results, the flow area, equivalent hydraulic diameter, rod-rod clearance, and rod-shroud clearance were calculated. The effect of rod position displacement on critical power was estimated by a sub-channel analysis. The result showed that the rod position displacement effect has only a small effect on critical power calculations. The calculated critical power still overestimated the measured value.

JAEA Reports

Annual report on analytical works in NUCEF in FY. 2002

Sakai, Yutaka; Gunji, Kazuhiko; Haga, Takahisa*; Fukaya, Hiroyuki; Sonoda, Takashi; Sakazume, Yoshinori; Akutsu, Hideyuki; Niitsuma, Yasushi; Shirahashi, Koichi; Sato, Takeshi

JAERI-Tech 2004-006, 25 Pages, 2004/02


Analyses of the uranyl nitrate solution fuel are carried out at the analytical laboratory, NUCEF (the Nuclear Fuel Cycle Engineering Research Facility), which provide essential data for the operations of STACY (the Static Experiment Critical Facility), TRACY (the Transient Experiment Critical Facility) and the fuel treatment system. In the FY 2002, analyses of the uranyl nitrate solution fuel from STACY/TRACY on its pre- and post-operations, analyses of the uranyl nitrate solution under preparation stage for the fuel and analyses for nuclear material accountancy purpose, have been conducted. In addition, analyses on the preliminary tests to confirm adjustment condition of plutonium solution fuel for its further use at STACY, and analyses on the americium extraction/separation tests to provide americium for the research on high temperature chemistry of TRU, were conducted. A total number of analytical samples in the FY 2002 were 275. This report summarizes works related to the analyses and management of the analytical laboratory in the FY 2002.

JAEA Reports

Present status of chemical analysis of uranyl nitrate solution used for the criticality experiments in NUCEF

Haga, Takahisa*; Gunji, Kazuhiko; Fukaya, Hiroyuki; Sonoda, Takashi; Sakazume, Yoshinori; Sakai, Yutaka; Niitsuma, Yasushi; Togashi, Yoshihiro; Miyauchi, Masakatsu; Sato, Takeshi; et al.

JAERI-Tech 2004-005, 54 Pages, 2004/02


Criticality experiments using uranyl nitrate solution fuel are being conducted at STACY (the Static Experiment Critical Facility) and TRACY (the Transient Experiment Critical Facility) in NUCEF (the Nuclear Fuel Cycle Safety Engineering Research Facility). Chemical analyses of the solution have been carried out to take necessary data for criticality experiments, for treatment and control of the fuel, and for safeguards purpose at the analytical laboratory placed in NUCEF. About 300 samples are analyzed annually that provide various kinds of data, such as uranium concentration, isolation acid concentration, uranium isotopic composition, concentration of fission product (FP) nuclides, tri-butyl phosphoric acid (TBP) concentration, impurities in the solution fuel and so on. This report summarizes the analytical methods and quality management of the analysis for uranyl nitrate solution relating to the criticality experiments.

JAEA Reports

Summary of the 6th Workshop on the Reduced-Moderation Water Reactor; March 6, 2003, JAERI, Tokai

Nabeshima, Kunihiko; Nakatsuka, Toru; Ishikawa, Nobuyuki; Uchikawa, Sadao

JAERI-Conf 2003-020, 240 Pages, 2003/11


The research on Reduced-Moderation Water Reactors (RMWRs) has been performed in JAERI for the development of future innovative reactors. The workshop on the RMWRs has been held every year since 1998 aimed at information exchange between JAERI and other organizations such as universities, laboratories, utilities and vendors. The workshop began with five lectures on status of research and development on RMWRs in JAERI entitled "Status and Future Program of Research and Development on Reduced-Moderation Water Reactors", "Design of Small Reduced-Moderation Water Reactors", "Critical Experiments for Reduced-Moderation Water Reactors", "Critical Heat Flux Experiments in Tight Lattice Core" and "Development of High Performance Cladding". Then two lectures followed: "Status of Phase II of Feasibility Studies on Commercialized Fast Breeder Reactor System" by JNC and "Present Status of Study on Super-critical water Cooled Power Reactor" by Toshiba Corporation.

Journal Articles

Subchannel analysis of CHF experiments for tight-lattice core

Nakatsuka, Toru; Tamai, Hidesada; Kureta, Masatoshi; Okubo, Tsutomu; Akimoto, Hajime; Iwamura, Takamichi

Proceedings of International Conference on Global Environment and Advanced Nuclear Power Plants (GENES4/ANP 2003) (CD-ROM), 6 Pages, 2003/09

It is important to evaluate thermal margin of the tight lattice core in the Reduced-Moderation Water reactor (RMWR). In the present study, to assess the applicability of subchannel analysis for tight lattice cores, tight lattice CHF experiments were analyzed with COBRA-TF code. For the axial uniform heated rod bundle, the code gives good prediction of critical power for mass velocity of around 500kg/(m$$^{2}$$s), while the code underestimates it for lower mass velocity and overestimates for higher mass velocity. The predicted BT position was outer channels and differed from the measured position. For the axially double-humped heated bundle, the code gives good prediction for mass velocity of around 200kg/(m$$^{2}$$s), and overestimates for higher mass velocity. It turned out that the two-phase multiplier of friction loss have a large influences on the flow distribution among the subchannels. To improve the calculation accuracy, it is required to predict precisely the flow distribution including the prediction of pressure distribution in a tight lattice bundle.

Journal Articles

Detailed dose assessment for the heavily exposed workers in the Tokai-mura criticality accident

Endo, Akira; Yamaguchi, Yasuhiro; Takahashi, Fumiaki

Radiation Risk Assessment Workshop Proceedings, p.151 - 156, 2003/00

We have developed a new system using numerical simulation technique for analyzing dose distribution in various postures by neutron, photon and electron exposures. The system consists of mathematical human phantoms with movable arms and legs and Monte Carlo codes MCNP and MCNPX. This system was applied to the analysis of dose distribution for the heavily exposed workers in the Tokai-mura criticality accident. The paper describes the simulation technique employed and a summary of the dose analysis.

JAEA Reports

Annual report on analytical works in NUCEF in FY. 2001

Sakazume, Yoshinori; Gunji, Kazuhiko; Haga, Takahisa*; Fukaya, Hiroyuki; Sonoda, Takashi; Sakai, Yutaka; Niitsuma, Yasushi; Shirahashi, Koichi; Sato, Takeshi

JAERI-Tech 2002-073, 25 Pages, 2002/09


Analytical results of uranyl nitrate solution are essential data for the operation of the Static Experiment Critical Facility (STACY), the Transient Experiment Critical Facility (TRACY) and the fuel treatment system in the Nuclear Fuel Cycle Safety Engineering Research Facility (NUCEF). Analytical works were carried out for the determination of fuel characteristics before and after criticality experiments, fuel preparation and nuclear material accountancy in FY. 2001. Moreover,as to preparation of critical experiments at STACY, plutonium preliminary tests were carried out to confirm the treatment condition (characteristics of the dissolution of the mixed oxide (MOX) powder and the extraction & separation for uranium / plutonium) of plutonium nitrate solution. Analytical works were carried out on the preliminary tests. A total number of analytical samples in FY. 2001 were 322 samples.This report summarizes the data on analytical works in FY.2001.

Journal Articles

Analysis of a uranium solution for evaluating the total number of fissions in the JCO criticality accident in Tokai-mura

Uchiyama, Gunzo; Watanabe, Kazuo; Miyauchi, Masakatsu; Togashi, Yoshihiro; Nakahara, Yoshinori; Fukaya, Hiroyuki; Inagawa, Jun; Suzuki, Daisuke; Sonoda, Takashi; Kono, Nobuaki; et al.

Journal of Radiation Research, 42(Suppl.), p.S11 - S16, 2001/10

no abstracts in English

Journal Articles

Benchmark analysis of experiments in fast critical assemblies using a continuous-energy monte carlo code MVP

Nagaya, Yasunobu; Nakakawa, Masayuki; Mori, Takamasa

Journal of Nuclear Science and Technology, 35(1), p.6 - 19, 1998/01

 Times Cited Count:3 Percentile:32.54(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Installation and execution of criticality and radiation shielding analysis codes on engineering work station

Masukawa, Fumihiro; ; Inoue, Osamu*; Hara, Toshiharu*

JAERI-M 93-024, 31 Pages, 1993/02


no abstracts in English

Journal Articles

A New CHF correlation scheme proposed for vertical rectangular channels heated from both sides in nuclear research reactors

Kaminaga, Masanori; Sudo, Yukio

Proc. of the 1st JSME/ASME Joint Int. Conf. on Nuclear Engineering,Vol. 1, p.73 - 79, 1991/00

no abstracts in English

33 (Records 1-20 displayed on this page)