The Effect of base irradiation on failure behaviors of UO and chromia-alumina additive fuels under simulated reactivity-initiated accidents; A Comparative analysis with FEMAXI-8

Udagawa, Yutaka; Mihara, Takeshi; Taniguchi, Yoshinori; Kakiuchi, Kazuo; Amaya, Masaki

Annals of Nuclear Energy, 139, p.107268_1 - 107268_9, 2020/05

AA2019-0372.pdf:0.81MB

https://doi.org/10.1016/j.anucene.2019.107268

An Interpretation of Fukushima-Daiichi Unit 3 plant data covering the two-week accident-progression phase based on correction for pressure data

Sato, Ikken

Journal of Nuclear Science and Technology, 56(5), p.394 - 411, 2019/05

https://doi.org/10.1080/00223131.2019.1588798

Water columns were adopted in the pressure measurement system of Fukushima-Daiichi Unit-3. Part of these water columns evaporated during the accident condition jeopardizing correct understanding on actual pressure. Through comparison of RPV (Reactor Pressure Vessel) and S/C pressures with D/W pressure, such water-column effect was evaluated. Correction for this effect was developed enabling clarification of slight pressure difference among RPV, S/C and D/W. This information was then integrated with other available data such as, water level, CAMS and environmental dose rate, into an interpretation of accident focusing on RPV and PCV pressurization/depressurization and radioactive material release to environment. It is suggested that dryout of in-vessel and ex-vessel debris was likely causing pressure decrease. S/C water poured into pedestal heated by relocated debris was the likely cause of pressurization. Cyclic reflooding of pedestal debris and dryout was likely.

Validation of MOSRA-SRAC for burnup of a BWR fuel assembly

Kojima, Kensuke

Proceedings of International Conference on the Physics of Reactors; Unifying Theory and Experiments in the 21st Century (PHYSOR 2016) (USB Flash Drive), p.3283 - 3292, 2016/05

The MOSRA system has been developing to improve the applicability of the neutronic characteristic analyses. The cell calculation module MOSRA-SRAC is a core module of MOSRA, and applicability tests for realistic problems are required. As a test, MOSRA-SRAC is validated by comparison with measured values. As the measurement, the post irradiation examination SFCOMPO 99-5 is chosen. In the examination, the compositions of major heavy metal and fission product nuclides in a UO-GdO fuel rod pulled from the 88 BWR fuel assembly used in TEPCO's Fukushima-Daini-2 were measured. The result shows good agreement between calculated and measured value. For uranium and plutonium nuclides, calculated values agree within 5% except for Pu. Pu composition is overestimated by 30%, and the overestimation is caused by the unclearness of the void faction history of the fuel rod. For fission products, calculated values agree within approximately 10%.

Fission gas release in irradiated UO fuel at burnup of 45 GWd/t during simulated Reactivity Initiated Accident (RIA) condition

Amaya, Masaki; Sugiyama, Tomoyuki; Fuketa, Toyoshi

Journal of Nuclear Science and Technology, 41(10), p.966 - 972, 2004/10

https://doi.org/10.3327/jnst.41.966

Pulse irradiation simulating RIA condition was carried out for test rod prepared from fuel irradiated in a commercial reactor. After the pulse irradiation, optical microscopy (OM) and scanning electron microscopy (SEM) observations and electron probe micro analysis (EPMA) were conducted for the test rod as a part of destructive tests. Fission gas release behavior during pulse irradiation was investigated by EPMA and puncture test. Xeon depression was observed in the fuel pellet after pulse irradiation at periphery and center region. It is considered that fission gas was mainly released from the pellet center region during pulse irradiation. The amount of xenon release during pulse irradiation was estimated to be 10-12% from the EPMA results and this estimated value was comparable with the puncture test result. Comparing the estimated value with other results of out-of-pile annealing tests, it was concluded that most fission gas, which was accumulated at grain boundary during base irradiation, was released from the center region of test fuel pellet during pulse irradiation.

Classification of criticality calculations with correlation coefficient method and its application to OECD/NEA burnup credit benchmarks phase III-A and II-A

Okuno, Hiroshi

Journal of Nuclear Science and Technology, 40(7), p.544 - 551, 2003/07

https://doi.org/10.3327/jnst.40.544

A method for classifying benchmark results of criticality calculations according to similarity was proposed in this paper. After formulation of the method utilizing correlation coefficients, it was applied to burnup credit criticality benchmarks Phase III-A and II-A, which were conducted by the Expert Group on Burnup Credit Criticality Safety under auspices of the OECD/NEA. Phase III-A benchmark was a series of criticality calculations for irradiated BWR fuel assemblies, whereas Phase II-A benchmark was a suite of criticality calculations for irradiated PWR fuel pins. These benchmark problems and their results were summarized. The correlation coefficients were calculated and sets of benchmark results were classified according to the criterion that the correlation coefficients were no less than 0.15 for Phase III-A and 0.10 for Phase II-A benchmarks. When a couple of results were in a same group, one result was found predictable from the other. An example was shown for each of the Benchmarks. The evaluated nuclear data seemed the main factor of errors.

Irradiated fuel behavior under power oscillation conditions

Nakamura, Takehiko; Nakamura, Jinichi; Sasajima, Hideo; Uetsuka, Hiroshi

Journal of Nuclear Science and Technology, 40(5), p.325 - 333, 2003/05

https://doi.org/10.3327/jnst.40.325

In order to examine high burnup fuel performance and to confirm its integrity under unstable power oscillation conditions arising during an ATWS in BWRs, two tests of irradiated fuels under simulated power oscillation conditions were conducted in the NSRR. Irradiated fuels at burnups of 25 and 56GWd/tU were subjected to four to seven power oscillations, which peaked at 50 to 95kW/m with intervals of 2s. The power oscillation was simulated by quick withdrawal and insertion of six regulating rods of the NSRR with a computerized control. Deformation of the fuel cladding of the test rods was comparable to those observed in shorter transient tests, which simulated RIAs, at the same fuel enthalpy level up to 368J/g. The fuel deformation was mainly caused by PCMI and was roughly proportional to the fuel enthalpy. Enhanced cladding deformation due to ratcheting by the cyclic load was not observed. Fission gas release, on the other hand, was considerably smaller than in the RIA tests, suggesting different release mechanisms in the two types of transients.

Benchmark results of burn-up calculation for LWR next generation fuels

Okumura, Keisuke; Unesaki, Hironobu*; Kitada, Takanori*; Saji, Etsuro*

Proceedings of International Conference on the New Frontiers of Nuclear Technology; Reactor Physics, Safety and High-Performance Computing (PHYSOR 2002) (CD-ROM), 10 Pages, 2002/10

In order to investigate the calculation accuracy of the nuclear characteristics of LWR next generation fuels, the Research Committee on Reactor Physics organized by Japan Atomic Energy Research Institute has proposed "Reactor Physics Benchmark for LWR Next Generation Fuels". The next generation fuels aim at very high burn-up of about 70GWd/t in PWR or BWR with UO2 or MOX fuels whose fissile enrichments may exceed the Japanese regulatory limitations for the current LWR fuels such as 5wt.% U-235. Twelve organizations have carried out the analyses of the benchmark problems with different codes and data, and their submitted results have been compared. As a result, status of accuracy with the current data and method and some problems to be solved in the future were clarified.

OECD/NEA burnup credit criticality benchmarks phase IIIB; Burnup calculations of BWR fuel assemblies for storage and transport

Okuno, Hiroshi; Naito, Yoshitaka*; Suyama, Kenya

JAERI-Research 2002-001, 181 Pages, 2002/02

JAERI-Research-2002-001.pdf:10.89MB

The report describes the final results of the Phase IIIB Benchmark conducted by the Expert Group on Burnup Credit Criticality Safety under the auspices of the OECD/NEA. The Benchmark was intended to compare the predictability of current computer code and data library combinations for the atomic number densities of an irradiated BWR fuel assembly model, which was irradiated under specific power of 25.6 MW/tHM up to 40 GWd/tHM and cooled for five years. The void fraction was assumed to be uniform and constant, at 0, 40 and 70%, during burnup. In total, 16 results were submitted from 13 institutes of 7 countries. The calculated densities of 12 actinides and 20 fission product nuclides were found mostly within a range of +- 10% relative to the average, although some results, esp. 155Eu and gadolinium isotopes, exceeded the band. Pin-wise burnup results agreed well among the participants. The results in the multiplication factor also accorded well with each other for void fractions of 0 and 40%; however some results deviated from the average noticeably for the void fraction of 70%.

Proposal and analysis of the benchmark problem suite for reactor physics study of LWR next generation fuels

Research Committee on Reactor Physics

JAERI-Research 2001-046, 326 Pages, 2001/10

JAERI-Research-2001-046.pdf:14.45MB

The Working Party on Reactor Physics for LWR Next Generation Fuels in the Research Committee on Reactor Physics, which is organized by the Japan Atomic Energy Research Institute, has recently proposed a series of benchmark problems to investigate the calculation accuracy of the nuclear characteristics of LWR next generation fuels. The next generation fuels mean the ones aiming for further extended burnup such as 70GWd/t over the current design. The resultant specifications of the benchmark problem therefore neglect some of the current limitations such as 5wt%235U to achieve the above-mentioned target. The Working Party proposed six benchmark problems, which consist of pin-cell, PWR assembly and BWR assembly geometries loaded with uranium and MOX fuels, respectively. The present report describes the detailed specifications of the benchmark problems. The results of preliminary analyses performed by the eleven member organizations and their comparisons are also presented.

Evaluation of burnup characteristics and energy deposition during NSRR pulse irradiation tests on irradiated BWR fuels

Nakamura, Takehiko; Takahashi, Masato*; Yoshinaga, Makio

JAERI-Research 2000-048, 77 Pages, 2000/11

JAERI-Research-2000-048.pdf:6.04MB

no abstracts in English