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spectrometry of molten core material from Fukushima Daiichi Nuclear Power Station unit 1, 2 and 3 cores for special nuclear material accountancy; Low-volatile FP and special nuclear material inventory analysis and fundamental characteristics of -rays from fuel debrisSagara, Hiroshi; Tomikawa, Hirofumi; Watahiki, Masaru; Kuno, Yusuke
Journal of Nuclear Science and Technology, 51(1), p.1 - 23, 2014/01
Times Cited Count：9 Percentile：57.19(Nuclear Science & Technology)Feasibility study of spectrometry of molten core material from Fukushima Daiichi Nuclear Power Station Unit 1, 2 and 3 cores for special nuclear material accountancy has been performed, focusing on the low-volatile fission product and heavy metal inventory analysis, and fundamental characteristics of -ray from fuel debris for passive measurement. The inventory ratio of low-volatile lanthanides, 
Eu and 
Ce, to special nuclear material were evaluated by whole core inventory in unit 1, 2 and 3 cores as reference value for homogenized molten fuel material, and also as a function of burnup for specific fuel debris, considering the sensitivity of enrichment, specific power, water void fraction, cooling time, calculation tool accuracy and release ratio. The same indices could be applied to unit 3, while the uncertainty of specific fuel debris of separated MOX fuel would be increased significantly. Source photon spectrum results showed the detectability of low-volatile high energy -rays emitted from Eu at least in 20 years after the accident, that from Ce/Pr in 10 years, and volatile 
Cs and 
Cs at least in 20 years with 99% or more release ratio. Mass attenuation coefficients of fuel debris was evaluated to be insensitive to its compositions in high energy region. Leakage photon ratio was evaluated with variety of parameters and significant impact was confirmed with certain size of fuel debris, its correlation was summarized with respect to the photopeak ratio of source Eu. Finally, preliminary study with hypothetical canister model of fuel debris based on TMI-2 experience, and future plan were introduced.
Sagara, Hiroshi; Tomikawa, Hirofumi; Watahiki, Masaru; Kuno, Yusuke
Transactions of the American Nuclear Society, 107(1), p.803 - 804, 2012/11
Fission products(FPs) such as Eu, Ce, Ru have low release ratio in case of core melting event in severe accident to co-exist inside fuel debris in oxide or metallic phase, based on TMI-2 experience and source term experiments. Passive spectroscopy of Ce-144/Pr-144 was utilized in quantifying special nuclear material in fuel debris of TMI-2 historically, and the same methodology might be applied to high energy emitter, Eu-154 and Ru-106. Passive neutron measurement has been also utilized for quantifying nuclear material practically. Different from conventional spent fuel, however, fuel debris would be lost in information of irradiated profile, release ratio of volatile FPs, and so on. In the present paper, sensitivity analysis of low-volatile FPs and Cm-244 inventory in irradiated nuclear fuel in light water reactor was performed numerically to clarify the uncertainty of low-volatile FP and Cm inventory regarding fuel irradiation parameters and calculation methodology, and to derive applicable index to quantify nuclear material in fuel debris.
spectroscopy of low-volatile FPs for special nuclear material accountancy in molten core materialSagara, Hiroshi; Tomikawa, Hirofumi; Watahiki, Masaru; Kuno, Yusuke
Proceedings of INMM 53rd Annual Meeting (CD-ROM), 10 Pages, 2012/07
Reviewing the technologies applied to TMI-2, feasibility study of spectroscopy of low-volatile FPs for special nuclear material accountancy in molten core material or debris has been performed numerically, and the sensitivity of low-volatile FP nuclides on fuel contents, especially 
Pu, was studied with parameters of typical BWR fuel such as enrichment, burnup and neutron spectrum, heat density. Comparing TMI-2, a PWR reactor, broader neutron spectrum axial profile and irradiation cycle complexity of typical BWR fuel assemblies make more variance in the accumulation of daughter nuclides by neutron capture reactions. As results, Pu quantification, by burnup dependent Eu/Pu index has accuracy of 15-18% in 1-sigma level mainly affected by burnup uncertainty, and Pu quantification by Ce/Pu has accuracy of 20% as long as Ce released photon could be observed within 10 years, within the scope of inventory survey except for measurement uncertainty. Finally systematic image of fuel quantification by passive spectroscopy and, as future study, FPs quantification by passive measurement tests by mockup debris measurement with self-attenuation correction are introduced.
Tomikawa, Masaru*; Maeda, Tomoo*; Honda, Kazushige*; Saga, Koichi*; Ishikawa, Ryuji*; Akita, Yusuke; Yoshihara, Ryohei; Nozawa, Shigeki; Narumi, Issei
JAEA-Review 2010-065, JAEA Takasaki Annual Report 2009, P. 73, 2011/01
Tomikawa, Masaru*; Maeda, Tomoo*; Honda, Kazushige*; Saga, Koichi*; Ishikawa, Ryuji*; Akita, Yusuke; Nozawa, Shigeki; Narumi, Issei
no journal, ,
no abstracts in English
Maeda, Tomoo*; Tomikawa, Masaru*; Honda, Kazushige*; Saga, Koichi*; Ishikawa, Ryuji*; Akita, Yusuke; Yoshihara, Ryohei; Nozawa, Shigeki; Narumi, Issei
no journal, ,
no abstracts in English
Tomikawa, Hirofumi; Watahiki, Masaru; Kuno, Yusuke
no journal, ,
Japan is the only non-nuclear-weapon country with nuclear fuel cycle facilities including uranium enrichment and reprocessing facilities. The evolution of technologies has been instrumental in improving facility and safeguards efficiency. Older facilities with small material throughput operated almost manually. In contrast, more modern facilities with large material throughput were designed for improved throughput and accountancy and introduced state-of-art safeguards technologies. Japan has the experience of a series of new types of nuclear facilities which are pilot scale through commercial size. This paper presents the efforts and evolutions of the safeguards technology development introduced to the bulk handling facilities including uranium enrichment, reprocessing and MOX fuel fabrication facilities in Japan, through international cooperation. The evolution of technologies has benefited both the State/Operator and the IAEA.
spectrometry of low-volatile FPs for accountancy of special nuclear material in molten core material of Fukushima Daiichi Nuclear Power Plant; Detectability of leakage -ray and fundamental characteristics of U-Ce/Eu compoundTomikawa, Hirofumi; Sagara, Hiroshi*; Shiba, Tomooki*; Ishimi, Akihiro; Osaka, Masahiko; Watahiki, Masaru; Kuno, Yusuke
no journal, ,
For nuclear material accountancy of molten core material in Fukushima Daiichi Nuclear Power Station units 1, 2 and 3 (1F1, 1F2 and 1F3), a variety of technologies are being evaluated from the viewpoint of applicability for in-situ measurement. For one of the technologies, a feasibility study of passive spectroscopy of low-volatile fission products (FPs) has been performed by reviewing TMI-2 experience, and studying the correlation of actinides and FPs inventory in the cores of 1F1, 1F2 and 1F3, considering the sensitivity of axial neutron spectrum, void, burnup, enrichment distribution unique to BWR fuel, and leakage -ray from molten core materials sphere model. In this paper, numerical simulation of leakage -ray from molten core materials in a hypothetical canister is dealt with for determination of radioactivity of low-volatile high-energy emission FPs, which could be utilized for special nuclear material (SNM) quantity estimation coupled with SNM/FPs ratio derived from core inventory calculations. This paper also presents the summary of survey results of high-temperature chemical stability of lanthanides coexisting with nuclear material in a certain atmospheres and temperatures simulating severe accident.
