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Hirooka, Shun; Nakamichi, Shinya; Matsumoto, Taku; Tsuchimochi, Ryota; Murakami, Tatsutoshi
Frontiers in Nuclear Engineering (Internet), 2, p.1119567_1 - 1119567_7, 2023/03
Storage of plutonium (Pu)-containing materials requires extremely strict attention in terms of physical safety and material accounting. Despite the emphasized importance of storage management, only a few reports are available in the public, e.g., experience in PuO
storage in the UK and safety standards in the storage of Pu-containing materials in the US. Japan also stores more U-Pu mixed oxide (MOX) mostly in powder form. Adopting an appropriate storage management is necessary depending on the characteristics of MOX items such as raw powder obtained by reprocessing of spent Light Water Reactor fuels, research and development on the remains of fuel fabrication, which can contain organic materials, and dry-recycled powder during fuel fabrication. Stagnation in fuel fabrications and experience in degradation of MOX containers during extended period of storage have led to the review of the storage method in the Plutonium Fuel Development Center in Japan Atomic Energy Agency. The present work discusses the various nuclear materials, storage methods, experience in degradation of containers that occur during storage, and strategies for future long-term storage.
Komuro, Michiyasu; Kanazawa, Hiroyuki; Kokusen, Junya; Shimizu, Osamu; Honda, Junichi; Harada, Katsuya; Otobe, Haruyoshi; Nakada, Masami; Inagawa, Jun
JAEA-Technology 2021-042, 197 Pages, 2022/03
JAEA-Technology-2021-042.pdf:16.87MB
Plutonium Research Building No.1 was constructed in 1960 for the purpose of establishing plutonium handling technology and studying its basic physical properties. Radiochemical research, physicochemical research and analytical chemistry regarding solutions and solid plutonium compounds had been doing for the research program in Japan Atomic Energy Agency (JAEA). In 1964, the laboratory building was expanded and started the researching plutonium-uranium mixed fuel and reprocessing of plutonium-based fuel, playing an advanced role in plutonium-related research in Japan. Since then, the research target has been expanded to include transplutonium elements, and it has functioned as a basic research facility for actinides. The laboratory is constructed by concrete structure and it has the second floor, equipped with 15 glove boxes and 4 chemical hoods. Plutonium Research Building No.1 was decided as one of the facilities to be decommissioned by Japan Atomic Energy Agency Reform Plan in September 2014. So far, the contamination survey of the radioactive materials in the controlled area, the decontamination of glove boxes, and the consideration of the equipment dismantling procedure have been performed as planned. The radioisotope and nuclear fuel materials used in the facility have been transfer to the other facilities in JAEA. The decommissioning of the facility is proceeding with the goal of completing by decommissioning the radiation controlled area in 2026. In this report, the details of the decommissioning plan and the past achievements are reported with the several data.
Hemmi, Ko; Walker, A.*; Yamaguchi, Tetsuji
Radiochimica Acta, 109(7), p.539 - 546, 2021/07
Times Cited Count：0 Percentile：0.01(Chemistry, Inorganic & Nuclear)Plutonium(IV) sorption onto quartz in carbonate solutions was systematically investigated under anaerobic conditions to analyze the sorption behaviors of Pu(IV) with a non-electrostatic model (NEM). Pu(IV) sorption data was obtained from batch sorption experiments as a function of pH and carbonate concentration. The Pu(IV) sorption onto quartz showed similar tendencies to Th(IV), which is considered to be chemically analogous as a tetravalent actinoid. The distribution coefficient, 
d, of Pu(IV) onto quartz showed inverse proportionality to the square of the total carbonate concentration under the investigated pH conditions of 8 to 11. The modeling study, however, revealed a Th(IV) sorption model, which is 
SOTh(OH)
and SOThOH(CO
)
, could not be applied to simulate the Pu(IV) sorption onto quartz. It was inferred that the electrostatic repulsion between negatively charged ligands limited the formation of SOM(OH) and SOMOH(CO) for Pu(IV) with smaller ionic radii than Th(IV). The Pu(IV) sorption model was developed as SOPu(OH) and SOPu(OH). In addition, data of Pu(IV) sorption onto muscovite was obtained in order to be compared with data for quartz.
Task Force on Writing Textbook of Nuclear Fuel Materials
JAEA-Review 2020-007, 165 Pages, 2020/07
JAEA-Review-2020-007.pdf:6.63MB
The present textbook was written by Task Force on Writing Textbook of Nuclear Fuel Materials at the Nuclear Science Research Institute in order to improve technological abilities of engineers and researchers who handle nuclear fuel materials. The taskforce consists of young and middle class engineers each having certification for chief engineer of nuclear fuel. The present textbook mainly deals with uranium and plutonium, and shows their nuclear properties, physical and chemical properties, and radiation effects on materials and human body. It also presents basic matters for safety handling of nuclear fuel materials, such as handling of nuclear fuel materials with hood and glovebox, important points in storage and transportation of nuclear fuel materials, radioactive waste management, radiation safety management, and emergency management. Furthermore, incident cases at domestic and foreign nuclear fuel materials facilities are compiled to learn from the past.
Aoki, Takeshi; Chirayath, S. S.*; Sagara, Hiroshi*
Annals of Nuclear Energy, 141, p.107325_1 - 107325_7, 2020/06
Times Cited Count：2 Percentile：31.22(Nuclear Science & Technology)The proliferation resistance (PR) of an inert matrix fuel (IMF) in the transuranic nuclear fuel cycle (NFC) of a high temperature gas cooled reactor is evaluated relative to the uranium and plutonium mixed-oxide (MOX) NFC of a light water reactor using PRAETOR code and sixty-eight input attributes. The objective is to determine the impacts of chemical stability of IMF and fuel irradiation on the PR. Specific material properties of the IMF, such as lower plutonium content, carbide ceramics coating, and absence of 
U, contribute to enhance its relative PR compared to MOX fuel. The overall PR value of the fresh IMF (an unirradiated direct use material with a one-month diversion detection timeliness goal) is nearly equal to that of the spent MOX fuel (an irradiated direct use nuclear material with a three-month diversion detection timeliness goal). Final results suggest a reduced safeguards inspection frequency to manage the IMF.
Ueta, Shohei; Mizuta, Naoki; Fukaya, Yuji; Goto, Minoru; Tachibana, Yukio; Honda, Masaki*; Saiki, Yohei*; Takahashi, Masashi*; Ohira, Koichi*; Nakano, Masaaki*; et al.
Nuclear Engineering and Design, 357, p.110419_1 - 110419_10, 2020/02
Times Cited Count：1 Percentile：16.13(Nuclear Science & Technology)The concept of a plutonium (Pu) burner HTGR is proposed to incarnate highly-effective Pu utilization by its inherent safety features. The security and safety fuel (3S-TRISO fuel) employs the coated fuel particle with a fuel kernel made of plutonium dioxide (PuO) and yttria stabilized zirconia (YSZ) as an inert matrix. This paper presents feasibility study of Pu burner HTGR and R&D on the 3S-TRISO fuel.
Fukushima, Masahiro; Goda, J.*; Oizumi, Akito; Bounds, J.*; Cutler, T.*; Grove, T.*; Hayes, D.*; Hutchinson, J.*; McKenzie, G.*; McSpaden, A.*; et al.
Nuclear Science and Engineering, 194(2), p.138 - 153, 2020/02
Times Cited Count：6 Percentile：56.26(Nuclear Science & Technology)To validate lead (Pb) nuclear cross sections, a series of integral experiments to measure lead void reactivity worth was conducted systematically in three fast spectra with different fuel compositions on the Comet critical assembly of the National Criticality Experiments Research Center. Previous experiments in a high-enriched uranium (HEU)/Pb and a low-enriched uranium (LEU)/Pb systems had been performed in 2016 and 2017, respectively. A follow-on experiment in a plutonium (Pu)/Pb system has been completed. The Pu/Pb system was constructed using lead plates and weapons grade plutonium plates that had been used in the Zero Power Physics Reactor (ZPPR) of Argonne National Laboratory until the 1990s. Furthermore, the HEU/Pb system was re-examined on the Comet critical assembly installed newly with a device that can guarantee the gap reproducibility with a higher accuracy and precision, and then the experimental data was re evaluated. Using the lead void reactivity worth measured in these three cores with different fuel compositions, the latest nuclear data libraries, JENDL 4.0 and ENDF/B VIII.0, were tested with the Monte Carlo calculation code MCNP version 6.1. As a result, the calculations by ENDF/B-VIII.0 were confirmed to agree with lead void reactivity worth measured in all the cores. It was furthermore found that the calculations by JENDL 4.0 overestimate by more than 20% for the Pu/Pb core while being in good agreements for the HEU/Pb and LEU/Pb cores.
Marufuji, Takato; Sato, Takumi; Ito, Hideaki; Suzuki, Hisashi; Fujishima, Tadatsune; Nakano, Tomoyuki
JAEA-Technology 2019-006, 22 Pages, 2019/05
JAEA-Technology-2019-006.pdf:2.84MB
Radioactive contamination incident occurred at Plutonium Fuel Research Facility (PFRF) in Oarai Research and Development Institute, Japan Atomic Energy Agency on June 6, 2017. During inspection work of storage container containing nuclear fuel materials, the PVC bag packaging in the storage container ruptured when a worker opened the lid in the hood, and a part of contents was spattered over the room. The cause of the increase of internal pressure of the storage container was gas generation by alpha radiolysis of the epoxy resin mixed with nuclear fuel materials. Opening inspection of about 70 similar containers stored in PFRF has been planned to confirm the condition of the contents and to stabilize the stored materials containing organic compounds. For safe and reliable open inspection of the storage containers with high internal pressure in the glove box, it is necessary to develop a pressure-resistant chamber in which the storage containers are opened and the contents are inspected under gastight condition. This report summarizes the concerns and countermeasures of the chamber design and the design results of the chamber.
Irisawa, Eriko; Yamamoto, Masahiro; Kato, Chiaki; Motooka, Takafumi; Ban, Yasutoshi
Journal of Nuclear Science and Technology, 56(4), p.337 - 344, 2019/04
Times Cited Count：1 Percentile：13.41(Nuclear Science & Technology)Takasaki, Koji; Yasumune, Takashi; Hashimoto, Makoto; Maeda, Koji; Kato, Masato; Yoshizawa, Michio; Momose, Takumaro
JAEA-Review 2019-003, 48 Pages, 2019/03
JAEA-Review-2019-003.pdf:3.81MB
June 6, 2017, at Plutonium Fuel Research Facility in Oarai Research and Development Center of JAEA, when five workers were inspecting storage containers containing plutonium and uranium, resin bags in a storage container ruptured, and radioactive dust spread. Though they were wearing a half face mask respirator, they inhaled radioactive materials. In the evaluation of the internal exposure dose, the aerodynamic radioactive median diameter (AMAD) is an important parameter. We measured 14 smear samples and a dust filter paper with imaging plates, and estimated the AMAD by image analysis. As a result of estimating the AMAD, from the 14 smear samples, the AMADs are 4.3 to 11 
m or more in the case of nitrate plutonium, and the AMADs are 5.6 to 14 m or more in the case of the oxidized plutonium. Also, from the dust filter paper, the AMAD is 3.0 m or more in the case of nitrate plutonium, and the AMAD is 3.9 m or more in the case of the oxidized plutonium.
Restoration Activity Team for the PFRF Contamination Incident
JAEA-Review 2019-001, 58 Pages, 2019/03
JAEA-Review-2019-001.pdf:10.74MB
The contamination accident occurred in a laboratory room (Room No.108) of Plutonium Fuel Research Facility (PFRF) in Japan Atomic Energy Agency (JAEA), Oarai Research and Development Institute on June 6, 2017. The polyvinyl chloride (PVC) bags burst just after the lid of one storage container was opened during the inspection of storage containers for U and Pu in the ventilation hood. At that time, part of nuclear materials in the storage container were scattered all over the room. Five workers in the room were subjected to plutonium contamination, which resulted in internal exposure. In order to restore the Room No.108 of PFRF, the Restoration Activity Team organized in JAEA carried out the decontamination work after the investigation of the contamination level in the room. The team decontaminated the surface of walls, ceiling, gloveboxes and other experimental instruments. Depending on the contamination distribution and installation state of the instruments, suitable decontamination methods were selected. In addition to the manual wiping using wet clothes, the exfoliation method using a strippable paint was applied for constricted areas. As a result, the loose alpha-contamination level fell below the detection limit throughout the room. On the other hand, the fixed contamination was covered with plastic sheets after the decontamination by a strippable paint. We hope that the restoration activity described in this report will provide useful information for the management of decommissioning facilities, especially for facilities treating alpha-radioactive materials such as plutonium.
Goto, Minoru; Aihara, Jun; Inaba, Yoshitomo; Ueta, Shohei; Fukaya, Yuji; Okamoto, Koji*
Proceedings of 9th International Topical Meeting on High Temperature Reactor Technology (HTR 2018) (USB Flash Drive), 6 Pages, 2018/10
JAEA has conducted design studies of a Pu-burner HTGR. The Pu-burner HTGR incinerates Pu by fission, and hence a high burn-up is required for the efficient incineration. In the fuel design, a thin ZrC layer, which acts as an oxygen getter and suppresses the internal pressure, was coated on the fuel kernel to prevent the CFP failure at the high burn-up. A stress analysis of the SiC layer, which acts as a pressure vessel for the CFP, was performed for with consideration of the depression effect due to the ZrC layer. As a result, the CFP failure fraction at high burn-up of 500 GWd/t satisfied the target value. In the reactor core design, an axial fuel shuffling was employed to attain the high burn-up, and the nuclear burn-up calculations with the whole core model and the fuel temperature calculations were performed. As a result, the nuclear characteristics, which are the shutdown margin and the temperature coefficient of reactivity, and the fuel temperature satisfied their target values.
-ray pipe-monitoring capabilities for real-time process monitoring safeguards applications in reprocessing facilitiesRodriguez, D.; Tanigawa, Masafumi; Nishimura, Kazuaki; Mukai, Yasunobu; Nakamura, Hironobu; Kurita, Tsutomu; Takamine, Jun; Suzuki, Satoshi*; Sekine, Megumi; Rossi, F.; et al.
Journal of Nuclear Science and Technology, 55(7), p.792 - 804, 2018/07
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)Nuclear material in reprocessing facilities is safeguarded by random sample verification with additional continuous monitoring applied to solution masses and volume in important tanks to maintain continuity-of-knowledge of process operation. Measuring the unique rays of each solution as the material flows through pipes connecting all tanks and process apparatuses could potentially improve process monitoring by verifying the compositions in real time. We tested this ray pipe-monitoring method using plutonium-nitrate solution transferred between tanks at the PCDF-TRP. The rays were measured using a lanthanum-bromide detector with a list-mode data acquisition system to obtain both time and energy of -ray. The analysis and results of this measurement demonstrate an ability to determine isotopic composition, process timing, flow rate, and volume of solution flowing through pipes, introducing a viable capability for process monitoring safeguards verification.
Goto, Minoru; Ueta, Shohei; Aihara, Jun; Inaba, Yoshitomo; Fukaya, Yuji; Tachibana, Yukio; Okamoto, Koji*
Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 6 Pages, 2017/07
A PuO-YSZ fuel kernel with a ZrC coating, which enhances safety, security and safeguard, namely: 3S-TRISO fuel, was proposed to introduce to the plutonium-burner HTGR. In this study, the efficiency of the ZrC coating as the free-oxygen getter was examined based on a thermochemical calculation. A preliminary study on the feasibility of the 3S-TRISO fuel was conducted focusing on the internal pressure. Additionally, a nuclear feasibility of the reactor core was studied. As a result, all the amount of the free-oxygen is captured by a thin ZrC coating under 1600
C and coating ZrC on the fuel kernel should be very effective method to suppress the internal pressure. The internal pressure of the 3S-TRISO fuel at 500 GWd/t is lower than that of UO kernel TRISO fuel whose feasibility had been already confirmed and the 3S-TRISO fuel should be feasible. The fuel shuffling allows to achieve 500 GWd/t. The temperature coefficient of reactivity is negative during the operation period and thus the nuclear feasibility of the reactor core should be achievable.
Mukai, Yasunobu; Nakamichi, Hideo; Kobayashi, Daisuke; Nishimura, Kazuaki; Fujisaku, Sakae; Tanaka, Hideki; Isomae, Hidemi; Nakamura, Hironobu; Kurita, Tsutomu; Iida, Masayoshi*; et al.
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 8 Pages, 2017/04
TRP has stored the plutonium in solution state for long-term since the last PCDF operation in 2007 was finished. After the great east Japan earthquake in 2011, JAEA had investigated the risk against potential hazard of these solutions which might lead to make hydrogen explosion and/or boiling of the solution accidents with the release of radioactive materials to the public when blackout. To reduce the risk for storing Pu solution (about 640 kg Pu), JAEA planned to perform the process operation for the solidification and stabilization of the solution by converted into MOX powder at PCDF in 2013. In order to perform PCDF operation without adaption of new safety regulation, JAEA conducted several safety measures such as emergency safety countermeasures, necessary security and safeguards (3S) measures with understanding of NRA. As a result, the PCDF operation had stared on 28th April, 2014, and successfully completed to convert MOX powder on 3rd August, 2016 for about 2 years as planned.
Kobayashi, Fuyumi; Sumiya, Masato; Kida, Takashi; Kokusen, Junya; Uchida, Shoji; Kaminaga, Jota; Oki, Keiichi; Fukaya, Hiroyuki; Sono, Hiroki
JAEA-Technology 2016-025, 42 Pages, 2016/11
JAEA-Technology-2016-025.pdf:17.88MB
A preliminary test on MOX fuel dissolution for the STACY critical experiments had been conducted in 2000 through 2003 at Nuclear Science Research Institute of JAEA. Accordingly, the uranyl / plutonium nitrate solution should be reconverted into oxide powder to store the fuel for a long period. For this storage, the moisture content in the oxide powder should be controlled from the viewpoint of criticality safety. The stabilization of uranium / plutonium solution was carried out under a precipitation process using ammonia or oxalic acid solution, and a calcination process using a sintering furnace. As a result of the stabilization operation, recovery rate was 95.6% for uranium and 95.0% for plutonium. Further, the recovered oxide powder was calcined again in nitrogen atmosphere and sealed immediately with a plastic bag to keep its moisture content low and to prevent from reabsorbing atmospheric moisture.
Tanaka, Kosuke; Sato, Isamu; Hirosawa, Takashi; Kurosaki, Ken*; Muta, Hiroaki*; Yamanaka, Shinsuke*
Journal of Nuclear Science and Technology, 52(10), p.1285 - 1289, 2015/10
Times Cited Count：2 Percentile：18.84(Nuclear Science & Technology)Polycrystalline specimens of americium-containing barium plutonate have been prepared by mixing the appropriate amounts of (Pu
Am
)O and BaCO powders followed by reacting and sintering at 1600 K under the flowing gas atmosphere of dry-air. The sintered specimens had a single phase of orthorhombic perovskite structure and were crack-free. The elastic moduli were determined from the longitudinal and shear sound velocities. The Debye temperature was also determined from the sound velocities and lattice parameter measurements. The thermal conductivity was calculated from the measured density at room temperature, literature values of heat capacity, and thermal diffusivity measured by laser flash method in vacuum. The thermal conductivity of americium-containing barium plutonate was roughly independent of the temperature and was almost the same magnitude as that of BaPuO and BaUO.
Goto, Minoru; Demachi, Kazuyuki*; Ueta, Shohei; Nakano, Masaaki*; Honda, Masaki*; Tachibana, Yukio; Inaba, Yoshitomo; Aihara, Jun; Fukaya, Yuji; Tsuji, Nobumasa*; et al.
Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.507 - 513, 2015/09
A concept of a plutonium burner HTGR named as Clean Burn, which has a high nuclear proliferation resistance, had been proposed by Japan Atomic Energy Agency. In addition to the high nuclear proliferation resistance, in order to enhance the safety, we propose to introduce PuO-YSZ TRISO fuel with ZrC coating to the Clean Burn. In this study, we conduct fabrication tests aiming to establish the basic technologies for fabrication of PuO-YSZ TRISO fuel with ZrC coating. Additionally, we conduct a quantitative evaluation of the security for the safety, a design of the fuel and the reactor core, and a safety evaluation for the Clean Burn to confirm the feasibility. This study is conducted by The University of Tokyo, Japan Atomic Energy Agency, Fuji Electric Co., Ltd., and Nuclear Fuel Industries, Ltd. It was started in FY2014 and will be completed in FY2017, and the first year of the implementation was on schedule.
Hosoma, Takashi
JAEA-Research 2015-009, 162 Pages, 2015/08
JAEA-Research-2015-009.pdf:22.3MB
Neutron coincidence counting assay systems have been developed in the last two decades. Objects would extend to high-mass uranium-plutonium dioxide containing other spontaneous fission nuclei, so essentials of neutron multiplicity counting were reconsidered and expanded: (a) Formulae of multiplicity distribution were algebraically derived up to septuplet using a probability generating function; (b) Leakage multiplication was evaluated not by Monte Carlo method but by an average length from an arbitrary point inside a sample to an arbitrary point on its surface and a probability of induced fission within the length; (c) Mechanism of coincidence counting was associated with a couple of different time axes in Poisson process, and consequently a pair of close-to-coincident neutrons from the process was derived. For the formulae, new expressions using combination were wrote down. For spectrum and mean free path, actually treated uranium-plutonium dioxide was selected as an example.
Seya, Michio; Kureta, Masatoshi; Soyama, Kazuhiko; Nakamura, Hironobu; Harada, Hideo; Hajima, Ryoichi
Proceedings of INMM 55th Annual Meeting (Internet), 10 Pages, 2014/07
JAEA has been implementing development programs of basic technologies of the following advanced NDA (non-destructive assay) of nuclear material (NM) for nuclear safeguards and security. (1) Alternative to 
He neutron detection using ZnS/BO ceramic scintillator, (2) NRD (neutron resonance densitometry) using NRTA (neutron resonance transmission analysis) and NRCA (neutron resonance capture analysis), (3) NRF (nuclear resonance fluorescence)-NDA using laser Compton scattered (LCS) -rays (intense mono-energetic -rays). The development program (1) is for NDA systems that use ZnS/BO ceramic scintillator as alternative neutron detector to He for coming shortage of its supply. The program (2) is for a NDA system of isotopic composition measurement (non-destructive mass spectroscopy) in targets such as particle-like melted fuel debris using NRTA and NRCA. The program (3) is for NDA systems using a specific NRF reaction of certain Pu/U isotope caused by mono-energetic LCS -ray with energy tuned to the specific excited state of the isotope. This paper introduces above three programs.
