Thermal-neutron capture cross-section measurements of neptunium-237 with graphite thermal column in KUR

Nakamura, Shoji; Shibahara, Yuji*; Endo, Shunsuke; Kimura, Atsushi

Journal of Nuclear Science and Technology, 59(11), p.1388 - 1398, 2022/11

https://doi.org/10.1080/00223131.2022.2058639

The present study selected Np among radioactive nuclides and aimed to measure the thermal-neutron capture cross-section for Np in a well-thermalized neutron field by an activation method. A Np standard solution was used for irradiation samples. A thermal-neutron flux at an irradiation position was measured with neutron flux monitors: Sc, Co, Mo, Ta and Au. The Np sample and flux monitors were irradiated together for 30 minutes in the graphite thermal column equipped with the Kyoto University Research Reactor. The similar irradiation was carried out twice. After the irradiations, the Np samples were quantified using 312-keV gamma ray emitted from Pa in a radiation equilibrium with Np. The reaction rates of Np were obtained from gamma-ray peak net counts given by Np, and then the thermal-neutron capture cross-section of Np was found to be 173.84.4 barn by averaging the results obtained by the two irradiations. The present result was in agreement with the reported data given by a time-of-flight method within the limit of uncertainty.

Development of an integrated computer code system for analyzing irradiation behaviors of a fast reactor fuel

Uwaba, Tomoyuki; Nemoto, Junichi*; Ito, Masahiro*; Ishitani, Ikuo*; Doda, Norihiro; Tanaka, Masaaki; Otsuka, Satoshi

Nuclear Technology, 207(8), p.1280 - 1289, 2021/08

https://doi.org/10.1080/00295450.2020.1810977

Computer codes for irradiation behavior analysis of a fuel pin and a fuel pin bundle and for coolant thermal hydraulics analysis were coupled into an integrated code system. In the system, each code provides data required by other codes and the analyzed results are shared among them. The system allows for the synthesizing of analyses of thermal, chemical and mechanical behaviors in a fuel subassembly under irradiation. A test analysis was made for a fuel subassembly containing a mixed oxide fuel pin bundle irradiated in a fast reactor. The results of the analysis were presented with transverse cross-sectional images of the fuel subassembly and three-dimensional images of a fuel pin and fuel pin bundle models. For detailed evaluation, various irradiation behaviors of all fuel pins in the subassembly were analyzed and correlated with irradiation conditions.

Establishment of reasonable 2-D model to investigate heat transfer and flow characteristics by using scale model of vessel cooling system for HTTR

Takada, Shoji; Ngarayana, I. W.*; Nakatsuru, Yukihiro*; Terada, Atsuhiko; Murakami, Kenta*; Sawa, Kazuhiro*

Mechanical Engineering Journal (Internet), 7(3), p.19-00536_1 - 19-00536_12, 2020/06

https://doi.org/10.1299/mej.19-00536

In this study reasonable 2D model was established by using FLUENT for start-up of analysis and evaluation of heat transfer flow characteristics in 1/6 scale model of VCS for HTTR. By setting up pressure vessel temperature around 200C about relatively high ratio of heat transfer via natural convection in total heat removal around 20-30%, which is useful for code to experiment benchmark in the aspect to confirm accuracy to predict temperature distribution of components which is heated up by natural convection flow. The numerical results of upper head of pressure vessel by the --SST intermittency transition model, which can adequately reproduce the separation, re-adhesion and transition, reproduced the test results including temperature distribution well in contrast to those by the - model in both cases that helium gas is evacuated or filled in the pressure vessel. It was emerged that any local hot spot did not appear on the top of upper head of pressure vessel where natural convection flow of air is separated in both cases. In addition, the plume of high temperature helium gas generated by the heating of heater was well mixed in the upper head and uniformly heated the inner surface of upper head without generating hot spots.

Development of gel filler that facilitates fuel debris retrieval (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; Osaka University*

JAEA-Review 2019-029, 36 Pages, 2020/02

JAEA-Review-2019-029.pdf:2.33MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of Gel Filler that Facilitates Fuel Debris Retrieval". When gel materials such as polymer, silicate and clay minerals with adjusted viscosity are used in the process of debris retrieval, the gel would not leak down from the damaged parts, resulting in the reduction of surrounding air dose rate. In addition, gel materials can reduce the diffusion and scattering of dust that is produced by cutting. For these reasons, we propose a method where inside of a containment vessel is filled by gel materials in order to simplify the debris retrieval.

Comparative study of oxidation on Cu and CuAu surfaces with a hyperthermal O molecular beam

Okada, Michio*; Moritani, Kosuke; Fukuyama, Tetsuya*; Mizutani, Hironori*; Yoshigoe, Akitaka; Teraoka, Yuden; Kasai, Toshio*

Surface Science, 600(18), p.4228 - 4232, 2006/09

https://doi.org/10.1016/j.susc.2006.01.149

Dissociative adsorption of hyperthermal O molecules on CuAu(100) was investigated by X-ray photoemission spectroscopy in conjunction with a synchrotron light source. Comparing the O-uptake curve on CuAu with that on Cu, it was found that the dissociative adsorption of O is more activated (less reactive) due to Au alloying. The low-energy electron-diffraction (LEED) pattern of c(22) for the clean surface turned into the (11) LEED pattern during the oxidation by hyperthermal O molecular beam, suggesting that the O adsorption induces the Cu-atom segregation on the surface.

An Irradiation test of heat-resistant ceramic composite materials, 2; Interim report on post-irradiation examinations of the second and third preliminary test, 98M-41A, 99M-30A

Baba, Shinichi; Nemoto, Makoto*; Sozawa, Shizuo; Yamaji, Masatoshi*; Ishihara, Masahiro; Sawa, Kazuhiro

JAERI-Tech 2005-055, 157 Pages, 2005/09

JAERI-Tech-2005-055.pdf:19.06MB

The Japan Atomic Energy Research Institute (JAERI) has been carrying out the research on radiation damage mechanism of heat-resistant ceramics composite materials, as one of the subjects of the innovative basic research on high temperature engineering using the High Temperature Engineering Test Reactor (HTTR). A series of preliminary irradiation tests is being made using the Japan Materials Testing Reactor (JMTR). The present report describes results of post-irradiation examinations so far on specimens irradiated in the second and third capsule, designated 98M-41A and 99M-30A, to fast neutron fluences of 1.010m(E1MeV) at temperatures of 973K-1173K and 1273K-1473K. The PIE were conducted as the fundamental statistics index of the diametral dimensions for irradiated specimen, irradiation induced dimensional change rate and thermal expansion rate.

Failure probability analysis on mercury target vessel

Ishikura, Shuichi*; Shiga, Akio*; Futakawa, Masatoshi; Kogawa, Hiroyuki; Sato, Hiroshi; Haga, Katsuhiro; Ikeda, Yujiro

JAERI-Tech 2005-026, 65 Pages, 2005/03

JAERI-Tech-2005-026.pdf:2.86MB

Failure probability analysis was carried out to estimate the lifetime of the mercury target which will be installed into the JSNS (Japan spallation neutron source) in J-PARC (Japan Proton Accelerator Research Complex). The lifetime was estimated as taking loading condition and materials degradation into account. Considered loads imposed on the target vessel were the static stresses due to thermal expansion and static pre-pressure on He-gas and mercury and the dynamic stresses due to the thermally shocked pressure waves generated repeatedly at 25 Hz. Materials used in target vessel will be degraded by the fatigue, neutron and proton irradiation, mercury immersion and pitting damages, etc. The imposed stresses were evaluated through static and dynamic structural analyses. The material-degradations were deduced based on published experimental data. As results, it was quantitatively confirmed that the failure probability for the lifetime expected in the design is very much lower, 10 in the safety hull, meaning that it will be hardly failed during the design lifetime. On the other hand, the beam window of mercury vessel suffered with high-pressure waves exhibits the failure probability of 12%. It was concluded, therefore, that the leaked mercury from the failed area at the beam window is adequately kept in the space between the safety hull and the mercury vessel to detect mercury-leakage sensors.

Review of JAERI activities on the IFMIF liquid lithium target in FY2004

Nakamura, Hiroo; Ida, Mizuho*; Matsuhiro, Kenjiro; Fischer, U.*; Hayashi, Takumi; Mori, Seiji*; Nakamura, Hirofumi; Nishitani, Takeo; Shimizu, Katsusuke*; Simakov, S.*; et al.

JAERI-Review 2005-005, 40 Pages, 2005/03

JAERI-Review-2005-005.pdf:3.52MB

The International Fusion Materials Irradiation Facility (IFMIF) is being jointly planned to provide an accelerator-based Deuterium-Lithium (Li) neutron source to produce intense high energy neutrons (2 MW/m) up to 200 dpa and a sufficient irradiation volume (500 cm) for testing the candidate materials and components up to about a full lifetime of their anticipated use in ITER and DEMO. To realize such a condition, 40 MeV deuteron beam with a current of 250 mA is injected into high speed liquid Li flow with a speed of 20 m/s. In target system, radioactive species such as 7Be, tritium and activated corrosion products are generated. In addition, back wall operates under severe conditions of neutron irradiation damage (about 50 dpa/y). In this paper, the thermal and thermal stress analyses, the accessibility evaluation of the IFMIF Li loop, and the tritium inventory and permeation of the IFMIF Li loop are summarized as JAERI activities on the IFMIF target system performed in FY2004.

Preliminary investigation of annealing effect on thermal conductivity of graphite and investigation of annealing test method (Contract research)

Sumita, Junya; Nakano, Masaaki*; Tsuji, Nobumasa*; Shibata, Taiju; Ishihara, Masahiro

JAERI-Tech 2004-055, 25 Pages, 2004/08

JAERI-Tech-2004-055.pdf:4.25MB

Neutron irradiation remarkably reduces the thermal conductivity of graphite, and the reduced thermal conductivity is recovered by annealing effect if the graphite is heated above the irradiation temperature. Therefore, it is expected that the reduced thermal conductivity of graphite components in the HTGR could be recovered by the annealing effect in accidents, such as a depressurization accident. Then, an analytical investigation of the annealing effect on thermal performance of a HTGR core was carried. The analysis showed that the annealing effect reduces the maximum fuel temperature about 70C, and it is important to introduce the annealing effect appropriately in the temperature analysis of the core components and reactor internals. In addition, an annealing test method was investigated to evaluate the effect quantitatively, and the test plan was made.

Reproducibility of thermal neutron flux distribution on patient's brain surface with a realistic phantom

Yamamoto, Kazuyoshi; Kumada, Hiroaki; Yamamoto, Tetsuya*; Matsumura, Akira*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(2), p.193 - 199, 2004/06

https://doi.org/10.3327/taesj2002.3.193

To investigate the possibility of experimental approach for dose evaluation using a realistic phantom that faithfully reproduced the shape of a head, this research considered the manufacture of a patient's realistic phantom and the reappearance of actual medical irradiation conditions. We selected the rapid prototyping technology to produce the realistic phantom from the Computed Tomography (CT) imaging. This phantom was irradiated under the same clinical irradiation condition of this patient, and the thermal neutron distribution on the brain surface was measured in detail. Several subjects on material and data conversion in the production of realistic phantom were mentioned. As a result of reproducing medical irradiation using the realistic phantom, the maximum thermal neutron flux became a value about 22% lower than the surface of the actual brain. If the problems pointed out in this paper are solved, it may also be expected that it would become possible to check computational dosimetry system.