Accident consequence analysis for JMTR as a decommission facilities

Nagata, Hiroshi; Omori, Takazumi; Maeda, Eita; Otsuka, Kaoru; Nakano, Hiroko; Hanakawa, Hiroki; Ide, Hiroshi

JAEA-Review 2023-033, 40 Pages, 2024/01

JAEA-Review-2023-033.pdf:1.39MB

Japan Materials Testing Reactor (JMTR) was decided as a one of decommission facilities in April 2017. In order to submit the decommissioning plan to the Nuclear Regulation Authority, the type of accident assumed in the first stage of the decommissioning plan was selected, and the public exposure dose was evaluated. A fuel handling accident and a fire accident during storage of waste were selected as assumed accidents in the first stage of the decommissioning plan. An evaluation of the public exposure dose from the radioactive materials released into the atmosphere due to these accidents was estimated to be a maximum of 0.019 mSv (due to a fire accident during storage of waste). This estimated value was found to be sufficiently smaller than the judging criteria (5 mSv), and not to pose a significant risk of radiation exposure to the general public.

Sodium-cooled Fast Reactors

Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

https://shop.elsevier.com/books/sodium-cooled-fast-reactors/morishita/978-0-12-824076-2

This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.

scattering length from photoproduction on the proton near the reaction threshold

Ishikawa, Takatsugu*; Fujimura, Hisako*; Fukasawa, Hiroshi*; Hashimoto, Ryo*; He, Q.*; Honda, Yuki*; Hosaka, Atsushi; Iwata, Takahiro*; Kaida, Shun*; Kasagi, Jirota*; et al.

Physical Review C, 101(5), p.052201_1 - 052201_6, 2020/05

https://doi.org/10.1103/PhysRevC.101.052201

Enhancement of element production by incomplete fusion reaction with weakly bound deuteron

Wang, H.*; Otsu, Hideaki*; Chiga, Nobuyuki*; Kawase, Shoichiro*; Takeuchi, Satoshi*; Sumikama, Toshiyuki*; Koyama, Shumpei*; Sakurai, Hiroyoshi*; Watanabe, Yukinobu*; Nakayama, Shinsuke; et al.

Communications Physics (Internet), 2(1), p.78_1 - 78_6, 2019/07

https://doi.org/10.1038/s42005-019-0165-1

Searching for effective pathways for the production of proton- and neutron-rich isotopes through an optimal combination of reaction mechanism and energy is one of the main driving forces behind experimental and theoretical nuclear reaction studies as well as for practical applications in nuclear transmutation of radioactive waste. We report on a study on incomplete fusion induced by deuteron, which contains one proton and one neutron with a weak binding energy and is easily broken up. This reaction study was achieved by measuring directly the cross sections for both proton and deuteron for Pd at 50 MeV/u via inverse kinematics technique. The results provide direct experimental evidence for the onset of a cross-section enhancement at high energy, indicating the potential of incomplete fusion induced by loosely-bound nuclei for creating proton-rich isotopes and nuclear transmutation of radioactive waste.

A Simple method to create gamma-ray-source spectrum for passive gamma technique

Shiba, Tomooki; Maeda, Shigetaka; Sagara, Hiroshi*; Ishimi, Akihiro; Tomikawa, Hirofumi

Energy Procedia, 131, p.250 - 257, 2017/12

https://doi.org/10.1016/j.egypro.2017.09.446

In the present paper, the ray source data was developed for the debris composition based on "best estimates", and the subsequent photon transportation calculation was performed to evaluate the leakage ray spectra according to the fuel debris. Since the creation of the line spectrum source requires a great deal, we have developed the relatively simple but accurate enough method to build up ray source, coupling of baseline spectra evaluated by ORIGEN2 code and several line spectra of interest. One of the advantages of the method is taking bremsstrahlung X rays into consideration by utilizing the bremsstrahlung libraries of ORIGEN2. The new ray source was used to calculate the detector response of HPGe detector and the results was compared as a benchmark with experimental measurement results of irradiated fuel pins. As the result, the simulated ray spectrum shape agreed well with the shape of ray spectrum obtained by the experiment.

R&D of active neutron NDA techniques for nuclear nonproliferation and nuclear security, 3; Validation of neutron transport code for design of NDA system

Maeda, Makoto; Komeda, Masao; Tobita, Hiroshi; Ozu, Akira; Kureta, Masatoshi; Bogucarska, T.*; Crochemore, J. M.*; Varasano, G.*; Pedersen, B.*

Dai-37-Kai Kaku Busshitsu Kanri Gakkai Nihon Shibu Nenji Taikai Rombunshu (CD-ROM), 7 Pages, 2017/02

JAEA and EC/JRC are carrying out collaborative research to develop NDA techniques that can be utilized for quantification of high radioactive special nuclear materials such as spent fuel and next generation minor actinide fuels. In the research, reliability of neutron transport codes is important because it is utilized for design and development of a demonstration system of next-generation Differential Die-away (DDA) technique in JAEA. In order to evaluate the reliability, actual neutron flux distribution in a sample cavity was examined in PUNITA device using JRC type DDA technique and JAWAS-T device using JAEA type DDA technique, and then the measurement results were compared with the simulation results obtained by the neutron transport codes. The neutron flux distribution in the target matrix was also examined in the PUNITA and compared with the simulation results. We report on the measurement and simulation results of the neutron flux distribution and evaluation results of the reliability of the neutron transport codes.

Evaluation of neutron flux distribution in the JAEA type and JRC type DDA systems

Maeda, Makoto; Komeda, Masao; Tobita, Hiroshi; Ozu, Akira; Kureta, Masatoshi; Bogucarska, T.*; Crochemore, J. M.*; Varasano, G.*; Pedersen, B.*

Proceedings of INMM 57th Annual Meeting (Internet), 9 Pages, 2016/07

The JAEA and EC/JRC have started collaborative research to develop a technique that can be utilized for quantification of high radioactive special nuclear materials such as next generation minor actinide fuels. In the study of a Differential Die-Away (DDA) technique, which is one of the techniques to be improved in the collaborative research, JRC type and JAEA type DDA techniques are compared. In the JRC type DDA technique, large amount of thermal neutron is generated using D-T neutron generator and graphite moderator to accomplish high detection sensitivity for small amount of fissile material. On the other hand, in JAEA type, relatively hard neutron spectrum and moderation of neutron in the target matrix are utilized to minimize position dependence of detection efficiency. Estimation of the neutron field is important to evaluate the performance of the system in DDA technique. The purpose of this study is to validate simulation results by experimental results and evaluate neutron flux distribution in the system by the simulation and the experiment. In this paper, we present the evaluation results of the neutron flux distributions in PUNITA which utilizes JRC type DDA technique and JAWAS-T which utilizes JAEA type DDA technique obtained by Monte Carlo simulation and activation method.

Applicability evaluation of candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station; Active neutron technique (Interim report)

Komeda, Masao; Maeda, Makoto; Furutaka, Kazuyoshi; Tobita, Hiroshi; Hattori, Kentaro; Shimofusa, Taichi; Ozu, Akira; Kureta, Masatoshi

Proceedings of INMM 57th Annual Meeting (Internet), 10 Pages, 2016/07

We are working on the development of a non-destructive assay (NDA) measurement system using the Fast Neutron Direct Interrogation (FNDI) method. The FNDI method is a kind of active neutron technique and can measure the total amounts of fissile materials (U-235, Pu-239, Pu-241). We have already carried out design analyses of an NDA measurement system for measuring the debris assuming use of the Three Mile Island (TMI) canister model. The result was presented at the Institute of Nuclear Materials Management (INMM) 56th Annual Meeting. Since then, we have modified the design of the NDA measurement system for the fuel debris and canister models at 1F. In this paper, we provide the calculation and evaluation results using the modified NDA measurement system. Moreover, we provide analytical investigations of the influence of fuel debris including high fissile material content on measurements.

Validation of decay heat evaluation method based on FPGS cord for fast reactor spent MOX fuels

Usami, Shin; Kishimoto, Yasufumi; Taninaka, Hiroshi; Maeda, Shigetaka

Proceedings of International Conference on the Physics of Reactors; Unifying Theory and Experiments in the 21st Century (PHYSOR 2016) (USB Flash Drive), p.3263 - 3274, 2016/05

The present paper describes the validation of the new decay heat evaluation method using FPGS90 code with both the updated nuclear data library and the rational extent of uncertainty, by comparing the results of the decay heat measurement of the spent fuel subassemblies in Joyo MK-II core and by comparing with the calculation results of ORIGEN2.2 code. The calculated values of decay heat (C) by FPGS90 based on the JENDL-4.0 library were coincident with the measured ones (E) within the calculation uncertainties, and the C/E ranged from 1.01 to 0.93. FPGS90 evaluated the decay heat almost 3% larger than ORIGEN2.2, and it improved the C/E in comparison with the ORIGEN2.2 code. Furthermore, The C/E by FPGS90 based on the JENDL-4.0 library was improved than that based on the JENDL-3.2 library, and the contribution of the revision of reaction cross section library to the improvement was dominant rather than that of the decay data and fission yield data libraries.

Study on nondestructive measurement of nuclear materials in fuel debris by using fast neutron direct interrogation method

Maeda, Makoto; Furutaka, Kazuyoshi; Kureta, Masatoshi; Ozu, Akira; Tobita, Hiroshi; Komeda, Masao; Hattori, Kentaro

Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-36-Kai Nenji Taikai Rombunshu (Internet), 9 Pages, 2015/12

Fukushima Daiichi Nuclear Disaster in March 11th in 2011 is considered to produce fuel debris. It is difficult to measure nondestructively the amount of fissile materials in the fuel debris since the constituents of the debris are unknown and it may contain various materials such as water, metal, and even neutron absorber. A fast neutron direct interrogation (FNDI) method, which has been developed for long years to measure uranium bearing wastes drums, can measure an amount of nuclear materials regardless of a matrix of the wastes drums. We have studied nondestructive assay for nuclear materials in fuel debris by using the FNDI method. In this paper, we report on a design study of a nondestructive measurement system for debris canister and results of the investigation on the applicability of the FNDI method to the fuel debris containing various materials using Monte Carlo simulations.