Extension of fuel performance code package FEMAXI; Development and validation of reactivity-initiated accident analysis module RANNS for light water reactor fuels

Tasaki, Yudai; Udagawa, Yutaka

JAEA-Data/Code 2024-012, 76 Pages, 2024/12

JAEA-Data-Code-2024-012.pdf:9.25MB

Japan Atomic Energy Agency (JAEA) has been developing a fuel performance code, FEMAXI, to evaluate the behavior of LWR fuels under normal operation and transient conditions. In March 2019, FEMAXI-8, the first systematically validated and performance evaluated code, was released. Since then, the code has undergone various improvements. In parallel, since the 2000s, JAEA has been developing the RANNS module as a branch for design basis accident (DBA) analysis, with a particular emphasis on computational stability, so that fuel behavior can be tracked even for very steep transients, in this case mainly reactivity-initiated accidents (RIAs). The specific models include boiling heat transfer, fission gas release by grain boundary failure, and cladding failure determination based on fracture mechanics parameters, which are essential for predicting such transient behavior. In this report, prior to the release of RANNS, we present a description of the models for accident behavior analysis, the relationship with FEMAXI-8 in terms of the design and structure of the program, and the results of a large-scale validation using the extensive database of RIA experiments conducted and accumulated by JAEA, to evaluate the overall RIA analysis performance. The code will be made available to users as a packaged FEMAXI/RANNS, enabling them to analyze fuel behavior under various conditions. The model parameter sets determined through the above validation analyses are also presented in this report, and by referring to them, the analysis can be easily performed with almost no change in usability from the previously released FEMAXI-8.

Bayesian statistical model for cladding high-temperature burst under loss-of-coolant accident conditions

Tasaki, Yudai; Narukawa, Takafumi; Udagawa, Yutaka

Journal of Nuclear Science and Technology, 61(10), p.1349 - 1359, 2024/10

https://doi.org/10.1080/00223131.2024.2321342

Double diffusive dissolution model of UO pellet in molten Zr cladding

Ito, Ayumi*; Yamashita, Susumu; Tasaki, Yudai; Kakiuchi, Kazuo; Kobayashi, Yoshinao*

Journal of Nuclear Science and Technology, 60(4), p.450 - 459, 2023/04

https://doi.org/10.1080/00223131.2022.2114956

Improvement of intragranular fission gas behavior model for fuel performance code FEMAXI-8

Udagawa, Yutaka; Tasaki, Yudai

JAEA-Data/Code 2021-007, 56 Pages, 2021/07

JAEA-Data-Code-2021-007.pdf:5.05MB

Japan Atomic Energy Agency (JAEA) has released FEMAXI-8 in 2019 as the latest version of the fuel performance code FEMAXI, which has been developed to analyze thermal and mechanical behaviors of a single fuel rod in mainly normal operation conditions and anticipated transient conditions. This report summarizes a newly developed model to analyze intragranular fission gas behaviors considering size distribution of gas bubbles and their dynamics. While the intragranular fission gas behavior models implemented in the previous FEMAXI versions have supported only treating single bubble size for a given fuel element, the new model supports multiple gas groups according to their size and treats their dynamic behaviors, making the code more versatile. The model was first implemented as a general module that takes arbitrary number of bubble groups and spatial mesh division for a given fuel grain system. An interface module to connect the model to FEMAXI-8 was then developed so that it works as a 2 bubble groups model, which is the minimum configuration of the multi-grouped model to be operated with FEMAXI-8 at the minimum calculation cost. FEMAXI-8 with the new intragranular model was subjected to a systematic validation calculation against 144 irradiation test cases and recommended values for model parameters were determined so that the code makes reasonable predictions in terms of fuel center temperature, fission gas release, etc. under steady-state and power ramp conditions.

Neutronic design of neutron moderator on a reentrant-hole configuration for Kyoto University Accelerator-based Neutron Source (KUANS)

Okita, Shoichiro; Tasaki, Seiji*; Abe, Yutaka*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 19(3), p.178 - 184, 2020/09

https://doi.org/10.3327/taesj.J19.028

The Kyoto University Accelerator-based Neutron Source (KUANS) is a compact neutron source that is mainly used for spectrometer and detector development. In addition, it is also suited for experiments to study the neutronic design of moderators owing to the relatively low neutron generation yield by Be(p,n). We present a neutronic design of the neutron moderator on a reentrant-hole configuration for KUANS to enhance the neutron emission, and some experiments are conducted at KUANS for verification. A polyethylene moderator on a reentrant-hole configuration is designed by PHITS calculation and is introduced to KUANS to obtain intense oblong neutron beams. The intensity of the pulsed neutron beam is experimentally measured. The results reveal that the intensity becomes approximately 1.9 times stronger than that of the conventional rectangular design. In addition, the ratio of its intensity to the conventional intensity increases to approximately threefold as the neutron wavelength increases. It is interesting to note that the longer the neutron wavelength, the more efficiently they are extracted from the inside of the moderator owing to the existence of the reentrant-hole configuration.

Introduction and implementation of physical protection measures including trustworthiness program at Tokai Reprocessing Facilities

Nakamura, Hironobu; Kimura, Takashi; Yamazaki, Katsuyuki; Kitao, Takahiko; Tasaki, Takashi; Iida, Toru

Proceedings of International Conference on Physical Protection of Nuclear Material and Nuclear Facilities (Internet), 9 Pages, 2018/09

After the accident of Fukushima Daiichi Nuclear Power Station, to develop effective security measures based on the lesson learned from such crisis and to meet the IAEA Nuclear Security Recommendations (INFCIRC/225/Rev.5), NRA in Japan made a partial amendment of the regulations concerning the reprocessing activity in 2012. The Tokai reprocessing facility implemented all of those security measures by the end of March 2014. Those new measures help us to keep high degree of security level and contributed to our planned operations to reduce the potential risk of the plant. On the other hand, the trustworthiness program was newly introduced in 2016, based on the trustworthiness policy determined by NRA. The implementing entity of the program is JAEA for the Tokai Reprocessing Facility and is required for both the persons afford unescorted access to Category I and II, CAS/SAS, and the persons afford access to the sensitive information. Those who are involved this program will be judged before engaging the work whether they might act as insider to cause or assist radiological sabotage or unauthorized removal of nuclear material, or leak sensitive information. The program is expected as a measure against insider at reprocessing facilities, and is expected to be enforced around the autumn of 2017. As well as the establishment of security measures, the promoting nuclear security culture for all employees was a big challenge. The Tokai reprocessing facility have introduced several security culture activities, such as case study education of security events done by a small group and putting up the security culture poster and so on. This paper presents introduction and implementation with effectiveness of security measures in the Tokai reprocessing facilities and the future security measures applied to the reprocessing facilities are discussed.

Report on activities related to fostering nuclear security culture in Tokai Reprocessing Facility

Kitao, Takahiko; Takeuchi, Yoshikatsu; Kimura, Takashi; Kojima, Junji; Shioya, Satoshi; Tasaki, Takashi; Nakamura, Hironobu

Nihon Kaku Busshitsu Kanri Gakkai Dai-38-Kai Nenji Taikai Rombunshu (Internet), 9 Pages, 2018/04

In order to ensure and strengthen nuclear security measures, an active cultivation of nuclear security culture implemented by both entire organization and individual persons is vitally essential. Tokai reprocessing facility has conducted various activities such as case study education and training, yearly posters and patrolling the site by upper-level management that all employees hold a deep rooted belief that there is a credible insider and outsider threat, and that nuclear security is important. These activities are conducted in order to establish the foundation of beliefs and attitudes of effective nuclear security culture based on the IAEA guideline. This report introduces our activities fostering nuclear security culture in Tokai reprocessing facility that the evaluation and the continuous improvement of bidirectional activities by both top-down from multiple management levels and bottom-up from individual employee, and our challenges need to be worked on for the future.

Report on the research through the U.S. DOE "The International Search and Consequence Management Workshop (ISCM-WS)"

Kawakami, Takeshi; Tasaki, Takashi

JAEA-Review 2011-028, 47 Pages, 2011/12

JAEA-Review-2011-028.pdf:3.25MB

The International Search and Consequence Management Workshop (ISCM-WS) that was organized by the U.S. Department of Energy (DOE) took place from May 17th to May 20th, 2010. The Aim of this Workshop is to build and enhance the global capacity to prevent and respond to nuclear and radiological emergencies, and it directly supports the aims of global initiative to combat nuclear terrorism. DOE brought together 92 officials from 26 countries and 3 officials from IAEA in this Workshop. DOE introduced two matters in USA, First is response against nuclear and radiological terrorisms and second is technology, systems, activity for consequence management. This review report summarized the observation in the ISCM-WS including activity of DOE/NNSA's Search Response Team and activity of consequence management.

Effect of ion beam irradiation for species

Kobayashi, Nobuo*; Sasaki, Shinichiro*; Tasaki, Keisuke*; Nakatsuka, Akira*; Nozawa, Shigeki; Hase, Yoshihiro; Narumi, Issei

JAEA-Review 2010-065, JAEA Takasaki Annual Report 2009, P. 67, 2011/01

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2010-065.pdf

Mutation induction in azalea seedlings using ion beam irradiation

Kobayashi, Nobuo*; Tasaki, Keisuke*; Kano, Sayaka*; Sakamoto, Sakiko*; Nakatsuka, Akira*; Hase, Yoshihiro; Narumi, Issei

JAEA-Review 2008-055, JAEA Takasaki Annual Report 2007, P. 70, 2008/11

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2008-055.pdf

no abstracts in English