Research and examination of seismic safety evaluation and function maintenance for important equipment in nuclear facilities

Furuya, Osamu*; Fujita, Satoshi*; Muta, Hitoshi*; Otori, Yasuki*; Itoi, Tatsuya*; Okamura, Shigeki*; Minagawa, Keisuke*; Nakamura, Izumi*; Fujimoto, Shigeru*; Otani, Akihito*; et al.

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 6 Pages, 2021/07

Since the Fukushima accident, with the higher safety requirements of nuclear facilities in Japan, suppliers, manufacturers and academic societies have been actively considering the reconstruction of the safety of nuclear facilities from various perspectives. The Nuclear Regulation Authority has formulated new regulatory standards and is in operation. The new regulatory standards are based on defense in depth, and have significantly raised the levels of natural hazards and have requested to strengthen the countermeasures from the perspective of preventing the simultaneous loss of safety functions due to common factors. Facilities for dealing with specific serious accidents are required to have robustness to ensure functions against earthquakes that exceed the design standards to a certain extent. In addition, since the probabilistic risk assessment (PRA) and the safety margin evaluation are performed to include the range beyond the design assumption in the safety improvement evaluation, it is very important to extent the special knowledge in the strength of important equipment for seismic safety. This paper summarizes the research and examination results of specialized knowledge on the concept of maintaining the functions of important seismic facilities and the damage index to be considered by severe earthquakes. In the other paper, the study on reliability of seismic capacity analysis for important equipment in nuclear facilities will be reported.

Final report on feasibility study of Pu monitoring and solution measurement of high active liquid waste containing fission product at Reprocessing Facility

Sekine, Megumi; Matsuki, Takuya; Suzuki, Satoshi*; Tsutagi, Koichi; Nishida, Naoki; Kitao, Takahiko; Tomikawa, Hirofumi; Nakamura, Hironobu; LaFleur, A.*; Browne, M.*

JAEA-Technology 2019-023, 160 Pages, 2020/03

JAEA-Technology-2019-023.pdf:9.43MB

The International Atomic Energy Agency (IAEA) has proposed in its Research and Development plan (STR-385), the development of technology to enable real-time flow measurement of nuclear material as a part of an advanced approach to effective and efficient safeguards for reprocessing facilities. To address this, Japan Atomic Energy Agency (JAEA) has been tackling development of a new detector to enable monitoring of Pu in solutions with numerous FPs as a joint research program with U.S. DOE to cover whole reprocessing process. In this study, High Active Liquid Waste (HALW) Storage Facility in Tokai Reprocessing Plant was used as the test field. At first, the design information of HALW storage tank and radiation (type and intensity) were investigated to develop a Monte Carlo N-Particle Transport Code (MCNP) model. And then, dose rate distribution outside/ inside of the concrete cell where the HALW tank is located was measured to design new detectors and check MCNP model applicability. Using the newly designed detectors, gamma rays and neutron were continuously measured at the outside/ inside of the concrete cell to assess the radiation characteristics and to optimize detector position. Finally, the applicability for Pu monitoring technology was evaluated based on the simulation results and gamma-ray/neutron measurement results. We have found that there is possibility to monitor the change of Pu amount in solution by combination both of gamma-ray and neutron measurement. The results of this study suggested the applicability and capability of the Pu motoring to enhance safeguards for entire reprocessing facility which handles Pu with FP as a feasibility study. This is final report of this project.

Replacement of the glove port equipped with glove box in Nuclear Fuel Reprocessing Facility

Horigome, Kazushi; Taguchi, Shigeo; Nishida, Naoki; Goto, Yuichi; Inada, Satoshi; Kuno, Takehiko

Nihon Hozen Gakkai Dai-14-Kai Gakujutsu Koenkai Yoshishu, p.381 - 384, 2017/08

no abstracts in English

Hardening induced by energetic electron beam for Cu-Ti alloys

Ueyama, Daichi*; Semboshi, Satoshi*; Saito, Yuichi; Ishikawa, Norito; Nishida, Kenji*; Soneda, Naoki*; Hori, Fuminobu*; Iwase, Akihiro*

Japanese Journal of Applied Physics, 53(5S1), p.05FC04_1 - 05FC04_5, 2014/05

https://doi.org/10.7567/JJAP.53.05FC04

In our previous research, it was found that the hardness of Cu-Ti alloy increased by energetic heavy ion irradiation at room temperature. In the conference, we will show the result of electron beam irradiation on the hardness of Cu-Ti alloys. We used CuTi sheets with the dimension of 10 10 0.250 mm. The specimens were irradiated at 473 K and 523 K with 2 MeV electrons. For comparison, we thermally aged some specimens at the same temperatures as that for the irradiation. The electron fluence of 8.0 10/cm corresponds to the processing time of about 10 h. As a result, the thermal aging for 10 h increases the hardness by 5 or less, which is much smaller than that by the irradiation (about 20). The hardness of the reverse side of irradiated surface is almost the same as that of the irradiated surface. The present result implies that energetic electron irradiation can be a useful tool for controlling the hardness of the "bulk" Cu-Ti alloy.

Structure and dynamics of poly(vinyl alcohol) gels in mixtures of dimethyl sulfoxide and water

Kanaya, Toshiji*; Takahashi, Nobuaki; Takeshita, Hiroki*; Okura, Masatoshi*; Nishida, Koji*; Kaji, Keisuke*

Polymer Journal, 44(1), p.83 - 94, 2012/01

https://doi.org/10.1038/pj.2011.88

Rheo-SANS study on gelation of poly(vinyl alcohol)

Takahashi, Nobuaki; Kanaya, Toshiji*; Nishida, Koji*; Takahashi, Yoshiaki*; Arai, Masatoshi

Physica B; Condensed Matter, 385-386(1), p.810 - 813, 2006/11

https://doi.org/10.1016/j.physb.2006.06.096

We have studied shear flow effects on physical gelation processes of poly(vinyl alcohol) solutions in a mixture of deuterated dimethyl sulfoxide and heavy water using time-resolved 2D-SANS technique with a rheological setup. Steady shear flow was applied on the sample solution after quenching from 100 C to 25 C, and the isothermal measurements were performed. The observed two-dimensional scattering patterns under the shear flow were isotropic while the growth rate of the scattering intensity was affected. It has been revealed in a previous report that the gelation of the solution was caused through crystallization between polymer chains to form the network. Hence, focusing on the scattering intensity from the crystallites, we have evaluated the crystallization rate. It was found that the crystallization rate was accelerated in a low shear rate region (shear rate is smaller than 5 sec) and decreased with increasing the shear rate in a high rate region (bigger than 5 sec) after a maximum at 5 sec. The results suggest that the local orientation of flexible polymer chains due to the shear flow assist crystal nucleation in the low shear rate region while the once-formed crystallites are destroyed by the shear in the high shear rate region.

Three-dimensional simulation of solid-particle sedimentation using a particle-grid coupled method

Ohara, Yohei*; Fujimoto, Takuya*; Nishida, Satoshi*; Morita, Koji*; Guo, L.*; Tagami, Hirotaka; Suzuki, Toru

no journal, , 

In order to assess sedimentation behavior of fuel debris during core disruptive accidents in sodium-cooled fast reactors, a three-dimensional particle-grid coupled method was developed. Through the analyses of basic experiments on the sedimentation behavior of solid particles, fundamental adequacy of the modeling approach was confirmed.

Numerical simulation of mixed particle sedimentation using a particle-grid coupled method

Kawata, Ryo*; Ohara, Yohei*; Fujimoto, Takuya*; Nishida, Satoshi*; Morita, Koji*; Guo, L.*; Tagami, Hirotaka; Suzuki, Toru

no journal, , 

no abstracts in English