Gas entrainment phenomenon from free liquid surface in a sodium-cooled fast reactor; Measurements and evaluation on a gas core growth form the liquid surface

Uchida, Mao*; Alzahrani, H.*; Shiono, Mikihito*; Sakai, Takaaki*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki

Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 16 Pages, 2022/03

Gas entrainment from cover gas is one of key issues for sodium-cooled fast reactors design to prevent unexpected effects to core reactivity. A vortex model based evaluation method has been developed to evaluate the surface vortex gas core growth at the free surface in the reactor vessel. In this study, water experiments were performed to clarify the prediction accuracy for the vortex gas core growth during the vortex drift motion using a circulating water tunnel with an open flow channel test section. Gas core growth were predicted by applying the evaluation method to the numerical analyses performed in the same geometry of the experiments, and compared with the experimental results. It was observed the gas core growth became large at downstream region where downward velocity became large in experiment. However, the gas core length which were predicted from numerical result showed a discrepancy with the experimental result on the peak position and an overestimation of peak value.

The Examination of advanced analysis method on unsteady gas entrainment vortex applying AMR method

Matsushita, Kentaro; Fujisaki, Tatsuya*; Ezure, Toshiki; Tanaka, Masaaki; Uchida, Mao*; Sakai, Takaaki*

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 26, 6 Pages, 2021/05

For the gas entrainment vortex at the free surface in sodium-cooled fast reactors, development of the numerical analysis method to evaluate amount of the gas entrainment from the free surface has been developing. In this paper, the automatic creation of analysis meshes which can suppress the calculation cost while maintaining the prediction accuracy of the vortex shape is investigated, and the adaptive mesh refinement (AMR) method is examined to the creation of analysis mesh applying to the unsteady vortex system. The refined mesh based on the criterion evaluated by vorticity, Q-value as second invariant of the velocity and the discriminant for the eigen equation of the velocity gradient tensor is considered, and it found that the AMR method based on Q-value can refine the analysis meshes most efficiently.

Quantitative risk assessment of accident managements against volcano ash hazard in a sodium-cooled fast reactor

Suzuki, Minoru*; Sakai, Takaaki*; Takata, Takashi; Doda, Norihiro

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 7 Pages, 2019/05

https://doi.org/10.1299/jsmeicone.2019.27.1982

With an aim to establish a quantitative risk assessment of accident managements (AMs) for various external hazards, the plant dynamics analyses with Continuous Markov Chain Monte Carlo (CMMC) method were carried out to assess repeatedly occurred multi-failures by volcano ash in volcanic eruption event. AM repetition of the filter exchange to recover the cooling function of the air coolers were considered. The results showed that this method can evaluate the effectiveness of AM measures against volcanic ash fall events with respect to time progress.

Study on In-Vessel Retention (IVR) of unprotected accident for fast reactor, 1; Overview of IVR evaluation in Anticipated Transient without Scram (ATWS)

Suzuki, Toru; Sogabe, Joji; Tobita, Yoshiharu; Sakai, Takaaki*; Nakai, Ryodai

Nihon Kikai Gakkai Rombunshu (Internet), 83(848), p.16-00395_1 - 16-00395_9, 2017/04

https://doi.org/10.1299/transjsme.16-00395

no abstracts in English

Fundamental safety strategy against severe accidents on prototype sodium-cooled fast reactor

Onoda, Yuichi; Kurisaka, Kenichi; Sakai, Takaaki

Journal of Nuclear Science and Technology, 53(11), p.1774 - 1786, 2016/11

https://doi.org/10.1080/00223131.2016.1159532

Development of risk assessment methodology against natural external hazards for sodium-cooled fast reactors; Project overview and margin assessment methodology against volcanic eruption

Yamano, Hidemasa; Nishino, Hiroyuki; Kurisaka, Kenichi; Okano, Yasushi; Sakai, Takaaki; Yamamoto, Takahiro*; Ishizuka, Yoshihiro*; Geshi, Nobuo*; Furukawa, Ryuta*; Nanayama, Futoshi*; et al.

Proceedings of 11th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operation and Safety (NUTHOS-11) (USB Flash Drive), 12 Pages, 2016/10

This paper describes mainly volcanic margin assessment methodology development in addition to the project overview. The volcanic tephra could potentially clog filters of air-intakes that need the decay heat removal. The filter clogging can be calculated by atmospheric concentration and fallout duration of the volcanic tephra and also suction flow rate of each component. In this paper, the margin was defined as a grace period to a filter failure limit. Consideration is needed only when the grace period is shorter than the fallout duration. The margin by component was calculated using the filter failure limit and the suction flow rate of each component. The margin by sequence was evaluated based on an event tree and the margin by component. An accident management strategy was also suggested to extend the margin; for instance, manual trip of the forced circulation operation, sequential operation of three air coolers, and covering with pre-filter.

Development of risk assessment methodology of decay heat removal function against natural external hazards for sodium-cooled fast reactors; Project overview and volcanic PRA methodology

Yamano, Hidemasa; Nishino, Hiroyuki; Kurisaka, Kenichi; Okano, Yasushi; Sakai, Takaaki; Yamamoto, Takahiro*; Ishizuka, Yoshihiro*; Geshi, Nobuo*; Furukawa, Ryuta*; Nanayama, Futoshi*; et al.

Proceedings of 24th International Conference on Nuclear Engineering (ICONE-24) (DVD-ROM), 10 Pages, 2016/06

https://doi.org/10.1115/ICONE24-60023

This paper describes mainly volcanic probabilistic risk assessment (PRA) methodology development for sodium-cooled fast reactors in addition to the project overview. The volcanic ash could potentially clog air filters of air-intakes that are essential for the decay heat removal. The degree of filter clogging can be calculated by atmospheric concentration of ash and tephra fallout duration and also suction flow rate of each component. The atmospheric concentration can be calculated by deposited tephra layer thickness, tephra fallout duration and fallout speed. This study evaluated a volcanic hazard using a combination of tephra fragment size, layer thickness and duration. In this paper, each component functional failure probability was defined as a failure probability of filter replacement obtained by using a grace period to a filter failure limit. Finally, based on an event tree, a core damage frequency was estimated about 310/year in total by multiplying discrete hazard probabilities by conditional decay heat removal failure probabilities. A dominant sequence was led by the loss of decay heat removal system due to the filter clogging after the loss of emergency power supply. A dominant volcanic hazard was 10 kg/m of atmospheric concentration, 0.1 mm of tephra diameter, 50-75 cm of deposited tephra layer thickness, and 1-10 hr of tephra fallout duration.

Operational experience of CW SRF injector and main linac cryomodules at the Compact ERL

Sakai, Hiroshi*; Enami, Kazuhiro*; Furuya, Takaaki*; Kako, Eiji*; Kondo, Yoshinari*; Michizono, Shinichiro*; Miura, Takako*; Qiu, F.*; Sato, Masato*; Shinoe, Kenji*; et al.

Proceedings of 56th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs (ERL 2015) (Internet), p.63 - 66, 2015/12

http://accelconf.web.cern.ch/AccelConf/ERL2015/papers/weiblh2054.pdf

no abstracts in English

The TEST of the helium processing for the ERL main linac superconductive cavity

Shinoe, Kenji*; Sakai, Hiroshi*; Umemori, Kensei*; Enami, Kazuhiro*; Sawamura, Masaru; Egi, Masato*; Furuya, Takaaki*

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.548 - 552, 2015/09

http://www.pasj.jp/web_publish/pasj2015/proceedings/PDF/WEP0/WEP046.pdf

no abstracts in English

Progress of thermal hydraulic evaluation methods and experimental studies on a sodium-cooled fast reactor and its safety

Kamide, Hideki; Ohshima, Hiroyuki; Sakai, Takaaki; Tanaka, Masaaki

Proceedings of 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16) (USB Flash Drive), p.8141 - 8155, 2015/08

In this paper, the authors focus on four kinds of thermal-hydraulic issues associated with the SDC, i.e. fuel assembly thermal-hydraulics, natural circulation decay heat removal, thermal striping phenomena, and core disruptive accidents, and provide a description of their evaluation method developments including verification and validation and necessary experimental studies for the Japan Sodium-cooled Fast Reactor (JSFR). These evaluation methods are planned to be eventually integrated into a comprehensive numerical simulation system that can be applied to all phenomena envisioned in SFR systems and that can be expected to become an effective tool for the development of human resource and the handing down of knowledge/technologies.