Effectiveness evaluation methodology of the measures for improving resilience of nuclear structures at ultra-high temperature

Onoda, Yuichi; Kurisaka, Kenichi; Yamano, Hidemasa

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05

The objective of this study is to develop an effectiveness evaluation methodology of the measures for improving resilience of nuclear structures at ultra-high temperature by using the failure mitigation technology. At the beginning, to identify the accident sequences having the potential to improve resilience, the characteristics of a next-generation loop-type sodium-cooled fast reactor (SFR) in Japan has been investigated by analyzing the event tree of level-1 and level-2 probabilistic risk assessment. As a result, event sequences of loss of heat removal systems (LOHRS) are identified. The effectiveness of the measures for improving resilience is evaluated by quantifying the reduction rate of core damage frequency before and after the introduction of the measures for improving resilience for all the accident sequences leading to LOHRS. To examine applicability of the developed methodology, a trial evaluation has conducted for a next-generation loop-type SFR in Japan. Through the applicability examined, the method for the effectiveness evaluation was developed successfully. The refinement of the conditional success probability of the measures for improving resilience is the future work.

Evaluation of detectability of pump/diagrid link rupture in pool-type sodium-cooled fast reactor

Onoda, Yuichi; Uchita, Masato*; Tokizaki, Minako*; Okazaki, Hitoshi*

Proceedings of 29th International Conference on Nuclear Engineering (ICONE 29) (Internet), 6 Pages, 2022/08

https://doi.org/10.1115/ICONE29-91688

The safety analyses were carried out to confirm the sufficiency of the function of the plant protection system against the pump/diagrid link rupture. The target plant is a pool-type SFR of about 600 MWe class equipped with an axially homogeneous core currently under development in Japan. In the pool-type SFR, the primary system piping connects primary pump and the high-pressure sodium plenum located at the inlet of fuel sub-assemblies and called "pump/diagrid link". Because this piping is submerged in the reactor vessel, it is difficult to detect small scale sodium leakage in this piping, and thus a certain large pipe break like guillotine should be assumed and evaluated as a design basis event. In order to confirm the detectability of pump/diagrid link rupture by safety protection system signals, a series of analyses of the guillotine break for a pump/diagrid link were carried out. Sensitivity study had also been performed to consider the uncertainty of the reactivity coefficient in the analyses. The sufficiency of the function of the plant protection system against the pump/diagrid link rupture was confirmed by the analysis results that at least two signals are transmitted for the detection of the event, which is the development target of the plant protection system in pool-type SFR.

Modelling and simulation of the source term for a sodium cooled fast reactor under hypothetical severe accident conditions; Final report of a coordinated research project

Arokiaswamy, J. A.*; Batra, C.*; Chang, J. E.*; Garcia, M.*; Herranz, L. E.*; Klimonov, I. A.*; Kriventsev, V.*; Li, S.*; Liegeard, C.*; Mahanes, J.*; et al.

IAEA-TECDOC-2006, 380 Pages, 2022/00

https://www.iaea.org/publications/15086/modelling-and-simulation-of-the-source-term-for-a-sodium-cooled-fast-reactor-under-hypothetical-severe-accident-conditions

The IAEA coordinated research project on "Radioactive Release from the Prototype Sodium Cooled Fast Reactor under Severe Accident Conditions" was devoted to realistic numerical simulation of fission products and fuel particles inventory inside the reference sodium cooled fast reactor volumes under severe accident conditions at different time scales. The scope of analysis was divided into three parts, defined as three work packages (WPs): (1) in-vessel source term estimation; (2) primary system/containment system interface source term estimation; and, (3) in-containment phenomenology analysis. Comparison of the results obtained in WP-1 indicates that the release fractions of noble gases and cesium radionuclides, and fractions of radionuclides released to the cover gas are in a good agreement. In the analysis using a common pressure history in WP-2, the results were in good agreement indicating that the accuracy of the analysis method of each institution is almost the same. The standalone case, which uses a set of pre-defined release fractions, was defined for WP-3 which enables to decouple this part of analysis from previous WPs. There is broad consensus among the predicted results by all the participants in WP-3.

Development of effectiveness evaluations technology of the measures for improving resilience of nuclear structures at ultra high temperature

Onoda, Yuichi; Nishino, Hiroyuki; Kurisaka, Kenichi; Yamano, Hidemasa

Proceedings of Asian Symposium on Risk Assessment and Management 2021 (ASRAM 2021) (Internet), 11 Pages, 2021/10

The effectiveness evaluations technology of the measures for improving resilience by applying a fracture control concept under ultra-high temperature conditions has developed for prototype sodium-cooled fast reactor Monju as a model plant, and the trial evaluation has conducted using this technology in this paper. The important accident sequences to which the fracture control concept is expected to be applied under ultra-high temperature condition are identified by investigating the results of the existing researches of level-2 probabilistic risk assessment for Monju. Accident sequences categorized in protected loss of heat sink and loss of reactor level are both identified as such important accident sequences which has the potential to prevent core damage. This study has developed the technology to evaluate the effectiveness of improving resilience, where the headings which stand for success or failure of the measures to improve resilience are introduced into the event tree, the branch probability of them is set, and the effectiveness of improving resilience is expressed as the reduction of core damage frequency. As a result of the trial evaluation of the effectiveness for the measures to improve resilience, it is confirmed that core damage frequency can be reduced by applying fracture control concept. The branch probability of the measures to improve resilience proposed in this study is tentatively assigned based on the assumption. This value is expected to be quantified by the forthcoming analyses of the integrity for the reactor vessel structure at ultra-high temperature. The technology developed in this study will be applied for the evaluation of improving resilience of the next generation sodium-cooled fast reactor.

Electron-tracking Compton camera imaging of technetium-95m

Hatsukawa, Yuichi*; Hayakawa, Takehito*; Tsukada, Kazuaki; Hashimoto, Kazuyuki*; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Tanimori, Toru*; Sonoda, Shinya*; Kabuki, Shigeto*; et al.

PLOS ONE (Internet), 13(12), p.e0208909_1 - e0208909_12, 2018/12

AA2018-0639.pdf:2.39MB

https://doi.org/10.1371/journal.pone.0208909

Imaging of Tc radioisotope was conducted using an electron tracking-Compton camera (ETCC). Tc emits 204, 582, and 835 keV rays, and was produced in the Mo(p,n)Tc reaction with a Mo-enriched target. The recycling of the Mo-enriched molybdenum trioxide was investigated, and the recycled yield of Mo was achieved to be 70% - 90%. The images were obtained with each of the three rays. Results showed that the spatial resolution increases with increasing -ray energy, and suggested that the ETCC with high-energy -ray emitters such as Tc is useful for the medical imaging of deep tissue and organs in the human body.

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

Production of Tc for Compton camera imaging

Hatsukawa, Yuichi; Hashimoto, Kazuyuki; Tsukada, Kazuaki; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Nagai, Yasuki; Tanimori, Toru*; Sonoda, Shinya*; Kabuki, Shigeto*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1283 - 1285, 2015/02

https://doi.org/10.1007/s10967-014-3508-0

Technetium-99m (Tc) is used in radioactive medical diagonostic tests, for example as a radioactive tracer that medical equipment can detect in the human body. It is well suited to the role because it emits readily detectable 141 keV rays, and its half-life is 6.01 hours (meaning that about 94% of it decays to technetium-99 in 24 hours). There are at least 31 commonly used radiopharmaceuticals based on technetium-99m for imaging and functional studies of the brain, myocardium, thyroid, lungs, liver, gallbladder, kidneys, skeleton, blood, and tumors. Recent years, with the develop-ment of the Compton camera which can realize high position resolution, technetium isotopes emitting high energy -rays are required. In this study, technetium-95m which emits some rays around 800 keV was produced by the Mo(p,n)Tc reaction.

Development of microbeam formation and single-ion hit technologies at the TIARA cyclotron

Yokota, Wataru; Sato, Takahiro; Kamiya, Tomihiro; Okumura, Susumu; Kurashima, Satoshi; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Yoshida, Kenichi; Funayama, Tomoo; Sakashita, Tetsuya; et al.

JAEA-Technology 2014-018, 103 Pages, 2014/09

JAEA-Technology-2014-018.pdf:123.66MB

The world's first microbeam focusing technology for heavy ions of hundreds MeV accelerated by a cyclotron has been developed at the TIARA facility in the Takasaki Advanced Radiation Research Institute of the Japan Atomic Energy Agency. The technology enables us to form a microbeam of less than 1 m in diameter and to shoot a specified point on a target by one ion (single-ion hit) with spatial accuracy of microbeam size. In the course of the development, a cyclotron technology to accelerate a small energy-spread beam of hundres MeV, which is necessary for focusing to 1 m, has been developed as well as a beam focusing apparatus, beam size measurement and so forth based on the several-MeV microbeam/single-ion hit system of the TIARA electrostatic accelerators. Applicability of the technologies was examined by actual use in irradiation experiment and the result were fed back to them. This paper reports the process and the results of the development over ten years.

Three-pin cluster CABRI tests simulating the unprotected loss-of-flow accident in sodium-cooled fast reactors

Onoda, Yuichi; Fukano, Yoshitaka; Sato, Ikken; Marquie, C.*; Duc, B.*

Journal of Nuclear Science and Technology, 48(2), p.188 - 204, 2011/02

https://doi.org/10.3327/jnst.48.188

Two three-pin cluster tests simulating the Unprotected Loss-of-Flow (ULOF) accident of Sodium-cooled Fast Reactors (SFRs) were conducted focusing on fuel relocation and freezing behavior. Based on detailed data evaluation and theoretical interpretation for the three-pin cluster tests, it is concluded that axial fuel relocation and freezing are dominated by local fuel enthalpy, and the relation between fuel dispersal and fuel enthalpy observed in these CABRI tests is basically applicable to the pin-bundle condition. It is also clarified that a fuel/steel mixture tends to create tight blockages near the axial ends of the relocating fuel. Part of the fission gas released from the fuel is expected to be trapped within the bottled-up region between the upper and lower blockages and will keep this region pressurized for a relatively long period.

Fuel pin behavior under slow-ramp-type transient-overpower conditions in the CABRI-FAST experiments

Fukano, Yoshitaka; Onoda, Yuichi; Sato, Ikken; Charpenel, J.*

Journal of Nuclear Science and Technology, 46(11), p.1049 - 1058, 2009/11

https://doi.org/10.3327/jnst.46.1049