著者

川村 慎一 木村 剛生 大森 修一 奈良林 直

出版者

一般社団法人 日本原子力学会

雑誌

日本原子力学会和文論文誌 (ISSN:13472879)

巻号頁・発行日

vol.15, no.1, pp.12-20, 2016 (Released:2016-02-15)

参考文献数

9

被引用文献数

4

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A filtered containment venting system was developed for nuclear power plants. In the Fukushima Dai-ichi Nuclear Accident, widespread land contamination was caused by cesium-137. This system was developed to filter aerosol particles and reduce the amount of radioactive particle release, while protecting the primary containment vessel from over pressure by venting gas from the vessel. Performance tests were conducted under various vent gas flow rate conditions to ascertain decontamination factors for aerosol particles with various diameters. It was observed through the tests that aerodynamic diameter was a good index for characterizing various aerosol particles for the filtered containment venting system. Test results showed that the decontamination factors were well over 1,000 for aerosol particles with aerodynamic diameters larger than 0.4 μm. For aerosol particles with aerodynamic diameters larger than 0.2 μm, the decontamination factors significantly increased with the diameter. This suggested that inertial deposition was the governing mechanism for filtering aerosols in this system. The decontamination factor of the water scrubber section of the filter increased with the increase in Stokes number.

著者

川村 慎一 大木 俊 奈良林 直

出版者

一般社団法人 日本原子力学会

雑誌

日本原子力学会和文論文誌 (ISSN:13472879)

巻号頁・発行日

pp.J15.018, (Released:2016-03-15)

参考文献数

10

被引用文献数

1

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Significant leakage of the primary containment vessel (PCV) occurred on March 15, 2011 at Unit 2 of Fukushima Dai-ichi Nuclear Power Station, causing land contamination over a large area. From the radiation dose rate map of Unit 2 and the temperature trend of the PCV, degradation of the PCV top head flange gasket was identified as the cause of the leakage. The design set point of the rapture disc and operability of the valves in the hardened containment venting system were further identified as factors contributing to the leakage. Based on the lessons from the leakage, the gasket material was improved to have greater heat resistance in a steam environment, the PCV cooling system was diversified to improve reliability, and the operability and operation methods of the PCV venting were improved for greater robustness of the PCV in severe accidents.

著者

奈良林 直 島津 洋一郎 辻 雅司 辻 雅司

出版者

北海道大学

雑誌

基盤研究(B)

巻号頁・発行日

2007

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スイスにおける原子力熱エネルギー供給システムの詳細調査を踏まえ、住民の要望や地域の要求を満たすシステムについての概念形成を地域住民と共同で検討し、北海道内3000世帯の中都市に原子炉からのエネルギー供給システムの検討を実施した。可燃性毒物としてガドリウムとエルビアを酸化ウランに混入することにより、10年間燃料交換なしで運転できる炉心が構成できること、1℃/5kmの温度降下で長距離熱輸送が可能なこと、神経・知能系を取り付けた原子炉機器による予兆検知実験とその解析シミュレーションを実施し、ポンプ、バルブ、炉内機器の異常検知が可能であることを明らかにした。

著者

野田 宏 奈良林 直 吉田 智朗 中村 誠 桐本 順広

出版者

Atomic Energy Society of Japan

雑誌

日本原子力学会和文論文誌 (ISSN:13472879)

巻号頁・発行日

vol.7, no.4, pp.408-419, 2008 (Released:2012-03-02)

参考文献数

8

被引用文献数

1

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Failures on demand of a reactor core isolation cooling (RCIC) system in BWRs are the most frequent events of limiting conditions for operation during 1982-2006 in Japan, according to data gathered in Nuclear Information Archives (NUCIA). In this work, probabilities of failures of the RCIC system are analyzed by using the hierarchical Bayes method. The failures on demand of the RCIC system are classified into two groups; one is related to the demand at a periodical inspection test, which is performed almost every 13 months at the end of the periodical inspection of the nuclear power plant, and the other is related to the monthly surveillance test during plant operation. The hierarchical Bayes analysis shows the characteristics of probabilities of failures of each Japanese plant and also that probabilities of failures at the periodical inspection test are quite different from those at the surveillance test, comparing Japanese nuclear power plants with American ones. This paper provides a new approach to analyzing sparse failure data taken from nuclear power plants in Japan.

著者

奈良林 直 佐藤 修彰 辻 雅司 千葉 豪

出版者

北海道大学

雑誌

基盤研究(B)

巻号頁・発行日

2012-04-01

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新規制基準では、国内全ての原発に格納容器フィルタードベントシステム (FCVS) の設置を義務づけた。しかし、FCVS 関する公開文献は限られており、ヨーロッパの既存のFCVS は小児甲状腺癌の原因物質である有機ヨウ素の除染係数(DF)が低い。本研究では、有機ヨウ素に対して高い除染係数(DF)を有する銀ゼオライト(AgX)を使用し,より高性能なFCVSの開発を実施した。北大は、FCVSの二相流特性の安定化、スクラビングノズルの最適化を、東北大学では、放射性ヨウ素を使った吸着試験を分担し、放射線検出器のカウント値の高精度な測定可能とし、世界最高性能のDFを有するFCVSの開発に成功した。

著者

川村 慎一 奈良林 直

出版者

一般社団法人 日本原子力学会

雑誌

日本原子力学会和文論文誌 (ISSN:13472879)

巻号頁・発行日

vol.15, no.2, pp.84-96, 2016

被引用文献数

1

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Three nuclear reactors at Fukushima Daini Nuclear Power Station lost all their ultimate heat sinks owing to damage from the tsunami caused by the Great East Japan Earthquake on March 11, 2011. Water was injected into the reactors by alternate measures, damaged cooling systems were restored with promptly supplied substitute materials, and all the reactors were brought to a cold shutdown state within four days. Lessons learned from this experience were identified to improve emergency management, especially in the areas of strategic response planning, logistics, and functions supporting response activities continuing over a long period. It was found that continuous planning activities reflecting information from plant parameters and response action results were important, and that relevant functions in emergency response organizations should be integrated. Logistics were handled successfully but many difficulties were experienced. Therefore, their functions should be clearly established and improved by emergency response organizations. Supporting emergency responders in the aspects of their physical and mental conditions was important for sustaining continuous response. As a platform for improvement, the concept of the Incident Command System was applied for the first time to a nuclear emergency management system, with specific improvement ideas such as a phased approach in response planning and common operation pictures.

著者

大森 修一 奈良林 直 森 治嗣 渡邉 史紀

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.75, no.751, pp.403-405, 2009-03-25

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A Steam Injector (SI) is a simple, compact and passive pump. We are developing this innovative concept by applying the SI system for core injection system in emergency core cooling systems (ECCS) to further improve the safety of nuclear power plants. Passive ECCS in nuclear power plants would be inherently very safe and would prevent severe accidents by keeping the core covered with water (Severe accident-free concept). The passive core injection system (PCIS) driven by high-efficiency SI is a system that, in an accident such as a LOCA, attains a higher discharge pressure than the supply steam pressure used to inject water into the reactor by operating the SI. This report describes the experiments and the analytical simulation on a SI-driven PCIS for innovative-simplified nuclear power plant. In addition, we conducted the analytical simulations of SI, which grew in size for the actual nuclear power plant.