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

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.