{"id":32331,"date":"2022-05-17T17:11:45","date_gmt":"2022-05-17T17:11:45","guid":{"rendered":"https:\/\/sitepourvtc.com\/?page_id=32331"},"modified":"2023-09-26T09:55:48","modified_gmt":"2023-09-26T09:55:48","slug":"practical-elimination","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-safety\/practical-elimination\/","title":{"rendered":"Practical Elimination"},"content":{"rendered":"
The term \u201cpractical elimination<\/strong>\u201d appeared for the first time in 1993 in the definition of the general safety objectives for future pressurized water reactors.<\/p>\n The most recent international texts, particularly those issued by WENRA and the IAEA, state that \u201cpractical elimination<\/strong>\u201d should be applied to core melt situations likely to lead to early or large releases.<\/p>\n Paragraph 2.13(4) of SSR-2\/1 (Rev. 1) states:<\/p>\n \u201cThe safety objective in the case of a severe accident is that only protective actions that are limited in terms of lengths of time and areas of application would be necessary and that off-site contamination would be avoided or minimized. Event sequences that would lead to an early radioactive release or a large radioactive release are required to be \u2018practically eliminated<\/strong>.\u201d<\/em><\/p>\n In this context, an early radioactive release for which off-site protective actions would be necessary but would be unlikely to be fully effective in due time. A \u2018large radioactive release\u2019 is a release for which off-site protective actions that are limited in terms of length of time and areas of application would be insufficient for the protection of people and of the environment.<\/p>\n So situations likely to lead to large releases, because of the simultaneous or successive loss of integrity of all the containment barriers or because of the bypass of these barriers (containment bypass situations):<\/p>\n The event sequences for which a specific demonstration of their \u2018practical elimination\u2019 is required should be classified as follows:<\/p>\n \u201cPractical elimination<\/strong>” of such accident situations can be demonstrated by deterministic and\/or probabilistic considerations, considering the uncertainties due to the limited knowledge of some physical phenomena. This demonstration can be based on various aspects such as:<\/p>\n For some external hazards, it may be not practical or even possible to demonstrate that the occurrence of a hazard of such severity that could cause extensive plant damage leading to a large or early radioactive release, and therefore need to be practically eliminated, is below a threshold of frequency such as 10-6<\/sup>\/year.<\/p>\n\n
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