Basic concept of safety evaluation method for decommissioning of nuclear power plants by applying a graded approach

• Published in: Nuclear engineering and design Vol. 379; p. 111212
• Main Authors: Kudo, Seiichi, Sugihara, Takuma
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.08.2021; Elsevier BV
• Subjects: BSL/BSO; Constraint; Decommissioning; Dismantling; Evaluation; Nuclear engineering; Nuclear power plants; Nuclear safety; Optimization; Pressurized water reactors; Radiation; Radiation effects; Radiation protection; Radioactivity; Safety; Safety measures; Severity classification; The public dose evaluation; Severity classification; BSL/BSO; The public dose evaluation; Constraint; Radiation protection; Optimization
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2021.111212

•The concept of decommissioning safety evaluation method applying the graded approach was constructed.•Based on UK SAPs BSL/BSO, the severity has classified into following three categories. 1) safety measures required. 2) safety measures required for optimization of radiation protection. 3) safety measures not required.•The severity of the public dose has divided into 4 ranks using regulation value, dose constraint, and dose exemption criterion.•Three stepwise techniques for determining severity has proposed. The IAEA has proposed to apply a graded approach that takes the safety measures commensurate with the magnitude of risk in decommissioning of nuclear power plants (NPPs). In this paper, the basic concept of the safety evaluation method to support development of the decommissioning plan of NPPs by applying a graded approach was established. The severity of consequence of radiation exposure risk to the public during decommissioning was divided into following three categories. Category 1 - safety measures required. Category 2 - safety measures required for optimization of radiation protection. Category 3 - safety measures not required. A procedure of classifying each object such as equipment and structures to be dismantled into the three categories was established based on its residual radioactivity and consequence of the expected accidents. Each object to be dismantled of PWR plant was classified using a simplified method with the residual radioactivity. It is estimated that the ratio for Category 1 by weight was about 0.03%, that for Category 2 was about 16%, and that for Category 3 was over 80%. It has become applicable to specify the scope of the decommissioning activities where the safety measures should be carried out intensively and the scope of decommissioning plans for optimizing of radiation protection.