The purpose of the presented method is to be applied for categorization in terms of safety of the findings (negative as deviations and positive as strengths) identified during the Periodic Safety Review (PSR) of units 5 and 6 at Kozloduy NPP. Such categorization is the main argument of fixing the scope and the deadline of measures to eliminate the deviations. The method consists of an approach as well as steps for categorization of the identified deviations. That includes definition of (1) The significance of the deviation in terms of safety; and (2) A level of the deviations in terms of the requirements for safety, applied technology, basic scientific knowledge and analytical methods, the evaluation of the cumulative effect of accomplished modification and equipment aging, organizational structure of the Licensee (management and operating staff). The method is developed based on the concept of Defence in depth (DiD), which is inherent in the design of the nuclear units.
Keywords: Deviation – PSR negative findings, Periodic Safety Review (PSR), PSR Safety Factor (SF), Reference basis, Criteria and levels for categorization