Object

Within the scope of Contract № 44-00-16 / 09.04.2019 with the Nuclear Regulatory Agency with subject: “Expertise of selected reports from stage 2 of the project for extension of the operation period of Unit 6 of Kozloduy NPP, related to justification of the possibility for safe operation of the reactor vessel and part of the main building structures “

Scope of the project

Subtask: Execution of independent verification calculations within the expertise of the analysis of the resistance of the reactor vessel to cold brittleness.

Results

Within the task, an analysis of the presented data on the properties of the base metal materials of the hull, the welds and the surfacing was performed, taking into account the results of the research of the witness samples and the results of the neutron fluence calculation of the reactor vessel for the period. of DSE. Defects in the surfacing to the reactor vessel have been postulated. Systemic thermohydraulic analyzes of events leading to abrupt cooling of the reactor vessel have been performed. Strength calculations were performed to determine the stress intensity factor in the reactor vessel materials.