Shevyelov D. Safety Analysis and Express-Methods of NPPs with WWER State Evaluation during accidents.

The dissertation is dedicated to development of best-estimated models and express-methods used for NPPs with WWER state evaluation during the accidents. WWER pressurizer model was developed and proved, which improves precision and physical correctness of the results, has low nodalization sensitivity and practically eliminates user effect. The postulated accident classes analyzed and the key parameters found to identify the initial event occurrence and its quantitative parameters. For the case of small and intermediate primary leaks express-method was built to determine break size and location. This method can be used in the operator support systems. For beyond design basis accident with complete loss of secondary heat removal, analysis performed and optimal strategy of accident management developed using primary “Feed and Bleed" procedure. The criteria and procedure initiation conditions were determined.