engleski

Screening Methodology for the Evaluation of PTS scenarios in the Symptom based Emergency Operating Procedures

Integrity of the reactor pressure vessel must be preserved throughout the plant operation as well in the postulated accidental conditions. Consistently, the actions that operators are instructed to perform in order to mitigate accidents should not adversely affect integrity of the reactor pressure vessel. Special consideration in this frame is dedicated to the Pressurized Thermal Shock transients (PTS), overcooling transients (interaction of cold safety injection water and hot vessel wall) with high pressure in reactor coolant system, which can cause damage to the reactor pressure vessel. PTS screening methodology was used according to determined criteria to select the most severe PTS scenarios caused by operator actions for two loop PWR nuclear power plant. The aim was to provide bounding analysis for the additional verification of the Symptom based Emergency Operating Procedures (SEOP). In order to bound asymmetrical behaviour of the two loop plant, transients with the most adverse screening criteria were further analyzed with vertically split reactor vessel model, and screening criteria were applied to the results obtained using RELAP5 computer code and split reactor pressure vessel model Additionally, on the basis of requirements from the 10 CFR 50.61, methodology accepted by US NRC, an assessment was performed to project and asses the values of PTS temperature (RTPTS) for the analysed PWR nuclear power plant.

PTS; EOP; RELAP

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