MODELING OPERATOR REDIAGNOSIS DURING AN SGTR EVENT

A parametric analysis has been performed analysing the hypothetical st eam generator tube rupture (SGTR) accident combined with the total los s of secondary heat sink. The analyses have been performed by RELAP5/M OD2/36.05 an MOD3 5M5 computer code versions using universal Krsko NPP input deck, developed at IJS. Two break sizes have been chosen for th e SGTR event: two and five double-ended broken tubes have been assumed . Total loss of secondary heat sink has been assumed from the beginnin g of the calculation with no possibility of initiating secondary-side feed and bleed. The ways of cooling down the plant after the postulate d accidents have been investigated. A scenario has been analysed, when the operator applies rediagnosis procedure, during the period of loss of secondary heat sink threat, and manages SGTR consequences first. T he Krsko nuclear power plant emergency operating procedures have been verified for this case.