Search - Number 20 - STUDY OF VVER-1000 OPERATION IN CASE OF LAST MAIN FEEDWATER PUMP TRIPPING UNDER POWER NO MORE THEN 25 %

STUDY OF VVER-1000 OPERATION IN CASE OF LAST MAIN FEEDWATER PUMP TRIPPING UNDER POWER NO MORE THEN 25 %
Cover not present STUDY OF VVER-1000 OPERATION IN CASE OF LAST MAIN FEEDWATER PUMP TRIPPING UNDER POWER NO MORE THEN 25 %
Category: Number 20
Publication: 20
Summary

The paper describes an operation of the reactor control and protection system of VVER-1000 in case of the steam generator (SG) feedwater failure. As the initiating event, the last main feedwater pump (MFWP) tripping under current reactor power no more then 25 % is assumed. Further feeding of steam generators is provided by two or one auxiliary feedwater pumps (AFWP). According to the VVER-1000 design requirements, the last MFWP tripping under reactor power more than 25 % shall be accompanied by the reactor scram signal. If the reactor power is less than 25 %, the reactor should be transferred to the reduced power level of 5 % by operation the power limitation controller (ROM). The results of the MFWP tripping transient analyses under power 25 % or less are presented. It is shown that in some cases the ROM does not provide a transition of the reactor to the required power level. AFWP capacity is insufficient to maintain the required levels in the steam generators that results in tripping of main circulation pumps (MCP) then, respectively, reactor scram initiation. The reasons for the distinctions of analyzed transients from the required design progression are examined and some procedures to prevent reactor scram are proposed.

Keywords: VVER, reactor scram, main feedwater pump, auxiliary feedwater pump, steam generator level.

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