SCDAP/RELAP5 Analysis of Station Blackout with Pump Seal LOCA in Surry Plant

Abstract

During a station blackout of PWR. the pump seal will fail due to loss of the seal cooling. This particular transient-LOCA sequence designated as S3-TMLB' analyzed by SNL with MELPROG/TRAC for Surry plant showed that the depressurization due to the pump seal LOCA would result in early accumulator injection and subsequent core cooling which lead to the delay of reactor pressure vessel (RPV) meltthrough. The present analysis was performed with SCDAP/RELAP5 to evaluate this scenario shown in the MELPROG/TRAC analyses. Additionally. the calculated results were compared with the similar experimental studies of JAERI's ROSA-IV program.The present analyses showed t h a t : (1) During S3-TMLB', the loop seal clearing would occur and cause a slight delay of accident progression. (2) It is unlikely that the accumulator injection, which leads to the delay of RPV meltthrough by approximately 60min, is initiated automatically during S3-TMLB'. Accordingly, an intentional depressurization using PORVs is recommended for the mitigation of the accident consequences. (3) The present SCDAP/RELAP5 analyses did not show significant delay of accident progression. It was found that non-realistic lower heat generation and higher core cooling models used in the MELPROG/TRAC analysis are attributed to this discrepancy.

Safety Analysis for Accident-Tolerant Fuels with Increased Enrichment and Extended Burnup

“…In this scenario, the LBLOCA event is followed by an initial failure of the LPSI system of ECCS due to equipment failure. However, unlike the previous LOCA analysis of the Surry reactor [45] and [46] the LPSI capability is restored shortly after the reactor water levels fall below the bottom of active fuel which occurs 27 minutes after the onset of the LOCA event an assumption of this research [39].…”

Safety Analysis for Accident Tolerant Fuels with Increased Enrichment and Extended Burnup

“…In this scenario, the LBLOCA event is followed by an initial failure of the LPSI system of ECCS due to equipment failure. However, unlike the previous LOCA analysis of the Surry reactor [39] and [40] the LPSI capability is restored shortly after the reactor water levels fall below the bottom of active fuel which occurs 27 minutes after the onset of the LOCA event an assumption of this research [33].…”

Review of thermal-hydraulic researches in severe accidents in light water reactors

“…During a station blackout of PWR, the pump seal will fail due to loss of the seal cooling. This particular transient-LOCA sequence analyzed for Surry plant showed that the depressurization due to the pump seal LOCA would result in early accumulator injection and subsequent core cooling which lead to the delay of RPV meltthrough [33]. The analysis was performed with SCDAP/RELAP5 to evaluate this scenario shown in the analyses.…”