What's New in 2009 Update

System Reliability Study and Component Performance Updates
LOOP Update
Initiating Event Update

System Reliability Study and Component Performance Updates

This is the fourth year for the EPIX and SPAR-based system studies and component studies.

The results in this annual update reflect the results of the enhanced component performance for emergency diesel generators, turbine-driven pumps, and motor-driven pumps in the trends.

The motor-driven pump component performance study is enhanced, meaning that the underlying data have been fully reviewed and that there are additional analyses in the document including: comparison between actual (ESF) demand reliability and all demand reliability, causes, subcomponents, method of detection, and recovery.

LOOP Update

This is the fourth LOOP Update published on the web site. This year we are including the LOOP frequency variation by Reliability Council for Grid events. The Total LOOP Frequency uncertainty calculation is being done with WINBUGS, which uses hierarchal Bayes routines to model the variation. In addition, this years LOOP update includes the EDG repair curve parameters.

Initiating Event Update

This year the staff at the INL reviewed all Initiating Events (IEs) that had a loss of condenser heat sink (LOCHS) attribute (most of these were due to loss of condenser vacuum). The issue was that the original coding guidance allowed for the counting of a trip caused by low condenser vacuum as a LOCHS.

The SPAR models assume that the condenser is unavailable for the duration of the event. Several of these events indicated that once the turbine was tripped, the condenser was available for dumping steam. To correct this, a new initial plant fault was created for the transient initiated by the loss of condenser vacuum (QL7) and those events that were coded as LOCHS inappropriately were changed to QL7. The net effect of this is that the estimate for the LOCHS for both BWRs and PWRs decreased and the transient frequency increased.