ML030860496

File Named ACRS Slides for Risk Considerations. Wpd from S. Long, NRR Computer

ML030860496
Person / Time
Site:	Davis Besse
Issue date:	06/04/2002
From:	Long S Office of Nuclear Reactor Regulation
To:
References
FOIA/PA-2003-0018
Download: ML030860496 (3)

Text

File from Steve Long's computer dated 06/04/02 06:00am named "ACRS slides for risk consid.wpd" Risk Considerations ACDF will be more significant than ALERF because containment is not affected.

ACDF = AFrequency x CCDP CCDP for medium LOCA is known from available PRAs 3 x 10-' for Davis-Besse AFrequency still must be determined

AMLOCA Frequency Two components:

"*Frequency of RCS pressure transients reaching failure pressure of as-found cavity.

"*Probability that cavity would not have been discovered before cavity grew to size that would rupture at RCS normal operating pressure.

Both components require quantification of failure pressures Second component also requires quantification of growth rate.

SDP Lessons

1. This is an example of cases where not enough is known about the phenomenon to produce a risk estimate within the time-frame envisioned by the new ROP SDP.

2. SDP is risk-based. Other safety concepts of a risk-informed process seem to be driving the agency's regulatory response in the absence of a ACDF value. In this case, loss of design margin appears to be the most important principle for consideration.