ML12272A259
| ML12272A259 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 02/01/2011 |
| From: | Richard Chang NRC/NSIR/DPR/DDEP |
| To: | Richard Guzman, Stutzke M Division of Operating Reactor Licensing, NRC/RES/DE |
| References | |
| FOIA/PA-2011-0083 | |
| Download: ML12272A259 (1) | |
Text
Chang, Richard From:
Chang, Richard Sent:
Tuesday, February 01, 2011 4:17 PM To:
Guzman, Richard; Stutzke, Martin Cc:
Schaperow, Jason; Tinkler, Charles
Subject:
PRA Information for Surry Marty and Rich, For the ISLOCA scenario for Surry:
From our site visit from Surry-we recently were told by the licensee that the catastrophic failure of 2 inline one-way check valves had a frequency of lx 10-8. We were then told that the catastrophic failure of a one-way check valve and leak-by of the other as well as a failure of a third isolation valve had a probability of 7x1 0-7.
However, Our current report states that the ISLOCA scenario does not meet the SOARCA screening criterion of 1 x 10-7 per reactor-year for a bypass event. The SPAR model assigns it a frequency of 3x10-8/reactor-year, and the licensee's PRA assigns it a frequency of 7x10-7/reactor-year. The SPAR model's frequency does not meet the SOARCA screening criterion for bypass events of lx1 0-7/reactor-year, but the licensee's PRA frequency does. Therefore, it was retained for analysis. The main reason for the difference is that the licensee assumed the likelihood of subsequent low head injection piping rupture was 1, while the NRC estimated it to be 0.1.
So my questions are this:
- 1. Does Surry have a level 2 or 3 analysis for ISLOCA?
- 2. How do they treat ISLOCA?
- 3. What is their internal events LERF frequency?
I am trying to avoid going back to plant...so if you guys could help me out, I would appreciate it.
If not, I will try to give the Plant PRA guys a ring.
- Thanks, Richard Chang Program Manager RES/DSA/SPB 301-251-7980 79