ML20050T442
| ML20050T442 | |
| Person / Time | |
|---|---|
| Issue date: | 02/19/2020 |
| From: | Matthew Leech Office of Nuclear Reactor Regulation |
| To: | |
| Leech M | |
| References | |
| Download: ML20050T442 (4) | |
Text
1 Revision to IMC 0609 Appendix H Containment Integrity Significance Determination Process The revision to Appendix H is in progress and projected to be issued by the end of April 2020.
The reason for the revision is to update Appendix H for the AP1000 design.
Appendix H was previously revised in February 2019, so this is a focused update for AP1000.
2 Revision to IMC 0609 Appendix H The current approach on how App H will be modified for the AP1000..
For type A findings (findings that affect both CDF and LERF)
It will be treated the same as a an existing large, dry PWR containment in Appendix H, with only a minor difference.
- In other words the tables 6.1 and 6.2 currently in Appendix H for screening and assessing type A findings will look the same for an AP1000 and a Large Dry PWR containment Minor difference
- The potential for consequential steam generator tube rupture (C-SGTR) will not be always screened out if the accident sequences that significantly affect the conditional probability of having a C-SGTR exist.
3 Revision to IMC 0609 Appendix H For type B findings (findings that only affect LERF and not CDF):
AP1000 will be treated the same as a an existing large, dry PWR containment for screening purposes in Appendix H. With only minor differences.
Tables 7.1 and 7.2 will be almost the same between an AP1000 and an existing large, dry PWR containment except:
- AP1000s can be evaluated for findings against hydrogen igniters, but only for a significant loss of function to the igniters.
- The risk significance potential of type B findings for an AP1000 will be significantly less than for existing large dry PWRs due to the lower baseline CDF of the AP1000 design
4 Revision to IMC 0609 Appendix H Summary
- Big Picture - AP1000 reactors will be treated the same as an existing large dry containment with only minor differences.
Other items:
- The technical basis document for Appendix H (IMC 0308, Att 3, App H) will be updated at a later date with a goal of December 2020.
- Keep in mind that App H screening and assessment only arrives at an intermediate risk result that can be further refined if needed.