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
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.
1
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.
2
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 3
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.
4