ML063210077
| ML063210077 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 11/16/2006 |
| From: | Ted Sullivan Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| Download: ML063210077 (7) | |
Text
NRC Perspective on Wolf Creek Inspection Results Ted Sullivan, SLS, NRR
2 NRC Interest in Wolf Creek Inspection Results z circumferential flaws z reported lengths longer than previous experience z multiple circumferential flaws in a single weld
3 NRC Interest in Wolf Creek (Continued) z potential safety concerns with Wolf Creek inspection results
- long circumferential flaws
- effect of flaw length on time to leakage
- effect of flaw length on time between leakage and rupture under design basis loadings
4 NRC Analyses of Wolf Creek (WC) Flaws z
preliminary calculations of time for WC size flaws to leak z
preliminary calculations of time for WC size flaws to fail z
2 independent calculations z
various assumptions used to bound time estimates
- fracture mechanics models
- residual stress assumptions
5 NRC Analyses of Wolf Creek Flaws (Continued) z time to leakage potentially ranges < 1 year to several years
- depends upon nozzle analyzed
- depends upon assumptions z time from leakage to failure calculations being revised
6 NRC Analyses of Wolf Creek Flaws (Continued) z most conservative analyses indicate more urgency for baseline inspection than previously considered z other relevant factors in assessing analyses
- visual inspections have not found pressurizer leaks at other plants
- inspections of pressurizer nozzles at 8 other plants found no other circumferential flaws
- smaller circ PWSCC found in other RCS locations z inspections or mitigation at 38 plants outstanding z uncertainties need to be addressed in near-term
7 Conclusions z completed preliminary calculations z meeting today to collect information and gain industrys perspectives and insights z interested in reducing uncertainties z staff will evaluate information industry provides