ENS 52378
ENS Event | |
|---|---|
05:00 Nov 18, 2016 | |
| Title | Part 21 Notification - Control Rod Guide Card Excessive Wear |
| Event Description | The following report is excerpted from Westinghouse fax LTR-NRC-16-74:
Westinghouse nuclear steam supply system (NSSS) plants that are using iron nitride rod cluster control assemblies (RCCAs) in conjunction with Westinghouse 17x17 A or 17x17 AS style guide tubes (GTs), the GT guide card wear inspection guidance provided in Westinghouse report WCAP-17451-P, Revision 1, is not conservative. Based on the data, a determination was made as to whether an affected plant could exceed its permissible number of worn guide cards before completing its first guide card wear measurement (GCWM) inspection, the timing of which is based on recommendations documented in the WCAP. The concern associated with exceeding the permissible number of worn guide cards is that a rodlet might slip out of alignment with the GT guide card fingers and become stuck. For example, if an unsupported rodlet were to deflect as a result of applied lateral fluid forces during normal operation, it could get caught on the corner of a worn guide card finger and jam or buckle during rod motion (i.e., scram). Additionally,. if a GT with an excessive number of worn guide cards experiences a seismic event or loss-of-coolant accident (LOCA), an unsupported rodlet might become plastically deformed, which could prevent a RCCA from scramming properly. Should this affect multiple GT locations, it could prevent a plant from achieving reactor shutdown using only the RCCAs. Left uncorrected, the wear inspection guidelines in WCAP-17451-P, Revision 1, underestimate the 17x17 A and 17x17 AS style GT guide card wear attributed to the use of iron nitride RCCAs to the extent that, for the four plants listed, the WCAP recommended number of effective full-power years (EFPYs) until the first GCWM is performed may no longer have margin to safety. The guidelines presented in this WCAP do not result in a defect for the other plants to which the WCAP applies. Affected reactors are: Catawba Units 1 and 2, McGuire Unit 2 , and Millstone Unit 3. |
| Where | |
|---|---|
| Westinghouse Cranberry Township, Pennsylvania (NRC Region 1) | |
| Organization: | Westinghouse |
| Reporting | |
| 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
| Time - Person (Reporting Time:+9.7 h0.404 days <br />0.0577 weeks <br />0.0133 months <br />) | |
| Opened: | James Gresham 14:42 Nov 18, 2016 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Nov 18, 2016 |
| 52378 - NRC Website
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Westinghouse with 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
WEEKMONTHYEARENS 544402019-12-12T05:00:00012 December 2019 05:00:00
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