ML20085D551
| ML20085D551 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 06/08/1995 |
| From: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 95-258, NUDOCS 9506160268 | |
| Download: ML20085D551 (5) | |
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VIRGINIA 15LECTHIC AND POWEH COMPANY Ricnuonn,VIHOINIA 20261 June 8, 1995 U. S. Nuclear Regulatory Commission Serial No.
95 258 Attention: Document Control Desk NAPS /JHL/MAE R4 Washington, D. C. 20555 Docket No.
50-338 License No.
NPF-4 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER SIATION UNIT 1
!NSPECTION REPORT NOS. 50-338/95-04 AND 50-339/95-04 REPLY TO A NOTICE OF VIOLATION We have reviewed your letter of May 11, 1995, which referred to the inspection conducted at North Anna Power Station from March 19,1995 to April 15,1995,and the associated Notice of Violation which was reported in inspection Report Nos. 50-338/95-04 and 50-339/95-04. Our reply to the Notice of Violation is attached.
If you have any further questions, please contact us.
Very truly yours, James P. O'Hanlon Senior Vice President - Nuclear Attachment cc:
U. S. Nuclear Regulatory Commission Region 11 101 Marietta Street, N.W.
Suite 2900 Atlanta, Georgia 30323 Mr. R. D. McWhorter NRC Senior Resident inspector North Anna Power Station 0
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e REPLY TO A NOTICE OF VIOLATION INSPECTION REPORT NOS. 50-338/95-04 AND 50-339/95-04 NRC CORMENI During an NRC inspection conducted on March 19 through April 15,1995, a violation of NRC requirements was identified. In accordance with the " General Statement of Policy and Procedure for NRC Enforcement Actions," 10 CFR Part 2, Appendix C, the violation is listed below:
Technical Specification 3.4.9.2.a requires that pressurizer temperature be limited to a maximum heatup of 100 degrees Fahrenheit (OF) or a cooldown of 2000 F, in any one hour period.
When pressurizer temperature exceeds these limits an engineering evaluation to determine the effects of the out-of-limit condition on the fracture toughness properties of the pressurizer must be performed and to determine if the pressurizer remains acceptable for continued operation.
Contrary to the above, an inadequate engineering evaluation was performed in order to determine the effects of the out-of-limit condition on the fracture toughness properties of the Unit 1 pressurizer following the September 10,1994, excessive heatup and cooldown. The assumption that the pressurizer liquid temperature was not an accurate indication of the pressurizer metal temperature lacked an engineering basis. A more detailed engineering evaluation was subsequently required to verify that the pressurizer remained acceptable for continued operation.
This is a Severity Level IV Violation (Supplement I).
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REPLY TO A NOTICE OF VIOLATION 1.
REASON FOR THE VIOLATION j
On September 10,1994, during the performance of periodic test procedure 1-PT-57.4, Safety injection Fonctional Test, letdown was isolated on North Anna Unit 1 while seal injection remained in service. This resulted in an increase in the RCS inventory causing the RCS water to flow into the pressurizer. The liquid temperature indicator at the bottom of the pressurizer sensed the cooler RCS water. Operators subsequently noted that the indicated pressurizer liquid temperature decreased greater than 200 0F in one hour.
Technical Specification 3.4.9.2, in part, requires that the pressurizer temperature be limited to a maximum heatup of 100 0F or cooldown of 200 0F, in any one hour period. The action required if the pressurizer temperature limits are exceeded are to: restore the temperature to within the limits within 30 minutes, perform an engineering evaluation to determine the effects of the out-of-limit condition on the fracture toughness properties of the pressurizer, determine that the pressure remains acceptable for continued operation or be in at least Hot Standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and reduce the pressurizer pressure to less than 500 psig within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
The observed temperature decrease was originally determined to not be indicative of a pressurizer bulk liquid temperature change. The observed temperature change occurred relatively quickly and, based on engineering judgment, it was concluded that the pressurizer metal temperature could not have changed so quickly. Therefore, it was initially determined that an actual cooldown event had not occurred and the pressurizer vessel was not thermally stressed. However, additional research was performed on March 27,1995 to further assess the Unit 1 September 10,1994 pressurizer temperature transient.
Based on the results of the additional research, it was determined that a Unit 1 pressurizer cooldown transient ad occurred on September 10, 1994.
Additionally, the subsequent increase in indicated pressurizer liquid temperature that followed the cooldown that resulted when the pressurizer heaters were energized exceeded the 100 0F in the one hour heatup limit of Technical Specification 3.4.9.2. Therefore, an engineering evaluation should have been performed as required by Technical Specification 3.4.9.2 to determine the effects of the excessive cooldown and heatup rates on the fracture toughness properties of the pressurizer.
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CORRECTIVE STEPS WHICH HAVE BEEN TAKEN AND THE RESULTS ACHIEVED Plant data for the event was provided to Westinghouce to perform a technical evaluation. Westinghouse concluded that the transient did not adversely affect the structural integrity of the pressurizer and that continued operation of Unit 1 1
was acceptable.
A detailed quantitative analysis was also performed by Westinghouse, and it concluded that the transient did not adversely affect the structural integrity of the pressurizer.
In addition, the effect of the transient data for impact on the pressurizer surge i
line with respect to the requirements of NRC Bulletin 88-11 was assessed. It was determined that the transient conditions analyzed for the pressurizer surge line as required by NRC Bulletin 88-11 enveloped the transient condition identified during the September 10,1994 event. Therefore, the cooldown event did not invalidate the conclusions of our analysis performed for NRC Bulletin l
88-11.
Unit 2 Safety injection Functional Test Procedure,2-PT-57.4, was revised as a result of the Unit 1 event to add a precaution and limitation for the operator at the controls to periodically monitor pressurizer level and maintain level at or below initial level to minimize cooldown during the test. If an uncontrolled pressurizer level increase occurs, then the operator at the controls should energize heaters as necessary to minimize liquid phase cooldown.
Performance of this test on March 25,1995 demonstrated that the test can be performed without creating a temperature transient. The Unit 1 test procedure will include similar changes before it is performed during the 1996 refueling outage.
A review of the pressurizer temperatures recorded for Unit 1 and 2 cooldown and heatup operations since 1990 was perforrned. No similar events were identified based upon this review.
LER 50-338/95-003 00, which addressed the event and was submitted on April 13,1995, was placed in Operations Department required reading.
Engineering personnel involved in the performance of periodic test procedure 1 PT-57.4 were coached in the importance of verbatim Technical Specification compliance.
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CORRECTIVE STEPS WHICH WILL BE TAKEN TO AVOID FURTHER VIOLATIONS Revisions to Unit 1 Safety injection Functional Test Procedure,1-PT-57.4, will be completed before the test is performed during the 1996 refueling outage in order to prevent a temperature transient.
As part of our independent operating experience review program, we are currently reviewing the RCS heatup and cooldown events at North Anna and within the industry to determine if additional measures should be considered to further prevent or mitigate excessive pressurizer heatups or cooldowns. Upon completion of their review, additional preventive measures will be implemented as necessary.
The Westinghouse Owners Group (WOG) has created a task team on pressurizer in-surge and out-surge thermal transients. The WOG is currently collecting data on pressurizer heatup and cooldown rates at three test plants.
As part of this study, these plants are using Westinghouse operating strategies developed to mitigate these transients. The final results of the WOG study will be evaluated for applicability to North Anna as part of our operating experience review program.
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THE DATE WHEN FULL COMPLIANCE WILL BE ACHIEVED Full compliance has been achieved.
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