ML18153A290
| ML18153A290 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 03/30/1998 |
| From: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 98-171, NUDOCS 9804070360 | |
| Download: ML18153A290 (2) | |
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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 March 30, 1998 Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20005
Dear Sir:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 1 PART LENGTH CONTROL ROD DRIVE MECHANISM HOUSING LEAKAGE ISSUE Serial No.
SPS/CGL Docket Nos.
License Nos.98-171 R1 50-280 DPR-32 Northern States Power Company recently identified a leak in a reactor vessel head penetration at Prairie Island Nuclear Station Unit 2. After further investigation of the leak, it was determined that the leak was at a dissimilar metal weld in a part length control rod drive mechanism (CROM) housing.
Surry Units 1 and 2 have been identified by the Westinghouse Owners Group (WOG) as potentially affected units.
Virginia Electric and Power Company has been actively involved in the WOG activities associated with the part length control rod drive mechanism (CROM) housing weld failure evaluation and development of proposed corrective actions.
The WOG's technical assessment of the dissimilar weld issue and safety assessment were provided to the NRC in a WOG letter from Mr. R. A. Newton to Mr. F. J. Miraglia (Serial No. OG-98-037), dated March 6, 1998.
The WOG investigation and safety assessment have reached the following conclusions:
the Prairie Island flaw originated from weld fabrication and was not service induced, there was no evidence of additional flaw growth during service, nineteen part length CRDMs have been ultrasonically examined to date with only the Prairie Island flaw being identified, such weld fabrication flaws are extremely unlikely to be present based on fabrication inspection criteria, operating plants are sensitive to leakage, particularly reactor coolant system
- leakage, for a failure to occur, a significant flaw not previously identified must exist and an abnormal load would be required to cause the flaw to fail, a part length CROM housing failure is bounded by existing safety analyses, and continued plant operation will not result in an increase in risk.
A March 6, 1998 WOG letter to affected utilities (Serial No. OG-98-038) summarized the issue and identified potential options. We are currently reviewing that information and will provide a future transmittal outlining an action plan to address the part length,\\D CROM housing leakage issue for Surry Units 1 and 2.
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Consistent with the WOG recommendations, the purpose of this letter is to advise the N'RC of activities undertaken relative to this issue during the ongoing Surry Unit 1 maintenance outage.
We began a planned nine-day maintenance outage on March 20, 1998. The intent of this short planned maintenance outage was to perform specific equipment repairs or replacements (i. e., pressurizer manway leakage repair, PORV leakage repairs, reactor coolant pump motor replacement) to enhance plant reliability and eliminate plant conditions not consistent with our plant performance and operational standards.
Because of the recent WOG recommendations on the part length CROM housing leakage issue, we expanded the maintenance outage scope to include a "best effort" visual inspection of the reactor vessel head and penetration area.
This inspection, which was capable of detecting boron deposits on the visually accessible, peripheral portions of the head and penetration area, was conducted on four of the five part length CROM housings located near the periphery of the reactor head.
The inspection did not reveal any evidence of part length CROM housing leakage.
As noted above, we will provide a future transmittal outlining an action plan to address the part length CROM housing leakage issue for Surry Units 1 and 2. Should you have any questions or require additional information, please contact us.
Very truly yours,
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James P. O'Hanlon Senior Vice President - Nuclear Commitments made in this letter:
- 1. We will provide a future transmittal outlining an action plan to address the part length CROM housing leakage issue for Surry Units 1 and 2.
cc:
United States Nuclear Regulatory Commission Regional Administrator - Region II Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 Mr. R. A. Musser NRC Senior Resident Inspector Surry Power Station