ML20035F153
| ML20035F153 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/14/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20035F151 | List: |
| References | |
| NUDOCS 9304200338 | |
| Download: ML20035F153 (3) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l
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i THE RE0 VEST FOR ENFORCEMENT DISCRETION
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IN REGARD TO COMPLYING WITH THE MILLSTONE UNIT 2' TECHNICAL SPECIFICATION 3.4.10 REACTOR COOLANT SYSTEM - STRUCTURAL INTEGRTTY AND THE RE0 VEST OF APPROVAL TO USE AN ALTERNATIVE METHOD OF i'
COMPLIANCE WITH THE ASME CODE. SECTION XI. FOR THE STRUCTURAL INTEGRITY OF AN ASME CLASS 3 COMPONENT.
NORTHEAST NUCLEAR ENERGY COMPANY i
THE CONNECTICUT LIGHT AND POWER COMPANY i
THE WESTERN MASSACHUSETTS ELECTRIC COMPANY i
MILLSTONE NUCLEAR POWER STATION. UNIT NO. 2
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DOCKET NO. 50-336 l
l l.0 BACKGROUND l
By letter dated March 26, 1993, the Northeast Nuclear Energy Company (NNECO or the licensee) submitted a Request for Enforcement Discretion in regard to meeting the requirements of Millstone Unit 2 Technical Specification (TS) 3.4.10, The Reactor Coolant System - Structural Integrity Limiting Condition for Operation and a request for approval, pursuant to 10 CFR 50.55a(a)(3)(ii),
j to use an alternative method of compliance with Section XI of the ASME Code for the structural integrity of a ASME Class 3 component. Technical Specification 3.4.10 and 10 CFR 50.55a(g)(4) both require the ASME Code' Class 1, 2, and 3 structures, systems and components meet the inservice testing and structural integrity requirements ASME Code Section XI during their service life. The request for discretion is made to allow the licensee time to implement an interim repair to a section of service water piping, component 2"-HUD-130. which supplies cooling water to Cooling Coils X-181A and X-181B in i
the West 480 Volt AC Vital Switchgear Room.
930420033s 930414 PDR ADOCK 05000336 P
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The licensee had discovered earlier, on January 25, 1993, that a socket weld, I
W-1, in component 2"-HUD-130 had displayed signs of weeping during hydrostatic l
testing, following a modification to the system. The hydrostatic test of the section in question was performed after the licensee had returned the unit to full power and had phased the unit to the grid on J'nuary 13, 1993. The licensee had decided to delay the hydrostatic test since repair / replacement J
activities were delayed for the outlet side of the system. On February 24, 1993, the licensee requested relief of the ASME Code,Section XI requirements pursuant to the guidance of Generic Letter (GL) 90-05, " Guidance for l
Performing Temporary Non-Code Repairs of ASME Code Class I, 2, and 3 Piping."
On March 22, 1993, during a telephone conference with the licensee, the NRC staff expressed that the guidance of GL 90-05 was not applicable to this situation since the leak was detected during the performance of a hydrostatic test, and the initial structural integrity of the weld had not been demonstrated following repair / replacement activities. The NRC staff, j
therefore, took the position that the licensee was not in compliance with the requirements of TS 3.4.10 and 10 CFR 50.55a(g)(4).
i The licensee has stated, under the current circumstances with the unit at i
power and on-line with the grid, that the electromotive forces generated during a Code (weld) repair of the component could affect the operability of the safety related Vital 480 Volt AC buses located in the Switchgear Room.
j The licensee believes that since the component does not exhibit " weeping" at operating pressure, the component is operable during normal operating conditions. The licensee, therefore, believes that the hardship provision of 10 CFR 50.55a(a)(3)(ii) applies in this case, and that enforcement discretion is warranted with respect to complying with the requirements of TS 3.4.10.
In this case,10 CFR 50.55a(a)(3)(ii) allows the licensee to propose alternatives to the requirements of 10 CFR 50.55a(g) if compliance wit' the specified requirements would result in hardship or unusual difficui.y without a compensating increase in the level of safety and quality.
2.0 EVALUATION The licensee's submittal indicates that the root cause of the pinhole leak is a lack of fusion between the weld and the socket welded tee 2"-HUD-130. This component supplies service water to Cooling Coils X-181A and X-1818 in the West Vital AC Switchgear Room. This component is made from a 90-10 Cu-Ni SB466-706 material, with a 100 psig design pressure. The leak was detected during a 110 psig hydrostatic test (110% of design pressure) of the component, following a modification to the system (AWO M2-92-17685). The hydrostatic test of the component was performed after the unit had been returned to power and placed on-line with the grid.
In order to meet the requirements of 10 CFR 50.55a(a)(3), the licensee proposes the following alternative plan:
1 perform a structural integrity evaluation in accordance with the branch reinforcement methodology of ASME Code Section III in order to show that component 2"-HUD-130 will maintain its structural integrity during design basis conditions under its degraded condition l
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1 monitor component 2"-HUD-130, as a minimum frequency, once per operating shift design and install an engineering clamp around the " weeping" weld in l
component 2"-HUD-130 as an appropriate measure to enhance the structural integrity of the system perform an ASME Section XI Code repair in accordance with the provisions of Article IWA 4000 at the next unit outage of 10 or more i
days duration The licensee's proposal for the use of an engineered clamp as a temporary l
replacement for assuring the structural integrity of the degraded component is acceptable. The staff believes that, in this case, a temporary replacement would alleviate concerns regarding the structural integrity of component 2"-
HUD-130; the compensatory examinations by plant operators to monitor 2"-HUD-130 once per shift will prove useful in assessing the component for further signs of leakage or structural degradation. This compensatory measure is acceptable during the period of discretionary enforcement to minimize the risk of a pipe rupture. The staff is unable to determine the applicability of an area reinforcement analysis for a socket welded "T" connection. The NRC staff evaluation of the acceptability for continued operation during the period of l
discretionary enforcement for the degraded joint is based on the minimal leakage observed and the compensatory measures put in place by the licensee, rather than the area reinforcement analysis.
The staff does not agree that branch reinforcement analysis is applicable to a socket welded tee.
3.0 CONCLUSION
The licensee has provided a reasonable alternative program for monitoring leakage and integrity of component 2"-HUD-130.
As a Code repair in the Switchgear Room would require a shutdown of the unit, the staff finds that the licensee's proposed program serves as an acceptable alternative and, pursuant to the provisions of 10 CFR 50.55a(a)(3)(ii), compliance with the requirements of 10 CFR 50.55a(g)(4) for component 2"-HUD-130 would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The approval of this alternative in no way relieves the licensee from complying with 10 CFR 50.55a(g)(4), which requires ASME Code Class 1, 2, and 3 i
l components to meet the inservice testing and structural integrity requirements of ASME Code Section XI after a shutdown of sufficient duration of 10 days or more to affect a Code repair / replacement of component 2"-HUD-130.
Principal Contributor:
J. Medoff Date: April 14, 1993 i
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