ML20138D594

Safety Evaluation Granting Relief from Repair Requirements of ASME Code Section XI in Order to Perform Temporary Noncode Repair to 18 Inch Portion of Nuclear Closed Cycle Cooling Sys

ML20138D594
Person / Time
Site:	Crystal River
Issue date:	02/09/1993
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20138D587	List: ML20138D582 ML20138D594
References
NUDOCS 9302220458
Download: ML20138D594 (2)

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[. g(fn g 3 I NUCLEAR REGULATORY COMMISSION W ASHINGTON, D. C. 205$5 k.....

SAFETY EVALVATION 8) THE OFFICE OF NUCLEAR REACTOR REGULATION FLORIDA POWER CORPORATION RE0 VEST FOR REllEF FROM ASME CODE REPAIR RE0VIREMENTS FOR ASME CODE CLASS 3 PivlNG CRYSTAL RIVER N0. 3 DOCKET NO. 50-302 1.0 JNTRODUCTION By letter dated November 13, 1992, with supplemental information dated November 30, 1992, Florida Power Corporation, (FPC, the licensee), requested relief from the repair requirements of ASME Section XI in order to perform a temporary non-Code repair to the Nuclear Closed Cycle Cooling (SW) system at Crystal River Unit 3.

i The purpose of the temporary repair was to patch two l l small leaks on an 18-inch diameter SW suction header. These leeks were the '

result of external corrosion of the subject pipe. The subject pipe and system l

are classified as AStiE Code Class 3. It is a moderate energy safety-related '

system that conveys closed cooling water to a wide variety of safety-related equipment throughout the unit. Because the leaks cannot be isolated, FPC determined that a Code repair is impractical during unit operation and would require shutdown of the unit for a significant t-ime. The relief request was submitted in accordance with the provisions of Generic Letter (GL) 90-05.

This system was the subject of a separate relief request dated November 6, 1992. The two leaks described above were discovered during the augmented examination subsequent to the first event.

2.0 DISCUSSION Flaw assessments and analysis of the corroded section of pipe containing the two stall leaks were performed by the licensee in accordance with the provisions of the GL. The flawed pipe meets the structural criteria of the GL. A temporary patch, consisting of a rubber seal and a pipe clamp, was l proposed as a leak mitigating measure, consistent with the GL.

The supplemental information to this relief request (dated November 30, 1992, addressed action initiated to alleviate the corrosion rate of this system so that presently thinned but operable sections do not become substantially degraded prior to the planned spring 1993 overhaul. One tause of the corrosion was attributed to a past practice of draining adiacent sea water heat exchangers to the trench containi:ig the subject line. This operation was performed when maintenance actions were required on the heat exchangers.

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Maintenance activities have been modifSd to assure that further sea water wetting of the subject pipe is avoided.

Visual inspection of the pipe'will be conducted once per shift to detect increased leakage and to monitor the water level in the trench to prevent-wetting of the pipe. The trench will also be cleared of water as necessary, approximately once per day, to aid in this activity.

Actions are under consideration to reduce the formation of condensation on the pipe. This includes control of SW water temperature, applying. insulation'and drying.

Routine UT inspections of the worst five areas of the pipe will be conducted every 45 days. This will aid in assessing the ongoing corrosion rates.

Dee to erosion of the inside of portions of this system, the licensee had existing plans to replace significant portions during the forthcoming outage.

At that time, the affected portions of the pipe with temporary repairs will also be replaced.

3.0 CONCLUSION

Based on our review, we have determined that Code repair requirement 4 h this case are impractical, as defined in GL 90-05, and that the proposed ;:mporary repair is acceptable. Our basis for this determination is that the leaks-cannot be isolated to perform a repair in conformance with the Code requirements and thus would require a unit shutdown. We find the fla'wed '

piping to have adequate structural integrity. Our basis for this. finding is that the flaws meet the acceptance criteria for flaws evaluated according to the through-wall approach specified in GL 90-05.

Furthermore, the licensee has committed to the guidance provided in GL.90-05,.

which will reasonably assure structural integrity and protect public health and safety. Pursuant to 10 CFR 50.55a(g)(6)(i), and consistent with the guidance in GL 90-05, the Commission herewith grants the requested relief i until the maintanance outage currently planned for the spring of 1993,- and requires FPC to perform the above-noted actions-and inspections. We have determined that they are authorized by law and will not endanger life-or.

property or the common defense and security and are otherwise in the public-interest, given due consideration to the burden upon the licensee and fac.lity, that could result if the Code requirements were imposed on the facility. -

Principal Contributor:

G. Hornseth, EMCB Date: February 9, 1993

t y Memorandum Dated February 9, 1993 Distribution Docket File NRC & Local PDRs P0ll-2 RF S. Varga G. Lainas H. Berkow H. Silver E. Tana OGC G. u'rnseth ACha (10)

M. Sinkule, Ril

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