ML20086Q415

SR-S2-75-01:during Refueling Operation,Cladding Perforation Detected on Fuel Assembly N-10.Fuel Assembly Can Be Safely Operated to end-of-Cycle 2 Design Burnup

ML20086Q415
Person / Time
Site:	Surry
Issue date:	06/02/1975
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML20086Q378	List: ML20086Q392 ML20086Q415 ML20086Q472
References
SR-S2-75-01, SR-S2-75-1, NUDOCS 8402270540
Download: ML20086Q415 (3)

Text

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O O SPECIAL REPORT SR-S2-7 5-0.1_

REPORT ON FUEL ASSDtBLY N-10 DOCKET NO. 50-281 LICENSE NO. DPR-37 t JUNE 2, 1975, SURRY POWER STATION VIRGINIA ELECTRIC AND POWER COMPANY-j PDR .-

. . O O

1. INTRODUCTION During the refueling operation for Cycle 2 of Surry Unit No. 2, a cladding perforation was detected on fuel assembly N-10.

II.

SUMMARY

OF OCCURRENCE During binocular visual inspection of fuel assemblies in accordance with procedures estabished for the first refueling of Surry Unit No. 2, gas bubbles were noted coming from one of the outer fuel rods (third rod from the left on face No. 3, between grids 3 and 4) in fuel assembly N-10.

l Fuel assembly N-10 was given a more detailed visual examination using I l

'IV inspection equipment and videotape. This inspection established that the cladding was perforated with some visual evidence of local hyd . ding.

The defect area is generally circular with the perforation being approximately 0.1 inches in diameter and the surrounding hydride area being approximately 0.25 inches in diameter.

Reactor coolant activity levels during the first cycle showed a slight increase, typical of a few failed rods, about two months after the beginning of operation. Initial I-131 activity levels in the ' reactor coolant were approximately 10-4 pCi/ml at the beginning of Cycle 1 (March 7,1973),

increasing to an average of approximately 5 x 10-3 pCi/ml (equivalent to at most a few perforated rods) by the end of April 1973 and continuing at this 1cvel throughout the remainder of Cycle 1 (shutdown of Cycle 1 occurred on April 26, 1975). Since coolant activity levels did not increase between May 1973 and the end of the cycle, it is reasonable to assume that the perforated rod observed in assembly N-10 is one of the few defects that developed during the first month or two of operation.

< _n_ v

. . O O The visual examination data available on the defect have been reviewed with Westinghouse, the fuel designer. Westinghouse has concluded that there is no reason why fuel assembly N-10 should not be operated through Cycle 2 as scheduled. A review of previous operating experience in other reactors with known defected fuel revealed no evidence of propagation of similar failures, and in fact showed no evidence that similar perforations led to gross failure of the affected rod.

A review of quality control / quality assurance records of fuel assembly N-10 revealed no deviations or discrepancies contributing to this defect.

Visual inspection of other fuel assemblies revealed no other defected fuel rods.

III. CONCLUSION It is concluded from the above that fuel assembly N-10, which has been included in the Cycle 2 loading for Surry Unit No. 2, can be safely operated 1

to its end-of-Cycle 2 design burnup. l The above conclusions have been reviewed by both Westinghouse and 'l Vepco personnel (including Vepco's independent consultant) and are con-curred with by all parties. The results and recommendations have also been reviewed and concurred with by the Station and System Nuclear Safety. and Operating Committees.

&. .I