ML20238C400

Safety Evaluation Supporting Proposed Mod to 10CFR50.62, ATWS Rule

ML20238C400
Person / Time
Site:	Cooper
Issue date:	12/23/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20238C398	List: ML20238C396 ML20238C400
References
NUDOCS 8712300254
Download: ML20238C400 (2)

Text

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W ASHINGTON, D. C 20555

%...../ ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO 10 CFR 50.62, ATWS RULE NEBRASKA PUBLIC POWER DISTRICT COOPER NUCLEAR STATION DOCKET NO. 50-298

1.0 INTRODUCTION

By letter dated April 8,1987 (NLS 8700187), the Nebraska Public Power District (NPPD, the licensee) submitted a description of its plans for implementing the requirements of 10 CFR 50.62 at Cooper Nuclear Station.

Additional information was provided by NPPD letter dated November 18, 1987 (NLS 8700601). The proposed Standby Liquid Control System (SLCS) is designed to supply a minimum of 67 gpm of sodium pentaborate solution (13 weight percent sodium pentaborate) to the reactor vessel'to meet ATWS requirements.

2.0 EVALUATION The system description provided by NPPD for Cooper has been reviewed by the staff against the requirements of the ATWS Rule (10 CFR 50.62), and Generic Letter 85-03, " Clarification of Equivalent Control Capacity for Standby Liquid Control Systems," dated January 28, 1985. The licensee will maintain the boron enrichment of 19.8 atom percent of B-10, and proposes to supply 67 gpm of 13 weight percent sodium pentaborate solution to the reactor vessel ~. Since the Cooper vessel is 218 inches in diameter, the aforementioned flow / concentration combination satisfies the ATWS Rule equivalency requirement which is based on 86 gpm,13 weight percent sodium pentaborate,19.8 atom percent B-10, and a 251 '

inch diameter vessel, as discussed in Generic Letter 85-03. The proposed design is therefore acceptable relative to equivalency requirements.

l The Cooper SLCS design will incorporate separate suction lines to each pump, ,

for the purpose of avoiding reinforcing pulsations which' are common'in single suction line designs. Under this condition,-a revised system relief valve pressure setpoint of 1300 psi which includes a 70 psi margin to pump discharge pressure is acceptable.

The licensee stated in its submittal that the Technical Specification figure j on Sodium Pentaborate Solution Volume Concentration requirements and the-identification of the relief valve setpoint will be. changed to reflect the proposed modification. In addition, surveillance and positive verification.

should be performed periodically to' assure that the correct concentration is j maintained. These surveillance requirements as well as periodic ~ verification i of the 67 pgm flow rate will be included in the plant Technical Specifications.

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3.0 CONCLUSION

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The description of the proposed SLCS operation provided by NPPD for the Cooper Nuclear Station, in letters dated April 8,1987 and November 18, 1987, is acceptable because it is consistent with the equivalency requirements of 10 CFR 50.62.

Dated: December 23, 1987 Principal Contributor: M. McCoy l

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