ML20154P923

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Discusses Rev to Abnormal Transient Procedure Atp 1210-10 Re Guidance in Event That Reactor Coolant Pumps Not Tripped Immediately Upon Loss of 25 F Subcooling Margin After Loca. B&W Analysis Indicates Tripping within 10 Min Acceptable
ML20154P923
Person / Time
Site: Three Mile Island Constellation icon.png
Issue date: 05/27/1988
From: Hukill H
GENERAL PUBLIC UTILITIES CORP.
To:
NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
TASK-2.K.3.05, TASK-TM C311-88-2062, GL-86-05, GL-86-5, NUDOCS 8806060127
Download: ML20154P923 (2)


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GPU Nuclear Corporation I G u. Nuclear  : ema=

o Middletown, Pennsylvania 17057 0191 l

717 944 7621 TELEX 84 2386 Writer's Direct Olal Nurnber:

May 27, 1988 C311 2062 J

U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:

Three Mile Island Nuclear Station, Unit 1 (TMI-1)

Operating License No. DPR-50 Docket No. 50-289 Mcdification to Reactor Coolant Pump Trip Criterion GPU Nuclear Corporation recently has implemented a change to Abnormal Transient Procedure ATP 1210-10, regarding guidance in the event that reactor coolant pumps are not tripped immediately upon loss of 25*F subcooling margin following a loss of coolant accident.

The requirement to trip the pumps immediately upon an indicated loss of subcooling margin provides assurance that limits of 10 CFR 50.46 will be mt.

This procedural requirement has not been changed. The procedural revision specifies that if the 25'F subcooling margin is lost and all operating reactor l coolant pumps are not tripped within ten minutes, then one reactor coolant pump per loop is to be left on for at least two hours. Previously one pump was to be left on per loop if all reactor coolant pumps were not tripped within two minutes. Best-estimate analyses performed by Babcock and Wilcox and found acceptable by the NRC (Reference 1) have demonstrated that tripping of the reactor coolant pumps within 10 minutes of loss of subcooling margin results in acceptable peak clad temperatures. 1 Since tripping the pumps is acceptable it is the preferred action to reduce risk of damage to the pumps. The pumps would thus remain available for restart if subcooling margin is restored, or to treat subsequent inadequate core cooling conditions should they occur.

This procedure change is in accordance with HRC guidance for justification of l manual reactor coolant pump trip provided in Appendix A to Generic letter l 86-05 (Reference 1). l i

GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation

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C311-88-2062 May 27, 1988 This letter augments information provided by GPUN in our response to Generic Letter 86-05 (Reference 2), and is submitted for information. The NRC

. conclusions in Reference 3 are unaffected. No NRC response is expected.

Sincerely, 4

. D. kill Vice President and Director, TMI-1 HDH/SMK:fg cc: J. Stolz - NRC R. Hernan - NRC R. Conte - NRC R. Borsum - BAW

References:

(1 ) Generic Letter 86-05, "Implementation of TMI Action Item i II.K.3.5 Automatic Trip of Reactor Coolant Pumps," dated l

May 29,1986.

(2) GPUN Letter 5211-86-2123, "Response to GL 86-05 Implenentation of TMI Action Item II.K.3.5," dated July 31, ,

1986.

(3) NRC Letter 5211-87-3169, "Safety Evaluation Relating to Implenentation of THI Action Item II.K.3.5 (Reactor Coolant Pump Trip) in Regard to TMI-l (TAC 49698)," dated August 11, 1987. .

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