ML19344D183

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Discusses Slightly Diminished Capacity of Charging Pumps to Inject Concentrated Boric Acid Into RCS Under Test Conditions.Change in Peak Clad Temp Due to Smaller Charging Pump Flow Is Not Significant Enough to Be Reportable
ML19344D183
Person / Time
Site: Millstone Dominion icon.png
Issue date: 02/29/1980
From: Counsil W
NORTHEAST NUCLEAR ENERGY CO.
To: Reid R
Office of Nuclear Reactor Regulation
References
TAC-11348, TAC-11561, TAC-12505, TAC-42846, NUDOCS 8003110489
Download: ML19344D183 (2)


Text

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February 29, 1980 Docket No. 50-336 Director of Nuclear Reactor Regulation Attn: Mr. R. Reid, Chief Operating Reactors Branch #4 U. S. Nuclear Regulatory Ccamission Wachington, D. C. 20555

References:

(1) R. Reid letter to W. G. Counsil dated May 12, 1979.

(2) W. G. Counsil letter to R. Reid dated March 22, 1979 (3) W. G. Council lutter to R. Reid dated August 31, 1979 Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Charging Pumps Milletone Nuclear Power Station, Unit No. 2 is equipped with three (3) positive displacement charging pumps as part of the Chemical and Volume Control System (CVCS). These pumps are designed to perform various functions, one of which is to inject concentrated boric acid into the Reactor Coolant System (RCS) under emergency conditions.

A percentage of this charging flow has been taken credit for in Millstone Unit No. 2, Small Break Loss-of-Coolant Accident Anal / sis as authorized by the NRC Staff in Reference (1). Presently, one half of the capacity of one charging pump, 22 gpn, is taken credit for in the Millstone Unit No. 2 Small Break LOCA Analysis as documented in References (2) and (3). The design capacity of the charging pumps utilized at Millstone Unit No. 2 is 4h gpm as reported in the FSAR. This is the rated flow at ideal conditions.

Recent in-service inspections (ISI) have shown that under test conditions, these pumps deliver approximately 43 spm.

Northeast Nuclear Energy Company (NNECO) has reviewed the discrepancy pursuant to the reporting requirements of the Millstone Unit No. 2 Technical Specifications Section 6.9.1.8 and 10CFR50, Appendix K. For the purposes of performing this evaluation, a conservative value of kl.h gpm was assumed for assessing the impact on existing Small Break LOCA Analysis.

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The flow rate of 41,4 gpm is the minimum acceptable flow rate permitted by the ICI program for these pumps. The QA Category 1 evaluation performed concerned the sensitivity of Peak Clad Temperature (PCT) to small changes in high pressure flow in the Omall Break IOCA Analysis.

The results of the sensitivity study demonstrate that the exIected change in PCT due to the smaller flow rate, assumed to be delivered from the charging pumps, would be less than 10 F. It is also . ted that for the worst-ease break size of 0.1 ft2, the calculated PCT is 1971 b , well below the 2200 F limit.

This calculated peak occurs approximately twenty four (24) minutes after the start of the accident. The above discrepancy results in the loss of only 31 gallons during the period of interest.

Based on this engineering evaluation, UNECO has determined that the change in PCT as a result of the smaller charging pump flow rate is not termed significant pursuant to Technical Specification 6.9.1.8, as clarified by 10CFR50, Appendix K, Paragraph lb, and as such, is not reportable.

It is NNECO's intention to have future ECCS safety analyses performed utilizing a more conservative bounding value for charging pump flow rate.

A reanalysis for both small and larger break LOCA vill be performed for the upcoming reload, the results of which will be reported in the reload submittals scheduled for docketing on April 1,1980. This letter is provided for informational purposes.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY

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. f t t /b3t W. G. Counsil Vice President