ML20116E663

Discusses Followup Actions to SER for Amend 90 to License DPR-65.New Steam Line Break Generator Tube Rupture Analysis Will Be Submitted for Review 4 Months After Startup from Current Refueling Outage

ML20116E663
Person / Time
Site:	Millstone
Issue date:	04/22/1985
From:	Counsil W, Sears C NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	John Miller, Sears C NORTHEAST UTILITIES, Office of Nuclear Reactor Regulation
References
A03722, A3722, B11518, TAC-54199, NUDOCS 8504300362
Download: ML20116E663 (2)

Text

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(203) 665-5000 April 22,1985 Docket No. 50-336 B11518 A03722 Director of Nuclear Reactor Regulation Attn:

Mr. James R. Miller, Chief Operating Reactors Branch #3 U. S. Nuclear Regulatory Commission Washington, D. C. 20555

References:

(1)

K. L. Heitner letter to W. G. Counsil, dated December 30, 1983.

(2)

W. G. Counsil letter to J. R. Miller, dated September 14, 1984.

(3)

W. G. Counsilletter to J. R. Miller, dated January 2,1985.

Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Followup Actions to Amendment No. 90 to Operating License No. DPR-65 The NRC Staff forwarded Amendment No. 90 to Facility Operating License No.

DPR-65 in Reference (1). The amendment authorized Cycle 6 operation for Millstone Unit No. 2.

The NRC Safety Evaluation Report (SER) accompanying the amendment addressed various aspects of the evaluations submitted to support Cycle 6 operation. The Staff documented several concerns relating to the analysis of steam line breaks and steam generator tube ruptures. The Staff's concerns included the possible effect of a loss of offsite power coincident with these events and the mixing factors considered in the steam line break analysis.

Northeast Nuclear Energy Company (NNECO) responded to the Staff concerns, in these areas, by References (2) and (3). These submittals discussed conclusions y

drawn from Cycle 5 analyses regarding the effects of loss of offsite power and a r

current evaluation of variations in assumed mixing within the reactor vesselinlet and outlet plenums. In the latter, Reference (3) reported that nucleate boiling did not occur and therefore Departure from Nucleate Boiling Ratios (DNBRs) were not calculated.

The information provided by References (2) and (3) was discussed in telephone conference calls involving NNECO and NRC Staff personnel on February 19 and 20, 1985.

In these conversations, NRC reviewers requested additional l}) g01 -

g information describing the bases for NNECO's conclusions.

NRC personnel expressed their intention to independently review the underlying analyses to 8504300362 850422 PDR ADOCK 05000336 p

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verify the conclusions. NNECO agreed to supply a schedule for providing the requested information. In considering the questions raised in these conference calls, NNECO has concluded that the optimal use of its resources would be to perform new analyses addressing NRC concerns directly.

NNECO will submit raw steam line break and steam generator tube rupture analyses for Millstone Unit No. 2.

These analyses will consider loss of offsite power and the effects of various mixing assumptions. These new analyses will be submitted to NRC' for review four months after startup from the current refueling outage.

We trust that this commitment will resolve any remaining NRC concerns.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY W. b. _.

W. G. Counsil Senior Vice President By: C. F. Sears Vice President 1

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