ML17037B538

Letter Requesting Information on Commitment to Modify Plant to Provide a Recirculation Pump Trip and Schedule for Submitting the Detailed Design for NRC Approval, Schedule for Procurement, and Schedule for Completion .

ML17037B538
Person / Time
Site:	Nine Mile Point
Issue date:	09/01/1976
From:	Stello V Office of Nuclear Reactor Regulation
To:	Rhode G Niagara Mohawk Power Corp
References
WASH-1270
Download: ML17037B538 (4)

Text

I SEP 1 876 I

Docket Ho. 50-,220 Hiagar a mohawk Pointer Cor poration ATTN:

Hr. Gerald K. Rhode Vice President - Engineering 300 Erie Boulevard West

Syracuse, Hew York 13202 Gentlemen:

RE:

Bine ffile Point, Unit Ho.

1 Distribution

~ocket File,

.NRC PDR Local PDR ORB g3 File KRGoller TJCarter OELD'IaE g)

GLear JGuibert CParrish DElseniludt TBAbernathy, DTIE JRBuchanan ACRS (16)

DRoss YRooney YStello In September

1973, The Atomic Energy Commission published the "Technical Report on Anticipated Transients Without Scram for Water-Cooled Power Reactors"

{WASH-1270) establishing acceptance criteria for anticipated transients without scram

{ATffS).

These criteria were developed because we believed that a fully satisfactory methodology for analyzing the reliability of protection systems from the standpoint of common mode failures was not available at that time, that these types of failures had occurred in protection systems and that the potential consequences of some postulated anticipated transients without scram might be hazardous to'the public.

Subsequent to the publication of LfASH-1270, we met with your Nuclear Steam Supply System Vendor, the General Electric Company {GE),

on a regular basis and reviewed their evaluation model, the results of analyses of anticipated transients without scram, the diversity of the systems relied upon to mitigate the consequences of A'NS, and the sus-ceptibility of the Reactor Protection System to common mode failure.

In January of 1976, the status of our ATItfS review and the generic analyses and proposals of GE were discussed before the ACRS.

A status report de-scribing the information discussed is enclosed.

13e requested from 'GE additional information needed to complete our generic review, and they responded by letter dated July 2, 1976.

t/e intend to complete our review of their report and detemine any necessary plant changes as soon as practicable.

In the interim, based on our review as decribed in the status

report, we believe that the addition of a recirculation pump trip >~ould ORI ICd~

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significantly limit the consequences of an ATk~S event.

GE took credit for a recirculation pump trip in the AA/S analysis they provfded us and i4fch you referenced.

A trip of the recirculation pumps fn the event of'igh reactor vessel pressure has the effect of causing an increase in the moderator voids fn the reactor core.

A substantial negative reactivity

results, and the povier and pressure surges that might otherwise occur fn the most limiting transient (HSIY closure) are substantially reduced.

He have found that a recirculation pump trip similar fn design to the trip described fn 4he enclosed report and in General Electric Report NEDO-20626 v>ill provide substantial additional protection which is required for the public health and safety.

Therefore we request that you inform us of your cormftment to modify your plant to provide a recirculation pump trip, and the schedule for doing so.

He wfll review your detailed design to assure that the pump trip conforms to current regulatory practice and. the description in the enclosed status report.

At least 90 days before your scheduled instal-lation, you should propose Technical Spec)ffcatfons for pressure and level setpoints for your recirculating pump tr)ps and for surveillance requirements.

Please provfde us with the above information >~fthfn 30 days of'eceipt of this letter, including your schedule for submitting the detailed design for NRC approval, your schedule for procurement, and your schedule for completion of mIodiffcations.

Sincerely, Original signed

~y

Enclosure:

StatuE Report on Anticipated Transients (Jithout Scram for GE Reactors - December 9, 1975 Victor Stello, Jr., Director Division of Operating Reactors CC:

Arvin E. Upton, Esquire

LeBoeuf, Lamb, Leiby 8 tfacRae 1757 H Street, "1.

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Washington, D.

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20036 Anthony Z. Rofsman, Esquire Rofsman, Kessler and Cashdan 1712 N Street, N. )I.

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