ML19322D176

Requests Recommendation Re Review of Tech Specs for RCS Heatup & Cooldown Rates & pressure-temp Limits within 60 Days.Forwards NRC 780330 Memo Re Evaluation of NSS Cooldown Transient at Rancho Seco.W/O Encl

ML19322D176
Person / Time
Site:	Rancho Seco, Crane
Issue date:	04/07/1978
From:	Stello V Office of Nuclear Reactor Regulation
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
TASK-TF, TASK-TMR NUDOCS 8002100017
Download: ML19322D176 (2)

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April 7,1978 Dacket !!o. 50-312 MEM0PR!DUM FOR:

Darrell G. Eisenhut, Assistant Director for Systems and Projects Brian Grimes, Assistant Director for Engineering and Projects FROM:

Victor Stello, Jr., Director, Division of Operating Reactors SU3 JECT:

TECHNICAL SPECIFICATI0 tis FOR REACTOR COOLANT SYSTEM HEATUP AND C00LDOUN RATES AND PRESSURE-TEliPERATURE LIMITS The recent severe cooldown transient at Rancho Seco Unit f!o. 1 (fiarch 20, 1978) has served to point out a significant deficiency in the present custom and standard technical specifications for RCS heatup/cooldown rates and pressure-temperature limits.

The deficiency is that there is no provision which requires prompt shutdown and !!RC review following a substantial violation of these limits.

Such a require-ment would appear to be appropriate under such conditions since gross violations of these limits could threaten reactor, vessel integrity.

At the same time, it is probably true that minor violations of the limits do not necessarily warrant prompt shutdown and NRC approval of restart.

One problem, therefore, is to define the boundary between a minor and a major violation of these limits and to specify the required action for each class of violation.

A second problem is determining the susceptibility of nuclear plants to major cooldown transients such as that experienced by Rancho Seco and minimizing this susceptibility.

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consequences of the Rancho Seco cooldown were significantly ameliorated I

because the transient occurred fairly early in reactor life.

By extension, however, it follows that the consequences might have been

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more severe if the transient had occurred after the reactor vessel bd received a higher neutron exposure.

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j-In order' to address these tito problems, it is requested that you:

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Develop and recorrnend a criterion to be included in

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facility technical specifications which will define when a violation of RCS heatup or cooldown rates or.

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g pressure-temperature limits will require plant shut-

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down and NRC approval prior to resumption of operation, 7p and

2...(ADSP)' -Evaluate the susceptibility of nuclear plants to cooldown transients which could cause violation of

.i the technical specification limits, and recommend L~

any design or procedural modifications that are-

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needed to provide reasonable assurance that such limits will not be significantly exceeded.

It is requested that the recommendation resulting' from review of'Part 1 of.the above request be available within 60 days of the date of this

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memorandum, and the recommendations resulting from review of Part 2 be available within 180 days.

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Victor Stello, Jr., Director Division of Op.erating Reactors EE

Attachment:

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D. Eisenhut memo to V. Stello, Jr.,

N of March 30, 1978, Sub. " Rancho Il Seco Nuclear Generating Station -

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Evaluation'of the NSS Cooldown lI^

Transient - Docket No. 50-312."

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