ML19322C365
| ML19322C365 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco, Crane |
| Issue date: | 04/07/1978 |
| From: | Stella V Office of Nuclear Reactor Regulation |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19322C361 | List: |
| References | |
| TASK-TF, TASK-TMR NUDOCS 8001160901 | |
| Download: ML19322C365 (2) | |
Text
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W bA p m'o, yp3 UNITED STATES
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WASHWG TON. D. C. 20555
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April 7,1978 Docket No. 50-312 MEMORANDUM FOR:
Darrell G. Eisenhut, Assistant Director for Systems and Projects Brien Grimes, Assistant Director for Engineering and Projects FROM:
Victor Stello, Jr., Director, Division of Operating Reactors
SUBJECT:
TECHNICAL SPECIFICATIONS FOR REACTOR COOLANT SYSTEM HEATUP AND C00LDOWN RATES AND PRESSURE-TEMPERATURE LIMITS The recent severe cooldown transient at Rancho Seco Unit No.1 (March 20, 1978) has served to point out a significant deficiency in the present custom and standard technical specificaticns for RCS heatup/cooldown rates and pressure-temper,ture limits.
The deficiency is that there is no provision which requires prompt shutdown and NRC 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.
As noted in the attachment the consequences of the Rancho Seco cooldown were significantly ameliorated because the transient occurred fairly early in reactor life.
By extension, however, it follows that the consequences might have been more severe if the transient had occurred after the reactor vessel had received a higher neutron exposure.
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-i In order to address these two problems, it is requested that you:
1.
(ADEP) Develop and recomend a criterion to be included in facility technical specifications which c"1 define when a violation of RCS heatup or cooldown rates or pressure-temperature limits will require plant shut-down and NRC approval prior to resumption of operation, and 2.
(ADSP) Evaluate the susceptibility of nuclear plants to cooldown transients which could cause violation of, the technical specification limits, and recommend any design or procedural modifications that are 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 memorandum, and the recommendations resulting from review of Part 2 be available within 180 days.
,e m
I Victor Stello, Jr., Director Division of Operating Reactors
Attachment:
D. Eisenhut memo to V. Stello, Jr.,
of March 30, 1978, Sub. " Rancho Seco Nuclear Generating Station -
Evaluation of the NSS Cooldown Transient - Docket No. 50-312."
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