L-80-431, Forwards Analysis of Natural Circulation Cooldown W/O Upper Head Voiding for St Lucie Unit 1, in Response to NRC 801017 Request for Info Re 800611 Natural Circulation Cooldown Event
| ML17209A500 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 12/30/1980 |
| From: | Robert E. Uhrig FLORIDA POWER & LIGHT CO. |
| To: | Clark R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17209A501 | List: |
| References | |
| L-80-431, NUDOCS 8101060288 | |
| Download: ML17209A500 (5) | |
Text
REGULATO INFORMATION DISTRIBUTION STEM (RIDS)
ACCESSION'BR:8101060288 DOC ~ DATEt 80/12/30 NOTARIZED; NO FACIL'.50 335 St'ucie Planti,Unit 1< Flor ida Power 8 Light Co>
AUTH ~ NAME AUTHOR AFFILIATION UHRIGrR,E, Florida Power 8 Light Co ~
RECIP NANEi RECIPIENT AFFILIATION CLARKpR,AD Operating Reactors Branch 3
C
SUBJECT:
Forwards "Analysis of Natural Circulation Cooldown li/o Upper'-
Head Voiding for St Lucie Unit 1~" in response to NRC 801017 request for info re 800611 natural circulation cooldown events DOCKET 05000335 NOTES:
DISTRIBUTION CODE:
A001S COPIES RECEIVED: LTR ENCL SIZE:. Rk/I TITLE: General Distribution for after Issuance of Operating License RECIPIENT ID CODE/NAME ACTION:-
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OF FLORIOA POWER 8 LIGHTCOMPANY December 30, 1980 L-80-431 Office of Nuclear Reactor Regulation Attention:
Mr. Robert A. Clark, Chief Operating Reactors Branch k'3 Division of Licensing U.
S.
Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Clark:
Re:
St.
Lucie Unit 0'1 Docket No. 50-335 Natural Circulation Cooldown The NRC letter dated October 17, 1980 requests additional information concerning our response to your question regarding the June 11, 1980 St. Lucie Natural Circulation Cooldown Event.
Your basic concern appears to be that we have not presented an analytical,ly justified procedure which would result in a natural circulation cooldown without voiding in the reactor vessel
- head, and which would at the same time stay within our technical specification limit for condensate storage.
In previous correspondence, we have shown that the drain and fill method utilized during the June ll, 1980 event is a method which we can safely use to cool down the reactor on natural circulation while remaining well within the cooldown limits as specified.in the technical specifications.
However, in an attempt to minimize the need for drain and fill cycles during the operational life of St. Lucie Unit 1, we will make certain alterations to the procedure governing natural circulation cooldown.
The purpose of the changes will be to extend the time the reactor remains at 325O before dropping pressure to shutdown cooling conditions.
This will allow the temperature of the water in the upper head to approach that of the hot leg, thereby allowing depressurization without void formation.
As stated in our September 16, 1980 letter, we revised 'our emergency operating procedure to require a cooldown rate of 25-30OF/hour, with the cooldown to be stopped at approximately 325OF RCS temperature for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
This revision was based on the best information available at the time and was felt to include adequate cpnservatisms.
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Robert A. Clark Office of Nuclear Reactor Regulation Page Two Me have now performed more detailed analyses of natural circulation cooldown events to determine'he time it would take for the upper head to cool to a temperature that will prevent voids upon depressurization and how much condensate is required to achieve that condition.
A description of the analysis is contained in Attachment 1.
Our results indicate that cooling down at a 50'/hr rate to 325'nd then maintaining the hot leg temperature at 325'or 20.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> would allow shutdown cooling pressure to be reached without flashing of the upper head flujd jn a total cooldown time of 25.7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />.
The condensate
~requirement for this cooldown is 270,500 gallons.
Our procedures will be,revised to require the operator to follow this cooldown procedure, to establish makeup to the condensate storage
- tank, and to mai ntain the volume of the tank continuously above the technical specification limit.
, Should the makeup, supply be inadequte, the operator will be instructed to commence the drain and fill method, which then can be accompljshed'tilizing the technical specjfication condensate water volume.
t1akeup water can be supplied from the w'ater treatment plant and the two 500,000 gallon city water storage tanks.
Pumping capability from both sources can be supplied from the diesel generators.
In this way, we can accommodate the events which have the highest probabilities of leading to a natural circulation cooldown, i.e. loss of offsite power or loss of component cooling water to the RCP seals.
Should an extremely low probabiljty event occur which could cause a loss of condensate makeup capaci ty, i.e.
- SSE, we would then follow the drain and fill shutdown procedure.
This procedure has been analyzed and performed successfully twice previously at St. Lucie and is considered to be a safe method of cooldown.
He have concluded that this approach adequately accomplishes the goal of bringing the plant to shutdown conditions in a safe manner, Very truly yours, Robert E. Uhrig Vice President Advanced Systems 8 Technology REU/JEM/md cc:
J.P. O'Reilly, Region II Harold F. Reis, Esquire