ML20023E151
| ML20023E151 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/25/1983 |
| From: | Stolz J Office of Nuclear Reactor Regulation |
| To: | Reinaldo Rodriguez SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| GL-82-21, TAC-47170, NUDOCS 8306140751 | |
| Download: ML20023E151 (6) | |
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MAY 2 5 1983 DI STR TRtf7T ON_
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Q cket Filed nML VUK L PDR ORB #4 Rdg Docket flo. 50-312 DEisenhut 0 ELD NSIC EJordan Mr. Ronald J. Rodriguez JTaylor ACRS-10 Executive Director, fluclear SMiner Sacramento Municipal Utility District 6201 S Street RIngram P. O. Box 15830 Gray File EBlackwood Sacramento, California 95813 H0rnstein
Dear Mr. Rodriguez:
Fron our review of your responses to our Generic Letter 82-21 dated May 5,1981 on natural circulation cooldown, we find that we require additional information. The specific infomation required is outlined in the enclosure.
In order for us to complete our review by September 30,1983, we require your response within 60 days of receipt of this letter.
This request for additional infomation affects fewer than ten respondents, therefore, OMB clearance is not required under P.L.96-511.
Sincerely,
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John F. Stolz, Chief Operating Reactors Branch #4 Division of Licensing
Enclosure:
3 Request for Additional Infomation cc w/ enclosure:
See next page 8306140751 830525 PDR ADOCK 05000312 p
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.' Sacramento Municipal Utility Rancho Stco, Docket No. 50-312 District cc w/ enclosure (s):
David S. Kaplan, Secretary and Christopher Ellison, Esq.
General Counsel Dian Grueuich, Esq.
Sacramento Municipal Utility California Energy Commission District 1111 Howe Avenue 6201 S Street Sacramento, California 95825 P. O. Box 15830 Sacramento, California 95813 Ms. Eleanor Schwartz California State Office Sacramento County 600 Pennsylvania Avenue, S.E., Rm. 201 Board of Supervisors Washington, D. C.
20003 827 7th Street, Room 424 Sacramento, California 95814 Docketing and Service Section Office of the Secretary Mr. John B. Martin, Regional U.S. Nuclear Regulatory Commission Administrator Washington, D. C.
20555 U.S. Nuclear Regulatory Commission Resi$entInspector/RanchoSeco Region V c/o U. S. N. R. C.
1450 Maria Lane, Suite 210 14410 Twin Cities Road Walnut Creek, California 94596 Herald, CA 95638 Atomic Safety and Licensing Appeal Board Panel U.S. Nuclear Regulatory ' Commission Washington, D. C.
20555 Regional Radiation F.epresentative EPA Reaion IX Alan S. Rosenthal, Chairman 215 Fremont Street Atomic Safety and Licensing San Francisco, California 94111 Appeal Board U. S. Nuclear Regulatory Commission Mr. Robert B. Borsum Washington, D. C.
20555 Babcock & Wilcox Nuclear Power Generation Division Dr. John H. Buck Suite 220, 7910 Woodmont Avenue Atomic Safety and Licensing Bethesda, Maryland 20814 Appeal Board U. S. Nuclear Regulatory Commission Thomas Baxter, Esq.
Washington, D. C.
20555 Shaw, Pittman, Potts & Trowbridge 1800 M Street, N.W.
Christine H. Kohl Washington, D. C.
20036 Atomic Safety and Licensing Appeal Board Herbert H. Brown, Esq.
U. S. Nuclear Regulatory Commission Lawrence Coe Lanpher, Esq.
Washington, D. C.
20555 Hill, Christopher and Phillips, P.C.
1900 M Street, N.W.
Joseph 0. Ward, Chief Washington, D. C.
20036 Radiological Health Branch State Deoartment of Health Services Helen Hubbard 714 P Street, Office Building #8 P. O. Box 63 Sacramento, California 95814 Sunol, California 94586
Enclosure REQUEST FOR ADDITIONAL INFORMATION RANCHO SECO NUCLEAR GENERATING STATION DOCKET NO. 50-312 In response to Generic Letter 81-21 (Reference 1), all PWR licensees were required to provide the following:
(1) A demonstration (e.g., analysis and/or test) that controlled natural circulation cooldown from operating conditions to cold shutdown conditions, conducted in accordance with their procedures, should not result in reactor vessel voiding.
(2) Verification that supplies of condensate grade auxiliary feedwater are sufficient to support their cooldown method, and (3) A description of their training program and the revisions to their procedures.
The Sacramento Municipal Utility District response to these questions is documented in Reference 2.
Your response concludes that you do not intend to provide the required demonstration because it is highly unlikely that a natural circulation cooldown will be performed and because you feel that upper head voiding is not a safety concern.
Natural circulation cooldown is necessary following an extended loss of offsite power or following a reactor coolant pump support system failure.
If void formation during natural circulation cooldown is allowed to reach the elevation of the hot leg, a potential safety concern exists.
For these reasons it is necessary that natural circulation cooldown be explicitly analyzed and included in the emergency procedures.
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4 Your procedures instruct the operator to cooldown at a rate of 100 F/hr or less_ and 'to depressurize gradually in 75 to 100 psi increments. The 4
operator is cautioned that a. sudden increase in pressurizer level indicates that flashing is occurring. The only available analyses (Reference 3, 4) for a B&W designed NSSS indicate that it will take between 84 and 135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> for the systen to reach the Decay Heat Removal.
System entry conditions without voidirp.
Reference 4 concludes that once a void forms it could take a long period of time for it to collapse. We cannot determine if your procedures reflect the fact tnat the upper head cools this slowly nor can we determine what actions the operator is instructed to take if voiding occurs. Therefore, we cannot concluded from the information given that the operator has sufficiert procedures to properly manage this esent.
Finally, an analysis has not been provided that indicates you have t
sufficient condensate supplies to support a cooldown of this length.
The staff can not conclude on the acceptability of your ability to properly manage a natural circulation cooldown with the information available. Therefore, we request that you provide the following i
information. These questions are essentially a restatement of the original questions asked.
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1.) Provide a detailed description of your natural circulation cooldown procedure and its basis (it should include guidance on possibility, prevention and mitigation of upper head voiding and natural circulation interruption.)
2.) Demonstrate by analyses or otherwise, that:
a)
Use of procedures will not result in upper head voiding b)
If voiding occurs, your procedures will prevent voiding at the hot leg elevation and if voiding does occur, at this elevation, your procedures adeauately address interrupted natural circulation.
3.) An analysis that shows you have sufficient condensate supplies to support a conservative estimate of the time to reach the Decay Heat Removal System entry conditions *.
1
- The Reference 4 report makes the following conclusions:
a)
A cooldown without voiding will take a minimum of 84-130 hours.
3 b) 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> are required to collapse a 458 ft steam bubble at 2000 psig during an isobaric process.
(Raising RCS pressure to accelerate bubble condensation is not an effective mechanism for rapid bubble collapse.
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' References l
1.
Generic Letter 81-21, " Natural-Circulation' Cooldown", Ma.v 5, 1981 2.
Letter, Cross to Eisenhut, " Generic Letter 81-21-Natural Circulation Cooldown", November 18, 1981 i
3.
Boman, B.L., " Reactor Vessel Head Cooldown During Natural Circulation Cooldown Prepared for Consumers Power Company", Babcock
& Wilcox Utility Power Generation Division, February,1983.
4.
Tally, C.W., " Single Loop Natural' Circulation Cooldown Prepared for Consumers Power Company," Babcock & Wilcox Nuclear Power Generation Division, August, 1982.
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