ML19225D059
| ML19225D059 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 07/26/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 7908060028 | |
| Download: ML19225D059 (1) | |
Text
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y UNITED STATES es
[{y y g,('[7,j NUCLEAR REGULATORY COMMISSION
, l) L REGION V
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SUITE 202. WALNUT CREE K PLAZA
- .,.e WALNUT CREEK, CALIFORNI A 94596 July 26, 1979 Docket flo. 50-312 i
I Sacramento Municipal Utility District P. O. Box 15830 Sacramento, California 95813 Attention: Mr. John J. Mattimoe Assistant General Manager Gentlemen:
The enclosed Bulletin 79-05C and 79-06C is forwarded to you for action.
Written responses are required.
If you desire additional information regarding this matter, please contact this office.
Sincerely,
}LLp p
R. H. Ehgelken Director
Enclosures:
1.
& 79-06C 2.
List of IE Bulletins Issued in Last 12 Months cc w/ enclosures:
R. J. Rodriguez, SMUD L. G. Schwieger, SMUD 421 103 s
o,, o 7908080 40 C?
UNITED STATES NUCLEAR REGULATORY CCPt1ISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 July 26, 1979 IE Bulletin Nos.79-05C & 79-06C
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NUCLEAR INCIDENT AT THREE MILE ISLAND - SUPPLEMENT Description of Circumstances:
l Information has become available to the NRC, subsequent to the issuance of IE Bulletins 79-05,79-05A, 79-05B, 79-06,79-06A, 79-06A (Revison 1) and 79-06B, which requires modification to the " Action To Be Taken By License: " portion of IE Bulletins79-05A, 79-06A and 79-068, for all pressurized water reactors (PWRs).
Item 4.c of Bulletin 79-05A reouired all holders of operating licenses for Babcock & Wilcox designed PWRs to revise their operating procedures to specify that, in the event of high pressure injection (HPI) initiation with reactor coolant pumps (RCPs) operating, at least one RCP per loop would remain operating.
Similar requirements, applicable to reactors desicned by other PWR vendors, were contained in Item 7.c of Bulletin 79-06A (for Westinghouse designed plants) and in Item 6.c of Bulletin 79-068 (for Combustion Engineering designed plants).
Prior to the incident at Three Mile Island Unit 2 (TMI 2), Westinghouse and its licensees generally adopted the position that the operator should promptly trip all operating RCPs in the loss of coolant accident (LOCA) situation. This Westinghouse position, has led to a series of meetings between the NRC staff and Westinghouse, as well as with other PWR vendors, to discuss this issue.
In addition, more detailed analyses concerning this matter were requested by the NRC. Recent preliminary calculations perfomed by Babcock & Wilcox, Westing-house and Cocbustion Engineering indicate that, for a certain spectrum of small breaks in the reactor coolant system, continued operation of the RCPs can increase the mass lost through the break and prolong or aqqravate the uncover-inq of the reactor core.
The damage to the reactor core at TMI 2 followed tripping of the last operating RCP, when two phase fluid was being pumped through the reactor coolant system.
It is our current understanding that all three of the nuclear steam system suppliers for PWRs now agree that an acceptable action under LOCA spptoms is to trip all operating RCPs imediately, before significant voiding in the reactor coolant system occurs.
3e.
Action To Be Taken By Licensees:
- DUPLICATE DOCUMENT In order to alleviate the concern over de) Entire document previously entered LCCA, all holders of cperat;nc licenses U into system under
following actions:
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c 421 104 No. of pages:
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