ML19259C679
| ML19259C679 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 07/26/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| NUDOCS 7908100345 | |
| Download: ML19259C679 (1) | |
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UNITED STATES g
NUCLEAR REGULATORY COMMISSION ti.g?*'
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,o KING OF PRUSSIA, PENNSYLVANIA 19406 July 26,1979 Docket No. 50-336 Northeast Nuclear Energy Company ATTN: Mr. W. G. Counsil Vice President - Nuclear Engineering and Operations P. O. Box 270 Hartford, Connecticut 06101 Gentlemen:
The enclosed Bulletin 79-05C & 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,
^--
Boyce H. Grier Director
Enclosures:
1.
IE Bulletin Nos.79-05C & 79-06C 2.
Listing of IE Bulletins Issued in Last 12 Months cc w/encls:
J. F. Opeka, Station Superintendent D. G. Diedrick, Manager of Quality Assurance J. R. Himmelwright, Licensing Safeguards Engineer
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ENCLOSURE 1 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Bulletin Nos.79-05C & 79-06C Date:
July 26, 1979 Page 1 ot 3 NUCLEAR INCIDENT AT THP.EE MILE ISLAND - SUPPLEMENT Description of Circumstances:
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 (Revision 1) and 79-06B, which requires modification to the " Action To Be Taken By Licensees" portion of IF. BLlletins79-05A, 79-06A and 79-06B, for all pressurized water reactors (PWRs).
Item 4.c of Bulletin 79-05A required 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.
Silar requirement:', applicable to reactors designed by other PWR vendors, were contained in Item 7.s of Bulletin 79-06A (for Westinghouse designed plants) and in Item 6.c of Bulletin 79-06B (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 preli.; nary calculations perfonned by Babcock & Wilcox, Westing-house and Combustion 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 aggravate the uncover-ing 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 coolan't system.
It is our current understanding that all three of the nuclear steam systec.
suppliers for PWRs now agree that an acceptable action under LOCA symptoms is to trip all operating RCPs immediately, before significant voiding in the reactor coolant system occurs.
Action To Be Taken By Licensees:
In order to alleviate the concern over delayed tripping of the RCPs after a LOCA, all holders of operating licenses for PWR facilities shall take the following actions:
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