ML19291B073
| ML19291B073 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 07/26/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Wachter L NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 7908290291 | |
| Download: ML19291B073 (1) | |
Text
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NUCLEAR REGULATORY COMMISSION YU 8'
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799 ROOSEVELT ROAD f
,o CLEN ELLYN, ILLINOIS 60137 JUL 2 6 W9 Docket No. 50-282 Docket No. 50-306 Northern States Power Company ATTN:
Mr. Leo Wachter Vice President Pcwer Production and System Operation 414 Nicollet Mall Minneapolis, MN 55401 Gentlemen:
The enclosed IE Eulletin Nos.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, James G. Kepp er 5
Director
Enclosure:
IE Bulletin Nos.79-05C and 79-06C cc w/ encl:
Mr. F. P. Tierney, Jr.,
Plant Manager John W. Ferman, Ph.D.,
Nuclear Engineer, MPCA Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC 20i3 335 7908290
4 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 July 26, 1979 IE Bulletin Nos.79-05C & 79-06C NUCLEAR INCIDENT AT THREE MILE ISLAND - SUPPLEMENT 3
Description of Circumstances:
Information has become available to the NRC, subsequent to the issuance of s
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 Licensees" portion of IE bulletins79-05A, 79-06A and 79-06B, for all pre.ssurized water reactors (PWRs).
Item 4.c of Bullettr.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.
Similar requirements, applicable to reactors designed by other PWR vendors, were.
contained in h em 7.c 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), Westicghouse and its licensees' generally adopted the porsition 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 calculatitr.s performed by Babcock & Wilcox, "esting-house and Combustion Engineering indicete that, for a certain spectrtm 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 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 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 del LOCA, all holders of operating licenses fo following actions:
DUPLICATE DOCUMENT 2 0sz 3-Entire document previously entered into system under:
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