ML19305A454
| ML19305A454 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/23/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Herbein J METROPOLITAN EDISON CO. |
| References | |
| TASK-TF, TASK-TMR NUDOCS 7906110016 | |
| Download: ML19305A454 (1) | |
Text
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p* "%c UNITED STATES A
.,9,L NUCLEAR REGULATORY COMMISSION j,j ') e
'j REGION I ER A 631 PARK AVENUE W ' s g
KING OF PRUSSI A. PENNSYt.V ant A 19406 D::cket No. 50-289 Metropolitan Edison Company ATTN: Mr. J. G. Herbein Vice President P. O. Box 542 Reading, Pennsylvania 19640 Gentlemen:
The enclosed Bulletin 79-05B is forwarded to you for information.
No written response is required.
We have also enclosed copies of recom-mendations of the ACRS to the Commission for your information.
If you desire additional information regarding this matter, please contact this office.
Sincerely, T------
/
Od 9AR Boyce H. Grier
- Director
Enclosures:
1.
IE Bulletin No. 79-058 with Enclosure 2.
ACRS Recommendations to the Commission dated April 18, 1979 and April 20, 1979 (Typed Copy) cc w/encis:
E. G. Wallace, Licensing Manager J. J. Barton, Project Manager L. L. Lawyer, Manager - Generation Operations G. P. Miller, Manager - Generating Station - Nuclear J. L. Seelinger, Unit 1 Superintendent W. E. Potts, Unit 1 Superintendent - Technical Support I. R. Finfrock, Jr.
Mr. R. Conrad G. F. Trowbridge, Esquire Miss Mary V. Southard, Chairman, Citizens for a Safe Environment l
2906110016
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, DC 20555 IE Bulletin 79-05B April 21,1979 Page 1 of 4 NUCLEAR INCIDENT AT THREE MILE ISLAND - SUPPLEMENT Description of Circumstances:
Continued NRC evaluation of the nuclear incident at Three Mile Island Unit 2 has identified measures in addition to those discussed in IE Bulletin 79-05 and 79-05A which should be acted upon by licensees with reactors designed by B&W. As discussed in Item 4.c. of Actions to be taken by Licensees in IEB 79-05A, the preferred mode of core cooling following a transient or accident is to provide forced flow using reactor coolant pumps.
It appears that natural circulation was not successfully achieved upon securing the reactor coolant pumps during the first two hours of the Thiee Mile Island (TMI) No. 2 incident of March 28, 1979.
Initiation of natural circulation was inhibited by significant coolant voids, possibly aggrevated by release of noncondensible gases, in the primary coolant system.
To avoid this potential for interference with natural circulation, the operator should ensure that the primary system is subcooled, and remains subcooled, before any attempt is made to establish natural circulation.
Natural circulation in Babcock and Wilcox reactor systems is enhanced by maintaining a relatively high water level on the secondary side of the once through steam generators (OTSG).
It is also promoted by injection of auxiliary feedwater at the upper nozzles in the OTSGs.
The integrated Control System automatically sets the OTSG level set operating range when all reactor coolant pumps (RCP) point to 50% on the are secured.
- However, in unusual or abnormal situations, manual actions by the operator to l
increase steam generator level will enhance natural circulation capability in anticipation of a possible loss of operation of the reactor coolant pumps.
As stated previously, forced flow of primary coolant through the core is preferred to natural circulation.
l Other means of reducing the possibility of void formation in the reactor coolant system are:
A.
Minimize the operation of the Power Operated Relief Valve (PORV) on the pressurizer and thereby reduce the possiblity of pressure reduction by a blowdown through a PORV that was stuck open.
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