ML19224C435
| ML19224C435 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 04/21/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Clayton F ALABAMA POWER CO. |
| References | |
| NUDOCS 7907020333 | |
| Download: ML19224C435 (2) | |
Text
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NUCLEAR REGULATORY COMMISSION
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APR 211979 t@Dl In Reply Refer To:
RII:JPO 50-348 50-364 Alabama Power Company ATTN:
Mr. F. L. Clayton Executive Vice President P. O. Box 2641 Birmingham, Alabama 35291 Gentlemen:
The enclosed Bulletin 79-05B is forwarded to you for information.
No written response is required. We have also enclosed copies of recocxnen-dations of the ACRS to the Comission for your information.
If you desire additional information regarding this matter, please contact this office.
Sincerely,
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hw James P. O'Reilly [
N Director
Enclosures:
1.
IE Bulletin No.79-05B with Enclosures 2.
ACRS Recomendations to the Comission dated April 18, 1979 and April 20, 1979
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APR 211979 Alabama Power Company cc w/ encl:
A. R. Barton Executive Vice President Post Office Box 2641 Birmingham, Alabama 35291 C. Biddinger, Jr.
Manager-Corporate Quality Assurance Post Office Box 2641 Birmingham, Alabama 35291 H. O. Thrash Manager-Nuclear Generation Post Office Box 2641 Birmingham, Alabama 35291 H. G. Hairston, III Plant danager Drawer 470 Ashford, Alabama 36312 R. E. Hollands, Jr.
QA Supervisor Post Office Box U Ashford, Alabama 36312
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMEhT WASHINGTON, DC 20555 APRIL 21, 1979 IE Bulletin 79-05B NUCLEAR INCIDENT AT THREE MILE ISLAhT - SUPPLEMEhT Description of Circumstances:
Continued NRC evaluation of the auclear 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 licer. sees 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 Three Mile Island (TMI) No. 2 incident of March 28, 1979.
Initiation of natural circulation was inhibited by significant coolant voids, possibly aggravated 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 1evel setpoint to 50% on the operating ra56c when all reactor coolant pumps (RCP) are secured. However, in unusual or stuormal situations, manual actions by the operator to increase steam generator level will enhance natural circulation capabi?;;y 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.
Other means of reducing the possibility of void formation in the reactor coolant system are:
A.
Minimize the ope ra t i on o f the Pe
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2f} 2)k on the pressurizer and thereby r' DUPLICATE DOCUMENT reduction by a blowdown through 4 Entire document previously entered into system under:
h hk ANO No. of pages:
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