ML19224C438
| ML19224C438 | |
| Person / Time | |
|---|---|
| Site: | Hatch, Vogtle  |
| Issue date: | 04/21/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | John Miller GEORGIA POWER CO. |
| References | |
| NUDOCS 7907020342 | |
| Download: ML19224C438 (2) | |
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NUCLEAR REGULATORY COMMISSION 47 RECloN il b
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ATLANT A, GEORGI A 30303 APfi 211979
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In Reply Refer To:
RII:JP0 50-321 50-366 50-424 50-425 Georgia Power Company ATTN:
Mr. J. H. Miller, Jr.
Executive Vice President 270 Peachtree Street, N. W.
Atlanta, Georgia 30303 Gentlemen:
The enclosed Bulletin 79-05B is forvarded to you for information.
No written response is required. We have also enclosed copies of recomen-dations of the ACRS to the Comission for your information.
If you desire additional inforlitation regarding this matter, please contact this office, Sincerely, d
C i -hw James P. O'Reilly N Director
Enclosures:
1.
IE Bulletin No.79-05B with Enclosures 2.
ACRS Recocraendations to the Comission dated April 18, 1979 and April 20, 1979
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APR 211973 Georgia Power Company,
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M. Manry, Pl. ant Manager Post Office Box 442 Baxley, Georgia 31513 C
E. Belflower tSite QA Supervisor Post Office Box 442 Baxley, Georgia 31513 L. L. Gray, Jr.
Construction Project Manager Post Office Box 329 Baxley, Georgia 31513 K. M. Gillespie Construction Project Manager Post Office Box 282 Waynesboro, Georgia 30830 E
D. Grover QA Site Supervisor Post Office Box 282 Wayncsboro, Georgia 30830}\\
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTM, DC 20555 APRIL 21, 1979 IE Bulletin 79-05B NUCLEAR INCIDENT AT THREE MILE ISLAhT - SUPPLEMEh7 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 caoling 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 (iMI) 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 seccadary 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.tts the OTSG 1evel setpoint to 50% on the operating range when all reactor coolant pumps (RCP) are secured.
- However, in unusual or abnormal situations, manual actions by the operator to increase steam generator level will enhance natural circulation capability in anticipation of a possible loss of operation of the resetor coolant pumps.
As stated previously, forced flow of primary coolant through the core is preferred to natural circulatioc. Other means of reducing the possibility of void formation in the reactor coolant system are: A. Minimize the operation of the Pove ,, P Valve (PORV) on the pressurizer and thereby tgd reduction by a blowdown through a DUPLICATE DOCUMENT 271 220 t P eviously entered Int sys ern under ANO_ Q q No-Of pages: fh}}