ML19254A643
| ML19254A643 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 04/23/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Daltroff S PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| References | |
| NUDOCS 7906110029 | |
| Download: ML19254A643 (1) | |
Text
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UNITED STATES p-p*"%g y,
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Docket Nos. 50-277 50-278 Philadelphia Electric Company ATTN:
Mr. S. L. Daltroff Vice President Electric Production 2301 Market Street Philadelphia, Pennsylvania 19101 Gentlemen:
The enclosed Bulletin 79-05B is forwarded to you for inforrrtion.
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, c
f, A 4,n f
Boyce. Grier Director
Enclosures:
1.
Ii Bulletin No.79-05B with Enclosure 2.
ACRS Recommendations to the Commission dated April 18, 1979 and April 20, 1979 (Typed Copy) cc w/encls:
W. T. Ullrich, Station Superintendent Troy B. Conner, Jr., Esquire Eugene J. Bradley, Esquire Raymond L. Hovis, Esquire Warren Rich, Esquire 79061100A7
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 Three Mile Island (TMI) No. 2 incident of March 28, 1979.
Initiation of natural circulation was inhibited by significant co_olant 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 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 reactor coolant pumps.
As stated previously, forced flow of primary coolant through the core is preferred to natural circulation.
Other means of reducing the pos n in h re ctor coolant system are:
DUPLICATE DOCUMENT A.
Minimize the operation of the pressurizer and thereb reduction by a blowdown th Entire document previously entered into system under:
xNo 79G5Md/ 57f No. of pages: