ML19254A644
| ML19254A644 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 04/23/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Boyer V PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| References | |
| NUDOCS 7906110031 | |
| Download: ML19254A644 (1) | |
Text
.
FrEn UNITED STATES
,pn afoug NUCLEAR REGULATORY COMMISSION
,og
,. j REGION I j,(k,
- g 631 PARK AVENUE
- i KING OF PRUSSI A, PENNSYLVANi A 19405 T.?? 2 31979 Docket Nos. 50-352 50-353 Philadelphia Electric Company Attention:
Mr. V. S. Boyer Vice President Engineering and Research 2301 Market Street Philadelphia, PA 19101 Gentlemen:
The enclosed Bulletin 79-058 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 desi,re additional information regarding this matter, please contact this office.
Sincerely, Y
s Boyce H. Grier
- Director
Enclosures:
1.
IE B'lletin No.79-05B wich Enclosure 2.
ACR2 Recommendations to the Commission dated April 18, 1979 and April 20, 1979 (Typed Copy) 790611003[ C
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 tiarch 28, 1979.
Initiation of natural circulation was inhibited by significant coolant voids, possibly aggrevated by release of noncondensible gases, in the primary coolant sy; tem. 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 relat.fvely 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 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 st'Md previously, forced flow of primary coolant through the core is pre ft.
ed to natural circulation.
Other means of reducing the possih_i_n the reactor coolant system are:
A.
Minimize the operation of t the pressurizer and thereby DUPLICATE DOCUMENT reduction by a blowdown thr Entire document previously entered into system under:
hhd[
[
ANO No. of pages:
9
,