ML19254A645
| ML19254A645 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 04/23/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Tallman W PUBLIC SERVICE CO. OF NEW HAMPSHIRE |
| References | |
| NUDOCS 7906110041 | |
| Download: ML19254A645 (1) | |
Text
a nrCo, UNITED STATES g
g NUCLEAR REGULATORY COMMISSION
[
') g REGloN I o
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gA xino or enussia.rEsusvevania is40s IJR 2 3 ;ng Docket Nos. 50-443 50-444 Public Service Company of New Hampshire ATTN:
Mr. W. C. Tallman President 1000 Elm Street Manchester, New h_ pshire 03105 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, c
n Boyce H. Grier
' Director
Enclosures:
1.
IE 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:
John D. Haseltine, Project Manager 79061100%
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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 trensient or accident is to provide forced flow using reactor ccolant pumps.
It appears that natural circulation wss 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 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 st0 cooled, 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 possibility of void formation in the reactor coolant system are:
A.
Minimize the operation of t DUPLICATE DOCUMENT the pressurizer and thereby reduction by a blowdown th Entire document previously entered into system under:
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