ML19256B331
| ML19256B331 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 04/21/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Aswell D LOUISIANA POWER & LIGHT CO. |
| References | |
| NUDOCS 7906110004 | |
| Download: ML19256B331 (1) | |
Text
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April 21, 1979 in Reply Refer 'lo:
RIV Docket flo. 50-382/IE Bulletin 79-05B Louisiana Power and Light Compa6y ATTN: Mr. D. L. Aswell Vice President Power Production 142 Delaronde St.
flew Orleans, Louisiana 70174 Gentlemen:
The enclosed IE Bulletin 79-05B is fonvarded to you for information.
flo written responsa is required. We have also enclosed copies of
, recommendations of the ACRS to the Conmission for your infonnation.
If you desire additional infornation regarding this matter, please contact this office Sincerely, df//64MS-Karl V. Seyfrit Director
Enclosures:
1.
IE Bulletin fio.79-05B with enclosures 2.
ACRS Reconmendations to the Commission dated April 18, 1979 and April 20, 1979 3.
List of IE Bulletins Issued in the Last Twelve Months 7906110ON/
1 I
1 l
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON.-DC 20555 1
APRIL 21, 1979 IE Bulletin 79-C5B 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 I
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 i
following a trancient 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 (THI) 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 subcoolec, before any attempt is made to establish natural circulation.
Natural circulation in Babcock and Wilcox reactor systems is enhanced by maintaining a relatively high wacer icvel on the secondary side of the ence 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 natt.ral 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 the pressurizer and thereb reduction by a blowdown th DUPLICATE DOCUMENT Entire document previously entered into system under:
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