ML19256B332
| ML19256B332 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak, Allens Creek  |
| Issue date: | 04/21/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Gary R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| References | |
| NUDOCS 7906110005 | |
| Download: ML19256B332 (1) | |
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UNITED STATES h
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611 RYAN PLAZA DRIVE,SulTE 1000 o '.
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April 21,1979 In Reply Refer To:
RIV Docket tio. 50-445/IE Bulletin 79-05B 50-466/IE Bulletin 79-058 Texas Utilities Generating Company ATTit: Mr. R. J. Gary, Executive Vice President and General Manager
- 2001 Bryan Tower Dallas, Texas 75201 Gentlemen:
The enclosed IE Bulletin 79-05B is fonvarded to you for information.
?!o written response is required. We have alco enclosed copies of recommendations of the ACRS to the Commission for your information.
If you desire additional information regarding this matter, please contact this office.
Sincerely, C
Karl V. Seyfrit Director
Enclosures:
1.
IE Bulletin flo.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 7906110ODf0
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UNITED STATES
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HUCLEAR REGULATORY COMMISSION P. ~ 5 i.E~ -f=
.i 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, DC 20555 5._ _.r5_
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APRIL 21, 1979 Essa
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NUCLEAR INCIDENT AT THREE MILE ISLAND - SUPPLEMENT 3=.-yr
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Descr1ption of Circumstances:.
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Continued HRC evaluation of the nuclear incident at Three Mile Islan'd.
Unit 2 has identified measures in addition to those discussed in II
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Bulletin 79-05 and 79-05A which should be acted upon by licensees with reactors designed by B&E As discussed in Item 4.c. of Actions to be ket--
taken by Licensees in IEB 79-05A, the preferred mode of core cooling
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following a transient or accident is to provide forced flow using reactor coolant pumps.
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It appears that natural circulation was not successfully achieved upon
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- EE securing the reactor coolant pumps-during the first two hours of the Three Mlle Island (MI) No. 2 incident of March 28, 1979.
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of natural circulation was inhibited by significant coolant voids, f535 possibly aggravated by release of noncondensible gases, in the primary E:[?5 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.
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Natural circulation in Babcock and Wilcox reactor systems is enhanced by Y[. 3..
maintaining a relatively high water level on the secondary side of the M.E once through steam generators (OTSG).
It is also promoted by injection of auxiliary feedwater at the upcer nozzles in the OTSGs. The integrated 7.~"J.~..
Control System automatically sets the OTSG 1evel setpoint to 50% on tha
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operating range when all reactor coolant pumps (RCP) are secured.
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in unusual or abnormal situations, manual actions by the operator to
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increase steam generator level will enhance natural circulation capability 3.g in anticipation of a possible less of operation of the reactor coolant pumps.
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As stated previously, forced flow of primary coolant through the core is g;g.
preferred to natural circulation.
"'r MF Other means of reducing the possibility of void formation in the reactor
'g; coolant system are:
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Minimize the operation of the P s.E ".
the pressurizer and thereby red DUPLICATE DOCUMENT F
reduction by a blowdown through
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