ML19224C440
| ML19224C440 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 04/21/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Mary Johnson SOUTH CAROLINA ELECTRIC & GAS CO. |
| References | |
| NUDOCS 7907020356 | |
| Download: ML19224C440 (2) | |
Text
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UNITED STATES
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9 NUCLEAR REGULATORY COMMISSION REGION 11 o
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D 101 M ARlETTA STREET.N.W.
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APR 211979 In Reply Refer To:
,f RII:JPO 50-395 South Carolina Electric and Gas Company ATTN:
Mr. M. C. Johnson, Vice President and Group Executive - Speciel Services and Purchasing P. O. Box 764 Columbia, South Carolina 29202 Gentlemen:
The enclosed Bulletin 79 15B is forwarded to you for information. No written response is requit :d.
We have also enclosed copies of recocznen-dations of the ACRS to the Cocxnission for your information. If you desire additional information regarding this matter, please contact this office.
Sincerely, James P. O'Reilly [
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N Director
Enclosures:
1.
IE Bulletin No.79-05B with Enclosures 2.
ACRS Recournendations to the Consnission dated April 18, 1979 and April 20, 1979
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271 232 7907020 %
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APR 211579 South Carolina Electric and Gas Company cc w/ encl:
T. B. Conners, Jr.
Conners, Moore and Corber 1 47 Pennsylvania Avenue, N.W.
W shington, D.C.
20006 A. A. Smith Quality Assurance Post Office Box 8 Jenkinsville, South Carolina 29065
- 0. S. Bradham, Manager Nuclear Operations Post Office Box 8 Jenkinsville, South Carolina 29065
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, DC 20555 APRIL 21, 1979 IE Bulletin 79-05B 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 cisrassed in IE Bulletin 79-05 and 79-05A bich 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 finw using reactor coolant pu=ps.
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 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 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 1evel setpoint to 50% on the operating range when all reactor coolant pumps (RCP) are secured. Ecwever, 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. Led previously, forced flow of primary coolant through the core is prefe red to natural circulation.
Other means of reducing the possibility of void formation in the reactor coolant system are:
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Minimize the operation of the Po on the pressurizer and thereby rf DUPLICATE DOCUMENT reduction by a blowdown through a 2[}
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