ML19224C461
| ML19224C461 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 04/21/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Parker W DUKE POWER CO. |
| References | |
| NUDOCS 7907020417 | |
| Download: ML19224C461 (2) | |
Text
e gnaatop UNITED STATES
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NUCLEAR REGULATORY COMMISSION REGloN ll o
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ATLANT A, GEORGI A 3o303
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o APR 211979 In Reply Refer To:
RII:JPO 50-369 50-370 Duke Power Company ATTN:
Mr. William O. Parker, Jr.
Vice President of Steam Production 422 South Church Street P. O. Box 33189 Charlotte, Ne'.th Carolina 28242 Gentlemen:
The enclosed Bulletin 79-05B is forwarded to you for information. No written response is required. We have also enclosed copies of recomen-dations of the ACRS to the Comission for your information.
If you desire additional information regarding this matter, please contact this office.
Sincerely, D W y/
James P. O'Reilly N Director
Enclosures:
1.
IE Bulletin No.79-05B with Enclosures 2.
ACRS Recomendatione to the Comission dated April 18, IJ79 and April 20, 1979
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APP 211979 Duke Power Company.
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M. D. McIntosh, Plant Manager Post Office Box 488 Cornelius, North Carolina 28031 J. C. Rogers, Project Manager Post Office Box 33189 Charlotte, North Carolina 28242 271 308
UNITED STATEe NUCl. EAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ESTORCEMENT WASHINGTON, DC 20555 APRIL 21, 1979 IE Bulletin 79-05B NUCLEAR INCIDENT AT THREE MILE ISLAND - SUPPLEMEhT 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 's to provide forced flow using reactor coolant pumps.
It appears that natural d rculation was not successfully achieved upon securing the reactor e.2olant pumps during ae trat two hours of the Three Mile Island (TMi) No. 2 incident of March 28, 1s79.
Initiation of natural circulatiot was inhibited by significant coolant voids, possibly aggravated by release of noncondensible gases, in the primary coolant system. Tc e<id this potential for interference with natural circulation, the operater 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 cystems 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 507,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 rear er coolant system are:
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Minimize t'se o eratico of the P
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