ML19224C434
| ML19224C434 | |
| Person / Time | |
|---|---|
| Site: | Atlantic Nuclear Power Plant  |
| Issue date: | 04/21/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Collier A OFFSHORE POWER SYSTEMS (SUBS. OF WESTINGHOUSE ELECTRI |
| References | |
| NUDOCS 7907020332 | |
| Download: ML19224C434 (1) | |
Text
e gnam:00 UNITED STATES 9'o NUCLEAR REGULATORY COMMISSION g
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/*,. E 101 M ARIETTA STR EET, N.W.
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AnANT4.oEoRoia scaca APR 211979
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l In Reply Refer To:
RII:JP0 50-437 Offshore Power Systems ATTN:
Mr. A. R. Collier, President P. O. Box 8000 Jacksonville, Florida 32211 Gentlemen:
The enclosed Bulletin 79-05B is forwarded to you for information. No written response is required. We have also enclosed copies of recocznen-datio 2s of the ACRS to the Cocznission for your information.
If you desi.e additional information regarding this matter, please contact tP.u office.
Sincerely, James P. O'Reilly [
R
-d,- w N Director
Enclosures:
1.
IE Bulletin No.79-05B with Enclosures 2.
ACRS Recocrnendations to the Cocruission dated April 18, 1979 and April 20, 1979 271 210 oA o
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UNITE 0 STATES h"UCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND EhTORCEMENT WASHINGTON, DC 20555 APRIL 21, 1979 I
IE Bulletin 79-05B NUCLEAR INCIDENT AT THREE MILE ISLAND - SUPPLEMENT
'sescription of Circumstances:
Continued KRC evaluation of the nuclear incident at Three Nile 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&V.
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 :ccident is to provide forced flow using reactor coolant pumps.
It appears that natural circulatica 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 gasen, 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 syste-os is enhanced by maintaining a rt latively 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 Systen automatically sets the OTSG level setpoint to 50% on the operating range when all reactor coolant pumps (RCP) are recured. However, in unusual or abnormal situations, minual actions by the operator to increase steam generator level vill 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:
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Minimize the operation of the Pows on the pressurizer and thereby rgdi DUPLICATE DOCUMENT }[]
}]j reduction by a blowdown through a 1 Entire document previously entered into system under:
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