ML19289E935
| ML19289E935 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 04/19/1979 |
| From: | Head J SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| NUDOCS 7905290500 | |
| Download: ML19289E935 (2) | |
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Southern California Edison Company QL.h;;*
P. O. BOX 8 0 0 2244 WALNUT GROVE AVENUE nosEMEAo, cAttronNtA 01770
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'p U. S. Nuclear Regulatory Commission Q ~4M g Office of Inspection and Enforcement Region V Suite 202, Walnut Creek Plaza 1990 North California Boulevard Walnut Creek, California 94596 Attention:
R. H. Engelken, Director Docket No. 50-206 San Onofre Unit 1
Dear Sir:
Reference:
NRC letter (Ziemann) to SCE (Drake) dated 2/9/79,
Subject:
SEP Review of Safe Shutdown Systems The following is in regard to Item 5 of IE Bulletin No.79-06A, for-warded by your letter of April 14, 1979.
Item 5 is duplicated below fol-lowed by our response.
Item 5:
"For facilities for which the auxiliary feedwater system is not auto-raatically initiated, prepare and implement immediately procedures which re-quire the stationing of an individual (with no other assigned concurrent duties and in direct and continuous coranunication with the control room) to promptly initiate adequate auxiliary feedwater to the steam generator (s) for those transients or accidents the consequences of which can be limited by such action."
Response
The auxiliary feedwater system at San Onofre Unit 1 is initiated by operator action as follows:
a.
Remote manual start of motor driven auxiliary feedwater pump fran the control rocm, or local manual start of the turbine driven pump; and, b.
Manual opening of auxiliary feedwater system isolation valves.
2C53 214 7005290 9 9
79-u
n k" G mee We heve reviewed the analyses of design basic transients and accidents for San Onofre Unit 1 and have concluded that immediate (automatic or manual) initiation of auxiliary feedwater is not essential in order to limit the ccnsequences of these events. There are, however, cettain events for wnich timely, though not immediate, manual initiation of auxiliary feedwater serves to facilitate a more orderly cooldown of the reactor coolant system and thereby limit the consequences of these events. Specifically, these events include loss of main feedwater flow and postulated main steam line break (MSLB) acci-dents. For each of these events, manual initiation of auxiliary feedwater within 15 minutes following occurrence of the event will permit on3erly cool-down of the RCS. This conclusion is further supported in the above referenced letter wherein the NRC staff has calculated that for the case of loss of load and feedwater there is sufficient water inventory in the steam genrators to maintain ECS temperature acceptable, without initiating any steam generator makeup, for approximately 25 minutes. He consider that this condition, in particular, highlights a fundamental difference between the San Onofre Unit 1 and Three Mile Island Unit 2 designs which bears significantly on the respective plant responses to postulated transients and accidents such as occurred recently at 'Ihree Mile Island.
Based on the above, we consider that sufficient time exists to dispatch operators to manually initiate auxiliary feedwater following occurrence of those transients or accidents the consequences of which can be limited by such actions. Furthermore, such operator actions can be accomplished in connection with other assigned duties. Accordingly, we conclude that the stationing of an operator with no other assigned concurrent duties and in direct and contin-uous communication with the control room to initiate auxiliary feedwater to the steam generators to be unwarranted.
Notwithstanding this conclusion, we have so stationed an operator at the auxiliary feedwater isolation valves effective Friday, April 13, 1979. Should you concur with the conclusion herein, we request your approval to exempt San Onofre Unit 1 from the requirement of Item 5 of IE Bulletin 79-06A. Upon receipt of your approval, we will terminate continuous stationing of an operator at the auxiliary feedwater isolation valves and implement revisions to emergency operating instructions governing affected transients and accidents to clarify the need to effect timely manual initiation of auxiliary feedwater such that an orderly cooldown of the reactor coolant system can be acccraplished.
Your prompt attention to this matter will be appreciated. We are prepared to meet with members of your staff at your convenience to discuss and resolve this matter. Should you require additional information, please let me Imow.
Sincerely,
/
cc: Director, Office of Inspection and Enforcement
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