ML13333A324
| ML13333A324 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/17/1978 |
| From: | Ziemann D SOUTHERN CALIFORNIA EDISON CO. |
| To: | James Drake Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7812060069 | |
| Download: ML13333A324 (5) | |
Text
DISTRIBUTION NRC Local PDR ORB #2 Reading Docket No. 50-206 VStello NOV 1 7 1978 OGEisenhut OI&E (3)
Southern California Edison Company DLZiemann ATTN:
Mr. James H. Drake ABurger Vice President HSmith 2244 Walnut Grove Avenue BGrimes Post Office Box 800 TERA Rosemead, California 91770 JRBuchanan ACRS (16)
Gentlemen:
DKDa-vis Enclosure I to this letter provides a summary of the open items in our review of your fire protection program for San Onofre, Unit 1 (SO-1). revises our staff position, PF-27A (Item 27) to further clarify our concern with the "Cable Spreading Area". Enclosure 2 also identifies an additional staff position PF-51, "Containment", as a result of a survey of the areas inside containment, conducted during our site visit on October 19, 1978.
Your response to the staff positions in Enclosure 2 is requested by November 27, 1978. This will allow consideration of your responses in the preparation of our draft Safety Evaluation of your fire protection program for SO-i.
Sincerely, De.nnis
- iemann, Ch Operati Reactors Branch #2 Division of Operating Reactors
Enclosures:
- 1. Summary
- 2. Staff Positions cc w/enclosures:
See next page 78120 60 0I OFFIE.
DOR:ORB #2 DOR:PSB DOR:RB OFFICE*
OR:---
ORB----
SURNAMFO ABurger:ah TDunning DLZiemann su N M... m....
DATE 11/
78 11/t/78 11//7/78 NRC FORM 318 (9-76) NRCM 024
- u. S. GOVERNMENT PRINTING OFFICE, 1976 -
626-624
I g
Southern California Edison Company
-2 cc w/enclosures:
Rollin E. Woodbury, Vice President and General Counsel Southern California Edison Company Post Office Box 800 Rosemead, California 91770 David R. Pigott Samuel B. Casey Chickerihg & Gregory Three Embarcadero Center.
Twenty-Third Floor San Francisco, California 94111 David W. Gilman Robert G. Lacy San Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 Mission Viejo Branch Library 24851 Chrisanta Drive Mission Viejo, California 92676
- . S. Nuclear Regulatory Commission ATTN:
Robert J. Pate Post Office Box 4167 San Clemente, California 92672
ENCLOSURE 1
SUMMARY
OF OPEN ITEMS ON SAN ONOFRE FIRE PROTECTION REEVALUATION
- 1. NRC letter dated September 30, 1978:
Summary of August 29, 1978 Meeting:
a) Item 27 -
We do not find that the resoonse provided by the licensee in the meeting notes is adequate to address the staff concern. Attached is.a revised statement of the staff position, PF-27A, which further clarifies our concern.
b) Item 44 -
As indicated, further analysis is required by the licensee on this item.
- 2. SCEC letter dated September 30, 1978:
a) As indicated, the results of the evaluation to determine the appropriate fire rating tc be assigned to penetration seals will be provided.
b) As indicated, a conceptual proposal, for an alternate shutdown method not dependent upon the test pump, will be provided by the licensee by January 15, 1979, following an investigation of the systems required X.
for safe shutdown.
- 3. On October 19, 1978, a site visit was conducted.to survey systems located inside containment. The attached staff position, PF-51 was discussed with the licensee at this time.
ENCLOSURE 2 FIRE PROTECTION PROGRAM REVIEW STAFF POSITION SAN ONOFRE, UNIT 1 DOCKET NO. 50-206 PF-27A Cable Spreading Area Staff Concern:
The cable spreading area is located in the upper half of the 4160 volt switchgear room which has a ceiling height of approximately 20 feet.
Cables for redundant divisions of safety related systems are routed in open ladder cable trays in close proximity. The combustible loading in the area consists of 31,500 lb. of electrical cable insulation consisting of PCV, bQ.tyl rubber, neoprene, and other materials that do not meet current flame test requirements.
This insulation gives an average fire loading of 172,000 BTU/ft 2 and equates to a fire severity in excess of two hours. Electrical cables consist of instru ment, control, and power cables. This area contains both divisions of 4160 volt switchgear and associated power and control cables. The availability of both the normal offsite power and emergency onsite power to all safety-related and shutdown systems is dependent upon systems in this area.
The licensee is completing modifications to provide the capability to shutdown with offsite power, independent of fire damage in this area, by the use of suitable casuality procedures.
Fire detection is provided by ceiling mounted smoke detectors. Manual fire fighting is provided by hose stations located outside the area.
The effectiveness of manual fire fighting is limited by the following considerations: Access to the upper elevations of the room would be required in order to direct water from hose stations on a cable fire due to the congestion of cable trays which would prevent such operations from the floor below. Visability in this situation would be greatly reduced due to the accumulation of smoke from a fire at the upper elevation of the room. This environment would require the fire brigade to use self contained breathing apparatus which would restrict their mobility in using fire ladders to gain access with a hose line. Water from hose streams if used in large quantities increases the potential of water damage to redundant divisions of essential switchgear.
An automatic total flooding Halon 1301 suppression system is a planned modification for the combined switchgear room and cable spreading area.
however, additional passive measures are appropriate to prevenL a major electrical cale fire in the cable spreading area for the following reaons:
- 1. The high fire loading due to cable insulation materials.'_
Ap
-2
- 2. The difficulties which would be encountered in combating a major cable fire in this area by manual means.
- 3. The vital nature of the area to effect safe shutdown without resorting to casualty procedures to effect safe shutdown.
Staff Position:
Passive measures should be taken to prevent a major electrical cable fire in the cable spreading areas. These measures should consist of the application of alflame retardant coating to electrical cables or the combination of fire stops in cable trays and the use of suitable fire barriers to prevent fire propagation between adjacent cable trays.
PF-51 Containment Staff Concern:
Cable trays are routed such that electrical cable insulation provides a continuity of combustibles between redundant divisions of cable trays.
This situation would pernit an unnitigated fire in one division of safety related cables to propagate to the redundant division of cable trays.
Due to the increased difficulty of normally supressing fires within containment, passive measures should be provided to prevent fire propagation between redundant divisions of electrical cables.
Staff PosIticn:
Fire stops should be provided in cable trays to prevent fire propagation between redundant divisions of cable trays.