ML13330B241
| ML13330B241 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 07/30/1987 |
| From: | Medford M SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8708050231 | |
| Download: ML13330B241 (8) | |
Text
Southern California Edison Company P. 0. BOX BOO 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M. 0. MEDFORD TELEPHONE MANAGER OF NUCLEAR ENGINEERING (818) 302-1749 AND LICENSING July 30, 1987 U. S. Nuclear Regulatory Commission 10 CFR 50.12(a)(ii)
Attention: Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Fire Protection Exemption Request San Onofre Nuclear Generating Station Unit 1 SCE is in the process of completing revision 3 to the San Onofre Unit 1 10 CFR 50 Appendix R, Section III.G Compliance Evaluation Report. This revision will incorporate all design changes implemented during the Cycle 9 refueling outage and during the recent mid-cycle outage. As part of SCE's internal review of the draft of this revision which was issued for review concurrent with the mid-cycle outage, we have identified changes which must be made to the current San Onofre Unit 1 Fire protection program.
The changes affect the safe shutdown procedures utilized in the event of a fire in the 480V switchgear room (fire area 1-FH-14-7), the yard area (fire zone 1-YD-14-4D), or the pipe tunnel (fire area 1-YD-11-34).
The current fire protection program and procedures credit the availability of the south charging pump G-8B for shutdown in the event of a fire in these areas.
The revised III.G Compliance Report indicates that charging pump G-8B may be lost due to the spurious opening of MOV-1100C in conjunction with loss of letdown. This could result in cavitation of the pump. Cables associated with normal operation of charging pump G-8A are routed in these areas and may be subject to fire damage. The cables associated with dedicated system operation of charging pump G-8A are routed outside these areas and will remain available for shutdown in the event of fire. Additionally, charging pump G-8A will trip on low VCT level in the event of loss of letdown concurrent with spurious opening of MOV-1100C thereby assuring its continued availability. Therefore, the post-fire safe shutdown procedures have been revised to credit dedicated system operation of the north charging pump G-8A in those areas listed above.
No other compensatory measures are considered necessary since the corrective measures (the procedure revisions) were implemented prior to startup from the recent Mid-Cycle Outage.
8708050231 870730 PDR ADOCK 05000206 F
~g
S Document Control Desk July 30, 1987 Since dedicated operation of charging pump G-8A would constitute alternate shutdown, 10 CFR 50 Appendix R, Section III.G.3 applies.Section III.G.3 requires that in areas where alternate or dedicated shutdown capability is provided, the alternate system and associated circuit must be independent of the area under consideration and that fire detection and fixed fire suppression shall be provided in the area where the normal shutdown equipment is located.
The 480V switchgear room (1-FH-14-7) meets these requirements. The yard area (1-YD-14-4D) meets these requirements with consideration given to the 1-hour rated fire barrier provided for VCT low level trip interlock circuit and the exemption granted to the requirements of 10 CFR 50 Appendix R Section III.G.3, dated June 27, 1986. The pipe tunnel (1-YD-11-34) has area wide fire detection provided but requires an exemption to the requirements 10 CFR 50 Appendix R, Section III.G.3 for the lack of suppression. Accordingly, SCE is submitting as an enclosure to this letter a Request for Exemption from the requirements for area wide suppression of 10 CFR 50 Appendix R, Section III.G.3 for fire area 1-YD-11-34.
In accordance with 10 CFR 50.12 (a)(2)(ii), the technical bases, provided in the enclosed fire area request for exemption, demonstrate that special circumstances are present such that application of the regulations in San Onofre Unit 1's particular circumstances is not necessary to achieve the underlying purpose of the requirements of 10 CFR 50 Appendix R III.G.
As stated in 10 CFR 50 Appendix R, the underlying purpose of Section III.G is to ensure that one train of safe shutdown equipment and its associated circuits are free of fire damage so that they remain available to safely shut down the plant. The Section III.G.3 requirements for fire detection and fixed suppression in the fire area under consideration, where alternate or dedicated shutdown is provided are intended to limit the extent of fire damage on the ability to safely shut down the plant. SCE is providing the technical bases to demonstrate that a fire will not affect the alternate shutdown capability and that the existing fire protection features are adequate. Therefore, the installation of automatic suppression in the fire area would not enhance, to a significant degree, the ability to maintain one train of safe shutdown equipment free of fire damage due to the special circumstances of fire area 1-YD-11-34 discussed in the request for exemption.
Moreover, implementing modifications to provide automatic fire suppression in this fire area would result in an unnecessary burden upon SCE since the costs associated with compliance in this fire area is not commensurate with the resulting improvement in the ability to safely shut down the plant after a fire and are in excess of those required to meet the underlying purpose of the rule. These costs include:
- 1. The capital cost associated with engineering and installation of additional fire protection modifications.
Document Control Desk July 30, 1987
- 2. The operational costs associated with the increased surveillance and maintenance on the additional fire protection equipment.
- 3. The additional engineering analysis and possible resulting modifications involved in the potential impact of spurious operation or rupture of fire suppression systems on safety related equipment and normal operations.
Therefore, the request for exemption enclosed meets the requirements of 10 CFR 50.12 paragraph (a)(2)(ii) in that special circumstances are present.
Further, SCE has concluded that the granting of these exemptions would not present an undue risk to the public health and safety, and are consistent with common defense and security.
Your expeditious review and approval of the enclosed request for exemption would be appreciated. SCE is available to support your efforts and will meet with your staff at their convenience, if necessary.
Pursuant to 10 CFR 170.12(c), the review of this request for exemption has been determined to require a fee of $150.00. Accordingly, SCE's check in the amount of $150.00 is enclosed.
If you have any questions, or if we can provide additional information, please let me know.
Very truly yours, Enclosure cc: R. F. Dudley, NRR Project Manager, San Onofre Unit 1 J. B. Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3
10 CFR 50 Appendix R Section III.G.3 Request for Exemption Fire Area 1-YD-11-34
EXEMPTION FIRE AREA 1-AB-11-34 TITLE:
Pipe Tunnel FIGURE:
3-3 DESCRIPTION OF DEVIATION Statement of Problem Cabling for the volume control tank isolation valve MOV-1100C is routed through this fire area. A fault in this cabling could cause MOV-1100C to fail in its normally open position. Since cabling for letdown valves are also routed in this fire area, loss of letdown may also occur. This could result in cavitation of charging pump G-8B. Charging pump G-8A will remain available since the cabling associated with its volume control tank low-low-low level trip are not affected by a fire in this fire area. Cabling for normal operation of charging pump G-8A and its support systems may also be lost for a fire in this fire area. Credit will therefore be taken for alternative shutdown operation of G-8A via the dedicated shutdown system power supply.
Cabling for alternative shutdown operation of G-8A and its support equipment is located outside this fire area and will therefore remain available. The fire area does not meet the requirements of Section III.G.3 of Appendix R, in that fixed fire suppression systems are not provided in the fire area.
AREA DESCRIPTION Physical Characteristics This fire area is located below grade, east of the reactor auxiliary building.
The walls are all 3-hour rated except as noted below. The ceiling is reinforced concrete with an approximate thickness of 9".
The fire area boundary contains a concrete plug over a manhole at the north end of the pipe tunnel and a manhole at the south end of the tunnel which communicate with the yard area (1-YD-14-4D).
The northeast end of the pipe tunnel is exposed to zone 1-YD-14-4D through an open grating.
Combustibles The in-situ combustible loading in this fire area consists of cable trays running throughout the area. The in-situ fire loading is 11,483 BTU/sq. ft.,
with an equivalent fire severity of approximately nine minutes.
Due to this area's remote location and confined nature, significant quantities of transient combustibles are not expected.
FIRE AREA 1-AB-11-34 ACTIVE FIRE PROTECTION CAPABILITY Detection Area wide ionization smoke detectors are installed in the tunnel.
Suppression There is a portable extinguisher located near each end of this area below the manholes. Manual hose reels are provided in adjacent fire areas with access to the pipe tunnel.
BASIS FOR EXEMPTION An exemption is requested from the requirements of 10CFR50 Appendix R, Section III.G.3, which requires that fire detection and fixed suppression be installed in any area for which alternative shutdown capability is provided. A fixed suppression system is not provided in this area. The technical bases which justify the exemption request are detailed below:
- 1. Alternative shutdown capability is provided outside the fire area.
- 2. The combustible in-situ fire loading in the fire area results in an equivalent fire severity of approximately nine minutes.
- 3. Ionization fire detectors are provided in the tunnel thereby ensuring early detection of a fire in this area.
- 4. The area near the northeast end of the tunnel where the tunnel communicates with the yard area through a grating contains only a small quantity of combustible cable insulation thus limiting the possibility of propagation of a fire through the barrier at this location.
- 5. The only non-rated assemblies in the fire area boundary are those leading to the yard area (1-YD-14-4D).
The yard area contains modest quantities of in-situ combustibles in this vicinity therefore precluding propagation of fire from the tunnel to the yard area. In the unlikely event that a fire were to spread to the yard area, the dedicated shutdown capability credited for the pipe tunnel will still remain available. Therefore, the resultant fire would be bounded by the yard area fire evaluation.
- 6. Portable fire extinguishers and hose stations are available for manual fire fighting capability.
FIRE AREA 1-AB-11-34
- 7. The San Onofre Fire Department consists of professionally trained, full time personnel whose primary responsibility is fighting fires at San Onofre. The fire department is certified by the State of California Fire Marshall's office to provide fire suppression activities. A minimum of five certified fire fighters are on duty per shift. The first arriving fire fighters under normal circumstances can be expected to be on the scene within five minutes of the receipt of an alarm.
CONCLUSION Based upon the above described configuration, the addition of a fire suppression system in this fire area would not enhance, to a significant degree, the protection of safe shutdown capability of San Onofre Unit 1 beyond that provided by the existing configuration.
FIGURE 3-3 I
VN 200-4 AH-1
~
.M A TCHL INE SEE DWG.
5 182 492 M..
I
- 10 9 I~LA AT-2 2
EL c0-I I-A
-1I 1551.
Ga II
-AB-30-2P
_Ic ST.-a T-w0-ID(
)
- WETAL, T4C0St5.TiWA ER
-1 O-0 TEIfIA PEIIAI~
ACSI IEW5 I L O
.A-501I0 AICI (50.C5 I.'
IA S S
I
,SI 5 51 CR (C 1 5
.5 54 45