ML13333A476
| ML13333A476 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/23/1980 |
| From: | Baskin K Southern California Edison Co |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML13333A477 | List: |
| References | |
| TAC-48143 NUDOCS 8001290430 | |
| Download: ML13333A476 (12) | |
Text
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Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 K. P. BASKIN TELEPHONE
- MANAGER, GENERATION ENGINEERING January 23, 1980 213-572-1401 Director, Office of Nuclear Reactor Regulation Attention:
Mr. D. L. Ziemann, Chief Operating Reactors Branch #2 Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Dentlemen:
Subject:
Docket No. 50-206 Fire Protection Program Review San Onofre Nuclear Generating Station Unit 1 As a result of your review of our submittal dated October 11, 1979, a set of questions was provided by your staff during the telephone discussion of November 13, 1979, regarding the additional design information for modifications to be implemented during the next refueling outage. These questions were combined into a set of eleven items which we have addressed in the enclosure to this letter. The requested design drawings have been included in the enclosure to aid in your review of the response to each item.
If you have any questions or desire additional information, please contact me.
Very truly yours,
'8001290,'30
ENCLOSURE RESPONSE TO OPEN ITEMS FIRE PROTECTION MODIFICATIONS SAN ONOFRE, UNIT 1 The following is a set of responses to the open items which resulted from the telephone discussion with the NRC Staff on November 13, 1979, regarding the fire protection modifications identified in our submittal dated October 23, 1979.
Item 1 The minimum design concentration of Halon in 4 kV and 480 V switchgear rooms should be 7% by volume per NFPA 12A and not 5% as in present design.
Response
NFPA 12A, paragraph 2-1.1.3 limits maximum concentrations of Halon 1301, dependent upon personnel evacuation time.
For evacuation times in excess of one minute, the maximum Halon concentration is 7%.
Paragraph 2.4.2 provides guidance for surface fires suggesting 5% concentration with a ten minute soak time as a practical minimum. Since the detection system is automatic and the fire hazard is cable insulation, there is little possibility of a deep seated fire occurring. Accordingly, the Halon 1301 systems.for San Onofre, Unit 1 are sized on the basis of a 6% design concentration, which is well above the 5% minimum.
Item 2 Provide parameters for Halon design regarding:
(a) discharge time following a signal to operate and (b) duration of desired concentration for both the 4 kV and 480 V switchgear rooms.
Response
The discharge time, provided by the vendor, is calculated to be ten seconds.
The design soak time is ten minutes.
These parameters apply to both the 4 kV and 480 V switchgear rooms.
Item 3 The fire suppression system power supplies should be automatically transferred to the onsite diesel generators upon loss of offsite power.
If manual transfer must be used then an uninterruptable power supply should be included in the design.
Response
The present design of the electric system at San Onofre, Unit 1 is such that upon loss of normal offsite power, manual actions are required to return power to the station (i.e., energization of the 4 kV buses) from either the alter nate source of offsite power, 'or the onsite diesel generators. The time
-2 required to perform all manual actions, and verify the automatic actions, is approximately two minutes.
If the main generator disconnect switch DC drive motor fails, the switch must be opened manually increasing the total time to seven minutes. Once the 4 kV buses are energized, no additional manual actions are required to return the fire protection systems to service.
Since under normal circumstances the fire protection systems would only be out of service for approximately two minutes (seven minutes for worst case) and since no additional manual actions are required to restore the systems to service, the existing design is considered acceptable for supplying power to the fire protection systems following loss of normal offsite power for the following reasons:
a) The fire water system at San Onofre Unit 1 will be interconnected to the Units 2&3 fire water system. Since the Units 2&3 diesel driven fire pump will automatically start on a low pressure demand signal regardless of the availability of offsite power, fire water pumping capability for Unit 1 will be available without performing any manual actions.
b) In the lube oil reservoir and conditioner area, the 480 volt room walls, the north wall of the turbine building, and the general area coverage is protected by a fusible link wet-pipe sprinkler system, in addition to the other systems in the area.
As specified in a) above, fire pumping capability is available so that given a complete loss of offsite power and a fire in this area, the sprinkler system would be available for fire protection even during the 2-7 minutes it would take to restore power to Unit 1.
c) For the areas where the combustible material is cable insulation (switch gear rooms and vital bus cabinet) the 2-7 minute outage of the fire protection systems is considered acceptable based on the fact that these areas involve slow burning, smoldering fires which would not cause a significant amount of damage during the short time period.
d) The area of the Station Service Transformers 2&3 involves a fire hazard associated with 2308 lb. of cable insulation and 534 gal. of oil.
The postulated fire is ignition and spillage of transformer oil from one of the two transformers (267 gal.).
The fire suppression system is intended to protect surrounding cables and other equipment in the vicinity of the transformers. Since this is an open area, it has been determined that the unmitigated fire occurring for a short duration (7 minutes) is not expected to damage these cables and equipment. It has also been shown that the loss of the area will not prevent a safe shutdown of the station.
For these reasons, the 7 minute outage is determined to be acceptable for this area's fire detection and suppression systems.
Item 4 The design water density of 0.15 gpm/ft2 for the water sprinkler system of the Station Service Transformers 2 and 3 is not in accordance with the require ments of Chapter 4 of NFPA 15 nor with those of FM Data Sheet 14-8.
-3
Response
The sprinkler system requirements have been revised to conform with NFPA 15.
The station service transformer sprinkler system design water density per vendor's hydraulic calculations will be 0.30 gpm/ft2.
NFPA 15, paragraph 4-4.3.4 requires 0.25 gpm/ft2 minimum.
Item 5 Provide design drawings for all fire suppression water systems which include general arrangment, location of deluge valves, area covered, sources of water for systems, etc.
Response
The enclosed drawings (5154097, 5154157, 5154143, 5154144, 5154159, 715260, 5154156, 5154141, 715261, 715262, 715267, 715271) are provided for your review. Drawing 5154097 has been modified, but these changes have not been incorporated into the drawing. Accordingly, the modifications are identified on the attached documents (CCN's) which are provided.
Item 6 The design water foam density of 0.15 gpm/ft2 for the foam suppression system of the Lube Oil Reservoir and Conditioner Area is not in accordance with Chapter 4, paragraph 4022 of NFPA 16 (0.16 gpm/ft 2 ).
Response
The sprinkler system requirements have been revised to conform with NFPA 16.
The design water foam density per vendor's hydraulic calculations will be 0.16 gpm/ft2.
Item 7 Provide the basis for using a temperature alarm setpoint of 280oF for the line-type heat detection system of the Cable Tray Fire Detection System in the Lube Oil Reservoir and Conditioner Area.
Response
The cable trays in this area contain power and control cables with ratings up to 266 0 F. Hot spots and cable fires are only expected to occur at or near the rated value. A setpoint of 280oF provides sufficient margin to minimize the likelihood of spurious actuation yet is adequate to protect the cables from a fire both internal and external to the cable trays.
Item 8 The design water density of 0.15 gpm/ft2 for the Area Fusible Link Sprinkler System in the Lube Oil Reservoir and Conditioner Area is not in accordance with the requirements of Chapter 4 of NFPA 15 nor with those of FM Data Sheet 14-8.
Response
The sprinkler system requirements have been revised to conform with NFPA 15.
The system design water density per vendor's hydraulic calculations will be 0.30 gpm/ft2 for the area sprinklers. Based on our evaluation of the heat removal capacity required for the wall sprinkler system, a water density of 0.15 gpm/ft2 has been determined to be conservative and will be used for the design.
Item 9 Provide design drawings for the Area Fire Detection System (ionization smoke detectors) of the Lube Oil Reservoir and Conditioner Area. Include the basis for the location and spacing of the detectors.
Response
The four ionization detectors (XA318-321) are shown on enclosed drawing 5154333 between the cable tray runs on the underside of the mezzanine floor plating. The remaining ionization detectors (XA266-290) as shown on enclosed drawing 5154334 provide coverage for the lube oil reservoir and chemical feed area and are located on the underside of the turbine deck. The location and coverage of these detectors has been reviewed and it has been determined that the arrangement is in agreement with the guidelines contained in NFPA 72E. In order to verify the adequacy of this detector arrangement, in-situ tests will be conducted with a suitable smoke generation device and appropriate modifica tions will be made if necessary. The results of these tests will be trans mitted to the NRC prior to startup following the refueling outage for Cycle 8 operation.
Item 10 Provide design drawings and a detailed description of the Reactor Coolant Pump Lube Oil Drain Pans and Spray Shields. Will the system completely enclose all pressurized portions of lube oil piping associated with the RCP's. Where will the oil be drained to.
Can the drains handle the entire inventory of 1 RCP.
Response
Enclosed drawings (5154154, 5154155) are provided for your review. The pressurized portions of the lube oil piping will be completely enclosed. The sphere sump pump will convey spilled oil to the decontamination,drain tank (D-26).
This tank has a capacity of 350 cubic feet (approximately 2700 gallons).
Since each reactor coolant pump has a lubricating oil inventory of less than 250 gallons, the radioactive waste system can easily accommodate a spill from any one pump.
Item 11 Discuss the adequacy of the methods used to test the operation of the pressure-actuated controller for the fire pumps.
-5
Response
Section 7-5.2.1 of NFPA 20 states in part:
"Suitable provision shall be made for relieving pressure to the pressure actuated switch, to test the operation of the controller and the pumping unit.
(See Fig. A-7-5.2.1.)"
Figure A-7-5.2.1 of NFPA 20 is titled "Piping Connection for Automatic Pressure Switch" and is a recommended arrangement for the interconnection of the controller pressure switch to the firewater loop. The arrangement of that figure includes the devices which incorporate the requirement for suitable provisions for relieving pressure as stated above. This arrangement is only a recommendation and it has been determined that the test method used at San Onofre, Unit 1 complies with the stated requirements.
As transmitted in our October 23, 1979 submittal, the testing methods used include provisions for testing the setpoint of the pressure-actuated switch.
The method used for relieving pressure in the system is to open slightly a valve on the test manifold. The valve used is a 2 inch gate valve which can be throttled to allow a minimal flow and thereby control the pressure decrease to any desired rate.
The capability to control the rate of pressure decrease allows for sufficient accuracy in determining the pressure setpoint for initiation of pump startup.
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 K. P. BASKIN TELEPHONE
- MANAGER, GENERATION ENGINEERING January 23, 1980 213-572-1401 Director, Office of Nuclear Reactor Regulation Attention:
Mr. D. L. Ziemann, Chief Operating Reactors Branch #2 Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Dentlemen:
Subject:
Docket No. 50-206 Fire Protection Program Review San Onofre Nuclear Generating Station Unit 1 As a result of your review of our submittal dated October 11, 1979, a set of questions was provided by your staff during the telephone discussion of November 13, 1979, regarding the additional design information for modifications to be implemented during the next refueling outage. These questions were combined into a set of eleven items which we have addressed in the enclosure to this letter.
The requested design drawings have been included in the enclosure to aid in your review of the response to each item.
If you have any questions or desire additional information, please contact me.
Very truly yours, 4t' t'