ML20205R037
| ML20205R037 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 04/16/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20205R014 | List: |
| References | |
| NUDOCS 9904220160 | |
| Download: ML20205R037 (6) | |
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W ee p k UNITED STATE 8 g
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20000 4001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO REQUEST FOR APPROVAL OF DEVIATION FROM FIRE PROTECTION PROGRAM INCORPORATING CERTAIN REQUIREMENTS OF APPENDIX R TO 10 CFR PART 50 SOUTHERN CALIFORNIA EDISON COMPANY SAN DIEGO GAS AND ELECTRIC COMPANY THE CITY OF RIVERSIDE. CALIFORNIA THE CITY OF ANAHEIM. CALIFORNIA I
SAN ONOFRE NUCLEAR GENERATING STATION. UNITS 2 AND 3 t
DOCKET NOS. 50-361 AND 50-362
1.0 INTRODUCTION
By letter dated March 11,1999, Southern Califomia Edison Ccmpany, et al. (SCE or the licensee) requested NRC approval for a deviation from its approved fire protection program under the provisions of License Conditions 2.C.(14) for Unit 2 and 2.C.(12) for Unit 3.
The approved fire protection program for SONGS incorporates by reference the requirements of Section ll1.0 of Appendix R to 10 CFR Part 50, which require in part that reactor coolant pumps (RCPs) be equipped with an oil collection system to collect lube oil from all potential leakage sites including oil fill lines. The licensee requested approval of a deviation from its fire protection program to allow use of remote oil fill lines not equipped with an oil collection system to refill oil reservoirs on the RCPs.
2.0 BACKGROUND
The remote oil fill lines to the RCPs were connected and used prior to 1997. The licensee disconnected these lines in 1997 following interactions with the NRC cff and an SCE evaluation of the conformance of the oil collection system for the filllines to its fire protection program which incorporates the requirements of Section Ill.O of Appendix R to 10 CFR Part 50.
The NRC staff and the licensee have subsequently reevaluated the use of remote oil fill lines for RCPs without complete oil collection systems.
The licensee connected the remote oil fill lines to the SONGS Unit 2 RCP lube oil systems during the Cycle 10 refueling outage, which ended February 26,1999. The licensee implemented administrative controls, including use of covers, to prevent the use of the oil fill 9904220160 990416 1 PDR ADOCK O ,
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lines pending NRC review of the proposed deviation. The licensee plans to connect the Unit 3 remote oil fill lines during the upcoming Cycle 10 refueling outage, scheduled for the end of March 1999. These lines, which extend from the 45 foot elevation walkway adjacent to the RCP motor to the oil fill line connections on the RCPs, were installed to reduce radiation exposure and personnel safety hazards to workers who periodically add oil to the RCP lube oil systems during power operation.
3.0 EVALUATION The underlying purpose behind the lube oil collection system is to ensure that leaking oil will not lead to a fire which could damage safety related equipment during normal or design basis accident conditions.
As a result of oil consumption during power operations, the licensee needs to periodically add oil to the RCP motor lube oil lower reservoir. Previously, this was accomplished by transporting oil into the containment building cavities (inside the bio-shield) and adding the oil using the oil fill connection on the motor. This resulted in both as low as reasonably achievable (ALARA) (an estimated 600 mR per entry) and personnel safety concems, including heat stress, climbing unguarded structures, and stepping out onto a beam, while carrying and pouring the containers of oil.
In an effort to minimize radiation exposure to maintenance personnel and address the personnel safety concerns, the licensee installed a gravity feed, remote oil fill system on each RCP motor. The system consists of a covered hopper and stainless steel tubing at the 45 fcot elevation adjacent to each RCP. The oil hopper is designed to accommodate up to a five gallon container of oil inserted upside down. After the container is inserted, the lid of the hopper will be closed. The oil container completely empties out while inside the hopper; thus there is no potential of spillage during filling. These fill hoppers are connected to each RCP motor lower reservoir fill connection by stainless steel tubing (3/8" in Unit 2 and 1/2" in Unit 3) using high pressure compression fittings. The licensee estimated that oil fill efforts using these hoppers will result in a reduced radiation exposure (from 600mR to an estimated 50 mR per entry) and reduced risk of physicalinjury.
These remote oil fill lines and hoppers are seismically mour. :d. The stainless steel (SS) tubing, the hopper, and the oil fill connection are all mounted on the motor to minimize the effect of any translated vibration and thermal movement. Not all of the SS tubing nor all of the hoppers are protected by an oil collection system. The connections to the motor lower reservoirs are protected by installed oil collection system pans. The maxirnum oil level in the reservoirs is lower than the oil fill connection.
The remote oil fill tubing runs are connected with high pressure compression fittings. All the fittings, except for one fitting per pump, is protected by an oil collection system. This type of fitting is highly reliable, especially when used in low pressure or vented applications, and not typically subject to leakage. The minimum slope of the installed tubing is 1/8" per 12" run. This ensures the system drains following each use and remains a dry system.
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The remote oil fill lines are fully contained within the fire zone boundary where the RCF is i located. With the above described remote oil fill system, the licensee considers that oil can be safely added to the RCP motor lower oil reservoirs. During each oil fill, the appropriate increase .
in reservoir level will be observed using a level indication system, in each case, the licensee will use the resultant indicated change in oil level to verify that the oil reaches the reservoir.
The licensee will use administrative controls, discussed later in this evaluation, to ensure any potential leakage is identified and eliminated.
The routing of the remote oil filllines, as described above, is from the side of the RCP motor, i under the grating, to the motor lower ett reservoir fill port. The oil fill tubing is routed such that :
no leakage from the system could reach any fibrous blanket insulation located in the containment building. All insulation that potential leakage from the system could come into contact with is a stainless steel reflective type pipe insulation. The expected maximum temperature on this type of insulation is less than 200'F under worst case design conditions, and would not, therefore, be an ignition source.
The Unit 2 containment building is a reinforced concrete structure that houses the reactor, steam generators, reactor coolant pumps, reactor coolant system, and other required support systems. The building is divided into three (3) principal fire areas, two of which do not contain any safe shutdown equipment. The fire area containing safe shutdown equipment and cables is comprised of fire zones 2-CO-15-1A,2-CO-15-1B,2-CO-15-1C, and 2-CO-63-1D. Fire zones 2-CO-15-1A and 2-CO-15-1B are the steam generator rooms. Fire zone 2-CO-15-1C is the area outside the steam generator on elevations 15,30, and 45 feet. Fire zone 2-CO-63-1D is the operating floor at elevation 63 feet six inches. All four fire zones are considered one fire area because of a number of unsealed floor penetrations and the use of open metal grating as floors.
Fire zones 2-CO-15-1 A and 2-CO-15-18, which contain RCPs, are the primary concem of the proposed deviation. The major in-situ combustibles located in fire zones 2-CO-15-1 A and 18 are cable insulation and RCP motor lube oillocated on the 45 foot elevation. Introduction cf transient combustibles to the area is controlled by plant administrative procedures, and access is limited to the area during normal plant operation. Although these fire zones do not have zone wide fire detection, fixed temperature rate-of-rise heat detectors and a semi-automatic water spray system are located above the RCPs. In the unlikely event of a fire, the detectors will provide an alarm to the control room as well as the site fire department office to alert Operations to open the containrnent firewater isolation valve. In addition, manual fire suppression capability, consisting of portable extinguishers and hose stations,4 svailable in adjacent fire zone 2-CO-M-1C.
The containment building is divided into
- ire areas for the purposes of evaluating the effects of fires. The zones were divided on the basis of clear space without intervening combustibles.
The north half of the containment building outside the generator rooms contains cabling and equipment associated with safe shutdown that is separated from cabling and equipment in the south half of the containment building. The oil filllines for the RCP motors are located in the steam generator rooms: fire; zones 2-CO-15-1 A (north) and 2-CO-15-1B (south). There are two RCPs in each steam generator room. The RCP remote fill tubing does not communicate outside the respective steam generator room. The effects of postulated oil loss inside the generator rooms during the oil fill evolution were specifically evaluated for each zone.
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- o Safe shutdown equipment located in these fire areas includes the following:
. Steam generator pressure and level instrumentation and associated cables
. Reactor coolant temperature instrumentation and associated cables
. Pressurizer pressure and level instrumentation and associated cables The licensee had previously analyzed the separation of these instruments and associated cables. The analysis demonstrated that for a fire in a steam generator compartment, redundant instruments will not be affected and at least one required channel will remain available for safe shutdown. The steam generator compartments block a direct path of fire between redundant cables as the cables leave the steam generator compartment. This separation, combined with the physical barrier of the steam generator rooms during most of the cables' routing, makes it highly unlikely that a single fire will affect instrumentation to both steam generators.
Pressurizer pressure and levelinstruments are mounted on the outside of the steam generator '
compartments. Cables from the pressurizer pressure and pressurizer level instrumentation are all routed independently inside containment. It is highly unlikely that a fire of sufficient magnitude will occur that will affect all channels of pressurizer pressure and level instrumentation; therefore, at least one channel of pressurizer pressure and level indication will remain available for safe shutdown.
The licensee also analyzed the effects of a potential fire from a leak occurring during oil fill. Oil leaks, if not captured by the lube oil collection system, would tend to migrate to the containment floor where it would flow to the equipment drains under the RCPs. The temperature of the equipment in the area will remain significantly below the auto-ignition temperature. Currently, Mobil, SHC 626 (synthetic) oil, which has an auto-ignition temperature of 720*F and a flash point of 4407F, is used at the lubricating oil for the RCPs. Fixed temperature rate-of-rise type heat detectors are installed over each RCP in the steam generator rooms. The detection system alarms are in the control room and the fire department office. The semi-automatic suppression system is designed to control the spread of fire, if it did occur. Additionally, manual fire suppression equipment is readily available for responding to a fire.
The licensee has established an administrative I;mit of three (3) gallons of oil per oil fill. This will limit the amount of oil that is not contained in the unlikely event of an oil leak. Given that the RCP oil remote fill system is not pressurized, the size of the generator room, the ignition i temperature of the oil, and the limited size of the postulated fire (three gallons of oil), the ;
potential for fire is minimized. The licensee therefore considers that damage to redundant instrumentation channels outside the generator room due to a lube oil leak from the fill lines is not credible.
Due to system design (sloping lines that do not retain oil) and the process for adding oil, the likelihood of an oil leak of three gallons is very remote. Further, should a leak occur during filling, the amount of the oil leaked would be much less than the contents from one RCP motor, which hat, been analyzed from a safe shutdown perspective and found to be acceptable.
Therefore, in the unlikely event of a fire involving the maximum postulated lobe oil leak from one RCP, the saility to achieve and maintain safe shutdown is reasonably assured.
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a In order to minimize the potential for an oil fire due to a leak from the lines of the remote oil fill system that do not have an oil collection system, the licensee will take the following actions each time oil is added through this system:
Prior to each fill the remote oil fill lines will be visually inspected.
. Each remote oil fill will be limited to three gallons.
A level indicator (e.g., PMS computer) will be utilized to verify that the three gallons has reached the reservoir of the correct RCP motor (the oil level can be determined to within
% gallon).
4 Subsequent to each fill the remote oil fill lines will be visually inspected for leakage.
The total oil volume to be added will be limited to less than the amount calculated to result in an indicated reservoir level of 95 percent.
Should any oil leak, it will be removed prior to exiting the containment building.
. The remote oil fill lines will be inspected each outage in conjunction with the RCP lube oil system inspection.
If at any point during a remote fill operation it is determined that added oil is not reaching the desired location, the activity will be terminated, and the situation will be assessed. Personnel responsible for adding oil to the system will also inspect for evidence of smoke following the oil fill if smoke is detected, a fire brigade will be dispatched to the area. Fire suppression equipment is readily available for use in responding to such an event.
4.0 CONCLUSION
The staff has reviewed the licensee's design, analysis, and compensatory measures provided to support the request for approval of a deviation from its approved fire protection program, specifically use of a remote RCP oil fill system without a complete oil collection system. Based on its review and the licenser /s compensatory measures, the staff concludes that the design of the oil filling system and the level of protection provided during oil fill operations provide reasonable assurance that a lube oil fire would not occur. The staff also concludes that in the event of a worst-cast postulated fire resulting from not having a complete oil collection system for the tube oil fill lines, it would be of limited magnitude and extent and would not damage safety related equipment. In addition, the staff concludes that such a fire would not prevent the operators from achieving and maintaining safe shutdown conditions.
Based on its evaluation and the facts and circumstances as discussed above, the staff concludes that the licensee's proposed deviation from its approved fim protection program to the extent it incorporates the technical requirements of Section Ill.O / Appendix R to 10 CFR Part 50 that specifically apply to the RCP oil fiil piping, is a change t; i e approved fire
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protection program that does not adversely affect the ability to achieve and maintain safe shutdown in the event of a fire and, therefore, does not require prior approval of the NRC under Paragraphs 2.C.(14) and 2.C.(12) of Facility Operating Licenses NPF-10 and NPF-15,
! respectively.
Principal Contributor: J. Clifford Date: April 16, 1999 l
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