ML20212L944
| ML20212L944 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 01/16/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20212L928 | List: |
| References | |
| NUDOCS 8701290443 | |
| Download: ML20212L944 (3) | |
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~ UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION RY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING APPENDIX R EXEMPTION FROM SECTION III.0 OIL COLLECTION SYSTEM
, CONSUMERS POWER COMPANY RIG ROCK POINT PLANT DOCKET NO. 50-155
1.0 INTRODUCTION
By letter dated February 9, 1982 the licensee requested an exemption from the recuirements of 10 CFR 50, Appendix R, Section III to the extent it requires an oil collection system be installed on the reactor recirculation pumps. The staff reviewed the exemption and found it adequate and therefore granted the exemption. Part of the licensee's basis for the exemption was a calculation of the terrperature rise in the Recirculation Pump Room due to the ignition and burning of the lubricating oil from the recirculation pump. The calculation was found to be in error by members of the NRC inspection team during an Appendix R inspection. By letter dated July 1, 1986 the licensee performed a new calculation and in addition provided information on the location of equipment needed for safe shutdown in relationship to the recirculation pump room.
2.0 DISCUSSION There are two reactor recirculation pumps at Big Rock Point. Each pump motor contains 31.75 gallons of lubricating oil, compared to a typical reactor coolant pump motor which contains 140 to 220 gallons of oil.
The pump motor is vertical and has a lower steady bearing and an upper steady and thrust bearing. Each bearing has its own oil supply with the lower reservoir containing 7 quarts and the upper reservoir containing 120 ouarts.
The oil reservoirs of both bearings are part of the motor end bell housings which are cast iron and do not consist of bolted assemblies.
Only the oil for the thrust bearing is cooled, and this is accomplished by a water cooling coil in the oil. No oil is brought outside the motor housing for conditioning or cooling.
The only locations where the possibility of oil leakage exists are at the drain plugs and oil level sight glasses for each oil reservoir, and the packing glands for the cooling water inlet and outlet of the oil cooler.
The lubricating oil is not pumped so that 1) except for fracture, the oil cannot leak internally, and 2) no spraying (atomizing) of the oil outside the housing can occur.
87o1290443 DR e70116 ADOCK 05000155 PDR
4 There is a low oil level switch for the lower reservoir and both a low and high oil level switch for the upper reservoir. These switches are independently annunciated in the Control Room, and the low oil alarms will alert the operators of possible oil leakage whether or not there is an accompanying fire. In addition, high tempere.ture in the bearings is annunciated in the Control Room, and thereby serve as a backup for the low oil alarms, although there will be a time delay.
Fire detectors which alarm in the Control Room and a manually actuated suppression system have been installed in the Recirculation Pump Room.
Redundant trains of the emergency condenser outlet valves are installed approximately 40 feet above the recirculation pumps should a recirculation pump room fire render the redundant trains of the emergency condenser outlet valves inoperable, the one train of core spray valves located outside the recirculation purp room would remain available for use. The cables associated with this redundant train run in a cable tray that passes through a room that is adjacent to the Recirculation Pump Room, and this roem is connected to the Recirculation Pump Room by two open doorways. Also, the ceiling of this room is approximately 50 feet lower and the doorways are approximately 60. feet lower than the ceiling of the Recirculation Pump Room. Therefore, an oil fire in the Recirculation Pump Room would transfer its heat to the air and surfaces in that room, and not to the air and surfaces in the adjacent room containing the cables for the redundant core spray valves. Since the Reactor Depressurization System, which is located outside the Recirculation Pump Room, and a train of core spray valves will remain free of damage in the event of an oil fire in the Recirculation Pump Room, these systems will be available to safety shutdown the Plant.
3.0 EVALUATION The staff has reviewed the licensee's recalculation of the temperature rise resulting from a fire in the recirculation pump rooms, The calculation is considered approximate, e.g., steady heat transfer was assumed. The licensee did not take into consideration the results of the plume effects or the hot layer which would be found in the room. The calculation was conservative in the fact it considered all the oil from a recirculation pump to have leaked out on to the floor and ignited. The lube oil is fully contained in the l recirculation pump motor housing and the notential for leakaoe of the entire quantity of oil is small. Any possible leakage would therefore result in a fire of limited magnitude. In addition the lubricating oil is not pumped so that except for a fracture, oil cannot leak internally and no spraying of
, atomizing oil outside the housing can occur. Oil leakage from the pumps would travel to the sump where it would be collected. There are no hot surfaces or hazards to ignite the oil.
If all of the lube oil contained in a recirculation pump leaked and was ignited, only one division of safe shutdown equipment would be affected.
, Redundant trains are located outside the recirculation pump room.
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4.0 CONCLUSION
Based on the above evaluation, the staff concludes that the modification to provide an oil collection system would not provide a significant increase in fire safety. The conclusion reached above was not based on the results of the recalculation performed by the licensee, but rather the additieral information provided by the licensee in its July 1,1986 letter. Therefore, the staff finds the conclusions reached in original exemption for the oil collection system remain valid, Principal Contributors: J. Stang, T. Rotella Dated: January 16, 1987 l
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