ML19257B873
| ML19257B873 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 01/16/1980 |
| From: | Hoffman D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| TASK-09-01, TASK-9-1, TASK-RR NUDOCS 8001210117 | |
| Download: ML19257B873 (8) | |
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January 16, 1980 Director, Nuclear Reactor Regulation Att Mr Dennis L Ziemann, Chief Operating Reactors Branch No 2 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - CONSUMERS POWER COMPANY RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION BY LETTER DATED DECEMBER 7, 1979 FROM D L ZIEMANN CONCERNING SPENT FUEL POOL STORAGE EXPANSION Attached please find Consumers Power Company's response to your request of December 7, 1979 for additional information concerning the Big Rock Point Plant spent fuel storage expansions.
David P Hoffman (Signed)
David P Hoffman Nuclear Licensing Administrator CC JGKeppler, UShTC Att 7 Pages 1773 243
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1 PART I Item 1 Provide a description of the piping systems for the spent fuel pool and discuss the potential for draining the pool below the level of the top of the stored fuel from pipe failures that would allow water to be drained, pumped, or siphoned out.
Response
Piping systems that connect with the spent fuel pool are:
Spent Fuel Pool Cooling System (SFPCS) piping, a.
b.
Demineralized Water System piping, and c.
Treated Waste piping.
A spent fuel pool drain line was originally provided in the plant design.
However, during the spent fuel pool liner modification, this drain was plugged and no penetration or provision for draining the pool was provided through the liner.
The redundant SFPCS pumps draw suttion from the surge tank through the fuel pool " sock" filter. No direct piping connection to the pool exists on the suction end of the SFPCS. Surge tank level is maintained by water from the spent fuel pool flowing across a weir and into the surge tank. A pipe failure in the SFPCS will result in draining of the surge tank, fuel pool filter tank and lines. Fuel pool level will not fall below the concrete weir as a result i773 244
2 of any pipe failure in the SFPCS. A water level at the weir provides approximately 20' of water over the top of the fuel assemblies. A siphon breaker in the makeup line inlet to the pool prevents siphoning pool water out of the pool as a result of pipe failures in the SFPCS or any other interconnected piping systems.
Therefore, no pipe failures can allow the full pool water to be drained, pumped, or siphoned out.
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3 Item 2 List all sources of makeup water to the pool (include " damage control measure" sources such as fire hoses). Provide a discussion of the ability of these sources to remain functional following a seismic event.
Response
There are three independent and redundant sources of makeup water to the pool:
a.
Demineralized water system.
b.
Treated waste.
c.
Fire hose.
The Demineralized Water System and the Fire Protection System have been designed to remain intact following a design basis earthquake as discussed in Sections 2.6.3 and 2.6.4 of the Big Rock Point Plant Final Hazards Summary Report.
i773 246
4 Item 3 Discuss the adequacy of the plant systems and procedural controls to enable detection of low fuel pool level following a seismic event. List the instrumentation and alarms associated with the spent fuel pool and the design criteria for the instrumentation and alarms.
Response
The containment and internal structure, including the spent fuel pool, have been designed to remain intact following a design basis earthquake, as discussed in Sections 2.6.3 and 2.6.4 of the FHSR.
Procedural controls specify that the pool level, pool cooling system operation, and pool circulating water temperature be verified twice per shift.
Access to the spent fuel pool area is assumed as a result of the design bases discussed above and, therefore, no significant interruption to this activity will occur as a result of a seismic event.
There is presently no instrumentation designed specifically to provide direct indication of fuel pool water level following a seismic event. However, a constant area monitor and a radiation criticality monitor, both in the vicinity of the pool, will alarm on high radiation as a result of low pool water levels. Both monitors alarm locally and in the control room and are considered to be safety-related as part of the plant Q-List.
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5 Item 4 Discuss the capability to detect loss of pool cooling and loss of water level in the event an accident occurred which would prevent entry into containment for an extended period of time.
Discuss the capability to cool the pool water and provide makeup to the pool if equipment inside the containment failed and containment could not be entered.
Response
The capability to detect the loss of pool cooling is provided in the control room by status indication of spent fuel pool cooling systems (SFPCS) pump motor operation. An indication that both pumps are not operating identifies a possible loss of forced pool cooling.
There is no instrumentation presently installed in the plant specifically designed to provide direct indication of spent fuel pool water level.
Capability to detect a reduction in the water level in the pool is possible by a local constant area monitor and a criticality monitor. These monitors alarm in the control room on high radiation that could result from a reduced pool water level. We will, however, install remote indicating spent fuel pool water level instrumentation prior to the installation of the new spent fuel storage racks, to provide means to augment the existing capability.
As discussed in telephone conversations with USNRC staff, a lack of capability to cool the pool water is not considered significant as long as the effect of boiling conditions in the pool will not adversely affect the integrity of the racks, liner and concrete structure, that evaporative losses from the pool 1773 248
6 will not cause overpressurization problems in the containment and the level of water can be maintained to prevent uncovering of the stored spent fuel.
A qualitative evaluation has been done to address the effects of pool boiling on the rack, liner and concrete structure. The results of the evaluation conclude that boiling conditions are not postulated to adversely affect the fuel racks, liner or concrete structure. A discussion of this finding can be found in Consumers Power Company's response to Question 3 in the December 28, 1979 submittal.
Overpressurization of containment as a result of pool boiling is considered unlikely due to the fact that the boil-off rate is so small (approximately 11 gpm in the worst case, see April 23, 1979 submittal). As a result of this very small energy release, it is concluded that the containment enclosure spray will prevent containment overpressurization since it is designed to prevent overpressurization in the event of a LOCA.
The capability to provide makeup water to the pool (actuated from outside containment) will '
available following the realignment of certain manual valves in the demineralized coater system which are in containment and remote motor-operated valves outside containment. This realignment will ensure makeup capability for an extended period of time in the event containment cannot be entered. This makeup capability will be more than enough to offset evaporative losses.
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7 PART II Item 1 Discuss the inspection and test procedures to be used for the crane and any other rack lifting and transporting devices prior to the movement of the racks in or over the pool.
Response
Inspection and test procedures to be used for the crane and any other rack lifting and transporting devices will be included in the detailed installation procedures. As discussed in response to USNRC Question 1 in our December 28, 1979 letter, we will provide the USNRC with a copy of the detailed installation procedures for review prior to movement of any racks in or over the pool.
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