ML20039B080
| ML20039B080 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/14/1981 |
| From: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-09-01, TASK-9-1, TASK-RR B-10346, NUDOCS 8112220265 | |
| Download: ML20039B080 (6) | |
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Reference:
(1)
W. G. Counsil letter to D. M. Crutchfiel, ated August 31, 1981.
I Gentlemen:
Millstone Nuclear Power Station, Unit No. 1 SEP Topic IX-1, Fuel Storage In Reference (1), Northeast Nuclear Energy Company (NNECO) submitted the Safety Assessment Report (SAR) for SEP Topic IX-1, Fuel Storage, for Millstone Unit No. 1.
Subsequent to the docketing of Reference (1), the Staff identified additional information required to complete the evaluation of this SEP Topic.
In accordance with this request, NNECO is providing Attachment 1 as an Addendum to the SAR submitted in Reference (1).
We trust the Staff will appropriately use this information to develop a Safety Assessment Report for this SEP topic.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY
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AWa W.' G. Counsil Senior Vice President OY
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8112220265 011214 PDR ADOCK 05000245 p
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Docket No. 50-245 Addendum to Safety Assessment Report SEP TOPIC IX-1, Fuel Storage December, 1981
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TOPIC IX-1 FUEL STORAGE MILLSTONE UNIT NO. 1 ADDENDUM The following has been compiled to address questions received from the NRC staff.
REQUEST Describe and demonstrate the equivalence of the Class I and Class ll classifications as stated in the FSAR to seismic Category I classification with respect to structures, systems, and components.
RESPONSE
A detailed description of Class I and Class li classifications is contained in Section 12.0 (Structural Design) of the FSAR as referenced. This request encompasses the unit as a whole and as such is not applicable to this topic.
The seismic design criteria used are being reviewed under Topic 111-6.
Other related topics include lil-1, Classification of Structures, Components, and Systems (seismic and quality); and lil-7B, Design Codes, Design Criteria, and Load Combinations. The specifics of the spent fuel system structures, systems, and components are included in the following request.
REQUEST in reference to ANSI N210-1976/ANS 57.2 and Fegulatory Guides 1.13, 1.26, and 1.29, provide the information for the following regarding the spent fuel cooling system and spent fuel storage pool.
Part A Describe and discuss those portions of the spent fuel pool cooling system which are seismic Category 1, nonseismic Category 1, and their corresponding quality group (safety class) classification.
For those non seismic Category I portions, describe the system design which, in the event of maloperation or failure in the system (including failure resulting from the safe shutdown earthquake) will not cause violation of minimum depth'in the pool for cooling or shielding.
During a conversation with the NRC on October 23,1981, the following
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addi+1onal information was requested.
1.
What code was the spent fuel pool cooling system piping designed to?
2.
What seismic criteria was the coo 1Ing system piping designed to?
TOPIC IX-1 FUEL STORAGE MILLSTONE UNIT NO. 1 ADDENDUM PAGE 2
RESPONSE
The spent fuel pool cooling system at Millstone Unit 1 is non seismic Category I and is not designed to any quality group classification as none existed at the time it was designed. The cooling system piping was designed.to USAS S31.1.0, predecessor to ANSI B31.1, and was not designed for any seismic loadings.
The only non seismic Category I portions of the spent fuel pool cooling system which enters the pool are the two coolant return pipes which terminate in diffusers. These pipes do not penetrate the pool liner.
The return pipes are equipped with check valves and have 1/2 inch holes drilled in them one foot below the normal pool water level. Any break in the cooling system piping causing a syphoning action would lower the pool level no more than one foot. At that point, assuming the check valves had failed, the 1/2 inch holes would break the syphon and prevent further draining of the pool.
Part B Demonstrate the capability to provide makeup water at the maximum required makeup rate from a seismic Category I system or its equivalent. Also, describe all other redundant or backup nakeup systems such as fire protection.
RESPONSE
The maximum makeup requirement to the spent fuel pool would exist if a total failure of the cooling system occurred following a full core off ~1oad.
The makeup flow recuirement is approximately 40 gpm.
There is a seismic Category I makeup supply to the skimmer surge tank from the condensate system, which is also seismic Category I. All connections to the skimmer surge tank except for the fuel pool cooling system line are seismic Category I up to and including the first isclation valves.
A backup makeup supply is provided by the fire protection system. Water for the fire protection system is supplied by two full capacity fire pumps. Each pump is rated at 2,000 gpm, one is diesel driven, the other motor driven.
Pressure in the system is maintained with a 50 gpm motor driven jockey pump.
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TOPIC IX-1 FUEL STORAGE MILLSTONE UNIT NO. 1 ADDENDUM PAGE 3 The connection from the fire protection system to the spent fuel pool cooling system would be made with fire hoses. A hose station in the immediate area would be conr.ected to an existing valve on the spent fuel pool cooling system designated for that purpose. Should a piping failure occur, the fire hose would be directly run to the fuel pool.
Part C Discuss the means of detecting low level and overfill conditions within the pool. Discuss the safety and seismic classification of the sensors and annunciators.
RESPONSE
A level switch (Magnetrol TS-21-NPX) monitoring pool water level is provided to alarm at high level, detect loss of water, and permit refilling of the -
pool f rom the condensate storage system.
In addition, a second level switch (Ashcroft 1901-105) located in the skimmer surge tank is provided to permit water loss detection. The fuel pool level switch is considered Category I.
However, seismic qualification of the unit, if any, is not available at.this time.
Part D Describe and discuss any portion of the spent fuel cooling system containing permanently installed piping which could lower the water level in the spent fuel. pool below the minimum safety level either by syphoning or gravity effects and the means of preventing such an occurrence.
RESPONSE
The only spent fuel cooling system piping which enters the pool are the two return pipes. Means for preventing syphoning or gravity effects are discussed in the answer to Part A above.
Part E is the spent fuel pool.(including the stainless steel liner, transfer gate and racks) seismic Category I?
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TOPIC IX-I FUEL STORAGE MILLSTONE UNIT NO. 1 ADDENDUM PAGE 4
RESPONSE
The spent fuel pool, surrounding reactor building, fuel pool gates, spent fuel racks (both previcus racks and existing racks), stain-less steel liner, and skimmer surge tanks are seismic Categofy 1 and were designed to the Class 1 design basis detailed in the FSAR.
The new high density racks and seismic restraints and the resulting impact on the spent fuel pool system were qualified to seismic Category 1.
(RE: July 15, 1976 letter; D. C. Switzer to Director Director of Nuclear Reactor Regulation, December 3, 1976 letter; D. C. Switzer to Director of Nuclear Reactor Regulation, and June 30, 1977 letter; George Lear to Northeast Nuclear Energy Company).
REQUEST The FSAR states that the new fuel storage facility is designed to prevent an accidental critical ' array, even in the event the vault becomes flooded. Verify that the KEFF does not exceed 0.98.
Also discuss the validity of the criticality analysis assuming that the new fuel experiences optimum moderation such as that provided by spray foams.
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RESPONSE
As stated in the FSAR, the spacing of fuel bundles in the new fuel storage vault maintains KEFF of 0.95 flooded. The original criticality analysis was performed by GE and is not available to NNECO at this time. The effects of spray foams on this analysis are not known.
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