ML20214U903

Proposed Tech Specs,Allowing Installation of High Density Spent Fuel Racks to Extend Full Core Discharge Capability Beyond 1990 & Allow Savings in Radiation Exposure,Disposal of Radioactive Matl & Financial Cost

ML20214U903
Person / Time
Site:	LaSalle
Issue date:	09/19/1986
From:	COMMONWEALTH EDISON CO.
To:
Shared Package
ML20214U898	List: ML20214U897 ML20214U903 ML20214U923
References
NUDOCS 8610020014
Download: ML20214U903 (4)

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I DESIGN FEATURES 4

5.6 FUEL STORAGE CRITICALITY ,

5. 6.1.1 The spent fuel storage racks are designed and shall be maintained with:

a. A k,ff equivalent to < 0.95 when flooded with unborated water, I

including all calculational uncertainties and biases, as described in Section 9.1 of the FSAR.

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b. A nominalf-inch center-to-center distance between fuel assemblies placed in the storage racks.

5.6.1.2 The k , for new fuel for the first core loading stored dry in thespentfuel,[torageracksshallnotexceed0.95whenfloodedwithwater.

ORAINAGE 5.6.2 The spent fuel storage pool is designed and shall b'e maintained to prevent inadvertent draining of the pool below elevation 819 feet.

CAPACITY 5.6.3 The spent fuel storage pool is designed and shall be maintained with a storage capacity limited to no more than 444WL fuel assemblies.

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5. 7 COMPONENT' CYCLIC OR TRANSIENT LIMIT

5. 7.1 The components identified in Table 5.7.1-1 are designed and shall be maintained within the cyclic or transient limits of Taole 5.7.1-1.

8610020014 860919 4 DR ADOCK 0S000 LA SALLE - UNIT 2 5-5 4

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ATTAQ9EBrf C SIGNIFICANT HAZARDS CONSIDERATION Commonwealth Edison has evaluated the proposed Technical Specification Amendment and determined that it does not represent a signifi-cant hazards consideration. Based on the criteria for defining a significant hazards consideration established in 10 CPR 50.92, operation of LaSalle County Station Unit 2 in accordance with the proposed amendment will not:

1) Involve a significant increase in the probability or consequences of an l accident previously evaluated because it indicated in the safety analyses performed to support this modification, the concerns, intent and design basis of the NRC position paper "OT position for review and l acceptance of Spent Fuel Storage and Handling Applications" (Reference (e)) have been met. These analyses addressed normal, abnormal, and accident conditions in the structural, thermal-hydraulic, and criticality analyses.

i l 2) Create the possibility of a new or different kind of accident from any accident previously evaluated because the same failure mechanisms l postulated for existing racks are appropriate and were addressed for the free standing high density neutron absorber racks. CBCo concludes that the design is adequate for full pool storage of spent fuel assemblies and will maintain a subcritical array for specified external loading l conditions including a fuel drop accident. Deformations resulting from the dropping of heavy objects into the spent fuel pool or from the effects of natural events will not produce a criticality accident.

Thermal-hydraulic calculations for various fuel pool discharge cases were performed to determine the heat-up rate and time un*i1 pool boiling follwing a loss of all spent fuel pool cooling. The conclusion is that sufficient time exists for an alternate cooling source to be placed in operation following loss of cooling in any of these cases. Sufficient water makeup capability for the fuel pool is also provided for the modified rack design. The neutron absorbing material has been anlyzed to ensure sufficient boron is available (with apporpriate margin) to

. preclude criticality. Administrative controls will be established, as appropriate, to insure that the fuel pool remains within design limits for its design lifetime.

3) Involve a significant reduction in the margin of safety because the Kegg is maintained below 0.95 and results of safety analyses show the margin of safety is maintained.

The Commission has provided guidance and examples (Reference (b))

of the types of amendments that are considered not likely to involve significant hazards consideration. Example (x) relates to an expansion of the storage capacity of a spent fuel pool when all of the following are satisfied:

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(1) The storage expansion method consists of either replacing existing racks with a design which allows closer spacing between stored spent fuel assemblies or placing additional racks of the original design on the pool floor as space permits; (2) The storage expansion method does not involve rod consolidation or double tiering; (3) The X,gg of the pool is maintained less than or equal to 0.95; and

, (4) No new technology or unproved technology is utilized in either the construction process or the analytical techniques necessary to justify the expansion.

In this case, the proposed change described herein is similar to example (x) in that:

(1) The modification consists of replacing the existing racks for 1080 cells with new racks with 4073 cells. The new racks are ot a design which allows closer spacing as the method for providing the additional cells; (2) The storage expansion method does not involve rod consolidation or double tiering; (3) The K,gg of the pool with the new rack design has been analyzed and calculated to have a maximum value of 0.9441. Without design conservatisms, the Kegg is 0.8983. In any case, the Ke gg is less than 0.95; and (4) Commonwealth Edison required the contractor to perform the analyses and fabrication according to standards outlined by the NRC. In particular, the NRC guidance, " Review and Acceptance of Spent Fuel Storage and Handling Applications" dated April 14, 1978 and modifications to same, dated January 18, 1979 were followed. The contractor (U.S. Tool and Die) recently provided similar analyses and rack fabrication for another BWR whose license submittal was approved by the NRC.

Based on the preceding discussion, it is concluded that the proposed system change clearly falls within all acceptable criteria with respect to the system or component, the consequences of previously evaluated accidents will not be increased and the marigin of safety will not be decreased.

Therefore, based on the guidance provided in the Federal Register and the criteria established in 10 CFR 50.92(c), the proposed change does not constitute a significant hazards consideration.

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ATTACHMENT D SAFETY ANALYSIS REPORT 1875K l

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