ML19256D698
| ML19256D698 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 08/02/1977 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19256D693 | List: |
| References | |
| NUDOCS 7910220615 | |
| Download: ML19256D698 (2) | |
Text
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THREE w lE ISLAND NUCLEAP STATION UNIT c REVIEW 0F SPENT FUEL PC^L MODIFICATION SAFETY EVALUATION REPORT ENGINEERING BRANCH DIVISION OF OPERATING REACTORS Pescriotion of Modification The proposed modification of spent fuel storage cspacity will involve the installation of new high density storage racks in the currently empty "B" spent fuel pool. The new storage racks will be constructed from strr tu-al stainless steel, type 304, and are designed to seismic Category I criteria.
The new racks consist of a rectangular array of storage cells welded to two lattices of structural stainless steel channel, located near the top and bottom of the cells. The lattice work of stainless steel channel, limits structural deformation and maintains a nominal center-to-center spacing of 13.625 inches between adjacent storage cells. The fuel cells have a square cross section with a 9.12 inch I.D. and a.187 inch wall thickness. The new racks are supported by the existing "B" pool floors and walls and utilize compression type restraints with pads at the points of contact with the pool liner.
A general description of the rack assembly is given in Sections 2.2 and 3.0 of the report " Spent Fuel Pool Modification Description and Safety Analysis" submitted by Metropolitan Edison Company.
Aspects of Review Structural and Mechanical The new spent fuel storage rack designs were reviewed for the following; structural design and analyses procedures for all loads including seismic and impact loadings; supporting arrangements for the racks including their restraints; loading combinations and structural acceptance criteria; quality control for design, fabrication and installation; in accordance with the applicable parts of Sections 3.7 and 3.8 of the Standard Review Plan.
Seismic analyses of the fuel storage racks were performed using a response spectrum modal dynamic analysis, enveloped over the elevation changes, in the two horizontal directions and a static seismic analysis in the verticle direction in accordance with Section 3.7 of the Standard Review Plan.
The modal Responses for each horizontal direction and the combination of each of the in pendent direction results were arrived at in accordance with Regt. atory Guide 1.92.
The effective mass of the water and the fuel-cell interaction were also included in the seismic analyses.
The existing pool structure was analyzed, using a finite element model, for the increased loading conditions imposed by the new high density storage racks and all loadings and load combinations were in accordance with Section 3.8.4 of the Standard Review Plan.
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Material The spent fuel pool racks, their associated hardware, the seismic restraints, and the pool liner are all constructed of stainless steel.
Because the possibility of long term storage of spent fuel exists the effects of the pool environment on the racks, fuel cladding and the pool liner have been investigated.
Based on our preliminary review and operating experience we have concluded that at the pool temperature and quality of demineralicad pool water, and taking no credit for inservice inspection, there is reasonable assurance that no significant corrosion of the racks, fuel cladding or pool liner over the lifetime of the plant will occur.
However, this issue is still under generic review by the Regulatory Staff.
If the results of this investigation indicate that additional protective measures are warrented to protect the racks, fuel cladding and liner from the effects of corrosion, we will determine what steps or inspection programs are necessary to assure that an acceptable level of safety is maintained.
Evaluation f
Analyses, design, fabrication and installation of the proposed racks are in accordance with accepted criteria, and are in conformance with the rules of ASME Boiler and Pressure Vessel Code and AISC " Specification for Design, Fabrication and Erection of Structural Steel for Buildings" including supplements 1, 2 and 3.
The racks were designed as Category I Eauipment. Welding is performed in accordance with Section IX of the ASME Boiler and Pressure Vessel Code.
i The effects of the additional loads on the existing pool structure due to the high density storage assemblies have been examined and the pool structural integrity and leak tightness were determined to be adequate under the new loading conditions.
There is no existing evidence at this time to indicate that corrosion of the stainless steel racks or liner will ocurr at the temperatures and quality of the demineralized water present in this pool.
We find that the proposed modification submitted by the licensee is acceptable, and in part satisfies the requirements of general design criteria 2, 4 and 61.
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I MEMORANDUM FOR:
K. R. Goller, Assistant Director for Operating Reactors, D0R FROM:
L. C. Shao, Chief. Engineering Branch, 00R
SUBJECT:
THREE MILE ISLAND UNIT 1 - SPENT FUEL POOL MODIFICATION DESCRIPTION AND SAFETY ANALYSIS Plant Name: Metropolitan Edison C:impany - Three Mile Island Nuclear Station Unit 1 NSSS Vendor:
Docket Number: 50-289 Requested Completion Date: 4pttmb6r 15771977
- Operating Reactors Branch and Project Manager: ORB 4; G. Zwetzig Operating Techn61ogy Brns::hes Involved: Engineering Branch,
' Plant Systems Branch, Environmental Evaluation Branch
- Description of Task: Review of Spent Fuel Pool Modification Review Status: Complete._,, ' ;" ; -
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l The Engineering Branch, Division of Operating Reactors, has reviewed
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the structural, mechanical and materials aspects of the infomation submitted tty Metropolitan Edison Company in a report entitled:"Three Mile Island Nuclear Station Unit 1 Spent Fuel Pool Modification Description and Safei;y Analysis" dated January 1977 and in Supplemental infomation dated May 24, 1977 and July 21, 1977. Our Safety Evaluation is contained in the enclosure.
L. C. Shao, Chief Engineering Branch
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Division of Operating Reactors Enclosure-
~As stated 1453 061
Contact:
S. Hosford
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