ML19274G119
| ML19274G119 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 08/01/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19274G117 | List: |
| References | |
| NUDOCS 7908290680 | |
| Download: ML19274G119 (4) | |
Text
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION C
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.I 9 TO FACILITY OPERATING LICENSE NO. NPF-3 TOLEDO EDIS0N COMPANY AND CLEVELAND ELECTRIC ILLUMINATING COMPANY DAVIS-BESSE tJUCLEAR POWER STATION, UNIT N0.1 DOCKET N0. 50-346 Introduction By letter dated December 19, 1977 as supplemented April 4, June 22,1978, and May 4, 1979, the Toledo Edisen Company (TECo or the licensee) requested an amendment to Facility Operating License No. NPF-3 for the Davis-Besse Nuclear Power Station, Unit No. 1 (Davis-Besse 1).
The amendment request would revise Sections 5.3 and 5.6 of the Technical Specifications (TS) to allow an increase in the spent fuel storage capability from the existing capacity of 260 fuel assemblies (approximately 1 1/3 cores) having a maximum enrichment of 3.0 weight percent U-235, to 735 fuel assemblies (approximately 4 cores) having a maximum enrichment of 3.3 weight percent U-235.
Background
TECo proposed to modify the existing Davis-Besse 1 spent fuel pool (SFP) to allow continued operation while accommodating an expected increase in the inventory of spent fuel assemblies above the present pool capacity. The first refueling of Davis-Besse 1 is scheduled to begin about March 1,1980. The present spent fuel storage racks would be removed and replaced with new storage racks consisting of stainless steel boxes, each having 0.125 inch thick walls, sized to accept a single fuel assembly per box (cell).
The cells would be installed in rows with center-to-center spacing of 12 31/32 inches in one direction, and 13 3/16 inches in the other orthogonal direction.
2008 257 Evaluation 1.
Tuclear and Mechanical Design Aspects The licensee performed a criticality analysis of the proposed spent fuel storage racks with the assumptions of unborated water in the pool, fresh fuel in the racks with 3.3 weight percent U-235 (as compared to the original fuel having a maximum enrichment of 3.0 we ght percent U-235), and s' pool water temperature of 68 F.
The rack configuratien is infinite in all dimensions, and no credit is taken for poison other than the existing stainless steel.
The licensee has cal-79082906 @
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'. culated the effect of variation in pool temperature increase, eccentric fuel placement in the racks, and reduced pitch of the racks. A diffusion theory-transport bias was obtained by performing a transport theory calculation for the nominal case. The results of the calculation for k ff of the racks forthenominalcasewas0.92withatotaluncertaintyont0epositiveside of 0.024 including a maximum increase of 0.01 k to allow for the worst case of fuel placement eccentricity. This results 181 maximum k value of 0.944 f
which meets our acceptance criterion of 0.95 or less. Weco8Nudethatthe analysis methods are acceptable and that the results meet our acceptance criteria and are, therefore, acceptable.
The design of the proposed racks would preclude storage of fuel assemblies in other than their prescribed location. Tha proposed racks are also designed to seismic Category 1 requirements. and can withstand the maximum uplift force resuiting from a stuck fuel assembly.
Seismic design was performed with methods which have been previously reviewed a d found acceptable by the NRC staff. The proposed rack arrangement would not affect the present tornado missile and flood protection for the spent fuel storage facility as there would be no structural changes made to the present pool design.
Since the supports of the proposed fuel racks extend higher than the fuel elements, the dropping of a fuel bundle would cause the same damage as previously assumed and therefore the calculated potential dose would not change with respect to what was previously accepted. The proposed rack design thus meets our criteria and we find it acceptable.
The licensee has performed a design basis heat load calculation to demonstrate that the existing SIP cooling system is able to handle the increased cooling requirement resulting from the proposed additional spent fuel storage. The decay heat' generated by the spent fuel is calculated on the basis that the average discharge batch would be 60 fuel assemblies which have undergone an average continuous operating period for 3 years at 2772 MWt discharging into the SFP after 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> of decay. We have evaluated the increased heat load for maximum normal refueling heat load conditions on the basis of annual refueling of the reactor.
Our evaluation verifies that the increased heat load resulting from the storage of 8 additional fuel batches (4 years and older) would be insignificant (less than 2% of the original design heat load) and that the existing pool cooling system would maintain the water temperature below 125 F, which is acceptable.
We have also reevaluated the increased heat load under abnormal conditions resulting from one entire core being discharged 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> after shutdown, 65 days after the last of 9 annual refueling batches. Under this condition, the residual heat removal (RHR) system would be used to remove the decay heat from the SFP.
Our evaluation verifies that the RHR system would be able to maintain the pool water temperature at 140 F and is acceptable. We therefore conclude that the e <ist ino S FP cooling system and the RHR system are adequate.
An increase in spent fuel storage capacity has not led to increased concentrations of radionuclides in the S FP water at other operating plants.
Measurements taken of the activity in the pool water before and after refueling have indicated essentially no change in concentrations of the impurities. We, therefore, find the existing purification portion of the system is adequate to perform its function.
2008 258
. The proposed increase in spent fuel storage capacity would have essentially no impact on the concentration of radioactivity in the air of the fuel building or heat load on the fuel building ventilation system.
No modification to this system is required in support of this change.
We had previously found the design for the SFP cooling and purification system, and the fuel handling building ventilation system to be acceptohle, and reach the same conclusion now.
2.
Material Aspects Since the possibility of long-term storage of spent fuel exists, we are investigating on a generic basis the effects of the pool envir7nment on the racks, fuel cladding and pool liner.
Based upon our preliminary review and previous operating experience, we have concluded that at the pool temperature which will be experienced and the quality of the demineralized water, and taking no credit for inservice inspection, there is reasonable assurance that no significant corrosion of the racks, the fuel cladding or the pool liner will occur over the lifetime of the plant.
However, if the results of the current generic review indicate that additional protective measures are warranted to protect the racks, the fuel cladding and/or the liner from the effects of corrosion, the necessary steps and/or inspection programs will be required to assure that an acceptable level of safety is maintained. Any conceivable problems which could be uncovered are of a long-term nature and warrant no need for immediate concern.
3.
Fuel Handling The NRC staff has under way a generic review of load handling operations in the vicinity of SFPs to determine the likelihood of a heavy load impacting fuel in the pool and. if neconsarv. the radiological consequences of such an ovent.
Because the licensee is required to prohibit loads greater than the weight of a fuel assembly plus the associated handling tool to be transported over spent fuel in the Davis-Besse 1 SFP, we have concluded that the likelihood of a heavy load handling accident is sufficiently small that the proposed modification is acceptable and no additional restrictions on load handling operations 'n the vicinity of the SFP are necessary while our review is under way.
The consequences of fuel handling accidents in the SFP area are not changed from those presented in the Safety Evaluation (SE) dated December 1976.
4.
Occupational Radiation Exposure 20%
25c)
We have reviewed the licensee's plan for the removal and disposal of the low density racks and the installation of the high density racks with respect to occupational radiation exposure.
Although the proposed modification will be completed prior to placement of irradiated fuel into the pool, the SFP water has been contaminated with low level quantities of radionuclides during transfer of contaminated burnable poison rod assemblies from the pool to the adjacent cask pit for storage.
It will, therefore, be necessary to decontaminate the existing low density racks prior to their removal dnd disposal, as Well as the walls and floors of the pool prior to installation of the new high density racks.
These actions iill be necessary in order to achieve as low as reasonably achiev4 fe exposure to
. to personnel during the modification. The licensee estimates that the occupational exposures during the modification will be about 5 man-rem. We believe this to be a reasonable estimate based on relevant exoerience of SFP modifications of other licensees who have performed this operation in similar radiation fields. Therefore, with proper decontamination of the low density fuel racks and the SFP area, the modifications will be perforn,ed with as low as reasonably achievable occupational exposure.
We have estimated the increment in onsite occupational dose resulting from the proposed increase in stored fuel assemblies on the basis of information supplied by the licensee and by utilizing relevant assumptions for occupancy times and for dose rates in the spent fuel area from radionuclide concentrations in the SFP water. The spent fuel assemblies themselves contribute a negligible amount to dose rates in the pool area because of the depth of water shielding the fuel.
The occupational radiation exposure resulting from the proposed action represents a negligible burden.
Based on present and projected operatinns in the SFP area,we estimate that the proposed modification should add less than one percent of the total annual occupational radiation exposure burden at this facility. The small increase in radiation exposure will not affect the licensee's ability to maintain individual = cupational doses to as low as is reasonably achievable and within the limits of 10 CFR Part 20. Thus, we conclude that storing additional fuel in the SFP will not result in any significant increase in doses received by occupational workers.
5.
Radioactive Waste Treatment The plant contains waste treatment systems designed to collect and process the gaseous, liquid, and solid wastes that might ccntain radioactive material. The waste treatment systems were evaluated in the SE dated December 1976. There will be no change in the waste treatment systems or in the conclusions of the evaluation of these sy " ems as described in Section 11.0 of the SE because of the proposed modification.
6.
Conclusion Based on our review, we conclude that the proposed modified high density fuel storage design of 735 fuel assemblies having a maximum enrichment of 3.3 weight percent U-235 meets the requirements of General Design Criterion 61 of Appendix A to 10 CFR Part 50, and the positions of Regulatory Guide 1.13, " Fuel Storage Facility Design Basis," and Regulatory Guide 1.29, " Seismic Design Qualification,"
and is, therefore, acceptable.
Based on the conclusion of our evaluation, we find that the proposed chenges to Sections 5.3, 5.6 and 3.9.3 of the plant TS are acceptable.
We have concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Dated:
August 1,1979 2006
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