ML20206G603
| ML20206G603 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 05/03/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20206G600 | List: |
| References | |
| NUDOCS 9905100075 | |
| Download: ML20206G603 (3) | |
Text
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NUCLEAR REGULATORY COMMISSION o
l WASHINGTON, D.C. soses 0001
' SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 108 TO FACILITY OPERATING LICENSE NO. NPF-37.
4 AMENDMENT NO.108 TO FACILITY OPERATING LICENSE NO. NPF-86.
AMENDMENT NO.' 101 TO FACILITY OPERATING LICENSE NO. NPF-72.
AND AMENDMENT NO.101 TO FACILITY OPERATING LICENSE NO. NPF-77 COMMONWEALTH EDISON COMPANY j
BYRON STATION. UNIT NOS.1 AND 2 1
BRAIDWOOD STATION. UNIT NOS.1 AND 2 DOCKET NOS. STN 50 454. STN 50-455. STN 50-456 AND STN 50-457 c
1.0 INTRODUCTION
By letter dated October 30,1998, the Commonwealth Edison Company (Comed, or the licensee) submitted a request to amend the licenses for Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2. The amendments would revise the Technical Specification (TS) requirements related.to the design of the Spent Fuel Pool (SFP). TS 4.3.2, " Fuel Storage, Drainage," specifies that the SFP is designed and shall be maintained to prevent inadvertent draining of the pool below elevation 423 feet, O inches for Braidwood and 423 feet,2 inches for Bym. According to the licensee, the valuss of 423 feet,0 inches for Braidwood and 423 feet 2 incnes for Byron were based on the elevation of the siphon breaks in the SFP cooling system return lines. These TS values did not consider all of the possible failure modes of the SFP cooling system or the SFP surface skimmer system. Comed proposes to change the TS inadvertent draindown elevation to 410 feet, O inches for both stations. This elevation bounds i
the potential draindown events that could be caused by maloperation or failures of the SFP cooling system and the SFP surface skimmer system at both stations, j
2.0 EVALUATION
' The Byron and Braidwood (B/B) spent fuel pools were designed to the guidance provided by Revision 1 of Regulatory Guide (RG) 1.13, as is described in the B/D Updated Final Safety Analysis Report (UFSAR). RG 1.13 provides acceptable methods for implementing General Design Criterion 61, " Fuel Storage and Handling Criteria for Nuclear Power Plants," of Appendix A of 10 CFR 50, including the requirement for the prevention of inadvertent draining of the pool to an unacceptably low water level. Additional guidance for draindown protection is provided by the Standard Review Plan (NUREG-0800), Section 9.1.3, " Spent Fuel Pool Cooling and Cleanup System," which states the systems are acceptable if they have been designed such that in the event of failure of inlets, outlets, piping, or drains, the pool level will not be inadvertently drained below a point approximately 10 feet above the top of the active fuel.
9905100075 990503 PDR ADOCK 05000454 P
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. At Braidwood and Byron, the SFP is shared between units 1 and 2. The SFP cooling and cleanup system consists of two cooling loops and one surface-skimmer loop. To prevent a piping failure in the cooling or skimmer loops from gravity draining the SFP beicw the water level required for adequate radiation shielding, the loops are designed such that the piping connections are near the normal water level or they are provided with anti-siphon protection.
The cooling loop suction connections are approximately 6% feet below the normal water level so that a break in these lines can not gravity drain the SFP below that level. The cooling loop return lines contain an anti-siphon hole approximately 1 foot below the normal water level to prevent gravity siphoning of the SFP via these lines. The suction side of the skimmer loop uses a surface extractor that floats on the water surface. At Byron the surface extractor is limited in travel to approximately 9 feet below the normal water level (which is still approximately 16% feet above the top of the fuel), while at Braidwood the skimmer loop suction piping contains an anti-siphon hole approximately 1 foot below the normal water level. The skimmer loop discharge connections are approximately 5 to 6 feet below the normal water level.
The staff previously reviewed and approved the design of Byron and Braidwood spent fuel pools. The Byron Safety Evaluation Report (SER), NUREG-0876, states "all connections to the spent-fuel pool are either near the normal water level or are provided with antisiphon holes to preclude possible draining of the pool water," and concludes the design is acceptable. The Braidwood SER, NUREG-1002, states this conclusion is also applicable to Braidwood. The e
licensee's proposal does not involve a change to the configuration or operation of the Spent Fuel Pool.
To determine whether the proposed TS value for minimum SFP inadvertent drain down level meets the Standard Review Plan (SRP) and regulatory guide acceptance criteria, the staff evaluated scenarios where failure of the SFP cooling or skimmer loop initiated gravity siphoning of the SFP coolant. Based on the piping configuration at the Byron and Braidwood Stations, the minimum potential level in the SFP that results from an inadvertent drain down event was determined to be 415' 1/4" at Byron Station, and 417' 9 3/8" at Braidwood Station. With the maximum nominal top of stored active fuellocated at elevation 398' 8", uncovering of the stored fuel is prevented and suitable shleiding is maintained.
The staff also reviewed the B/B UFSAR fuel handling accident in the SFP and the SFP dewatering incident evaluations to ensure they were not affected by the proposed change. TS LCO 3.7.14 prohibits fuel movement at B/B with less than 23 feet of coolant above the stored fuel. Therefore, any dewatering effects from system failures would be detected and addressed by the required Actions ensuring that the fuel handling analyses remain unaffected. Likewise.
- the initial conditions for the dewatering accident analysis are not affected by this proposed TS change because they are not assumed to be coincident with the additiona! dewatering effects of postulated SFP cooling or skimmer loop fai!ures. Therefore, the current dewatering incident shielding analysis and resultant water levels over the spent fuel at B/B remain valid.
The staff has reviewed the proposed change to the B/B TSs for SFP inadvertent drain elevation and has determined that the proposed level continues to meet the guidance in RG 1.13 and SRP 9.1.3 and is, therefore, acceptable.
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3.0 STATE CONSULTATION
'In accordance with the Commission's regulations, the Illinois State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no slgnificant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the arnendments involve no -
significant hazards consideration, and there has been no public comment on such finding j
(63 FR 6g335). Accordingly, the amendments meet the t' gibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
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The Commission has 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, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: Stewart N. Bailey
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Date: May 3, 1999 1
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