ML20141M587
| ML20141M587 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 08/20/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20141M511 | List: |
| References | |
| NUDOCS 9209030014 | |
| Download: ML20141M587 (3) | |
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S_AFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 54 TO FACILITY OPERATING LICENSE NPF-68 AND AMENDMENT NO. 33 TO FACIllTY OPERATitLG LICENSE NPF-81 GEORGIA POWER COMPANY. ET AL.
V0GTLE ELECTRIC GENERATING PLANT. UNITS 1 AND_2 DOCKET NOS. 50-424 AND 50-425
1.0 INTRODUCTION
By "ELV-03576, Application for Amends to Licenses NPF-68 & NPF-81 to Revise TS 4.3.4.2.d Re Periodic Disassembly & Exam of Valves Associated W/Turbine [[Topic" contains a listed "[" character as part of the property label and has therefore been classified as invalid. Protection Sys|letter dated April 28, 1992]], as supplemented July ?0, 1992, Georgia Power Company, et al. -(the licensee) proposed license amendments to change the surveillance requirement of Technical Specification (TS) 4.3.4.2.d for Vogtle Electric Generating Plant (Vogtle), Units 1 and 2.
TS 4.3.4.2.d requires that at least one of each of the four high-pressure turbine stop valves, four high-pressure turbine control valves, six low-pressure turbine intermediate stop valves, and six low-pressure turbine inte ;ept valves be disassembled and inspected at least once every 40 months.
The proposed amendments would change this requirement so that all of these valves are disassembled and inspected at least once every 60 months.
The licensee's letter of July 20, 1992, provided additional information in support of the original request and did not change the NRC's propor,d finding of no significant hazards consideration.
2.0 BACKGROUND
The Vogtle facility uses two General Electric turbine generators; one for each unit.
Steam from the four steam generators of each unit enters the respective
-high-pressure turbine through four high-pressure steam lines.
Each line contains one turbine stop valve and one control valve in a single assembly.
After expanding through the high-pressure turbine, the steam passes through one of six moisture separator / reheaters (MSRs). A combined intermediate stop and intercept valve is located in each of the six steam lines leading from the outlet of an MSR to the inlet of one of three low-pressure turbines.
Two steam lines supply each low-pressure turbine. During operation, the valves are held open against closing springs by hydraulic fluid pressure in the valve actuators, allowing springs to close the valves.
The valves identified by TS 4.2.4.2.d are used for turbine overspeed protection.
Failure of the steam admission valves to close in any one steam line between the steam generators and the high-pre sure turbine, or between an 9209030014 920820 PDR ADOCK 0S000424 P
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l MSR and a low-pressure turbine, coincident with generator separation, would result-in a turbine overspeed condition.
A turbine overspeed condition significantly increases the probability of turbine missile generation compared to operation' at normal speed.
Regular tasting and inspection of the steam
- dmission valves reduces the probability of their failure.
a 3.0 EVALVATION Section 10.2 of the Standard Review Plan (SRP),'NUREG-0800, orovides guidance in evaluating the inservice inspection of turbine steam admission valves.
The purpose of the guidance is to ensure that the turbine overspeed protection-system will nerform in a manner which meets the requirements of General Design Criterion (GDC) 4 of Appendix A to 10 CFR Part 50 with regard to the protection of structures, systems, and components imoortant to safety from the effects of turbine missiles.
Under Vogtle's existing surveillance requirement, assuming an 18-month fuel cycle,__one stop valve, one control valve, and one combined intermediate stop and intercept valve are disassembled and inspected during every other refueling outage.
Under the proposed change, all four stop valves would be disassembled and_ inspected during one outage, all four control valves during the next outage, and the_six combined intermediate stop ana intercept valves during the third outage. Although the stop and control valves are considered to form a single assembly, they are disassembled separately.
The combined intermediate stop and intercept valves are integral units that are disassembled and inspected _ at one time.
Since each individual valve will be inspected more frequently following the proposed change,;the licensee concluded that the overall effect of the proposed change should result in increased reliability of the turbine
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overspeed protection-system.
The licensee states that the operating experience with these valves at Vogtle has been most favorable, and the valve vendor indicates that turbine steam admission valvcs_ of the type used at Vogtle have not experienced any significant generic problems. Although the proposed > change to the surveillance requirement may-reduce the probability of detecting a generic failure mode of a particular valve type, the licensee concluded that the contribution of generic failures to the total valve failure probability would ba small. - Assuming the valves are subject to random
_ failures only, the 'icensee determined that the increased frequency of inspection of. each individual valve would result in an improvement in valve reliability by a factor of'2.67.
The NRC. staff concurs with the licensee s determination that the proposed
. change should-. result in increased-reliability of the turbine overspeed protection system.
Therefore, the staff; finds that the proposad change to the Einservice testing program for the turbine steam admission valves does not-
-increase the probability of. turbine missile generation. The staff also finds that the change does not create-any additional safety concern.
Accordingly, we find'that the proposed change-complies with the requirements of GDC 4 of Appendix A to 10 CFR Part 50 with regard to the protection of structures, systems, and components important to safety from the effects of e
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..... turbine missiles and the intent of the guidance of Section 10.2 of the SRP.
The proposed change is, therefore, acceptable.
4.0 STATE CONSULTATION
In accordance with1the Commission's regulations, the Georgia State official was nctified of the proposed issuance of the amendments. The State official had no comments.
5.0 ENVIRANMENTAL CONSIDERATION The amendments change a surveillance requirement.
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 significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, ard there has been no public comment on such finding (57 FR 28201-dated June 24,1992). Accordingly, the amendments meet the eligibility 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.
6.0- CONCLUSION 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 Contributors:
D. Hood, PDII-3/DRPE S. Jones, SPLB/ DST Date: August 20, 1992 i
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