ML20246P656
| ML20246P656 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 05/12/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20246P646 | List: |
| References | |
| NUDOCS 8905220249 | |
| Download: ML20246P656 (3) | |
Text
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NUCLEAR REGULATORY COMMISSION I
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WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0. 95 TO FACILITY OPERATING LICENSE NPF-9 AND AMENDMENT NO. 77 TO FACILITY OPERATING LICENSE NPF-17 1
DUKE POWER COMPANY DOCKET NOS. 50-369 AND 50-370 MCGUIRE NUCLEAR STATION, UNITS 1 AND 2
1.0 INTRODUCTION
By letter dated June 19, 1987, as supplemented February 24 and Novetter 23, 1988, and January 6,1989, Duke Power Company (the licensee) proposed amendments which would grant a one-time extension of the allowed outage time for each of the two trains of the Control Area Ventilation (VC) System to provide for sy(stem modifications to improve reliability.TS) 3.7.6 requires both inde Technical Specification in all modes. With one VC System inoperable during Modes 1, 2, 3. or 4, the TS requires the operators to restore the inoperable system to operable status within 7 isys or both McGuire Units are to be in at least Hot Standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in Cold Shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
Similarly, with one VC System inoperable during Modes 5 or 6, the operator is to restore the inoperable system to operable status within 7 days or initiate and maintain operation of the remaining operable VC System in the recirculation mode. The proposed change would add a footnote to TS 3.7.6, referenced after the specified 7 days, to state that an allowed outage time extension to 21 days is granted for each train, one at a time, to allow system modifications related to replacement of the two 50% capacity outside air filter fans with one 100% capacity fan. The system modification will be implemented during a scheduled refueling outage for one of the two McGuire units such that only one unit will be at power during the modification. No transport of toxic gas containers on site is permitted during the system modification.
2.0 EVALUATION The proposed system modifications will replace the outside air pressure filter train fans with one nuclear-grade fan per filter unit. The licensee stated that the existing fans are light-duty commercial-grade fans purchased as part of a nuclear-grade package. The licensee considers the present fans undersized for their intended duty. The result is that a high fan wheel speed i
is needed to accomplish the desired flow rate. The high running speeds have caused cracks in the fan frames and premature bearing failure. The fan manufacturer does not provide nuclear-grade replacement parts. Direct replacement would require an original design and, therefore, would be excessively costly. The licensee does not consider the existing fans reliable, based on the fact that the fans fail frequently even though preventative maintenance is performed on them and they have limited run time.
8905220249 890512 ADOCK0500gg69 DR
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' Presently, each filter train contains two 50% capacity f ans that operate in parallel. The modification will replace the two 50% capacity fans with a single 100% capacity fan per filter train.
Present parallel ducting from the fan discharge to the control room return duct will handle 100% flow, therefore, one of the existing ducts will be removed, along with its hunidity sensor, pressure switches, firestat, and flow instrumentation.
The licensee has performed a failure analysis to compare the probabilities and consequences of postulated equipment failures for the existing and post-modified systems. The function of the fi' iter train fans is to maintain, in a radiological emergency, a positive pressure in the common control room to l
prevent in-leakage of potentially contaminated (unfiltered) air and to provide for the flow of outside air (required for pressurization) through the control room area filter package. The probability of losing this function is j
dominated by the failure probabilities of the filter train fans. By replacing the two 50% capacity fans by a single 100% capacity fan, the probability of failing the above function is reduced, since failing of any one of two fans would lead to f ailure of the existing train function. Thus, the overall proability of failing to function in an emergency is reduced.
The licensee stated that the implementation risk (single train vulnerability) will be minimized by testing one train just prior to and during the 21 days that the opposite train is being modified.
This will provide increased confidence regarding proper system actuation and operation, if needed. Also, if trouble with the support systems is encountered, the operable system may be realigned to the support systems from the other unit.
The failure sequence of ECCS and containment to the extent that the filter would be required is highly unlikely.
In addition to a core melt, the operable filter train would have to fail to affect safety. Such a total failure during the additional 14 days of requested allowed outage time is not considered a credible event.
The VC outside air intakes have chlorine sensors which automatically isolate the affected intake upon detection of chlorine. These are train related and having one train down for an extended period of time will not affect the ability of the other train to isolate on chlorine detection. The licensee also stated that, as an additional precaution to further minimize the robability of a chlorine release f rom the only potential source at the site p(approximately 15150-pound bottles), the chlorine bottles will not be handled (i.e., transported) during the system modification.
Furthermore, air masks and self-contained breathing apparatus and thyroid dose blocking potassium iodide pills are readily available to the control room operators in the unlikely event that they are needed to protect the operators in a radiological or toxic gas emergency.
The staff has reviewed the licensee's submittals and, based on this review, has determined that the proposed modification to the design of the VC system
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Therefore, the proposed change to the TS is acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
These amendments involve changes to the installation or use of facility com-ponents located within the restricted area as defined in 10 CFR Part 20. The I
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 exposure. The NRC staff has made a determination that the amendments involve no significant hazards consideration, and there has been j
no public coment on such finding. 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 these amendments.
4.0 CONCLUSION
The Comission made a proposed determination that the amendments involve no significant hazards consideration which was published in the Federal Register (54 FR 7632) on February 22, 1989. The Comission consulted with the state of North Carolina. No public coments were received, and the state of North Carolina did not have any comments.
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 Comission's regulations, and the issuance of these amendments will not be inimical to the comon defense and security or to the health and safety of the public.
Principal Contributors:
D. Hood, PDlII-3/DRP-I/II C. Nichols, SPLB/ DEST Dated: !!ay 12,1989 i
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