ML20097B623
| ML20097B623 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 02/01/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20097B619 | List: |
| References | |
| NUDOCS 9602070190 | |
| Download: ML20097B623 (5) | |
Text
{{#Wiki_filter:_. pm k UNITED STATES p j NUCLEAR REGULATORY COMMISSION g WASHINGTON, D.C. 20066-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.163 TO FACILITY OPERATING LICENSE NPF-9 AND AMENDMENT NO.145 TO FACILITY OPERATING LICENSE NPF-17 DUKE POWER COMPANY MCGUIRE NUCLEAR STATION. UNITS 1 AND 2 DOCKET NOS. 50-369 AND 50-370 1.0 BACKGR@!El By letter of August 20, 1992, as supplemented by letter dated December 5, 1995, Duke Power Company (DPC or the licensee) submitted a request for changes to the McGuire Nuclear Station, Units 1 and 2, Technical Specifications (TS). The requested changes would revise the TS for the 125-volt battery Surveillance Requirement (SR). The proposed amendments delete the words "during shutdown" from SR 4.8.2.1.2.e, which requires that each battery be subjected to a performance discharge test (PDT) during shutdown at least once per 60 months. The PDT is a constant current capacity test for a battery to detect any change in the battery capacity after being in service and the PDT is performed regularly to verify that the battery capacity is at least 80 percent of the manufacturer's rating. The licensee finds that performing the battery PDT during shutdown in accordance with SR 4.8.2.1.2.e is impractical because it requires shutdown of both McGuire units. 2.0 EVALUATION The purpose of the de power system in nuclear power plants is to provide control and motive power to valves, instrumentation, emergency diesel generators, and many other components and systems during all phases of plant operation, including abnormal shutdown and accident situations. The failure of de power supplies could result in a loss of shutdown cooling capability which, in turn, could increase the probability of core damage. Since a single failure of any de component (e.g., de bus, battery, and battery charger) in one unit could affect the de system from performing its intended safety function of the other unit, the current de power system design in multi-units does not allow for sharing. In addition, the A0T for an inoperable de component in the current version of the standard TS allows power operation to continue only for two hours. With the two hour A0T, most licensees find that the battery PDT needs to be performed when the unit is shut down. ng2Sgggggggg P
. 2.1 Deletion of the Words "Durina Shutdown" From TS SR 4.8.2.1.2,e The licensee proposes to delete the words "during shutdown" from SR 4.8.2.1.2.e, which states that: At least once per 60 months, during shutdown, by verifying that the battery capacity is at least 80 percent of the manufacturer's rating when subjected to a performance discharge test. Once per 60-month interval, this performance discharge test may be performed in lieu of the battery service test required by Specification 4.8.2.1.2.d. With one battery and/or battery charger inoperable, Action Statement b.2 of LCO 3.8.2.1 in the current McGuire TS allows unit operation to be continued for up to 72 hours, as long as the associated bus is energized with an operable battery bank via operable tie breakers within two hours. With a 1-hour discharge rate of 758 amps and an accelerated recharge procedure used for the test, the licensee finds that the PDT can be conducted and the battery can be fully recharged within the 72-hour A0T. Therefore, the licensee believes that there is no reason that SR 4.8.2.1.2.e should be performed only during the shutdown of both units. The licensee has reviewed the design of the 125-volt de power system, the i current TS provisions, and pertinent regulatory guides (RGs) applicable to the McGuire licensing basis and finds that: 1. The 125-volt de system at McGuire has been designed as a " shared system" by having four batteries, chargers, and distribution centers (EVDA, EVDB, EVDC, and EVDD) that serve two units. A dedicated battery and chargers are connected to each distribution center, which in turn feeds power to the two de power panel boards and two static inverters for both units. The loads served from four distribution centers are all safety-related and unitized; one group, consisting of a dc panel board and an inverter, serves Unit 1, and another group serves Unit 2. These unitized panel boards allow independence and separation between the engineered safety feature (ESF) loads for each unit. 2. Two distribution centers (EVDA and EVDC) can be tied together since they are of the same train (i.e., Train A). Likewise, distribution centers (EVDB and EVDD) can be tied together because they are of the same train (i.e., Train B). For the removal of a battery and its associated charger for maintenance or testing, a spare (the fifth) battery charger has been provided:to replace the associated battery charger by closing appropriate key interlock circuit breakers. This alignment is controlled by approved procedures. Therefore, train redundancy is maintained at all times. 3. Each train has two batteries, and each battery is sized to carry the accident loads of one unit plus the safe shutdown of the other unit for one complete train, assuming a loss of offsite power. Coordination also exists such that a fault at the system level on the non-accident unit will not affect the ability to supply ESF loads to the non-accident unit and safely shutdown the other unit in the event of a loss of offsite power.
i j I j t j 4. In the 1977 edition of RG 1.32, " Criteria for Safety-Related Electric Power Systems.for Nuclear Power Plants," position C.2.a states that shared electric systems for multi-unit stations are unacceptable except as i specified in RG 1.81, " Shared Emergency and Shutdown Electric Systems for Multi-Unit Nuclear Power Plants." However, for multi-unit plants under construction with permit applications prior to June 1, 1973, position C.2 j of RG 1,81 permitted the staff to review each request on an individual case basis. 4 5. Because the McGuire construction permit was granted on February 28, 1973, the McGuire's shared de system is committed to the earlier RG 1.32, Rev. l 0, 1972. RG 1.81 is not in the McGuire licensing basis. 6. Nevertheless, the concern about sharing the 125-volt de system between the ~ j units at McGuire with respect to position C.2 of RG 1.81 was identified as i an open item in the original Safety Evaluation Report (SER). Subsequently, l the staff sought additional information. The staff closed this issue in Supplement 1 of the SER in 1978. i On the basis of the above information, the licensee states that the 125-volt. l de shared system design at McGuire is not only permitted by the licensing j basis but also is not vulnerable to a single failure because of the additional battery capacity and train redundancy. The licensee further states that even j during a 72-hour A0T, the single failure of any components of either train { (including an emergency diesel generator) will still leave a full capacity train available to provide vital instrumentation and control power for both { units. Therefore, the staff finds that a battery can safely be removed from service for the purpose of performing the PDT for the battery without i presenting appreciable risk. On this basis, the staff concludes that the proposed removal of the words "during shutdown" from SR 4.8.2.1.2.e is j acceptable. However, during the review of the amendment, the staff found that McGuire's i square cell batteries have been replaced with new AT&T round cell batteries. With new AT&T round cell batteries installed, the staff has raised the following two TS concerns: 1. Adequacy,of the 72-hour A0T following a PDT (deep discharging) to restore or returm the ba,ttery capacity to its pre-test condition. /, m.s 2. Because the. capacity!of new AT&T round cells would not drop below ~ publisNedcrates for the guaranteed life of the cell as their capacity increases with.uagek the staff believes that the battery replacement (SR 4.8.2'.1.Z.e) and degradation (SR 4.8.2.1.2.f) criteria in the TS should be modified to reflect its consistency with other operating plants (e.g., Palo Verde, Byron, and Braidwood), which installed the AT&T round cells of 4 the same design. To resolve these concerns, the licensee committed to interact with the battery j vendor to determine how long the battery will take to recover its capacity i immediately following the POT; the licensee also committed to interact with appropriate industry groups to resolve the battery replacement and degradation
F critefiafortGeilT&T.roundcells. The licensee will provide an update on this, issue to NRC by June 30, 1996, and periodically thereafter. Until the issue M arding recovered battery capacity after PDT is resolved, the licensen, as an interin measure, has proposed that no discharge test shall be performed within 10 days on the remaining three batteries to ensure the tested batterf is fully charged, and this commitment is reflected in the TS n j 3/4.8.2 BASES section by adding the following paragraph: i In SURVEILLEM Of.2.1.2.e, after the battery is returned to service (re-connected to and supplying its normal DC distribution center) i following a perfonnance discharge tests (PDT), no discharge testing shall be done within 10 days on the other three batteries. This is a conservative measure to ensure the tested battery is fully charged. i This restriction is an interim measure until the concern regarding l recovered battery capacity immediately following recharging is i' resolved. The staff has reviewed the above compensatory action and finds it prudent and acceptable. When the battery recharging issue is resolved, the above paragraph should be removed from the Bases section.
3.0 STATE CONSULTATION
In accordance with the Commission's regulttions, the North Carolina State official was notified of the proposed issuance of the amendments. The State official had no comments., 4.0 ENVIR0leiENTAL CONSIDERA1 ION The amendments change surveillance requirements. 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, and there has been no public comment on such finding (60 FR 65677 dated December 20,1995). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9)w Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessmen(t need be prepared in connection with the issuance of the amendments'. i
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5.0 CONCLUSION
The Commission has concTuded, 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: P. Kang I Date: February 1, 1996 9 s =#}}