ML20134J733
| ML20134J733 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 02/07/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20134J724 | List: |
| References | |
| NUDOCS 9702120267 | |
| Download: ML20134J733 (6) | |
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UNITED STATES y
j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20066-4001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION i
l RELATED TO AMENDMENT NO. 172 TO FACILITY OPERATING LICENSE NPF-9 AND AMENDMENT NO.154 TO FACILITY OPERATING LICENSE NPF-17 DUKE POWER COMPANY 4
MCGUIRE NUCLEAR STATION. UNITS 1 AND 2 DOCKET NOS. 50-369 AND 50-370 1
1.0 INTRODUCTION
By letter dated November 26, 1996, as supplemented December 17, 1996, Duke Power Company (the licensee) submitted a request for changes to the McGuire Nuclear Station, Units 1 and 2, Technical Specifications (TS). The requested changes would allow a one-time change in the limiting condition for operation l
(LCO) of TS 3.8.2.1 to allow on-line replacement of the existing 125-volt AT&T high specific gravity (HSG) round cell battery banks with the conventional low specific gravity (LSG) cell battery banks. While each battery bank is being replaced, a temporary battery bank composed of a new LSG cell battery bank would be installed and connected to the affected vital 125-volt dc bus so that a full complement of TS-required de configuration would remain. The proposed amendment also adds a modified performance discharge test to the battery surveillance tests and clarifies whether the battery has LSG or HSG cells in the TS and the Bases section.
4 On October 28, 1996, one of the four AT&T HSG battery banks failed its TS surveillance test, resulting in the shutdown of both McGuire units until the failed bank was replaced with a new AT&T HSG battery bank.
In order to prevent a recurrence of such a dual-unit shutdown, the licensee is planning to replace all AT&T HSG cells with new conventional LSG cells by the end of 1997.
It should be noted that in a similar amendment requesting a one-time only change in 1991, the staff granted the replacement of LSG batteries with AT&T
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HSG batteries while both units were operating at 100 percent power.
The December 17, 1996, letter provided clarifying information that did not change the scope of the November 26, 1996, application and the initial proposed no significant hazards consideration determination.
2.0 EVALUATION The purpose of the 125-volt de vitz.1 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 the de power supplies (i.e., battery banks) could result in a loss of shutdown cooling capability which, in turn, could increase the probability I
of core damage.
9702120267 970207 PDR ADOCK 05000369 P
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. Recent experience with AT&T HSG round cell batteries in the industry has shown that they are subject to both inadvertent discharges and discharges associated with TS surveillance testing. With the discharged battery, the safety i
function described above cannot be completed and the prolonged use of a discharged battery can accelerate battery degradation. Given the recent l
battery failure at McGuire, the licensee decided to replace AT&T HSG cell l
batteries with either new conventional LSG square cell (first option) or new AT&T LSG round cell (second option) batteries.
While a battery bank is being replaced on-line, the licensee plans to install a full capacity temporary LSG battery bank that will be procured through the commercial grade program for Class IE usage and sized in accordance with IEEE Std. 485-1983 and that will be connected so that the affected vital bus will remain battery-backed. The temporary battery will be installed in the Service Building due to space limitations in the battery room in the Auxiliary Building. During each battery replacement period, the remaining three vital battery banks and their associated equipment will remain in their normal configuration and will not be reconfigured for preplanned activities or routine maintenance.
The NRC staff has reviewed the proposed TS and its Bases changes for the 125-volt batteries for McGuire, Units 1 and 2.
Its evaluation of each of the proposed changes follows.
2.1 Replacement of a Footnote (#) for TS LCO 3.8.2.1 on Paae 3/4 8-12 The licensee proposes to delete the existing footnote (#) shown on items a through d in TS LC0 3.8.2.1 that was used for the replacement of the licensee's previous battery banks and to replace it with the following new footnote (#):
During periods of battery bank replacement only, the affected channel may be considered OPERABLE for up to 30 days provided a full capacity temporary battery is configured to a full capacity charger and connected to the respective bus. All limiting conditions for operation, action statements, and surveillance requirements pertaining to-the permanent batteries shall be maintained for the temporary battery during periods of battery bank replacement. This battery replacement option is only applicable once per battery bank.
On the basis of its previous experience, the licensee determined that the replacement of each vital battery bank would take approximately 30 days, with 7-day and 24-hour work coverage.
During the 30 days when a battery bank is being replaced, the licensee contends that TS LCO 3.8.2.1 is still satisfied because all four 125-volt de channels (i.e., items a through d) are operable and energized.
The licensee offered the following justifications and compensatory measures:
- 1. The 125-volt de vital power system at McGuire has been designed as a
" shared system" by having four de channels that serve Units 1 and 2. Each de channel consists of a battery bank, a full-capacity battery charger, and a 125-vn1t bus.
For each unit, two trains (A&B) are available and
t each train consists of two de channels. A cross-tie capability exists with its " associated" bus within the same train.
Each battery is sized to carry the accident loads of one unit and the safe shutdown of the other unit assuming both a loss of offsite power and a single failure in the 125-volts system. With two 100 percent batteries in each train, the McGuire-shared de system design has additional battery capacity and is not vulnerable to a single failure.
In actuality, a battery can be removed from service for the purpose of performing the replacement and still meet its safety functions.
- 2. During the 30 days, a new LSG cell full-capacity temporary battery bank composed of the standby battery charger and bus at a fifth channel will be installed and connected to the affected 125-volt bus using a temporary oparating procedure developed and approved for this purpose.
Thus, a full complement of TS-required dc channels would be available while the battery bank is being replaceo, i.e., the bus and all associated safety-related equipment remain battery-backed with a dedicated battery bank and charger at all times. Therefore, the temporary dc channel configuration maintains its TS-required train redundancy at all times.
- 3. The ambient temperature of the temporary battery room will be periodically monitored to ensure that it remains within battery specifications.
All necessary training related to the procedure will be performed prior to replacement of the first battery bank. New inter-cell connectors and inter-tier jumpers / cables will be connected and tested for connection resistance.
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Before being connected to the vital bus, the temporary battery will receive a full complement of surveillanc! measurements, including a service test.
In addition, all 7-day surveillance requirements (SRs) associated with the 125-volt dc channels would be performed for the temporary battery configuration to verify its operability.
- 5. Upon completion of a new battery installation, the battery will be charged and will receive a service test in accordance with TS SR 4.8.2.1.2.d.1.
The battery will be recharged after testing using existing station procec'ures and post-charge TS SR taken to determine operability.
Factory acceptince tests will be used to satisfy TS SR 4.8.2.1.2.e rather than performing an onsite performance discharge test (i.e., TS SR 4.8.2.1.2.e).
- 6. The size of the replacement batteries are in accordance with IEEE Std.
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45-1983, will meet the current licensing basis, and can perform the same safety function as the existing vital battery. A list of battery 4
replacement activities and the basis for their 30-day estimates were provided.
- 7. The Service Building is not a Seismic Category I structure and the temporary battery will not be seismically mounted.
In addition, the temporary battery will not be stored in an area protected from tornados or missiles, or where Equipment Qualification has been performed.
All of these factors were reviewed and were found to be insignificant when calculating the actual risk associated with the short duration of the battery replacement.
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1 i Should the temporary battery configuration become degraded and incapable of j
fulfilling the required function while a battery is being replaced, then the i
affected 125-volt channel will be declared inoperable and TS Action b.2 of LC0 3.8.2.1 will be applied, which requires the associated bus to be cross-tied to j
an operable battery bank within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> so that operating in this configuration can then be continued up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> from the time of initial j
loss of operdility.
On the basis of the 125-volt de power system design at McGuire and the l
proposed compensatory actions, the staff finds no significant decrease in margin of safety or increased risk of core damage for the proposed amendment l
request that, on a one-time only basis, allows a limited period of 30 days to i
replace the existing AT&T HSG battery bank with the conventional LSG battery i
bank. Therefore, the staff concludes that the proposed footnote (#) shown on 1
items a through d of TS LCO 3.8.2.1 is acceptable.
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2.2 Addition of Modified Performance Discharae Test in TS SR 4.8.2.1.2.e and Its Justification in the Bases Section The licensee proposes to add a modified performance discharge test in TS SR l
4.8.2.1.2.e and provides its justification in the Bases section. Under TS SR 4.8.2.1.2.e, the licensee currently requires only a performance discharge test to be performed once per 60-month interval to verify that the battery capacity is at least 80 percent of the manufacturer's rating. With a modified performance discharge test added to TS SR 4.8.2.1.2.e, a modified performance a
discharge test can be performed in lieu of a performance discharge test.
In j
the Bases section, the licensee justified that the modified performance discharge test is a combination of the performance discharge test and the j
service test that results in a more conservative surveillance test.
k Since a modified performance discharge test is permitted by IEEE Std. 450-1995
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and the latest improved Standard TS for Westinghouse plants allows either the modified performance discharge test or the performance discharge test, the staff finds the proposed addition of a modified performance discharge test in TS SR 4.8.2.1.2.e and its justification in the Bases section acceptable.
4 2.3 Interim Modification to TS and Bases Section Until the battery replacement on all four battery banks is completed in late 1997, both LSG and HSG battery banks would be in service for the McGuire 125-volt vital power system.
For clarification, the licensee proposes to modify the following TS and Bases section.
2.3.1 Modification of TS Table 4.8-3 on Paaes 3/4 8-15 and 16 Currently, the licensee naaintains two tables (Table 4.8-3 on page 3/4 8-15 and
- 16) in the TS for its battery call parameter values (limits) for electrolyte level, float voltage, and specific gravity. One table is for the previous conventional LSG square cell battery that was replaced and identified as "Gould cells;" the other table is for the AT&T HSG round cell battery identified as "AT&T cells." Since both HSG and LSG batteries will be in service for the McGuire 125-volt vital power system while the battery bank is being replaced, the licensee proposes to clarify that these Gould cells and AT&T cells should be identified more generically as low specific gravity cells
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. and high specific gravity cells, respectively.
The staff has reviewed the proposed change that specifies either LSG or HSG cells in their respective cell parameters on the two tables.
Since the cell parameter values for new LSG battery banks will be identical to those of Gould cells, the staff finds that the p'.oposed modification correctly identifies appropriate battery cell parameter values. Therefore, the staff concludes that the proposed modification is acceptable.
2.3.2 Clarification of TS Bases on Paae B 3/4 8-2 The AT&T HSG cell battery bank has a special 10-day waiting restriction to prevent another performance discharge test before the tested battery has a chance to fully recharge. Since the restriction applies to only AT&T HSG batteries, the licensee proposes to denote the difference from new LSG batteries by inserting the words "high specific gravity" and further to clarify by adding more sentences (changes are delineated) in the following TS Bases section:
In SURVEILLANCE 4.8.2.1.2.e, after the hiah specific aravity battery is returned to service (reconnected to and supplying its normal DC distribution center) following a performance discharge test (PDT), no discharge testing shall be done within 10 days on the other hiah specific aravity batteries. This is a conservative measure to ensure the tested hiah specific aravity battery is fully charged. This restriction is an interim measure until the concern regarding recovered battery capacity immediately following recharging is resolved or until replacement of these batteries with low specific aravity batteries.
i Low specific aravity batteries are not sub.iected to the 10 day l
restriction.
The proposed changes in the Bases section are temporary and will expire when all battery banks are replaced. The changes are submitted for information only and the staff finds the proposed changes acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the North Carolina State official was notified of the proposed issuance of the amendments. The State 4
official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change requirements with respect to installation or use of a i
facility component located within the restricted area as defined in 10 CFR Part 20 and 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 Commissio~n has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (61 FR
e 1 65605 dated December 13,1996). 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.
5.0 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 Contributor:
Peter Kang Date:
February 7, 1997
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