Information Notice 2013-05, Battery Expected Life and Its Potential Impact on Surveillance Requirements: Difference between revisions

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==ADDRESSEES==
==ADDRESSEES==
All holders of an operating license or construction permit for a nuclear power reactor under
All holders of an operating license or construction permit for a nuclear power reactor under Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel.
 
Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of
 
Production and Utilization Facilities, except those who have permanently ceased operations
 
and have certified that fuel has been permanently removed from the reactor vessel.


All holders or applicants for a combined license under 10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants.
All holders or applicants for a combined license under 10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants.


==PURPOSE==
==PURPOSE==
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform addressees about recent issues involving licensees nonconservative technical specifications (TSs) regarding surveillance requirements (SRs) for direct current (DC) power systems due to reductions in battery expected life. The NRC expects that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems.
 
addressees about recent issues involving licensees nonconservative technical specifications
 
(TSs) regarding surveillance requirements (SRs) for direct current (DC) power systems due to
 
reductions in battery expected life. The NRC expects that recipients will review the information
 
for applicability to their facilities and consider actions, as appropriate, to avoid similar problems.


Suggestions contained in this IN are not NRC requirements; therefore, no specific action or
Suggestions contained in this IN are not NRC requirements; therefore, no specific action or written response is required.
 
written response is required.


==BACKGROUND==
==BACKGROUND==
Class 1E batteries are used to supply DC loads at nuclear power plants and are designed
Class 1E batteries are used to supply DC loads at nuclear power plants and are designed consistent with the requirements in General Design Criterion (GDC) 17, Electric Power Systems, and GDC 18, Inspection and Testing of Electric Power Systems, of Appendix A, General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50 or similar plant-specific design criteria.
 
consistent with the requirements in General Design Criterion (GDC) 17, Electric Power
 
Systems, and GDC 18, Inspection and Testing of Electric Power Systems, of Appendix A,
General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50 or similar plant-specific


design criteria.
The Class 1E batteries are lead-acid batteries which degrade over time, primarily as a result of the buildup of lead sulfates on the plates. The battery manufacturers typical expected battery life curve indicates a 100 percent battery capacity over the initial 14 years of service. The capacity then decreases to 80 percent at the end of the expected 20-year life. At this point, the Institute of Electrical and Electronics Engineers (IEEE) Standard (Std.) 450-2002, IEEE


The Class 1E batteries are lead-acid batteries which degrade over time, primarily as a result of
Recommended Practice for Maintenance, Testing, and Replacement of Vented Lead-Acid Batteries for Stationary Applications, as endorsed by Regulatory Guide 1.129, Maintenance, Testing, and Replacement of Vented Lead-Acid Storage Batteries for Nuclear Power Plants, recommends replacing the battery bank. To account for this degradation, IEEE Std. 485-1997, IEEE Recommended Practice for Sizing Lead-Acid Batteries for Stationary Applications, as endorsed by Regulatory Guide 1.212, Sizing of Large Lead-Acid Storage Batteries, recommends that when sizing batteries for use at nuclear power plants, the rated capacity of the battery, when put in service, should be at least 125 percent of the design load. This ensures that at least 80 percent of the battery nameplate capacity will be available at the end of the 20-year expected life of the batteries, which will be sufficient to serve 100 percent of the design load (80 percent of 125 percent equals 100 percent).


the buildup of lead sulfates on the plates. The battery manufacturers typical expected battery
The NRC requires licensees to maintain batteries in an operable condition as specified in plant TS. As such, the batteries must be capable of performing their intended function of supplying 100 percent of design DC loads. Standard TSs have a SR to Verify battery capacity is  80% of the manufacturer's rating when subjected to a performance discharge test or a modified performance discharge test. The specified frequency of this surveillance is 60 months AND 12 months when battery shows degradation, or has reached 85% of the expected life with capacity < 100% of manufacturers rating AND 24 months when battery has reached 85% of the expected life with capacity  100% of manufacturers rating. Note that the surveillance frequency uses the term expected life but does not include a specific value (e.g., 20 years).


life curve indicates a 100 percent battery capacity over the initial 14 years of service. The
Because of this, licensees may not be immediately aware of the impact changes to the expected life of their Class 1E batteries can have on their plants TS SRs.
 
capacity then decreases to 80 percent at the end of the expected 20-year life. At this point, the
 
Institute of Electrical and Electronics Engineers (IEEE) Standard (Std.) 450-2002, IEEE
 
Recommended Practice for Maintenance, Testing, and Replacement of Vented Lead-Acid
 
Batteries for Stationary Applications, as endorsed by Regulatory Guide 1.129, Maintenance, Testing, and Replacement of Vented Lead-Acid Storage Batteries for Nuclear Power Plants, recommends replacing the battery bank. To account for this degradation, IEEE Std. 485-1997, IEEE Recommended Practice for Sizing Lead-Acid Batteries for Stationary Applications, as
 
endorsed by Regulatory Guide 1.212, Sizing of Large Lead-Acid Storage Batteries, recommends that when sizing batteries for use at nuclear power plants, the rated capacity of the
 
battery, when put in service, should be at least 125 percent of the design load. This ensures
 
that at least 80 percent of the battery nameplate capacity will be available at the end of the
 
20-year expected life of the batteries, which will be sufficient to serve 100 percent of the design
 
load (80 percent of 125 percent equals 100 percent).
 
The NRC requires licensees to maintain batteries in an operable condition as specified in plant
 
TS. As such, the batteries must be capable of performing their intended function of supplying
 
100 percent of design DC loads. Standard TSs have a SR to Verify battery capacity is  80%
of the manufacturer's rating when subjected to a performance discharge test or a modified
 
performance discharge test. The specified frequency of this surveillance is 60 months AND
 
12 months when battery shows degradation, or has reached 85% of the expected life with
 
capacity < 100% of manufacturers rating AND 24 months when battery has reached 85% of the
 
expected life with capacity  100% of manufacturers rating. Note that the surveillance
 
frequency uses the term expected life but does not include a specific value (e.g., 20 years).
 
Because of this, licensees may not be immediately aware of the impact changes to the
 
expected life of their Class 1E batteries can have on their plants TS SRs.


==DESCRIPTION OF CIRCUMSTANCES==
==DESCRIPTION OF CIRCUMSTANCES==
In the examples below, the licensees discovered conditions that either increased battery design
In the examples below, the licensees discovered conditions that either increased battery design loads or decreased rated battery capacity such that the battery no longer met the sizing design basis. The batteries remained operable, at least in the near term, as the batteries were still capable of supplying 100 percent of the design DC loads. However, the licensees did not recognize the need to ensure the expected life of Class 1E batteries appropriately accounted for the sizing requirements and post-accident DC loading assumptions contained in design basis documents. As a result, certain TS SR testing frequencies, specifically those associated with performance or modified performance discharge testing, were non-conservative.
 
loads or decreased rated battery capacity such that the battery no longer met the sizing design
 
basis. The batteries remained operable, at least in the near term, as the batteries were still
 
capable of supplying 100 percent of the design DC loads. However, the licensees did not
 
recognize the need to ensure the expected life of Class 1E batteries appropriately accounted
 
for the sizing requirements and post-accident DC loading assumptions contained in design
 
basis documents. As a result, certain TS SR testing frequencies, specifically those associated
 
with performance or modified performance discharge testing, were nonconservative.


===Cooper Nuclear Station===
===Cooper Nuclear Station===
On March 11, 2009, the licensee for Cooper Nuclear Station submitted a license amendment
On March 11, 2009, the licensee for Cooper Nuclear Station submitted a license amendment request to address non-conservative TSs regarding the SRs for 125 volt (V) and 250 V DC power systems. During its review of the amendment, the NRC staff noted that a reduction in the expected service life would be needed to ensure the batteries would be capable of providing 90 percent of their rated capacity at the end of their service life. The NRC issued a request for additional information that requested the licensee to describe the impact of this change on the expected life of Cooper Nuclear Station batteries (e.g., conclusions drawn from the battery life versus capacity curve for the batteries).
 
request to address nonconservative TSs regarding the SRs for 125 volt (V) and 250 V DC
 
power systems. During its review of the amendment, the NRC staff noted that a reduction in the
 
expected service life would be needed to ensure the batteries would be capable of providing 90
percent of their rated capacity at the end of their service life. The NRC issued a request for
 
additional information that requested the licensee to describe the impact of this change on the
 
expected life of Cooper Nuclear Station batteries (e.g., conclusions drawn from the battery life
 
versus capacity curve for the batteries).
 
In its response to the NRC staffs request for additional information, the licensee noted that as
 
loads have increased over time, the required battery capacity is now closer to 90 percent of the
 
nameplate rating. The licensee further stated that its battery vendor does not estimate battery
 
life for 90 percent capacity. Therefore, the licensee conservatively established 15 years as the
 
point at which the batteries reach 85 percent of expected life. The licensee also conservatively
 
defined battery degradation to be when capacity drops by more than 5 percent (normally 10
percent as defined by the IEEE Std. 450-2002,) relative to the capacity on the previous
 
performance test or when the battery capacity reaches less than or equal to 95 percent of the
 
manufacturers rating (normally 90 percent or when it is 10 percent below the manufacturers
 
rating as defined by IEEE Std. 450-2002). On March 18, 2010, the NRC issued the above mentioned license amendment for Cooper
 
Nuclear Station. To address the above concern, the NRC staff required the licensee to update
 
its updated safety analysis report and TS bases for the batteries upon implementation of the
 
approved license amendment. These updates included the reduction to 15 years as the point at
 
which the safety-related batteries have reached 85 percent of expected life. See the licensee


amendment issuance package for further details (Agencywide Documents Access and
In its response to the NRC staffs request for additional information, the licensee noted that as loads have increased over time, the required battery capacity is now closer to 90 percent of the nameplate rating. The licensee further stated that its battery vendor does not estimate battery life for 90 percent capacity. Therefore, the licensee conservatively established 15 years as the point at which the batteries reach 85 percent of expected life. The licensee also conservatively defined battery degradation to be when capacity drops by more than 5 percent (normally 10 percent as defined by the IEEE Std. 450-2002,) relative to the capacity on the previous performance test or when the battery capacity reaches less than or equal to 95 percent of the manufacturers rating (normally 90 percent or when it is 10 percent below the manufacturers rating as defined by IEEE Std. 450-2002). On March 18, 2010, the NRC issued the above mentioned license amendment for Cooper Nuclear Station. To address the above concern, the NRC staff required the licensee to update its updated safety analysis report and TS bases for the batteries upon implementation of the approved license amendment. These updates included the reduction to 15 years as the point at which the safety-related batteries have reached 85 percent of expected life. See the licensee amendment issuance package for further details (Agencywide Documents Access and Management System (ADAMS) Accession No. ML100610233).


Management System (ADAMS) Accession No. ML100610233).
===Indian Point Nuclear Generating, Unit 2 (IP2)===
On March 29, 2009, the licensee for IP2 submitted a license amendment request to address non-conservative TSs regarding SR 3.8.6.6 in TS section 3.8.6, Battery Parameters, for 125 V DC power systems. The SR verifies battery capacity during a performance discharge test or a modified performance discharge test. The licensee discovered that the 80 percent capacity value was non-conservative with respect to the existing design basis calculation for battery capacity under minimum design temperature conditions. The licensee determined that it should implement a more restrictive battery acceptance criterion ( 85 percent of manufacturers rating) to ensure that sufficient battery capacity exists at limiting conditions. During its review of the amendment, the NRC staff identified that the licensee for IP2 applied a 117.6 percent (1.176) aging factor in its design calculation for sizing the Class 1E batteries. While the aging factor is less than that recommended by IEEE Std. 485-1997, the licensee followed this guidance since the aging factor is appropriate for the assumed end-of-life criterion (i.e., 85 percent). However, based on standard battery life versus capacity curves, the licensee noted that aging these batteries to 85 percent of rated capacity would indicate an expected battery life of approximately 18 years versus 20 years originally assumed.


Indian Point Nuclear Generating, Unit 2 (IP2)
On February 24, 2010, the NRC issued the above mentioned license amendment for IP2. To address the above concern, the NRC staff required the licensee to update its battery monitoring and maintenance program, TS bases for the batteries, and updated final safety analysis report upon implementation of the approved license amendment. These updates included the reduction to 18 years as the expected life of their safety-related batteries. See the licensee amendment issuance package for further details (ADAMS Accession No. ML100270051).
On March 29, 2009, the licensee for IP2 submitted a license amendment request to address
 
nonconservative TSs regarding SR 3.8.6.6 in TS section 3.8.6, Battery Parameters, for 125 V
 
DC power systems. The SR verifies battery capacity during a performance discharge test or a
 
modified performance discharge test. The licensee discovered that the 80 percent capacity
 
value was nonconservative with respect to the existing design basis calculation for battery
 
capacity under minimum design temperature conditions. The licensee determined that it should
 
implement a more restrictive battery acceptance criterion ( 85 percent of manufacturers rating)
to ensure that sufficient battery capacity exists at limiting conditions. During its review of the
 
amendment, the NRC staff identified that the licensee for IP2 applied a 117.6 percent (1.176)
aging factor in its design calculation for sizing the Class 1E batteries. While the aging factor is
 
less than that recommended by IEEE Std. 485-1997, the licensee followed this guidance since
 
the aging factor is appropriate for the assumed end-of-life criterion (i.e., 85 percent). However, based on standard battery life versus capacity curves, the licensee noted that aging these
 
batteries to 85 percent of rated capacity would indicate an expected battery life of approximately
 
18 years versus 20 years originally assumed.
 
On February 24, 2010, the NRC issued the above mentioned license amendment for IP2. To
 
address the above concern, the NRC staff required the licensee to update its battery monitoring
 
and maintenance program, TS bases for the batteries, and updated final safety analysis report
 
upon implementation of the approved license amendment. These updates included the
 
reduction to 18 years as the expected life of their safety-related batteries. See the licensee
 
amendment issuance package for further details (ADAMS Accession No. ML100270051).


==DISCUSSION==
==DISCUSSION==
Licensees rely on Class 1E batteries to supply DC loads when battery chargers are not
Licensees rely on Class 1E batteries to supply DC loads when battery chargers are not available. The batteries are sized in accordance with IEEE Std. 485-1997 to carry the expected shutdown loads following a plant trip and a loss of all alternating current power without battery terminal voltage falling below its minimum required voltage. This ensures that adequate DC power will be available for starting and loading the emergency diesel generators, emergency power to run instrumentation and controls, and emergency lighting.
 
available. The batteries are sized in accordance with IEEE Std. 485-1997 to carry the expected
 
shutdown loads following a plant trip and a loss of all alternating current power without battery
 
terminal voltage falling below its minimum required voltage. This ensures that adequate DC
 
power will be available for starting and loading the emergency diesel generators, emergency
 
power to run instrumentation and controls, and emergency lighting.
 
IEEE Std. 485-1997, recommends applying at least a 125 percent (1.25) aging factor when
 
sizing batteries for nuclear power plants, to ensure the battery can perform its design function
 
with a greater than or equal to 80 percent capacity rating throughout its 20-year life. When
 
using an aging factor less than 1.25, the result is a reduction in expected life of the batteries
 
based on the manufacturers expected life versus capacity curves. The licensees identified
 
above were not immediately aware that an increase in battery design loads or a decrease in
 
rated battery capacity would result in a reduced expected life of the batteries. Certain TS SR
 
testing frequencies, specifically those associated with performance and modified performance
 
discharge testing, are directly tied to the expected life of batteries. The once per 60-month performance discharge test (which is based on 25 percent of a 20-year expected life) and the
 
increased TS SR frequencies (i.e., 12 and 24 months), when batteries reach 85 percent of
 
expected life, are consistent with the guidance provided in IEEE Std. 450 and are tied to known
 
age-related degradation of vented lead-acid batteries. The events described in this IN illustrate
 
the importance of considering the impact of a decrease in the battery expected life on plant TS


SRs.
IEEE Std. 485-1997, recommends applying at least a 125 percent (1.25) aging factor when sizing batteries for nuclear power plants, to ensure the battery can perform its design function with a greater than or equal to 80 percent capacity rating throughout its 20-year life. When using an aging factor less than 1.25, the result is a reduction in expected life of the batteries based on the manufacturers expected life versus capacity curves. The licensees identified above were not immediately aware that an increase in battery design loads or a decrease in rated battery capacity would result in a reduced expected life of the batteries. Certain TS SR testing frequencies, specifically those associated with performance and modified performance discharge testing, are directly tied to the expected life of batteries. The once per 60-month performance discharge test (which is based on 25 percent of a 20-year expected life) and the increased TS SR frequencies (i.e., 12 and 24 months), when batteries reach 85 percent of expected life, are consistent with the guidance provided in IEEE Std. 450 and are tied to known age-related degradation of vented lead-acid batteries. The events described in this IN illustrate the importance of considering the impact of a decrease in the battery expected life on plant TS SRs.


==CONTACT==
==CONTACT==

Latest revision as of 09:39, 10 November 2023

Battery Expected Life and Its Potential Impact on Surveillance Requirements
ML122130601
Person / Time
Issue date: 03/19/2013
From: Laura Dudes, Kokajko L
Division of Construction Inspection and Operational Programs, Division of Policy and Rulemaking
To:
Russell A
References
TAC MF0492 IN-13-005
Download: ML122130601 (5)
v • d • e


UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

OFFICE OF NEW REACTORS

WASHINGTON, DC 20555-0001 March 19, 2013 NRC INFORMATION NOTICE 2013-05: BATTERY EXPECTED LIFE AND ITS POTENTIAL

IMPACT ON SURVEILLANCE REQUIREMENTS

ADDRESSEES

All holders of an operating license or construction permit for a nuclear power reactor under Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and Utilization Facilities, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel.

All holders or applicants for a combined license under 10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants.

PURPOSE

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform addressees about recent issues involving licensees nonconservative technical specifications (TSs) regarding surveillance requirements (SRs) for direct current (DC) power systems due to reductions in battery expected life. The NRC expects that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems.

Suggestions contained in this IN are not NRC requirements; therefore, no specific action or written response is required.

BACKGROUND

Class 1E batteries are used to supply DC loads at nuclear power plants and are designed consistent with the requirements in General Design Criterion (GDC) 17, Electric Power Systems, and GDC 18, Inspection and Testing of Electric Power Systems, of Appendix A, General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50 or similar plant-specific design criteria.

The Class 1E batteries are lead-acid batteries which degrade over time, primarily as a result of the buildup of lead sulfates on the plates. The battery manufacturers typical expected battery life curve indicates a 100 percent battery capacity over the initial 14 years of service. The capacity then decreases to 80 percent at the end of the expected 20-year life. At this point, the Institute of Electrical and Electronics Engineers (IEEE) Standard (Std.) 450-2002, IEEE

Recommended Practice for Maintenance, Testing, and Replacement of Vented Lead-Acid Batteries for Stationary Applications, as endorsed by Regulatory Guide 1.129, Maintenance, Testing, and Replacement of Vented Lead-Acid Storage Batteries for Nuclear Power Plants, recommends replacing the battery bank. To account for this degradation, IEEE Std. 485-1997, IEEE Recommended Practice for Sizing Lead-Acid Batteries for Stationary Applications, as endorsed by Regulatory Guide 1.212, Sizing of Large Lead-Acid Storage Batteries, recommends that when sizing batteries for use at nuclear power plants, the rated capacity of the battery, when put in service, should be at least 125 percent of the design load. This ensures that at least 80 percent of the battery nameplate capacity will be available at the end of the 20-year expected life of the batteries, which will be sufficient to serve 100 percent of the design load (80 percent of 125 percent equals 100 percent).

The NRC requires licensees to maintain batteries in an operable condition as specified in plant TS. As such, the batteries must be capable of performing their intended function of supplying 100 percent of design DC loads. Standard TSs have a SR to Verify battery capacity is 80% of the manufacturer's rating when subjected to a performance discharge test or a modified performance discharge test. The specified frequency of this surveillance is 60 months AND 12 months when battery shows degradation, or has reached 85% of the expected life with capacity < 100% of manufacturers rating AND 24 months when battery has reached 85% of the expected life with capacity 100% of manufacturers rating. Note that the surveillance frequency uses the term expected life but does not include a specific value (e.g., 20 years).

Because of this, licensees may not be immediately aware of the impact changes to the expected life of their Class 1E batteries can have on their plants TS SRs.

DESCRIPTION OF CIRCUMSTANCES

In the examples below, the licensees discovered conditions that either increased battery design loads or decreased rated battery capacity such that the battery no longer met the sizing design basis. The batteries remained operable, at least in the near term, as the batteries were still capable of supplying 100 percent of the design DC loads. However, the licensees did not recognize the need to ensure the expected life of Class 1E batteries appropriately accounted for the sizing requirements and post-accident DC loading assumptions contained in design basis documents. As a result, certain TS SR testing frequencies, specifically those associated with performance or modified performance discharge testing, were non-conservative.

Cooper Nuclear Station

On March 11, 2009, the licensee for Cooper Nuclear Station submitted a license amendment request to address non-conservative TSs regarding the SRs for 125 volt (V) and 250 V DC power systems. During its review of the amendment, the NRC staff noted that a reduction in the expected service life would be needed to ensure the batteries would be capable of providing 90 percent of their rated capacity at the end of their service life. The NRC issued a request for additional information that requested the licensee to describe the impact of this change on the expected life of Cooper Nuclear Station batteries (e.g., conclusions drawn from the battery life versus capacity curve for the batteries).

In its response to the NRC staffs request for additional information, the licensee noted that as loads have increased over time, the required battery capacity is now closer to 90 percent of the nameplate rating. The licensee further stated that its battery vendor does not estimate battery life for 90 percent capacity. Therefore, the licensee conservatively established 15 years as the point at which the batteries reach 85 percent of expected life. The licensee also conservatively defined battery degradation to be when capacity drops by more than 5 percent (normally 10 percent as defined by the IEEE Std. 450-2002,) relative to the capacity on the previous performance test or when the battery capacity reaches less than or equal to 95 percent of the manufacturers rating (normally 90 percent or when it is 10 percent below the manufacturers rating as defined by IEEE Std. 450-2002). On March 18, 2010, the NRC issued the above mentioned license amendment for Cooper Nuclear Station. To address the above concern, the NRC staff required the licensee to update its updated safety analysis report and TS bases for the batteries upon implementation of the approved license amendment. These updates included the reduction to 15 years as the point at which the safety-related batteries have reached 85 percent of expected life. See the licensee amendment issuance package for further details (Agencywide Documents Access and Management System (ADAMS) Accession No. ML100610233).

Indian Point Nuclear Generating, Unit 2 (IP2)

On March 29, 2009, the licensee for IP2 submitted a license amendment request to address non-conservative TSs regarding SR 3.8.6.6 in TS section 3.8.6, Battery Parameters, for 125 V DC power systems. The SR verifies battery capacity during a performance discharge test or a modified performance discharge test. The licensee discovered that the 80 percent capacity value was non-conservative with respect to the existing design basis calculation for battery capacity under minimum design temperature conditions. The licensee determined that it should implement a more restrictive battery acceptance criterion ( 85 percent of manufacturers rating) to ensure that sufficient battery capacity exists at limiting conditions. During its review of the amendment, the NRC staff identified that the licensee for IP2 applied a 117.6 percent (1.176) aging factor in its design calculation for sizing the Class 1E batteries. While the aging factor is less than that recommended by IEEE Std. 485-1997, the licensee followed this guidance since the aging factor is appropriate for the assumed end-of-life criterion (i.e., 85 percent). However, based on standard battery life versus capacity curves, the licensee noted that aging these batteries to 85 percent of rated capacity would indicate an expected battery life of approximately 18 years versus 20 years originally assumed.

On February 24, 2010, the NRC issued the above mentioned license amendment for IP2. To address the above concern, the NRC staff required the licensee to update its battery monitoring and maintenance program, TS bases for the batteries, and updated final safety analysis report upon implementation of the approved license amendment. These updates included the reduction to 18 years as the expected life of their safety-related batteries. See the licensee amendment issuance package for further details (ADAMS Accession No. ML100270051).

DISCUSSION

Licensees rely on Class 1E batteries to supply DC loads when battery chargers are not available. The batteries are sized in accordance with IEEE Std. 485-1997 to carry the expected shutdown loads following a plant trip and a loss of all alternating current power without battery terminal voltage falling below its minimum required voltage. This ensures that adequate DC power will be available for starting and loading the emergency diesel generators, emergency power to run instrumentation and controls, and emergency lighting.

IEEE Std. 485-1997, recommends applying at least a 125 percent (1.25) aging factor when sizing batteries for nuclear power plants, to ensure the battery can perform its design function with a greater than or equal to 80 percent capacity rating throughout its 20-year life. When using an aging factor less than 1.25, the result is a reduction in expected life of the batteries based on the manufacturers expected life versus capacity curves. The licensees identified above were not immediately aware that an increase in battery design loads or a decrease in rated battery capacity would result in a reduced expected life of the batteries. Certain TS SR testing frequencies, specifically those associated with performance and modified performance discharge testing, are directly tied to the expected life of batteries. The once per 60-month performance discharge test (which is based on 25 percent of a 20-year expected life) and the increased TS SR frequencies (i.e., 12 and 24 months), when batteries reach 85 percent of expected life, are consistent with the guidance provided in IEEE Std. 450 and are tied to known age-related degradation of vented lead-acid batteries. The events described in this IN illustrate the importance of considering the impact of a decrease in the battery expected life on plant TS SRs.

CONTACT

This IN requires no specific action or written response. Please direct any questions about this

matter to the technical contacts listed below or the appropriate NRC project manager.

/RA/ /RA/

Lawrence E. Kokajko, Director Laura A. Dudes, Director

Division of Policy and Rulemaking Division of Construction Inspection

Office of Nuclear Reactor Regulation and Operational Programs

Office of New Reactors

Technical Contacts: Matthew McConnell, NRR

301-415-1597 E-mail: Matthew.McConnell@nrc.gov

Sergiu Basturescu, NRR

301-415-1237 E-mail: Sergiu.Basturescu@nrc.gov

Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under NRC Library.

ML122130601 *via e-mail TAC MF0492 OFFICE NRR/DE/EEEB* Tech Editor* NRR/DE/EEEB/BC NRR/DE/D NRR/DPR/PGCB/PM

NAME MMcConnell CHsu JAndersen PHiland ARussell

(RMathew for)

DATE 02/13/13 01/18/13 02/14/13 02/14/13 02/19/13 OFFICE NRR/DPR/PGCB/LA NRR/DPR/PGCB/BC NRO/DCIP/D NRR/DPR/DD NRR/DPR/D

NAME CHawes, (GLappert DPelton LDudes SBahadur LKokajko

for)

DATE 02/19/13 03/04/13 03/14/13 03/18/13 03/19/13


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