NLS2011060, Response to NRC Request for Additional Information Non-Conservative Battery Terminal Voltage and Specific Gravity in Technical Specification Surveillance Requirements
| ML11167A083 | |
| Person / Time | |
|---|---|
| Site: | Cooper  (DPR-046) |
| Issue date: | 06/10/2011 |
| From: | O'Grady B Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2011060 | |
| Download: ML11167A083 (6) | |
Text
H Nebraska Public Power District Always there when you need us 50.90 NLS2011060 June 10, 2011 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Response to Nuclear Regulatory Commission Request for Additional Information Re: Non-Conservative Battery Terminal Voltage and Specific Gravity in Technical Specification Surveillance Requirements Cooper Nuclear Station, Docket No. 50-298, DPR-46
References:
- 1.
Letter from Lynnea E. Wilkins, U. S. Nuclear Regulatory Commission, to Brian J. O'Grady, Nebraska Public Power District, dated May 13, 2011, "Cooper Nuclear Station - Request for Additional Information Re: Non-Conservative Battery Terminal Voltage and Specific Gravity in Technical Specification Surveillance Requirements (TAC No. ME4974)
- 2.
Letter from Brian J. O'Grady, Nebraska Public Power District, to the U.S.
Nuclear Regulatory Commission, dated October 29, 2010, "Non-Conservative Battery Terminal Voltage and Specific Gravity in Technical Specification Surveillance Requirements"
Dear Sir or Madam:
The purpose of this letter is for Nebraska Public Power District to submit a response to a request for additional information (RAI) from the Nuclear Regulatory Commission (NRC) (Reference 1). The RAI requested information is in support of the NRC's review of a license amendment request for the Cooper Nuclear Station (CNS) facility operating license and technical specifications (TS) to correct non-conservative values of minimum voltages in TS Surveillance Requirement 3.8.4.1 for the 125 volt and 250 volt batteries, and to correct non-conservative battery specific gravity values listed in CNS TS Table 3.8.6-1.
Responses to the specific RAI questions are provided in the Attachment. No regulatory commitments are made in this submittal.
The information submitted by this response to the RAI does not change the conclusions or the basis of the no significant hazards consideration evaluation provided with Reference 2.
COOPER NUCLEAR STATION0 P.O. Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-3811 / Fax: (402) 825-5211 www.nppd.com
NLS2011060 Page 2 of 2 If you have any questions concerning this matter, please contact David Van Der Kamp, Licensing Manager, at (402) 825-2904.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on 10 0* 1 /
(date)
Sincerely, Brian J. O'Grady Vice President - Nuclear and Chief Nuclear Officer
/em Attachment cc:
Regional Administrator w/ attachment USNRC - Region IV Cooper Project Manager w/ attachment USNRC - NRR Project Directorate IV-1 Senior Resident Inspector w/ attachment USNRC - CNS Nebraska Health and Human Services w/ attachment Department of Regulation and Licensure NPG Distribution w/o attachment CNS Records w/ attachment
NLS2011060 Attachment Page 1 of 3 Attachment Response to Nuclear Regulatory Commission Request for Additional Information Re: Non-Conservative Battery Terminal Voltage and Specific Gravity in Technical Specification Surveillance Requirements Cooper Nuclear Station, Docket No. 50-298, DPR-46 NRC Question 1:
In its LAR, the licensee proposed revising the battery terminal voltage acceptance criteria for the Division I and II safety-related batteries. However, the associated battery charger output voltage acceptance criteria in TS SR 3.8.4.6 were not proposed to be revised. Please provide justification for not proposing a revision to the corresponding TS SR 3.8.4.6for the battery charger.
NPPD Response:
The battery charger voltage acceptance rating does not require changing, because it is specified for a more limiting condition on the charger. As noted in Cooper Nuclear Station (CNS)
Technical Specification (TS) Bases 3.8.4, DC Sources - Operating, Background section, the battery charger must be able to fully recharge the batteries while carrying full load on the busses from a minimum charge rather than only maintaining float voltage. Surveillance Requirement 3.8.4.6 requires the battery charger to deliver at least rated amps (200) and rated volts (125 or 250 volt (V) direct current (DC)) for at least four hours in order to restore the battery from design minimum charge to fully charged.
This proposed license amendment appropriately only addresses the float voltage to maintain the battery in the fully charged state after that state has been reached. The float voltage setting is a different function of the battery charger than the ability to recharge a battery while supplying the connected loads concurrently.
NRC Question 2:
Please describe how the manufacturer quantified a capacity of 96 percent of rated from an average specific gravity of l.205.
NPPD Response:
Because there was insufficient empirical data to draw a correlation of battery rating to specific gravity, the manufacturer, C&D Charter Power System, Inc., provided an engineering estimate for the battery de-rating of 96% to quantify the performance reduction for a lead calcium type battery such as the LCR-25 D841 type used at CNS. This estimate was for a battery with a nominal specific gravity of 1.215 (1.215 + 0.005) that is fully charged, but, due to causes other
NLS2011060 Attachment Page 2 of 3 than the battery charger being out of service, has a specific gravity of 1.205. The following table was provided.
Fully Charged Rated Performance Specific Gravity 8 Hour 4 Hour 1 Hour 1 Minute 1.215 100%
100%
100%
100%
1.205 96%
96%
97%
97%
1.195 93%
93%
94%
95%
1.175 82%
82%
83%
85%
NRC Question 3:
Please provide the technical justification for the proposed Category B specific gravity limit of 1.200.
NPPD Response:
The Category B minimum specific gravity limit for each connected cell ensures that a cell with a marginal or unacceptable specific gravity is not masked by averaging with cells having higher specific gravities. The value of 1.200 was chosen to correct the non-conservative TS values identified from load study calculations as being conservatively higher than the value recommended by the Institute of Electrical and Electronic Engineers (IEEE) Working Group on Batteries. The IEEE recommended value for each connected cell should be no more than 20 points (0.020) below the full charge specific gravity (1.210 - 0.020 =1.190).
NRC Question 4:
Please state if CNS is using a nuclear qualified version of electrical power systems design, simulation, and analytic software.
NPPD Response:
Yes, CNS is using a nuclear qualified version of electrical power systems design, simulation, and analytic (EDSA) software; currently, EDSA Technical 2000, Service Pack 3.5.
NRC Question 5:
Please provide a summary of the analysis that shows how CNS found that the DC systems were capable of meeting requirements for safe shutdown and for maintaining the plant in a safe shutdown mode as well as meeting the requirements for station blackout and Appendix R of Title 10 of the Code of Federal Regulations (10 CFR) Part 50.
NLS2011060 Attachment Page 3 of 3 NPPD Response:
CNS maintains four calculations for the 125 VDC and 250 VDC systems. Each voltage system has a separate calculation for the components and battery per electrical division. The four calculations evaluate, by analysis, the adequacy of voltage to the components supplied by the battery to perform their required function for all design basis events. The calculations determine the DC equipment start, stop, and run times for the following events:
- 1. Loss of coolant accident (LOCA) event with concurrent loss of battery charge for time t = 0 seconds and ending at time t = 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
- 2. Station blackout (SBO) occurring at time t = 0 seconds and ending at time t = 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
- 3.
Appendix R fire scenario with loss of off-site power (LOOP) occurring at t = 0 seconds and ending at t = 4.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> (Division II batteries only).
Additionally, the calculations determine the load on each of the main busses for the respective system, the terminal voltages of the devices and verification of adequate voltage to perform their safety function for the scenarios, and verify adequate voltage exists at the DC starter busses for the motor-operated valves (MOV) in the CNS MOV Program Plan.
The calculations include a worst case ground fault added to the switchgear bus, cable conductor resistance conservatively corrected to 75 degrees Celsius, battery connection impedance, battery curves for the C&D battery type LCR-25, battery aging coefficient, number of cells, battery temperature, and a design margin factor. The battery de-rating of 96% is included in the design margin factor.
The four calculations conclude that all safety-related 125 and 250 VDC components powered from the 125 and 250 VDC batteries at CNS will have adequate voltage and current to perform their safety function for the LOOP/LOCA, SBO, and Appendix R with LOOP (Division II only) scenarios.
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTSC 4 ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS@'
Correspondence Number:
NLS2011060 The following table identifies those actions committed to by Nebraska Public Power District (NPPD) in this document. Any other actions discussed in the submittal represent intended or planned actions by NPPD. They are described for information only and are not regulatory commitments. Please notify the Licensing Manager at Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.
COMMITMENT COMMITTED DATE COMMITMENT NUMBER OR OUTAGE None I PROCEDURE 0.42 REVISION 27 PAGE 18 OF 25 ý