CNS-15-068, Response to NRC Request for Additional Information Regarding License Amendment Request for Changes to Technical Specification 3.3.2, Engineered Safety Feature Actuation System Instrumentation and .
| ML15217A008 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 07/31/2015 |
| From: | Henderson K Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| CNS-15-068 | |
| Download: ML15217A008 (8) | |
Text
ENERGY Kelvin Henderson Vice President Catawba Nuclear Station Duke Energy CNOIVP 4800 Concord Road York, SC 29745 CNS-1 5-06 8 July 31, 2015 0:803.701.4251 f: 803.701.3221 10 CFR 50.90 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001
Subject:
Duke Energy Carolinas, LLC (Duke Energy)
Catawba Nuclear Station, Units 1 and 2 Docket Numbers 50-413 and 50-414 License Amendment Request (LAR) for Changes to Technical Specification (TS) 3.3.2, "Engineered Safety Feature Actuation System (ESFAS) Instrumentation" and TS 3.3.5, "Loss of Power (LOP) Diesel Generator (DG) Start Instrumentation" Resolution of Operable But Degraded Condition Due to Non-Conservative TS Response to NRC Reques~t for Additional Information
References:
- 1. Letter from Duke Energy to NRC, dated November 24, 2014 (ADAMS Accession Number ML14330A327)
- 2. Letter from NRC to Duke Energy, dated May 18, 2015 (ADAMS Accession Number ML15132A773)
Reference 1 requested NRC review and approval to revise the Allowable Value parameter for the TS 3.3.2 Table 3.3.2-1, "Engineered Safety Feature Actuation System Instrumentation" function for Auxiliary Feedwater Loss of Offsite Power (Function 6.d.) and for the TS 3.3.5 Loss of Voltage function in Surveillance Requirement (SR) 3.3.5.2 in order to make this parameter more restrictive. The existing parameter was determined to be non-conservative and this parameter is presently classified as Operable But Degraded in the Catawba Corrective Action Program. In addition, the Nominal Trip Setpoint parameter for this function is being slightly lowered in order to gain additional margin to what is known as a "double sequencing event".
Finally, as part of this LAR, applicable footnotes are also being added to the affected TS 3.3.2 function in accordance with TS Task Force Traveler TSTF-493, Revision 4, "Clarify Application of Setpoint Methodology for LSSS Functions".
Reference 2 transmitted NRC Requests for Additional Information (RAIs) associated with Reference 1.
The purpose of this letter is to formally respond to the Reference 2 RAls. The enclosure to this letter provides Duke Energy's response. The format of the enclosure is to restate each RAI question, followed by its associated response.
www.duke-energy.com
U.S. Nuclear Regulatory Commission Page 2 July 31, 2015 The conclusions of the original Regulatory Evaluation and Environmental Consideration contained in Reference 1 are unaffected as a result of this RAI response.
Pursuant to 10 CER 50.91, a copy of this LAR supplement has been forwarded to the appropriate State of South Carolina official.
There are no regulatory commitments contained in this letter or its enclosure.
If you have any questions or need additional information on this matter, please contact L.J.
Rudy at (803) 701-3084.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on July 31, 2015.
Very truly yours Kelvin Henderson Vice President, Catawba Nuclear Station LJR/s Enclosure
U.S. Nuclear Regulatory Commission Page 3 July 31, 2015 xc (with enclosure):
V.M. McCree Regional Administrator U.S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, GA 30303-1 257 G.A. Hutto Ill Senior Resident Inspector U.S. Nuclear Regulatory Commission Catawba Nuclear Station G.E. Miller (addressee only)
NRC Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 8 G9A 11555 Rockville Pike Rockville, MD 20852-2738 S.E. Jenkins Manager Radioactive & Infectious Waste Management Division of Waste Management South Carolina Department of Health and Environmental Control 2600 Bull St.
Columbia, SC 29201
Enclosure RESPONSE TO NRC REQUESTS FOR ADDITIONAL INFORMATION (RAIs)
Subject:
License Amendment Request (LAR) for Changes to Technical Specification (TS) 3.3.2, "Engineered Safety Feature Actuation System (ESFAS) Instrumentation" and TS 3.3.5, "Loss of Power (LOP) Diesel Generator (DG) Start Instrumentation" Resolution of Operable But Degraded Condition Due to Non-Conservative TS Page 1 of 5
Enclosure REQUEST FOR ADDITIONAL INFORMATION REGARDING CATAWBA NUCLEAR STATION. UNITS 1 AND 2 LICENSE AMENDMENT REQUEST TS 3.3.2. "ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION" TS 3.3.5. "LOSS OF POWER DIESEL GENERATOR STARTUP INSTRUMENTATION" DOCKET NOS. 50-413 AND 50-414 By letter dated November 24, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML14330A327), Duke Energy Carolinas (Duke) submitted a license amendment request for the Catawba Nuclear Station, Units 1 and 2. The proposed amendment would revise the allowable value in the subject TSs to correct a non-conservative value. In order for the NRC staff to complete its review of the relief request, the following additional information is requested.
- 1. RG 1.105 includes the NRC staff concern that the uncertainties assumed for instrumentation, including primary elements, were subsequently not verified or controlled through surveillance testing, qualification, or maintenance programs. Also, RG 1.105 states the NRC staff is concerned limited instrumentation drift data. In calculation CNC-1381.05-00-001 7, provided as an Attachment to the letter dated January 15, 2015, (ADAMS Accession No. ML15020A018), the licensee identifies the maximum value from the last 11 monthly calibrations has been used as the relay drift (RD) value in the channel uncertainty and ultimately the application of that to the Nominal Trip Setpoint.
Please provide a discussion on the following with regards to the RD uncertainty factor:
- a.
Has a statistical analysis been done on the existing data to determine if a normal distribution, standard deviation and confidence level exists?
Duke Energy Response:
No statistical analysis was done, nor was one necessary. As indicated to the NRC in a May 7, 2015 telephone conference call discussing the draft RAIs, the drift values used are considered typical for these relays and are consistent with the information provided in the instruction book for the relays.
- b.
Is this data consistent with the data and value provided by the manufacturer?
Duke Energy Response:
Yes. The instruction book for the relay does not give an actual number, but states that the relay has "excellent repeatability". Engineering considers the values determined from our calibration results to fall in that category.
- c.
The NRC staff requires additional information regarding how the licensee will assess the latest as-found and as-left acceptance data when performing surveillance test activities and will update the uncertainties accordingly. For Page 2 of 5
Enclosure example, the maximum drift value from the previous (2012) revision of the calculation is the same as the value that is used in the current calculation. Is this because the maximum value was not exceeded or additional data was not needed to be considered?
Duke Energy Response:
The drift values used in the uncertainty calculation are considered typical for these relays. In support of this response, calibration results for the last six months of 2014 were reviewed. The maximum assumed drift value was never exceeded; in fact, it was never approached. The maximum drift observed was 0.2 volts, while the worst case drift assumed in the uncertainty calculation was 0.7 volts. This confirms that the values used in the uncertainty calculation are bounding.
- 2.
Section 3.0, of the license amendment request (LAR) states the revised relay settings calculation (Revision 17) includes new information provided in the latest vendor documentation for the relays. However, the referenced vendor documentation for that relay is the Instruction Bulletin, Issue E, which is dated July, 1988. Please provide the source and extent of the new vendor information for this relay that affected the changes to the uncertainty.
Duke Energy Response:
See the information below for Question 3.
- 3.
Section 3.0 states that, in Revision 16 of the calculation CNC 1381.05 0017, the corresponding tolerance for the factory calibration dial markings in the relay instruction bulletin should not have been used and was the major contributor to reducing the uncertainty for the loss of voltage relays. However, Revision 16, page 1 8a of the channel uncertainty calculation does not show an uncertainty factor for the factory calibration dial markings or any other factors other than those which will be used for the post-LAR channel uncertainty calculation. Clarify where the previous calculation is presented, which factors were removed from the calculation and provide a discussion on how the relay manufacturer was consulted on the issue.
Duke Energy Response:
Revision 16 of CNC-1381.05-00-0017 (as opposed to Revision 17) actually incorporated the new information from the vendor documentation. Revision 16 did not include the tolerances associated with the factory calibration dial markings. Revision 17 (which was developed in support of this LAR), which lowers the loss of voltage setpoint, follows Revision 16 and accordingly does not include the tolerances associated with the calibration dial markings, as they were removed in the previous revision to the calculation. As part of the preparation for Revision 16, the relay manufacturer was contacted pertaining to the required variables to be considered in the uncertainty calculation. The variables used in Revision 16 and Revision 17 are consistent with those recommended by the relay manufacturer.
- 4.
Please confirm the following for the undervoltage relay setting:
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Enclosure
- a.
The lower analytical voltage limit for the undervoltage relay is such that none of the safety-related, normally running motors would stall when subjected to this voltage.
Duke Energy Response:
The Electrical Analysis Group in the Corporate Office, using the Electrical Transient Analyzer Program (ETAP) PowerStation software, determined the current which would be pulled by each of the safety related motors. The current draw for each of the motors was compared to the protective relaying, overload heaters, and breaker ratings, and it was verified that the current drawn would not exceed these values. Therefore, the motors would continue to run.
- b.
The upper analytical limit for the undervoltage relay is such that the minimum expected voltage during loss-of-coolant accident (LOCA) start of. all safety related loads remains above this voltage.
Duke Energy Response:
Yes. The upper limit for the LOV relay will be 3504 V. Per the supporting calculations performed by the Electrical Analysis Group, the lowest bus voltage during a LOCA is 3563 V for Unit 1 and 3557 V for Unit 2. Therefore, the lower of the two (3557 V) leaves a margin of 53 V.
- 5.
The proposed time delay setting of the undervoltage relay is 10 cycles. With respect to how this value Will avoid unnecessary separation of safety-related buses from offsite power. Please provide the following:
- a.
A discussion of the voltage dip following a fault, lightning strike, or switching transient in the grid and whether it will cause spurious separation of safety buses from offsite power. Provide the maximum fault clearing time in the transmission system.
Duke Energy Response:
Per the Transmission organization, there is not a "maximum fault clearing time" in the transmission system. If there were a fault that caused a voltage drop this low that lasted for 8.5 seconds, it would not be a spurious separation from the grid.
The system would have already passed the normal clearing times used in the grid stability studies and would be heading for (or already be in) a cascading event.
Note that UFSAR section 8.3.1.1.2.1 (7th paragraph) states: "The 10 cycle time delay prevents false diesel starting due to power system transients." This 10 cycle time delay is not being added per this LAR. It has been in effect for many years. Actuation of the loss of voltage relays starts the diesel generator via the load sequencer. After 8.5 seconds, if the load sequencer still detects a loss of voltage, then the safety related buses are separated from offsite power. So in effect there is at least an 8.5 second delay prior to separating from offsite power.
Page 4 of 5
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Enclosure
- b.
A discussion that momentary voltage dip lasting to clear a fault in the distribution system downstream of safety-related buses will not cause separation of safety-related buses from offsite power.
Duke Energy Response:
As stated above, the load sequencer rechecks for a loss of voltage after 8.5 seconds. If the voltage is still low, then the safety related buses will separate from offsite power. A momentary voltage dip does not cause separation from offsite power. Therefore, a downstream fault would only clear that portion of the system.
Qffsite power would not be affected.
- 6.
Please provide a curve showing the minimum voltages at the 4160 V safety-related buses during the starting of LOCA loads after the safety injection signal based on the minimum switchyard voltage (based on agreement with the transmission system.
operator). Super-impose on this curve, the analytical and reset voltage values of the undervoltage relay settings to demonstrate that adequate margin exists so that the motors would not trip out by the undervoltage relay during a LOCA load sequencing.
Duke Energy Response:
Duke Energy will provide a response to this question by August 17, 2015.
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