ML13345A609

Response to Request for Additional Information Regarding License Amendment Request Pursuant to 10 CFR 50.90: Standby Liquid Control System - Increase in Isotopic Enrichment of Boron-10

ML13345A609
Person / Time
Site:	Nine Mile Point
Issue date:	12/06/2013
From:	Costanzo C Constellation Energy Group, EDF Group, Nine Mile Point
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML13345A609 (7)

Text

Christopher R. Costanzo Office: 315.349.5200 Vice President - Nine Mile Point Fax: 315.349.1321 E-mail: Christopher.Costanzo@cengllc.com CENG.

a joint venture of 0Energy nst"eaIýi 66-'eDF NINE MILE POINT NUCLEAR STATION December 6, 2013 U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION: Document Control Desk

SUBJECT:

Nine Mile Point Nuclear Station Unit No. 2" Docket No. 50-410 Response to Request for Additional Information Regarding License Amendment Request Pursuant to 10 CFR 50.90: Standby Liquid Control System - Increase in Isotopic Enrichment of Boron- 10

REFERENCES:

(a) Letter from P. M. Swift (NMPNS) to Document Control Desk (USNRC), License Amendment Request Pursuant to 10 CFR 50.90: Standby Liquid Control System

- Increase in Isotopic Enrichment of Boron- 10, dated July 5, 2013 (ML13197A221)

On July 5, 2013 (Reference a), Nine Mile Point Nuclear Station, LLC (NMPNS) submitted a request for an amendment to Nine Mile Point Unit 2 (NMP2) Renewed Operating License (OL) NPF-69 to increase the isotopic enrichment of boron-10 in the sodium pentaborate solution used to prepare the neutron absorber solution in the Standby Liquid Control System (SLS). On November 6, 2013, the U.S. Nuclear Regulatory Commission (NRC) issued a Request for Additional Information (RAI) via email regarding the NMP2 license amendment request. A subsequent teleconference with the NRC reviewer and staff on November 14, 2013 provided clarification of the questions and the agreed to scope of response. provides the NMPNS response to the 4 questions in the NRC RAI.

This supplemental information does not affect the No Significant Hazards Determination analysis provided by NMPNS in Reference (a). Pursuant to 10 CFR 50.91(b)(1), NMPNS has provided a copy of this supplemental information to the appropriate state representative. This letter contains no new regulatory commitments.

Document Control Desk December 6, 2013 Page 2 Should you have any questions regarding the information in this submittal, please contact Everett (Chip).

Perkins, Director - Licensing, at (315) 349-5219.

I declare under penalty of perjury that the foregoing is true and correct. Executed on December 6, 2013.

Very truly yours, CRC/KJK/STD

Attachment:

Response to Request for Additional Information cc: Regional Administrator, Region I, NRC Resident Inspector, NRC Project Manager, NRC A. L. Peterson NYSERDA

ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION Nine Mile Point Nuclear Station, LLC December 6, 2013

ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION Each individual NRC question is repeated (in italics), followed by the NMPNS response.

NRC RAI #1 The application describes the changes to the volumes, concentrations and enrichments but does not describe physical plant changes to the SLC [Standby Liquid Control] System. Is the system being physically changed? Describe the svstem (storage tank size, pumps location and its actuationmechanism during A TWS), provide a schematic of the systems, and describe the functionality of the proposed SLC System for NMP2 [Nine Mile Point Unit 2] including the operator actions necessary during an A TWS

[Anticipated Transient Without Scram].

NMPNS Response The proposed license amendment only affects the isotopic enrichment of boron-10 in the sodium pentaborate solution used to prepare the neutron absorber solution in the SLC. The proposed license amendment request does not require any physical modifications to the SLC system including its function and operation. As discussed in a teleconference with the NRC on November 14, 2013, the NRC staff noted that it is acceptable to refer to specific sections of the NMP2 Updated Safety Analysis Report (USAR), rather than include a description and schematic of the system. The SLC System is described in Section 9.3.5, Standby Liquid Control System, of the NMP2 USAR. The SLC System Piping and Instrument Diagram is shown in NMP2 USAR Figure 9.3-17a, Standby Liquid Control.

The SLC system initiates upon receiving High Dome Pressure signal or Reactor Low Vessel Level 2 with Average Power Range Monitor (APRM) confirmation (power > 4%) with 98 seconds nominal time delay.

The SLC system initiation logic is shown in NMP2 USAR Figure 7.6-9, Redundant Reactivity Control System.

The only difference is that the negative reactivity insertion rate is about 4 times higher. Therefore, the injection time is shorter with the changes defined in the proposed license amendment request.

The SLC system initiates automatically during an ATWS event and manual operator actions are not required.

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ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION NRC RAI #2 Please provide a design rationalefor the assumptions regarding SLC System Petformances listed in Table I of the July 5. 2013 submittal. Specifically explain why the range of values was chosen for minimum boron-JO enrichmentfor A TWS analysis and SLC System pump flow rate to support.

a. The application states the required minimum volumes for the 13.6 wt% [weight percent] and 14.4 wt% solution volumes were derived by determining the minimum solution volume and then increasingthe volume to accountfor: 1) the dead volume not pumped in the reactorthat remains in the SLC System and HPCS [High Pressure Core Spray] piping, and 2) instrument accuracy.

Please explain how these volumes were derived. Please include the methodologies and the basis for the criteria used.

NMPNS Response The 92% minimum boron- 0 enrichment is primarily based on injection of sufficient negative reactivity as soon as practical to offset the impact of a future modification, while maintaining the suppression pool heatup approximately same.

GEH issued a Safety Communication (SC) 10-13, Standby Liquid Control System Dilution Flow, alerting utilities that there is a potential that the solution injected into the vessel may be diluted due to a small flow through an orifice from the makeup water system. The maximum expected dilution flow is less than 1 gpm. Therefore, the suction flow from the SLC storage tank could be 81.4 gallons per minute (gpm)

(82.4 gpm total pump flow - I gpm dilution flow). NMP2 conservatively used an 80 gpm suction flow rate from the SLC storage tank.

The minimum tank volume requirements were calculated as follows:

• First, the solution volume necessary to bring reactor coolant boron concentration to 780 parts per million (ppm) of natural boron plus 25% margin is calculated. For a 13.6 wt% sodium pentaborate solution concentration, the required solution volume is 1,178 gallons. For 14.4 wt%

solution concentration, the required volume is 1,108 gallons.

• Following an injection, some of the solution will remain in the piping between the tank and the injection points (HPCS injection spargers) once the SLC pump trips on low level. This volume (239.4 gallons) is added to the above volume.

• The SLC pumps automatically trip when the sensed tank level is "zero", 10.23 inches above the tank bottom. The overall instrumentation loop uncertainty in the level measurement is 3.6 inches (same as prior to the proposed license amendment request), which equates to 143 gallons.

Conservatively, the SLC pumps are assumed to trip 3.6 inches above the "zero" level.

• The minimum required tank volume (above tank "zero" level) calculated above is further adjusted for solution temperature variation with added margin (approximately 40 gallons). The minimum required inventory above the tank "zero" level is 1,600 gallons. NMP2 administratively maintains the tank solution between 1,800 and 2,000 gallons above the tank "zero" level.

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ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION NRC RAI #3 With respect to maintainingsuppressionpool pH >7.0, please provide the methodologies used to generate the minimum sodium pentaborate solution volume requiredfor injection post-LOCA [Loss of Coolant Accident]for adequatepH control at the limiting concentrationas given in the submittal as 1, 065 gallon for a sodium pentaborate concentration of 13.6%. Also provide an explanation regarding how the mnaximum time available to add boron is determined.

NMPNS Response The suppression pool pH calculation utilizes the methodology described in NUREG/CR-5950, Iodine Evolution and pH Control. This methodology was used earlier by NMP2 in support of Alternate Source Term License Amendment Request approved by the NRC on May 29, 2008 (ML081230439, ML081560633).

The maximum time available to add boron is based on a SLC storage tank operating heater failure scenario. The operating heater is assumed to fail in the ON position (heater continues to heat the liquid) and no operator action is taken following the LOCA event to turn-off the heater. Under this conservative scenario, the solution temperature increases. At approximately 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> into the LOCA event, the solution temperature would be at the point such that the Net Positive Suction Head - Available (NPSHA) is reduced to Net Positive Suction Head - Required (NPSHR). Therefore, in the heater failure scenario, the SLC pump may not function after 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br />.

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ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION NRC RAI #4 With respect to Net Positive Suction Head Available (NPSH.,) for SLC System pumps, the proposed reduction in the minimum volume for SLC System storage tank results in a reduction in the static head available to provide NPSHA and the calculation that determines the SLC System pumnp NPSHA did not take any creditfor the static head above the SLC System storage tank zero level. Please describe any difference in the SLC System pump specifications between the current ones and the ones to be usedfor proposed change of the minimum SLC System storage tank andjustiy that the proposed NPSH4 for the SLC System pumps adequate.

NMPNS Response The proposed license amendment request does not require any modifications to the SLC pumps, piping, or tank. Therefore, there is no change to the SLC pump specification.

The SLC pump NPSH calculation uses tank "zero" level as its basis for calculating NPSHA, same as before the proposed change, which has been confirmed through the review of the calculation. In addition, the pump flow remains the same as before. Therefore, SLC pump NPSH margin is not affected by the license amendment request.

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