ML13318A011

Comanche Peak - Response to Request for Additional Information Regarding Closure Options for Generic Safety Issue 191

ML13318A011
Person / Time
Site:	Comanche Peak
Issue date:	10/31/2013
From:	Flores R, McCool T P Luminant Generation Co, Luminant Power
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CP-201301214, GL 2004-02, GSI-191, TAC MC4676, TAC MC4677, TXX-13149
Download: ML13318A011 (4)

Text

Rafael Flores Senior Vice President& Chief Nuclear Officer rafael.flores@Luminant.com Luminant Power P 0 Box 1002 6322 North FM 56 Glen Rose, TX 76043 Luminant T 254 897 5590 C 817 559 0403 F 254 897 6652 REF: GL 2004-02 CP-201301214 TXX-13149 October 31, 2013 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT (CPNPP)DOCKET NOS. 50-445 AND 50-446 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING CLOSURE OPTIONS FOR GENERIC SAFETY ISSUE 191 (TAC NOS. MC4676 AND MC4677)

REFERENCE:

1.Letter logged TXX-13091, dated May 16, 2013, from Rafael Flores of Luminant Power to Balwant Singal of the NRC, RE: Closure OPTIONS FOR GENERIC SAFETY ISSUE 191 (GSI-191), ASSESSMENT OF DEBRIS ACCUMULATION ON PRESSURIZED WATER REACTOR SUMP PERFORMANCE, (ML 13149A101)

2. Letter dated September 30, 2013, from Balwant Singal of the NRC to Rafael Flores of Luminant Power, RE: Comanche Peak Nuclear Power Plant, Units I and 2 -Request for Additional Information Regarding Closure Options for Generic Safety Issue 191, ASSESSMENT OF DEBRIS ACCUMULATION ON PRESSURIZED-WATER REACTOR SUMP PERFORMANCE (ML 13267A197)

Dear Sir or Madam:

In Reference 1, Luminant Generation Company LLC (Luminant Power) provided the U.S. Nuclear Regulatory Commission (NRC) staff with the intended path forward for the resolution of Generic Safety Issue (GSI)-191, "Assessment of Debris Accumulation on Pressurized-Water Reactor Sump Performance," for Comanche Peak Nuclear Power Plant, Units 1 and 2 (CPNPP). Luminant Power identified that CPNPP will follow Option 2a (defined as deterministic approach with additional modeling refinements in SECY-12-0093).

A member of the STARS Alliance Callaway

• Comanche Peak

• Diablo Canyon -Palo Verde

• South Texas Project

• Wolf Creek AdD U. S. Nuctear Regulatory Commission TXX-13149 Page 2 of 2 10/31/2013 In Reference 2, the NRC staff requested the following additional information to complete the review of Luminant Power's path forward for the resolution of GSI-191 for CPNPP: 1. Please provide the Westinghouse recommended mitigative measures deemed necessary for CPNPP, and if not yet implemented, the schedule for implementing the Westinghouse recommendations.

2. Please provide the details of actions performed by EOPs FRC-0-1A, FRC-0.1B, FRC-0.2A, and FRC-0.2B to deal with inadequate core cooling.The attachment to this letter provides the requested information.

This communication contains no new commitments regarding CPNPP Units 1 and 2.Should you have any questions, please contact Mr. J. D. Seawright at (254) 897-0140.I state under penalty of perjury that the foregoing is true and correct.Executed on October 31, 2013.Sincerely, Luminant Generation Company LLC Rafael Flores By: Thomas P. McCool Vice President, Station Support Attachment c -Marc L. Dapas, Region IV Balwant K. Singal, NRR Resident Inspectors, Comanche Peak Attachment to TXX-13149 Page 1 of 2 NRC Request No. 1.Please provide the Westinghouse recommended mitigative measures deemed necessary for CPNPP, and if not yet implemented, the schedule for implementing the Westinghouse recommendations.

CPNPP Response: Westinghouse and the PWR Owners Group recommended (Ref. Direct Work Requests DW-01-017 dated 02/20/2008 and DW-12-13 dated 03/20/2013) that the following changes be made to generic Emergency Operating Procedures.

• ES-1.3, Loss of Reactor or Secondary Coolant (CPNPP EOS-1.3A for Unit 1 and CPNPP EOS-1.3B for Unit 2)Westinghouse recommended that the following be added to the PLANT-SPECIFIC INFORMATION section of the Step Description Table for Step 6 (Step 7 LP) of ES-1.3: "Some plants may be susceptible to blockage in the fuel assemblies due to debris passing through the sump screen. Plants can assess the impact of debris on equipment required by the ECCS and NSSS to maintain the core in a coolable geometry following an accident using WCAP-16406-P, Rev. 1, "Evaluation of Downstream Sump Debris Effects in Support of GSI-191". Susceptible plants should evaluate the use of available temperature monitoring (core exit thermocouples or PAMS) to initiate backflow through the core via hot leg recirculation on a potentially more frequent basis to ensure adequate core cooling. An analysis may be needed to determine the frequency of switching to and from hot-leg injection to satisfy core blockage requirements while addressing boron precipitation concerns." The corresponding step in the CPNPP procedures (step 14) determines if transfer to hot leg recirculation will be required.

The plant staff is consulted for this determination.

In accordance with the generic recommendation, this guidance was added to the Plant Staff Document for use by the Emergency Response Organization." FR.C.1 Response to Inadequate Core Cooling (CPNPP FRC-0-1A for Unit 1 and CPNPP FRC-0.1B for Unit 2) and FR.C.2 Response to Degrade Core Cooling (CPNPP FRC-0.2A for Unit 1 and CPNPP FRC-0.2B for Unit 2)Westinghouse recommended that the following be added to the PLANT-SPECIFIC INFORMATION section of the Step Description Table for Step 2 (HP and LP) of FR-C. 1 and Step 2 (HP and LP) of FR-C.2: "Some plants may be susceptible to blockage in the fuel assemblies due to debris passing through the sump screen. Plants can assess the impact of debris on equipment required by the ECCS and NSSS to maintain the core in a coolable geometry following an accident using WCAP-16406-P, Rev. 1, "Evaluation of Downstream Sump Debris Effects in Support of GSI-191". During the recovery, if SI flow is indicated and core cooling remains inadequate, SI flow may not be reaching the core due to blockage.

It may be possible to restore adequate core cooling by initiating backflow through the core via hot leg recirculation." These changes to CPNPP procedures have been implemented by incorporation into the bases for the corresponding step in CPNPP procedures (step 3) and by changes to the Plant Staff Document for use by the Emergency Response Organization.

Attachment to TXX-13149 Page 2 of 2 Westinghouse also recommended procedure changes for plants that use a Westinghouse-designed reactor vessel level indication system. These do not apply to the CPNPP Reactor Vessel Water Level Indication System (RVLIS) design which employs heated and unheated junction thermocouples as described in the CPNPP FSAR TMI RESPONSE TO NRC ACTION PLAN DEVELOPED AS A RESULT OF THE TMI-2 ACCIDENT,Section II.F.2 IDENTIFICATION OF AND RECOVERY FROM CONDITIONS LEADING TO INADEQUATE CORE COOLING.NRC Request No. 2.Please provide the details of actions performed by EOPs FRC-0-1A, FRC-0.1B, FRC-0.2A, and FRC-0.2B to deal with inadequate core cooling.CPNPP Response: CPNPP FRC-0-1A for Unit 1 and CPNPP FRC-0.1B for Unit 2 are titled Response to Inadequate Core Cooling. This procedure is entered from Critical Safety Function CORE COOLING Status Tree when Core Exit Temperature (CET) is greater than or equal to 1200 degrees F.CPNPP FRC-0.2A for Unit 1 and CPNPP FRC-0.2B for Unit 2 are titled Response to Degrade Core Cooling. This procedure is entered from Critical Safety Function CORE COOLING Status Tree when RCS subcooling is inadequate, Reactor Vessel Water Level Indication System (RVLIS) indicates low level in the vessel and Core Exit Temperature (CET) is greater than or equal to 750 degrees F.Both procedures are based on assuring emergency core cooling to the reactor vessel. None of the steps in the original generic or plant specific guidance dealt with core blockage.

There are no actions to be taken for core blockage other than switchover from cold leg recirculation to hot leg recirculation and back. Therefore, the guidance added is to contact the Plant Staff for specific guidance.The Shift Technical Advisors (STAs) and/or the Technical Support Center (TSC) engineers would monitor plant conditions and advise the control room operators regarding switchover from Cold Leg Recirculation to Hot Leg Recirculation and back.