ML15201A512

Request for Additional Information Regarding License Amendment Request to Support a Measurement Uncertainty Recapture Power Uprate for Catawba, Unit 1

ML15201A512
Person / Time
Site:	Catawba
Issue date:	08/13/2015
From:	Geoffrey Miller Plant Licensing Branch II
To:	Henderson K Duke Energy Carolinas
Miller G
References
TAC MF4526, TAC MF4527
Download: ML15201A512 (6)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 August 13, 2015

• Mr. Kelvin Henderson Site Vice President Catawba Nuclear Station Duke Energy Carolinas, LLC 4800 Concord Road York, NC 297 45

SUBJECT:

CATAWBA NUCLEAR STATION, UNITS 1AND2: REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO SUPPORT A MEASUREMENT UNCERTAINTY RECAPTURE POWER UPRATE FOR CATAWBA, UNIT 1 (TAC NOS. MF4526 AND MF4527)

Dear Mr. Henderson,

By letter dated June 23, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML14176A109}, Duke Energy Carolinas, LLC submitted a license amendment request to increase the Catawba, Unit 1, authorized core power level from 3,411 megawatts thermal (MWt) to 3,469 MWt, an increase of approximately 1. 7 percent rated thermal power.

The U.S. Nuclear Regulatory Commission (NRG) staff has reviewed the licensee's submittal and determined that additional information is needed in order to complete the NRG staff's review ..Enclosure 1 describes this request for additional information. The NRG staff requests a .

response form Duke within 90 days from the date of this letter.

• The NRG staff notes that the RAls identified with the prefix SRXB relate to the review of the new neutron fluence methodology incorporated in the LAR. *,

• K. Henderson If you have any questions, please call me at 301-415-2481.

Sinc:et 0~Djff ,a'1

.. J

.G. Edward Miller, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-413 and 50-414

Enclosure:

As stated cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION UCENSEAMENDMENTREQUESTTOSUPPORTTHE MEASUREMENT UNCERTAINTY RECAPTURE POWER UPRATE DUKE ENERGY CAROLINAS, LLC CATAWBA NUCLEAR STATION, UNITS 1AND2 DOCKET NOS. 50-413AND 50-414 TAC NOS. MF4526 AND MF4527 By letter dated June 23, 2014, Duke Energy Carolinas, LLC, the licensee for Catawba Nuclear Station, Units 1 and 2 (Catawba), requested a measurement uncertainty recapture (MUR) power uprate (Agencywide Documents Access and Management System (ADAMS) Accession No. ML14176A109). The proposed revision would increase the Catawba, Unit 1, authorized.

core power level from 3411 megawatts thermal (MWt) to 3469 MWt, an increase of 1. 7 percent rated thermal power (RTP).

Based on the review of the amendment request, the NRC staff has determined that additional information is required regarding the MUR power uprate .

. Reactor Systems Branch (SRXB) - RAI 8 SRXB-RAI 11 The basis of review for RAPTOR-M3G is Regulatory Guide (RG) 1.190, "Calculational and Dosimetry Methods for Determining Pressure Vessel Neutron Fluence." RG 1.190 intends to ensure the accuracy and reliability of the neutron fluence determination required by General Design Criteria (GDC) related to the reactor coolant pressure boundary. RG 1.190 describes methods and assumptions acceptable to the NRC staff for determining the pressure vessel.

neutron fluence. RG 1.190 specifies that the neutron transport methods should be benchmarked to a statistically significant data base of measurement-to-calculation ratios (M/C) and that an overall neutron fluence bias and uncertainty be estimated. The NRC. staff requests that the licensee provide an explanation for how RAPTOR-M3G satisfies this portion of RG 1.190.

SRXB-RAI 12 In Section IV.1.C.ii of the application, the licensee states that Westinghouse has evaluated the latest-available ENDF/B-Vll-based cross-section data contained in the BUGLE-B7 library and the results of this evaluation indicate no significant differences between the results of analyses performed using two different cross-section data. This evaluation can be found in Appendix B of WCAP-16083-NP, Revision 1, "Benchmark Testing of the FERRET Code for Least Squares Enclosure

Evaluation of Light Water Reactor Dosimetry," dated April 2013. Appendix Bin WCAP-16083-NP, Revision 1, discusses the evaluation of the two cross-section sets by Oak Ridge National Laboratory for applications related to fluence. However, the Westinghouse evaluation only refers to work related to low-energy neutrons. There is an apparant conflict between statements made ir:i the application and Appendix 8 of WCAP-16083-NP, Revision 1, with respect to the Westinghouse evaluation of two multi-group cross section libraries. The NRC staff requests that the licensee clarify the statements or provide a revision of the relevant paragraph in Section IV.1.C.ii of the application and/or Appendix B ofWCAP-16083-NP, Revision 1.

SRXB-RAI 13 I

The use of Sa angular quadrature is generally acceptable according to RG 1.190. However, RG 1.190 states that when off-midplane locations are analyzed, the adequacy of the Sa quadrature to determine the streaming component must be demonstrated with higher-order Sn calculations. It is noted for Catawba, Unit 1, that one of the limiting locations is near the extended beltline. The analysis of Catawba, Unit 1, for the MUR includes an angular discretization "modeled with an Sa order of angular quadrature or higher." Since some of the locations of interest are on the extended beltline, it must be shown that the angular quadrature for those calculations .is adequate. The NRC staff requests that the licensee provide the angular quadrature used for the locations that are off-midplane. Additionally, the NRC staff requests that the licensee provide a justification for the angular quadrature.

SRXB-RAI 14 RG 1.190 requires that the neutron fluence methodology be qualified, and flux uncertainty estimates be determined. One component of the uncertainty is from the analytical sensitivity studies. The important sources of "analytical uncertainty" .are listed in RG 1.190, Section 1.4.1, "Analytic Uncertainty Analysis." The analytical sensitivity studies using RAPTOR-M3G are important in determining the overall uncertainty in neutron fluence calculations: The NRC staff requests that the licensee provide justification for the parameters that are important to performing neutron fluence analysis. Additionally, the NRC staff requests that the licensee provide the resulting uncertainties for each parameter and all parameters combined.

SRXB-RAI 15 The Pool Critical Assembly (PCA) benchmark is a full-scale section mockup of a pressure vessel with dosimetry measurements at the inner surface of the pressure vessel, and at locations within the pressure vessel wall. The PCA benchmark is one of the three suggested RG 1.190 benchmarks for pressure vessel simulator measurements. The PCA benchmark has been calculated using both TORT and RAPTOR-M3G with identical assumptions an.d the codes produced identical results. The spatial differencing in RAPTOR-M3G can be performed using either theta-weighted (TW) or directional theta-weighted (DTW) options. For the direct comparisons with TORT, the TW option is used in RAPTOR-M3G as TORT does not have the DTW option. The DTW is the normal option used in the Catawba neutron fluence analysis using RAPTOR-M3G. In order to determine the M/C ratios based .on the PCA measurements, RAPTOR-M3G should be used with the DTW option. The NRC staff requests that the licensee provide RAPTOR-M3G results for the PCA benchmark, as part of the code validation, using the same modeling assumptions used for the Catawba neutron fluence calculations.

SRXB- RAI 16 The analysis of the H.B. Robinson benchmark using RAPTOR-M3G is provided in Appendix A of WCAP-16083-NP, Revision 1. The analysis is performed using Ps expansion of the scattering kernel and an S12 angular quadrature as compared to Ps and Ss quadratures used in the Catawba neutron fluence analysis. In Section A.2 of WCAP-16083-NP, Revision 1, it is stated that the results in Appendix A made no attempt to address power redistribution effects over the course of the fuel cycle when calculating measured reaction rates at saturation, whereas the results presented in Section 3.3 did consider power redistribution. The analysis of the benchmark is atypical, although there is good agreement with the data. The NRC staff

• requests that the licensee provide the results for the H.B. Robinson benchmark using the standard methodology used for the Catawba neutron fluence analysis for qualification of RAPTOR-M3G.

SRXB-RAI 17 The comparisons of RAPTOR-M3G calculations with capsule data are discussed in Appendix A of WCAP-16083-NP, Revision 1, and in Appendix C of WCAP-17669-NP, Revision 0, "Catawba Unit 1 Measurement Uncertainty Recapture (MUR) Power Uprate: Reactor Vessel Integrity and Neutron Fluence Evaluations," dated June 2013 (ML14353A029). A requirement of RG 1.190 is that the uncertainty and bias in the neutron fluence calculations be assessed based on three components: surveillance measurements, benchmarks, and analytical sensitivity .studies.

a) The NRC staff requests that the licensee provide an explanation for how each component of uncertainty will be weighted to arrive at the uncertainty and bias for fast neutron fluence at the limiting vessel locations.

• b) The component of uncertainty and bias from comparisons of calculations with surveillance capsule data should be from a statistically significant number of measurements. The NRC staff requests that the licensee provide a justification of the use of the database, used to assess RAPTOR-M3G, based' on its statistical significance.

Electrical Engineering Branch (EEEB) - RAI 8 In Duke Energy's RAI response dated January 22, 2015 for EEEB RAI 6, it stated that "Locations on Elevation 560' were existing EQ HARSH zones due to the overall Total Integrated Dose (TIO} with identified EO equipment. Locations or:i Elevations 577' and 594' were existing EQ MILD zones that were projected to transition to EQ HARSH dose levels due to this issue."

Please confirm that the replacer:nent of additional lead shielding.in the affected equipment areas would transition the locations on Elevations 577' and 594' back from EQ Harsh to EO Mild. In addition, please verify that with the addition of lead shielding on the Annulus Penetrations on Unit 1, locations on Elevations 577' and 594' will be within the TIO values listed iri the Catawba EQCM and are qualified for pre-MUR and post-MUR power uprate conditions.

ML15201A512. *Via E-mail OFFICE NRR/LPLl-1 /PM NRR/LPL2-1/LA NRR/DSS/SRXB NRR/DE/EEEB NRR/LPL2-1/BC NAME GE Miller SFigueroa CJackson JZimmerman RPascarelli DATE 08/12/15 08/13/15 08/12/15* 08/12/15 08/13/15