ML12129A501

Donald C. Cook, Units 1 and 2 - RAI the Effect of Thermal Conductivity Degradation on Peak Cladding Temperature Analysis

ML12129A501
Person / Time
Site:	Cook
Issue date:	05/14/2012
From:	Tam P S Plant Licensing Branch III
To:	Weber L J Indiana Michigan Power Co
Tam P S
References
TAC ME8322, TAC ME8323
Download: ML12129A501 (5)

Text

May 14, 2012

Mr. Lawrence Senior Vice President and Chief Nuclear Officer Indiana Michigan Power Company Nuclear Generation Group One Cook Place Bridgman, MI 49106

SUBJECT: DONALD C. COOK NUCLEAR PLANT, UNITS 1 AND 2 -REQUEST FOR ADDITIONAL INFORMATION ON THE ISSUE OF PEAK CLADDING TEMPERATURE AFFECTED BY THERMAL CONDUCTIVITY DEGRADATION (TAC NOS. ME8322 AND ME8323)

Dear Mr. Weber:

By letter dated March 19, 2012 (Accession No. ML 12088A104), Indiana Michigan Power Company submitted its response to a Nuclear Regulatory Commission (NRC) staffs information request pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.54(f) related to the estimated effect on peak cladding temperature resulting from thermal conductivity degradation in the Westinghouse-furnished realistic emergency core cooling system (ECCS) evaluation. The licensee also stated that the March 19, 2012, letter served as a 30-day report of a significant ECCS evaluation model change or error in accordance with requirements of 10 CFR 50.46(a)(3). In the course of its 10 CFR 50.46 report review, the NRC staff determined that additional information is necessary to complete its review. A draft of a request for additional information (RAI, Accession No. ML 12086A002) was provided to facilitate discussion with the licensee; subsequently, the NRC staff conducted an audit at the Westinghouse Electric Company facilities in Cranberry Township, Pennsylvania, to further clarify the request for additional information and the contents required to be responsive to the request. The draft RAI has been revised and sent to the licensee by an e-mail ofApriI23.2012(AccessionNo.ML12115A004). On April 30, 2012, the NRC staff held a conference call with your staff and agreed to revise the RAI further, eliminating Question 4, and revising Question 10. The revised RAI was e-mailed to your staff on April 30, 2012 (Accession No. ML 12122A005).

L. The purpose of this letter is to formally convey the final RAI to you (see Enclosure). The NRC staff requests your response within 30 days of the date of this letter. Feel free to contact me if you need any further clarification of the questions in the enclosed RAI.

Sincerely,P er S. Tam, Senior Project Manager Plant Licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-315 and 50-316

Enclosure:

RAI cc w/encl: Distribution via ListServ REQUEST FOR ADDITIONAL INFORMATION D. C. COOK NUCLEAR PLANT THE ISSUE OF PEAK CLADDING TEMPERATURE AFFECTED BY THERMAL CONDUCTIVITY DEGRADATION Provide a table of data that includes the following ASTRUM inputs for AOR and integrated analyses: (1) AOR Run #, (2) TCD Run #, (3) PCT, (4) Time of PCT, (5) Fq, (6) FdH, (7) Cycle Burnup, (8) RCS Tavg, (9) Accumulator Temperature, (10) Safety Temperature, (11) Safety Injection Please highlight the limiting cases in the ASTRUM run matrices and explain how these cases were chosen. Provide details and explain the approach used to estimate (1) the effects of TCD and (2) the compensating model changes. Justify the selection of the number of WCOBRAITRAC cases that were re-executed, as opposed to a larger number of cases. Justify the containment pressure changes made to obtain margin on Unit 1. Provide reference to excerpts from the applicable methodologies to clarify the response. Your submittal referenced a March 7, 2012, letter sent by Westinghouse Electric Company (WEC) to the Nuclear Regulatory Commission (NRC). The final paragraph on Page 2 of 9 refers to small differences in fuel characteristics that were claimed to be compared. The paragraph also discusses confirmatory evaluations concluding that other operating characteristics were acceptable. Provide the results of this comparison for D. C. Cook, including the relevant conclusions and the technical basis supporting those conclusions. For any conclusion regarding differences in void volume are offset by other conservatisms, list those conservatisms and provide a quantitative estimate for each conservatism, as well as a brief description of the rigor associated with that estimate. Please provide the values for the coefficients used in the PAD 4.0 + TCD UOz thermal conductivity equation. Please explain any error corrections, code improvements, and miscellaneous code cleanup between the WCOBRAITRAC and HOTSPOT code versions used in the TCD evaluations and those used in the plant's AOR. What is the thermal conductivity model impact of code version changes in HOTSPOT? Explain the differences between the HOTSPOT and PAD thermal conductivity models and the impact of those differences. Provide graphs or other quantified descriptions that aid in explanation. Enclosure

-Please provide additional detail concerning the steady-state ASTRUM/CQD initialization process. In particular, please explain what fuel characteristics are adjusted within the applicable models to obtain convergence among HOTSPOT, WCOBRAITRAC, and PAD 4.0 + TCD. Please explain how the changed design values will be verified during operation of the plant, i.e., Technical Specification limits, Surveillances, etc. Also, explain what compensatory actions will be taken if a value is found to be outside of the limits assumed in the analysis. Fully explain all peaking factor adjustments and provide the rationale for each adjustment. At the bottom of Page 1 of Enclosure 2 to AEP-NRC-2012-13 it is stated that "I&M and WEC utilized processes which ensure that the LBLOCA [large-break loss-of-coolant accident] analysis input values conservatively bound the as-operated plant values for those parameters." Please explain these processes. Please explain the process for determining the establishment of a trend in the context of the following statement: "For the margin PCT calculation, WCOBRAITRAC cases were executed until an estimated trend could be established." Based on the NRC's review of the March 19,2012, submittal it appears that the licensee has revised inputs to a method of evaluation as described in the Final Safety Analysis Report (as updated) used in establishing the design bases or in the safety analyses. Revision 1 to NEI 96-07, "Guidelines for 10 CFR 50.59 Implementation," Section 3.8, "Input Parameters," (Accession No. ML003771157) provides clarifying information concerning whether an input parameter is considered to be an element of a methodology for the purposes of addressing the applicable requirements found at Title 10 of the Code of Federal Regulations (10 CFR) 50.59, "Changes, Tests, and Experiments." Address whether the methodology permits the licensee to establish how to select the value of an input parameter to yield adequately conservative results and whether the revised value is more conservative than that required by the selection method. Address whether any of the changes (i.e., to the U02 thermal conductivity equation) constitutes a change in the calculational framework used for evaluating behavior or response of a system, structure or component. Explain whether and how 10 CFR 50.59(c)(4) might apply to such a change.