ML12086A002

Draft RAI on Licensee'S Response to 10 CFR 50.54(f) Letter Regarding Thermal Conductivity Degradation

ML12086A002
Person / Time
Site:	Cook
Issue date:	03/23/2012
From:	Tam P Plant Licensing Branch III
To:	Etheridge H, Waters J, Scarpello M Indiana Michigan Power Co, American Electric Power
Tam P
References
TAC ME7947, TAC ME7948
Download: ML12086A002 (2)

Text

Accession No. ML12086A002 From: Tam, Peter Sent: Friday, March 23, 2012 9:10 AM To: mkscarpello@aep.com; hletheridge@aep.com; 'jrwaters@aep.com' Cc: Parks, Benjamin; Woodyatt, Diana; Gall, Jennifer; Ulses, Anthony; Williams, Shawn; Lennartz, Jay; LaFlamme, Paul; Giessner, John

Subject:

D.C. Cook - Draft RAI on the response to the 10 CFR 50.54(f) letter re. thermal conductivity degradation (TAC ME7947 and ME7948)

Michael:

We prepared the following draft RAI questions that we plan to discuss with you in the conference call that we have already set up for 1:00 p.m. Eastern time, 3/23/12 (Friday). In the conference call, we will discuss with you the proposed response date, and any need to revise these questions.

1. Provide a table of data that includes ASTRUM inputs treated statistically, as well as key results[1], by WCOBRA/TRAC case number used pre- and post-completion of the estimation of the effect of thermal conductivity degradation on peak cladding temperature.

2. Please highlight the limiting cases in the ASTRUM run matrices and explain how these cases were chosen. Provide details and explain the order statistics approach used on the selected cases. Justify the selection of the number of WCOBRA/TRAC cases that were re-executed, as opposed to a larger number of cases.

3. Provide the number of cases that were re-executed to develop the off-setting margin assessment. Please provide similar information justifying the selection of this number of cases as in 2., above.

4. Your submittal referenced a March 7, 2012 letter sent by Westinghouse Electric Company to the NRC.

a. In the final paragraph on page 2 of 9, the document states, Small differences between the void volumes may exist for rods with the same cladding diameter, however, these differences in void volumes have been compared, and the components of the void volume calculations are either conservative or the changes in void volume are negligible after considering other conservatisms.

Core operating conditions and powers were also confirmed to either be bounding, the same, or offset by other margins. The representative fuel temperatures and rod internal pressures are either similar or bound those expected for plant specific calculations. Provide the results of this comparison for D.C. Cook, including the relevant conclusions and the technical basis supporting those conclusions. For any conclusion that differences in void volume are offset by other conservatisms, list those conservatisms and provide a

[1]

Key results include peak cladding temperature, local oxidation, time of PCT

quantitative estimate of each conservatism, as well as a brief description of the rigor associated with that estimate.

b. Please provide the values for the coefficients A1 and A2 used in the PAD 4.0 +

TCD UO2 thermal conductivity equation.

c. Please explain any error corrections, code improvements, and miscellaneous code cleanup between the WCOBRA/TRAC and HOTSPOT code versions used in the TCD evaluations and those used in the plants AOR.

d. What is the thermal conductivity model impact of code version changes in HOTSPOT?

e.

5. Explain the differences between the TRANSURANUS and PAD computer codes and the impact of those differences. Provide graphs or other quantified descriptions that aid in explanation.

6. Justify the containment pressure changes made to obtain margin and explain why this change does not warrant re-seeding. Provide reference to excerpts from the applicable modeling guidance documents to clarify the response.

7. Explain the double-ended adjustments made for the accumulator temperature and why they are not symmetric.

8. Fully explain all peaking factor adjustments and provide the rationale for each adjustment.

9. 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 analysis input values conservatively bound the as-operated plant values for those parameters. Please explain these processes.

10. Please explain how the updated values on the table on Page 3 of 6 of Enclosure 2 to AEP-NRC-2012-13 will be verified during operation of the plant, i.e. TS 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.

11. Please explain the process for determining the establishment of a trend in the context of the following statement: For the margin PCT calculation, WCOBRA/TRAC cases were executed until an estimated trend could be established.

Peter S. Tam Senior Project Manager (for D. C. Cook and Monticello)

Plant Licensing Branch III-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Tel. 301-415-1451