ML110590577

Email Attachment, Rlbloca Round 2 RAIs Qs

ML110590577
Person / Time
Site:	Harris
Issue date:	02/28/2011
From:	Mozafari B Plant Licensing Branch II
To:	Bass K, Corlett D Progress Energy Carolinas
Mozafari B, NRR/ADRO/DORL, 415-2020
Shared Package
ML110590624	List: ML110590577 ML110590620
References
TAC ME3569
Download: ML110590577 (2)

Text

1. 10 CFR 50.46(a) requires that a number of postulated loss of coolant accidents of different break sizes, locations, and other properties be analyzed to provide assurance that the limiting loss of coolant accident has been analyzed. The NRC staff considers the time in core life to be among the other properties to be analyzed, and requests assurance that the EMF-2103(P)(A) Revision 0 time-in-life modeling approach is conservative relative to conceivable cases that are not explicitly analyzed.

Demonstrate that the time-in-life modeling approach in the EMF-2103(P)(A) evaluation model is bounding for fuel rods at all times in life when compensated for fuel thermal conductivity degradation issues. Provide the following:

a) Updated sensitivity study results based on the reference three-loop plant studied generically in Appendix B.1 of EMF-2103(P)(A) Revision 0, and incorporating the modeling correction applied to RODEX3A to account for the issues identified in NRC Information Notice 2009-23.

b) Comparison of those sensitivity study results to recent observed and planned HNP core designs to demonstrate that the sensitivity study, when updated, remains bounding and applicable to HNP.

2. 10 CFR 50.46(b) requires that cladding inner and outer surface oxidation be calculated if the fuel cladding is predicted to rupture. Provide the results of a detailed evaluation that demonstrates that the fuel will not experience clad ballooning or rupture during the analyzed sequences. Ensure that the evaluation accounts for the issues identified in IN- 2009-23 at all times in core life. Provide the acceptance criteria used for this evaluation and a justification for those acceptance criteria.

3. If the study for Item 2, above, indicates that clad ballooning or rupture could occur, recalculate the predicted peak cladding temperature and local oxidation, including an empirical assessment of the post-rupture heatup, recognizing the potential for pellet fragmentation and relocation. Alternatively, repeat the sensitivity studies in Appendix B.2 of EMF-2103(P)(A) including consideration of pellet relocation to a packing fraction as high as 70% in the balloon/burst region to demonstrate that the phenomenological arguments presented in B.2 are true.

4. The NRC staff position regarding pre-existing oxidation is that it must be considered in the calculation of emergency core cooling system performance. This position is documented in numerous references, including NRC Information Notice 98-29 and letters to the Nuclear Energy Institute dated March 31 and November 8, 1999.

Demonstrate that the limiting local oxidation result, when added to the pre-existing oxidation at all times in core life, remains below the 10 CFR 50.46(b) acceptance criterion.

5. The EMF-2103(P)(A) Revision 0 decay heat modeling approach is unacceptable in that, although it conservatively considers the fully saturated decay of U-235 only, the conservatism of this modeling approach is not quantitatively balanced against the inherently non-conservative approach of applying a constant decay heat multiplier for the duration of the postulated event. Provide sensitivity studies to demonstrate that the approach applied in the acceptable evaluation model is conservative relative to one that time-samples decay heat using the standard uncertainty at the sampled time step.

Alternatively, repeat the analysis using a bounding decay heat multiplier for all cases.

6. Regarding HNP Response to NRC staff RAI 4.a.3, in the letter dated December 9, 2010, characterize the uncertainty distribution that is sampled and added to the fuel centerline temperature augmentation.

7. HNP Response to staff RAI 4.a.2 states that the transient fuel pellet radial temperature profile is computed by solving the conduction equation of S-RELAP5. Material properties are taken from RODEX3A and incorporated into S-RELAP5. The HNP response to NRC staff RAI 4.a.3 states that a total adjustment is achieved by iterating a multiplicative adjustment to the fuel thermal conductivity until the desired fuel centerline temperature is achieved. Provide a scatter plot of the adjustment factor as a function of burnup for the HNP LOCA cases.

8. Provide a plot of temperature as a function of time with traces for the fuel centerline temperature, pellet average temperature, and cladding surface temperature for the limiting PCT case at the limiting node. Indicate the end of blowdown, start of refill, and start of reflood on the graph.

9. Provide the corrected and uncorrected radial temperature profiles for the hot rod at the time and location of the peak cladding temperature.

10. The NRC staff does not accept the HNP response to staff RAI 5, letter dated December 9, 2010. The safety analysis must reflect the plant technical specifications; otherwise, the safety analysis implementation would be inconsistent with 10 CFR 50.36 requirements. Demonstrate that the additional permissible pressurizer liquid mass (the difference between an analyzed maximum of 66.75 percent span versus an allowable 92 percent) provides a benefit to the analyzed ECCS performance, re-run the realistic analysis using a sampled range that corresponds to the TS-permitted values, or propose to revise TS 3.4.3 to reflect the range of pressurizer level that is analyzed in accordance with EMF-2103(P)(A) Revision 0.