ML121290123

Round 2, Draft Request for Additional Information, License Amendment Request to Revise Technical Specification 3.4.9, RCS Pressure and Temperature (P/T) Limits, to Revise Limit Curves and SRs

ML121290123
Person / Time
Site:	Cooper
Issue date:	05/07/2012
From:	Lynnea Wilkins Plant Licensing Branch IV
To:	Mccutchen E Nebraska Public Power District (NPPD)
Wilkins, L E, NRR/DORL/LPL4, 415-1377
Shared Package
ML121290080	List: ML121290081 ML121290123
References
TAC ME7324
Download: ML121290123 (2)

Text

REQUEST FOR ADDITIONAL INFORMATION NEBRASKA PUBLIC POWER DISTRICT COOPER NUCLEAR STATION DOCKET NO. 50-298 By letter dated September 22, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML11272A057), Nebraska Public Power District (the licensee) submitted a license amendment request (LAR) to revise the Technical Specifications (TSs) for Cooper Nuclear Station (Cooper). The proposed LAR would revise TS 3.4.9, "RCS [Reactor Coolant System] Pressure and Temperature (P/T) Limits," to include new pressure-temperature (P-T) limits for heat-up and cool-down operations with the core critical and core not critical, as well as for pressure test conditions. The proposed P-T limits would be valid for 32 effective full power years (EFPY) of facility operation. The proposed revisions to TS 3.4.9 also would revise surveillance requirements for verifying that the reactor vessel (RV) flange and RV head flange temperatures are greater than the revised minimum operating temperature (70 degrees Fahrenheit (ºF)) specified for the proposed 32 EFPY P-T limits.

By letter dated February 29, 2012 (ADAMS Accession No. ML120590085), the U.S. Nuclear Regulatory Commission (NRC) issued a request for additional information. By letter dated March 30, 2012 (ADAMS Accession No. ML12094A118), the licensee responded to the NRCs request. The NRC staff has reviewed and evaluated the information provided by the licensee and has determined that additional information is needed in order to complete its review.

BACKGROUND Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix G, Fracture Toughness Requirements, states, this appendix specifies fracture toughness requirements for ferritic materials of pressure-retaining components of the reactor coolant pressure boundary (RCPB) of light water nuclear power reactors to provide adequate margins of safety In addition, 10 CFR Part 50, Appendix G, Paragraph IV.A states that, the pressure-retaining components of the RCPB that are made of ferritic materials must meet the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),

supplemented by the additional requirements set forth in [paragraph IV.A.2, Pressure-Temperature (P-T) Limits and Minimum Temperature Requirements"] Therefore, 10 CFR Part 50, Appendix G requires that P-T limits be developed for the entire RCPB, consisting of ferritic RCPB materials in the reactor vessel (RV) beltline (neutron fluence 1 x 1017 n/cm2, E > 1 MeV), as well as ferritic RCPB materials not in the RV beltline (neutron fluence < 1 x 1017 n/cm2, E > 1 MeV).

ISSUE P-T limit calculations for ferritic RCPB components that are not RV beltline shell materials, may define curves that are more limiting than those calculated for the RV beltline shell materials.

This may be due to the following factors:

Enclosure

1. Some ferritic RCPB components that are not RV beltline shell materials, such as nozzles, penetrations, and other discontinuities, are complex geometry components that exhibit significantly higher stresses than those for the RV beltline region. These higher stresses can potentially result in more restrictive P-T limits, even if the reference temperature (RTNDT) for these components is not as high as that of RV beltline materials that have simpler geometries.

2. Ferritic RCPB components that are not RV beltline shell materials may have material properties, in particular initial RTNDT values, which may define more restrictive P-T limits that those for the RV beltline shell materials.

REQUEST Please describe how the P-T limit curves, and the methodology used to develop these curves, considered all ferritic RCPB materials, consistent with the requirements of 10 CFR Part 50, Appendix G.