ML20217E614

Safety Evaluation Accepting Util Proposed Changes to Licensing Basis for Plant to Reflect Incorporation of Safer/Gestr Methodology for LOCA Analysis

ML20217E614
Person / Time
Site:	Cooper
Issue date:	09/23/1997
From:	NRC (Affiliation Not Assigned)
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ML20217E606	List: ML20217E602 ML20217E614
References
NUDOCS 9710070103
Download: ML20217E614 (3)

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,l NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. sce6 Hoot SAFE 1Y EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO THE USE OF SAFER /GESTR-LOCA ANALYSIS NEBRASKA PUBLIC POWER DISTRICT COOPER NUCLEAR STATION DOCKET NO. S0-298

1.0 INTRODUCTION

By letter dated March 19, 1997 District (NPPD), the licensee, r(Reference 1), thefor equested changes Nebraska Public the Cooper Power Nuclear Station (CNS) to reflect the incorporation of the SAFER /GESTR methodology for loss-of-coolant accident (LOCA) analyses. Supplementing that letter, the licensee furnished the results of the SAFER /GESTR-LOCA analysis for CNS (Reference 2 .

a generic bas)is (Reference 3), has been previously approved by the NuclearUse o Regulatory Commission (NRC) staff. Review of the plant specific analysis against the conditions underlying staff acceptance of the generic SAFER /GESTR-LOCA methodology ensures conformance with the emergency core cooling system (ECCS) criteria of 10 CFR 50.46, 2.0 EVALUATION The NRC staff acceptance of SAFER /GESTR is described in a 1984 Topical Report Evaluation contained in Reference 3. The SAFER /GESTR methodology was accepted subject to limitations and the requirement-that both the nominal and Appendix K peak clad temperature (PCTNOM and PCT APP K) versus break size curves for the generic calculation for a given class of plants be demonstrated applicable to a specific plant. Necessary conditions demonstrating applicability are:

1. Calculation of a sufficient number of plant specific PCTNOM and PCTAPP K points to verify the shapes of the PCTNOM and PCTAPP K versus break. size curves. The trends of the plant specific PCTNOM and PCTAPP K curves must follow the applicable generic case.

2. Confirmation that plant specific operating parameters have been bounded by the models and inputs used in the generic calculations.

3. Confirmation that the plant specific ECCS configuration is consistent with the reference plant class ECCS configuration.

4. Restriction of the calculated upper bound peak cladding temperature (PCTUB) to less than 1600 'F.

ENCLOSURE 9710070103 970923 PDR P ADOCK 05000298 PDR

In Reference 2, the licensee furnished information confirming that the basic requiremer,ts for items 2, 3 and 4 are met for the CNS SAFER /GESTR application.  ;

The analyses include break sizes from 0.04 square feet to the design basis accident (DBA) recirculation suction line break. PCTNOM values were determined for eleven break sizes, and PCTAPP K values for four break sizes.

These break sizes were selected to yield conservative results relative to current CNS design information and Technical Specification (TS) requirements, j

Limiting MAPLHGR and power / exposure combinations were selected as inputs.

Although the ECCS component configuration for CNS matches the BWR/4 generic configuration, some parameters were selected to be conservative relative to current TS requirements or expected equipment performance. This was done to allow for subsequent changes to the TSs. Such conservative assumptions for the SAFER /GESTR analyses are permitted by the generic report, item 1 of the list of conditions includes the stipulation that the plant saccific PCT versus break size curves match the generically determined trends.

Tie PCTNOM curve is formed using best-estimate values of slant response. This curve establishes the limiting break (normally the larga areak LOCA) which is used for subsequent calculations. The PCTNOM curve shows a decreasing PCT as the break area decreases, which is consistent with the trend observed in the generic break spectrum (Reference 3). PCTAPP K is determined for the limiting

! case, and then an upper bound PCT (PCTUB) is determined to confirm the i

conservatism of PCTAPP K. The analysis presented in the generic report uses l

assumptions arising from conditions based on the large break event. The l

' requirements of the staff safety evaluation of the generic report ensure that plant LOCA response does not significantly diverge from the generic LOCA response and possibly invalidate application of SAFER /GESTR-LOCA analysis assumptions.

The results of the plant specific break calculations presented in the PCT versus break si:e plot in Figure 5-1 of Reference 2 establish that the large breaks are limiting. For CNS the small break PCTAPP K is lower than the DBA PCTAPP K, which confims that the large break LOCA is limiting. The DBA break is the recirculation suction line break with the DC power source single failure. For this case, the PCTNOM is 1103 'F and the PCTAPP K is 1539 'F.

The PCTUB is 1460 'F and the licensing basis PCT (PCTLB) is 1570 'F. The comparison of PCTLB to PCTAPP K assures that the methodology is conservative (PCTLB > PCTAPP K). To conform with 10 CFR 50.46 and the SAFER /GESTR-LOCA methodalogy: the PCTLB must be less than 2200 'F; the PCTUB must be less than the PCTLB; and the PCTUB must be less than 1600 'F. Since the plant specific analysis for CNS complies with the requirements stated above for applying the generic methodology to a specific plant, the application of SAFER /GESTR to CNS is considered acceptable. However, changes to plant operating conditions which could affect LOCA analyses should be evaluated by the licensee to ensure that the relationships between PCTUB, PCTNOM, PCTLB, and PCTAPP K are maintained, and that the large break remains the limiting case.

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-3 3.0 TECHNICAL SP.[CIFICATIONS 1

The following TS change is needed to accommodate implementation of the 1 SAFER /GESTR methodology. Prior to the ese of or reliance upon the SAFER /GESTR '

LOCA analysis for Cooper, Reference 3 the generic SAFER /GESTR report, shall be aoded to a list of documents describing analytical methods contained in the ap)ropriate TS Section entitled. ' Core Operating Limits Report" (TS Section 6.5.1.G for the current CNS Technical Specifications; Section 5.6.5 for the proposed improved Technical Specifications for CNS).

4.0 LONCLUSIONS NPPD has proposed changes to the licensing basis for CNS to reflect the incorporation of the SAFER /CESTR methodology for LOCA analyses. Based upon the licensee's March 19, 1997, submittal and previously approved General Electric analytical techniques and design data, implementation of SAFER /GESTR for CNS is acceptable.

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5.0 REFERENCES

1. Letter (NLS970040 from P.D. Graham (NPPD to USNRC dated March 19, 1997, transmitting reque)st for approval for use)of the SAFER /GESTR methodology at Cooper Nuclear Station.

2. NEDC-32687P, Revision 1, " Cooper Nuclear Station SAFER /GESTR-LOCA Loss-of-Coolant Accident Analysis," March 1997, (General Electric proprietary information)_

3. NEDE-23785-1-PA, "The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant Accident," Volume Ill, Revision 1, October 1984, (General Electric proprietary information).

Principal Contributor: R. Frahm NRR Date: September 23, 1997 u