ML20207Q671

Safety Evaluation Supporting Util Re Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events

ML20207Q671
Person / Time
Site:	Davis Besse
Issue date:	01/09/1987
From:	Office of Nuclear Reactor Regulation
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Shared Package
ML20207Q669	List: ML20207Q668 ML20207Q671
References
TAC-59950, NUDOCS 8701280494
Download: ML20207Q671 (3)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FRACTURE TOUGHNESS REQUIREMENTS FOR PROTECTION AGAINST PRESSURIZED THERMAL SHOCK EVENTS TOLEDO EDISON COMPANY AND THE CLEVELAND ELECTRTEILLUMINATING COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT NO. 1 DOCKET NO. 50-346

1.0 INTRODUCTION

On July 23, 1985, the Commission published in the Federal Register at 50 FR 29944, a final rule, 650.61, fracture toughness requirements for protection against pressurized thermal shock. This rule required the licensee for each operating pressurized water reactor to submit projected values of RT for reactor Nkse(as calculated l beltline by the The materials. method specified values of RTin the regulation) from the time of submittal to the expiration date of the operating licNke were to be supplied. The assessment was to be submitted by January 23, 1986. The rule, furthermore, requires that the assessment be updated whenever changes in core loadings, surveillance measurements, or other information indicate a significant change in projected values.

In compliance with the requirement of t cegulation. Toledo Edison Company submitted on January 21, 1986, information on material properties, fast neutron fluence, and projected values of PT for the PTS Davis-Besse reactor vessel beltline material.

2.0 EVALUATION OF MATERIAL ASPECTS Toledo Edison Company identified the controlling beltline material, from the standpoint of pressurized thermal shock susceptibility, to be the middle circumferential weld, WF182-1 (weld wire heat No. 821T44).

The material properties of the controlling material and the associated margin and chemistry factor were reported to be:

Utility Submittal Staff Evaluation Cu (copper content, %) 0.24 0.24 Ni (nickel content, %) 0.63 0.63 I (Initial RT NDT, F) 2 2 M (Maroin, F) 48 48 CF (Chemistry Factor, "F) 155.7 8701280494 870109 PDR ADOCK 05000346 P PDR

y The controlling material has been properly identified. The justifications are given for theThe acceptable. copper marginand has nickel beencontents derived fromand consideration the initial RT,N the bases for these values, following the PTS Rule, Section 50.61 of 10 CFR Part

50. Assuming that the reported values of fluence are correct, Equation 1 of the PTS rule governs, and the chemistry factor is as shown above.

3.0 Evaluation of the Fluence Aspects The licensee estimated the fluence to the pressure vessel to the end of the current license and also after 32 effective full-power years of operation and the corresponding values of RT PTS

• Flux and fluence calculations were performed using the Discrete Ordinates Code, 00T, and plant specific sources based on previous cycles. Last cycle sources were used to extrapolate to future cycles. The critical material was identified to be the middle circumferential weld WF182-1, thus, the peak azimuthal and longitudinal flux was used in the calculation of the RT . The 00T transport calculations have been compared to the latest suNhillancecapsuleresults. The method of the fluence calculation is conservative and acceptable.

The ecuation specified in 10 CFR 50.61, applicable for the Davis-Besse Unit 1 pressure vessel is:

0 RT PTS = I+M+(-10+470xCu+350xCuxNi)xf .27 where: I = Initial RT = 2*F M=Uncertainthargin = 48*F Cu = w/o Copper in weld WF 182-1 = 0.24 Ni = w/o Nickel in weld WF 182-1 = 0.63 f=PeakQuence2 n weld WF 182-1 in units of 10 n/cm to the end of the current license and 32 effective full power years respectively = 1.3,1.7 Then, to the end of the current license:

0 RT PTS = 2+48+(-10+470x0.24+350x0.24x0.63)x1.3 27

= 50+155.7x1.073 = 217.1*F which is less than 300 F i.e., the applicable screening criterion and, thus, acceptable. Similarly, for 32 effective full power years, the estimated RT = 50+155.7x1.154 = 229.7*F which is also less than the applicable 10NFR50.61criterionof300*Fandisacceptable.

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N 4.0 Conclusion The licensee has calculated values of RT at the end of the current .

licenseandafter32effectivefullpowepThearsofoperation. Both values are less than the applicable screening criteria for the limitina material i .e. , 300 F. This is acceptable. However, in view of:

(a) the Pressure-Temperature updating reauirements for the fracture toughness of the beltline material in 10 CFR 50, Appendix G, (b) the fact that the RT value is readily available from the calculation of the PEI$sure-Temperature limits, and (c) the staff's desire to be informed on the current value of the RT PTS' we request that Toledo Edison Company submit a reevaluation of the RT and a comparison to the prediction contained in the January 20, 1986 PTS submittal along with future Pressure-Temperature operating limits which are required by 10 CFR 50, Appendix G. It should be noted that this reevaluation is a requirement by 10 CFR 50.61, whenever core loadings, surveillance measurements, or other information indicate a significant change in project values.

Date: January 9,1987 Principal Contributors:

L. Lois P. N. Randall A. DeAgazio

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