ML20154B213

Safety Evaluation Supporting Fracture Toughness Requirements for Protection Against PTS Events,Per 10CFR50.61

ML20154B213
Person / Time
Site:	Sequoyah
Issue date:	05/05/1988
From:	NRC OFFICE OF SPECIAL PROJECTS
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ML20154B197	List: ML20154B194 ML20154B199 ML20154B213
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NUDOCS 8805170112
Download: ML20154B213 (3)

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SAFETY EVALUATION BY THE OFFICE OF SPECIAL PROJECTS  :

FRACTURE TOUGHNESS REQUIREMENTS FOR PROTECTION AGAINST PRESSURIZED THERMAL SHOCK EVENTS (10 CFR 50.61) t TENNESSEE VALLEY AUTHORITY  ;

SE000YAH NUCLEAR PLANT, UNIT 2 DOCKET NO. 50-328  !

1.0 INTRODUCTION

Inaccordancewith10CFRPart50.61(b)(1),eachpressurizedwaterreactor licensee shall have sub;nitted an assessment of the pressure vessel reference temperature by January 23, 1985. This assessment of the reference temperature  !

at the inner surface of the reactor vessel beltline materials is projected from  !

the time of submittal to the expiration of the license. The assessment must specify the bases for the projection and the assumptions regarding core loading  !

patterns. It must be updated whenever changes in core loadings, surveillance measurements or other infomation indicate a significant change in projected i reference temperature values.

2.0 EVALUATION [

By letter dated January 21, 1986, theTennesseeValleyAuthority(TVA) submitted information for Seouoyah Unit 2 on the material properties and the ,

fast neutron fluence (E greater than 1.0 MeV) of the reactor pressure vessel in  ;

d compliance with the requirenents of 10 CFR 50.61 (See References 1 and 2),

2.1 Material Properties

The controlling beltline material from the standpoint of PTS susceptibility was identified by TVA to be the intermediate forging. The material properties '

of the controlling material and the casociated margin and chenistry factor were

, reported by TVA to be:

4 TVA Submittal Staff Evaluation Cu (copper content, %) 0.13 0.13

Ni (nickel content, %) 0.74 0.74 i I (Initial RT*DT, F +10 +10 ,

M (Margin, 'F7 -- 48  :

CF (Chemistry Factor. *F) -- 84.8 8005170112 000505 PDR ADOCK 05000327 P PDR  ;

2 The results of the staff's evaluation are given in the second column above.

The controlling material has been properly identified. The justifications given for the copper and nickel contents and the initial reference temperature, as defined in the ASME Code, Paragraph NB-2331, (RTNDT) are acceptable.

The margin has been derived from consideration of the bases for these values, following the PTS rule (10 CFR Part 50.61). Based on the reported values of fluence, Equation 1 of the PTS rule governs and the chemistry factor is as shown in the above table.

2.2 Fast Neutron Fluence The following evaluation concerns the estimation of the fluence to the pressure vessel for 32 effective full power years of operation and the equations in 10 CFR Part 50.61(b)(2). The 32 effective full power years represent a 40-year design life based on an 80 percent capacity factor.

The methodology of the fluence calculation was based on the discrete ordinates code 00T with an ENDF-B/IV based cross section set. The scattering is treated approximation, plant specific sources were used and the code has with been a P,hmarked by Westinghoun. Its predictions for the surveillance benc capsule locations are within 215% of the measured values. The intermediate vessel forging has been identified as the controlling material, therefore, the applicable value of the fluence is the peak of the azimuthal distribution. The fluence estimate is conservative and no future low leakage core loadings were assumed. The methodology, the cross sections and the approximations used are ,

acceptable.

The applicable equation specified in 10 CFR 50.61(b)(2) for the pressure vessel PTS reference temperature RTPTS) for Sequoyah Unit 2 plant is the following:

0 RT PTS = !+H+(.10+470.Cu+350.Cu.Ni).f .27 where:

I = Initial RT hDT = 10*F M = Uncertainty Margin = 48'F Cu = w/o Copper in Intermediate Forging = 0.13 Ni = w/o Nickel in Intermediate Forging = 0.74 f = Peak Azimuthal Fluence for 32 EFPY (E or greater than 1.0 MeV)

Intermediate 19 2 Forging in units of 10 n/cm = 3.01 Therefore; the PTS reference temperature is:

0 RT PTS58+84,8

== 10+48+(-10+470x0.13+350x0.13x0.74)x3.0 x1.347 = 172.1*F

~

-3 which is lower than 270'F which is the app!! cable PTS rule screening criterion in10CFRPart50.61(b)(2)and,therefore,theprojectedPTSreference temperature for Unit 2 is acceptable.

3.0 CONCLUSION

The staff concludes, based on the above, that the pressure vessel PTS reference temperature defined in 10 CFR Part 50.61(b)(2) is less than the applicable PTS screening criterion. Because the PTS reference temperature is projected to be within the screening criterion through the expiration of the Unit 2 license, TVA does not have to addrer* 10 CFR Part 50.61(b)(3). In accordance with 10 CFR 50.61(b)(1), the ! Tir will request that TVA submit an update to the information in the TVA 1 :.: P 4ated January 21, 1986 whenever changes in core loadings, surveillance n tt 't.oents, or other information indicate a significant change in projected refeiecca temperature values.

4.0 REFERENCES

1. Letter from J. A. Domer, Tennessee Valley Authority to Director, NRR dated January 21, 1986,

2. WCAP-10509, "Analysis of Capsule T from the Tei... .ee Valley Authority Sequoyah Unit 2 Reactor Vessel Radiation Surveillance Program" dated April, 1984 Principal Contributors: L. Lois, P. N. Randall Cated: May 5, 1988 l

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