ML20205G449

Safety Evaluation Accepting Projected Values of Matl Properties for Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events

ML20205G449
Person / Time
Site:	Beaver Valley
Issue date:	08/31/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20205G447	List: ML20205G443 ML20205G449
References
REF-GTECI-A-49, REF-GTECI-RV, TASK-A-49, TASK-OR NUDOCS 8608190505
Download: ML20205G449 (3)

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4@teuq kg UNITED STATES

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L :j NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555

\*.../ SAFETY EVAtUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION  :

REGARDING PROJECTED VALUES OF MATERIAL PROPERTIES FOR FRACTURE TOUGHNESS REQUIREMENTS FOR PROTECTION AGAlfiST PRESSURIZED TERfiAL Sf0CK EVENTS DUQUESNE LIGHT COMPANY BEAVER VALLEY POWER STATION, UNIT 1 DOCKET NO. 50-334 INTRODUCTION As required by 10 CFR 50.61, " Fracture Toughness Requirements for protection 1 Against Pressurized Thermal Shock" (PTS Rule) which was published in the Federal Register July 23, 1985, the licensee for each operating pressurized water reactor "shall submit projected values of RT PTS (at the inner vessel) surface) of reactor vessel beltline materials by giving values from the time of submittal to the expiration date of the operating license. The assessment must 1 specify the bases for the projection including the assumptions regarding core  ;

loading patterns. This assessment must be submitted by January 23, 1986, and l must be updated whenever changes in core loadings, surveillance measurements or i other information indicate a significant change in projected values."  !

By letter dated January 21, 1986, supplemented by letter dated May 16, 1986,  !

Duquesre Light Company (the licensee or DLC) submitted projected valuer for RT j PTS together with material properties and fast neutron fluence of reactor vessel beltline material for Beaver Valley Power Station, Unit 1. The RT fluence values were projected to 32 effective full power years (EN)and which is -

considered to be beyond the expiration date of the license.

EVALUATION OF THE MATERIALS ASPECTS The controlling beltline material from the standpoint of PTS susceptibility was identified to be lower shell plate B6903-1.

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

l Utility Submittal Staff Evaluation

! l i

C1(coppercontent,%) 0.20 0.20 l Ni (nickel content, %) 0.54 0.54 I (Initial RT 'F) 27 27 M (Margin *FyT, 1

43 j CF (Chemistry factor,*F) 121.8 8608190505 860811 4 DR ADOCK 0500 .

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l b

The controlling material has been properly identified. The justification given for the copper and nickel contents and the initial RT are acceptable. The margin has been derived from consideration of the baskTfor these values, following the PTS Rule, Section 50.61 of 10 CFR Part 50. Assuming that the i l

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

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EVALUATION OF THE FLUENCE ASPECTS The following evaluation concerns the estimation of the fluence to the pressure vessel for 32 effective full power years cf operation and the corresponding value of the RTPTS

• The licensee submitted additional information on May 16,19P6 in response to a staff request regarding the fast neutron fluence to the inside surface of the pressure vessel. The methodology of the fluence calculation was based on the l discrete ordinates code DOT with an ENDF-B/IV-based cross section set. The l scattering is treated with a P, approximation. The code has been henchmarked '

by Westinghouse and its predictions for the surveillance capsule locations are within 15% of the measured values. The methodology, the cross sections and the approximations used are acceptable.

l The equation specified (in 10 CFR 50.61) as applicable or the Beaver Valley Unit 1 plant is:

0 RTPTS = I+M+(-10+470.Cu+350.Cu.Ni).f .27 where: I = Initial RT = 27' M=Uncertainthargin = 48'F Cu = w/o Copper in shell plate B6903-1 = 0.20 Ni = w/o Nickel in shell plate B6903-2 = 0.54 for g 32 EFPY, lower shell plate f=peakfluence(E41.0Mg)n/cm B6903-1 in units of 10 . = 4.5 Therefore:

0 RTPTS = 27+48+(-10+470x0.20+350x0.20x0.54)x4.5 27

= 75+121.8x1.5 = 257.8'F which is lower than 270*F the applicable PTS rule screening criterion and is acceptable.

In view of:

(a) the Pressure-temperature updating requirements for the' fracture toughness of the beltline material in 10 CFR 50 Appendix G, and l

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(b) the fact that the RT value is readily available from the calculation ofthePressure-tempNhturelimits,and (c) the staff desire to be informed on the current value of the RTPTS f r all PWRs, we request that the licensee submit a re-evaluation of the RTPTS and a comparison to the prediction of Reference 1 along with future Pressure-Temperature operating limits which are required by 10 CFR 50 Appendix G.* It should be noted that this re-evaluation is a requirement by 10 CFR 50.61, whenever core loadings, surveillance measurements, or other infomation indicate a significant change in projected values.

CONCLUSION The licensee has calculated a RT of 257.8'F for plate material at the erd of 32 EFPY, which is same as the nokIbal 3E EFPY considered in the development of the PTS Rule. This is less than 270 F, the screening criteria for the limiting material at the expiration date of the license. This is acceptable. However, in order for the staff to confim the licensee's projected estimated RT throughoutthelifeoftheBeaverValleyIoperatinglicense,thelicenNhis requested to submit a re-evaluation of the RT and comparison to the predicted value with future pressure-temperatNh submittals which are required by 10 CFR 50, Appendix G.

Principal contributors P.N. Randall Lambros Lois l

Dated l August, 1986