ML20202A753

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

ML20202A753
Person / Time
Site:	Prairie Island
Issue date:	06/23/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20202A736	List: ML20202A732 ML20202A753
References
REF-GTECI-A-49, REF-GTECI-RV, TASK-A-49, TASK-OR TAC-59974, TAC-59975, NUDOCS 8607100121
Download: ML20202A753 (3)

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i SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REGARDING PROJECTED VALUES OF MATERIAL PROPERTIES FOR FRACTURE TOUGHNESS REQUIREMENTS FOR PROTECTION AGAINST PRESSURIZED THERMAL SHOCK EVENTS NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT NO. 2 DOCKET NO. 50-306 INTRODUCTION As required by 10 CFR 50.61, " Fracture Toughness Requirements for Protection 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 surface)ofreactorvesselbeltlinematerialsbyg$Nng(attheinnervessel values from the time of submittal to the expiration date of the operating license. The assessment must specify the bases for the projection including the assumptions regarding core loading patterns. This assessment must be submitted by January 23, 1986, and must be updated whenever changes in core loadings, surveillance measurements or other information indicate a significant change in projected values."

By letter dated January 10, 1986, Northern States Power Company (the Licensee) submitted projected values of RT together with material properties and fast neutronfluenceofreactorvesse$TbeltlinematerialforthePrairieIsland Nuclear Generating Plant Station, Unit No. 2. The RT and fluence values were projected to June 25, 2008, the expiration date N the current license.

By letter dated February 21, 1986, the licensee has applied for a license amendment which would extend the operating license to October 29, 2014. This evaluation deals only with the reactor vessel material properttes and fluence to the expiration date of the current license, June 25, 2008.

EVALUATION OF THE MATERIALS ASPECTS The controlling beltline material from the standpoint of PTS susceptibility was identified to be the circumferential weld joining the intermediate to the

, lower shell forging (weld W-3), Weld Wire heat number 3049. The material properties of the controlling material and the associated margin and chemistry i factor were reported to be:

Utility Submittal Staff Evaluation Cu (copper content, %) 0.19 0.19 Ni (nickel content, %) 0.13 0.13 I (Initial RT PTS, F) 0.0 0.0

' 8607100121 860623 PDR ADOCK 05000306 p PDR

1 o Utility Submittal Staff Evaluation M (Margin, *F) 59 59 CF (Chemistry Factor, *F) 88 The controlling material has been properly identified. The justification are given for the The acceptable. copper marginandhas nickel oeen contents and the derived from initial RT" N the bases for consideration these values, following the PTS Rule, Section 50.61 of 10 CFR Part 50.

Equation 1 of the PTS Rule governs, and the chemistry factor is as shown above.

EVALUATION OF THE FLUENCE ASPECTS The maximum azimuthal fluence at the limiting weld material, thefircumjerential Weld, W-3 Weld Wire Heat No. 3049, was determined to be 4.3 x 10 n/cm at the end of the current license. The Prairie Island Unit No. 2 fluence was estimated using an accepted two dimension transport code. Details of the methodology are described in the licensee's submittal dated January 10, 1986. The methodology and results were found acceptable.

EVALUATION OF THE CALCULATED RTog According to the PTS Rule, 10 CFR 50.61, the applicable equation for calculating RT PTS is:

RT PTS = I+M+(-10+470xCu + 350xCuxNi) f.27 Where: I =

initial RTNDT = 0 F M = uncertainty = 59 F Cu =  % copper in weld W-3 = 0.19 Ni =  % nickel in weld W-3 = 0.13 f =

peakfluege([/ng W-3 x 10 cm 1.0 MeV) on weld = 4.3 0

Then: RT PTS = 0+59+(-10+470x0.19+350x0.19x0.13)4.3 27 RTPTS = 59+87.95x1.483=189.4*F To quantify the margin in terms of the fluence required to reach the screening criterion the staff solved the following equation:

300 = 59+87.95xf.27 9p f.27 = 241 = 2.74 87.95 or f = 41.8 (where this fluence value is outside the limits of the available experimental data of Reg. Guide 1.99) and in terms of the end of life peak weld W-3 fluence it is 41.8/4.3 = 9.7 1.e., the fluence to the end of 32 EFPYs is about 10% of that required to reach the screening criterion.

, For circumferential weld material the governing of screening criteria at the expiration date of the license is 300*F. 189.4*F is less than 300 F by a very large margin (110.6 F). This meets the requirements of the PTS Rule and is acceptable.

CONCLUSIONS Calculations show that RT is 189.4 F for the limiting circumferential weldmaterialattheexpihIkionattheexpirationdateofthelicense. This is less then 300 F by a considerable margin which is the screening criteria for the limiting material at the expiration date of the license. This is acceptable and thus meet" the requirements of the PTS Rule.

In order for us to confirm the licensee's projected estimated RT p thelifeofthelicensewewillrequestthelicenseetosubmitaIhthroughout evaluation of the RT and comparison to the predicted value with future Pressure-TemperatuhIbsubmittals which are required by 10 CFR 50, Appendix G.

Date:

Contributers to this SER: P. N. Randall L. Lois D. Dilanni 9

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