ML20214R548
| ML20214R548 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 11/26/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20214R539 | List: |
| References | |
| REF-GTECI-A-49, REF-GTECI-RV, TASK-A-49, TASK-OR NUDOCS 8612080017 | |
| Download: ML20214R548 (3) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION o
,E WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REGARDING PROJECTED VALUES OF MATERIAL PROPERTIES FOR FRACTURE TOUGHNESS REQUIREMENTS FOR PROTECTION AGAINST PRES 5URIZED THERMAL 5H0CK EVENTS COMMONWEALTH EDISON COMPANY BYRON STATION, UNIT 1 DOCKET NO. STN 50-454 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)ofreactorvesselbeltlinematerialsbygbng(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, 1985, 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 17, 1986, the Commonwealth Edison Company, licensee for the Byron Unit 1 plant, submitted information on the material properties and the fast neutron fluence (E E 1.0 MeV) of the reactor pressure vessel in compliance with the requirements of 10 CFR 50.61. The following evaluation concerns the estimation of the fluence to the pressure vessel for 32 effective full power years of operation and the corresponding value of RT PTS
- EVALUATION OF THE MATERIALS ASPECTS The controlling beltline material from the standpoint of PTS susceptibility was identified to be the upper shell forging SP-5933.
The material properties of the controlling material and the associated margin and chemistry factor were reported to be:
Utility Submittal Staff Evaluation l
Cu (copper content, %)
0.05 0.05 i
l Ni (nickel content, %)
0.73 0.73 I (Initial RT F) 40 40
- NDT, M (Margin, 'F) 48 48 i
CF (Chemistry Factor, F) 26.3 8612ca0017 861126 DR ADOCK 0500 4
-O V The controlling material has been properly identified. The justifications given for the copper and nickel contents and the initial RT are acceptable.
The margin has been derived from consideration of the bases N r these values, N
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.
EVALUATION OF THE FLUENCE ASPECTS AND THE CALCULATED RTn73 The methodology of the fluence calculation was based on the discrete ordinates code DOT using " Sailor" an ENDF-B/IV based cross section set.
The scattering is treated with a P approximation. The power distribution utilized in the 3
analysis was derived from statistical studies of lona-tenn operation of Westinghouse 4-loop plants. These distributions include the out-in fuel management and are conservative. The upper shell forging SP-5933 was identified as the controlling material. The peak axial and azimuthal fluence is the applicable value for the estimation of the RT The code was bench-marked by Westinghouse.
Themethodology,thecrossNhtionsandthe approximations used are acceptable.
The equation specified in 10 CFR 50.61, as applicable for the Byron Unit 1, plant is:
PTS = I+M+(-10+470xCu+350xCuxNi)xf.27 0
RT where:
I = Initial RT M =Uncertaintfkargin
= 40'F Cu = w/o Copper in shell forging SP-5933
= 48 F Ni = w/o Nickel in shell forging SP-5933
= 0.05 f = peak azimuthal fluence for 32 effective
= 0.73 fuypoweg.vears(E 1.0 MeV) in units of g
= 2.80 10 n/cm Therefore:
RTPTSY = 40+48+(-10+470x0.05+350x0.05x0.73) x 2.8 27 0
= 88+26.3x1.32 = 88+34.7 = 122.3"F which is less than 270'F, the applicable screening criterion and is acceptable.
CONCLUSIONS The licensee has calculated a RT of 122.3 F for plate material at the end of the 32 EFPY considered in the dhvelopment of the PTS Rule. This is less p
then 270 F which is the screening criteria for the limiting material at expiration date of the license. This is accpetable. However, in order for the staff to confirm the licensee's pro.iected estimated RT throughout the life of the Byron Unit 1 operating license, the licensee 1EThequired to submit a re-evaluation of the RT and comparison to the predicted value with future Pressure-TemperaturesubmSIkalswhicharerequiredby10CFR50,AppendixG.
PRINCIPAL CONTRIBUTORS L. Lois L. Olshan P. N. Randall Date:
.