ML16341E410
| ML16341E410 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 10/30/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16341E409 | List: |
| References | |
| TAC-59951, TAC-59952, NUDOCS 8711030526 | |
| Download: ML16341E410 (10) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REGARDING PROJECTED VALUES OF MATERIAL PROPERTIES FOR FRACTURE TOUGHNESS RE UIREMENTS FOR PROTECTION AGAINST PRESSURIZED THERMAL SHOCK EVENTS PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON NUCLEAR POMER PLANT UNITS 1 AND 2 DOCKET NOS.
50"275 AND 50-323 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 RTPTS (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 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 17, 1986, as supplemented April 7, 1986, Pacific Gas 8
Electric Company (the licensee or PG&E) submitted projected values of RTPTS together with material properties and fast neutron fluence of reactor vessel beltline material for Diablo Canyon Nuclear Power Plant, Unit Nos.
1 and 2.
The RT T and fluence values were projected to 40 effective full power years (EFPY) for both units which is beyond the expiration date of both operating licenses.
Evaluation of Materials As ects Unit 1 The controlling beltline material from the standpoint of PTS susceptibility was identified to be the lower shell longitudinal welds 3-442A, B 8 C (weld wire heat No. 27204).
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The material properties of the controlling material and the associated margin and chemistry factor were reported to be:
Utilit Submittal Staff Evaluation Cu (copper content, Wt. X)
Ni (nickel content, Wt. X)
I (Initial RTN0T, 'F)
M (Margin, 'F)
CF (Chemistry Factor, 'F)
- 0. 21
- 0. 98 "56 59 0.23 0.98
-56 59 177. 0 The controlling material has been properly identified.
The justifications given for the copper and nickel contents are that these were measured on the surveillance
- weldment, which was made with the matching weld wire heat number
- 27204, using base metal trimmed from the proper beltline plates, and welded in the same time period.
The latter was confirmed by supplemental information furnished at the staff's request.
The surveillance weld was made in November 1967 and the lower shell longitudinal welds were made in February 1968.
It was also reported in the supplemental information provided, on August 7, 1986 that the chemistry values for the surveillance weld were the result of one measurement.
In Table 2 of the submittal dated January 17, 1986, six other measurements (the first six listed) are given for weld wire heat 27204 for samples taken from groove welds.
The staff has concluded that the average copper and nickel contents for the seven measurements (including the surveillance weld) represent the best estimates of the chemistry of the controlling beltline weld.
As indicated in the Table above, the value for nickel content remains unchanged, but the copper content becomes 0.23X instead of 0.21X.
With this change, the chemistry factor becomes 177.0.
Unit 2 The controlling beltline material from the standpoint of PTS susceptibility was identified to be in the intermediate shell plate B5454-2.
The material properties of the contro"l1ing material and the associated margin and chemistry factor were reported to be:
Utilit Submittal Staff Evaluation Cu (copper content, Wt. I)
Ni (nickel content, Wt. X)
I (initial RTN>T, 'F)
M (Mar gin, 'F)
CF (Chemistry factor, F)
- 0. 14
- 0. 59 67 48
- 0. 14
- 0. 59 67 48
- 84. 7 The controlling material has been properly identified.
The justifications given for the copper and nickel contents and the initial RTNpT are acceptable.
The margin has been derived from consideration of the bases for 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.
"3" Fluence Evaluation and Calculated RTPTS The following evaluation concerns the estimation of the fluence to the pressure vessel for 40 effective fu'll power years of operation and the corresponding value of the RTPTS.
The methodology of the fluence calculation was based on the discrete ordinates code DOT with an ENDF-B/IV based cross section set.
The scattering is treated with a P3 approximation, plant-specific sources were used and the code has been benchmarked by Westinghouse.
Unit 1 The lower shell longitudinal welds 3-422A, B, C were identified as the con-trolling material for Unit 1.
The peak axial fluence at the location of welds is the applicable value (Reference 3).
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 equation specified in 10 CFR 50.61 as applicable for the Diablo Canyon Unit 1 plant is:
RT S
= I+M+(-10+470xCu+350xCuxNi)xf
'TS where:
I = Initial RTNDT M = Uncertainty Margin Cu = w/o Copper in longitudinal welds 3-442A,B,C Ni = w/o Nickel in longitudinal welds 3-442A,B,C F
= Peak Fluence for 40 EFPY (E>1,0 MeV) longitudinal welds 3-442A,B,C in units of 10'gn/cm~
=-56F 59 F
= 0.23
= 0.98
= 2.9 Therefore:
RTPTS 56+59+(
10+470XO 23+350XO 23XO 98)x2 9
= 3+177. Oxl.333 = 238. 9 F
which is lower than 270 F, the applicable PTS rule screening criterion and is acceptable.
This value is for 40 effective full power years of operation, and is higher than the value of 217 F reported by the licensee for the reason explained above.
Unit 2 The intermediate shell plate B5454-2 was identified as the controlling material for Unit 2.
The peak azimuthal fluence at the intermediate shell plate is the applicable value (Reference 4).
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 equation Unit 2 plant where:
I M
Cu =
Ni =
f Therefore:
Initial RTNDT Uncertainty Margin w/o Copper in shell plate B5454-2 w/o Nickel in shell plate B5454-2 peak azimuthal fluence for 40 effective full power years (E> 1.0 MeV) intermediate shell plate B5454-2 in units of 10 n/cm 67 F
48 F
- 0. 14
- 0. 59 2.9 specified in 10 CFR 50.61 as applicable for the Diablo Canyon is the same as shown above for Unit 1, RT
= 67+48+(-10+470x0. 14+350x0. 14x0.59)x2.9
'TS
= 115+84.7lx1.333
= 227.9 F
which is lower than 270'F, the applicable PTS rule screening criteria and is acceptable.
This value is for 40 effective full-power years of operation.
Conclusion The values of RTPTS for the controlling beltline materials for Diablo Canyon Units 1 and 2 are 239 F and 228 F, respectively, based on 40 effective full power years of operation, which is beyond the expiration date of both operating licenses.
These values are less than the applicable screening criteria contained in 10 CFR 50. 61 and are therefore acceptable.
Thus, the requirements of the PTS Rule are satisfied.
In order for us to confirm the licensee's projected estimated RTPTS throughout the life of the licenses we will request the licensee to submit a re-evaluation of the RTPTS and comparison to the predicted value with future Pressure-Temperature submittals which are required by 10 CFR 50, Appendix G.
Date:
Principal Contributors:
P.
N. Randall L. Loi s C. Trammell
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References 1.
Letter from J.
D. Shiffer, Pacific Gas and Electric Company to S. Varga, NRR, dated January 17, 1986 (DCL-86-0006).
2.
Letter from J.
D. Shiffer, Pacific Gas and Electric Company to S. Varga, NRR, dated April 7, 1986 (DCL-86-092).
3.
WCAP-10878, "Diablo Canyon Unit 1 Flux Reduction Program for Reactor Vessel Integrity, Phase 1," S.
L. Anderson, et. al., Westinghouse Electric Corporation, dated October 1985.
4.
MCAP-10780, "Diablo Canyon Unit 2, Flux Reduction Program for Reactor Vessel Integrity, Phase 1,"
R.
L. Turner et al., Westinghouse Electric Corporation, dated October 1985.
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