ML18152A619
| ML18152A619 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 12/07/1987 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML18152A615 | List: |
| References | |
| NUDOCS 8712160074 | |
| Download: ML18152A619 (3) | |
Text
e UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 e
SURRY UNIT 1, SAFETY EVALUATION FOR FRACTURE TOUGHNESS REQUIREMENTS FOR PROTECTION AGAINST PRESSURIZED THERMAL SHOCK EVENTS (10 CFR 50.61)
INTRODUCTION By letter dated January 23, 1986, as supplemented November 26, 1986, December 12, 1986, and April 30, 1987, the Virginia Electric and Power Company (the licensee) submitted information on the material properties and the fast neutron fluence (E ~ 1.0 MeV) of the reactor pressure vessel in compliance with the requirements of 10 CFR 50.61.
The staff has reviewed these submittals to assure that the licensee has properly identified the controlling beltline material from the standpoint of pressurized thermal shock (PTS) susceptibility, and provided proper justifications for the copper and nickel contents and the initial RTNDT (RTNnT is a reference temperature as defined in 10 CFR 50.61).
Also, the staff u~~d this information in estimating the fluence to the pressure vessel at the end of 40 calendar years of operation and in calculating the corresponding value of RTPTS (RTQIS is a reference temperature for pressurized thermal shock as defined 1n 10 CtR 50.61) for assuring compliance with 10 CFR
- 50. 61.
EVALUATION The controlling beltline material from the standpoint of PTS susceptibility was identified to be the lower shell longitudinal weld, L2, weld wire heat number 299L44. *using the material properties of the controlling material submitted by the licensee and using the guidance provided in 10 CFR 50.61, the staff has included the following information in its evaluation of RTPTS" Cu (copper content, w/o) 0.35 Ni (nickel content, w/o) 0.67 I (Initial RTNDT' °F) 0 M (Uncertainty Margin as discussed in 10 CFR 50.61, °F) 59 The methodology of the fluence calculation was based on the discrete ordinates code, which is named Discrete Ordinates Transport (DOT), with an ENDF/B-IV based cross-section set.
The scattering is treated with a P approximation and plant-specific sources were used.
The power distributfon for operating cycle 8 was used for the extrapolation to the end of the 40 calendar years of opera-tion.
The power uprating from 2441 MWt to 2546 MWt in cycle 11 has also been taken into account.
The code has been benchmarked by Westinghouse.
Its predictions for the surveillance capsule locations are within +/-15% of the measured values.
An S angular quadrature was used.
The lower shell longi-tudinal weld, 12, has Been identified as the controlling material.
The weld, L2, is at an azTmuthal location of -45° (315°).
r 8712160074 871207 PDR ADOCi<. 05000280
. p PDR I
I The fluence for this location was estimated for 40 calendar years of operation.
The fluence estimate is based on the licensee's estimated 28.8 effective full power years of operation during 40 years of operation.
The value of the peak axial fluence at this azimuthal location for 401§alend~r years of operation for neutrons with energies E~l.O MeV is 0.639 x 10 n/cm.
This value is used in the following equation specified in 10 CFR 50.61 as applicable for the Surry Unit 1.
The fluence estimate is conservative.
The ~ethodology, the cross-sections and the approximations used by licensee are acceptable.
RTPTS where:
Therefore:
RTPTS
= I+M+(-10+470 x Cu+350 x Cu x Ni) x f0* 27 I = Initial RTNDT M = Uncertainty Margin Cu= w/o copper in longitudinal weld L2 Ni= w/o nickel in longitudinal
= 0°F
= 59°F
= 0.35 weld L2
= 0.67 f = Peak axial fluence (E~l.O MeV) on longitudinal weld L2 for 40 calendar years of operation, in units of 1019n/cm2
= 0.639
= 59+(-10+470 X 0.35+350 X 0.35 X 0.67) X (0.639)0* 27
.* = 268. 6°F Thus, the estimated RTPTS is lower than the applicable PTS rule screening criterion of 270°F for ongitudinal welds.
CONCLUSION Based on above evaluation, the staff concludes that the licensee has properly identified the controlling beltline material from the standpoint of the PTS rule and provided proper justification for the material and initial RTNBT*
Also, the staff finds that the Surry Unit 1 pressure vessel meets the t ughness requirements of 10 CFR 50.61 for 40 calendar years of operation.
In view of:
(a) the pressure-temperature updating requirements for the fracture toughness of the beltline material in 10 CFR 50 Appendix G, and (b) the fact that the RTPTS value is readily available from the calculation of the pressure-tempetature limits, and
e (c) the staff desire to be informed on the current value of the RTPTS for all
- PWRs, we request that the licensee submit a reevaluation of the RTPTS and a compari-son to the prediction of the original submittal along with the future pressure-temperature operating limits which are required by 10 CFR 50 Appendix G.
It should be noted that this reevaluation is a requirement of 10 CFR 50.61 whenever core loadings, surveillance measurements, or other information indicate a significant change in projected values.
Dated:
December 7, 1987 Principal Contributors:
L. Lois P. N. Randall