ML18152A620
| ML18152A620 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 12/07/1987 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML18152A615 | List: |
| References | |
| NUDOCS 8712160096 | |
| Download: ML18152A620 (3) | |
Text
e UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 e
SURRY UNIT 2, 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 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 justifi-cations for the copper and nickel contents and the initial RTN (RT is a reference temperature as defined in 10 CFR 50.61).
Also, the Rtaff ~~id 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 RT~Ts (RTPTS is a reference temperature for pressurized thermal shock as def ned ih IO CFR 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 welds, Ll and L2, weld wire heat number 8Tl762.
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 RTPTS" Cu (copper content, w/o) 0.29 Ni (nickel content, w/o) 0.55 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, 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 distributi~n for operating cycle 8 was used for the extrapolation to the end of the 40 calendar years of operation.
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 longitudinal welds, L and L,, Rave been identified as the controlling material; therefore, the appltcable value of the fluence is the axial peak at the weld.
The fluence for this 1
8712160096 871207.. ~
I PDR ADOCK 05000280 I
p PDR location was estimated for 40 calendar years of operation.
The fluence esti-mate is based on the licensee 1s estimated 29.4 effective full power years of operation during 40 calendar year of operation.
The value of peak fluence at welds L13 and2L2 for 40 years of operation is estimated to be 0.714 x 10 n/cm.
The fluence estimate is conservative.
Future low leakage core loadings were assumed.
The methodology, the cross-sections and the approximations used by licensee are acceptable.
The equation specified in 10 CFR 50.61, as applicable for the Surry Unit 2 is:
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 the lower shell longitudinal weld L1,L2 Ni= w/o nickel in longitudinal weld Ll'L2
= 0°F
= 59°F
= 0.29
= 0.55 f = Peak Fl uence (E ~ 1. 0 MeV) on 1 ower shell longitudinal weld L1,L2 in units of 1019n/cm2
= 0.714
= 59+(-10+470 X 0.29+350 X 0.29 X 0.55) X (0.714)0* 27
= 225°F Thus, the estimated RTPTS is lower than the applicable PTS rule screening criterion of 270°F.
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 ihitial RTNBT" Also, the staff finds that the Surry Unit 2 pressure vessel meets the t ughness requirements for 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 Appenpix G, and *
(b) the fact that the RTPTS value is readily available from the calculation of the pressure-temperature limits, and (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 RT and a compari-son to the prediction of original submittal along with the f~tare pressure-temperature operating limits which are required by 10 CFR 50 Appendix G.
It should be noted that this reevaluation is a requirement by 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. Randa 11