ML20211M416

Safety Evalution Supporting Licensee 860123 Submittals Re Fast Neutron Fluence for Fracture Toughness Requirements for Protection Against PTS Events (10CFR50.61)

ML20211M416
Person / Time
Site:	Summer
Issue date:	12/09/1986
From:	NRC
To:
Shared Package
ML20211M384	List: ML20211M381 ML20211M416
References
REF-GTECI-A-49, REF-GTECI-RV, TASK-A-49, TASK-OR NUDOCS 8612170246
Download: ML20211M416 (3)

Text

_ _ _ _

Enclosure VIRGIL SUMMER, FAST NEUTRON FLUENCE FOR FRACTURE TOUGHNESS REQUIREMENTS FOR PROTECTION AGAINST PRESSURIZED THERMAL SHOCK EVENTS (10 CFR 50.61)

By letter dated January 23, 1986, the South Carolina Electric and Gas Company, the licensee for the Virgil Summer plant, 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 (Reference 1).

We have reviewed the pressure vessel material properties and find them acceptable (Reference 2). The following evaluation concerns the estimation of the fluence

{

to the pressure vessel until the end of the current license and the corresponding I value of the RT PTS' The methodology of the fluence calculation was based on the discrete ordinates code 00T with SAILOR an ENDF/8-IV based cross section set. The scattering is treated with a P 3approximation. The Code has been benchmarked by Westinghouse.

Design values of the neutron sources were used for cycles 1-3. Cycles 2 and 3 sources (low leakage loading) were used for the extrapolation of the exposure to the end of the operating license (October 22, 2022) when the reactor will accumulate 35.14 effective full power years of operation with an 90% load factor. The intermediate lower shell plate A9154-1 has been identified as the controlling material, therefore, the applicable value of the fluence for the estimation of the RTPTS is the peak of the azimuthal distribution. The methodology, the cross sections and the approximations used are acceptable.

The equation specified in 10 CFR 50.61, as applicable for the Virgil Summer plant is:

8612170246 861209 DR ADCCK 05 35

~

0 RTPTS = I+M+(-10+470 x Cu+350 x Cu x Ni) x f .27 J

where: I = Initial RT NDT = 30 F M = Uncertainty Margin = 48 F Cu = w/o Copper in intermediate shell plate A9154-1 = 0.10 Ni = w/o Nickel in intermediate shell plate A9154-1 = 0.51 f = Peak Azimuthal Fluence (E 1.0 MeV) intermediate shell plate A9154-1 in units of 10 19 n/cm2 = 4.78 Therefore, for 35.14 effective full power years:

0 RTPTS = 30+48+(-10+470 x 0.10+350 x 0.10 x 0.51) x 4.78 27

= 78+54.8 x 1.526 = 161.6*F which is lower than 270 F the applicable PTS rule screening criterion and is acceptable. It should be noted that the above fluence represents about 4.6% of the fluence required to reach the PTS screening criteria.

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 RT PTS 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 RT PTS for all PWRs, we request that the licensee submit a re evaluation of the RT and a PTS comparison to the prediction of Reference 1 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 by 10 CFR 50.61, whenever core loading, surveillance measurements, or other information indicate a significant change in projected values.

• This request for information is covered under OMB clearance No. 3150-0011.

A

r=

REFERENCES

'1. Letter from D. A. Nauman, South Carolina Electric and Gas Company to Director NRR dated January 23, 1986 and attachment WCAP-10998 Rev. I dated December 1985.

2. Memorandum from R. Ballard to J. Hopkins, " Virgil Summer, Material Properties for Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events 10 CFR 50.61," dated October 21, 1986.

l