ML20150C265

Safety Evaluation Supporting Licensee Assessment to Fracture Toughness Requirements for Protection Against PTS Events,Per 10CFR50.61

ML20150C265
Person / Time
Site:	Catawba
Issue date:	06/28/1988
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20150C251	List: ML20150C248 ML20150C261 ML20150C265
References
NUDOCS 8807120388
Download: ML20150C265 (3)

Text

.

1. f ro g 'g

~ UNITED STATES

!" o NUCLEAR REGULATORY COMMISSION

{ $ WASHINGTON, D. C. 20555

\...../

ENCLOSURE 2 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FRACTURE TOUGHNESS REQUIREMENTS FOR PROTECTION AGAINST I PRESSURIZED THERMAL SH0CK EVENTS (10 CFR 50.61) I 1

, DUKE POWER COMPANY, ET AL.

CATAWBA NUCLEAR STATION, UNIT 2 DOCKET NO. 50-414

1.0 INTRODUCTION

In accordance with 10 CFR Part 50.61(b)(1), each pressurized water reactor licensee shall have submitted an assessment of the pressure vessel reference i temperature by January 23, 1986. This assessment of the reference temperature l at the inner surface of the reactor vessel beltline materials is projected j from the time of submittal to the expiration of the license. The assessment  ;

must specify the bases for the projection and the assumptions regarding core '

loading patterns. It must be updated whenever changes in core loadings, surveillance measurements, or other information indicate a significant change in projected reference temperature values.

2.0 EVALUATION l l

By letters dated October 1, 1985, and November 11, 1986, Duke Power Company, et I al., (the licensee) submitted information for Catawba Unit 2 on the material  ;

properties and the fast neutron fluence (E greater than or equal to 1.0 MeV) of l the reactor pressure vessel in compliance with the requirements of 10 CFR 50.61  ;

(See References 1 and 2).

2.1 Material Properties The controlling beltline material from the standpoint of PTS susceptibility was identified by the 'icensee to be the intermediate shell plate 88605-2. The material properties of the controlling material and the associated margin and chemistry factor were reported by the licensee to be:

Licensee Submittal Staff Evaluation Cu(coppercontent,%) 0.07 0.07 Ni (nickel content, %) 0.61 0.61 I (Initial RT NDT, F) 33 33 M(Margin,'F) _

48 CF (Chemistry Factor *F) _

37.8 8807120388 880628 PDR ADOCK 05000413

. P PDR

4 2-The results of the staff's evaluation are given in the second column above.

The controlling material has been properly identified. The justifications given for the copper and nickel contents and the initial reference temperature (RTNDT), as defined in the ASME Ccde, Paragraph NB-2331, are acceptable.

The margin has been derived frcm consideration of the bases for these values, following the PTS rule (10 CFR Part 50.61). Based on the reported values of fluence, Equation 1 of the PTS rule governs and the chemistry factor is as shown in the above table.

2.2 Fast Neutron Fluence The following evaluation concerns the estimation of the fluence to the pressure vessel for 32 effective full power years of operation and the equations in 10 CFR Part 50.61(b)(2). The 32 effective full power years represent a 40-year design life based on an 80 percent capacity factor.

The fluence calculation was based on the 00T computer code, but used the P approximation and an ENDF/B-II based cross section set (Reference 2). No 1 statement is made on other aspects of the computation such as quadrature approximation, source distribution, reload strategy, etc. It is possible that the peak fluence might be underestimated by as much as 50%. However, as shown i above the available margin is much greater. Hence, the staff finds that the l proposed RT value is acceptable, subject to the condition that a revision of the peak flN$ce estimation methodology (E greater than or equal to 1.0 MeV) for 32 effective full power years of operation on intermediate shell plate )

88605-2 will be carried out. This revision should be performed with a i benchm6rked version of the D0T code and as a minimum: (a) use a P  !

cross section approximation, (b) use an S g quadratureapproximatio$, scattering (c) use an ENDF/8-IVbasedcrosssectionset}s(d)useapinwisesourcedistributionfor the peripheral assemblies, and (e hould account for future reload strategies.

The applicable equation specified in 10 CFR 50.61(b)(2) for the pressure vessel PTS reference temperature (RTPTS) f r Catawba Unit 2 reactor is the following:

RT 0

PTS = !+M+(-10+470xCu+350xCuxNi)xf .27 Where: I = Initial RT NDT = 33*F M = Uncertainty Margin = 48'F l Cu = w/o Copper in intermediate plate B8605-2 = 0.07 l Ni = w/o Nickel in intermediate plate B8605-2 = 0.61 f = Peak Azimuthal Fluence for 32 EFPY (E greater than or equal to 1.0 MeV) on intermediate plate B8605-2 in units of 19 2 10 n/cm = 2.01

-_ _ _ -. -_ __-_._i-__.-..____ , _ _ _ . -

.i Therefore, for 32 effective full power years of operation, the PTS reference temperature is:

0 RT PTS = 33+48+(-10+470x0.07+350x0.07x0.61)x2.1 27

= 81+48.85x1.222=81+46.2=127.2*F This value is considerably lower than 270*F which is the applicable PTS rule screening criterion in 10 CFR Part 50.61 (b)(2) and, therefore, the projected PTS reference temperature for Unit 2 is acceptable.

3.0 Conclusion that the pressure vessel PTS reference The staff concludes, temperature based defined in 10 on the CFR Part 50.61above,(b)(2) is less than the applicable PTS screening criterion. Because the PTS reference temperature is projected to be within the screening criterion through the expiration of the Unit 1 license, the licensee does not have to address 10 CFR Part 50.61(b)(3). In accordance with 10 CFR 50.61(b)(1), the staff requests that the licensee submit an update to the information provided ir its letters dated October 1, 1985, and November 11, 1986, whenever changes in core loadings, surveillance measurements, or other information indicate a significant change in projected reference temperature values.

4.0 References

1. Letter from W. H. Owen, Duke Power Company to H. R. Denton NRR, dated October 1, 1985.

2. Letter from H. B. Tucker, Duke Power Company to H. R. Denton, NRR, dated November 11, 1986.

Principal Contributors: L. Lois, P. N. Randall Dated:

l 1

l l

l l

_