ML20216F765

Provides Response to Address Questions Submitted by 970417 RAI Re Alternatives to Examination Requirements of 10CFR50.55a(g)(6)(ii)(A).W/three Oversize Drawings

ML20216F765
Person / Time
Site:	Catawba
Issue date:	09/02/1997
From:	Gordon Peterson DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20216F769	List: ML20216F765 ML20266A471 ML20266A475 ML20266A479
References
TAC-M98040, TAC-M98041, NUDOCS 9709120093
Download: ML20216F765 (9)

Text

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• W Catawba Nwlear Station 4800 Concord Road York. SC 29745 Gary R. Petermn (803) 831-425I omCE Yuce 1%ident (803) 8313426nx I

September 2, 1997 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001

Subject:

Duke Energy Corporation j Catawba Nuclear Station,

[ Unit 1 and Unit 2 i

Docket Nos. 50-413 and 50-414 Request for Additional Information Alternatives to Examination Requirements of 10 CFR 50.55a (g) (6) (iii ( A) ,

Augmented Examination of Reactor Vessel Unit 1. No. 97-01, Unit 2, No. 97-02 TAC Nos. M98040 and M98041 Re: Letter from NRC to William R. McCollum dated April 17, 1997, Alternatives to Reactor Vessel Augmented Examination Request The following response is provided to address the questions submitted by the subject Request for Additional Information Each question is restated below with the response following.

(1) Discuss the feasibility of examining each weld specified in Item B1.10 of Examination Category B-A from the outside surface of the vessel.

Response: In Unit 1, the Nozzle Belt -to- Shell Weld (Item Number B01.011.004, ID Number 1RPV-WO6) "

is totally inaccessible from the outside !O surface of the reactor vessel due to insufficient clearance between the reactor //

vessel wall and concrete encasement. //

In Unit 2, the Longitudinal Welds (Item Number B01.012.007, ID Number 2RPV-101-142A; 9709120093 970902 "

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O Document Control Desk Page 2 September 2, 1997 Item Number B01.012.008. 2RPV-101-142B; and Item Number B01.012.009, 2RPV-101-142C) are totally inaccessible from the outside surface of the reactor vessel due to insufficient clearance between the reactor vessel wall and concrete encasement.

Removing a sufficient amount of the concrete encasement to perform the examination of these welds would create a hardship on Duke Energy Corporation.

Examination of the Lower Head -to- Shell Weld in Units 1 and 2 (Item Number B01.011.001, ID Number 1RPV-WO3 and Item Number B01.011.001, ID Number 2RPV-101-141) from the outside surface of the reactor vessel would create an j undue hardship on Duke Energy Corporation due to the following reasons:

• There is less than 180 degrees of the cutside surface of the weld exposed (less than 25 percent of the examination volume)

• Examination of these welds from the outside surface has never been performed and weld prep work of approximately 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> would therefore be required.

Exmaination time would be approximately 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> I

• The weld is located in a high radiation area, with readings being approximately 300 mr/hr on contact and 100 mr/hr general area Any minimal increase in examination coverage and the  !

significant additional radiation exposure that would be  ;

incurred would not warrant the effort required to examine the accessible weld length from the outside surface.

Reference attachments 1(CN-1041-8), 2(CN-1041-1) and 3 (CN-1041-12')

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' Document Control Desk Page-3 September 2, 1997 (2) Provide dimensions of the largest indication (planar and/or linear) in the unexmained volume of each of the above welds found during the preservice inspection.

f Response: There were no recorded flaw indications in the subject welds during preservice inspection.

(3) Confirm that the peak neutron fluence at the end of the inspection interval for the shell to nozzle belt weld and 3the lower head to shell weld will not exceed 10" n/cm (E > 1 MeV) based on the test results of surveillance specimens or estimated analytically.

Response: Catawba Nuclear Station (CNS) Units 1 and 2 lower head to shell welds will have ac a peak neutron fluence well below 10" quired n/cm 2 at the end of the inspection interval. Stan Anderson (Westinghouse) has provided this information to William Brady (Duke Energy Company) in the attached note ( Attachment 4) dated August 21, 1997 based on fluence -

calculations performed internally by Westinghouse. Furthermore, Westinghouse estimates the CNS Units 1 and 2 lower head to shell welas will not have cccumulated a peak neutron fluence of 10" n/cm2 by the end of life (32 EFPY). CNS Units 1 and 2 shell to nozzle belt welds are not as easily estimated to have ac below 10" quired n/cm 2 bypeak the neutron fluence end of the values inspection interval; therefore, RAI #4 response will address these two welds.

I i

Document Control Desk Page 4 a September 2,-1997 l

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(4)' If the neutron fluence exceeds 10" n/ca (E > 1 MeV),

provide the adjusted reference nil ductility transition '

temperature at the end of the inspection interval for the welds and the heat-affected zones, which could not  !

be examined for 90 percent of the volume, by using the methodology of regulatory Guide 1.99, Revision 2.

i Response: CNS Unit 1 shell to nozzle belt circumferential weld is heat number 899680 and is composed of 0.03% Cu and 0.75% Ni.

The most limiting weld for CNS Unit 1 is the circumferential weld located slightly below

. the core centerline and is heat number 895075 with chemical compositions of 0.039% Cu and 0.724% Ni. Chemical composition values are obtained from the EPRI RPVDATA database. It is observed that the two welds possess virtually identical chemical properties with the shell to nozzle belt weld having a slightly lower copper content and a slightly

, higher nickel content. However, the circumferential weld 1 ated at approximately

, the core midplane receives a substantially-higher neutron fluence since the shell to

, nozzle belt weld lies outside the beltline region of the reactor pressure vessel.

Based on the similar chemical compositions of

, the two welds and the fact that the neutron fluence received by the beltline

, circumferential weld is significantly higher

than the shell to nozzle belt weld, the reference nil ductility transition temperature (RTmn) of the beltline circumferential weld will bound the shell to nozzle belt RTmg value. WCAP-13720 entitled,

" Analysis of Capsule Y from the Duke Power Company Catawba Unit 1 Reactor Vessel Radiation Surveillance Program", dated June,

-1993 lists the RTmn value of the circumferential beltline weld in Table B-2.

The RTmn value is calculated for a 15 EFPY neutron fluence.value and is 6SCF and 330F for-1/4t and 3/4t, respectively.

Document Control Desk Page 5 September 2, 1997 These RTmn values are further reduced based on chemistry factors calculated using surveillance capsule data. The RTmn values are -300F and -360F for 1/4t and 3/4t, respectively. The shell to nozzle belt weld and heat affected zone RTmn values will easily be bounded by the beltline circumferential weld RTmn values given above.

CNS Unit 2 shell to nozzle belt circumferential weld is heat number SP5622 and is predicted to have a 32 EFPY or end of life (EOL) accumulated neutron fluence of only 7. 3 8 x 10" n/cm' . The most limiting circumferential weld for CNS Unit 2 is the circumferentin' weld located slightly below the core centerline and is heat number 83648 with a predicted EOL neutron fluence of 2.46 M 2 x 10 n/cm. Neutron EOL fluence values are obtained from the EPRI RPVDATA database. It is observed that the two welds have different l chemical properties with the shell to nozzle belt weld having a higher copper content and a lower nickel content. However, the circumferential weld located at approximately the core midplane receives a substantially higher neutron fluence since the shell to nozzle belt weld lies outside the beltline region of the reactor pressure vessel. Based on the fact that the neutron fluence received by the beltline circumferential weld is significantly higher than the shell to nozzle belt weld, the reference nil ductility transition temperature'(RTmn) of the beltline circumferential weld will bound the shell to nozzle belt RTmn value. WCAP-13875 entitled,

" Analysis of Capsule X from the Duke Power Company Catawba Unit 2 Reactor Vessel Radiation Surveillance Program", dated February, 1994 lists the RTun value of the circumferential beltline weld in Table B-3.

The RTmn value is calculated for a 15 EFPY neutron fluence value and is -8.3 F and

-30.50F for 1/4t and 3/4t, respectively.

f

Document Control Desk Page 6 September 2, 1997 '

These RTmg values are further reduced based on chemistry factors calculated using surveillance cspsule data. The RTmn values are -39.00F and -51.70F for 1/4t and 3/4t, respectively. The shell to nozzle belt weld and heat affected zone RTmn values will easily be bounded by the beltline circumferential weld RTmg values given above.

Based on the logic presented in the previous two paragraphs it is Duke Energy Company's recommendation that the NRC staff utilize the beltline circumferential weld RTmn values from the referenced WCAP documents to conservatively represent the CNS Units 1 and 2 snell to nozzle belt weld and heat affected zone RTmn values.

Should there be any questions concerning this request, please call D. Tower at (803) 831-3419.

Very truly yours a

Cary R. Peterson Attachments xc (letter only):

L.A. Reyes, Regional Administrator Region II Senior Resident Inspector Catawba Nuclear Station w/ attachment:

P.S. Tam, Senior Project Manager ONRR

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