ML20140D142

Forwards Supplemental RAI Re Resolution of Unresolved Safety Issue A-46.Written Response Requested to Be Provided within 30 Days of Receipt of Ltr

ML20140D142
Person / Time
Site:	Fort Calhoun
Issue date:	06/05/1997
From:	Wharton L NRC (Affiliation Not Assigned)
To:	Gambhir S OMAHA PUBLIC POWER DISTRICT
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR TAC-M69447, NUDOCS 9706100266
Download: ML20140D142 (4)

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June 5,1997 Mr. S. K. Gambhir Division Manager - Production Engineering Omaha Public Power District Fort Calhoun Station FC-2-4 Adm.

Post Office Box 399 Hwy. 75 - North of Fort Calhoun Fort Calhoun. Nebraska 68023-0399

SUBJECT:

FORT CALHOUN STATION UNIT NO. 1 - SUPPLEMENTAL REQUEST FOR ADDITIONAL INFORMATION ON THE RESOLUTION OF UNRESOLVED SAFETY ISSUE i A-46 (TAC NO. M69447)

Dear Mr. Gambhir:

l By letter dated August 23, 1996, the Omaha Public Power District provided its response to the staff's request for additional information (RAI). dated June 21. 1996. The RAI requested information on the plant-specific sun. nary j report addressing the resolution of unresolved safety issue (USI) A-46 program at the Fort Calhoun Station.

The staff has reviewed your response and determined that further supplemental information is necessary to complete its review of your USI A-46 response. We have enclosed the supplemental request- for additional information. l Please provide written responses to the enclosed questions within 30 days of receipt of this letter.

Sincerely.

Original Signed B L. Raynard Wharton,yProject Manager -

Project Directorate IV-2 Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation l Docket No. 50-285 DISTRIBUTION:

Docket File RWessman

Enclosure:

Supplemental Request for PUBLIC LHurley, RIV Additional Information PDIV-2 Reading ACRS. T2E26  ;

JRoe OGC. 015B18 i cc w/ encl: See next page EGA1 WJohnson, RIV )

WBateman KManoly i RWharton JKilcrease. RIV EPeyton PGwynn. RIV f I

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DOCUMENT NAME: FC69447.RAI OFC PDIV-2/PM PDIV-2/LA b I NAME RWharton EP57tN DATE lo /5 /97 G/4 /97 {jg{g((g]iQ{py 0FFICIAL RECORD COPY l

9706100266 970605

} PDR ADOCK 05000285 P PDR l

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• Mr. 5. K. Gambhir June 5, 1997 cc w/ encl:

Winston & Strawn ATTN: Perry D. Robinson. Esq.

1400 L Street. N.W.

Washington, DC 20005-3502 Mr. Jack Jensen. Chairman Washington County Board of Su Blair. pervisors Nebraska 68008 Mr. Wayne Walker. Resident Inspector U.S. Nuclear Regulatory Commission Post Office Box 309 Fort Calhoun. Nebraska 68023 Regional Administrator. Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive. Suite 1000 Arlington. Texas 76011 Ms. Cheryl Rodgers..LLRW Program Manager Environmental Protection Section Nebraska Department of Health 301 Centennial Mall. South P.O. Box 95007 Lincoln. Nebraska 68509-5007 Mr. James W. Chase. Manager Fort Calhoun Station Post Office Box 399 Fort Calhoun. Nebraska 68023 Mr. James W. Tills Manager - Nuclear Licensing Omaha Public Power District Fort Calhoun Station FC-2-4 Adm.

Post Office Box 399 Hwy. 75 - North of Fort Calhoun Fort Calhoun. Nebraska 68023-0399

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SUPPLEMENTAL REQUEST FOR ADDITIONAL INFORMATION OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION. UNIT NO. 1 DOCKET NO. 50-285

1. In reference to Attachment 4 of your submittal LIC-96-0121. Calculation No. FC06313. please note the following:

a. The nominal allowable capacities of the cast-in-place anchor bolts should be determined in accordance with Section C3 of the GIP.

Appendix C. In the computation of allowable tension "P" for cast-in-) lace anchor on sheet 14 of 37 (Calculation No. FC06313) an anclor is considered as a plain top rebar in a beam. This representation is not conservative since a rebar, most likely will be much longer than an anchor and the end of the rebar is embeddeo in the compression zone of the beam. Therefore, you are requested to provide a justification for the use of higher tensile allowables than those specified in Appendix C of the GIP for cast-in-place  ;

anchors. or revise your computation in conformance with the GIP '

provision. l l

b. The shear-tension interaction analysis on sheet 15 of 37 does not '

a) pear to be valid for the pedestal which is under tension and slear. because under such a condition, either the concrete or the shear reinforcement, not both can be considered to resist the shear.

Therefore, your computation of allowable shear "V" should be justified or revised, as discussed in item 1.a above.

c. As a result of revised allowable values of "P" and "V" your shear-tension interaction analysis on sheets 26 and 32 of 37 should also be reassessed.

d. The )roposed modification as shown on sheet 37 of 37 (Calculation No. C06313) is not clear and the location of the modification in relation to the saddle and the tank as a whole, should be clearly identified. ,

2. In the com)utation for USI A-46 Outlier Resolution for Heat Exchanger CH-7, you lave not followed Appendix C of the GIP to calculate the bolt  ;

capacities on the basis of the embedment length check and edge distance check and have used the anchorage requirement of a plain top bar in a beam to determine the bolt capacities. As indicated in 1. above, such an approach results in overestimation of bolt ca)acities and is, therefore, unacceptable. We request a re-evaluation of >olt capabilities for this equipment using the approved methodology in Appendix C of the GIP. I l

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3. In the calculation for seismic qualification of the diesel fuel tanks, discussed in Calculation No. FC06011. the theoretical buckling stress is shown to be 76'.150 psi which is more than twice the yield stress of

'30.000 psi of the steel used. Therefore, the buckling is in the plastic

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range and hence. the analysis should be made on this basis. You calculated the buckling stress by using the formula in ASME Code Case 284. In accordance with Code Case 284, the formula you used is for local buckling of unstiffened.or ring stiffened cylindrical shells under axial compression. Since the diesel fuel tank is buried, it is under both axial compression and hoop compression and the concern is general stability. Therefore. Code Case 284 is not applicable for the required evaluation. The basic allowable buckling stress values should be established on the basis of NE-3131(b). NE-3133 and NE-3222 or other applicable criteria.

On the basis of above observation, we request a re-evaluation of the seismic capability of the diesel fuel tanks.

4. In the evaluation of the seismic resistance of concrete block walls, you have idealized the sortion of the wall between Wall No.10 and row line 0 as one way slab wit 1 single span and simple support in the horizontal direction. On the basis of such an idealization, you have calculated the seismic bending moment and the corresponding bending stress (21.2 asi) i which can be tensile or compressive. This stress is compared to t1e  !

allowable value (f,)4 which is taken as 50 p.si. According to Table 10.1 in ACI 531-79 code, the allowable stress for tension normal-to-bed joints is 25 psi. With the idealization of the layer of block wall as a beam, the flexural tension force is normal to the vertical bed joint. A close examination of your calculation for the moment of inertia of the idealized beam section, would indicate the calculated moment of inertia to be for a section of a beam spanned between supports in the vertical direction. On this basis you are requested to re-evaluate the bending stresses in the wall against the corresponding allowable, or provide a justification for the apparent discrepancy in the block wall seismic  !

evaluation. i l

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