ML20235V989

Forwards Request for Addl Info on Elimination of Postulated Primary Loop Pipe Ruptures as Design Basis,Per Util 861106 Request for Amends to Licenses NPF-4 & NPF-7.Identify Welding Process of Primary Loop & If Annealing Performed

ML20235V989
Person / Time
Site:	North Anna
Issue date:	07/17/1987
From:	Engle L Office of Nuclear Reactor Regulation
To:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
References
TAC-63577, TAC-63578, NUDOCS 8707230384
Download: ML20235V989 (4)

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,$1 July 17,1987 s,

Docket Nos. 50-338 DISTRIBUTION and 50-339 dDocketJile? OGC-Bethesda NRC PDR E. Jordan Local PDR J. Partlow PD22 Rdg. ACRS (10)

Mr. W. L. Stewart S. Varga Gray File Vice President - Nuclear Operations G. Lainas Virginia Electric and Power Company D. Miller Post Office Box 26666 L. Engle j Richmond, Virginia 23261  !

Dear Mr. Stewart:

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SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON ELIMINATION OF DYNAMIC EFFECTS 0F POSTULATED PRIMARY LOOP PIPE RUPTURES FROM DESIGN BASIS FOR NORTH ANNA POWER STATION UNITS 1 AND 2 (NA-1&2) (TAC NOS. 63577 AND 63578)

By letter dated November 6, 1986, Virginia Electric and Power Company (VEPC0) ,

requested an amendment to Facility Operating License Nos. NPF-4 and NPF-7 {

for NA-182, respectively. The proposed amendment would permit the redesign  ;

of the reactor coolant pump and steam generator supports, because the dynamic i effects of postulated primary loop pipe ruptures would be eliminated from the  !

design basis using " leak-before-break" technology as permitted by the revised l General Design Criterion 4 (GDC-4) of Appendix A,10 CFR 50. '

VEPC0 submitted the technical basis for the elimination of primary loop pipe ruptures for NA-1&2 in report WCAP-11163. The staff has reviewed the licensee's ,

submittal for compliance with the revised GDC-4. The staff has prepared the i enclosed request for additional information and is also available to discuss this request with VEPCO. 1 The reporting and/or recordkeeping requirements of this letter affect fewer  !

than 10 respondents; therefore, OMB clearance is not required under P.L.96-511.

Sincerely, Leon B. Engle, Project Manager l Project Directorate II-2 Division of Reactor Projects-I/II

Enclosure:

As stated cc: See next page

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R Mr. W. L. Stewart North Anna Power Station l Virginia Electric & Power Company Units 1 and 2 cc:

Richard M. Foster, Esq. Atomic Safety and Licensing Appeal Cockrell, Quinn & Creighton Board Panel 516 Cherry Tower U.S. Nuclear Regulatory Commission 920 South Cherry Street Washington, DC 20555 i Denver, Colorado 80222 l Regional Administrator, Region II l

Michael W. Maupin, Esq. U.S. Nuclear Regulatory Commission Hunton, Williams, Gay and Gibson Office of Executive Director P. O. Box 1535 for Operations R}rhmond, Virginia 23212 101 Marietta Street N.W., Suite 2900 Atlanta, Georgia 30323 Mr. W. T. Lough Virginia Corporation Commission Mr. E. W. Harrell Division of Energy Regulation P. O. Box 402 P.~0. Box 1197 Mineral, Virginia 23117 Richmond, Virginia 23209 Old Dominion Electric Cooperative Ellyn R. We iss, Esq. c/o Executive Vice President Harmon, Weiss and Jordan Innsbrook Corporate Center 2001 S Street NW 4222 Cox Road, Suite 102 Washington, DC 20009 Glen Allen, Virginia 23060 Mr.' J. T. Rhodes Mr. William C. Porter, Jr.

Senior Vice President - Power Ops. County Administrator Virginia Electric and Power Co. Louisa County Post Office Box 26666 P. O. Box 160 Richmond, Virginia 23261 Louisa, Virginia 23093 Mr. Patrick A. O' Hare James B. Kenley, M.D., Commissioner Office of the Attorney General Department of Health Supreme Court Building 109 Governor Street 101 North 8th Street Richmond, Virginia 23219 l Richmond, Virginia 23219 Resident Inspector / North Anna c/o U.S. NRC Senior Resident Inspector Route 2, Box 78 Mineral, Virginia 23117

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ENCLOSURE

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-(. REQUEST FOR ADDIT 10NAL INFORMATION

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((  ; AS A DESIGN BASIS

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,. VIRGINIA ELECTRIC AND POWER COMPANY , )

, ,' NORTH ANNrl S WER STATION UNITS 1 AND 2 L DOCKET WOS. 50-338 & 50-339

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) (1) The primary loop piping and fittings were fabricated from cast stainless

}r steel. Describe whether the piping and fittings are centrifugal % cast 1 stainless steel or statically cast stainless steel.. Also, identM the f < ( welding process of the primary loop and indicate 11'solutiok annes) ling

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was performed. ,

5 (2) The material properties were presented.in Tables 3-I t$$ough@3 in n.

g WCAP-11163. Describetwhether the propertfes are plant specific dataf* rom certified material test reports (CMTRs) cir Section III Code-minimut I

' values at joom temperature or operatirg timperdture. Provide the dlastic I modulus, yield strength, ultimate strengtd,VapC thuss-strain curve at f the lietting locatiBn v)d at the operading tes,perature. '

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,y , r n  % f (3) It appeari'thth the'same strdrs-strain" relationship was use&in the fracture stability and. leakage calculations._The licensee should use the i lower-bound stress-strain relationship for the stability _ evaluation and

• the derage st(ess-strain relationship for the leakage evaluation, sy -

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was used for the fracture i (4)Lberelasticfracturemechanics(LEFM)diculated"J"gp",itap

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' stability (N hsis. However, from the e the associated Irwin plane-stress plastic zone tizes e not small a j

i compared with the half-crack length "a". The licensee should use s  !

r elastic-plastic fracture mechanics instead of LEFM procedures.

. (5) Limit load analysis was used to estimate the size of a stable crack.

/However IMit lord analysis does not account for material toughness h mitations. In particular, low toughness themally-aged cast stainless ,

steel is involved in the present evaluation. The licensee should use a '

fracture stabilityJanalysis which accounts for material toughness.

,. o (6)Lo$t critical and toughnt;ss critical locations were discussed. However, the leak-before break (LBB) evaluation margins should be demonstrated for l the limiting lo"stion having the least fannble combinati6n of strcss<

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l and material properties. The limiting location may be defined from a fracture stability evaluation of the load critical and toughness critical locations. Since the primary loop piping is of a similar size, the location with the smallest stable crack size (independent of leakage) is the limiting location for LBB evaluations.

(7) The limiting location as discussed in item (6) above should be evaluated to demonstrate that the LBB margins are satisfied. Specifically, the margins are 10 on the leakage rate, 2 on the crack size, and 1.4 on the applied load, as discussed in detail in NUREG-1061, Volume 3. (Note that in the submittal, the licensee did not discuss the margin of 1.4 on the applied load. The licensee should include this margin of 1.4 on the appliedloadintheLBBevaluations.)

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