ML20236J874

Forwards Request for Addl Info Re Util Proposed Application of Leak Before Break Methodology to Eliminate Dynamic Effect of Postulated Primary Loop Pipe Ruptures from Design Basis, Per GDC-4.Response Requested within 30 Days of Ltr Receipt

ML20236J874
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	08/04/1987
From:	Chan T Office of Nuclear Reactor Regulation
To:	Cockfield D PORTLAND GENERAL ELECTRIC CO.
References
TAC-06596, TAC-6596, NUDOCS 8708060322
Download: ML20236J874 (5)

Text

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? I l t August 4, 1987 1 Docket No.: 50-344 DISTRIBUTION

. Docket File . Tchan )

Mr. David W. Cockfield NRC & Local PDRS OGC-Bethesda )

Vice President, Nuclear PD5 . Plant Files EJordan Portland General Electric Company GHolahan JPartlow 121 S.W. Salmon Street JLee ACRS (10)

Portland, Oregon 97204

Dear Mr. Cockfield:

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SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON ELIMINATION OF l DYNAMIC EFFECTS OF POSTULATED PRIMARY LOOP PIPE RUPTURES l FROM DESIGN BASIS FOR TROJAN NUCLEAR PLANT (TAC N0. 06596) l l

By letters dated October 25, 1985 and October 31, 1986, Portland General Electric Company (PGE) submitted a " leak-before-break" (LBB) evaluation of the reactor coolant loop piping for the Trojan Nuclear Plant. PGE proposed to apply the LBB methodology to eliminate the dynamic effects of postulated primary loop pipe ruptures from the design basis for Trojan, as permitted by 10 CFR 50, Appendix A, General Design Criterion 4 (GDC-4)-1987.

The staff has reviewed the above submittals and finds that additional information is required before we can complete our evaluation. Accordingly, we ask that you provide the requested information within 30 days from receipt of this letter, or provide an alternate schedule for doing so within 15 days.

The reporting and/or recordkeeping requirements of this letter affect fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511.

Sincerely.

Original Signed by/

Terence L. Chan, Project Manager Project Directorate V Division of Reactor Projects-III IV, V and Special Projects

Enclosure:

Add. Info.

cc w/ enclosure See next page DRSP/PD5  :> DP PD5 TChan:ts.~- GKn gtton 8/J /87 8/ /87 0FFICIA1 RECORD COPY 870B060322 870004 PDR ADOCK 05000344 P PDR

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Mr. David W. Cockfield Portland General Electric Company Trojan Nuclear Plant i

I cc:

Senior Resident Inspector 1 U.S. Nuclear Regulatory Commission Trojan Nuclear Plant )

Post Office Box 0 Rainier, Oregon 97048 l

Michael J. Sykes, Chairman "

Board of County Commissioners Columbia County l' St. Helens, Oregon 97501 Mr. David Kish Oregon Department of Energy Labor and IndustFies Building ,

c Room 111 Salem, Oregon 97310 3

Regional Administrator, Region V

, U.S. Nuclear Regulatory Commission l

1450 Maria Lane, Suite 210 t l

Walnut Creek, California 94596 i

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/ 1 ENCLOSURE REQUEST FOR ADDITIONAL INFORMATION ON ELIMINATION OF POSTULATED PRIMARY LOOP PIPE RUPTURES AS A DESIGN BASIS -j

. PORTLAND GENERAL ELECTRIC COMPANY TROJAN NUCLEAR PLANT DOCKET NO. 50-344 By letter dated October 31, 1986, Portland General Electric Company (the licensee) submitted the technical basis for the elimination of primary loop pipe ruptures using " leak-before-break" (LBB) methodology for the Trojan Nuclear Plant in Impell Report No. 01-0300-1395, Revision 1, dated October 1986. The staff has reviewed the licensee's submittal for compliance with the revised General Design Criterion 4 (GDC-4) of Appendix A.10 CFR 50. The evaluation criteria are discussed in detail in NUREG-1061. Volume 3. The staff requires the following additional information from the licensee before our review can continue.

(1) The LBB criteria in NUREG-1061. Volume 3 contain margins on leakage rate,  ;

, crack size, and applied loads to account for uncertainties inherent in ,

the analyses. The LBB margins are discussed in detail in NUREG-1061 Volume 3. The margins on crack size and applied loads were not addressed i by the licensee in the submitted report. The licensee should discoss l compliance with the margin of "2" on the crack size and the margirl of

, "the square root of 2" on the applied loads. The licensee should i demonstrate the stability of a through-wall crack twice the size of the leakage-size crack under combined normal and safe shutdown earthquake (SSE) loads. Also, the licensee should demonstrate the stability of the leakage-size crack if the loads are increased to the square root of 2 times the combination of normal and SSE loads.

(2) In Section 2.5.1 of the submitted report, the licensee discussed the '

thennal aging effects of cast stainless steel on the unterial fracture toughness. However, the 9pecific extent of thensal aging depends on the chemistry and the ferrite, content of the cast material. The licensee should demonstrate that the data shown in Figure 5 of the submitted report provide a.lowerpmnd estimate of the toughness properties for the specific Trojan materia . Alternatively, the licensee should determine the thermally-aged fracture toughness for each cast stainless steel piping component material in the primary loop of Trojan based on its specific chemistry and the ferrite content.

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(3) The LBB analysis should be perfomed for the functional piping system l from anchor point to anchor point. In Figure 1 of the submitted report.

It is indicated that LB8 analyses wem performed at break. locations.. In Section 2.4.1 of the submitted report the licensee indicated that 4

several intermediate locations wem also considered. The L86 methodology should be separated from the methodology in Standard Review Plan 3.6.2 9 which discusses break locations. In the application of LBB. the piping .,

system from anchor to anchor, including all intermediate locations, should be considered. The Ifmiting location for LBB analyses is the location with the highest stresses coincident with the poorest material i properties for base materials, weldments, and safe ends. The effects of l iS. themal aging as discussed in item 2 above must be considered. '

(4) Linear elastic fracture mechanics (LEFM) was used for the fracture stability analysis. However, from the calculated fracture mechanics parameter "J-integral" it appears that the associated Irwin plane-stress plastic zone sizes are not small compared with the half-crack len  !

The licensee should use elastic-plastic fracture mechanics (EPFM)gth.-

instead .

of LEFM procedures. Although the licensee attempted'to compare the l plastic zone wi+h the uncracked circumference in Table 6 of the submitted report, the proper commrison should be with the crack length because the i crack length is less tian the uncracked circumference. Furthemore, the '

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licensee should benchmark the EPFM procedure against experimental pipe test data.

(5) In Section 2.4.1 of the submitted report. it is indicated that SSE loads

, were obtained by multiplying the maximum operating basis earthquaks (OBE) loads by a factor of 1.67. Describe the validity of obtaining SSE loads  ;

from OBE loads.

(6) In Section 2.5.2 of the submitted report it is indicated that four typical weld procedures were reviewed to detemine the welding process of the primary loop. From this review, the licensee detensined that the weldingprocesseswereshieldedmetalarcwelding(SMAW)andgas-tungsten arcwelding-(GTAW). The licensee should review all-the welding procedures for the primary loop to determine if submerged arc welds (SAW) were used. Also, indicate if solution annealing was performed.

Furthermore, the staff disagrees with the licensee's assertion in Section 2.5.3 of the submittedpport that the fracture toughness of GTAW would bound that of SMAW. 1 (7) In Section 2.4.2 of the submitted report, it is indicated that' ASME Code  !

minimum material properties were used. Because'various materials were used in the fabrication of the primary loop, describe the Code minimum of which material was used for the calculations and justify this selection.

Also, provide the elastic modulus, yield strength, ultimate strength, and  ;

stress-strain' curve at the limiting. location and at the operating temperature. The licensee would have to select these material propertfes in order to perfo m a EPFM evaluation as discussed in item 4 above.

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q (8) In Sect' ion 2.4.2 of the submitted report,-the licensee indicated that a fully-plasticdisplacement-controlledtearingmodulus(J-T)analysiswas j

performed. Describe whether the J-T-result shown in Figure 8 of the 1 submitted report was calculated for a 7-inch crack in 'the hot leg . vessel outlet nozzle. If the calculation was based on a 25-inch crack as discussed in Section 2.4.2 of the submitted report, it is not conservative to use the J-integral value for a 7-inch crack on the J-T curve for a 25-inch crack. Also, the licensee should use elastic-plastic i load-controlled J-T analysis because a fully-plastic .

l displacement-controlled J-T analysis may not be conservative.

Furthermore, if crack growth is predicted before instability, crack l growth should be considered in the J-T analysis.

(9) In Appendix A'of the submitted report, the licensee indicated that the leakage prediction computer code has been benchmarked against test data.

The licensee should submit the benchmarking results for staff review.

(10) In Table 1 of. the submitted report, the licensee listed the diameters and '

wall thicknesses of the hot leg, crossover leg, and.the cold leg.

Describe whether the nominal' dimensions or minimum dimensions were tabulated. If nominal dimensions were used, the licensee.should review the as-built configuration of the primary loop weldments to determine  !

whether the actual thickness is less than the necinal thickness. Due to l

}' ~ weld fit-up, the actual thickness may be less than the nominal pipe thickness.

. l (11) In Appendir. C of the submitted report, a fatigue crack growth analysis was discussed. Describe the design transients' considered in the '. i

, analysis. Also, show the crack growth material data used for the  :

analysis.

(12) Net section plastic analysis was discussed in Section 2.6 of the submitted report. However, net section analysis does not account for material toughness limitations. In particular, low toughness thermally-aged cast stainless steel is involved in the present LBB evaluation. The licensee should use a fracture stability analysis which ,

accounts for material toughness.

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