ML19344D574

Forwards Request for Addl Info Re Review of OL Application. Schedule Based on Assumption That Info Will Be Available by 800505.Requests Response within Seven Days After Receipt of Ltr If Date Cannot Be Met

ML19344D574
Person / Time
Site:	Farley
Issue date:	04/01/1980
From:	Stolz J Office of Nuclear Reactor Regulation
To:	Clayton F ALABAMA POWER CO.
References
NUDOCS 8004250048
Download: ML19344D574 (11)

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UNITED STATES

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NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20S$5 s, ~ f a s

p APR 1 1980 Docket No. 50-364 Mr. F. L. Clayton, Jr.

Senior Vice President Alabama Power Company 600 North 18th Street Birmingham, Alabama 35291

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION FOR FARLEY 2 OPERATING LICENSE APPLICATION As a result of our continuing review of the operating license application for the Joseph M. Farley Nuclear Plant Unit 2, we have developed the enclosed request for additional infomation.

Please provide the information requested in the enclosure. Our review schedule is based on the assumption that the additional information will be available for review by fiay 5, 1980.

If you cannot meet this date, please inform us within 7 days af ter receipt of this letter so that we may revise our scheduling.

Sincerely, r

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Join F. Stolz, Chief j

L ght Water Reactors Branch No. 1 ivision of Project Management

Enclosure:

Request for Additional Information cc: See next page 8004250 0

.-. l-D Mr. F. L. Clayton, Jr.

cc: Mr. Alan R. Barton Executive Vice President Alabama Power Company Post Office Box 2641 Birmingham, Alabama 35291 Mr. Ruble A. Thomas

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• 4 Vice President Southern Company Services, Inc.

Post Office Box 2625 Birmingham, Alabama 35202 Mr. George F. Trowbridge Shaw, Pittman, Potts and Trowbridge 1800 M Street, N. W.

[;T Washington, D. C.

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i ENCLOSURE REQUESTS FOR ADDITIONAL INFORM 4 TION JOSEPH M. FARLEY NUCLEAR PLANT 'JNIT 2 DOCKET NO. 50-364 Requests from the following branch in NRC are included in this enclosure.

Requests and pages: are numbered sequentially with respect to requests trans-mitted following issuance of SER Supplement No. 3.

Branch Page No.

Core Performance Branch 231-1 through 231-6 f

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i 231-1 231.0 REACTOR CORE PERFORMANCE BRANCH - FUELS SECTION 231.1 Following our review of the improved Wdstinghouse fuel per-formance code (PAD 3.3/WCAP-8720), we stated that the old per-famance code (PAD 3.1-Farley reference 4.2.4-3) was no longer acceptable for reference in license applications. Fuel performance analysis for Farley 2 should be performed with the approved version of PAD 3.3 and the results evaluated against your fuel rod design criteria.

231.2 Westinghouse has documented in WCAP-8963 a change in the internal fuel rod gas pressure criteria. Will the fuel design criterion for Farley 2 incorporate this change for rod pressure?

If so, provido the criterion as modified by NRC review, the above noted reference, I

and a reanalysis in the FSAR of affected evaluations.

231.3 Westinghouse has observed guide thimble tube wear on some of its fuel assemblies and has submitted information (References 1, 3 and 5 below) to us on this matter.

Since this experience could potentially affect the Farley 2 fuel, additional information as detailed below is needed to provide a basis for resolving this issue.

You must either (a) directly provide information for Farley 2 equivalent to that contained in References 1, 3 and 5 along with answers to the following related quest; ions, or (b) state the applicability to Farley 2 of similar information and answers that you can reference in a Licensing Topical Report (there are none at present) or another docketed plant Safety Analysis Report.

(a') Please provide the basis and derivation of the guide thimble wear model described in Reference 1.

In particular, explain assumption 4 and the equations proviNd under assumption 7.

Does the model predict maximum lo".al wear or average circum-ferential wear?

(b) Using the guide thimble wer.r model, Westinghiuse has predicted I

maximum stresses and stress intensity limits for worn guide thimble walls in two fuel assembly designs, which were subjected

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(W 231-2 to a 6g handling load. These calculated values are listed in Table 4.1 of Reference 1.

We note that the stress intensity limits increase as a function of time for both fuel assembly designs and that the limits always remain greater than the maximum stresses, which increase as the wall is worn away.

From the supporting discussion preceeding Table 4.1, it is not clear if the stress intensity limits are time deoendent.

Such an assumption would explain the noted increase in stress limits, but does not address the decreasing material toughness, associated with irradiation hardening.

If such credit is being used, it is contrary to the previous Westinghouse position in Reference 2 and item 4.0.5 of Reference 1.

Please clarify whether or not Westinghouse has taken credit for irradiation strengthening. Show that the criteria adopted represents the more conservative approach.

(c) Guide thimble wear data, which were taken from Point Beach Units 1 and 2 spent fuel, are discussed, listed, and plotted in Section 2.3, Table 2.1, and Figure 5, respectively, of Reference 1.

Please confirm that the time units in Section 2.3 and Table 2.1 l

are in error and make corrections as needed. Should not the units be days instead of hours?

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(d) Submitted Westinghouse information does not explain why the i

guide thimble wear model, which was developed from measurements taken on two 2-loop plants with 14x14 fuel assemblies, is applicable to wear predictions on plants of other designs.

Other NSSS-vendor-designed plants have experienced a " plant-specific" and " core-position" dependence in the observed wear. Therefore, please explain how the model accounts for wear differences and provide supporting data for all Westinghouse design variations. If the analytical treatment of design variations are justified, the supporting data can be provided in a confinnatory manner after NRC approval of the model.

Please provide details of yc.. data-rthering proposal, a schedule for its implementation, and state your connitment to t'

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carry out this confirmatory program. This data-gathering program should be completed expeditiously considering the availability of irradiated assemblies in all Westinghouse plants.

(e). In Reference 3 Westinghouse stated that the effect of hydrogen content on the mechanical properties of Zircaloy is dicussed in WCAP-9179 (Reference 4). We have reviewed that topical report and found no information on this issue. Please provide your evaluation of how this consideration affects the safety analysis.

Include in this evaluation a description of the propensity for hydrogen uptake of the Zircaloy as a function of the accumulative l

wear.

(f) When eddy current testing was conducted on worn guide thimble tubes frnm the Point Beach Units, did the. presence of zirconium j

hydrides affect the results? How sensitive is the interpre-tation of eddy current signals to hydride presence?

How is the effect taken into account?

(g) References 1, 3, and 5 do not address the consequences of hole i

formation in wrn guide thimble tubes. Moreover, it is not clear from the submitted information if Westinghouse (1) has observed holes during inspection of the 49 guide thimbles 3

tubes that were examined in the Point Beach spent fuel, or (2) has predicted (with the guide thimble wear model) hole fomation to occur during projected fuel lifetime. Please clarify. Also, if holes have been observed or are anticipated, provide a discussion on the impact of such holes on guide thimble tube integrity, control rod motion, and thermal-hydrualic i

perfomance. This discussion should also account for flow-induced vibration resulting in crack propagation and possibly fatigue fracture in locally thinned areas of the thimble wall.

This discussion should address th'e integrity of the thimble tubes during the entire care residence time; both during periods of wear (under RCCA) and when the fuel assemblies are not under RCCA.

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231 I (h) During the review of WCAP-9179 (Reference 6), the staff questioned the Westinghouse value of the ultimate tensile strength of Zircaloy components. The subsequent Westinghouse response l

(Reference 2) stated that the ultimate tensile strength of Zircaloy was not used in the design analyses of present fuel assembly designs. However, the analysis contained in Reference 1 uses the ultimate strength as a limiting variable. There-T fare, please submit for review the Westinghouse correlation for the ultimate tensile Strength of Zircaloy.

(i) Section 4.1 of Reference 1 states that the stress intensity factors are plotted as a function of time for 14x14 and 17x17 fuel assemblies in Figure 5.

This is not true. Please provide such a figure or amend Figure 5 as necessary.

(j) Per item d, Section 4.0 of Reference 1, your analyses are based on uniform wear in all thimble tubes. Address the margin of conservatism for this assumption. Compare your results with an analysis that considers non-uniform wear re-sulting in a shift of the neutral axis. Note that such shifts will result in both direct stress and bending stresses.

(k) For Condition-1 and -2 load analyses of Reference 1, a skew factor is mentioned that accounts for the uneven axial load 3

distribution. Clarify how the skew factor is related to both geometric changes (resulting from uneven wear) und assembly misalignment. How does the skew factor impact the load analyses?

(1) The equation for the wear volume in Reference 1 appear;; ifnear with time.

However, in Figures 5 and 6, wear depth is plotted versus time, and the resulting correlation appears to be non-linear. Please provide information on how these parameters are related.

(m) For Condition-3 and -4 load analyses described in Reference 1, it is stated that the stresses in a worn guide thimble tube are based on generic stress calculations. Please reference where 4

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231-5 these generic stress calculations can be found.

i It is also stated that the stresses in the unworn cuide thimble tub'es increased to account for the reduction of the tube cross due to the wear scar.

This would indicate credit for a load redistribution to the unworn guide thimble tubes.

Is a skew factor employed in the Condition-3 and -4 load analyses?

Describe the state of stress in the worn guide tubes and how the t

uneven wear affects the load-bearing characteristics of the worn tubes.

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231-6 References 1.

T. M. Anderson (W) letter (NS-TMA-2102) to D. G. Eisenhut (USNRC),datedJu'ne 27, 1979.

2.

T. M. Anderson (W) letter (NS-TMA-1985) to J. F. Stolz (USNRC), dated November 10, 1978.

T. M. Anderson (') letter (NS-TMA-1936) to D. G. Eisenhut 3.

f (USNRC),datedSeptember 12, 1978.

4.

P. J. Kuchirka, " Properties of Fuel and Core Component Materials,"

Westinghouse Electric Corporation Report, WCAP-9179, Rev.1, dated July 1978.

5.

T. M. Anderson (W) letter (NS-TMA-1992) to D. G. Eisenhut (USNRC), dated December 15, 1978.

6.

P. J. Kuchirka, " Properties of Fuel and Core Component Materials,"

Westinghouse Electric Corporation Report, WCAP-9179, dated October 25, 1977.

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