ML18079B027
| ML18079B027 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 09/07/1979 |
| From: | Parr O Office of Nuclear Reactor Regulation |
| To: | Mittl R Public Service Enterprise Group |
| References | |
| NUDOCS 7910030606 | |
| Download: ML18079B027 (8) | |
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a(r Local PDR M. Rushbrook LWR #3 File A. Dromerick D. Vassallo R. Mattson D. Ross S. Hanauer S. Varga J. Knight Docket No. 50-311 R. Tedesco R. DeYoung V: Moore vJ. Kreger M. Ernst R. Denise OELD IE (3) -
_SEP 0 7 1979 BCC:
JBuchanan TAbernathy ACRS (l~)
Mr. R.
L~ Mittl, Gener~l Manager Licensing and Environrneht
- Engineering and Construction Department Public Service Electric and Gas Company 80 Park Place Newark, New Jersey 07101
Dear Mr. Mittl:
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE SALEM UNIT 2 FINAL SAFETY ANALYSIS REPORT (FSAR) 1~s a result of our continuing review of the Salem FS.l\\R~ we find.that we need additional information to complete our evaluation.
The specific information required is 1 isted in the Enclosure.
- The information requested is based on our evaluation of information submitted by Westinghouse related to their I
experienc~ with guide thimble tube wear (see References l, 3 and 5 listed in the Enclosure).
- Our review schedule is based on.the assumption that this additional information will be available for our review by September 21, 1979.
If you cannot meet this date, please inform us within seven days after receipt of this letter so that we may revise our schequle accordingly.
Please contact us if you desire any discussion or clarification of ~he enclosed request.
Enclosure:
Request for Additional Information cc w/enclosure:
Sincer.ely, Orr *
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01 an D. Parr, Chief Light Wat~r Reactors B~anch No. 3 Division of Project Management
Mr. R. L. Mittl, General Manager
- cc: Richard Fryling, Jr., Esq.
Assistant General Counsel Public Service Electric & Gas Company 80 Park Place Newark, New Jersey 07100 Mark Wetterhahn, Esq.
Conner, Moore & Caber 1747 Pennsylvania Avenue, N.W.
Suite 1050 W~shington, D.C.
20006 Mr. Leif J. Norrholm U.S. Nuclear Regulatory Commiss.ion Region I Drawer I Hancocks Bridge, New Jersey 08038
3.0 Reactor ENCLOSURE R.ST FOR AIJDITIONAL INFORMATION e SALEM NUCLEAR GENERATING STATION, UNIT 2 DOCKET NO. 50-311 3.14 Please provide the basis and derivation of the guide thimble wear model described in Reference.l.
In particular, explain.assumption 4 and the equations provided under assumption 7.
Does the model predict maximum
- 1ocal wear or average circumferential wear?
3.15 Using the guide thimbl~ wea~ model, Westinghouse has predicted maximum stresses and ~tress intensity limits for worn guide thimble walls in two fuel assembly designs, which were subjected to*a 69 handli~g load.
These calculated values are listed in Table 4.1 of Reference 1.
We note that the ~tress 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 dependent.
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 wheth~r or*not Westinihouse has taken credit for irradiation strengthening.
Show that the criteria adopted represents the more conservative approach.
- 3. 16 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 are in error and make corrections as needed.
Should not the units be days instead of hours?
- Incorporate this information by reference in your response.
3.17 Submitted We.stinghouse infonnation does not explain*why the guide thimb1e
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3.18 wear model, which was developed from measurements taken on two 2-loop p1ants with 14x14 fuel assemblies, is applicable to wear predictions on plants of other designs.
ether NSSS-vendor-designed plants have exper-ienced a "plant-specific" and "core-position" dependence in the observed wear.
Therefore. please.explain how the model accounts for wear differ-ences and provide supporting data for all Westinghouse design variations.
If the analytical treatment of design variations are justified, the sup-porting data can be provided in a confirmatory manner after NRC approval of the model.
Please provide details of your data-gathering proposal, a schedule for its implementation, and state your commitment to carry out this confirmatory program.
This da ta-gathering program should be comp 1 eted expeditiously considering the availability of irradiated assemblies in all Westinghouse plants.
In Reference 3, Westinghouse stated that the effect of hydrogen content on the mechanical properties of Zircaloy is discussed in WCAP-9179
~Reference 4~.
We_ have reviewed that topical report and found no infonna-tion *on this issue.
Please provide your evaluation of how this considera-tion affects the safety ana1ysis.
Include in this evaluation a description of the propensity for hydrogen uptake of the Zircaloy as a function of the accumu1ative wear.
3.19 When eddy current testing was conducted on worn guide thimble tubes from the Point Beach Units, did the presence of zirconium hydrides affect the resu1ts?
How sensitive is the interpretation of eddy current signals to hydride presence?. How is this effect taken into account?
- Incorporate this information by reference in your response.
3.20 References 1, 3, and 5 do not address the consequ~nces of hole fonnation in worn guide thimble tubes. Moreover, it is not clear from the submitted infonnation if Westinghouse (l) has observed holes during inspection of the 49 quide thimbles tu~es that were examined in the Point Beach spent fuel, or (2) has predicted ~ith the guide thimble l'.iear model) hole fonnation to occur during projected fuel lifetime.
Please clarify. Also, if holes have been observed or are anticipated, provide a discussion eri the impact of such holes on guide thimble tube integrity, co~trol rod motion, and thermal-hydraulic perfonnance.
This discussion should also account for flow-induced vibration resulting in crack propagation and possibly fitigue. fracture in locally thinned areas of the thimble wall. This dis-cussion should address the integrity of the thimble tubes during the entire core residence time; both during periods *of wear (under RCCA) and w~en the fuel assemblies are not under RCCAs.
3.21 During the review of WCAP-9179 {Reference 6), the staff questioned the Westinghouse value for the ultimate tensile strength of Zircaloy components~
The subsequent Westinghouse response {Reference 2) stated that the ul.timate 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. Therefore, please submit for*
review the Westinghouse correlation for the ultimate tensile strength of Zircaloy.
- Incorporate this iDformation by reference in your response.
3.22 Section 4.1 -Of Referen~e 1 states that the stress*intensity factors are plotted as a function of time for 14xl4 and 17xl7 fue1 assemblies in
- Figure 5. This is not true. Please provide such a figure or amend Figure 5 a~ neces!ary.
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3.23 Per.item 4, Section 4.o of Reference 1, your analyses are based on uni form wear in a 11 thimble tubes. Address the margin of conservatism* for this assumption.
Compare your results with an analysis that considers non-uni form wear resulting in a shift of the neutral axis.
Note that such shifts wi l 1 result in.both direct stress and bending stresses.
3.24 For Condition-1 and -2 load analyses of Reference l, a skew factor is mentioned that accounts for the uneven axial load distribution.
Clarify how the skew factor is related to both geometric changes (resulting from uneven wearj and assembly misalignment.
How does the skew factor impact the load analyses?
3.25 The equation for the w~ar volume in Refer~nce 1 appears linear with time.
However, in Figures 5 and 6, wear depth is plotted versus time, and the res.ulting correlation appears to be* non-linear.
Please provide. infonnation on how these parameters are related.
3.26 For Conditibn-3 and -4 load analyses described in Reference l, it is stated that the stresses in a worn guide thimble tube are based on generic stress calculations.
Please reference where these generic str.ess calcula-tions can be found.
It is also stated that the stresses in the unworn guide thimble tubes are increased to account for the reduction of the tube cross section 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 Condit.ion-3 and -4 load analyses? Describe the state of stress in I
the worn guide tubes and how the uneven wear affects the load-bearing char-*
acteristics of the worn tubes.
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ATTACHMENT References 1.
T. M. Anderson (W) letter (NS-TMA-2102) to D. G. Eisen hut (USNRC),
dated J u n e 2 7, 197 9.
- 2.
T. M. Anderson (W) letter (NS-TMA-1985) to J. F. Stolz (USNRC),
dated November 10, 1978:
- 3.
T. M. Anderson (W) letter (NS-TMA-1936) to D. G. Eisenhut (USNRC),
dated September T2, 1978.
- 4.
P. J. Kuchirka, "Properties of Fuel and Core Component Materials, 11 Westingho"use Electric Corporation Report, WCAP-9179, Rev. 1, dated Jul.Y 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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