ML19209A329
| ML19209A329 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/07/1979 |
| From: | Parr O Office of Nuclear Reactor Regulation |
| To: | Proffitt W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| References | |
| NUDOCS 7910030611 | |
| Download: ML19209A329 (9) | |
Text
- W POR
- o, UNITED STATES
! *j ) ( *j NUCLEAR REGULATORY COMMISSION
- ,;p
- . g WASHINGTON, D C. 20555 k..v,/
SEP 0 71979 Docket No. 50-339 Mr. W. L. Proffitt Senior Vice President - Power Operations Virginia Electric & Power Company P. O. Box 26666 Richmond, Virginia 23261
Dear Mr. Proffitt:
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION To continue our review of your application for a license to operate the North Anna Power Station, Unit 2, adt'itional information is required.
The information requested is described in the Enclosure. The information requested in the Enclosure is based on our evaluation of information submitted by Westinghouse related to their experience with guide thimble tube wear (see Reference 1, 3 and 5 listed in the Enclosure).
To maintain our licensing review schedule, we will need a completely adequate response to the enclosed request by September 21, 1979.
Please inform us after receipt of this letter of your confirmation of the above date or the date you will be able to meet.
Sincerely,
% @. [n lan D. Parr, Chief Light Water Reactors Branch No. 3 Division of Project Management
Enclosure:
Request for Additional Information cc w/ enclosure:
See next page 1085 189 7910080 6//
//
SEP 0 71979 9
Mr. W. L. Proffitt cc: Mr. Anthony Gambaradella Cl arence T. Ki pps, Jr., Esq.
Office of the Attorney General 1700 Pennsylvania Avenue, A.W.
11 South 12th Street - Room 308 Washington, D. C.
20006 Richmond, Virginia 23219 Carroll J. Savage, Esq.
Richard M. Foster, Esq.
1700 Pennsylvania Avenue, N.W.
211 Stribling Avenue Washington, D. C.
20006 Charlottesville, Virginia 22903 Mr. James C. Dunstan Michael W. Maupin, Esq.
State Corporation Comission Hunton, Williams, Gay & Gibson Comonwalth of Virginia P. O. Box 1535 Blandon Building Richmond, Virginia 23212 Ri chmond, Vi rgini a,
.3209 Mrs. June Allen Alan S. Rosenthal, Esq.
412 Owens Drive Atomic Safety and Licensing Appeal Board Huntsville, Alabama 35801 U.S. Nuclear Regulatory Comission Washington, D. C.
20555 Mr. James Torson 501 Leroy Michael C. Farrar, Esq.
Socorro, New Mexico 87801 Atomic Safety and Licensing Appeal Board U.S. Nuclear Regulatory Comission Mrs. Margaret Dietrich Washington, D. C.
20555 Route 2, Box 568 Gordonsville, Virginia 22942 Dr. John H. Buck Atomic Safety and Licensing Appeal Board Willian H. Rodgers, Jr., Esq.
U.S. Nuclear Regulatory Comission Georgetom University Law Center Washington, D. C.
20555 600 New Jersey Avenue, N.W.
Washington, D. C.
20001 Atomic Safety and Licensing Boird Panel U.S. Nuclear Regulatory Comission Mr. Peter S. Hepp Washington, D. C.
20555 Executive Vice President Sun Shipping & Dry Dock Company Mr. Michael S. Kidd P. O. Box 540 U.S. Nuclear Regulatory Comission Chester, Pennsylvania 19013 P. O. Box 128 Spotsivania, Virginia 22553 Mr. R. B. Briggs Associate Director Dr. Paul W. Purdom 110 Evans Lane Department of Civil Engineering Oak Ridge, Tennessee 37830 Drexel University Philadelphia, Pennsylvania 19104 P00RORIBEL 1085 190
A Mr. W. L. Proffitt dr. Lawrence R. Quarles cc:
Apartment No. 51 Kendal-at-Longwood Kennett Square, Pennsylvania 19348 Mr. Irwin B. Kroot Citizens Energy Forum P. O. Box 138 McLean, Virginia 22101 James B. Dougherty, Esq.
Potomac Mliance 1416 S Str eet, N.W.
Washington, D. C.
20009 i
1085 191
ENCLOSURE REQUEST FOR ADDITIONAL INFORMATION NORTH ANNA POWER STATION, UNIT 2 DOCKET NO. 50-339' 4.0 Reactor 4.17 Please provide the basis and derivation of the guide thimble wear model described in Reference 1.
In particular, explain assumption 4 and the equations provided under assumption 7.
Does the model predict maximum local wear or average circumferential wear?
4.18,_
Using the guide thimble wear model, Westinghouse has predicted maximum stresses and stress intensity limits for worn guide thimble walls in two fuel assembly des'.gns, which were subjected 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 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 pos[ tion 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.
4.19_
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 confim 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 infomation by reference in your response.
1085 192 P00Ron
. 4.20 Submitted Westinghouse information does not explain why the 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 exper-1enced 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 r.re justified, the sup-porting data can be provided in a confimatory manner after NRC approval of the model.
Please provide details of your data-gatherir.g proposal, a schedule for its implementation, and state your commitment to carry out this confimatory program. This data-gathering program should be completed expeditiously considering the availability of irradiated assemblies in all Westinghouse plants.
4.21 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 infoma-tion on this issue. Please provide your evaluation of how this considera-tion 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 wear.
4.22 When eddy current testing was conducted on worn gu de thimble tubes from i
the Point Beach Units, did the presence of zirconium hydrides affect the results? How sensitive is the interpretation of eddy current signals to hydride presence? How is this effect taken into account?
1085 193
- Incorporate this information by reference in your response.
P00RBRIGM
^
3-4.23 References 1, 3, and 5*do not address the consequences of hole formation in worn guide thimble tubes. Moreover, it is not clear from the submitted infomation if Westinghouse (1) has observed holes during inspection of the 49 quide thimbles tubes that were examined in the Point Beach spent fuel, or (2) has predicted kith the guide thimble wear model) hole fomation to occur during projected fuel lifetime. Please clarify. Also, if holes have been observed or are anticipated, proviu a discussion on the impact of such holes on guide thimble tube integrity, control rod motion, and themal-hydraulic perfomance.
This discussion should also account for flow-induced vibration resulting in crack propagation and possibly fatigue fracture in locally thinned area: of the thimble wall. This dis-cussion should address the integrity of the thimble tubes Juring the entire core residence time; both during periods of wear (under RCCA) and when the fuel assemblies are not under RCCAs.
4.24 During the review of WCAP-9179 (Reference 6), the staff questioned the Westinghouse value for the ultimate tensile strength of Zircaloy components.
The sut,requent Westinghouse response (Reference 2) stated that the ultimate ten.sile 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 Ii rcaloy.
- Incorporate this information by reference in your response.
P00R OR81M
~-
4-4.25 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.
4.26 Per item 4. Section 4.0 of Reference 1, your analyses are based on uniform wear in all thimble tubes. Address the margin o' conservatism for this assumption. Compare your results with an analysis that considers non-uniform wear resulting in a shift of the neutral axis. Note that such shifts will re'sult in both direct stress and bending stresses.
4.27 For Condition-1 and -2 load analyses of Reference 1, 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 wear) and assembly misalignment. How does the skew factor impact the load analyses?
4.28 The equation for the wear volume in Reference 1 appears linear 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 infomation on how these parar =^.us are related.
4.29 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 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 ms ns P00RORGINM
5-redistribution to the unworn guide thimble tubes.
Is a skew factor employed in the Condition-3 and A load analyses? Describe the state of stress in the worn guide tubes and how the uneven wear affects the load-bearing char-acteristics of the worn tubes.
w 1085 196 P00R ORGINAL
s ATTACHMENT References 1
T. 'M. Anderson (W) letter (NS-TMA-2102) to D. G. Eisenhut (USNRC),
dated June 27, 1779.
2.
T. M. Anderson (W) letter (NS-TMA-1985) to J. F. Stolz (USNRC),
dated November II,1978.
3.
T. M. Anderson (W) letter (NS-TNA-1936) to D. G. Eisenhut (USNRC),
dated September T2,1978.
4 P. J. Kuchirka "Drcperties of Fuel and Core Component Materials,"
o Westinghouse Electeie Corporation Report, WCAP-9179, Rev.1, dated July 1978.
T. M. Anderson (3) 1978. letter (NS-TMA-1992) to D. G. Eisenhut (USNRC),
5.
W dated December 1, 6.
P. J. Kuchirka, " Properties of Fual and Core Component Materials,"
Westinghouse Electric Corporation Report, WCAF-9179, dated October 25, 1977 t
1085 197 P00R ORGINJL
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