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OCT :: s $73 MEMORANDUM FOR: Lester Rubenstein, Acting Chief, Light Water Reactors Branch No. 4, DPM FROM:
Karl Kniel, Chief, Core Perfomance Branch, DSS
SUBJECT:
GUIDE TUBE WEAR IN B&W FUEL ASSEMBLY DESIGNS Plant Name:
Midland, Units 1 and 2 Milestone Number:
12-24 Docket Number:
50-329/330 Licensing Stage:
OL Responsible Branch LWR #4 and Project Manager:
D. Hood Review Branch Involved:
Core Performance Branch Description of Review:
Request f ar Additional Information Review Status:
Incomplete In response to a staff incuiry (Ref.1), Babcock & Wilcox has submitted infomation (Ref. 2) on their experience with guide tube wear.
In reviewing this brief information, the Core Performance Branch and the Reactor Safety Branch (DOR) have been unable to favorably concludt their reviews ('Ref. 3). Therefore, to aid in resolving this open item, we request that the attached questions be forwarded to Consumers Power Ccmpan Furthemore, because (a) the Babcock & Wilcox information (Ref. 2)y.was not submitted to NRC via the applicant's docket and (b) neither Babcock
& Wilcox nor the applicant have femally specified that the information is applicable to this OL application, the applicant's response should incorporate by reference the previous submittal (Ref. 2 of the cover memorandum or Ref.1 of the attachment).
It is our opinion that Consumers Power Company will not be able to answer all of these enclosed questions on a time scale that will be comoatible with a schedule that pennits issuance of an OL in the near future. However, guide tube wear is a time-dependent arecess, and we have reason to believe that the guide tube wear rates in the Midland fuel design will be less than those experience in other NSSS designs, for which continued operation of up to one cycle with worn tubes has been justified. Furthermore, we believe that operation of the Midland facilities for one cycle will not result in severe wear or hole femation 11 the guide tube walls. Therefore, we recomend that this issue not be
Contact:
Dale Powers, x27603 g
j 03b 791114 8
. considered unresolved for issuance of the OL, but that the license be conditioned such that this issue is completely resolved prior to startup of the second cycle.
The attached list of questions is concurrently being transmitted directly to Babcock and Wilcox and licensees using B&W NSSS designs for resolution with regard to operating reactors. Our (DSS and 00R reviews are being fully coordinated.
Karl Kniel, Chief Core Performance Branch Division of Systems Safety
Attachment:
As stated cc:
R. Denise S. Varga D. Eisenhut D. Hood D. Vassallo 2050 032
References 1.
B. K. Grimes (USNRC) letter to J. H. Taylor (B&W), June 13, 1978.
2.
J. H. Taylor (B&W) letter to B. K. Grimes (USNRC), January 12, 1979.
3.
B. K. Grimes (USNRC) letter to J. H. Taylor (B&W), August 22, 1979.
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ATTACHMENT NRR QUESTIONS ON GUIDE TUBE WEAR OCTOBER 1979 2030 0;4
ATTACHMENT 1.
The B&W surveillance experience on worn guide tubes consists of (a) air testing of sixteen guide tubes ' rom an Oconee-1 15x15 fuel assembly that had experienced one cycle of operation under a control rod assembly (Ref. 1) and (b) clam-shell sectioning of two guide tubes from a 17xl7 fuel assembly that had undergone a 1.000-hour flow test under a control red assembly (Ref.1). Webelieve(Ref.2) that this experience is not sufficient to support the B&W conclusion that there is strong evidence for the absence of wear in B&W-designed plants.
In fact, to the contrary, worn guide tubes have been observed in Crystal River, Unit 3 spent fuel (Ref. 3). Our position is further based on observations made by other NSSS vendors who have found a "pl ut-specific" and " core-position" deoendence in the observed wear. Furthermore, out-of pile flow tests have demonstrated ths the wear rate is a function of several design and operating variables.
Hence, the applic&nt, licensee, or B&W should propose for NRC review a post-irradiation examination (PIE) program dth a schedule for its implementation and a comitment to execute the program.
This data-gathering program should be completed expeditiously considering the availability of irradiated assemblies in all B&W-designed plants. Details of the surveillance plan s~ ould include n
the following.
a.
Methods of examination (e.g., destructive, eddy current probe, boroscope, mechanical gage) accompanied by qualification of tho;e methods.
b.
Characterization of the examined guide tubes, including their in-core locations, EFPHs, flow rates, fluence, and wear time under rods (control, instrument, axial-power shaping, burnable poison, startup source, and orifice).
c.
Examination of those rods (control, instrument, axial-power shaping, burnable poison, startup source, and orif'ce) contained within the guide tubes to identify fatigue, stress corrosion 2030 035 7
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2 cracking, Gr, denting, or any other conditions that can degrade their design function, reduce their design lifetime, or impede their movement.
d.
Analysis of results including quantification of guide tube wall wear depth and distribution. This PIE program may be satisfied in part of totality by reference to data takea from another B&W designed plant (s) that uses the same type of fuel assemblies. In such case, justification must be given that wear in the referenced plant adequately represents that of the plant design in ouestion.
e.
Provide all correlations supported by your tests and discuss how these correlations are used to predict guide tube wear during reactor operations over the fuel lifetime.
2.
Provide an evaluation on the predicted guide tube wear on the stress analyses contained in the FSAR. The evaluation should address Mdings associated with Condition-1 through -4 events including fal handling accidents, control rod scrams, and seismic and LOCA transients. The discu:sion should describe the state of stress in the worn guide tubes and how the wear affects the loadbearing characteristics of the worn tubes.
(Note that nonuniform wear results in a shift of the neutral tube exis which then induces not only direct stresses but also bending stresses.) Show that the loadbearing capacity of the worn guide tubes satisfies the acceptance criteria for these loading events.
3.
Provide or reference all material property correlations that are used in the guide tube stress analyses. These correlations should accommodate the effects of hydrogen absorption and the propensity for hydrogen uptake in the Zircaloy guide tubes as a function of accumulative wear.
4.
Reference 1 does not address the consecuences of hole formation in worn guide tubes. Consider the extent and distribution of wear to see if hole fornation is possible.
If the potential for hole 2050 036
3 formation cannot be. discounted, evaluate the imnact of such holes on the guide tube integrity, control red motion, and local thermal-hydraulic performance. This evaluation should account for flow-induced vibration resulting in crack propagation and possible fatigue fracture in locally thinned areas of the tube wall. This discussion should also address the entire core residence time, both during periods of wear (under rods; i.e.,
control, instrument, axial-power shaping, burnable poison, startup source, and orifice) and when the tubes are not rodded.
2030 037
2 References 1.
J. H. Taylor (B&W) letter to B. K. Grimes (USNRC), January 12, 1979.
2.
B. K. Grimes (USNRC) letter to J. H. Taylor (B&W), August 22, 1979 3.
" Crystal River Unit 3 Licensing Considerations for Continued Operation Without Burnable Poison Rod Assemblies and Orifice Rod Assemblies,"
Babcock & Wilcox Company Report, SAW-1490, Rev. 1, July 1978.
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