ML20148E132
| ML20148E132 | |
| Person / Time | |
|---|---|
| Issue date: | 07/20/1978 |
| From: | Grimes B Office of Nuclear Reactor Regulation |
| To: | Nechodom W SIEMENS POWER CORP. (FORMERLY SIEMENS NUCLEAR POWER |
| References | |
| NUDOCS 7811060121 | |
| Download: ML20148E132 (6) | |
Text
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UNITED STATES 1
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NUCLEAR REGULATORY QOMMisslON
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WASHINGTON, D. C. 20555
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July 20, 1978
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Exxon Nuclear Company, Inc.
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ATTN: Mr. Warren Nechodom Manager of Licensing and Compliance 2101 Horn Rapids Road Richland, Washington 99352 Gentlemen:
Significant wear has been found in control rod guide tubes at the Combustion Engineering (CE) NSSS facilities.
The guide tube wear has been primarily located at the axial location where the control rod is " parked" in the fully withdrawn position during normal oper-ation.
CE postulates that the wear is cau:ed by a flow induced vibration of the Inconel control rod against the softer Zircaloy guide tube.
Corrective actions, including the increased operability surveillance, step insertion of control rods and extensive sleeving of both new and irr diated guide tubes, have been taken at all affected CE facilities.
We realize that your fuel design is different from the CE design, however, we believe that a similar wear problem could exist at facili-ties ising your fuel.
You are requested to provide the enclosed additional information for all facilities using Exxon fuel within 60 days of the date of this letter.
Sincerely, Brian K. Grimes, Assistant Director for Engineering & Projects Division of Operating Reactors
Enclosure:
Request for Additional Information cc w/ enclosure:
See next page 7812.06OIdI f
Exxon Nuclear Company, Inc. cc w/ enclosure:
Exxon Nuclear Company, Inc.
ATTN:
Mr. G. Owsley 2101 Horn Rapids Road Richland, Washington 99352 1
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REQUEST FOR ADDITIONAL INFORh% TION INTEGRITY OF CONTROL ROD GUIDE TUBE (CRGT)
_ FACILITIES USING EXXON FUEL Answers to the following questions should be supported with data and drawings to the extent possible.
1.
Describe the details of any routine surveillance of fuel assemblies performed at facilities using your fuel.
2.
Have examinations of the fuel assembly guide tubes to detect wear been completed at any facility using your fuel?
If so, provide the following infonnation:
The method of examination (i.e. destructive testing, eddy-cur-a.
rent testing, periscope, borescope, mechanical gage, TV, etc,)
b.
The areas of CRGT examined, Qualification of the exanination procedure.
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c.
d.
The number of CRGT sampl'ed at each facility and the applicable operational paraneters including:
the core location; EFPH; time in service; related control rod parameters; fluence; etc.
Results of observations or measurements.
e.
3.
Were any CRGT destructively tested (e.g., by mechanical er metallographic means) and what observations or measurements were made?
4.
What correlations were suggested between operating parameters an?
CRGT condition?
5.
If specific examinations for CRGT wear have not been completed at any facility, either provide other evidence for the absence of wear or answer the following:
a.
Are examinations planned?
If so, provide details as requested in 2 a-d.
b.
Have out-of-pile wear tests been completed? If so, provide details including qualification of the test procedure and answers to 2 a-d.
Address vibration, fatique, flow visualization, etc.
6.
Document any other observations of wear or degradation found in the examination of your fuel assemblies (i.e., grid wear, post wear,etc.).
Provide the results of your assessment of the consequence of these observations.
Describe any design changes
. effected to either mitigate the consequences of this wear or
- eliminate the wear.
7.
If CRGT wear has been found at facilities using your fuel:
a.
What have been the attributive causes?
b.
Have correlations been made to characterize the phenomena with respect to operating procedures and plant specific core paramete rs ?
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3 Are specific locations within the core or particular c.
CRGT within an assembly more susceptible?
e 8.
If CRGT wear has been observed at any facility using your fuel:
Describe your efforts to reassess the mechanical integrity a.
of the core with worn CRGT to demonstrate that cool-ability and scramability exist for the normal, seismic and anticipated operational occurrence loading conditions.
Describe the worst condition analyzed.
b.
Discuss your structural design bases.
Indicate if provisions have been made to accommodate wear in the design.
What amount of waar or related degradation would be cause for rejection for reload? Provide the allowable stresses used in the :tructural analysis.
Discuss the effects of temperature strain rate, notch severity, irradietion snd hydrogen content on mechanical pro'porties used to establish the allowable stresses.
4b i
Provide the results of your structural analysis sumarizing the c.
CRGT loads and the primary and secondary strest intensities for normal, fuel handling, and accident loadinc conditions.
d.
Discuss the effects of CRGI wear on the thermal-hydraulic performance of the reactor under nomal and accident conditiens.
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. Discuss any control rod scram testing that has been completed 9.
Address the effects to demonstrate scramability in worn CRGT.
of worn CRGT on scramability for the worst expected guide tube Include the strain-deflection limits for control rod geometry.
functionability.
If examinations for CRGT wear have not been or will not be made 10.
at representative facilities using your fuel, provide justification for continued operation of these facilities.
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