ML19220C254
| ML19220C254 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco, Crane |
| Issue date: | 06/13/1978 |
| From: | Grimes B Office of Nuclear Reactor Regulation |
| To: | Taylor J BABCOCK & WILCOX CO. |
| Shared Package | |
| ML19220C252 | List: |
| References | |
| NUDOCS 7904300100 | |
| Download: ML19220C254 (5) | |
Text
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,s UNITEc STATES
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NUCLEAR REGULATORY CCMMISSION
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-e VVASNNGTCN D. C. 20555 h
r a....,j June 13,1978 g
Babcock & Wilcox Ccmoany ATTN:
Mr. James H. Taylor Manager, Licensing Nuclear Power Generation Division P. O, Sox 1250 Lynchourg, Virginia 24505 Gentlemen:
Significant wear has been found in control rod guide tubes at the Ccmoustion Engine
- ring (CE) NSSS facilities. The guide tube wear has been primarily located at the axial location where the control roc is "parkec" in tne fully withdrawn position during normal oper-ation.
CE postu.ates tnat the wear is caused by a flow induced vibration of tnr Inconel control rod against the softer Zircaloy guide tube.
Co rective actions, including increased operability surveillance, Step insertion of control rods and extensive sleevinc of both new anj irradiated guice tuces, have been taken at all affected CE facilities.
We realite taat your NSSS design is different from the CE system, however, we oelieve that a similar wear problem,could exist at facili-ties using your NSSS design. You are requested'to provide the enclosed additional information for all S&W facilities with operating licenses wi thin 60 days of the date of tnis letter.
Sincerely, M
Brian K. Grimes, Assistant Director for Engineering & Projects Diviaevn cf 0;erating Reactors
Enclosure:
Request for Accitional Info rmaton
- .4 i -
89 003 a
7 9 0 4 3 0 e 100
g REQUEST FOR ADDITIONAL INFORMATION INTEGRI 0F CONTRCL ROD GUIDE TUBE (CRGT)
QABCDCK & WILCOX FACILITIES Answers to the follo ig questiens should be su; cried with data and drawings to the extent possible.
1.
Describe the Jetails of any routine surveillance of fuel assemblies performed at your facilities using your NSSS design.
2.
Hava examinations of the fuel assembly guide tubes to detect wear been completed at any facility using your NSSS design? If so, pr0 vide the follcwing information-The metnod of examination (i.e. destructive testing, eddy-cur-a.
rent testing, ceriscope, borescoce, mechanical gage, /V, etc. )
5.
The areas of CRGT sxamined.
e Qualification of the exaninatien-procedure.
c.
d.
The num:er of CRGT samoled at each facility and the acclicable eperational parameters includinc:
the care location; E.:FH; time in service; related centrol red parameters; fluence; etc.
Results of ocservatiens or measurements.
e.
3.
Were any CRGT destructively tested (e.g., by mechanical or metallograchic metns) and what observations or measurements were mace?
- 's A.
What correlations were suggested between operating parameters and CRGT condition?
4 O
2-5.
If specific examinatiens for CRGT wear have not been completed at any facility, either provide other evidence for the absence of wear or answer tne follcwing:
a.
Are examinations planned?
If so, provide details as requested in 2 a-d.
b.
Have cut-of-pile wear tests been coroleted? If so, provide details including qualification of the test procedure and answers to 2 a-d.
Address vibration, faticue, ficw visuali:ation, etc.
6.
Document any other cbservations of wear or degradation foi tne examination of your fuel asse,iies (i.e., grid wear, post wear, etc. ).
Provide the results of your assessment of the consecuence of these observations. Describe any design changes effected to either mitigate the consecuences of this wea or eliminate the wear.
7.
If CRGT wear has been found at facilities using your N555 design:
What have been the attributive causes?
a.
b.
Have correlations been made to characteri:e tne phancmena with respect to operating procedures and plant specific ct. e parameters ?
.4 P.-JUU y)
3 c.
Are s: <
c locations within the core or particular CRGT within an assem ly more susce:tibie?
8.
If CRGT wear has been Observed at any facility using your NSSS design:
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 analy:ed.
b.
Discuss your structural design bases.
Indicate if provisions have been made to accommodate car in the dasign.
What amount of wear or related degradation wculd be cause for rejection for reload?
Provide the allcwable stresses used in the structural analysis.
Discuss the effects of tem:erature strain rate, notch severity, irradiation anc hydrogen content on mecnanical properties used to establish the allowable stresses.
~
Provide the results of your structural analysis summarizing the c.
CRGT leads and the primary and secondary stress intensities for normal, fuel handling, and accident leading conditiens.
d.
Discuss the effects of CRGT wear on the ti:ermal-hydraulic performance of the reactor under normal and accident conditions.
.4
4-9.
Discuss any control rod scram testing that has been canpleted to demonstrate scramacility in worn CRGT.
Address the effects of worn CRGT on scramability for the worst expected guide tube gecret ry.
Include the strain-deflection limits for control rod functionability.
10.
If examina:1ons for CRGT wear have not been or will not be made at representative facilities usi.'g your N555 design, provide justif' cation for continued operation of these facilities.
11.
S&'d has redesigned the guide tube lock nuts of later design fuel assemblies by making a change from :ircaloy to stainless steel to miticate the ef'1 cts of observed wear in the upper region of the guide tube.
Indicate wnicn design is employed at each B&W designed facility and indicate any observations that have been made to detect wear in this area and/or verify the adecuacy of the redesign I
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