ML19262A681
| ML19262A681 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 11/23/1979 |
| From: | Reid R Office of Nuclear Reactor Regulation |
| To: | Cavanaugh W ARKANSAS POWER & LIGHT CO. |
| References | |
| NUDOCS 7912100229 | |
| Download: ML19262A681 (6) | |
Text
TERA
- J 4
- "ECg\\
UNITED STATES
+-[ $wy i NUCLEAR REGULATORY COMMISSION
/. p W ASHINGTON, D. C. 20555 54 November 23, 1979 Docket No. 50-313 l
Mr. William Cavanaugh, III Vice President, Generation and Construction Arkansas Power & Light Company P. O. Box 551 Little Rock, Arkansas 72203,
Dear Mr. Cavanaugh:
Significan:. wear of the Zircaloy control rod guide tubes has been observed in facilities designed by Combustion Engineering (CE).
Similar wear has also been repoeted in those facilities designed by Westinghouse (W).
In our letter of June 13,1978, we requested information from Babcock and Wilcox (B&W) on the susceptability of the facilities designed by B&W to guide tube wear. The information provided by B&W by letter dated January 12, 1979 was insufficient for us to conclude that guide tube wear was not a significant problem in the j
facilities designed by B&W. This was documented in our letter to B&W dated August 22, 1979.
Because significant guide tube wear could impede the control rod scram capability, and also effect the required coolable geometry of the reactor core, we consider this wear phenomenon a potential safety concern.
Therefore, we are recuesting that you provide detailed infomation on the wear character-istics of the control rods on tha guide tubes in fuel assemblies in Arkansas Nuclear One, Unit No.1.
l The enclosed NRC concerns are provided to assist you in planning your control
~
rod and guide tube surveillance program. When you have completed your surveil-lance program plan, we request that this program be submitted for NRC review before inplementation. Although this data-gathering program may be perfomed on available irradiated assemblies in spent fuel pools, we find that this issue should be resolved for each facility before startup from your next scheduled refueling outage comencing after January 1,
1980.
To expedite our review of your program, a meeting at NRC headquarters in Bethesda, varyland, has been scheduled for December 20,1979, at 9:30 a.m.
This meeting will provide you the ocportunity to clarify and discuss the encicsed NRC concerns and the details of your proposed program.
Your ager.ca of the reeting should be provided by Decenber 17, 1979.
P00R DRRR 1527 285 7912100 f
i
s
.7_
Should you have an; questions on the type of inforr.ation we need or scheduling requirements, please contact our Operating Reactors Branch #4 Project Manager assigned to your facility.
Sincerely, D'
- O
,(.-j<.dl/,,4..>/
Robert W. Reid, Chief Operating Reactors Branch fi Division of Operating Rea tors Enclosure cc: w/e ncl osure See next page j
1527 286
Arkansas Power & Light Company cc:
Phillip K. Lyon, Esq.
House, Holns & Jewell 1550 Tower Building Little Rock, Arkansas 72201 Mr. David C. Trimble Manager, Licensing Arkansas Power & Light Company P. O. Box 551 Little Rock, Arkansas 72203 Mr. James P. O'Hanlon General Manager Arkansas Nuclear One P. O. Box 608 Russellville, Arkansas 72801 Mr. William Johnson U. S. Nuclear Regulatory Commission P. O. Box 2090 Russellville, Arkansas 72801 Mr. Robert B. Bor um Babcock & Wilcox 4
Nuclear Power Generation Division Suite 420, 7735 Old Georgetown Road Bethesda, Maryland 20014 Troy B. Conner, Jr., Esq.
Conner, Moore & Corber 1747 Pennsylvania Avenue, N.W.
Washington, D.C.
20006 Arkansas Polytechnic College Russellville, Arkansas 72801 m
1527 287
Enclosure NRC CONCERNS ON CONTROL ROD GUIDE TUBE WEAR IN FACILITIES DESIGNED BY B&W The ESW surveillance experience on worn control rod guide tubes, as cescribed in their January 12, 1979 letter, consists of (a) air testing of sixteen guide tubes from an Oconee-1 15x15 fuel assembly that had experienced one cycle of operation under a control rod assembly and (b) clam-shell sectioning of two guide tubes from a 17x17 fuel assemb.y that had undergone a 1000-hour flow test under a control rod assembly. As documented in our letter of August 22, 1979, we find that this experience is not sufficient to support the B&W con-clusion 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 (see BAW-1490 Rev. 1, July 1978).
Our position is further -
based on observations made by other NSSS vendors who have found a " plant-specific",
and " core-position" dependence in the observed wear.
Furthermore, out-of pile flow tests have demonstrated that the wear rate is a function of several design and operating variables.
1.
Propose a post-irradiation examination (PIE) program with a schedule for its implementation and a comitment to execute the program for NRC review.
This data-gathering program should be completed expeditiously considering g
the availability of irradiated assemblies in all B&W-designed plants.
?
Details of the sarveillance plan should include the following:
a.
Ve:ho:s :# exa-inati:n (e.g., cestru:-ive, ec :. :urrer.: :*0:e, boroscope, mecharical gage) accor:anie: by cualification of
~
those r.e: hods.
Characterization of the exarined guice -'obes, includin; ne'r in-core locations, EFPHs, # low rates, #13ence, and wear tire under rocs (control, instrurent, axisi-power sha:ing, buenable Doison, startup source, and cri# ice).
c.
Exarination of those rods (contrci, 'as trv ent, axial-:cwer s,ating, t.;r.atie ::iser., start.:: 50. :e, ard or'# ice) ::
i' ed
'-.r - e g,'
5 t,:es0;ie 1 #;se, s!*ess 0 ##:s#:-
q 152/
z88
2 cracking, wear, denting, er ar.; etner cea.c'. ions tnat car.
degrade their design func-ion, reduce tne' cesigr. lifet-e, or im:ede tneir novecer.t.
d.
Analysis of results including cuar.:ifica:icn of guide tube wall wear deoth and distribution. This :IE orcgram may be satisfied in part of totality by reference to data taken from another B&W designed clant(s) that.uses the same tyre of fuei assemblies.
In such case, justification mus be given that wear in the referenced plant adecuately represents that of the plant design in cuestion.
Provide all correlations supported by your tests and discuss how these correlarions are used to predict guide tube wear during reactor operations over the fuel lifetime.
2.
Provide an evaluation on the credicted guide tube wear on the stress analyses contained in the FSAR.
The evaluation snould
.s address loadings associated with Condition-1 thr:v;b 4 events 4
inclucing fuel handling accidents, contrei roc sc*srs, and seismic and ' CG trar.sients. The discussion sho ld descrice
.E state o#
stress in the worn guide tubes anc hcw :ne wea-a'fects ne loadbearing characteristics of tne worr, tubes.
(Note tnat nonuniform wear results in a shift of the neutral tube axis wt.ich then induces not only direct stresses but also bending stresses.) Show that the loadbearing capacity of the worn guide tubes satisfies the accectance criteria for these loading events.
3.
Drevide or reference all material preperty correlations tnat are used in the guide tube stress analyses.
These correlaticns should acconmodate the effects of hycrogen absorotion and the procensity for hydrogen ur.ake in the Zircaioy guide tubes as a function of accuru'.Stive wear -
P00fguy t
1527 289
~
3-a.
Address the consequences of hole fc-mation in wor ;JiCe tubes.
Consider-the extent and cistributic-cf wear to see if.cle formation is possible.
If the potential for hole #crea-ion can-not be discounted, evalua e the im;act of such nc'.es er the guide tube integrity,. control rod motior and loca! ther al-hycraulic performance. This evaluation should accoun-for #iow-induced vibration resulting in crack propagation and possiole fatigue frac-ture 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.
9 1527 290