ML20002A111

Sleeved Fuel Assembly Insp Results at Calvert Cliffs Unit 1, Nonproprietary Version

ML20002A111
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Site:	Calvert Cliffs
Issue date:	05/31/1979
From:	ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
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ML20002A110	List: ML20002A109 ML20002A111
References
CEN-111(B)-NP, NUDOCS 7906040250
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4 CEtt-111(B)-flP Sleeved Fuel Assembly Inspection Results at Calvert Cliffs l'ait 1 flay, 1979 J

l Combustion Engineering, Inc.

fluclear Power Systems Windsor, Connecticut 1

7906040260

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LEGAL NOTICE 3

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THIS REPORT WAS PREPARED AS AN ACCOUNT CF WORK SPONSORED f i

BY COMBUSTION ENGINEERING, INC. NEITHER COMBUSTION ENGINEERING . [

l NOR ANY PERSON ACTING ON ITS BEHALF:

, t A. MAKES ANY WARRANTY OR REPRESENTATION, EXPRESS OR IMPLIED INCLUDING THE WARRANTIES OF FITNESS FOR A PARTICULAR -

I PURPOSE OR MERCHANTABILITY, WITH RESPECT TO THE ACCURACY, {

COMPLETENESS, OR USEFULNESS OF THE INFORMATION CONTAINED IN THIS i REPORT, O,R THAT THE USE OF ANY INFORMATION, APPARATUS, METHOD,  !

OR PROCESS DISCLOSED IN THIS REPORT MAY NOT INFRINGE PRIVATELY  !

OWNED RIGHTS;OR (

l B. ASSUMES ANY LIABILITIES WITH RESPECT TO THE USE OF, OR FOR  ;

j DAMAGES RESULTING FROM THE USE OF, ANY INFORMATION, APPARATUS, L METHOD OR PROCESS DISCLOSED IN THis REPORT. . . . . .

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SLEEVED FUEL ASSEMBLY INSPECTION RESULTS AT CALVERT CLIFFS UNIT I

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MAY., 1979 I. INTRODUCTION During the current refueling at Calvert Cliffs Unit 1, an extensive ECT inspection program was conducted to ascertain the 4

I, condition of sleeves in assemblies located under CEA's during Cycle 3. No indications of sleeve wear were found in any assembly. However it was found that several guide tube sleeves

• did not exhibit the expected resistan:e to axial motion. These anomalies wyre detected during sleeved fuel assembly inspections.

The purpose of this document is to provide a summary of the observations made on sleeved fuel assemblies and the remedial actions which have been taken to insure proper operation in reactor.

Although a small amount of axial motion was observed during the sleeve pull testing on some fuel assemblics described in the following sections, it should be noted that a core scan at the end of cycle 3 operation detected no improperly positioned sleeves.

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II. Guide Tube Eddy Current Testing Results

- At Calvert Cliffs Unit I. Eddy Current Testing of sleeved l l CEA guide tubes was performed for the purpose of detecting any service induced wear in the sleeves. The inspection 1 was performed on May 6, 1979 in accordance with C-E Procedure No. 00000-ESS-134. Atotalof[)sleevedguidetubeswas inspected. No indications of wear were observed in the test data for the sleeved guide tubes. The portion of the sleeve i inspected for wear extended from "

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.,of the sleeve. Table II-l lists the assemblies inspected al,ong with the test results.

For all five guide tube sleeves in assembly D030, signals 1 from the crimp region of the sleeves were less than those i

{ observed for all other sleeves inspected for wear.

4 In assembly 0036, a signal indicative of an underexpansion ripple was observed in the southwest guide tube approximately 2" from the bottom of the sleeve.

1 The unsleeved assemblies, BT03 and C026, were inspected in accordance with C-E Procedure No. 00000-ESS-097, Revision 2.

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BT03 was the ccnter core assembly under a CEA and the latest

! inspection results indicated no additional wear occurred during i the last cycle. C026 contained a flow plug in the latest cycle and no wear indication was observed.

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. TABLE 11-1.

( CALVERT CLIFFS - UNIT I SLEEVED GUIDE TUBE ECT WEAR INSPECTION e

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II. (cont.)

i During the course of the wear inspection program, Eddy Current Test signals for the crimped region of the sleeve with widely varying magnitude were observed. The Eddy Current Inspection j Program was then extended to assess the crimp size in a variety i

of different category fuel assemblies. The inspection for crimp assessment was done using the same probe and test procedure as

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v was used in the wear inspection program. A correlation

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bItEeeneddycurrenttestsignalamplitudeandcrimpsizewas

! dett i..ad from the following pieces of information: _

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i l 3he ranges of estimated crimp size observed is tabulat,ed in i Table II-2.

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! A total of; , assemblics were designated for recrimping, using the new style crimp over the previously made olo style crimp.

An coq' current test was performed on each, after recrimping, to measure actual crimp size.

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SUMMARY

OF CRIMP SIZE ESTIMATES i

i BASED ON EDDY CURRENT TEST RESULTS i

a Crimp Return l Size Range to Core Under j, Number of -

i Category Batch Assemblies Mils Diameter CEA's Next Cycle i No 1 . Irradiated Unworn A I C No Sleeved (Old Style 1978 Cri 'mp) D* ies j

Irradiated Unworn Yes

! D, j Sleeved 1979

) (New Style Crimp) t Non-irradiated Unworn .. E Yes**

i Sleeved in 1978 (Old Style Crimp)

Recrimped 1979 D* Yes (New Style Crimp Over _

'; Old Style Crimp) 1-i r ~

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arc the same assemblies in the two categories

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! **( l assembly does not go under CEA during Cycle IV.

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III. Sleeve Pull Test Summary Pulltestswereconducteduponthesleeveso[

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fuel assemblies was that these assemblies where sleeved in 1978

- in the irradiated condition and are going under CEAS for cycle c ,-

4 operation. In

. In all other sleeves, some upward motion of varying magnitude ,

was observed.

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! Movement of the control rods is the only significant source of i

axial force on the sleeves in the cold condition. Recent tests

'I involving measurement of drag force between irradiated control

rod assemblies and sleeved fuel assemblies have shown this force 7

to be less than; Jtotal for the five control rods in the assembly. These tests confirm previous laboratory tests.

This information was not available at.the time the original 7- ,

pound requirement was set (approximately ). When the undersize crimps were discovered, the more realistic, yet still conservative,( fpound test per guide tube was established i~ in an effort to segregate the bundles ;ct.ording to the ability of the sleeves to resist movement under anticipated loads.

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Sleeve Pull Test Summary Continued

.[' ,Thc followin acceptance criteria were established

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The minimum upward force to move a sleeve was not specifically measured.,

However, in one instance a pound force did move the southeast

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a 5.leeveofD037 upward ( _ inch which was the maximum possible travel of the removal tool. With another tool and with approximately L -

pounds upward force, the northeast sleeve in 0030 was moved up approximately( inches, which was the largest

, upward movement observed during pull testing.

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i i' *It was later decided to recrimp all sleeves that were

, pull tested.

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IV.

SUMMARY

OF MECHAtlICAL PROPERTIES Af!D HOT CELL RESULTS TO QUALIFY RECRIMPING. t Irradiated Mechanical properties As background for the proposed sleeve re-expansion prograui, the strain capability characteristics of irradiated cold-worked Type 304 stainless si. eel and annealed Zircaloy have been reviewed.

- The elongation in uniaxial tension testing is considered a conservative -

measure of the materials ductilities .iith respect to accepting the i; expansion without any deleterious effects.

Type 304 Stainless Steel N on the room temperature mechanical Publ.ished data l properties of irradiated cold worked Type 304 stainless steel as a l

function of fast neutron fluence (E >l Mev) indicate 2 that the effect of '

n/cm . The saturation irradiation saturates at a fast fluence of 10 value for room temperature total elongation between this exposure and 21 2 the maximum tested of 1.5 x 10 n/cm is 5%. t Annealed Zircaloy ,

i A review of room temperature total elongation data (6-14) for irradiat,ed annealed Zircaloy as a function of fast fluence (E >l Mev) l i

indicate,s the minimum ranges from 4T to 8% in the fast fluence range 21 2 of interest,1 x 10 21 to 4 x 10 n/cm ,

Conclusion _

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Availaole data on the room temperature ductilities of the l irradiated sleeve and guide tube materials show that the proposed re-expansions to a n'aximum of[ )llowed by the snacification are ,

L acceptable. ,

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s Hot Cell Expani .on Tests To demonstrate the strain capabilities of the irradiated

sleeve and guide tube materials, expansion tests were performed at the Battelle-Columbus Laboratories hot cell facility on an intact sleeve and a sleeved guide tube section removed from a previously irradiated fuel assembly.

A hydraulica.'.y operated elastomer tool, similar to that used in the . . ,

field, was enplcyed. The specimen description ar.d locaticn of the  ;

expansions in the high fluence exposed regions of the specimens are listed in Table 1 along with the final diametral strains achieved during the tests. ,

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Fical strains of and((.[)w'erereachedinthesleeved- ~~~

guide tube section. exposed to fluences comparable to that of typical ,

sections to be re-expanded in the field. To demonstrate the ductility of the Type 304 stainless steel sleeve alone, the highest fluence exposed location.available was strained to{[, [ without visible defects.

t l A visual examination of the expanded regions of the sleeve and sleeved-guide tube section was then conducted with a binocular microscope up to a magr.ification cf 30X. The sleeved-nuide tube section was clamshelled to expose all surfaces for the ex mination. No crackina or other unacceptable defects were found.

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These hot cell tests, therefore, canfirm that irradiated _, __

sleeved guide tubes can be re-expanded to the specification limit ofl L. J l without any deleterious effects.

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. . . Table 1 .

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Hot Cell Expansion Tests of Irradiated Sleeves and Guide Tube .

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' Expansion Location Fluep~ceExposure Final Diametral in. From Sleeve ~n/cm (E >0.82 Mev) Strain, f, Sleeve Zircaloy Scecimen Description Bottom  ;

1-1/4 0.8 x 10 -- ( )

304SS Sleeve 3 0.6 x 10 21 __

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5-1/2 0.4 x 10 --

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i 21 0.6 x 10 21 .j ,4 x,10 ( ]

Sleeved 3-3/8 21

Guide Tube 7,-1/8 0.5 x 10 21 1 06 x 10 [ ]c, Section .

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REFERENCES ,

(1) A. L. Bement et al., Irradiation Damage to Stainless Steel s, Report HW-70962 (1962) S. 4.73 ff.

(2) J. E. Irvin, A. L. Bement, R. G. Hoagland, ASTM-STP-380 (1965)

S. 236 ff.

(3) J. E. Irvin, A. L. Bement, ASTM-STP-426 (1967) S. 278 ff.

(4) R. E..Rcbbins, J. J. Holmes, J. E. Irvin, ANS Trans. 10, (1967) 488. .

(5) A. J. Lovell, AflS.Trans 11.(1968)482.

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B. A. Cheadle, C. E. Ells, and J. Van der Kuur, " Plastic Instability in Irradiated Zircaloy-Sn and Zircaloy-Nb Alloys", Zirconium in Nuclear Applications, ASTM, STP 551, 1974, pp. 370-384. . . . .

(7) W. R. Smalley, " Effects of Irradiation on Mechanical Properties of ,

CVTR Pressure Tube Material", CVNA-159, September 1962.

(8) A. R. Kaphart, " Review of Selected Physical and Mechanical Properties I of.Zircaloy-2", Trans. of ANS, Vol. 4, No. 2, November 1961, pp.194-197.

L (9) B. 'Lustman, et al . , "Zircaloy Cladding Perfonns Well in PWR",

i Nucleonics, Vol .19_, No. l . , January 1961, pp. 58-63.

(10) Coplin, D. H., et al., " Mechanical Property Changes in Zircaloy-2, Inconel and Incaloy for Neutran Exposures to 2.5 x 1021 (above 1 MeV)"

. GEAP-51009.  ;

' (11) H. E. Williamson and Dana C. Ditmore, " Current BWR Fuel Design and-

Experience", Reactor Technology, Vol .14, No.1, Spring 1971.

t (12) L. M. Howe, "The Annealing of Irradiation Damage in Zircaloy-2",

1 AECL-1024,1960.

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- (13) D. G. Hardy, "The Effects of tieutron Irradiation on the Mecht nical Properties of Zirconium Alloy Fuel Cladding in Uniaxial and Biaxial Tests", Irradiation Effects on Structural Alloys for Nuclear Applications, ASTM-STP 484, 1970, pp. 215-258.

(14) D. G. Hardy, " Burst Testing of Zircaloy Cladding From Irradiated

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Pickering Type Fuel Bundles", Effects. c'f Radiatiori'bn Substructure

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and Mechanical Properties of Metals and Alloys, ASTM-STP 529,~-

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1973, pp. 415-434.

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V. RECRIMPIflG PROCEDURE A. Recrimping of sleeved guide tubes is accomplished with the I

)elastomercrimpingtool. This is the same tooling utilized for all recent sleeving operations. In addition, crimping operations performed in the hot cell on e i aited quantities of irradiated guide tube and sleeve material (see Section IV) indicated a higher crimping pressure

] than had been required on previous tests. In

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- ' earlier site crimping operations at [

_ ] with fresh (unirradietad) sleeves and the;- ,

style elastomer, life and qualification of the elastomer became a major problem, leading.to the development of the elastomer crimp process. The higher crimp presst.re required for use with irradiated guide tubes and sleeves precluded use of the old style ] elastomer. Figures V-1 and V-2 depict the elastomer,( style elastomer differences between(

and recrimped sleeve configuration.

The "recrimping" location is within the{ of the original crimp. Bench tests of unirradiated material have crimp can be produced for a demonstrated that the(

- variation of initial crimp diameters, ranging from low values, as observed in some CC-1 fuel, to values up to and including

( ], without affecting sleeve end geometry (See Section VI).

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V. (cont.)

's Because the recrimp is positioned at some distance F 1 jfrom the bottom of the sleeve, a w

second operation, in which the bottom is re-expanded

' against the guide tube wall, was also performed. This operation, together with a free path gauge : heck insures

• that the end of the sleeve does not interfere with CEA insertion. The procedure for recrimping guide tubes sleeves

,.that have been previous ly crimped is C-E Procedure 8067-ESS-144, Rev. O, dated 5/17/79.

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l Figure V-1:I Elastomer Crimp Configuration

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Ficure V-2: Elastonce over Crimp Configuration l

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! VI. ACCEPTABILITY OF Tile GE0 METRY OF Tile RECRIf1P Bench testing was completed on 14 x 14 guide tube and sleeve "

i samples to determine effects on sleeve and guide tube geometry i

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by installing a second crimp over a previously. installed crimp.

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'he results show that the new style - - 3 jwithout crimpcanbeinstalledoverthef ,

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" rolling in" the end of the sleeve, or causing any other i ..

1 anbmalies in geometry.

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Inspection of all samples showed no effects on geometry by l

installing a-[, ]crimpovera( crimp, except for a slight shift in the maximum 0.0. location. The tests show

! no need for an additional iower end expansion, however, 1

this procedure is retained in field crimping operations to

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preclude any chance of sleeve edge protrusion.

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For the actual recrimps placed in the fuel assemblies in f

j question, all sleeves have been eddy current tested and

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shown to have crimp sizes sufficient to prevent axial i

> motion (see Section XIII).

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Section VII Sleeve Withdrawal Evaluation .

Assembly D030

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l Initial attempts to remove a sleeve from fuel assembly D030 resulted in moving the sleeve upward approximately _

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i before reaching tool pressure limitations. At this position, 3,

the total applied force was approximately ,

A second attempt to remove the sleeve was made after evalu-ation of possible causes for the above results. It was thought that the gripping portion of the tool could be pushing the

' sleeve against the Upper End Fitting post inside diameter and thereby creating a high friction force. The second attempt l

i placed the gri iper in the portion of sleeve above the upper end j

fitting post.

The sleeve was successfully removed during the 4 -

r second attempt with an average withdrawal force of{

and a maximum of The latter value was observe I l when the sleue crimp region entered the upper end fitting  ;

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post.

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VIII. ECT and Visual Inspection of Recrimped Fuel Asserrblies After the recrimping process was completed, all guide tubes were eddy current tested. Based on the eddy current testing l

described in Section II, the maximum strain induced during f

the recrimp was [ ]. As discussed in Section IV, recrimps *

] are deemed acceptable. It is concluded to a maximum of [

that a sufficient margin of safety exists between the strain

• induced as a result of the recrimp and that strain required io'causecracking. Therefore, no visual inspections were performed on the recrimped fuel assemblies during this refueling outage.

Similar conclusions were verified during the Calvert Cliffs Unit 1 and Millstone Unit 21978 refueling outages. At that time,atotalof(sleevedfuelassemblieswerevisually inspected. fio evidence of guide tube cracking was observed.

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l IX. Discussion As To Why Pull Tests /Recrinping Need Not Be Done For f Non-CEA Locations I

In CEA locations, axial load: may be imposed on the wear sleeves-as 4. result of the drag > force' due.to.CEA movement. To ensure that the sleeves do not move up during operation, pull tests and In ac.

recrimping of the. sleeves in bundles was done as required.

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non-CEA location, the CEA drag force-does not exist, and.the only axial load which the sleeves must withstand without axial movement is the drag force on the sleeve due to the coolant flow up,the guide tube which is not significant.

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Upon heatup to operating conditions, the sleeve and guide tube come into contact in the expansion region with a resulting interference fit due to differential thermal expansion. The magnitude of the interference depends upon the installed cold diametral gap between the sleeve and the guide tube, and the amount that the guide tube and sleeve relax during operation. Based~ on the maximum allowable and the maximum expected installed cold diametral gap, _

relaxation over two cycles of operation , the interference i

at operating conditions is sufficient to preclude axial movement of the sleeves due to loadings in CEA: and non-CEA locations.

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X. Could Fretting Be Occurring If A Sleeve Were Loose In A

' Non-CEA Location 4

As explained above, there will be an interference fit between the sleeve and the guide tube at operating conditions that precludet

! - axial movement of the sleeve due to hydraulic forces, and similarly, Therefore, precludes fretting by restricting any lateral movement.

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the.only time when fretting could occur would be during the heatup and cooldown operations. Since these operations are of short duration,

' - it is concluded that no significant fretting will occur between the sleeves and the guide tube.

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) XI. Inspection of D046_

'After the recrimping process was completed, it was observed that the top of the sleeve installed in the center guide tube was raised inch above the fuel assembly post. It was concluded that the j u

} pull test did not lead to this condition. The raised sleeve may tie unsatisfactory since a' scrammed CEA would impact the sleeve durinq reactor operation. It was decided that the most prudent course of action i da to place D046 in a non-CEA location (core location F6). In i a non-CEA location, there will be no interference between the l

raised' sleeve and any reactor internals during reactor operation.

The origina1 cycle 4 position designated for 0046 (core location f

J N18) was replaced with 0026 which is an unworn sleeved fuel assembly, a

D026 was originally designated to be in core location V9 for cycle i

4 operation. D014 which was to be in core location F6 for cycle 4 was moved to core location V9 to replace D026. Fuel assembly i D014 is an unsleeved fuel assembly which sustained wear during Cycle 2. The wear observed during Cycle 2 in location V9 is Judged to be sufficiently low, in conjunction with the current 3

condition of D014, to allow operation during Cycle 4 without l

i sleeves in 0014 since the CEA in that location will be positioned

• inches below the fully withdrawn elevation.

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Tha three bundle substitution was used, as opposed to a two bundle substitution, to place the non-sleeved fuel assembly under i

a CEA in a low wear region of the core to ensure that none of the l  !

l guide tubes will violate their allo.nble irradiated stress limits 1

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XI. Inspection of D046(Continued) or sustain sufficient wear to form a hole in the guide tube. This course of action places D014 in the same category as fuel assembly BT03; i.e., a non-sleeved fuel assembly under a CEA in a low wear position.

• This three bundle substitution has been analyzed to have a minimal 6ffect on the fuel management and should not adversely affect physics peaking.

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la s XI. -(cont.)

j In summary, as a result of the raised sleeve observed in the fuel assembly

) D046, the following core modifications have been made:

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I J Original New i Loca tion _ Status j, Fuel Assembly Location _

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F6 (non-CEA Sleeved, unworn D046 N18 location) r Sleeve raised inch l

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V9 (CEA Unsleeved; low ,

i 0014 F6 location) wear received

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N18 (CEA Sleeved, unworn 0026 V9 location) l l

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XII. OPERATIOllAL CUIDELIf1ES

.As explained in Section II,-the fuel assemblics wh,ich had sleeves with abnormally small crimps t .,

were included in a particular category (sleeved in 1978 in the irradiated cendition). Ilowever, other categories of fuel do exhibit crimps which are undersized to a lesser extent.

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+ At the startup of Cycle 4, all sleeves supply adequate resistance

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.t6siial motion in CEA locations, based on the following:

The ef fects of irradiation in Cycle 4 will be to cause relaxation, or continuation of relaxation, in the guide tube and sleeves. To preclude the possibility of sleeve movement during later shutdowns, it would be prudent to restrict movement of control rods at system temperatures below .

The basis for this temperature is that ,

it is a conservative minimum temperature at which the sleeve crimp diameter will exceed the guide tube I.D. in the non-crimp region.

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XIII. Discussion of Crimp Size During hot operation, the differential thermal expansion between

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the stainless steel sleeve and zircaloy guide tube wiii cause the two components to be in intimate contact over the expanded length of the sleeve l ( ~

inches in control rod locations). The(]milmaximuminstalled gap between the two was set to ensure this condition.

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The minimum outward crimp cf the sleeve was originally chosen as a conseryative size that would prevent withdrawal of the sleeve upward thru thb non-crimped region cf the guide tube. Realistically, crimps as small as )are capable of performing this function e e n af ter long term operation (since the cold gap would not exceed the( differential thermal expansion, even with relaxation values approaching _

j) . This appears to be the* case from the pull test data from hillstone 2 and Calvert Cliffs 1:

a. At Millstone 2, three sleeves with ,1 crimps and one sleeve with a

{ )rimp were pull tested, and silowed no movement at net loads in excessof[] pounds.

b. At Calvert Cliffs 1, where the sleeves that were pull tested had crimps

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_ ranging from ] mils,movementwasdetectedforcrimps.ofupto mils.

m Therefore,the({ ysize has been established as the minimum crimp that-prevents sleeve movement under cold CEA operation. For sizes less thar.

mils, current evaluation of the data would indicate operational guide-

. ([lines to limit control rod movement are prudent (see Section XII).

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" These guidelines refer to a minimum system temperature for control rod movement, which is based on the temperature required to ensure interference between the sleeve crimp and the non-crimped guide tube I.D.

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XIII. CONCLUSION It is concluded that Calvert Cliffs-Unit 1 sleeved fuel

. assemblies-will operate properly during Cycle 40-This 9 conclusion is based on the,following observations: .

1. The anomaly of abnormally small crimps observed at Calvert Cliffs Unit 1 during.the current refueling c'00tage has been isolated in thi cycle 4 fuel category to Batch D fuel assemblies sleeved in.1978. .

I 2. Based on the operational guidelines imposed by Section XII, coupled with the reworking of Batch 0 fuel assemblies exhibiting the above anomalies-and returning to CEA locations for cycle 4, these sleeves are captured in the guide tube 'and will not move axial.ly during reactor operation under both hot and cold conditions even after thermal cycling and irradiation.

3. The Batch D crimp size after the recrimping process is comparable to those crimp sizes in Millstone Unit

1. Number 2 fuel assemblies which were satisfactorily pull tested af ter one cycle of operation.

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XIII. (cont.)

4. For all other categories of sleeved fuel assemblies in cycle 4, either eddy current sampling and/or pull testing was performed to insure adequate resistance to sleeve motion during cycle 4 startup. The restrictions imposed by section XII precludes sleeve movement during the remainder of cycle.

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5. ,.Fqr non-CEA locations, the sleeves are captured in the cold condition by the fuel alignment plate and in the hot condition by differential thermal expansion with the guide tubes. This capturing of the sleeve would preclude any possibility of fretting.

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