ML20127L885

Forwards Results of Engineering Evaluation of Design Changes Introduced in CRD & Orifice Assembly Bearings.Physical Comparison Testing of Original & Replacement Shim Motor Bearings Underway to Establish Operating/Design Margins

ML20127L885
Person / Time
Site:	Fort Saint Vrain
Issue date:	06/13/1985
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
P-85201, TAC-55294, NUDOCS 8506280187
Download: ML20127L885 (26)

Text

-

O PublicService e-e s.-.

Company of Colorado 16805 WCR 19 1/2, Platteville, Colorado 80651 June 13, 1985 Fort St. Vrain Unit No. 1 P-85201 Regional Administrator Region IV U. S. Nuclear Regulatory Commission g l 45 li ton a bil j Attention: Mr. Eric 11. Johnson Docket No. 50-267

SUBJECT:

Engineering Evaluation of CRDOA Bearings

Dear Mr. Johnson:

Enclosed are the results to date of the engineering evaluation of design changes, introduced in the control rod drive and orifice assembly bearings. The report includes analytical investigations as well as physical tests data for the original and replacement bearing designs. The findings indicate the replacement bearings perform comparably to the original bearings, and as such are suitable for use in the control rod drive and orifice assemblies at Fort St. Vrain.

Mathematical analyses were performed by GA Technologies and Industrial Tectonics to determine contact stresses between bearing components for both designs. Though calculated stresses in the replacement bearings showed slight increases, ranging from 3 to 7 percent, all stresses were below the original design allowable contact stress of 368 ksi. Standard lifetime calculations, though not entirely applicable to the dry film lubrication technique used in the bearings, predicted cyclic life for all bearings in excess of the g life of the plant. i a

C d

/bC e506280187 850613 PDR ADOCK 05000267 y

b()b P PDR l[

, :e-

~ Physical comparison testing of the original'and replacement shim motor bearings is' currently underway at.GA Technologies and Fort St.

Vrain. Initially, original and replacement bearings were tested at

-GA Technologies and SKF Industries on test rigs under simulated load conditions. The cyclic lives exhibited by both types of bearings, though , comparable, were below the design life requirements.

Subsequent modification to the GA Technologies test rig has resulted in greatly improved bearing' performance. In the first test following-

' modification, replacement bearings have completed two life cycles with no indication of bearing degradation. Given the successful performance. of the GA Technologies test rig, we made a decision to discontinue any further testing at SKF Industries.

In an effort to better simulate application loads, bearing tests at Fort St. Vrain have started in which replacement bearings installed in a- control rod drive are being cycled via repeated scrams and withdrawal of the rods. In another test, replacement bearings

. installed in a shim motor mounted on a test stand have completed two

-(2) test cycles with no indication of - degradation. The successful completion of a . test cycle in these tests demonstrates that the replacement bearings fulfill their design function.

We plan to ~ continue- the.above outlined test programs to establish operating / design margins for the bearings. We will provide you with J further. information upon completion of the test programs.. In the interim, the attached report provides engineering analysis and test data demonstrating the acceptability of the new CRD0A bearing designs-in the overall. performance of the control rod drives.

If you have any questions, please contact Mr. M. H. Holmes at -(303) 571-8409.

Very truly yours, h f- (Yuu l D. W.- Warembourg-l Manager, Nuclear Eng.

i- Division

! DWW/BEB/ksc h Enclosure i

e

Abstract a 9

-In January, 1985, a program to rafurbish Fort St. Vrain control rod drive and orifice assemblies (CRDOA) was undertaken after six units failed to insert automatically during a reactor scram. As part of the refurbishment program, new ball bearings were ordered to replace the used bearings in these CRD0A's. Several discrepancies between the bearings supplied and the purchase specifications were noted, prompting an engineering evaluation of the design changes.

Independent mathematical analyses by GA Technologies and Industrial Tectonics, Inc., determined that contact stresses in the replacement bearings exceed values calculated for the original bearings, but are still within acceptable limits. Standard life cycle calculations, though not directly applicable to dry film it.bricated bearings, predict fatigue lives well in excess of the life of the plant for the service loads expected on the bearings.

Physical testing of the original and replacement shim motor bearings under simulated loading conditions, conducted at GA Technologies and SKF Industries, Inc., produced comparable lifetimes for both bearing designs. Additional testing under actual load conditions is currently underway to provide more realistic comparative data.

l

. .,. y

I. INTRODUCTION .

A. System Description and-0perating Environment.

The control rod drive system at. Fort St. Vrain consists of 74 control rods operated in pairs by 37 CRD0A's. Each CRD0A

resides in a refueling . penetration .in the tophead of the

. Prestressed Concrete Reactor Vessel (PCRV). The control' rod drives are located within the pressure boundary of the PCRV,

-and as.such, operate in a dry helium environment at reactor

. pressure. Radiation exposure is limited by shielding to one rad per-hour.-

Each -CRDOA is' composed of a control rod drive mechanism and an orifice valve assembly. The control rod drives raise and lower the control rods to moderate nuclear reactions in the core. The rods are hung cables 'which spiral-wind onto a cable drum assembly. The cable drum meshes with a 3-stage, 1151:1 reduction gear train driven by an electric shim motor.- 'The cable drum, . gearing and motor shafts .are supported by 14 anti-friction, dry film lubricated ball bearings. The orifice valves control coolant flow from the refueling penetrations into core. Dry film lubricated

. bearings .are used to support the gearing and drive mechanisms. The use of dry film lubrication in the control rod drive and orifice valve bearings is dictated by the environmental operating conditions.

The ball bearings in the CRDOA are assembled from commercially available balls and raceways and custom cages designed to incorporate dry film-lubrication. Inner and outer raceways are manufactured from AISI 440C stainless steel, which was selected due to its high corrosion resistance and hardenability. Seven of. the nine bearing designs used 440C stainless steel balls as well, with ball cages fabricated from 17-4 PH steel. Materials in the shim motor and first stage bearings were changed to. increase wear resistance. Tungsten carbide balls and cages made -of a surface-nitrided nitralloy' 135M material were used to i accommodate the higher duty cycle of these bearings.

L Lubrication in the CRDOA bearings was applied in the fonn of a dry molybdenum disulfide powder, which was burnished into the raceways and ball cage pockets. The shim motor bearings

!, were further modified to incorporate a reservoir of dry film

~ lubricant, consisting of two s'intered bronze rings impregnated with' molybdenum disulfide which press fit into the cage. The lubricant is deposited on the ball surface as L

the ball wears against the sintered bronze' rings.

Two other bearings are included in the CRDOA which support i position indicating potentiometer shafts. These' are small

! - commerical ' instrument bearings which operate at extremely low shaft speeds. Dry film lubricant is applied to these

bearings via dusting during run-in.

[ l

. i B. Design Changes During Refurbishment ,

Following an incident on June 23, 1984, in which six of the control rod drives malfunctioned, a program was initiated to refurbish each control rod drive and orifice assembly. As part of this program, Public Service Company contracted with GA Technologies, who sub-contracted with Industrial Tectonics, Inc., to manufacture replacement bearings under existing specifications for all CRD0A bearings except potentiometer drive bearings. The races used in the original bearing design were apparently not available when the new bearings were ordered, so races with equivalent external dimensions (bore, width, and outer diameter), but different interior dimensions were substituted. In an effort to -maintain functional equivalence, clearances and tolerances between internal bearing components were kept as similar~ as possible to those in the original bearing designs. A complete list of dimensional discrepancies between the original and replacement bearings appears in Appendix A.

C. Engineering Approach to Design Change Evaluation

.The design changes to the CRD0A bearings have been evaluated using analytical techniques and physical testing. The objective of the evaluations was to compare the abilities of the modified bearing designs to perform their design function of maintaining control rod operability. The analyses were directed toward the shim motor bearings, based on the following observations. The potential for these bearings to fail or inhibit rod drive operation is greater than any other bearing due to maximum life cycle and minimum allowable drag torque requirements. Furthermore, it was demonstrated that the complete failure of a second stage result bearing (totalinstallation of improper disassembly)of bearing would internals not prevent theasrod a drive mechanism from scramming. In addition, in the developmental and qualification testing and in operating experience to date, no evidence of failure in any bearing other than the shim motor bearings has been observed.

The design parameters considered critical in assessing bearing performance are applied loads, internal geometry (which affects load and stress distributions), materials, and lubrication. The design load calculations and cyclic life requirements are discussed in Section II of this report. Analytical techniques used to calculate contact stresses and fatigue lives of bearings and the results of these analyses are presented in Section III. The materials used in manufacturing the replacement bearings conformed to

. o the original specifications, with the exception of the sintered bronze material used in the shim motor ' bearing lubricsnt reservoir. The original specifications called for a material manufactured under the trade name of "Bearite" to be used, but this is no longer produced. Therefore, a material of comparable chemical and physical properties was developed for use-in the replacement bearings. To evaluate the lubricating ability of the replacement material, -

physical testing of original and replacement shim motor bearings is being conducted in which the cyclic life of both bearings under design loading is compared. The test programs and results to date are presented in Section IV of this report. Cyclic testing was also performed on potentiometer drive bearings to-determine post-refurbishment operability. In the refurbishment program, these bearings were decontaminated and reinstalled without re-lubrication.

New unlubricated bearings were tested in a helium atmosphere under a 1.2 lb. radial load. The completion of 5 test cycles with no evidence of an increase in drag torque indicates any effects of decontamination on lubrication will have no significant impact on the operability of these bearings.

II. DESIGN LOAD AND LIFE REQUIREMENTS The design loads for the CRD0A bearings are calculated in GADR-10, Design Report for Control Rod Drive Mechanism. (Ref.1)

Norcel operating loads are determined for each shaft in the mechanism by static load distributions. Maximum loads on duplex bearings are calculated based on an 80/20 percent distrbution.

In addition, dynamic loads on shim motor bearings are calculated for stopping and starting the mechanism. The maximum design

. loads are as follows:

CRDM LOCATION GA PART NUMBER RADIAL LOAD (LBS)

Cable Drum Duplex SLR-D1201-260 616.9 lbs.

Cable Drum Simplex SLR-D1201-259 162.5 lbs.

3rd Stage Duplex SLR-D1201-258 440.6 lbs.

3rd Stage Simplex SLR-D1201-257 209.9 lbs.

2nd Stage Duplex SLR-D1201-261 236.2 lbs.

2nd Stage Simplex SLR-01201-256 78.2 lbs.

1st Stage Simplex SLR-01201-265 41.3 lbs.

Shim Motor Duplex SLR-D1201-222 12.2 lbs.(Normal Operating)

Shim Motor Duplex SLR-D1201-222- 50.8lbs.(Starting)

Shim Motor Duplex SLR-D1201-222

.~ 33.9lbs.(Stopping)

The radial loads imposed on the potentiometer drive bearings are negligible. -

~

w. ,

)

'\ ,

N.,

e

l The test cycle life requirements of the CRD0A are based on anticipated adjustments of the regulating rod. The estimated cycle duty for the regulating rod, per the system description (Ref.2), corresponds to one 2-second jog every 5 minutes, for a total of 86,400 jogs per refueling cycle. The regulating rod also moves during operating transients, at a rate of 7.5 jegs per minute for a 5% per minute change in power level. The frequency of operating transients for the plant was estimated to be one .

load swing per day from 100% power to 50% power and return (Ref.

5). Based on these figures, the number of jogs of the regulating rod due to operating transients for one refsaling cycle comes to 45,000 jogs. The total service duty of the re alating rod is the sum of these components, or 131,400 jogs per ref;eling cycle. To express this value in terms of shim motor bearing cycles, the average rate of 2.2 inches of rod vertical travel per 2-second jag is multiplied by an average of 28.14 shim motor shaft revolutions per inch of rod travel to arrive at the figure of 8.1 million bearing revolutions per refueling cycle for regulating service.

l The test cycle life requirements for the CRD0A's are very conservative in that the estimated regulating rod duty greatly exceeds shim bank duty and projected operating transients have not been realized in practice. The requirements are sufficient to demonstrate the desired reliability of the CRD0A to perform its function through one refuel cycle of regulating rod duty and five refuel cycles of shim bank duty.

III. LOAD / STRESS ANALYSIS i

A. Analytical Techniques Used in Bearing Analysis Analytical techniques used in rolling-element bearing design provide a means to predict the performance of a bearing in a specific application. Current standards are based on a fatigue life criterion, which is very sensitive to minor variations in material, geometry and loading parameters that occur within a given application. Consequently, performance standards are expressed in terms of " reliability", or percentage of failures of a group of identical bearings in a given number of cycles.

The fatigue life of a rolling-element bearing is governed by the hertzian stresses generated at the contact surfaces between the rolling elements and their raceways. Standard formulas exist for calculating these stresses as a function of material, geometry and loading parameters.

s i

Gulf General Atomic (now GA Technologies) used a maximum allowable hertzian contact stress of 368 ksi for the original bearing design calculations. This stress figure, which is equal to 1/3 the Brinell hardness number of the material, was based upon research described in NASA-SP38, Advanced Bearing Technology, (Ref. 3) which found that adhesive wear remains essentially constant for stresses up to this value.

The standard calculations of fatigue life and load rating for a rolling-element bearing are presented in Anti-Friction <

Bearing Manufactures Association (AFBMA) Standard 9, (Ref. I 4). These calculations estimate the theoretical number of cycles which a certain percentage of a group of identical

. bearings will endure under service loading without l exhibiting signs of fatigue. l 1

The AFBMA bearing life values are based upon oil lubricated i bearings and the expected failure mode is subsurface fatigue. For dry film lubricated bearings as used in the CRD0As, the failures are expected to be surface-initiated and as a result the AFBMA bearing life is not completely valid for these bearings. However, the life calculations do indicate the relative stress levels in the bearing since lower stress results in longer calculated bearing life if other variables such as material and lubrication factors remain constant.

B. Results of Stress Calculations Hertzian contact stresses were independently calculated by GA Technologies and Industrial Tectonics using their own computer programs. Variations in the results occur due to minor differences in load distribution over the ball complement and input material parameters.

The calculated hertzian contact stresses are as follows:

Analysis Performed by GA Technologies Original Bearing Replacement Bearing GA Technologies Max. Hertzian Max. Hertzian Percent Bearing Part Number Contact Stress (ksi) Contact Stress (ksi) Change SLR-D1201-222 (Steady Sate Shimming) 169.5 181.5 +7 SLR-D1201-222 (Motor Sta: ting) 272.6 292.0 +7 SLR-D1201-222 (Motor Stopping) 238.2 255.2 +7 SLR-D1201-256 235.0 242.5 +3 SLR-D1201-257 295.5 306.0 +4 SLR-D1201-258 335.2 347.2 +4 SLR-D1201-261 325.7 348.6 +6 SLR-D1201-265 254.4 272.6 +7 SLR-D1201-420 246.5 262.3 +6 Analysis Performed by Industrial Tectonics Original Bearing Replacement Bearing GA Technologies Max. Hertzian Max. Hertzian Percent Bearing Part Number ContactStress(ksi) Contact Stress (ksi) Change SLR-D1201-222 (Steady State Shimming) 149.3 143.1 -4 SLR-D1201-256 235.4 239.3 +2 SLR-D1201-257 284.0 257.0 -10 SLR-D1201-258- 316.3 294.4 -7 SLR-D1201-261 312.0 319.4 +2 SLR-01201-265 209.4 214.6 +2 SLR-D1201-420 251.1 271.5 +8 The GA Technologies analysis indicates that the maximum hertzian contact stresses increased in all bearings by 3 to 7 percent. The Industrial Tectonics analysis indicates that the maximum hertzian contact stress changes ranged from a reduction of 10 percent to an increase of 8 percent. Both analyses, therefore, show a relatively small difference 'in contact stress between the original and replacement bearings. The calculated maximum contact stresses of all the replacement bearings are below the original design criteria of 368 ksi.

I i

u

'C . Results of L10 Life Calculat' ions

~ Industrial -Tectonics performed bearing life calculations in

'accordance with- AFBMA Standard 9. The results are as

'follows:

Original Bearing Replacement Bearing GA Technologies L10 Life L10 Life L10 Life Bearing Part Number (Revolutions) (Revolutions)

SLR-D1201-222l 3.94 x.10 12 2.16 x 1012 SLR-D1201-256 .1.22 x 10 10 1.01 x 1010

-SLR-D1201-257 1.78 x 1 9 1.40~x 109 SLR-D1201-258. 5.21 x 1 4.16 x 108 SLR-D1201-261 1.06 x 1 5.82 x 108 SLR-D1201-265 1.02 x 10 1 5.57 x 1010 SLR-D1201-420 2.24 x 10 10 1.21 x 1010 The shortest computed replacement bearing L10 life is greater than 51 years of continuous operation for bearing part number SLR-D1201-261, based upon the in-service. speed of rotation of 21.64 rpm. Although the L10 life values are not directly applicable to dry-film lubricated bearings, the high L10 life figures listed above 'do indicate that the bearings are- very lightly loaded compared to their actual

-load capacity.

D. Conclusions for Mathematical Analyses As indicated above, the maximum hertzian contact stresses calculated for replacement' bearings are up to 8 percent higher than those calculated for original bearings.

However, the calculated contact stresses are below the maximum contact stress of 368 ksi' established i n' the original design. Therefore, the replacement bearings will be used within their load capabilities.

The L10 bearing life calculations also show that replacement bearings will be used well within their load capabilities due to the very long L10 life figures. Thus the load capacity of replacement bearings is adequate for the application.

.g.

o .

IV. COMPARATIVE TESTING OF CRD SHIM MOTOR BEARINGS A. Purpose'of Testing For dry film lubricated bearings the most common failure mechanism involves the loss of.. lubrication between internal components. Repeated contact between two unlubricated surfaces can cause microwelding and material transfer which reduces internal clearances and eventually causes bearing seizure. The lubricating characteristics of a dry film lubricated bearing are complex and difficult to establish by analytical techniques. In developmental testing, it was determined that the absence of or excess lubrication was

. detrimental to bearing performance. The lubricant reservoir used in the shia motor bearings was designed to introduce an adequate supply of lubricant to the bearing internal components.

To evaluate the impact of the design changes on the lubricating properties of the shim motor bearings, experimental test programs were initiated at GA Technologies and SKF Industries, Inc. In the tests, opposed pairs of original and replacement shim motor bearings were mounted in a test rig, loaded to the calculated start-up loads and run in a dry helium atmosphere. The torques transferred from the inner to outer races were monitored and compared to certain cut-off limits to serve as a failure criteria for the test. A cumulative drag torque corresponding to 15 oz-in at the motor shaft is required to stall the control rod drive during scram operation. A value of 30 oz-in was selected as the test cut-off point to explore bearing degradation rates beyond the stall point. The cbjective of the' tests was not to predict bearing performance in a shim motor installation, but rather to . compare the relative lubricating characteristics of the original and replacement bearings.

B. GA Technologies Test Program The GA Technologies test rig utilized pendulums into which the bearings were mounted to apply the radial load required.

The pendulums weighed 65 lb. each, corresponding to the calculated radial load (static plus dynamic) on the shim motor bearings during startup. Rotational displacements of the pendulums were monitored with proximity probes and equated to drag torques in the bearings. The drive shaft was run continously at 1730 rpm, corresponding to the shim motor speed during shimming operation. The test machine was capable of testing two pairs of bearings at once.

The rig was tested by running a pair of replacement bearings ,

and a pair of grease-lubricated bearings simultaneously. In this phase of testing, the bearings were run for individual periods of time ranging from 8 1/2 to 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> after which each time the rig was disassembled and inspected. A total of 67 hours7.75463e-4 days <br />0.0186 hours <br />1.107804e-4 weeks <br />2.54935e-5 months <br /> of intermittent operation was accumulated with no apparent degradation of bearing performance noted. This corresponds to approximately 7 million bearing revolutions or slightly less . than one test cycle. The torque measurements during this phase were inhibited by harmonic oscillations in the pendulum which required foam damping to be installed. Following the completion of this test, the pendulums were rigidly attached to force transducers to allow measurement of drag torque, and the damping material was removed.

A comparative test was then performed using two original bearings and two replacement bearings. The test ran for 29 hours3.356481e-4 days <br />0.00806 hours <br />4.794974e-5 weeks <br />1.10345e-5 months <br /> before one of the replacement bearings seized.

Subsequent inspection indicated axial vibrations in the weighted pendulums had caused detrimental axial loading of the bearings, as unusual wear patterns were observed in the ball track of the seized replacement bearing, and displacements of the press-fit lubricant reservoirs from their cage seats were noted in one of the original bearings.

The test rig was then modified to dampen the axial vibrations to acceptable levels and reduce the radial load to the normal operating value of 15.3 lb. per bearing pair.

In subsequent testing, a pair of replacement bearings have completed 16.2 million revolutions, corresponding to 2 full test cycles, with no significant increase in drag torque.

C. SKF Industries Test Program In the SKF Industries test rig, a single pair of bearings was mounted in a housing free to rotate, which was supported on a drive shaft. A radial load of 65 lbs. was applied by suspending weights from the housing. Drag torques were measured periodically by a force transducer coupled to the housing. The bearings were run in a helium atmosphere at 2450 rpm, corresponding to the shaft speed of the shim motor during scramming operation. The direction of rotation was reversed every half hour to resemble service duty in the CRD0A.

After the rig performance was tested successfully, a test was initiated using replacement bearings. The test ran for 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br /> before drag torque reached 30 oz-in. The radial 1 cad was reduced to 15.3 lb. and a new test with replacement bearings was started. This test lasted 6 1/4 hours before the failure criteria was met. A third test in which

.. w

<' - original bearings were run under a 15.3 lb. radial load was performed. This test ran for a total of 5 1/4. hours before the bearing torque reached 30 oz-in. Subsequent inspection of the failed bearings showed significant deposits of wear debris from balls, cages and races.

= D.- Conclusions-from Physical Testing In~ the experimental testing conducted at GA Technologies and SKF Industries, Inc., the performance of .the original and replacement shim motor bearings- has been roughly-equivalent.

The results of the testing are some what inconclusive in that total lifetimes exhibited by the test bearings range

.widely and do not correlate with the radial loads applied.

Significant differences in bearing performance occur between testing in a rig with simulated loads and actual operating experience - accrued in the history of the plant. In all the bearings removed from the CRD0A's during the refurbishment program,.-no indication of material transfer or significant deposits of wear debris have been noted.

The evidence indicates the loading conditions imposed on the test bearings are significantly different than the actual loads in a CRD0A. In an effort to better simulate these loads, two separate test programs have been initiated at Fort St. Vrain. In one test a. shim motor, mounted on a test stand, is driven by actual gear train components and loaded using the electro-motive force braking capability of the motor. By driving the shim motor at approximately the same speed as in scram operation, shaft loads corresponding to actual operation are achieved. This system has currently completed 17.7 million revolutions, or 2.18 test cycles of the shim motor bearings. Cycling will continue until bearing ' failure is evident. In the other test, an actual.

CRD0A mounted in an equipment storage well will be subjected to repeated scramming and withdrawal of the control rods until one test cycle is completed, at which time the CRD0A will be disassembled and inspected. Both tests are being *

-conducted in a helium atmosphere.

The successful completion of two test cycles for the replacement bearings in the GA Technologies and PSC test l rigs indicates load and service simulation techniques have improved, and that test cycle requirements do not exceed the replacement bearing's capability. Thus, it is concluded that the replacement bearing is suitable for use in the ,

specific application. With these points established, the results of subsequent comparison tests between the original

, and. replacement bcarings will provide a basis for

determining operable lifetimes for the bearings and safety margins associated with the application.

I

- , . _ . - _ , _ _ . . _ . . ,_._ - ,__.- _._. . ,. .._m ._._-m., - - . _ - . - . - _ _ _ . ~ . -

w .

References

1. '" Design Report for Control Rod Drive Mechanisms", GADR-10, Issue L, 6/1/76.

2. " System

Description:

Control Rod Drive (System 12-3)", SD-12-3, Issue E, 7/24/73.

3. Bisson, Edmund E., and Anderson, William J., " Advanced Bearing; Technology", NSA SP-38, 1964.

4. " Load Ratings and Fatigue Life for Ball Bearings", AFBMA Standard-9, June 1972.

5. GA Memo, R. Rosenberg to S.E. Donelson - GTF-12475 dated 9-23-68,

Subject:

Control Rod Drives -

Answers to AEC Questions.

6. " Engineering Evaluation of ITI Bearings for FSV", ITI #P-1293,4/12/85.

7. " Calculation of the Hertz Stresses on C&O Assembly Bearings at Fort St. Vrain", GA Document #907999, 4/16/85.

8. GA memo, J. Petrek to R. Rosenberg - 400:JPP:201:85, dated 4/23/85, subject: Comparison of thei L o life of the Fort St. Vrain Control Rod Drive Bearings.

/  !

y t

f f

s d

ENGINEERING EVALUATION OF CRD0A BEARINGS FORT ST. VRAIN NUCLEAR GENERATING STATION JL!NE 11,1985 5

• f'~

g i

A iiiiw

l APPENDIX A

, Page 1 of 11 Control Rod Drive Bearing Locations D1201-258 n n n D1201-257

) v v D1201-261

{ - - - -

\\ --

- _ D1201-256

--- --- /

Z~~~~~

xx/

h-en.

S X, '

xx =' _

g D1201-265

~ -

D1201-222

_\ / /J XX S h- b

/

7 r g- -g I L_

D1201-259 D1201-260 ~'

@ R Y -

I I F LJ LJ LJ

APPENDIX A Page 2 of 11 Fort St. Vrain Control Rod Drive Bearing Differences GA Technologies Inc. SLR-D1201-222 Historical Reference GA Tech. ITI 16427 ITI 14609 Feature Dwg. Spec. Dwg. Spec. Dwg. Spec.

Source of Manufacture ND SS 3203 SMT ND SS 3203 or equiv.

Ball Size .28125 .2656 .28125 Number of Balls 9 (TC)* 8 (TC)* 9 (TC)*

Outer Race Dimensions:

- Inner Diameter 1.360/1.370 1.326/1329

- Retaining Ring (Seats) 1.483/1.484 1.5025/1.5015

- Lead-in Chamfer Angle 1/2 1

- Ring Width .477/.472 .4674/.4724

- Fracture Groove Angle On 0.D. only On 0.D. and (90 degrees) 1/2 side 5

- Slot for Fracture .08/.10 .085/.105 ,

Groove Width Inner Race Dimensions:

- Outer Diameter .935/.925 .980/.974 Retaining Ring Dimensions:

- Finish 63 Finish 125 Finish

- Outer Diameter 1.562/1.557 1.570/1.568

- Inner Diameter 1.477/1.479 1.5005/1.4990

- Width .036/.026 .050/.046

- thamfer (00) x 45 .010/.015 .018/.023

• Tungsten Carbide

l APPENDIX A Page 3 of 11 Fort St. Vrain Control Rod Drive Bearing Differences GA Technologies Inc. SLR-D1201-222 (cont.)

Historical Reference GA Tech. ITI 16427 ITI 14609 Feature Dwg. Spec. Dwg. Spec. Dwg. Spec.

Retainer (Cage) Dimensions:

- Finish 63 Finish (00) 32 Finish (OD)

- Outer Diameter 1.340/1.335 1.304/1.298

- Inner Diameter 1.025/1.035 1.045/1.055

- Ring Se:t (for 1.275/1.280 1.2440/1.2445 Bearite Rings)

- Hole Spacing 9 eq. sp. 8 eq. sp.

- Hole Diameter .328/.329 .310/.315

- Spacing of .288/.283 .273/.269 Bearite Rings

- Nitriding Ball pockets Ball pockets and 0.D.

Bearite Ring Dimensions:

- Width .140/.120 .113/.108

- Outer Diameter 1.340/1.320 1.2463/1.2460

- Inner Diameter 1.015/1.020 1.060/1.065

- Chamfer on 0.D. 45 1/2 45 1 Differences in cage dimensions were chosen to create the same functior,a1 fit-up as per the GA spec. dwg. as follows:

- Ball to Pocket Axial / Circum. Axial / Circum. Axial / Circum.

Clearance .0018 .0068/ .0034 .0074/ .0033/.047

.047 .048 .044 .049

- Cage Guide Land to .020/.035 .022/.031 .020/.035 Outer Race Clearance

- Nominal Cage I.D. .100 .073 .090 to Inner Race 0.D.

Clearance (Not Functional)

'. *. APPENDIX A Page 4 of 11 Fort St. Vrain Control Rod Drive Bearing Differences GA Technologies Inc. SLR-D1201-256 Historical Reference GA Tech. ITI 16428 ITI 12203 Feature Dwg. Spec. Dwg. Spec. Dwg. Spec.

- Source of Manufacture ND SS 3LOS Mod SMT ITI Ball Size .250 .250 .250 Number of Balls 11 10 11 r

Low Shoulder Height. 0/R .0015/.0020 .0015/.0025 .0010/.0015 Separator (Cage) Dimensions:

3

- Outer Diameter 1.502/1.497 -1.510/1.505

--Inner Diameter 1.290/1.295 1.279/1.281

- Number of Ball Pockets 11 10 Race Dimensions:

- 0/R Land Diameter 1.577 Ref . 1.583/1.587 (Measured)

- I/R Land Diameter 1.280 Ref 1.267/1.268

(Measured)

Differences in cage diameters 'were chosen to create the same functional fit-up as per the GA spec. dwg. as follows:

--Cage Guide Land to .010/.015 .011/.014 .010/.016 Inner Race Clearance s - Nominal Cage-0.0. .078 .078

' Clearance

.(Not Functional) l .

APPENDIX A Page 5 of 11 Fort St. Vrain Control Rod Drive Bearing Differences GA Technologies Inc. SLR-D1201-257 Historical Reference GA Tech. ITI 16429 ITI 12204 Feature Dwg. Spec. Dwg. Spec. Dwg. Spec.

Source of Manufacture ND SS 3205 Mod SMT ITI Ball Size .3125 .3125 .3125 Number of Balls 10 9 10 Low Shoulder Height, 0/R .0016/.0021 .0015/.0025 .0011/.0016 Separator (Cage) Dimensions:

- Outer Diameter 1.650/1.645 1.675/1.670

- Inner Diameter 1.364/1.369 1.334/1.336

- Number of Ball Pockets 10 9 Race Dimensions:

- 0/R Land Diameter 1.725 Ref 1.744/1.756 (Measured)

- I/R Land Diameter 1.353 Ref 1.3221/1.3230 .

(Measured)

Differences in cage diameters were chosen to create the same functional fit-up as per the GA spec. dwg. as follows:

- Cage Guide Land to .011/.016 .011/.014 .009/.016 Inner Race Clearance

- Nominal Cage 0.D. .078 .078 to Outer Race I.D.

Clearance (Not Functional)

+

APPENDIX A Page 6 of 11 Fort St. Vrain Control Rod Drive Bearing Differences GA Technologies Inc. SLR-D1201-258 Historical Reference GA Tech. ITI 16430 ITI 12205 Feature Dwg. Spec. Dwg. Spec. Dwg. Spec.

Source of Manufacture ND SS 3206 Mod SMT ITI Ball Size .375 .375 .375 Number of Balls 10 9 10 Low Shoulder Height, 0/R .0020/.0025 .0020/.0025 .0015/.0020 Separator (Cage) Dimensions:

- Outer Diameter 1.985/1.980 2.000/1.995

- Inner Diameter 1.631/1.636 1.621/1.623

- Number of Ball Pockets 10 9 Race Dimensions:

- 0/R Land Diameter 2.064 Ref 2.075/2.083

- I/R' Land Diameter 1.621 Ref 1.6100/1.6104 Differences in cage diameters were chosen to create the same functional fit-up as per the GA spec. dwg. as follows:

- Cage Guide Land to .010/015 .0106/013 .009/.016 Inner Race Clearance

- Nominal Cage 0.D. .082 .082 to Outer Race I.D.

Clearance (Not Functional)

APPENDIX A Page 7 of 11 Fort St. Vrain Control Rod Drive Bearing Differences GA Technologies Inc. SLR-D1201-259 GA Tech. ITI 12206 Feature Dwg. Spec. Dwg. Spec Source of Manufacture NO SS 3207 Mod Manufactured Complete at ITI Low Shoulder Height, 0/R .0023/.0028 .0025/0030 All other features indentical

l AIPPENDIX A

• ' ~ '

Page 8 of 11 Fort St. Vrain Control Rod-Drive Bearing Differences

-GA Technologies Inc. SLR-D1201-260

. GA Tech. ITI 12207

. Feature Dwg. Spec. Dwg. Spec.

Source of Manufacture MRC-210S-ST Manufactured Mod Complete at ITI Low Shoulder Height, 0/R- .0029/0034 .0031/.0036

~

All other features identical 4

w 3

E.

l.,

2,y Y

k H

[l l 4 gy r - - . - . , _ , ,.y - , , .,%,

APPENDIX A

.Page 9 of 11 Fort St. Vrain Control Rod Drive Bearing Differences GA Technologies Inc. SLR-D1201-261 Historical Reference GA Tech. ITI 16433 ITI 12208 Feature Dwg. Spec. Dwg. Spec. Dwg. Spec.

Source of Manufacture ND SS 3203 Mod SMT ITI Ball Size .2812 .2656 .2812

. Number of Balls 9 8 9 Low Shoulder Height, 0/R .0013/.0018 .0013/0023 .0007/.0012 Separator (Cage) Dimensions:

- Outer Diameter- 1.275/1.270 1.245/1.240

- Inner Diameter .939/.944 .985/.987

- Ball Pocket Diameter .297/.302 .281/.286

- Number of Pockets 9 8

-Race Dimensions:

- 0/R Land Diameter 1.350 Ref 1.315/1.322

- I/R Land Diameter .929 Ref .9739/.9744 (Measured)

Differences in cage dimensions were chosen to create the same functional fit-up as per the GA spec. dwg. as follows:

- Ball to Pocket .0158/.0208 .0154/.0204 .016/.021 Clearance.

-- Cage Guide Land to .010/.015 .0106/.0131 .008/.015 Inner Race Clearance

--Nominal Cage 0.D. .077 .076 Jto Outer Race I.D.

Clearance (Not Functional)

• *~ APPENDIX A Page 10 of 11

~

Fort St. Vrain Control Rod Drive Bearing Differences GA Technologies Inc. SLR-D1201-265 Historical Reference GA Tech. ITI 16434 ITI 12367 Feature Dwg. Spec. Dwg. Spec. Dwg. Spec.

Source of Manufacture ND SS 3203 Mod SMT ITI Ball Size .2812 .2656 .2812 Number of Balls 9-(TC)* 8 (TC)* 9 (TC)*

Low Shoulder Height, 0/R .0013/.0018 .0015/.0020 .0007/.0012 Separator (Cage) Dimensions:

- Outer Diameter 1.275/1.270 1.245/1.240

~- Inner Diameter .939/.944 .985/.987

- Ball Pocket .297/.302 .281/.286

- Number of Pockets 9 8 Race' Dimensions:

-- 0/R-Land Diameter 1.350'Ref 1.318/1.327

--I/R Land Diameter .929 Ref .9740/.9746 Differences in cage dimensions were chosen to create the same functional fit-up as per the GA spec. dwg. as follows:

- Ball to Pocket .0158/.0208 .0154/.0204 .016/.021 Clearance

'-- Cage Guide Land to

.010/.015 .0104/.0130 .008/.015 Inner Ring Clearance

- Nominal-Cage 0.D. .077 .080 to Outer Race I.D.

Clearance.

~(Not Functional)

• Tungsten carbide a .

7

-APPENDIX A Paga 11 of 11 i

Fort St. Vrain Control Rod Drive Bearing Differences ,

GA Technologies Inc. SLR-D1201-420 Historical Reference GA Tech. ITI 16407 ITI 12210 ,

Feature Dwg. Spec. Dwg. Spec. Dwg. Spec.

Source of Manufacture MRC 200-S-ST MRC 200-S-ST ITI Ball Size .250 .21875 .250 Number of Balls 7 7 7 Low Shoulder Height, 0/R .0010/.0015 .0015/.0025 .0007/.0012 Separator (Cage) Dimensions:

- Outer Diameter .890/.887 .875/.872

- Inner Diameter .634/.639 .657/.662

- Ball Pocket Diameter .265/.270 .234/.238 Race Dimensions:

- 0/R Land Diameter .957 Ref .936/.944 '

(Measured)

- I/R Land Diameter .624 Ref .646/.647 (Measured)

The above differences were chosen in design of ITI bearing to create the same functional fit-up as per GA spec. dwg. as follows:

- Ball to Pocket .015/.020 .015/.019 .015/.020 Clearance

- Cage Guide Land to .010/.015 .010/.016 .010/.017 Inner Race Clearance

- Nominal Cage 0.D. .069 .067 to Outer Race I.D.

Clearance (Not Functional)-

i s