ML20098E001

Final Deficiency Rept DER 83-49 Re Broken or Loose Impeller Blades & Diffuser Bolts in Reactor Coolant Pumps.Proprietary Rev 1-P to CEN-271(V)-P, Final Rept on Palo Verde... & Affidavit Encl.Rept Withheld (Ref 10CFR2.790)

ML20098E001
Person / Time
Site:	Palo Verde
Issue date:	09/14/1984
From:	Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	Bishop T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
ANPP-30520-TDS, DER-83-49, NUDOCS 8409280098
Download: ML20098E001 (13)

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itce,3 hnc Arizona Public Service Company Wt EP I 7 g n y September 14, 1984 ANPP-30520-TDS/TRB gg,j

- U. S. Nuclear Regulatory Commission Region V

. Creekside Oaks Office Park

'1450 Maria Lane - Suite 210 Walnut Creek, CA 94596-5368 Attention: Mr. T. W. Bishop, Director Division of Resident Reactor Projects and Engineering Programs

Subject:

Final Report - DER 83-49 A 50.55(e) Reportable Condition Relating to Broken Impeller Blades and Diffuser Bolts Broken / Loose In The Reactor Coolant Pumps.

File: 84-019-026; D.4.33.2 Ref erence: A) Telephone Conversation between P. Narbut and R. Tucker on July 15, 1983 B) ANPP-Telephone conversation between T. Young and R. Tucker on July 18,1983 (Interim Report)

C) ANPP-ANPP-27593, dated August 19,1983 (Interim Report)

D) ANPP-28734, dated January 27, 1984 (DER 83-50 Interim Report, Revision 1)

E) ANPP-28733, dated January 27,1984 (Interim Report, Revision 1)

F) ANPP-28313, dated November 29,1983 (Time Extension)

G) ANPP-29713, dated June 11,1984 (Time Extension)

H) Telephone conversation between P. Narbut- and T. Bradish on August 14, 1984)

I) ANPP-30188, dated August 13,1984 (Time Extension)

Dear Sir:

Attached is our final written report of the deficiency referenced above, which has been determined to be Not Reportable under the requirements of 10CFR50.55(e) .

Very truly yours, EE%%k/g E. E. Van Brunt, Jr.

APS Vice President Nuclear Production ANPP Project Director EEVB/TRE/nj Se age Two- 9 O S

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l Mr. T. W. Bishop DER 83-49 Page Two .

CE Doc. No. CEN-271(V)-P

- Revision 1-P -

Proprietary Copies cc: Richard DeYoung, Director #2 Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission

. Washington, D. C. 20555

T. G. Woods, Jr. #3 D. B. Karner

• W. E. Ide

• D. B. Fasnacht

• A. C. Rogers

• L. A. Souza

• D. E. Fowler

• T. D. Shriver #4-C. N. Russo

• J. D. Houchen-

• J. R. Bynum

• J. M. Allen

• J. A. Brand

• A. C. Gehr #5 W. J. Stubblefield #6 W. G. Binghan #7 R. L. Patterson #8 R. W. Welcher #9 H. D. Foster #10 D. R. Hawkinson #11 L. E. Vorderbrueggen #12 R. P. Zimmerman #13 M. Woods

• T. J. Bloom

• D. N. Stover

• L. Clyde

• D. Canady

• Records Center

• Institute of Nuclear Fower Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, GA 30339

Mr. E. Licitra #14 through #37 U.' S. Nuclear Regulatory Commission Phillips Building 7920 Norfolk Avenue Bethesda, MD 20814 File

DER 83-49 #38

• Non-Proprietary Copy Attached

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FINAL. REPORT - DER 83-49

" DEFICIENCY EVALUATION 50.55(e)

~ ARIZONA.PUBLIC SEEVICE COMPANY (APS)

PVNGS UNITS 1, 2,~3 4

I. Description of Deficiency

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Af ter pre-core hot functional testing (HFT) in July 1983, the Unit 1 RCP (tag IMRCEP01A) was disassembled to repair a previously identified linear indication in the pump casing circumf erential weld. ' An inspection of the -pump internals revealed four broken and two loose diffuser-to-casing retaining cap screws. Also,. ten'of the diffuser-to-suction pipe car screws were found to be _ loose and the impeller shaf t

. keyway bolt was breken, (Ref. NCR 2657) . There was also slight cavitation ' damage on the leading edge of .seven diffuser vane s. .

As a result of the above, the other three Unit 1 RCPs (tags 1MRCEP01B, C, D) were disassembled and inspect. .i. In addition to discovering loose and/or broken diffuser and suction pipe

- cap screws, damage was noted as follows (Ref. NCRs SM-2658, 2659, and 2660):

The pump casing internal surface above the impeller had sustained peening damage from the loose diffuser cap screws.

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The pump casing-to-diffuser fit indicated surface fretting damage ~ had occurred due to relative motion between the part s.

Pieces were missing. from the leading edge of one impeller vane on RCP 1B and two vanes on RCP 2A, There were broken and/or loose impeller key retaining screws shaf t protection sleeve key retaining rings, and carbon journal bearing ke.y retaining screws.

The shaf t seals showed wear on the stationary seal ring holders and heavy deposits of 0-ring lubricant was noted throughout the seal assemblies. Also, bolts in the seal cartridges were ' loose.

Leakage was observed between the carbon bearing sleeve and the seal housing, indicating seal ring failure.

The PVNGS type R01 Reactor Coolant Pumps are supplied by Combustion Engineering (C-E), designed by Klein Schanzlin &

Becker (KSB) of West Germany, and were manufactured and perf ormance-tested by CE-KSB in Newington, New Hampshire. .

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._Mr.1T. W. Bishop DER ' 83-49 Page Two S~ Evaluation

.CE-KSB has manufactured and _ tested a. total'of 24 duplicate

' type-R01 RCPs.at their Newington facility for use in System 80

~ plants.' 'The Palo Verde IB pump, che first of. this group tested;'was'run approximately'600 hours0.00694 days <br />0.167 hours <br />9.920635e-4 weeks <br />2.283e-4 months <br /> in the test loop. All the other pumps were tested approximately fif ty hours each.

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The damage described in-section I above was incurred during 700 to 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> of operation per pump during the HFT. There are no'RCPs of this design in any operating plant. The pumps at. Palo Verde Unit 1 are the first of this particular design to be operated in other than a test loop, therefore, any design or material deficiencies would be evidenced af ter the BFT at' Palo Verde.

The root cause of the capscrew and impeller vane f ailures is fatigue, i.e., cyclic loading exceeded the material fatigue s tre ng th. In the case of both the diff user -casing and diffuser-to-suction pipe capscrews, it was determined that loss of pre-load preceded the f atigue failures. The loss of pre-load was due' to a combination of cyclic loading; a relatively low capscrew working pre-load (approximately 45% of yield); and ambiguous and multiple load paths.

The proximity of the impeller outer diameter (OD) to the leading edge of the diffuser vanes (ID); in this case 11mm

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(2.3% of impeller radius), contributed to the magnitude of the dynamic f orces which caused. the' fatigue failures and to the cavitation damage' of some diffuser vanes. Fatiguing hydraulic pressure fluctuations are generatad at the rate of 78;000 impulses per minute (6 impeller vanes x 11 diffuser vanes x 1180 rpm). The close gap between the impeller and diffuser vanes increases the pulse intensity and the potential for -

fatigue f ailures. Operation at runout (single pump) which is approximately 142% of design flow, produces the highest pulse intensities and therefore the highest stresses in the working pa rt s.

KSB conducted model tests to evaluate the affects of increased impeller-to-diffuser clearance to preclude diffuser vane leading edge cavitation damage and reduce the magnitude of dymanic forces,- both at design and runout flows. Tle hydraulic model' employed for this test program was the same a-used during the original development of this particular RCP.

This testing was also used to verify that the original design requirements for head-capacity, horsepower, and NPSHR would

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Mr.' T.! W. _ Bishop DER 83-49 Page Three-not be compromised by this modification. From these tests, it was determined that increasing the radial gap from lima to -

28.5mm (6.0% of impeller radius) .by cutting back and re profiling the leading edges of the diffuser vanes would produce the desired results of . reduction in.the magnitude of the dynamic forces and elimination of cavitation damage.

These model tests also verified that head reduction at the design capacity due to the increased gap could be efficiently recovered by backfiling the impeller vanes and that the resultant change in runout 'perf ormance would be acceptable.

Analyses of material properties of both capscrews and impe11ers by CE-KSB verified that the materials conformed to specifications were not deficient, and that failures were due to fatigue.

A detailed survey of .the three broken impeller vanes and nineteen intact vanes (the two remaining vanes were used f or metallurgical examinations) revealed that the broken vanes were thinner than the intact vanes in the critical area at the leading edge to upper shroud junction. Both finite element stress analysis and strain gage tests were correlated to the known fatigue failure stress in the f ailed vanes, including variables such as casting imperfections and stress concentrations. Using these values, the analysis of an intact vane with greater thickness and greater fillet radius than the failed vanes results in peak stresses well below the fatigue failure stress. This design analysis by CE-KSB concludes that all the impe11ers now installed have a safety f actor of at least 1.5 over the impe11ers originally used in the Unit 1 RCPs. .(For impeller modifications, see section III, paragraph 2).

The increased impeller to diffuser gap fur *her-reduces loads, therefor , the current safety margin is now approximately 1.75 compared to the thickest vane which previously ' f ailed.

II. Analysis of Safety Implications C-E investigated various f ailure mechanisms of the RCPs and consequential damage to . the system including locked rotor, degraded pump costdown and core flow blockage. In all cases it was determined that the internal failures would not constitute a safety hazard. The safety requirement-of the RCPs is to maintain the Reactor Coolant System (RCS) pressure boundary integrity.- C-E has determined that if the conditions had remained uncorrected, the integrity of the RCS pressure boundary would not be compromised.

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Mr. _ T. .Wi -. Bishop

< DEP 83-4 9 Page Four :

. Based on the preservation ofLthe reactor coolant pressure boundary integrity and the fact'that fragments of RCP internals will not damage the reactor, have adverse affect on heat transfer to fuel elements, or-interfere with control rod movement. . the project evaluates the RCP deficiencies as not reportable under the requirements .of 10CFR50.55(e) and 10CFR Part 21; 'since, if these conditions were to remain

' uncorrected, they would not represent a significant safety haza rd.

III. Corrective : Action A comprehensive program was completed by C-E, CE-KSB, ond KSB confirm the root cause of the -deficiencies and define and

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implement specific modifications. Additionally, programs were established to ' verify the modifications by analysis, model

- testing, prototype testing, and full-scale field testing.

These programs and their results are contained in Reference (1).

C-E's corrective action program and disposition of the ref erenced NCRs are summarized as follows:

1) The diffuser-to-casing fit (#1) and the suction pipe-to-diffuser fits (#2) were redesigned to eliminate ambiguous load paths and to minimize the number of multiple load paths, i.e., elimination of tapered fits, use of shorter ring segments at fit #1, and addition of a support ring and four reinforcing level pins at fit #2.

Additionally. the number of capscrews was increased (f rom.

16 to 29 for fit #1 and f rom 16 to 24 for fit #2) and the design torques increased to provide working stresses of 85%

of yield. 'Also, the fit #1 capscrews were increased in length by 54% to make them less susceptible to loss of preload due to thermal' and cyclic loading affects and the length of the threaded inserts (helicoils) in the diffuser was increased to guarantee complete thread engagement. A re-analysis was conducted to verify that the capscrew preloads will exceed operating loads under all variations of operating conditions.

A total of 351 hours0.00406 days <br />0.0975 hours <br />5.803571e-4 weeks <br />1.335555e-4 months <br /> of testing was conducted in the CE-KSB test loop to generate baseline data on an unmodified pump and comparable data af ter modifications. Accelerometer and strain gage data indicated that the original. loss of preload could be duplicated within 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />' of runout operation. After modification,~ data verified that there was -no change of capscrew strain af ter 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> of operation at runout,

. Mr.LT2 W. Bishop DER 83-49.

Page Five-

-2) The' Atlas (foundry source)-impe11ers for the Unit 1 & 2

-RCPs were: replaced by Schmidt and Clemens (S&C, -foundry -

source) impe11ers which were available from other

.(cancelled) System 80 plants. The S&C impe11ers .have -

thicker vanes with a flatter profile than the Atlas impe11ers near the leading edge where the failures occurred. At' sections further away from the leading edge, there are less differences in vane thickness between the Atlas and S&C impe11ers. The Unit 3 impe11ers were replaced .with Atlas impe11ers where the vane leading edges were re profiled so the leading edge thicknesses are equal to or greater than the replacement S&C impe11ers installed in the Unit 1 & 2 RCPs. .

' All impellers were backfiled (to compensate for head loss due to cutting back the diffuser vanes) and rebalanced.

One S&C and one modified Atlas impeller were retested with c' heir diffusers in the CE-KSB test loop in Newington to verify the hydraulic performance of the modified parts.

3) Examination of the broken impeller key retaining screws indicated that the sockets in the heads were formed too deep. This resulted in insufficient wall thickness in the head to shank area. These screws were redesigned with a larger head to accommodate the socket. These screws will be installed with retaining sleeves and staked in place.

The shaf t protection sleeve and carbon journal bearing key

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retaining screws are smaller screws and their looseness was attributed to vibration. The method of torquing these screws and staking them was revised.

4) The bearing sleeve to. seal housing seal ring was replaced with.a flexitallic type gasket. The size of the bolts in the joint was increased to insure that the gasket is properly seated.

5) Regarding the shaf t seal deficiencies, instructions will be issued by C-E on the proper use of "0" ring lubrication.

Precautions will also be taken to insure that the seal cartridge bolts are properly torqued.

The Unit 1 seal cartridges have been designated as test sets and have been installed in the Unit 2 RCPs for use during hot functional tests (HFT). They will subsequently be used for Unit 3 HFT. Unit 2 seal cartridges have been installed in the Unit 1 RCPs, reference NCR dispositions.

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3 Mr. T. W. Bishop DER 83-49 Page Six 4

6) Special demonstration tests during July / August 1984 f or the four modified Unit 1 RCPs, with subsequent disassembly of the 2B pump for a detailed inspection, have reconfirmed the adequacy of the corrective actions. The test sequence included the same conditions as those which resulted in the original damage and totaled 737 hours0.00853 days <br />0.205 hours <br />0.00122 weeks <br />2.804285e-4 months <br /> of running time on the 2B RCP (Reference 2).

The post-tect inspection confirmed all diffuser and suction pipe cap scr ews were properly secured. Also, there was nn evidence of itavitation wear on either the diffuser or impeller vants. Liquid penetrant inspection of the impeller vanet showed no unacceptable indications.

7) The required cc*rective actions for Unit I were implemented prior to the above mcrtioned demonstration test via the following Design Change 2*ckages (DCPs).

ISM-RC-107 ISM-RC-109 ISM-RC-113 Additionally, these same changes will be implemented in the Units 2 and 3 RCPs prior to their fuel load via DCPs as follows:

2SM-RC-107 304-RC-107 2SM-RC-109 3CM-RC-109 2SM-RC-113 3CH-RC-113 These DCPs provide the corrective action disposition of NCRs SM-1657, -2658, -2659, and -2660.

IV. References

1. Letter V-CE-30867, August 30, 1984

, C-E Final Report (proprietary) on Palo Verde Nuclear i Generating Station Reactor Coolant Pumps, CEN-271(V)-P, I August 1984

2. Letter V-CE-21757, August 14, 1984.

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'84 SEP -5 MO 33 1 , C-E Power Systems Te!. 203/688-1911 C:mbustion EnggrM& CENTER Mn M297 1000 Prospect Hill Road Windsor. Conrjecticut 06095

$Y-00/- Y/9 /

• POWER

.am SYSTEMS August 30, 1984 V-CE-30867 Mr. E. E. Van Brunt, Jr.

Arizona Nuclear Power Project P. O. Box 21666 - Sta. 3003 Phoenix, Arizona 85036 i

Subject:

10 CFR 50.55(e) Report on the Palo Verde Reactor Coolant Pumps

Dear Mr. Van Brunt:

j Enclosed for your submittal to the Nuclear Regulatory Commission is the 10 CFR ,

) 50.55(e) report on the Palo Verde Reactor Coolant Pumps along with the '

{ proprietary affidavit. Copies 1 through 25 of the proprietary repport are intended for submittal to the NRC. Copies 26 througt 43 are provided for APS ,

use. In addition, thirty-five copies of the non-proprietary version are also '

enclosed. This report is a final report and is considered complete.

If yoa have any questions feel free to call.

Very truly yours,

' Mt C. Ferguson ,/

Project Manager V l (sv l CF/TJC:jld Enclosures cc: D. B. Amerine w/c apy 45 W. G. Bingham w/ copy 44 T. R. Bradish G. A. Butterworth J. R. Bynum J.W.Dik R. H. Holm W. L. MacDonald W. H. Wilson W. F. Quinn

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-AFFIDAVIT PURSUANT TO 10 CFR 2.790 Combustion Engineerlag, Inc. )

State of Connecticut )

County of Hartford ) SS.:

I, A.~E. Scherer, depose and say that I am the Director, Nuclear Licensing, of Combustion Engineering, Inc., duly authorized to md.e this affidavit, and have reviewed or caused to have reviewed the information which is identified as proprietary and referenced in the paragraph immediately below. I am submitting this affidavit in conformance with the provisions of 10 CFR 2.790 of the Commission's regulations and in conjunction with the construction permit of Arizona Public Service Company, for withholding this information.

The'information for which proprietary treatment is sought is contained in the following document:

CEN-271(V)-P Rev.1-P, Final Report on Palo Verde Nuclear Generating Station Unit #1 Reactor Coolant Pumps, August 1984.

This document has been appropriately designated as proprietary.

I have personal knowledge of the criteria and procedures utilized by Combustion Engineering in designating information as a trade secret, privileged or as confidential commercial or financial information.

Pursuant to the provisions of paragraph (o) (4) of Section 2.790 of the Commission's regulations, the following is furnished for consideration by the Commission in determining whether the information sought to be withheld from public disclosure, included in the above referenced document, shou'd be withheld.

1. The information sought to be withheld from public disclosure are Reactor Coolant Pump design and experimental test data and analysis from -

testing, which is owned and has been held in confidence by Combustion Engineering.

2. The information consists of test data or other similar data concerning a process, method or component, _the application of which results in a substantial competitive advantage to Combustion Engineering.

3. .The information is of a type customarily held in confidence by Combustion Engineering and not customarily disclosed to the public. Combustion Engineering has a rational basis for determining the types of information customarily held in confidence by it and, in that connection, utilizes a system to determine when and whether to hold certain types of information in confidence. The details of the aforementioned system were provided to the Nuclear Regulatory Commission via letter DP-537 from F.M. Stern to Frank Schroeder dated December 2, 1974. This system was applied in determining that the subject document herein are proprietary.

4. The information is being transmitted to the Commission in confidence under the prov sions of 10 CFR 2.790 with the understanding that it is to be received in confidence by the Commission.

5. The information, to the best of my knowledge and belief, is not available in public sources, and any disclosure to third parties has been made pursuant to regulatory provisions or proprietary agreements which provide for maintenance of the information in confidence.

6. Public disclosure of the information is likely to cause substantial harm to the competitive position of Combustion Engineering because:

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a. LA similar product is manufactured and sold by major pressurized ,

. water reactor competitors of Combustion Engineering.

b. Development of this information by C-E required tens of thousands of man-hours of effort and millions of dollars- . To the best of my knowledge-and belief a competitor would have to undergo similar expense in generating equivalent information.

c. In order _to acquire such information, a competitor would also require considerable time'and inconvenience related to Reactor Coolant Pump design'and detailed test data and analysis.

d.- The information required significant effort and expense to obtain the licensing approvals necessary for application of the information.

Avoidance of this expense would decrease a competitor's cost in applying the information and marketing the product to which the information is applicable,

e. The information consists of Reactor Coolant Pump design and experimental test data and analysis, the application of which provides a competitive economic advantage. The availability of such information to competitors would enable them to modify their product to better compete with

. Combustion Engineering, take marketing or other actions to improve their product's position or. impair the position of Combustion Engineering's product, and avoid developing similar data and analyses in support of their processes,

methods or apparatus.

,_ f. In pricing Combustion Engineering's products and services, 4

significant reseat ch, development, engineering, analytical, manufacturing, licensing, quality assurance and other costs and expenses must be included.

The ability of Combustion Engineering's competitors to utilize such information l

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.. . l without similar expenditure of resources may enable them to sell at prices reflecting significantly lower costs,

g. Use of the inforrration by competitors in the international marketplace would increase their ability to market nuclear steam supply systems .

by reducing the costs associated with their technology development. In addition, disclosure would have an adverse economic impact on Combustion Engineering's potential for obtaining or maintaining foreign licensees.

Further the deponent sayeth not.

J _4MN A.E.SIerer Director riuclear Licensing Sworn to before me this . 30 day /. iof @OQ.1994

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