ML20106A546

Final Deficiency Rept DER 83-57 Re Cracks in C-E Supplied Control Element Assembly Shroud.Mods Made to Control Element Assembly Guide & Shroud Lateral Supports

ML20106A546
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)
Shared Package
ML20106A551	List: ML20106A546
References
DER-83-57, NUDOCS 8409280486
Download: ML20106A546 (12)

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Arizona Public Service Company A.

2 September 14, 1984' ANPP-30521-TDS/TRB-A U. S. ' Nuclear Regulatory Commission Region V Creekside Oaks' Office Park i1450 Maria Lanc - Suite 210 I

Walnut Creek, CA 94596-5368 Attention: Mr. T. W. Bishop, Director Division of Resident Reactor Projects and Engineering Programs Subjec t:

Final Report - DER 83 "

A 50.55(e)-Reportable Condition _ Relating To Cracks In The

-Control Element Assembly. Shroud.

File: 84-019-026; D 4.33.2

Reference:

A) Telephone Conversation between P. Johnson and R. Tucker on July 29, 1983 B) ANPP-27598, dated August 19,;1983 (Interim Report)

C) ANPP-28093, dated October 26,1983 (Time Extension)'

D)-ANPP-28654, dated January 20,1984 (Interim Report)

E) ANPP-29715, _ dated Jane 11, 1984 (Time Extension)

C F) Telephone conversation between P. Narbut and T. Bradish on

_ August 14, 1984 G) ANPP-30187, dated August 13,1984 (Time Extension)

Dear Sir:

Attached is o'ur final written report of the Reportable Deficiency unde-L10CFR50.55(e), ref erenced. above. - '

Very truly yours,-

G!n A

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E. E. Van -B runt, Jr.

APS.Vice President Nualear Production

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ANPP Project. Director EEVB/TRB/nj.

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Mr. _ T. W. Bishop

- DER 83-57

.Pagc Two CE Doc. No. CEN-267(V)-P

- Revision 1-P -

Proprietary Copies cc:

Richard DeYoung, Director

1. 2 Office of Inspection and Enforceme.nt U. S. Nuclear Regulatory Commission

- Washington, D. C. 20555 T. G. Woods,~Jr.

1. 3 D. B. Karner W. E. Ide D, B. Fasnacht A. C. Rogers L. A. Souza D. E. Fowler T. D. Shriver

1. 4 C. N. Russo J. - D. Houchen J. R. Bynum J. M. Allen J. A. Brand A. C. Gehr

1. 5 W. J. Stubblefield

1. 6 W. G. Bir,gham

1. 7 R. L. Patterson

1. 8 R. W. Welcher

1. 9 H. D. Foster

1. 10 D. R. Hawkinson

1. 11 L. E. Vorderbrueggen

1. 12 R. P. Zimmerman

1. 13-M. Woods T. J. Bloom D. N. Stover L. Clyde D. Canady Records Center Institute of Nuclear Power Operations 1100 circle 75 Parkway, Suite 1500 Atlanta, CA 30339

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U7 S7Ndelear' Regulatory Commission Phillips Building 7920 Norfolk Avenue Bethesda, MD 20814 File: DER 83-57

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FINAL REPORT; DER 83-57 c

' DEFICIENCY EVALUATION 50.55(e)

A11 ZONA PUBLIC; SERVICE COMPANY _ (APS).

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'PVNGO UNITS 1, 2, 3

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JCondition Describtion' Inspection of the Palo Verde Unit 1. reactor internals isubsequent to Pre-Core HFT in July 1983 revealed damage -

to the CEA shroud. The CEA" shroud is part of the upper Guide: Structure (UGS) assembly furnished by Combustion

. Engineering (C-E;. The' CEA shroud consists of an array of vertical -round. tubes arranged in a square grid pattern. The tubes are; joined by welding vertical plates called webs

- between adjacent tubes. Tubes and webs are fabricated f rom type 304 stainlessLateel.

Guides for the 4-finger CEA extension shaf ts are attached -

to the top of-the_ tubes and guides f or the 12-finger-CEA y

extension shafts are attached to the webs. These guides align

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the CEA extension shaf ts for entry into the closure head nozzles during closure head installation and into the internals lif t rig during attachment.

'The ' damage, revealed by visual and dye penetrant examination r

and documented by NCRs SM2470 and SM3155, consisted of the folicuing:

1. - A total of 13 cracks in eleven 4-finger CEA sh oud tubes.

In most instances, these cracks start in the welds at the attachment of the 4-finger CEA guides to the shroud tubes.

2.. Two-cracks involving the welds at the attachment of the

~12-finger CEA ' extension shaf t guides to the webs,

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Three cracks involving the welds between 4-finger CEA shroud tubes and webs; two. at the top of the shroud and one at the bottom.

4 One crack in the base metal of a web.

5. - Three wear marks on the shroud at the 45' location.

6. ' One ductile break, one half-inch long, located in a web at the bottom.

Evaluation The CEA shroud is a f eature first used in the C-E System 80 t:

. The design is not used on other C-E NSSSs.

In reactor.

addition to Palo Verde Unit 1, similar CEA shrouds are part of the upper guide structure (UGS)- delivered to Palo Verde Units

. 2 and 3, and other System 80 plants under construction.

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. DER 83-57)

Page Two The' CEA shroud is not a core support structure under the definition of the' ASME' code, ' Section NC, and does not in itself perf orm a. safety function. The assembly of tubes and webs. serves to provide separation of the CEAs. Flow is

. restricted within the CEA shroud region, theref ore, the shroud -

. assembly is not subjected to significant operating loads.

Th' ' extension shaf t guideo -located at the top of the shroud e

are provided to align CEA' extension shaf ts for entry into the closure head nozzles during closure head installation. They have no function during reactor operation. Although not observed,'a hypothetical, complete fallere in CEA shroud tubes or webs particularly to the extent that extension shaf t guides

. loosen or become detached would have' potential adverse safety implications in that: the insertion of CEAs could be impeded or prevented by interf erence with the loose components.. The 3

damage which was observed on the Palo Verde Unit 1 CEA shroud ji

. would not have prevented a reactor trip had it.been present in an operating reactor.

y An' intensive investigative program was initiated by C-E to evaluate the nature and extent of the cracks which were observed in the CEA shroud and to determine the necessary modifications to correct the problems. The program included vibration tests, hydraulic and mechanical tests, analytical

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modeling and metallurgical examinations both at C-E and at iadependent testing labs. A combination of experimental and

. analytical results indicate the root cause to be vibration which caused the fatigue 'eracks in localized regions with high stress concentration. A modified design minimizes this stress-concentration and limits the maximum possible amplitude of the

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. likely damaging mode of vibration.

. In addition to the f atigue cracking, the other principal failure mechanism was determined to be trans granular stress corrosion cracking (TCSCC) due to concentrations of potassium hydroxide (KOH).'. This source of contaminant was traced to

. entrapped. slag from the welding electrode coating f rom the shielded-metal arc welding (SMAW) process used at the tube-to-web joints.

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Mr. T. W. Bishop.

DER - 8 3-5 7 Page Three An evaluation to determine if other RCS components might have been affected by the KOH considered material in close proximity and overall RCS KOH concentration, i.e., KOH concentrations greater than 100 ppm at reactor-operating conditions will cause TGSCC. There was no evidence of TGSCC in either damaged or undamaged thread areas on adjacent pa rt s.

Furthermore, a conservative estimate determined e 1.4 ppm rise in KOH would occur in the RCS if all the flux in the' tube-to-web joints were dissolved.

II.

Analysis of Safety Implications Based on the above, this condition is evaluated as reportable under the requirements of 10CFR50.55(e) since, if this condition were to remain uncorrected, it would represent a significant safety condition.

This project has also evaluated this condition as reportable under 10CFR21.21(b)(3). This report addresses the reporting requirements of the regulation with the exception of subpart (vi), regarding the number and location of such components supplied to other facilities. A-copy of this report will be transmitted to C-E.

III.

Corrective Action-The e scrective actions taken were in two specific areas, i.e.,

CEA guide modifications and CEA shroud lateral support mcdifications, with a subsegunnt demonstration test to validate the adequacy of the modifications.

CEA Guide Modifications The modification consists of removing the top three inches of the CEA shroud and all the 4-finger and 12-finger CEA guides.

Since the guides have no function during normal operation, their function is provided by a separate tool, utilized only during refueling operations, which is not a permanent part of the vessel or the internals.- This eliminates locations for crack initiation due to high stress concentration at the top of ' the tubes, the potential for interference sith CEA insertion and the potential for resonance f ailure caused by vibration of the CEA guides.

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Mr.- T. -W. Bishop DER,83-57

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- Cutting' three inches f rom the top 'of 'the CEA shroud eliminates the affectc of the original welding of the guides. This

-length is reduced everywhere except atiche eight tie rod locations and' two locations for Reactor Vessel Level Monitoring System (RVLMS) probes. ' These shroud tubes remain fu11' length to eliminate the need for changes to the tie rod.

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. assembly and to the Heated ' Junction Thermocouple RVLMS.

'Af ter cutoff, a minimum of three inches of the welds at the top between webs and' shroud tubes were ground: out and replaced with full penetration welds. An additional fillet weld was.

applied over' this to minimize the -stress concentration at the junctions.. The bottom welds at the tie rod ' locations were also reworked in like manner. SMA welding, which. led to the

..TGSCC failure mechanism, was not used for'any rework.a L

CEA Shroud Lateral Support Modifications

w' The CEA shroud is held:down to the Upper Guide Structure Support Plate by eight tie rods. Stiffness of the shroud assembly provides the ? restraint against lateral f orces in the original. design. Analyses indicated 1that global modes of vibration of the shroud could cause lateral deflection of the~

outer tubes and webs and would contribute to-higher stresses.

To limit ; such lateral deflections, four 'anubbers-were added to

,the;CEA shroud.-

1The snubber' consists of. three pieces. - A -snubber block assembly is shop welded into the three outermost shroud' tubes on 'each of f our sides of 'the shroud. A flange block assembly is field installed 'on the UGS barrel flange by pins -and bolts. A'hard shim is field fitted to the snubber-block to it provide a ' controlled clearance with:the sides of the slot in

.the flange ' block. The completed ' snubber: assembly allows radial and axial differential motion between the CEA shroud and the UGS barrel but restricts lateral or tangential motion

. to the amount of clearance at the shim.

The CEA guide. modifications and the installation of the

.-snubber block assembly onto the CEA shroud were performed by C-E at,their Newington facility.

The field installation of the flange block assembly onto the UGS barrel was performed via DCPs (Reference 1).

These'DCPs and' the modifications by C-E as detailed in N

Reference 2. provide corrective action disposition of

.NCRs SM2470 and.SM3155.

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..e Mr. T. @ Bishop DER 83-57' Page Five

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f Demonstration Test I-A demonstration test incorporating extensive instrumentation

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. was performed on Unit 1 during July and August, 1984 to confirm the adequacy of the modified shroud and UGS under operating condi:: ions and to determine actual loadings and structural responses. A detailed post-test inspection confirmed conclusions f rom the previous component tests and analyses that the modified CEA shroud is adequate for. its -

design service.

F A detailed description of the investigative and testing program, 'the res Its,' and' the physical modifications perf ormed

-'are included in Reference 2.

IV. -

. References 1.

DOPs ISM-RC-112, 2SM-RC-112, 3CM-RC-112

2.. C-E's Proprietary Final Report CEN-267 (V)-P, Rev.1-P, dated August, 1984, Perf ormance Evaluation of the Palo Verde Control Element. Assembly' Shroud.

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wr L C-E Power Sy tems Tel 203/6881911 Combustion Erbyi)QQ; 'EN TElt Telex: 99297 1000 Prospect Hill Roao Windsor. Connecticut 06095 d4'-dat-V/ 9 PN POWER Ed 3 SYSTEMS QA ec h t Lc. b n. GsCLA bd%ud b /N'XC September 10, 1984 e ec-d 4 (2 L dau 2j'r V-CE 30912 fr.4,t. w re-se. d y k i L O R w p

Mr. E. E. Van Brunt Arizona Nuclear Power Project P. O. Box 21666 - Sta. 3003 Phoenix, Arizona 85036

Subject:

10 CFR 50.55(e) Report on the Palo Verde CEA Shroud

Dear Mr. Var. Brunt:

Enclosed for your submittal to the Nuclear Reculatory Commission is the 10 CFR 50.55(e) report on the Palo Verde CEA Shroud along with the proprietary affidavit. Copies 1 through 25 of the proprietary report are intended for submittal to the NRC. Copies 26 through 43 are provided for APS use.

In addition, thirty-five cooies of the non-proprietary version are also enclosed. This report is a final report and is considered complete.

If you have any questions feel free to call.

Very truly yours,

,L C. Fer

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CF/TJC:jld Ul b Enclosures Resp.

cc: D.B.Amerinew/ copy 45 A_CG W. G. Bingham w/ copy 44 Mgr./

_GCA Supv T. R. Bradish G. A. Butterworth

_SCJ J. R. Bynum

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AFFIDAVIT PURSUANT TO 10 CFR 2.790 Combustion Engineering, Inc.

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State of Connecticut

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County of Hartford-

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SS.:

I, A. E. Scherer, depose and say that I am the Director, Nuclear Licensing, of Combustion Engineering, Inc., duly authorized to make 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-267(V)-P Revision 1-P-Final Report on.the Performance Evaluation of the Pala Verde Control Element Assembly Shrou'd, August 1984.

' This document has been appropriately designated as proprietary.

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

Pursuant to the provisions of paragrap'n (b) (4) of Section 2.790 of the

. Commission's regulations, the following is furnished for consideration by the

-Commission in deternining whether the information sought to be withheld from public disclosure,-included in the above referenced document, should be withheld.

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-1.: The information sought to be withneld from public disclosure are

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experimental data from the Palo Verde 1 Comprehensive Vibration Assessment Program (CVAP), demonstration test, and other associated laboratory tests, Ldetailed design data and analytical results for the Control Element Assembly (CEA) shroud, 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 nf a type customarily held in confidence by Combustion Engineering and not customarily disclosed to the public. Conbustion 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 det. ermine 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 Conmission in confidence under the provisions 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 Conbustion Engineering because:

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A similar product is nanufactured and sold by ma,ine pressurized water reactor competitors of Combustion Engineering.

b.

Development o'f this information by C-E required thousands of man-hours of effort'and hundreds of thousands 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 the detailed design, testing, and. analysis for the Control Element Assenbly shroud, 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 experimental data and the associated laboratory tests, detailed design data, and analytical results for vibration

' testing of. the Control Element Assembly shroud at Palo Verde 1, the application of which provides a competiti_ve economic advantage.

'The availability of such information to competitors would enable them to modify their product to better compete with Combustinn Engineering, take marketing or other attions to improve their product's position or impair the position F '..o'ust or Engineering's product, and avoid developing similar data and an oyses in 'upport t f their processes, methods or apparatus.

f..

In pricing Canbustion Engineering's products and sei vices, significant research, development, engineering, analytical, manufacturing, if censing, quality assurance and other costs and expenses must be included.

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

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

g.

Use of the information 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 naintaining foreign licensees.

Further the deponent sayeth not.

A. E.

cherer Director Nuclear Licensing Sworn to before me yh this s day of 44

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