ML20098E449

Final Part 21 & Deficiency Rept Re Cracks in C-E Supplied Control Element Assembly Shroud.Mods Made to Control Element Assembly Guide & Shroud Lateral Supports

ML20098E449
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
REF-PT21-84-459-000 ANPP-30521-TDS, DER-83-57, PT21-84-459, PT21-84-459-000, NUDOCS 8409280486
Download: ML20098E449 (12)

Text

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'1fCDVED N7.C Anzona Public Service Company EG SEP i7 jJi B 26 September 14, 1984 ANPP-30521-TDS/TRBUE V LI" 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 83-57 A 50.55(e) Reportable Condition Relating To Cracks In The Control Element Assembly Shroud.

File: 84-019-026; D.4.33.2 Refere nce: 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 June 11,1984 (Time Extension)

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 our final written report of the Reportable Deficiency under 10CFR50.55(e), ref erenced above.

Very truly yours, G!ts

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E. E. Van Brunt, Jr.

APS Vice President Nuclear Production ANPP Project Director EEVB/TRB/nj Attachment ec: See Page Two 8409280486 840914 PDR ADOCK 05000528 S-PDR J_-A /

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.Mr. T.. W. Bishop ;

DER 83-57 Page Two CE Doc. No. CEN-267(V)-P Revision l-P -

Proprietary Copies cc:

Richaid DeYoung, Director

1. 2 Office of Inspection and Enf orcement U. S. Nuclear Regulatory. Constission Washington, D. C. 20555.'

T. G. Woods, Jr.

~#3 D. B. Ka rner '

W. E. Ide D. B. Fasnacht A. C. Rogers L. A. Souza

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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. Bingham

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. Zinunerman

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, GA 30339

-Mr. E. Licitra

1. 14 through #37 U. S. Nuclear Regulatory Commission Phillips Building 7920 Norfolk Avenue

. Bethesda, MD 20814

- File: DER 83 #38

• Non-Proprietary Copy Attached.

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FINAL REPORT - DER 83-57' DEFICIENCY EVALUATION 50.55(e)

. ARIZONA PUBLIC SERVICE COMPANY-( APS) ~

PVNGS UNITS 1, 2, 3 I.

Condition Description Inspection of the Palo Verde Unit 1. reactor internals subsequent 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 stainless steel.

Guides f or the 4-finger CEA extension' shaf ts-are attached to the top of the tubes and guides f or the.12-finger CEA extension shafts are attached to the webs. These guides align 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 and documented by NCRs.SM2470 and SM3155,. consisted of the following:

1.

A. total of 13 cracks in eleven 4-finger CEA shroud 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 j

12-finger CEA extension shaf t guides to the webs.

3.

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 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 hal'f-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

. reactor. The design is not used on other=C-E NSSSs.--In 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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.Page'Two i

1The CEA shroud is not. a core support structure.under the odefinition of the ASME code, Section NG, and does not in if 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.

The extension slmf t guides located at the top of the shroud 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 failure in CEA shroud tubes or webs particularly to the extent that extension shaf t guides loosen or become detached would have potential adverse safety l

implications in that the insertion of CEAs could be impeded or prevented by interf erence with the loose components. The damage which was observed on the Palo Verde Unit 1 CEA shroud would not have prevented a reactor trip had it been present in an operating reactor.

An intensive investigative program was initiated by C-E to

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evaluate the natura 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 modeling and metallurgical examinations both at C-E and at independent testing labs. A combination of experimental and analytical results indicate the root -cause to.be. vibration which caused the f atigue cracks in localized regions with high i

stress concentration. A modified design minimizes this stress

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concentration and limits the maximum possible amplitude of the likely damaging mode of vibration.

In addition to the fatigue cracking, the other. principal I

failure mechanism was determined to be trans-granular stress corrosion cracking (TGSCC) due to concentrations of potassium hydroxide (KOH). This source of contaminant was traced to

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

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' Page ' Three

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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 concentratf ons greater than 100 ppa at reactor-operating conditions will cause TGSCC. There was no evidence of TGSCC g

in either damaged or undamaged thread areas on adjacent F

parts.. Furthermore, a ' conservative estimate determined a 1.4 ppe 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 1

subpart (vi), regarding the ' number and location of such

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components supplied to other f acilities. A copy of this report. will be transmitted to C-E.

F III.-

Corrective Action l

The corrective actions taken were in two specific areas, i.e.,

CEA guide-modifications and CEA shroud lateral support codifications, with a subsequent demonstration test to validate the adequacy of the modifications.

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CEA Guide Modifications 1

The modification consists of removing the top three inches of Lia CEA shroud and all the 4-finger and 12-finger CEA guides, j

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_ 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 with CEA insertion and the potential for resonance failure caused by vibration of-the CEA guides.

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Page Four Cutting three inches f rom the top of the CEA shroud eliminates

- the affects of the original welding of the guides. This

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

CEA Shroud Lateral Support Modifications 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 forces in the original design. Analyses indicated that 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 snubbers were added to the CEA shroud.

The snubber consists of three pieces. A snubber block assembly is shop welded into the three outermost shroud tubes on each of four 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 provide a controlled clearance with the sides of the slot in the flange block. The completed snubber assembly allows

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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 perf ormed by C-E at their Newington f acility.

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 Reference 2 provide corrective action disposition of NCRs SM2470 and SM3155.

1 i

s lHr.'T. W.' Bishop DER 83-57

-Page_Five Demonstration Test A demonstration test incorporating extensive instrumentation was performed on Unit 1 during July and August, 1984 to confirm the adequacy of the modified shroud and UGS under operating conditions 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.

A detailed description of the investigative and testing program, the results, and the physical modifications performed are included in Reference 2.~

IV.

Ref erences 1.

DCPs 1SM-RC-112, 2SM-RC-112, 3CH-RC-112 2.

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

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'84 SEP 12 P2:15 C-E Power Systems Tel. 203/688-1911 Combustion EnDeijQ([, '0ENTf.it Te'ex: 99297 1000 Prospect Hill Roaa Windsor. Connecticut 05095

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September 10, 1984 d /j d LZ h u fj V-CE 30912 nu ec fiwiv7c.d iL W w 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. Van Brunt:

Enclosed for your submittal to the Nuclear Regulatory Commission is the 10 CFR 50.55(e) report on the Palo Verde CEA Shroud along with the proprietary af fidavi t.

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 copies 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 ours,

,Lu C. Fer -

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CF/TJC:jld dd b Enclosures Resp.

cc: D. B. Amerine w/ copy 45 Mgr./ _ACG 1

W. G. Bingham w/ copy 44 Supy GCA T. R. Bradish G. A. Butterworth SCJ J. R. Bynum

_ By J. W. Dilk R. H. Holm

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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 nake this affidavit, and have reviewed or caused to have reviewed tha 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 withhciding this information.

The information for whicil 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 Palo Verde Control Element Assembly Shroud, 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 paragraph (b) (4) of Section 2.790 of the Commission's regulations, the followi'ng 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, should be withheld.

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1.

The information sought to be withheld from public disclosure are experimental data from the Palo Verde 1 Comprehensive Vibration Assessment Program (CVAP), demonstration test, and other associated laboratory tests, detailed 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 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 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 Combustion Engineering because:

c.

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A similar product is manufactured and sold by ma,inr 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 consideraole 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, The information consists of experimental data and the associated e.

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 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 Conbustion Engineering's products and services, significant' research, 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

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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 inforuation by competitors in che international marketplace would increase their ability to narket 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.

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