NG-97-2068, Submits Addl Justification for ISI Relief Request NDE-R004, Per 10CFR50.55a(a)(3)(ii)

Submits Addl Justification for ISI Relief Request NDE-R004, Per 10CFR50.55a(a)(3)(ii)

ML20203E847
Person / Time
Site:	Duane Arnold
Issue date:	12/05/1997
From:	Peveler K IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT
To:	NRC (Affiliation Not Assigned), NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NG-97-2068, NUDOCS 9712170205
Download: ML20203E847 (5)

Text

Du::ne Amold Energy Conter .

., I* , 3277 DAEC Foad Mo. tA 52324 Telephone 319 8517611 Fax 319 8517611 UTILITIES December 5,1997 NG-97-2068 Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Atta: Document Control Desk Mail Station PI-37 Washington, DC 20555-0001

Subject:

Duane Arnold 'Jnergy Center Docket No: 50-331 Op. License No: DPR-49 Additional Justification for Inservice inspection Relief Request NDE-R004

Reference:

Letter dated October 15,1997, NG-97-1802, from Kenneth E. Peveler (IES) to NRC, Third 10-Year Interval inservice Inspection Relief Request NDE-R004 File: A-100, A-286 The referenced letter submitted a revision to Duane Arnold Energy Center (DAEC) inservice inspection (IS!) relief request NDE-R004. The revision modities the requirement for radiographic examinations of a non-Code repair on the outboard "D" main steam isolation valve (MSIV). The StafThas requested additionaljustification regarding the revision. Relief tequest NDE-R004 has been modified to include this justification and is attached.

As discussed in the attached relief request, the required radiographic examinations would require disassembly of outboard "D" MSIV, resulting in hardship or unusual difliculty without a compensating increase in the level of quality and safety. Therefbre, reliefis requested in accordance with 10CFR 50.55a(a)(3)(ii).

AD i 9712170205 971205 AI5!N.lllIllI[Illl$,y//

PDR ADOCK 05000331 G PDR m

• 4 V An !ES Industnes Company

_, NG 97-2068 December 5,1997 ,

Page 2 Sh6uld you have any questions agarding this matter, please contact this office.

Sincerely, h w xC l.

Kenneth E. Peveler Manager, Regulatory Performance Attachment ec: C. Rushworth L.Roon J. Franz D. Wilson G. Kelly (NRC-NRR)

P. Ray (NRC-NRR)

A. H. Beach (Region Ill)

NRC Resident Office Docu i

p

=*  :

. Attachment to -

NG-97-2068 -

Page1of3 RELIEF REQUEST NUMBER: NDE-R004 (RR-002) >

- COMPONENT IDENTIFICATION Code Class: 1

References:

IWA-4000 iWB 4000,IWB-4120 Examination Category: B M-2 Item Number: B 12.50 .

Description:

Valve bodies Exceeding NPS 4" Casting Repairs Component Numbers: Main Steam Isolation Valve "D" Outboard, CV-4421 CODE REOUIREMENT ASME Section XI IWA-4000, requires repairr, to be performed in accordance to the owner's design specification and constructior. code. lWB-4120, requires the complete removal of the defect or flaw. lWB-4230, after final grinding, cavities prepared for L welding, shall be examined by magnetic particle or liquid penetrant to ensure indications o have been reduced to an aceptable limit in accordance with IWA-3000.

HASIS FOR RELIEF The subject MSIV is an ASME Section XI Class 1 valve, the body is fabricated from ASTM /ASME SA-216, grade WCB, cast carbon steel, procured under GE Specification 21 A9230 Rev. 2. The unacceptable defect was uncovered during a routine maintenance machining operation to correct unacceptable seat leakage. The indication was determined

- to be a subsurface casting shrinkage brought to the surface by the re-boring operation.

An evaluation of the original construction radiographs confirmed the presence of the

- subsurface defects and that the flaws were acceptable to the radiography requiremer.ts.

A code repair to the MSIV would require a post-weld heat treatment (PWHT) of the valve body casting. Prior experience with PWHT has demonstrated that unacceptable distortion of the valve body may occur, Correction of the distortion may not be feasible.

Application ofimbedded flaw acceptance criteria r.fter perfomiing a weld overlay in the

- alTected area should demonstrate acceptable structural integrity.

Attachment to NG-97-2068 Page 2 of 3 IES Utilitii:s requested assistance from the EPRI Non-Destructive Examination (NDE) Center to develop an NDE technique for examination of the internal repair. EPRI reviewea the valve geometry and the details of the repair and determined that an ultrasonic examination of the valve from the outer diameter would not be reliable. Because of the wall thickness. the only feasible method of exenining the hiSIV repair area is with single-wall radiography, requiring the valve to be disassembled.

Disassembly of the "D" outboard h1SIV solely for the purpose of performing a radiograph is undesirable for the following reasons:

. As discussed in the NRC safety evaluation transmitted by letter dated December 27,1994 (Norrholm (NRC) to Liu (lES)),"Per the f' m dings of NUREG-1169, excessive valve disassembly should be avoided if the leak tightness of valves such as hiSIVs is to be optimum. Disassembly for no other reason than to perform a radiograph (necessary in this case due to overall valve size and thickness)is contrary to the guidance oft he NUREG."

• The DAEC has learned from extensive experience that an hiSIV can not just be taken apart and put back together. It requires extensive in;pection, machining, grinding, and possible weld repair prior to reasssembly to ensure the lowest practical leakage levels. This effbrt requires e igineering personnel, mechanics, and machinists, unnecessarily diverting these resources from other outage projects.

• The disassembly and reassembly would result in the unnecessary expenditure of both resources and exposure. Simple disassembly and reassembly costs about $20,000 and results in approximately 0.5 rem exposure. Refurbishment, including parts and labor, could increase the cost by approximately $60,000.

. The h1SIV is .ocated in the Steam Tunnel, a contaminated and congested work area containing extensive safety-related equipment. During the performance of the RT all other work in the Steam Tunnel is deferred, delaying work activities on other equipment.

The radiography performed during RFO 12 indicated resolution of the IT hole in a !!40 penetrameter which represents a sensitivity of 1.26% Since no indication is visible, a conservative estimate of the remaining Daw size may be obtained by assuming the Daw to be the size of the smal'.est hole in the penetrameter which was resolved. The size of the remaining Haw can therefore be conservatively estimated as 1.26% of wall thickness. Since the wall is about 3.175 inches thick, the Daw size is bounded by approximately 0.04 inches.

A tlaw evaluation was performed in accordance with Appendix A of AShiE Section XI 1980 with the Winter 81 Addenda. The evaluation was performed for several aspect ratios (1/6,1/4.

1/3, I/2). The size (0.04 inch), length (2 inches) and aspect ratio (1/100) of the predicted flaw detectable by the radiography technique is bounded by the Haw evaluation.

Attachment to NG-97-2068 Page 3 of 3 Since the predicted flaw is bounded by the evaluation, disassembly of the outboard "D" MSIV solely to perform a radiographic examination would result in undue hardship or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, reliefis requested in accordance with 10CFR 50.55a(a)(3)(ii).

AI, TERNATE EXAMINATION The flaw was excavated to a depth not exceeding 20% of the wall thickness (0.6 inch in this case). A magnetic particle examination (MT) was performed to document the remaining flaw dimensions. Using a 200 F preheat, a low heat input, multi-pass veld was perfomied to fill the excavated cavity. "' eld intep.ity was verified by performing a visual examination and hot MT of each layer of the weld naal. Shielded metal are welding (SMAW) using small diameter electrodes was employed. The fluxing action of the SMAW electrodes (E7018 in this case) would aid in removal of any casting impurities that may have beer ment in the flawed area.

After machining of the weld was completed, an MT of the machined surface was performed.

The repaired area was radiographed to verify that no defects existed in the weld deposit and that the casting around the repaired area met the original construction code. Structural integrity for the remaining embedded flaw was demonstrated by perfomiing bounding analyses using the appropriate Section XI embedded flaw evaluation methods. The radiography used for the repair was capable of resolving a flaw size of 1.26% of the wall thickness. This size flaw is bounded by the flaw evaluation which determined that the flaw sizes were acceptable for 40 years of operation per the requirements oflWB-3600 of ASME Section XI 1980 Edition with the Winter 81 Addenda.

l One more radiographic inspection of the non-code repair area on the "D" outboard MSIV will be perfbrmed when the valve is disassembled Ihr other reasons. The inspection results will be compared with the previous results per IWB-3121.

APPL.ICAHl.E TIME PERIOD This relief will be used during the third ten-year interrd of tne Insenice Inspection Program for

! the DAEC.

!