NL-14-1193, Response to Request for Additional Information Regarding Proposed Alternative to Lnservice Inspection Requirements of ASME Code Case N-770-1

Response to Request for Additional Information Regarding Proposed Alternative to Lnservice Inspection Requirements of ASME Code Case N-770-1

ML14213A484
Person / Time
Site:	Farley
Issue date:	08/01/2014
From:	Pierce C Southern Co, Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-14-1193
Download: ML14213A484 (6)

Text

Charles R. Pierce Southern Nuclear Regulatory Affairs Director Operating Company, Inc.

40 Inverness Center Parkway Post Office Box 1295 Birmingham, AL 35242 Tel 205.992.7872 Fax 205.992 .7601 sou August 1, 2014 Docket Nos.: 50-348 NL-14-1193 50-364 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington , D. C. 20555-0001 Joseph M. Farley Nuclear Plant Response to Request for Additional Information Regarding Proposed Alternative To lnservice Inspection Requirements of ASME Code Case N-770-1 Ladies and Gentlemen:

By letter dated March 24, 2014, the Southern Nuclear Operating Company (SNC) submitted proposed alternative FNP-ISI-AL T-15 , Version 1 to the inservice inspection requirement of ASME Code Case N-770-1 for the reactor pressure vessel cold leg nozzle dissimilar metal welds for Joseph M. Farley Nuclear Plant (Farley) , Units 1 and 2, during the fourth inservice inspection interval. By letter dated July 2, 2014, the Nuclear Regulatory Commission (NRC) sent SNC a Request for Additional Information (RAI) letter. The Enclosure provides the SNC response to the NRC RAI.

This letter contains no NRC commitments. If you have any questions, please contact Ken McElroy at (205) 992-7369 .

.Sincerely,

t. J(. ~

C.R. Pierce Regulatory Affairs Director CRP/ RMJ/Iac

Enclosure:

SNC Response to NRC RAI

U.S. Nuclear Regulatory Commission NL-14-1193 Page2 cc: Southern Nuclear Operating Company Mr. S. E. Kuczynski, Chairman, President & CEO Mr. D. G. Bast, Executive Vice President & Chief Nuclear Officer Ms. C. A. Gayheart, Vice President - Farley Mr. B. L. lvey, Vice President- Regulatory Affairs Mr. D. R. Madison, Vice President- Fleet Operations Mr. B. J. Adams, Vice President- Engineering Mr. R.R Martin, Regulatory Manager - Farley RTYPE: CFA04.054 U.S. Nuclear Regulatory Commission Mr. V. M. McCree, Regional Administrator Mr. S. A. Williams, NRR Project Manager- Farley Mr. P. K. Niebaum, Senior Resident Inspector- Farley Mr. K. E. Miller, Resident Inspector- Farley

Joseph M. Farley Nuclear Plant Response to Request for Additional Information Regarding Proposed Alternative To lnservice Inspection Requirements of ASME Code Case N-770-1 Enclosure SNC Response to NRC RAI

Enclosure to N L-14-1193 SNC Response to NRC RAI NRC RAJ#1 Provide detail description of the geometric and surface conditions of the ASME Code required inside diameter (I D) surface area of the subject DM welds examined by the eddy current testing (ET) .

SNC Response to NRC RAJ #1 The dissimilar metal (OM) welds are shop welds and essentially have a flat surface across the DM weld volume. The figure below is an outline of the contour for the Farley Unit 1 Cold Leg , Loop 1; this configuration is representative of each Farley Unit 1 and Unit 2 reactor pressure vessel (RPV) Cold Leg. The weld on the left is the DM weld . The weld on the right is the stainless to stainless weld (field weld) .

-0.5

'I I  ! I 0.0 I

-t I i\ *

/-~

o.s Distance from ID in inches I - I I I\

1.0 ~

! r- \ -~ ~ ~

1.5 Nozzle DM J eld Safe End *B-J Weld 2.0 I I I

11 5.0 11 6.0 117.0 I

11 8.0 119.0 120 .0 I

12 1.0 122.0 12).0 1 2~ . 0 125.0 Distance from RPV centerline in inches

--Surface Contour of ID

--'."'e c;, to f gv.c.. . . o NRC RAJ #2 Discuss whether the full exam ination coverage of the ASME Code required surface area of the DM welds was obtained when performing the ET from the ID surface.

SNC Response to NRC RAJ #2 Full examination coverage was obtained . A summary of the review of the ASME coverage for each DM Cold Leg Weld and the results are recorded in the following table . In addition , coverage area for ET from the ID surface is also included for each RPV Cold Leg DM Weld .

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Enclosure to NL-14-1193 SNC Response to NRC RAI Weld# I Description ASME Code required ET Coverage Obtained volumetric examination ALA1-4100-14DM I Unit 100% 100%

1 Inlet Nozzle DM at 335° ALA1-4200-14DM I Unit 100% 100%

1 Inlet Nozzle DM at 215° ALA 1-4300-14DM I Unit 100% 100%

1 Inlet Nozzle DM at 95° APR1-4100-14DM I Unit 100% 100%

2 Inlet Nozzle DM at 335° APR1-4200-14DM I Unit 100% 100%

2 Inlet Nozzle DM at 215° APR1-4300-14DM I Unit 100% 100%

2 Inlet Nozzle DM at 95° NRC RAI#3 Describe the qualification process used for the ET procedure.

SNC Response to NRC RAI #3 The qualification process for the ET procedure included a technical justification in accordance with European Network for Inspection Qualification (ENIQ) guidelines and a practical trial. The procedure qualification trials were performed in 2003 on a nozzle to safe end test specimen supplied by Ringhals AB. The trials were proctored and the technical justification was reviewed and approved by the Swedish Qualification Centre (SQC), an inspection qualification body. The trials were conducted in a non-blind manner. The test specimen (clad SA508 carbon steel forging, buttered with Alloy 600 material, and welded to a SA312 Type 316 stainless steel forging) included 10 ID-surface connected branch cracks ranging in depth from 0.24" (6.1mm) to 1.33" (33.7mm) and in length from 0.67" (17.1 mm) to 2.78" (70.5mm) and located in the weld and in the buttering. Parametric evaluations were also performed on other test specimens containing fatigue cracks as small as 0.04" (1 mm) deep by 0.24" (6mm) long located in the center of an Alloy 182 weld. The target flaw for detection by the ET process was 0.04" (1 mm) deep by 0.24" (6mm) long ID surface connected crack oriented either parallel or transverse to the weld.

Inspection personnel were then required to undergo blind qualification trials using the approved procedure. These personnel qualification trials included collected data from a test specimen similar to that used in the procedure qualification trial.

Additionally, SQC required a procedure technique verification on supplemental test specimens containing flaws representing intergranular stress corrosion cracking (IGSCC)I interdendritic stress corrosion cracking (IDSCC) conditions. These specimens were made as part of the sac investigation of the E-2

Enclosure to NL-14-1193 SNC Response to NRC RAI degradation mechanism. In this verification, the test specimens were scanned and the data interpreted in accordance with the qualified procedure.

Qualification documentation for the procedure stated that the ET capability is capable of detecting fatigue and IGSCC/IDSCC cracks 0.04" (1mm) deep by 0.24" (6mm) long and of length sizing such cracks within a range of +/- 0.39" (+/-

10mm).

NRC RAI #4 What is the longest and deepest ID surface-connected flaw that the ET procedure would not be qualified to detect?

SNC Response to NRC RAI #4 The ET procedure is qualified to detect fatigue and IGSCC/IDSCC cracks having a depth of 0.04" (1 mm) and greater and a length of 0.24" (6mm) and greater. As such, an ID surface connected flaw with less than 0.04" (1 mm) in depth and 0.24" (6mm) in length is not qualified for detection.

It is important to note that ET is primarily used in detecting very small surface breaking flaws and not for depth sizing. The vendor procedure requires an indication with a length of 0.25" or greater to be recorded. There is no minimum depth requirement. In relation to the postulated flaw evaluation previously provided, an axial flaw aspect ratio (flaw length/flaw depth) of 2:1 is conservatively assumed in the crack growth analysis, since axial flaw growth due to primary water stress corrosion cracking (PWSCC) is limited to the width of the DM weld. Based on the assumed aspect ratio and minimum flaw reporting length, a 0.125" deep initial flaw assumption would be consistent and reasonable for the initial flaw depth. SNC's use of a postulated initial flaw size of 7.5% (or 0.245") used in the PWSCC Crack Growth Curve for Farley Units 1 and 2 Reactor Vessel Inlet Nozzle DM Welds is conservative for the RPV Cold Leg examinations, since this initial depth assumption corresponds to a 1:1 aspect ratio for initial flaw depth assuming the minimum recordable length detected by ET. In addition to the ET examinations, volumetric examinations are performed concurrently as required by ASME Code Case N-770-1.

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