attn: document control desk · license amendment and exemption lar 15-08 s1: supplemental...

April Rice Manager

Nuclear Licensing

SCE&G New Nuclear Deployment ● P. O. Box 88 ● MC 846 ● Jenkinsville, South Carolina 29065 ● www.sceg.com

September 23, 2015 NND-15-0568

10 CFR 50.90

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Virgil C. Summer Nuclear Station (VCSNS) Units 2 and 3 Combined License Nos. NPF-93 and NPF-94 Docket No. 52-027 Subject: Preliminary Amendment Request (PAR) 15-08: Supplemental Requirements for

Mechanical Coupler Weld Acceptability Reference: 1. South Carolina Electric & Gas Company (SCE&G) Request for License Amendment

and Exemption LAR 15-08: Supplemental Requirements for Mechanical Coupler Weld Acceptability, August 24, 2015 (NND-15-0518) (ML15236A344)

2. Notice of No Objection for Preliminary Amendment Request (PAR 15-010), “Supplemental Requirements for Mechanical Coupler Weld Acceptability” for the Vogtle Electric Generating Plant Unit 3, September 21, 2015 (TAC NO. RP9514) (ML15254A505)

3. South Carolina Electric & Gas Company (SCE&G) Supplement to Request for License Amendment and Exemption LAR 15-08 S1: Supplemental Requirements for Mechanical Coupler Weld Acceptability, September 23, 2015 (NND-15-0567)

In accordance with the provisions of 10 CFR 50.90, South Carolina Electric & Gas Company (SCE&G) submitted a request for license amendment to the Virgil C. Summer Nuclear Station (VCSNS) Units 2 and 3 combined licenses (COLs) numbers NPF-93 and NPF-94, respectively. The requested amendment (LAR 15-08) was submitted as indicated in the reference list above, to depart from VCSNS Units 2 and 3 Tier 2* and Tier 2 material contained within the Updated Final Safety Analysis Report (UFSAR) to specify supplemental requirements for confirming the acceptability of mechanical couplers with combined partial joint penetration (PJP) welds and fillet welds.

SCE&G is submitting a Preliminary Amendment Request, PAR 15-08, to avoid possible construction delays for Unit 2 during the NRC’s evaluation of the related license amendment request. The determination of whether the NRC has any objection to SCE&G proceeding with construction based on the proposed plant licensing basis changes identified in the LAR is requested on or before September 30, 2015. Construction of VCSNS Unit 2 seismic Category I and II structures containing non-accessible mechanical couplers subject to the changes proposed in LAR 15-08 could be delayed by a delayed determination regarding this PAR.

A description of the proposed change and the reason for the change are contained in Enclosure 1 to this letter. This PAR has been developed in accordance with guidance provided in the most recent revision to the Interim Staff Guidance on Changes during Construction Under 10 CFR Part 52, COL-ISG-25 [ML15058A377], and corresponds accurately and technically with the above-mentioned LAR15-08. The

Document Control Desk NND-15-0568 ,~~ A-

of 3 1:'" .... . ,.

technical scope of this PAR is consistent with the technical scope of the submitted LAR. Section 7 of Enclosure 1 identifies the scope of the "no objection" sought in this PAR.

This letter contains no regulatory commitments.

Should you have any questions, please contact Mr. Justin Bouknight, Supervisor, Nuclear Licensing, at (803) 941-9828.

I declare under penalty of perjury that the foregoing is true and correct.

MMD/ARR/mmd

.,J Executed on this ~3 day of S~t~~2015.

Sincerely,

yJ~ April Rice Manager Nuclear Licensing

Enclosure 1: Virgil C. Summer Nuclear Station Unit 2 - Preliminary Amendrt)i~nt Request Regarding ., :1 ... . ~ • • ., -1 . '-, . ' ••

Supplemental ReqUirements for Mechanical Coupler Weld Acceptability (PAR 15-08)

Document Control Desk NND-15-0568 of 3

copy (with enclosures): Billy Gleaves Ruth Reyes Chandu Patel Paul Kallan [email protected]

copy (without enclosures): Tom Fredette Tomy Nazario Victor McCree Jim Reece Stephen A. Byrne Jeffrey B. Archie Ronald A. Jones Alvis J. Bynum Kathryn M. Sutton April Rice Justin Bouknight Matt Kunkle Mory Diané Bryan Barwick Dean Kersey Kyle Young Stephen Mothena Margaret Felkel Cynthia Lanier Kristin Seibert Amanda Pugh Neil Haggerty Joel Hjelseth Carl Churchman Pat Young Michael Frankle AJ Marciano Sean Burk Zach Harper Brian McIntyre Brian Bedford Joseph Cole Chuck Baucom Lisa Alberghini Curt Castell Ken Hollenbach Susan E. Jenkins William M. Cherry Rhonda O’Banion VCSummer2&[email protected] vcsummer2&[email protected]

South Carolina Electric and Gas Company

NND-15-0568

Enclosure 1

Virgil C. Summer Nuclear Station (VCSNS) Unit 2

Preliminary Amendment Request

Regarding

Supplemental Requirements for Mechanical Coupler Weld Acceptability

(PAR 15-08)

NND-15-0568 Enclosure 1 PAR 15-08: Supplemental Requirements for Mechanical Coupler Weld Acceptability

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Pursuant to 10 CFR 50.90, South Carolina Electric and Gas Company (SCE&G) requested an amendment to Combined License (COL) Numbers NPF-93 and NPF-94, for Virgil C. Summer Nuclear Station (VCSNS) Unit 2 and 3, respectively. Accordingly, SCE&G requests the determination of whether the NRC has any objection to proceeding with the construction of the VCSNS Unit 2 seismic Category I and II structures containing mechanical couplers welded to structural steel utilizing combined partial joint penetration (PJP) weld with fillet weld reinforcement with fillet welds satisfying the minimum size requirements for C2/C3J couplers established by the analyses and testing, as identified in the Preliminary Amendment Request (PAR) provided below to be provided by the date shown below. PAR Number

PAR 15-08

Station Name VCSNS

Unit Number

2 3

PAR Date 09/23/15

1. NRC PAR Notification Requested Date (see Block 7 for basis) September 30, 2015

2. License Amendment Request References (as applicable)

LAR su bmittal date and SCE&G Correspo ndence Nu mber: August 24, 201 4 / NND-1 5-0518 – Reference 1 (Supplemented on September 23, 2015 by letter NND-15-0567 – Reference 3)

Expected LAR submittal date:

3. Brief Description of Proposed Change

This proposed change would revise th e licensing basis, specifically the Co mbined Licenses’ Updated Final Safety Analysis Report (UFSAR) description of supplemental requirements for concrete structures to include a description of supplemental requirements for demonstrat ing the acceptability of weldable coupler connections of re inforcing b ar (re bar) to stru ctural steel, includin g structu ral steel shap es, embedded plates, overlay plates, and structural module liner plates.

Weldable mechanical couplers (couplers) are used in the AP100 0 design where rebar are attache d to structural ste el. The cou plers are attach ed to the stru ctural st eel usi ng a combined partial joint penetration (PJP) wel d with fillet weld reinfo rcement. The C2/C3 J type of coupl er is use d i n containment internal structures, other seismic Category I structures, and the seismic Category II portion of the annex building located adjacent to the nuclear island.

The analysis and design of concrete a nd structural steel conform to American Concrete Institute (ACI) 349-01, “Co de Re quirements for Nuclear Safety Rela ted Con crete Stru ctures,” (ACI 3 49-01) an d American Institute of Steel Con struction (AISC) N690-1994, “Specification for t he Design, Fabrication, and Erection of Steel Safety-Related Structures for Nuclear Facilities,” (AISC N690-1994), respectively. The coupler weld strength is evaluated in accordance with AISC N690-1994 and ACI 349-01.

Load combinations f rom UFSAR Tables 3. 8.4-1 a nd 3.8.4 -2, and the corresp onding S tress Li mit Coefficients (SLCs), are used in the evaluation of coupler weld capacity. The coupler weld capacity for all si zes of C2/C3J coup lers i s fou nd to b e acceptable when co mpared t o de mand f or all lo ad combinations.

To demonstrate the adequacy of mechanical connections (rebar-coupler), ACI 349-01 requires that a full mechanical connection (rebar-coupler) develop at least 125% of the specified yield strength of the rebar. ACI 349-01 does not provide requirements on weld qualification.

LAR 15 -08 (Reference 3), pro poses a Tier 2* UFSAR ch ange to en hance the supplem ental requirements for con crete stru ctures in UFSAR subsection 3.8.4.5.1 to demon strate 1 25% of the specified yield strength of the rebar as follows:


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PAR Number

PAR 15-08

Station Name VCSNS

Unit Number

2 3

PAR Date 09/23/15

The required weld capacity of C2/C3J couplers for #4, #5, and #6 rebar sizes is demonstrated through analysis in accordance with AISC N690-1994 requirements, using an SLC of 1.6,

The coupler connection weld ade quacy for C2/C3 J couplers for rebar sizes #7 through #11 i s demonstrated thro ugh test ing, a s p ermitted by AISC N6 90-1994, Sectio n Q 1.0.1, and mo re specifically, Section Q1.22.2. Two sets of testing are pe rformed to d emonstrate that the strength of th e reinfo rcing bar i s the lim iting f eature of the co upler reinforcing bar splice and weld system:

(1) Six static te nsion test s a re pe rformed for e ach rein forcing b ar si ze on samples of the coupler reinforcing bar splice and weld system, retaining the 90%/95% upper confidence limit of the coupler system static tension test results. Three cyclic tests are also performed as described in ACI 349-0 1 12.14.3.4.1(b) to co nfirm that there is not significa nt coupler system degradation under cyclic demand.

(2) Static tension testing of th e coupler weld to failure using ten representative sample weld configurations fro m ea ch of the five reinfo rcing bar coupler sizes i s performed to determine the 90%/95% lower confidence limit weld capacity.

The proposed UFSAR Tier 2* change also identifies the factors of safety demonstrated by the coupler connection weld testing, and spec ifies the minimum fillet weld si zes for C2/C3J couplers established by the analyses and testing, as follows:

C2/C3J Coupler Size #4 #5 #6 #7 #8 #9 #10 #11

Minimum Fillet Weld Size (inches) 1/4 1/4 1/4 1/4 1/4 5/16 1/4 3/8

The propo sed cha nge al so inclu des the addition of Ti er 2 text summari zing the tests p erformed to demonstrate the acce ptability of non-conforming fill et weld rei nforcement on #9 a nd # 11 cou plers identified in module CA20.

4. Reason for License Amendment Request

These ch anges are drive n prima rily by a need to identify and define in the UFSAR the applica ble requirements and criteria for analyzing and demonstrating the strength of the combined PJP weld with fillet weld reinforcement used to attach couplers to structural steel.

The analysis and design of concrete and structural steel conform to ACI 349-01, “Code Requirements for Nuclear Safety Related Concrete Structures,” and AISC N690 -1994, “Specification for the De sign, Fabrication, and Erectio n of Steel Safety-Relate d St ructures for Nu clear Facilitie s,” re spectively. Coupler weld strength is evaluated in accordance with AISC N690-1994 and ACI 349-01.

AISC N69 0-1994 i s the g overning cod e for weld d esign. Loa d combi nations from UFSAR Tabl es 3.8.4-1 and 3.8.4-2, and the corresponding Stress Limit Coefficients (SLCs), are cu rrently used in th e evaluation of cou pler weld ca pacity. The coupl er weld capacity for all si zes of C2/C3 J couplers i s found to be a cceptable when compared to demand for all load co mbinations calculated in accordance with UFSAR and AISC N690-1994 requirements.

The requi rements fo r m echanical a nchorage of rein forcing steel are p rovided in A CI 349-01. As applicable to the co upler-rebar splice system, a splice ma de by full mech anical connection must develop 125% of the specified yield strength of the reinforcing steel as required by ACI 349-01 Section 12.14.3.4. Testing of wel ds is pe rformed to demonstrate that the we ld strength exceeds 125% of the specified yiel d strength of the rei nforcing ba r. It is also a cceptable to demonstrate ad equate weld strength by evaluation to AISC N690-1994 Table Q1.5.7.1 stress limits for 12 5% of the spe cified yield


Page 4 of 5

PAR Number

PAR 15-08

Station Name VCSNS

Unit Number

2 3

PAR Date 09/23/15

strength of the reinforcing bar. If the AISC N6 90-1994 Table Q1.5.7.1 stress limit analytical approach is u sed, a n SLC of 1.6 i s ap plied. For rebar sizes # 4, #5, a nd #6 C2/C3J coupl ers, analytical evaluation of the weld using an SLC of 1.6 shows that the weld strength exceeds 125% of the specified yield strength of the rebar. Larger bar size couplers (sizes #7, #8, #9, #10, and #11) are evaluated by testing.

5. Is an Exemption Request Required? Yes No

If Yes, Briefly Describe Reason for Exemption

Not Applicable

6. (Optional) Identify Applicable Precedents Reference 2: Notice of No Objection for Preliminary Amendment Request (PAR 15-010), “Supplemental Requirements for Mechanical Coupler Weld Acceptability” for the Vogtle Electric Generating Plant Unit 3, September 21, 2015 (TAC NO. RP9514) (ML15254A505)

Reference 2 is an applicable precedent for a portion of the scope requested by this PAR. Specifically, it is applicable to Activity #1 identified in Section 7 below.

7. (As needed) Impact of Change on Installation and Testing Schedules

SCE&G’s requested date for approval of this license amendment as identified in the referenced LAR (Reference 3) is November 15, 2015. This date is based primarily upon the time period required for processing a requested license amendment. Construction activities of structural modules adversely affecting the accessibility of couplers meeting the minimum fillet weld requirements and installed in non-accessible locations are currently placed in a “construction hold” status.

As such, this PAR requests a “no objection” finding related to this license amendment by the date identified in Block 1 above (or sooner if reasonably achievable) to allow for appropriate notifications and release of related welding activities currently under the “construction hold” status to allow construction to continue.

Activity #1: Specifically, SCE&G requests a “no objection” finding to allow concrete fill in Unit 2 structural module CA20 in accordance with the coupler weld change proposed in the revised UFSAR description in LAR 15-08 (Reference 3).

Activity #2: SCE&G also requests a “no objection” finding to allow the installation of the shield building internal and external wall panels from EL 113'6''-131'6''. This installation includes the placement of panel and their welding to other adjacent panels.

A “no objection” finding for the above construction activity would release the associated Unit 2 construction holds.

8. Impact of Change on ITAAC

None 9. Addition al Information

None


10. Preparer Name (Print) 12. Date f"

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13. Reviewer Name (Print) 15. Date

rtA 4' 1\ Bou.~; l+- q -"23- 15 16. Approver Name (Print) 17. Approver Signature 18. Date

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