TMI-11-128, Response to Request for Additional Information - Relief Request RR-11-01 and RR-11-02

Response to Request for Additional Information - Relief Request RR-11-01 and RR-11-02

ML112430091
Person / Time
Site:	Three Mile Island
Issue date:	08/30/2011
From:	Jesse M Exelon Generation Co, Exelon Nuclear
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RR-11-01, RR-11-02, TMI-11-128
Download: ML112430091 (11)

Text

10 CFR 50.55a TMI-11-128 August 30, 2011 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Three Mile Island Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-50 NRC Docket No. 50-289

Subject:

Response to Request for Additional Information - Relief Request RR-11-01 and RR-11-02

References:

1) Letter from D. P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "Submittal of Relief Request RR-11-01 and RR-11-02," dated February 10, 2011

2) Letter from P. Bamford (U.S. Nuclear Regulatory Commission) to M. J. Pacilio (Exelon Generation Company, LLC), "Three Mile Island Nuclear Station, Unit 1 - Request for Additional Information Regarding Third Inservice Inspection Interval Relief Requests RR-11-01 and RR-11-02 (TAC NOS.

ME5670 and ME5671 )," dated July 27,2011 In the Reference 1 letter, Exelon Generation Company, LLC (Exelon) submitted for your review two (2) relief requests associated with the third Inservice Inspection (lSI) interval for Three Mile Island Nuclear Station (TMI), Unit 1. RR-11-01 concerns requirements for examination of steam generator welds that were replaced in the fall 2009 Refueling Outage (T1 R18). RR-11-02 concerns four (4) High Pressure Injection circumferential valve to safe-end welds installed during the fall 2009 Refueling Outage (T1 R18). In the Reference 2 letter, the U.S. Nuclear Regulatory Commission requested additional information. Attached is our response.

There are no regulatory commitments in this letter.

Response to Request for Additional Information -

Relief Request RR~ 11 ~01 and RR~ 11 ~02 August 30, 2011 Page 2 If you have any questions conceming this letter, please contact Tom Loomis at (610) 765~5510.

Respectfully, Michael D. Jesse Director ~ Licensing & Regulatory Affairs Exelon Generation Company, LLC

Attachment:

Response to Request for Additional Information - Relief Requests RR-11~01 and RR-11~02 cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, TMI USNRC Project Manager, [TMI] USNRC

Attachment Response to Request for Additional Information - Relief Requests RR-11-01 and RR-11-02

Attachment Response to Request for Additional Information -

Relief Requests RR-11-01 and RR-11-02 Page 1 Question:

RR-11-01

1. Describe the specific limitations for each item as to why 100% of the required inspection volume cannot be examined, I.e., what configuration, interference or other reason prevented 100% ultrasonic examination coverage of the item in question?

Response

Figure 1 below is a duplication of Figure 1 from Relief Request RR-11-01 with annotations noting the examination limitations due to the nozzle configuration. Figure 2 below provides a steam generator lower head configuration that includes the steam generator support skirt attachment that limited examination coverage from the head shell (applicable to welds RCH0001 ASG0003N, RCH0001 ASG0004N, RCH0001 BSG0008N, and RCH0001 BSG0009N).

Figure 3 below is a duplication of Figure 2 from Relief Request RR-11-01 with annotations noting the examination limitations due to the nozzle configuration. The annotations and configuration are applicable to welds RCH0001 ASG0002N and RCH0001 BSG001 ON.

Figure 4 below provides a design configuration for weld RCH0001 BSG0030N along with limitation annotations. Figure 5 below provides an insulation configuration with annotations identifying support steel locations that limited examination coverage for weld RCH0001 BSG0030N.

As indicated in Relief Request RR-11-01, the steam generators were replaced during the 2009 refueling outage. These nozzle welds are no longer in service; therefore, application of additional examination techniques is no longer practical. The currently installed steam generators were designed to eliminate similar examination limitations.

Attachment Response to Request for Additional Information -

Relief Requests RR-11-01 and RR-11-02 Page 2 Figure 1 NDE Data Report Coverage Plot for Welds RCHOOOIASG0003N and RCHOOOIASG0004N.

Note that welds RCHOOOIBSG0008N and RCHOOOIBSG0009N are identical in design.

Scan coverage limited on upper region of head shell due to steam generator support skirt and associated integral attachment weld preventing scan surface access. See Figure 2 for skirt attachment details.

Nozzle configuration prevents ultrasonic search unit contact to allow scanning over contoured and tapered region of nozzle.

Attachment Response to Request for Additional Information -

Relief Requests RR-11-01 and RR-11-02 Page 3 Figure 2 Welds RCHOOOIASGOO03N, RCHOOOIASGOOO4N, RCHOOOIBSGOOO8N and RCHOOOIBSGOOO9N Support Skirt Interference Support skirt attachment limits scanning from lower head shell.

See Figure 1

Attachment Response to Request for Additional Information -

Relief Requests RR-11-01 and RR-11-02 Page 4 Figure 3 NDE Data Report Coverage Plot for Welds RCH0001 A5G0002N and RCH0001 85G001 ON Nozzle configuration prevents

. . - - - - - - - - - - , ultrasonic search unit contact to allow scanning over contoured and tapered region of nozzle.

Attachment Response to Request for Additional Information ~

Relief Requests RR~11~01 and RR~11~02 Page 5 Figure 4 Weld RCH0001 BSG0030N Design

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Nozzle configuration prevents ultrasonic search unit contact to allow scanning over contoured region of -1 nozzle. Note backing ring removed prior to applying outside surface weld metal.

Insulation support hardware prevented complete search unit scanning on steam generator shell. See Figure 5 for insulation support details.

Attachment Response to Request for Additional Information -

Relief Requests RR-11-01 and RR-11-02 Page 6 Figure 5 Weld RCH0001 BSG0030N Insulation Installation

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Attachment Response to Request for Additional Information -

Relief Requests RR~ 11 ~01 and RR~ 11 ~02 Page 7 Question:

RR~11~02

1. The submittal states that due to valve geometry, code coverage is limited to 50%. Please describe Exelon's best effort attempt to achieve maximum coverage in/through the cast austenitic stainless steel portion of these welds.

Response

TMI, Unit 1 completed the ultrasonic examination per procedure, PDI~UT~2, Revision C, which describes the actions for single sided weld examination. The actions completed are:

6.7.2.1 For components where access is limited to a single side of the component, the following additional factors shall be considered:

a.) For the inspection of the same side weld volume, the techniques and processes defined for dual sided access shall be utilized.

b.) When accessibility is limited to a single side in materials equal to or less than 0.50" thick, a 2.25 MHZ, 70" shear wave search unit shall be used for the detection and length sizing of flaws on the far side of the weld.

While not POI qualified for detection of flaws on the far side of an austenitic weld, the 70" shear wave examination interrogates the far side of the weld along with a lower adjacent segment of the Cast Austenitic Stainless Steel (CASS) valve body. There are no additional ultrasonic examination methods beyond the techniques described that will provide meaningful and reliable examination results. The valve body is constructed of A351-CF8M material (CASS) for which there are no ASME Section XI, Appendix VIII/Performance Demonstration Initiative qualified examination techniques. Current UT examination techniques have not demonstrated reliable performance in CASS material due to sound attenuation. The valve configuration has a tapered transition at the edge of the weld and a continuously changing outside surface contour which limits ultrasonic search unit contact (see Figure 6 below).

Attachment Response to Request for Additional Information -

Relief Requests RR-11-01 and RR-11-02 Page 8 Figure 6 Valve to Safe End Valve Configuration Question:

2. A pre-replacement typical valve to safe-end configuration was provided. Has the configuration changed post-replacement?

Response

There is no change to the valve configuration. The safe-end design, however, was modified to move the safe-end outside surface taper further away from the valve to allow full examination coverage of the safe-end side of the weld including adjacent base material. The removed safe-end did not provide adequate surface area for UT examination on the safe-end side of the weld.

This resulted in the pre-service examination coverage improvement when compared to the original configuration.