ML112430566

NRC Slides for Watts Bar Nuclear 2 Public Meeting

ML112430566
Person / Time
Site:	Watts Bar
Issue date:	09/01/2011
From:	NRC/RGN-II/DCP/CPB2
To:	Tennessee Valley Authority
References
Download: ML112430566 (8)

Text

TVA Heinemann Molded Case Circuit Breakers (MCCBs)

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Enclosure 4

Power Board Design:

The breakers are clamped between the front cover and the two angle iron supports in the rear.

Enclosure 4

Timeline

• 1974: Initial seismic qualification of 120Vac vital instrument power boards

• 1992: Replacement Heinemann MCCBs are Dedicated as Commercial Commercial-Grade Grade

• 2008: Heinemann redesigned breakers

• 2010: TVA installed breakers at Watts Bar Unit 2 Enclosure 4

Regulatory History 3/4January 2009: NRC questioned differences in mounting methods between the seismic testing and the installation in Watts Bar Unit 1.

3/4August 2010: Evaluation of historical Corrective Action Program (CAP) resulted in a violation for not adequately addressing the issue within their CAP.

3/4September 2010 - TVA denied the violation. Enclosure 4

Regulatory History 3/4October 2010 - NRC upheld the violation.

3/4November 2010 - TVA accepted the violation.

3/4D 3/4December b 2010 - TVA presented t d their th i corrective actions at a public meeting.

3/4July 2011 - NRC inspected TVAs corrective actions and concluded that they were not sufficient to close the NOV.

Enclosure 4

NRCs Concerns

• The MCCBs mounted during testing are not representative of the breakers clamped arrangement as installed in the plant.

• The test arrangement placed an accelerometer 13 inches below the upper-most upper most row of breakers.

breakers

• The circuit breakers, as viewed on past inspections, did not appear to firmly fit into the panel.

• The licensee used spacer materials, not documented on design drawings, as installation aids.

Enclosure 4

Projected Path Forward

• Task Interface Agreement (TIA) has been drafted by Region II and submitted to the office of Nuclear Reactor Regulation (NRR).

• After acceptance of the TIA by NRR, a public meeting will be held in Rockville, Rockville MD MD.

- Opportunity for TVA and NRC technical experts to discuss the issue.

• TIA will be finalized with all available information.

• TVA will then be able to make their decisions for Corrective Actions with knowledge of NRRs response to the TIA.

Enclosure 4

Questions?

Enclosure 4