ML112430566
| 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)
(
)
Power Board Design:
The breakers are clamped between the front cover and the two angle iron supports in the rear.
Timeline
- 1974: Initial seismic qualification of 120Vac vital instrument power boards
- 1992: Replacement Heinemann MCCBs are Dedicated as Commercial Grade are Dedicated as Commercial-Grade
- 2008: Heinemann redesigned breakers
- 2010: TVA installed breakers at Watts Bar Unit 2
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.
Regulatory History 3/4October 2010 - NRC upheld the violation.
3/4November 2010 - TVA accepted the violation.
3/4D b
2010 TVA t d th i 3/4December 2010 - TVA presented their 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.
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 row of breakers inches below the upper most row of 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.
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 MD meeting will be held in Rockville, 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.
Questions?