Saturday, April 08, 2017

Junk Plant Watts Bar 2: A Main Condenser Collapsed  

This has been nightmare since first start-up.
TVA investigates failure of condenser at Watts Bar nuclear unit
Washington (Platts)--7 Apr 2017 423 pm EDT/2023 GMT

Workers still are developing a repair plan for Tennessee Valley Authority's new 1,210-MW Watts Bar-2 nuclear generating unit in Spring City, Tennessee, after a condenser failure shut it last month, a spokesman said Friday.

TVA is investigating the cause of the structural failure of a portion of the steel condenser and repairs will involve reinforcing the structure, Jim Hopson said in an email.

The condenser is the part of the plant where steam from the turbines cools and turns back into water that can be sent back into steam generators.

"[S]ome of the structural supports within the condenser did not operate as designed," Hopson said. Those supports must be repaired and reinforced as part of a plan to return the condenser to service, he said.
That plan is being developed, and TVA does not have an estimate for the return to service of the unit, Hopson said.

Because of limited space inside the condenser, the assessment is taking longer than expected, he said.

Watts Bar-2 shut March 23 while it was starting up from an outage to check condenser and feedwater pumps. The unit shut immediately after synchronizing to the grid as condenser vacuum was lost, TVA said in an event report to NRC that day.

The 'B' waterbox of the condenser experienced a structural failure tripping the main turbine, NRC said in a preliminary report March 23. This allowed steam to enter into the main turbine hall, resulting in closure of the main steam isolation valves at the unit, the report said. Operators manually shut the unit after the incident.

Waterboxes are part of the condenser containing cooling water from the ultimate heat sink, which, in this case, is river water.

Watts Bar-2 is the newest nuclear unit in the US, having entered commercial operation in October. The unit had been "running like a top," TVA President and CEO Bill Johnson told reporters February 1.

Construction of Watts Bar-2 began in the 1970s but was suspended for two decades before TVA decided in 2007 to complete the unit.

The adjacent 1,210-MW Watts Bar-1 has been shut since March 18 for refueling and maintenance. The repair plan for the unit 2 condenser is being designed to avoid affecting the unit 1 refueling outage, Hopson said.

The US Nuclear Regulatory Commission is following TVA's repair activities, but the condenser is not considered a safety-related component, so the agency will not need to approve the federal power producer's root cause analysis before restart, agency spokesman Roger Hannah said Friday.

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