some text The cooling tower of the single operating reactor at the Watts Bar Nuclear Plant belches steam in Spring City, Tenn.

The TVA vice president in charge of Watts Bar Nuclear Plant abruptly left the employment of TVA today, but TVA officials will not say why.

"Timothy Cleary will serve as acting site vice president for Watts Bar Nuclear Plant, effective immediately. Cleary replaces Don Grissette." said TVA spokesman Ray Golden on Thursday.

Golden said TVA will not elaborate on Grissette's departure.

The news comes on the same day that TVA is announcing Watts Bar worker incentives if the behind-schedule, over-budget new reactor there can be made operational by the end of the 2015.

Construction on Watt's Bar Nuclear Plant's second reactor - in February announced to as much as $2.5 billion over budget and three years behind completion schedule - is now so improved that TVA is offering workers there an incentive bonus if the good work continues, according to TVA's nuclear construction chief, Mike Scaggs.

If the new reactor is operational by Dec. 31, 2015, and its cost is no more than $3.875 billion to $4.4 billion, each of an estimated 3,000 workers, depending on how long they worked, could receive a flat bonus ranging from about $1,500 to $37,500, Skaggs said.

"We've gained traction," he said of work at the plant since earlier this year when workers were forced into a "work stand down" to address safety, quality and schedule problems. The action followed a discovery that contract employees had removed a parts from the operating reactor rather than the twin one under construction where they were supposed to be working.

"We've had a good safety and quality performance for the last 14 months, and I believe this incentive plan will bring [more] margin," Skaggs said Thursday.

Grissette joined TVA in 2009. He previously had been a vice president for nuclear operations at Florida Power and Light.

Cleary joined TVA in August 2007.

"Tim is an experienced nuclear power generation leader. His breadth of experience ranges from site operations, engineering and license renewal, to general management, organizational effectiveness and new business initiatives," Golden said.