Decisive action is needed to get on with work to finish the Hanford vitrification plant and start treating radioactive waste for disposal, said Nils Diaz, former chairman of the Nuclear Regulatory Commission.

Diaz sent a letter Tuesday to outgoing Energy Secretary Steven Chu calling for decisions to be made.

"Although the Department of Energy has expended major efforts directed at resolving the myriad of technical and policy issues at Hanford, a lack of consistent decision-making has impeded completion of the waste treatment project, delaying immobilization," he wrote in the letter to Chu.

The plant languishes because prioritizing safety issues has been obscured by a laundry list of technical and management decisions, Diaz said in the letter. That causes multiple changes in design and direction, which are then compounded by funding problems, which then create more changes and delays, he said.

"We could spend another generation arguing about it and its costs, allowing the risk to the people and the nation to escalate further," he wrote.

The design of the plant will never be perfect, but the project is at a point where raising more issues and questions does not have a significant payoff, he said in a telephone interview Wednesday with the Herald.

"It's time to make decisions," he said. "The enemy of good is better."

The real risk to the well-being of the people in Washington is leaving 56 million gallons of radioactive waste in underground tanks, some of them dating to World War II, he said.

The tanks keep degrading, they have no protection against earthquakes and the hydraulic condition of the waste is unknown, he said.

The vitrification plant is legally required to start turning the waste into a stable glass form in 2019, but DOE has said that schedule may not be met and that the estimated cost of $12.3 billion to build and start operating the plant may be too low.

Diaz said he's been following Hanford environmental cleanup since 1974 -- including two years he lived in the Tri-Cities -- during a nuclear career spanning more than 40 years. In 2011 he served as vice chairman of the Independent Safety and Quality Culture Assessment Team commissioned by DOE contractor Bechtel National at the vitrification plant.

"Nowhere has lack of effective decision-making been more apparent than at the long-delayed WTP (Waste Treatment Plant)," he said in the letter.

But there is an opportunity now to get the project on track with Chu's latest efforts to reduce the plant's technical challenges to a practical plan and final design and schedule, he said.

Chu has assigned five scientific teams to evaluate groups of technical issues and finalize the design of the plant.

"The plan should be expeditiously approved and implemented, funded and fully supported to completion, without further delay," Diaz said in the letter. "Your leadership in assuring that continuing progress is made by your successor is critical."

Chu announced his resignation early this month.

Diaz, who was NRC chairman from April 2003 to June 2006, sent copies of his letter to Washington Gov. Jay Inslee; Sens. Patty Murray and Maria Cantwell, both D-Wash.; Rep. Doc Hastings, R-Wash., and other key congressional leaders.

-- Annette Cary: 582-1533; acary@tricityherald.com; Twitter: @HanfordNews