Flammable gases in Hanford's underground tanks holding radioactive waste continue to pose a possible risk of an explosion, according to a letter from the Defense Nuclear Facilities Safety Board.
Sen. Ron Wyden, D-Oregon, asked the defense board for a rundown of current issues at Hanford as he prepares for a confirmation hearing Tuesday for Ernest Moniz, the energy secretary nominee. Wyden is the new chairman of the Senate Energy and Natural Resources Committee.
"The next secretary of energy -- Dr. Moniz -- needs to understand that a major part of his job is going to be to get the Hanford cleanup back on track, and I plan to stress that at his confirmation hearing next week," Wyden said in a statement.
Of particular concern to Wyden are the safety of Hanford's underground tanks, the technical issues plaguing the vitrification plant and the safety culture at the nuclear reservation.
Twenty years ago, the senator passed legislation creating the "Wyden watch list" of Hanford tanks that posed a risk of hydrogen explosions, and a plan to address them. Safety issues, which covered 56 tanks then, were resolved in 2001, and Wyden joined Hanford workers to celebrate.
"Now in this letter, the board says that the high-level waste tanks continue to present a risk of hydrogen explosions," Wyden said.
In September, as reported in the Herald, the defense board issued a formal recommendation to the Department of Energy, saying DOE needed to do more to guard against a buildup of flammable gases in its 28 double-shell tanks.
"A significant flammable gas accident would have considerable radiological consequences, endanger personnel, contaminate portions of the tank farms and seriously disrupt the waste cleanup mission," the September report said.
DOE has a ventilation system installed in its double-shell tanks that blows air into the head space of each tank and then sucks it out with gases generated by the sludge-like radioactive waste.
In 2010, it began making improvements in the system, acknowledging its importance to safety.
When the defense board called for faster action in 2012, Energy Secretary Steven Chu responded with a plan for improvement. It includes installing instruments for real-time monitoring of the ventilation exhaust flow from each of Hanford's 28 double-shell tanks and making the monitoring data available remotely.
In February, DOE instituted an improved testing and monitoring system to allow for direct monitoring of the tank ventilation system, DOE said in a statement Tuesday.
"DOE is absolutely committed to ensuring the safety of Hanford's underground tanks," it said.
The defense board letter to Wyden also reiterated the key technical challenges faced at the vitrification plant, which is being built at a cost of $12.2 billion to treat tank waste for disposal in a sturdy glass form starting in 2019.
Issues at the plant's Pretreatment Facility include keeping waste well mixed to prevent an uncontrolled nuclear reaction, preventing the buildup of flammable hydrogen in pipes, and reducing projected erosion and corrosion of piping and tanks within the plant. The resolution of the issues is complicated by the partial construction of the facility and a design that plans for no workers to enter highly radioactive areas for maintenance during the 40 years the plant will operate, the defense board letter said.
DOE is considering strategies to allow waste to bypass the Pretreatment Facility. But directly feeding the waste into the facilities that will treat it "will be a challenging undertaking that will involve resolving some of the same technical and safety issues associated with the design of the Pretreatment Facility," according to the defense board.
The board identified a substantial number of unresolved problems at the vitrification plant, Wyden said, indicating that the plant's schedule will be delayed further and the cost will rise more.
"There is a real question as to whether the plant, as currently designed, will work at all," he said.
The defense board was somewhat more positive on improvements in the safety culture at Hanford.
"The board believes that Secretary Chu has vigorously tackled this issue, but progress in changing any organizational culture is historically slow," the board's letter said.
Fundamental differences between officials designing the vitrification plant and those responsible for documenting that it will operate safely still must be resolved, the letter said. DOE has agreed to a review of the vitrification plant's safety culture within the next few months to evaluate the effectiveness of the changes made to improve safety culture, the letter said.