WASHINGTON -- A treatment plant that the Energy Department is counting on to stabilize the radioactive waste at the nation's largest environmental cleanup project, at the Hanford Nuclear Reservation in Washington State, has design problems that could lead to chemical explosions, inadvertent nuclear reactions and mechanical breakdowns, a federal advisory panel warned on Tuesday.
The panel, the Defense Nuclear Facilities Safety Board, said the waste was also not safe where it was now, in leaking tanks that have long put dangerous pollutants into the soil a few miles from the Columbia River. In addition to the leaks, the board said, radioactive sludge and liquids in the tanks produce hydrogen that could burn and further disperse the waste.
The current problems are only the latest in the treatment plant's long and expensive history. The Energy Department signed an agreement with the Environmental Protection Agency and Washington State to start construction of the plant in 1989, paid for two sets of designs for such a plant in the 1990s and then did not build either one.
Construction on the project finally began in October 2001. Two years ago, the plant was expected to cost $12.2 billion, but the schedule, and the price, have grown since then. The Energy Department does not have a current estimate for the plant's cost and completion date.
For now, the agency has stopped work on some sections of the plant while it tries to figure out how to solve the problems.
The board described the difficulties in a letter to Senator Ron Wyden, the Oregon Democrat who is the chairman of the Senate Energy Committee. Mr. Wyden said in an interview on Tuesday that the board's experts had raised "a serious question as to whether this plant is going to work at all."
An Energy Department spokeswoman, Aoife McCarthy, said in a statement that the plant was "a highly complex facility with first-of-a-kind applications of many advanced technologies," and that the department was working with its contractor, Bechtel National, "on resolving the remaining technical issues."
But changes to address some issues have raised other potential problems. Engineers realized that they needed to mix the radioactive waste more thoroughly to break up concentrations of plutonium to ensure that there would be no chain reaction. But more thorough mixing raised the possibility of more erosion of the pipes.
The waste is a byproduct from nine nuclear reactors at the vast site that were used to produce plutonium, including for the bomb that destroyed Nagasaki in World War II. The government has known for decades that the oldest tanks, made of a single layer of carbon steel, were leaking.
At the least, the board's report raises the question of whether reports of past progress at the site were illusory.
In 1991, Mr. Wyden, then a member of the House, was the author of a law requiring the Energy Department to pay closer attention to the hydrogen in the tanks. In 2001, the department gave him a plaque after 24 tanks were taken off the "watch list" because the hydrogen problem had supposedly been solved. But the board said in its report that "many of the double-shell tanks currently have enough flammable gas retained in the waste" that, if it is released in the tank's head space, it could create "a flammable atmosphere."
"Here we are again," said Mr. Wyden, who added that he planned to raise the issue next week when his committee holds a confirmation hearing for President Obama's nominee to be energy secretary, Ernest J. Moniz.
The treatment plant now under construction is to mix the radioactive waste with molten glass, which would turn it into a solid that could not spill and would be very difficult to break down, even over millenniums. The waste includes materials that give off hydrogen when they are bombarded with high levels of radiation.
The board noted that the Energy Department had decided that hydrogen explosions would be acceptable in some piping systems, but said it had not demonstrated that such explosions would not break open pipes or tanks.
Mr. Wyden expressed exasperation in the interview that the problems had surfaced when construction of the plant was nearly complete. "These are the questions that should have been resolved at the front end," he said.
The project also has issues, apparently still not resolved, about whether managers have sought to intimidate professional staff members who raised safety questions. In 2010, the board received a letter from a former engineering manager, Walter Tamosaitis, in which he alleged that he "was removed from the project because he identified technical issues that could affect safety." The board investigated and agreed that the site had "a flawed safety culture" that was "inhibiting the identification and resolution of technical and safety issues."
The board said in its letter to Mr. Wyden that since then the Energy Department had taken significant steps, but that "progress in changing any organizational culture is historically slow."
This article originally appeared in The New York Times.