New research reported in Science Magazine finds that plutonium reacts differently than previously assumed when exposed to air and water, and becomes very soluble in water. The fact that plutonium can, over time, transition to a chemical form that will rapidly move into the biosphere calls into question the viability of burial as a disposal method.
Plutonium is present in all nuclear waste that originates from a nuclear reactor. Current U.S. policy for nuclear waste disposition is burial. For "low-level" wastes, this is in shallow trenches near the surface. The plan for highly concentrated radioactive wastes is geologic burial at Yucca Mountain, as exemplified in the current S. 1287 Amendments to the Nuclear Waste Policy Act.
The report in Science Magazine (Vol 287 # 5451,14 January 2000), by chemists Haschke, Allen, & Morales overturns long-held assumptions about what may happen when plutonium is buried. A commentary in the same issue of the magazine, entitled "Towards the End of PuO2's Supremacy?" discusses implications for long-term storage of plutonium dioxide:
"It has … been assumed for more than 50 years that PuO2 is the highest plutonium oxide which can be prepared. This oxide … was believed to be stable over a wide temperature range…. For both civilian and military applications, the stability of PuO2 was a key factor underlying the industrial strategy … The new results … have great consequences for the underground disposal of plutonium wastes. Until now, it was assumed that plutonium would not be very mobile in the underground geological environment because of the insolubility of Pu(IV) compounds. But Haschke et al. demonstrate that water can oxide PuO2 into PuO2+x in which more than 25% of the plutonium ions exist as Pu(VI), an ion that is far more water soluble …"
"This new information demonstrates the folly of current U.S. nuclear waste policy," said Michael Mariotte, executive director of the Nuclear Information and Resource Service (NIRS). "This policy has been marked by incorrect assumptions, inadequate information and politically-based dump siting. It is clear that the leaky, earthquake-prone Yucca Mountain, Nevada site is unsuitable for long-term atomic waste storage. What is becoming increasingly clear is that the scientific community still doesn't know enough about radioactive waste to even offer a solution. "
"Pursuing a half-baked "disposal" strategy for the sole interests of the nuclear power industry—as embodied in the nuclear waste legislation (S. 1287) to be considered on the floor of the Senate next week—puts the cart before the horse and sets the stage for a potential catastrophe for people and the environment," said Mary Olson, radioactive waste specialist in NIRS' Southeast office. It's time for the government to admit we just don't yet have enough information to handle a huge centralized stockpile of high-level atomic waste. Pretending we do would be the greatest folly of all."