Plutonium Transport in the Environment

The recent estimated global stockpile of separated plutonium (Pu) worldwide is about 500 t, with equal contributions from nuclear weapons and civilian nuclear energy. Independent of the United States’ future nuclear energy policy, the current large and increasing stockpile of Pu needs to be safely isolated from the biosphere and stored for thousands of years. Recent laboratory and field studies have demonstrated the ability of colloids (1–1000 nm particles) to facilitate the migration of strongly sorbing contaminants such as Pu. In understanding the dominant processes that may facilitate the transport of Pu, the initial source chemistry and groundwater chemistry are important factors, as no one process can explain all the different field observations of Pu transport. Very little is known about the molecular-scale geochemical and biochemical mechanisms controlling Pu transport, leaving our conceptual model incomplete. Equally uncertain are the conditions that inhibit the cycling and mobility of Pu in the s...