Fukushima’s Radioactive Waste Elements Three Years Later: Plutonium and Cesium

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Much of North East Japan Suffered catastrophic losses, including the Sendai region. Image from Nuclear Regulator Commission Report: Recommendations for Enhancing Reactor Safety in the 21st Century

Much of northeast Japan suffered catastrophic losses, including the Sendai region. Image from Nuclear Regulator Commission Report: Recommendations for Enhancing Reactor Safety in the 21st Century.

The safe disposal of chemical or radioactive waste is important – everyone agrees on that – but no one wants it in his or her backyard. Unfortunately, the amount of radioactive, harmful waste from the Great Japan Earthquake of 2011 is staggering.

While most radioactive elements have degraded, the radioactive elements that have not decayed to a measurable degree are Cesium and Plutonium, both of which can be deadly.

The Plutonium seems to have dropped from public consciousness since the early days of the 2011 earthquake. Professionals are disposing of Cesium, on the other hand, in ways that may eventually be applied elsewhere in the world.

Aspects of Plutonium at Fukushima

Plutonium, an artificial element, results from the synthesis of Uranium 238 with a neutron- it is also found as a by-product of nuclear explosions. The complete decay (or degradation) of  Plutonium 239 takes thousands of years. Estimates put the total amount of released plutonium approximately one-half of one gram.

Certain isotopes of radioactive plutonium are known as some of the deadliest poisons on the face of the earth. A mere microgram (a speck of darkness on a pinhead) of Plutonium-239, if inhaled, can cause death, and if ingested, radioactive Plutonium can be harmful, causing leukemia and other bone cancers.

In the days following the 2011 earthquake and nuclear plant explosions, seawater meant to cool the nuclear power plants instead carried radioactive elements back to the Pacific ocean. Radioactive Plutonium was one of the elements streamed back to sea. Environmental groups protested loudly.

Environmental testing of shoreline around the nuclear plant (as well fish, especially Tuna) showed negligible amounts of Plutonium in the seawater. The Plutonium, from what little is reported, sank into the sediments off the Japanese coast. Plutonium is one of the densest elements known to humankind; the plutonium that escaped after the Fukushima disaster seems to have disappeared.

Radioactive Cesium at Fukushima

Radioactive fallout of Cesium left Japan desperate for an answer to a logistic nightmare— the disposal of more than 15 years of accumulated waste generated on a single day. (Cesium, known to damage soft tissue and bone, causes bone cancer.) If left unaltered, the landscape would contribute to thousands of deaths.

The Cesium fallout resulted from the explosions that rocked four of the six nuclear reactors at the Daiichi Power Plant. Experts estimate that the total amount of waste that needs disposal or incineration is 20 million tons. The waste consists of two kinds: rural- and urban-type refuse. The refuse is further characterized by the amount of radioactive Cesium contained.

The rural waste consists primarily of radioactive soil and vegetation. Incineration of vegetation and soil generates radioactive ash, and the radioactive cesium isolated. The urban waste, once separated into sewage, garbage and ‘durable-type materials’ (concrete and steel), requires further processing. First, they burn the sewage and garbage, and then compact the durable material.

Secondly, the processed material undergoes washing to isolate radioactive Cesium. Although both compaction and incineration reduce the total volume, the mounting volume of fly ash posed a nightmarish scenario. So, the question became, how to contain the radioactive Cesium from bulk amount of ash. The answers show considerable inventiveness.

Cesium (Cs) is trapped by Prussian blue dye by removing Potassium (K) from the crystal lattice. Schematic with Chem Draw 14. Image by John A. Jaksich, all rights reserved

In a nutshell, the answer came down to understanding how the radioactive Cesium could be washed and then trapped in small batches. The smaller volume of Cesium obtained by washing in a hot acidic water bath (also known as digestion) allowed its isolation.

An organic dye (an organic molecule) known as Prussian blue selectively extracts Cesium over other elements. A solid matrix then traps the extracted Cesium in an appropriate landfill or storage.

Important research has come to the forefront as clean-up of Cesium proceeds at Sendai. Processes to remove radioactive Cesium come from findings reported from nuclear chemists in India. The process involves an oganic-cobalt molecule. The reported research, although novel and  efficient, is only in the research phase.

The Ugly Realities and the Hope in the Aftermath

Although a ‘trace’ amount of Plutonium contaminates the environment, questions remain: The degradation products may be traced; if not ingested, it may be isolated and permanently removed. The other issue is the Cesium which contaminated much of Northeast Japan.

Clean-up still goes on three-and-a-half years later. The economic burden of clean-up, estimated as $500 billion US dollars, surely will increase in cost as health issues come to the forefront. If we may glean any hope, it is that research dollars (and specific results) await in cases that may make future radioactive nightmares less likely.

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