Americium dioxide

Synthesis of americium dioxide involves precipitating/water a solution of americium in hydrochloric acid (HCl) solution as described by the Oak Ridge National Laboratory.[3] The demand for americium dioxide stems from the difficulty of storing the element americium as a liquid in the hydrochloric acid solution because the alpha radiation and hydrochloric acid decomposes storage containers over time. To solve the liquid storage problem, Oak Ridge National Laboratory devised a synthesis to turn liquid americium-acid solution into a precipitated form of americium for safer handling and more efficient storage.[3]

Synthesis of americium dioxide as described by the Oak Ridge National Laboratory includes making a solution of americium in hydrochloric acid by adding americium to hydrochloric acid, then neutralizing the acid as using ammonium hydroxide (NH₄OH).[3]

After neutralization using ammonium hydroxide, a saturated oxalic acid solution was added to the now neutralized solution. This causes large americium oxalate crystals to begin to grow; once complete precipitation is achieved, oxalic acid is then added, once again, to attain a slurry. The slurry of americium oxalate and oxalic acid is next agitated before the americium oxalate is filtered out, washed with water, and is partially dried by allowing air to flow through it. Oak Ridge National Laboratory researchers noted that the americium oxalate that was filtered out has a "dusty rose color" appearance.

The americium oxalate is then added to a platinum boat to undergo calcination. The americium oxalate precipitate is dried in a furnace and will begin to decompose at 350 °C. When decomposition begins to occur, the oxalate will turn into the desired black americium dioxide; to ensure no oxalate remains in the newly forming dioxide, the oven temperature is increased and held at 800 °C then slowly allowed to cool to room temperature.

Americium dioxide is the most widely used americium compound in ionising smoke detectors. The dioxide form is insoluble in water, making it relatively safe to handle in production.

In the late 2010s, americium dioxide has been of interest to ESA as power source for radioisotope thermoelectric generators (RTGs) for deep space exploration spacecraft and satellites. A fully automated chemical process to produce americium dioxide was developed by nuclear researchers from the University of Bristol to be implemented on the Sellafield nuclear site in Cumbria, UK. It is based on the same principles as the historic production method developed at Oak Ridge National Laboratory. [4]

Americium-aluminium alloys can be formed by melting americium dioxide with aluminium and an additional fluxing agent.[5] The created alloy can undergo neutron irradiation to produce other transuranic nuclides.[6]