The US Department of Energy (DoE) has not done enough to find uses for the depleted uranium (DU) left over from uranium enrichment and should do more to avoid having to treat the entire inventory as waste, according to the department's own internal watchdog.
The DoE has an inventory of some 700,000 tonnes of uranium hexafluoride tails - the "leftovers" from uranium enrichment - and a program is under way to convert it back into the oxide form, which is more stable and can easily be disposed of as low-level radioactive waste. The depleted uranium oxide could also potentially be re-used, and DoE, through its Office of Environmental Management, had been charged with investigating this.
A new report from the DoE's Office of the Inspector General (IG) has concluded that the DoE has not followed through adequately on various promising potential applications. The report, based on an audit carried out between November 2007 and August 2008, questioned plans to dispose of nearly all the 551,000 tonnes of depleted uranium from the deconversion project as waste at an estimated cost of $428 million.
Over the years, some DU has been used to blend down highly enriched uranium from decommissioned nuclear weapons so it can be used to generate energy in nuclear reactors. Other uses have relied on its very high density, which also makes it even more effective than lead as a radiation shielding material. It is not classed as a dangerous substance radiologically, but has a chemical toxicity similar to lead. DoE research carried out over 13 years found that it could potentially be used in catalysts, semiconductors, nuclear repository applications and radiation shielding products. The IG report criticises that, with the exception of spent nuclear fuel shielding applications, not enough has been done to pursue these avenues.
The report notes that swingeing budget cuts have been a major factor behind the lapse in research, but questions the wisdom of management decisions within DoE to lower the priority of the DU work when funds became limited. According to the IG report, "modest investments sufficient to continue the research for alternative use for depleted uranium oxide have the potential to avoid significant disposal costs." It also criticises a DoE decision only to focus on uses that would be able to consume a significant portion of the inventory, and notes that radiation shielding uses alone would have the potential to absorb the entire inventory.
No commercial interest?
In response, DoE has said that a lack of commercial interest in the use of DU means that further investigations are not currently warranted. Nonetheless, with two plants currently being built to carry out the reconversion at the Paducah, Kentucky and Portsmouth, Ohio sites due to start up in 2010, it concedes that "it may be beneficial to reassess" to that end it will issue an expression of interest by early 2010 to gauge any industry interest in the uses of DU. The reconversion plants are being built by contractor Uranium Disposition Services (UDS).
Separately, a US speciality chemical company is working on using unconverted depleted uranium hexafluoride as a feedstock to produce fluorine for the manufacture of high-value fluoride gases. In November, International Isotopes Inc said that plans to build a commercial plant based on its patented Fluorine Extraction Process (FEP) technology remained on track with work on a pilot plant to begin in 2009.