A production line at India’s Bhabha Atomic Research Centre (BARC) in Trombay is producing medical products based on caesium-137 instead of the usual cobalt-60, with a range of benefits. A rare but usually fatal complication from blood transfusion, Transfusion-Associated Graft Versus Host Disease, is a major risk for fetuses and very premature newborns, as well as patients with suppressed immune systems. To protect against this, doctors routinely irradiate donated blood either with x-rays or gamma rays sourced from cobalt-60.
However, cobalt-60 has a short half-life of 5.3 years which means technicians have to regularly make, transport and install new sources. Caesium-137 offers a longer-lasting alternative with a half-life of 30.2 years, but usually comes as powdered caesium-chloride presenting the potential hazard of dispersal if not properly handled and managed. Researchers at BARC have now created a solid form of caesium-137 with the benefits of long life, reduced handling and no risk of dispersal. They did this by developing an ion exchange and solvent extraction process for caesium-137 present in the stream of reprocessed used fuel from India's nuclear power plants, with the extra benefit of reducing the heat generation and radio-toxicity of the waste and thereby making its long-term storage easier. The caesium-137 is mixed with molten glass (vitrification) and poured directly into metal 'pencils' only 23 mm wide and 204 mm in length before the lid is seal-welded.
A plant-scale production facility has been installed at the Waste Immobilisation Plant at BARC's Trombay site. Its first batch of ten pencils was delivered in June 2015. Although the pencils were developed for blood irradiation, they are expected to replace cobalt-60 for applications such as food irradiation, brachytherapy and sterilization of medical equipment.
