Remediation of borosilicate Raschig rings

The legacy of the nuclear arms race has left numerous environmental remediation challenges. For example, a common practice from the 1950s to the 1970s for nuclear criticality control of fissile solutions in storage tanks was the use of borosilicate Raschig rings However, this practice subsided with the uncertainty in the long-term consistency of the boron concentration in the Raschig rings The result was numerous abandoned tanks that are relatively filled with contaminated borosilicate Raschig rings

The focus of this study was on a radioactive waste stream from an uranium/thorium separation process that was conducted in the 1970s. The primary radioactive contaminants of this waste stream were thorium-228/229 and the associated decay products. Motivation for remediation of the Raschig rings is based on the associated costs of disposal of large volumes of radioactively contaminated Raschig rings. Additional inspiration behind this particular waste stream is the interest in thorium-229 as a bio-medical generator for alpha radioimmunotherapy

In this study, successful remediation of radioactively contaminated borosilicate Raschig rings was achieved using a nitric acid solvent/ultrasonic agitation method followed by ion exchange separation and a combination surfactant/ultrasonic volume reduction method. Both methods resulted in a successful remediation with greater than 99% removal of the radioactive contaminants Furthermore, successful recovery of the thorium-229 was achieved through a combination of batch anion and cation ion exchange processes Consequently, this success has allowed clinical trials to begin on a new treatment for myelogenous leukemia using the decay products fi-om thorium-229