Method development for the recovery of plutonium from refractory alumina crucible using NaOH fusion technique

Abstract

The public acceptance of clean energy production from nuclear reactors demands the development of innovative methods to minimize and recycle the actinide waste with little or no impact to the environment. Nuclear fuel before it could be qualified has to undergo stringent quality control (QC) measures at various stages of fabrication. Analysis of carbon content in nuclear fuel is one such QC checks which produces refractory alumina crucibles containing plutonium embedded in molten solidified Cu. Development of a method for recovery of plutonium (Pu) from these refractory materials, accumulated over the years, is crucial prior to their disposal. The conventional process of acid leaching, using HF + HNO3 mixture, is time consuming and generates large volume of radioactive acid waste. To eliminate these drawbacks, a simple pre-treatment method of fusion with NaOH was adopted prior to acid leaching for recovery of Pu from these alumina crucibles. A number of small scale experiments were conducted by varying process parameters and fusion temperature of 600 °C and 16 M HNO3 as leachant were found to be optimum for maximum recovery of Pu. The final recovery of 96.5% was arrived by biamperometric analysis of Pu in acid leachate. The efficiency of recovery of Pu was reconfirmed by its gamma spectrometric assay in the residual precipitate. Experiments were also carried out by treating alumina crucible with NaOH in a single step and heating uninterruptedly to check the feasibility of scaling-up the process. The fused product and precipitates obtained during leaching were characterised using X-ray diffraction analysis (XRD).