Effect of accelerators on thoria based nuclear fuels for rapid and quantitative pyrohydrolytic extraction of F− and Cl− and their simultaneous determination by ion chromatography

Pyrohydrolysis is a fast, reliable and convenient method for the decomposition of solid refractory samples. Thoria based mixed oxide nuclear fuels requires more than 1,200 °C reaction temperature to lose its structural integrity so as to release the halides. In the present paper, we report WO 3 accelerated pyrohydrolytic extraction technique for the separation of F − and Cl − from thoria based fuels along with the feasibility of using MoO 3 and V 2 O 5 . The mechanism of extraction has been investigated in detail using X-ray diffraction and recovery studies. ThO 2 along with its halides undergo high temperature solid state reaction with WO 3 forming Th(WO 4 ) 2 and releasing the halides for their subsequent hydrolysis. The quantification was carried out by ion chromatography with suppressed ion conductivity detection. The average recoveries of the spiked samples for F − and Cl − were 93–99%. The method was successfully applied for simultaneous determination of F − and Cl − in thorium based nuclear fuel samples at 950 °C.