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 A degrees C reaction temperature to lose its structural integrity so as to release the halides. In the present paper, we report WO3 accelerated pyrohydrolytic extraction technique for the separation of F- and Cl- from thoria based fuels along with the feasibility of using MoO3 and V2O5. The mechanism of extraction has been investigated in detail using X-ray diffraction and recovery studies. ThO2 along with its halides undergo high temperature solid state reaction with WO3 forming Th(WO4)(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 A degrees C.