ISOTHERMAL DECOMPOSITION OF GAMMA-IRRADIATED LANTHANUM OXALATE

Isothermal decomposition of gamma-irradiated (0.1-1.0 MGy) lanthanum o xalate has been carried out at different temperatures between 623-663 K by gas evolution method. The alpha-t plots for unirradiated as well as irradiated crystals indicate that decomposition occurs through smal l initial gas evolution (alpha(i) similar to 0.4%) followed by short a cceleratory and long decay stages. The data are well fitted to Prout-T ompkins relationship and Avrami Erofeev mechanism suggesting that nucl eation occurs in a chain branching manner with two dimensional growth of nuclei. Irradiation facilitates the rate of reaction, the effect be ing higher at higher doses and decreases the energy of activation whic h may arise due to increased number of point defects and additional nu cleation centres generated in the crystal lattice.