A Simple Kinetic Model for the Alpha Radiolysis of Water Sorbed on NpO₂

Alpha radiolysis experiments have been performed on NpO₂ that contains sorbed moisture. A high dose rate to the sample was achieved by spiking it with ~7000 ppm ²⁴⁴Cm during preparation. Pressure monitoring of sample containers showed that a low, steady-state pressure plateau is reached. This plateau indicates a situation in which the forward reaction (i.e., radiolysis of water) is equal to the back reaction (i.e., the reformation of H₂O). In this technical note, a simple kinetic model that can be used for predicting steady-state pressures under practical conditions is described.