In-Line Determination of Fissile Material in High-Activity Solutions

A determination of fissile material concentration in high-level radioactive solutions can be accomplished by measuring the source multiplication of an external neutron source. Computer calculations and laboratory experiments were used to demonstrate the applicability of the method to fissile material solutions containing unknown quantities of homogeneous neutron poison materials. A relation between the fissile material concentration C_fiss and the quantities thermal and epithermal leakage neutron fluxes measured with ²³⁵U fission chambers is derived. The accuracy obtained using a ²⁵²Cf neutron source of source strength 5 × 10⁸ n/s, a measuring time interval of 20 s, and assuming C_fiss to be at least twice the minimum detectable concentration is better than 30%. This is adequate for application of the method for process control of pulsed columns in reprocessing plants.