Optimization of neutron activation analyses of 129I in low-level radioactive waste samples

Abstract

Determination of 129I in low-level radioactive waste (LLW) samples from reactors can be a tedious and time consuming procedure often leading to results with large margins of error. This study used an efficient (approx. 2-3 h per sample) and reliable procedure, which could be used for LLW waste samples in various physical forms (solid, liquid, resin). Samples were processed without pretreatment by distillation of the LLW samples, followed by separation using chemical extraction. The extracted 129I solution was then irradiated for 5 min in a 2 MW research reactor (neutron flux of about 1013 n/cm2-s), and the activation product, 130I, was analyzed with a high-purity intrinsic germanium detector. A tracer of 127I was also activated to 128I to determine radiochemical yield, which was 29 +/- 7%. The lower limit of detection of the procedure was about 30 pCi/g for 4 g samples, 29% recovery, and a 1000 s counting time.