Luminescence analysis of underground waters of the Lake Karachai contamination area for the neptunium content and forms of occurrence

A luminescence procedure using crystal phosphors was developed for Np determination in environmental objects. The procedure allows the sensitivity of the Np determination to be increased by an order of magnitude relative to traditional α-ray spectrometric analysis. A specialized photometer developed for this purpose is described. The attained Np detection limit in natural waters is 0.1–0.8 Bq l−1. With membrane preconcentration, the detection limit can be decreased to 3 × 10−4 Bq l−1. The procedure was successfully tested in monitoring of groundwaters of the Lake Karachai contamination area.