A HIGH SENSITIVITY NUCLEAR METHOD FOR REAL-TIME DETECTION OF ELEMENTS AND COMPOUNDS IN DRINKING WATER AND SOIL

摘要

Experiments using a neutron probe in lakes, wells, rivers and water collectors show that the instrument is capable of analyzing soil and water for contaminants in the ppm-range. A two-channel-neutron-neutron-probe is used; the neutrons are produced by a deuterium/tritium-source. The distribution of thermal neutrons is mainly influenced by the composition of the medium and therefore a direct recognition of the components disturbing the neutrons is possible. Measurements may be performed in time-dependent (monitoring) or depth/length-dependent (logs or profiles) mode. The monitoring may be used for permanent control of critical spots in water reservoirs and on soil (bomb detection, explosive indication). The logs and profiles may be run for depth-related information or area studies. The field studies have shown a high sensitivity. Concentration values may be obtained from the shape of the decay curve or by pulse distribution in the measuring windows. Comparisons with lab analysis have shown regression coefficients over 0.9 for different elements like Fe, As, Cl, Cd, P etc., but also for chemical compounds like BTEX or trichlorbezen. It was established experimentally, that a 25 kg bomb may be detected on a distance of 4.5 m. Thus, the pulse neutron technique may be applied for risk studies and planning measures for risk assessment in real time under in-situ-conditions.