Environmental and personnel monitoring for uranium by delayed neutron counting

At the Imperial College Reactor Centre we have developed a fully automated, large sample, high sensitivity delayed neutron counting system for routine analysis of environmental samples and personnel monitoring. Two-hundred fifty samples with a maximum volume of 30 ml can be analysed each working day. The detection limits (3 sigma) for uranium of natural isotopic abundance in our routine samples are typically 1 microgram/kg (0.05 Bq/kg) for dry samples and 1 microgram/l (0.05 Bq/l) for aqueous samples. Daily analysis of BNFL uranium standards, 'in house' uranium standards and weekly analysis of IAEA Soil-7 reference material are used to ensure constant system sensitivity and accuracy.