Monitoring radioactive gaseous emissions from the ISIS Spallation Neutron and Muon Source

The systems for monitoring mildly radioactive air emissions from the ISIS Spallation Neutron and Muon Source are described. The systems use Geiger tubes to measure beta activity (both β– and β+) sampled from stacks discharging air to the atmosphere, and whilst they are relatively simple systems, they have proved themselves very reliable over the thirty-six years since ISIS began operations. Calculations and measurements of sensitivities of these systems in terms of Bq m–3 per count s–1 are presented, and these calculations and measurements are in good agreement with one another.