An instant working level meter for uranium mines

The Instant Working Level Meter (IWLM) evaluates the Working Level (WL) in a uranium mine atomsphere within 4 min. Two minutes are needed to measure the background mostly due to ambient gamma radiation and 2 min are spent to measure background plus WL. It has two a channels (RaA and RaC') and one beta + gamma channel (RaB and RaC). The counts in the different channels are multiplied electronically by calculated weighting coefficients and combined to give the WL. No assumptions about Rn daughter equilibrium are made. Only constancy of the radon daughter concentrations in the atmosphere during the time of sampling is assumed. So far a total of 5 instruments of the type described in this report have been built and used in uranium mines.