The sensitivity of the UKAEA criticality dosimeter to slow neutrons

Improvements have been made in the determination of the thermal and epithermal neutron sensitivity of the thick gold foil combination of the UKAEA personnel criticality dosimeter which is used to measure the neutron leakage spectra from critical assemblies and reactors. Calculations are presented to enable incident and reflected components of the thermal fluence and the epithermal fluence per unit lethargy interval to be derived from β-ray measurements from each gold foil surface. Gold foils and criticality dosimeters have been exposed to reference neutron fluence rates to verify the calibration, and the uncertainties of the method are described both for these reference exposures and for exposures in typical criticality conditions. (author)