Neutron dosimetry in the particle accelerator environment

Radiological safety aspects in general and neutron dosimetry in particular, around medium and high-energy particle accelerators pose some unique challenges to the practitioners of radiation protection. This is mainly because the source of radiations are directional, dynamic, pulsed and a mixture of different types. In conventional dosimetry, measurements are done in the units of the quantities in which the radiological protection limits are expressed. In the accelerator environment, measurement of energy and angular distribution of radiations is preferred instead. Research activities being carried out (particularly in India) in the field of neutron dosimetry are discussed. Measurements of neutron ambient dose equivalent directly using conventional rem-meters as well as neutron energy distributions using the time-of-flight technique employing proton recoil scintillators have been done at different directions with respect to light and heavy ion projectiles incident on various thick elemental targets. The observations and conclusions are summarized. Finally, a discussion on the concept of dose and radiological protection and operational quantities is done along with the recommendation of using Evidence theory instead of Bayesian probability in assessing radiological risk.