This report (HPA-RPD-016) describes calculations to estimate performance bias in the three most commonly-used neutron area survey instruments.
Neutron area survey instruments are used to detect neutrons with a wide range of energies and directions. They are designed to have a response that is as independent of neutron energy and angle of incidence as possible, but given the difficulty of the problem it is unsurprising that they are all deficient in terms of both energy and angle dependence of response to some extent.
To estimate the magnitudes of the biases that occur improved energy and angle dependence of response characteristics for the three most commonly used designs in the UK have been calculated using MCNP (Monte Carlo N-Particle). These calculations have been augmented by measurements. The new response data have then been used to calculate the response in workplaces and assess the implications of the deficiencies of the response characteristics.