Estimating mixed field effects: an application supporting the lack of a non-linear component for chromosome aberration induction by neutrons.

The action of neutron fields on biological structures was investigated on the basis of chromosome aberration induction in human cells. Available experimental data on aberration induction by neutrons and their interaction products were reviewed. Present criteria adopted in neutron radiation protection were discussed. The linear coefficient alpha and the quadratic coefficient beta describing dose-response curves for dicentric chromosomes induced by neutrons of different energies were calculated via integration of experimental data on dicentric induction by photons and charged particles into the Monte Carlo transport code FLUKA. The predicted values of the linear coefficients for neutron beams of different energies showed good agreement with the corresponding experimental values, whereas the data themselves indicated that the neutron quadratic coefficient cannot be obtained by 'averaging' the beta values of recoil ions and other nuclear reaction products. This supports the hypothesis that neutron induced aberrations increase substantially linearly with dose, a question that has been object of debate for a long time and is still open.