Determination of uranium fission rate in an arbitrary neutron field using fission track detectors

In accelerator driven systems, particularly near the spallation target, the neutron spectrum covers a very wide range of energies and has a complex angular distribution. It is possible to determine the fission rate of fissionable nuclei in such neutron fields using fission track technique. We use the mean density of fission tracks in the two track detectors in contact with two faces of a fission foil (radiator). A calibration factor, w, relating the number of fission events to the track density is needed and was determined in a very well-known neutron field. It was used to estimate the fission rate in a uranium-lead assembly when the lead target was irradiated with protons of energy 1 GeV. Experimental results are compared with Monte Carlo predictions using MCNPX code.