Evaluation of fission neutron multiplicity data for Th-232

This paper describes the evaluation of the energy dependent experimental data for the average number of prompt neutrons, ν-barp, for the neutron induced fission of Th-232 in the energy range from 1 - 20 MeV. The evaluation takes in account not only the actual numerical data of ν-barp (En) but also certain physical concepts based on the energy balance in nuclear fission. the energy dependence of ν-barp is represented by two SPLINE fitted curves because of the anomalous behaviour near threshold and multiple chance fission which introduces a non-linear dependence on En. Data are renormalised wherever necessary to the latest recommended value of (3.757) for ν-barp for spontaneous fission of Cf-252. The present evaluation is compared with the existing ones. Recommended values of ν-barp (En) are given over the energy range 1 - 20 MeV. (author)