An estimation of fast neutron flux by 35Cl(n, α)32P reaction

Phosphorus-32 produced by the 35Cl(n, α)32P reaction in table salt and KCl was measured to estimate the fast neutron flux from the JCO criticality accident. A directional dependence of the fast neutron flux was suggested by the anomalously low activities of samples collected from the south and south-west directions. Although the present data are preliminary, the total number of fast neutrons from the precipitation vessel is estimated to have been approximately 5×1016 using both the 32P activity at 70 m and the observed attenuation constant (0.006 m −1).