The 238U(n,f) Cross Section and its Ratio to the 27Al(n,α)24Na and 56Fe(n,p)56Mn Cross Section in the 14 MeV Region

The response of a 238U fission chamber in an 3H(d,n)4He neutron field was measured against the activation of iron and aluminium foils and the neutron fluence as determined from measurement of the associated alpha particle fluence. Using a value for the mass of the 238U deposit obtained from independent measurements, the 238U(n,f) cross section was derived and also the ratio of this to the cross section for the 27Al(n,α)24Na and 56Fe(n,p)56Mn reactions was examined. The results were consistent, but indicated a discrepancy of 2 to 3% in the present ENDF/B-VI evaluation of the 238U(n,f) cross section in the 14 MeV range (included in the International Reactor Dosimetry File).