Experimental Determination of the 236U(nth, f) Cross Section

The 236U(nth, f) cross section was measured for the first time at the high-flux reactor of the Institut LaueLangevin in Grenoble, yielding a value of (0.3 ± 1.0) mb. This means that f 1.3 mb, which is about two orders of magnitude lower than previously adopted. This result was obtained by combining a highly enriched 236U sample with a very clean neutron beam and assuming that the Westcott factor gf = 1 for 236U (n, f) with cold neutrons. The new value is compatible with the latest fission resonance data and with the subthreshold character of the thermal neutron induced fission of 236U.