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

The ²³⁶U(n_th, f) cross section was measured for the first time at the high-flux reactor of the Institut Laue-Langevin 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 g_f = 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.