Some time ago there was a query about neutron emission from plutonium compounds. Here is some data. I believe it's correct, but I'm not certain Material neutrons/gram/second Pu-238 2500 Pu-239 0.022 Pu-240 1022 Pu(238)O2 1.4 E4 Pu(239)O2 45 Pu(240)O2 170