The LATimes ran a story last year after the death of the inventor of the neutron bomb, Samuel T. Cohen.
Cohen believed that this bomb would lead to safer warfare, but, as one might imagine, others disagreed. Apparently, President Reagan ordered up many hundreds of these bombs, which were supposed to have been dismantled following protests and the fall of the iron curtain. Still,
France, China, Russia and Israel are also thought to have produced neutron weapons, but it is not known if they still have any.
Maybe events in Japan will help shine a light on whether these weapons still exist somewhere.