A SEARCH FOR SUPERHEAVY ELEMENTS IN METEORITES USING A NEUTRON MULTIPLICITY DETECTOR

A search for superheavy element fission events in meteoritic samples was made using a novel neutron multiplicity detector which was operated underground. No differences could be detected between samples of meteoritic and terrestrial materials. All multiple neutron events could be attributed either to very small amounts of fissile material contaminating the detector materials or to the effects of cosmic rays. An upper limit of 1.3 kg-1 y-1 for the fission rate in meteorites is derived. Assuming the half life to be 10(9) y, this translates to a concentration of < 1.0 x 10(-15) kg kg-1 which is below all previous measurements. Further analysis of the data suggests that Runcorn's lunar core hypothesis remains just barely tenable. It is argued that further studies of this type are likely to be unrewarding.