Conference Agenda

Atmospheric fallout from reactor accidents and atmospheric nuclear weapons tests can arise in refractory and volatile forms affording forensic analysis via the ratios of plutonium isotope abundance. Here, accelerator mass spectrometry measurements of ²⁴⁴Pu/²³⁹Pu and ²⁴⁰Pu/²³⁹Pu are compared from both refractory and volatile components in soil samples from the United Kingdom. ²⁴⁴Pu/²³⁹Pu measurements of both the refractory and volatile components and the volatile proportion of ²⁴⁰Pu/²³⁹Pu are observed to be consistent with their corresponding global averages. By contrast, refractory ²⁴⁰Pu/²³⁹Pu is high relative to both the global average and that expected for local sources but is consistent with fallout from Chernobyl. However, being in the refractory phase suggests formation at temperatures > 3000°C which, whilst inconsistent with prior analyses based on the initiating event being chemical in origin and the subsequent fire, is consistent with both nuclear reactivity and ²⁴⁰Pu production being enhanced at such temperatures as per the associated neutron cross-section data, and prior reports of a blue flash above the plant, seismic records and prompt isotopic xenon signatures recorded some 1000 km distant. A further calibration with a ²⁴⁰Pu standard is recommended to substantiate these observations.