DIFFRACTION STUDY OF ACTINIDES UNDER PRESSURE

Uranium and thorium have sufficiently low radioactive dose rates to al low their study at synchrotrons and neutron facilities. Correspondingl y, numerous compounds of these two actinides have been studied under p ressure by synchrotron x-ray diffraction. The maximum pressures reache d were on the order of 60-80 GPa, and 300 GPa in one case. The situati on is much more difficult for all other actinides. Their high level of radioactivity has up to now prevented their study at synchrotrons, ex cept in a few special cases. In contrast, all actinide metals availabl e in sufficient quantities, and a large number of compounds of highly radioactive actinides, have been studied in high pressure laboratory f acilities. Recent examples of in situ high pressure x-ray diffraction work will be described.