Crystallographic study and self irradiation damage on plutonium at low temperature

We have studied the variation of the parameters of α plutonium and aluminium stabilised δ alloys at low temperature, in order to verify the existence of an antiferromagnetic transition at low temperature. The effects of α particles on the length of a polycrystal of α plutonium at 4,2 deg. K are also presented at 18 deg. K a plutonium shows no crystallographic change from its structure at room temperature. The thermal expansion coefficients along the 3 axis seem to be positive at this temperature. Therefore a magnetic contribution on thermal expansion coefficients must be small. A dilatation anomaly of δPu has been observed at 100 deg. K, together with an anomaly of the diffraction lines intensity. No sur-structure line has been observed at 20 deg. K. The length of α plutonium Increases with time at a rate of about 5 x 10-6 per hour when held in liquid helium. This effect is attributed to the creation of Frenkel pairs. (author)