J. Fuger

Self-irradiation effects in americium oxides

Abstract Using X-ray powder diffraction techniques we have followed as a function of time the effects of self-irradiation damage at room temperature in the americium-241 oxides. The radiation induced lattice expansion of the dioxide is slightly different wether the samples are kept in a vacuum or under an oxygen atmosphere: differential oxygen losses under the effect of self-irradiation would satisfactorily account for this effect. The influence of the irradiation of the sesquioxide is shown to be markedly dependent upon the crystalline form under investigation. Evidence is presented for the spontaneous transformation over a period of several years of the room-temperature cubic form of the sesquioxide into the hexagonal high-temperature form.

Self-radiation effects on the lattice parameter of 244CmO2

The effects of the self-irradiation damage induced in 244CmO2 have been studied by following the evolution of the lattice parameter of this compound as a function of time. Samples kept at room temperature undergo an expansion of the lattice parameter, limited to a saturation value, which is reached in a few days. The expansion of the samples kept in a vacuum of 10−6 torr appears slightly different from that of samples kept under 34 atmosphere of oxygen pressure. At liquid nitrogen temperature, a further expansion can be observed, only with the samples sealed in oxygen. This low temperature expansion anneals out at room temperature, in two days, whereas the complete annealing of the initial room temperature expansion needs a treatment of ten days at 360°C. Freshly prepared samples, kept in 34 atmosphere of oxygen, for one month, at 360°C, do not show any lattice expansion.

Self-radiation effects on the lattice parameter of 238PuO2

A study was made, as a function of time, of the self-radiationinduced expansion of the lattice parameter of freshly prepared onential equation. The observations were compared with previous results reported for PuO/sub 2/ and with recent observations on the lattice expansion of /sup 244/CmO/sub 2/. The isochronal annealing of the damaged lattice revealed a two-stage process. Isothermal treatments showed a rapid contraction during the first few minutes of annealing, the equilibrium of recovery being reached within one hour. (auth)

Some recent observations on curium sesquioxide

Abstract We have studied as a function of temperature the rate of the radiation induced transformation of the cubic form of curium sesquioxide into the hexagonal form. The rate of destruction of the cubic lattice, as shown by X ray diffraction, is much greater at low temperature than at room temperature, while at 300°C, it is essentially negligible. Whereas the monoclinic form of Cm2O3 has been obtained on heating the cubic phase under vacuum, or by reduction of the dioxide, both reactions at temperatures higher than 850°C, we have shown that it can be produced by heating the hexagonal form to 500°C. We have observed an expansion in the lattice parameter of the cubic sesquioxide samples during the very first hours following their preparation. This expansion rapidly reaches a saturation value. We also noted a contraction of the hexagonal lattice during the time of its spontaneous formation from the cubic lattice.

On the cyclooctatetraenyl compounds of actinide elements part II. Bis-(cyclooctatetraenyl) protactinium(IV)

Abstract The preparation of a new organometallic compound, (C 8 H 8 ) 2 Pa, is reported. It has been characterized by IR spectrometry and by X-ray powder diffraction analysis.

A new determination of the heat of solution of americum metal and the heat of formation of various americium ions and compounds

Abstract The heats of solution of americium metal (d.h.c.p. structure) in aqueous hydrochloric acid solutions have been measured at 298.15 ± 0.05 K. The values obtained are −616.1 ± 0.8 kJ mol −1 in 1M HCl, −615.4 ± 0.8 kJ mol −1 in 1.5M HCl and −613.1 ± 1.4 kJ mol −1 in 6M HCl. From these data, the standard enthalpy of formation of Am 3+ (aq) is obtained as −616.7 ± 1.2 kJ mol −1 and the standard potential of the Am(O)/Am(III) couple is calculated to be 2.06 ± 0.01 V. New values for the heat of formation of various americium ions and compounds are presented.

On the indenyl compounds of actinide elements Part I: Triindenylthorium bromide and triindenyluranium bromide

Abstract The synthesis of new organometallic compounds of actinides, (C 9 H 7 ) 3 ThBr and (C 9 H 7 ) 3 UBr, is reported. Some properties of the triindenylactinide bromide compounds are described and compared with those of triindenylactinide chloride compounds. Mass, infrared, Raman and electronic spectra and partial X-ray powder diagrams are given. (C 9 H 7 ) 3 UBr, (C 9 H 7 ) 3 ThBr and (C 9 H 7 ) 3 ThCl are not isomorphous. Evidence is given for the presence of metal to indenyl ligands π bonds.

On the cyclooctateraenyl complexes of actinide elements Part I : Thorium

Abstract The infrared, Raman, visible and X ray diffraction spectra of (C 8 H 8 ) 2 Th are reported. The measurements are consistent with the idea of a sandwich compound with two organic rings of aromatic character.

A new determination of the enthalpy of solution of curium metal and the enthalpies of formation of Cm3+(aq) and CmCl3(s)

Abstract The enthalpy of solution of curium metal (dhcp structure) in 1M HCl has been measured at 298.15 ± 0.1 K, giving a value of −614.5 ± 4.5 kJ mol −1 . From this value, the standard enthalpy of formation of Cm 3+ (aq) is deduced as −615 ± 5 kJ mol −1 and, using reasonable entropy estimates, the standard potential of the Cm(O)/Cm(III) couple is calculated to be 2.07 ± 0.03 V. Calculation also yields a value of −971 ± 6 kJ mol −1 for the standard enthalpy of formation of CmCl 3 (s) at 298 K.

The enthalpy of solution of body-centred tetragonal protactinium metal

Abstract The enthalpy of solution at 298.15 ± 0.05 K of body-centred tetragonal protactinium metal in oxygen-free 12 M HCl − 0.05 M HF, to yield quadrivalent protactinium, has been measured as − 668 ± 14 kJ mol −1 . Dissolution of the metal in 12 M HCl − 0.05 M HF containing oxygen to yield quinquevalent protactinium resulted in an enthalpy effect of − 822 ± 14 kJ mol −1 , leading to − 677 ± 14 kJ mol −1 for the enthalpy of formation of quinquevalent protactinium in that medium.