Martin J. Steindler

The absorption spectrum of neptunium hexafluoride

Abstract Recent interest in the properties of neptunium hexafluoride included the development of non-destructive methods for the analysis of this volatile, reactive substance. While the infrared spectrum of neptunium hexafluoride has been reported [1], only the work of G oodman [2] and E isenstein and P ryce [3] give data on the absorption spectrum in the visible and near infrared regions. This note records the spectrum of gaseous neptunium hexafluoride in the region of 2000 to 20,000 A and tabulates the principal peaks together with their molar absorptivities.

The fluorination of neptunium(IV) fluoride and neptunium(IV) oxide

Abstract Rates of formation of NpF 6 by the reactions at 250–400°C of NpF 4 with fluorine, with BrF 3 , and with BrF 5 can be represented by a rate law that assumes the reaction site to be a continuously diminishing spherical interface. The rates of reaction of NpF 4 at 350°C lie in the order fluorine (100 mole%) > BrF 3 (6–13 mole%) > BrF 5 (33–35 mole%). Correlation of the derived rate constants by the Arrhenius equation yielded activation energies of 20 kcal/mole for the reaction of NpF 4 with fluorine and 26 kcal/mole for the reaction of NpF 4 with BrF 5 . The solid residues from the reactions of NpF 4 with either BrF 5 or fluorine contained no species other than NpF 4 . The fluorination of NpO 2 by either BrF 5 or fluorine proceeds through the intermediate compound NpF 4 . Thus, the fluorination of NpO 2 is analogous to that of PuO 2 , which proceeds through the intermediate compound PuF 4 , but differs from the fluorination of UO 2 , which proceeds through the intermediate compound UO 2 F 2 .

THE REACTION OF GASEOUS BROMINE PENTAFLUORIDE WITH URANIUM COMPOUNDS. I. THE KINETICS OF THE REACTIONS WITH UF

Abstract The kinetics of the gas-solid reactions between BrF5 und UF4 and UO2F2 have been studied in the temperature range 175–300°C and in the BrF5 partial pressure range of 130–370 torr. Both of these reactions produce UF6 as the main product, and in the case of the UF4-BrF5 reaction the intermediate uranium fluorides (U2F9, U4F17, and UF5) as minor products. Analysis of the reaction products of the UF4BrF5 reaction showed elemental bromine to be the other gaseous product of that reaction. The data were correlated using the diminishing sphere model which describes the gas-solid reaction occurring at a continuslly diminishing spherical interface. Values of the activation energy of 16·9 and 8·3 kcal/mole and of the order of the pressures dependence of 0·38 and 0·71 were calculated for the reactions with UF4 and UO2F2, respectively. The following equations were derived to represent the temperature and BrF5 partial pressure dependence of these two reactions. UF4BrF5: log k′ = 0·38 log PBrF5 (torr) − 3690/T(°K) + 4·286 UO2F2BrF5: log k′ = 0·71 log PBrF5 (torr) − 1810/T(°K)

sub 4

The kinetics of the reaction of BrF5 with U3O8, UO3 have been determined. The following equations represent the combined temperature and pressure dependence of the reactions U3O8;logk1=0·90logP−2000T−0·220 U2O2;logk1=0·84logP−1630T−0·270 U3O8;logk1=0·05logP−1680T−0·767 Activation energies of 9·2, 7·5 and 7·7 kcal/mole were calc. for reactions of U3O8, UO2 and UO3, respectively. Bromine was the other volatile product of the reaction along with UF6 and oxygen. These reactions proceed through the formation of UO2F2 as an intermediate. The presence of UF4 in the reaction of U3O8 and BrF5 was probably due to the interaction of the product UF6 with U3O8.

AND UO

Abstract Plutonium hexafluoride is decomposed by γ-radiation to produce plutonium tetrafluoride and elemental fluorine. The G value for the decomposition is 7·5 ± 1·7. Addition of one atmosphere of helium to 80 mm Hg plutonium hexafluoride resulted in a G for the decomposition of 7·2 ± 1·3. When two atmospheres helium were added to 80 mm Hg plutonium hexafluoride, the resulting G for the decomposition is 5·8 ± 0·9. A study of the decomposition in the presence of various amounts of krypton revealed a pronounced enhancement of the decomposition of plutonium hexafluoride at an electron fraction of krypton of 0·73 and an exposure dose of 1 × 10 8 rads. Mechanisms for the decomposition are proposed.

sub 2

Abstract At 300°C, the solid product of the reaction of PuF6(g) with LiF(s) was found to be LiPuF5. At 350–450°C, the solid product of the reaction of LiPuF5(s) with F2(g) was found to be Li4PuF8, and the solid product of the reaction of Li4PuF8(s) with F2(g) was found to be LiF. These experimental observations were used to infer that the reaction of PuF6 with LiF can be expected to produce a number of solid complexes that are analogues of the compounds known to exist in the condensed system LiF-UF4. Activation energies for the rates of reaction of LiPuF5 and Li4PuF8 with fluorine (1 atm) were found to be 12 and 10 kcal/mole PuF4, respectively. Fluorinations of the complexes proceeded with a first-order dependence on fluorine pressure in the range from 0·3 to 1 atm. The fluorination results also limited the value of the equilibrium constant, p F 2 p PuF 6 , for the reaction 4LiF(s) + PuF6(g) ⇄ Li4PuF8(s) + F2(g) at 400°C between 1 × 103 and 16 × 103.