Volume 95, Issue 11

Protactinium complexation with sulphate anions was investigated with the element at tracer scale ( ca. 10 -12 M) using the solvent extraction method. Extraction experiments were conducted using the chelating agent thenoyltrifluoroacetone (TTA) in toluene. The temperature was maintained constant at 25 °C, while the ionic strength was varying. Numerical treatment of the experimental data allowed the determination of complexation constants. Extrapolated constants to zero ionic strength, as well as interaction coefficients of the involved species were derived using SIT modelling.

Five separation methods by Eichrom column extraction chromatography were developed and implemented for performance control of a PUREX (Plutonium, Uranium Refining by EXtraction) test. One of them concerning the separation of actinides from fission products in the main PUREX raffinate is the subject of this work. The others, concerning separation between actinides, are described in another article submitted to the same journal. Analytical control of a PUREX process test implies measuring the neptunium, plutonium and uranium concentrations in the main extraction raffinate. The fission products are the major constituents of the raffinate, and thus prevent the use of direct L-line X-ray fluorescence (LXF) for these determinations. An actinide separation process by extraction chromatography with quantitative efficiency was therefore developed. This separation method necessary upstream from the LXF measurement was applied during the PUREX test in 2005 in ATALANTE (French acronym for “Alpha facilities and analysis laboratories, transuranics and reprocessing research”).

Five separation methods by Eichrom column extraction chromatography were developed and implemented for performance control of a PUREX (Plutonium, Uranium Refining by EXtraction) test. Four of them, concerning the separation between actinides, are described in this work. The latest, concerning the separation of actinides from fission products in a main raffinate is described in another article submitted to the same journal. For the production of U, Pu and Np streams following the “main extraction” step in the PUREX process, it is necessary to determine the concentration of the two residual actinides in the third actinide stream: i.e. determine the Pu and Np concentrations in the U flow, the U and Np concentrations in the Pu flow, and the U and Pu concentrations in the Np flow. The predominance of any of these three actinides in solution impedes direct L-line X-ray fluorescence LXF: chromatographic separation ensures quantitative separation efficiency for each of the two residual actinides prior to the LXF measurement, and is therefore performed in each case. A final separation method was developed to quantify the residual U in a Pu/Np flow for the Np/Pu partitioning step of the PUREX process. This separation is a prerequisite for LXF to eliminate any interference due to Pu and Np when measuring the U concentration. These separation methods necessary upstream from the LXF measurement were applied during the PUREX test in 2005 in ATALANTE (French acronym for “Alpha facilities and analysis laboratories, transuranics and reprocessing research”).

Low doses of gamma radiation were given to four different solvents containing C5-BTBP and CyMe 4 -BTBP, each molecule dissolved both in cyclohexanone and hexanol. Four corresponding solvents were kept unirradiated and used as references for the extraction experiments. Multiple samples were taken from both the irradiated solutions and the reference solutions at certain time intervals. The samples were used in extraction experiments with the radionuclides 241 Am and 152 Eu. The protection against radiolysis of the extracting molecules by the diluent used for dissolution without adding a scavenger molecule was checked. The interplay between the diluent and the side group of the extracting molecule for protection against radiolysis was also studied by keeping the same type of core molecule for binding to the metal ions and varying the diluent and side group. The results were unexpected. The presence of a cyclic molecule as both a side group or diluent seems to keep the extraction of europium almost unaffected by radiolysis, while americium behaves differently from solvent to solvent. The diluent alone does not protect the extracting molecule. In some of the studied systems there is a distinct change in the extraction behaviour of Am between the irradiated and reference solutions, an effect that is however only present at the beginning of the experimental series. At later times the difference in distribution ratios between the irradiated and reference solution is constant. This phenomenon is found only when the side group and diluent are structurally dissimilar.

During a hypothetical severe nuclear accident on a pressurized water reactor (PWR), it is of primary importance to assess potential radionuclide release into the environment, and thus to better understand the volatile ruthenium tetroxide stability, in the containment building, due to its high radiotoxicity. The stability of RuO 4 (g) in dry and moist air, under conditions representative of a PWR containment building, is investigated. RuO 4 decomposition occurs in bulk gas phase, without any specific affinity with surfaces. The kinetic rate law of RuO 4 reduction is found to be dependent on the presence of steam. The humidity seems to play a catalytic role, as well as the presence of ruthenium dioxide deposits. The temperature is also a key parameter. In the presence of steam, the half-life times of RuO [4] are found to be respectively of 5 h and 9 h at 90 °C and 40 °C. A chemical reaction scheme consistent with the experimental observations is proposed.

The production yield of iodine radionuclides ( 123/124 I) by solid target irradiation strongly depends on the quality of the tellurium (Te) target. To avoid poor quality 124 Te targets frequently obtained using the classical method, a new technology for high quality electroplated elemental 124 Te was developed. In this method, simultaneous preparation of four smooth, dense and homogeneous 124 Te targets was achieved within 1 h period. The prepared targets were capable of withstanding high beam currents without burning or losing the enriched material during bombardment. As a result, in comparison to the classical method, the overall yield of 123 I increased by nearly 25%.

Because of the high content of inactive molybdenum in neutron irradiated MoO 3 , large columns containing alumina or gel are needed to produce chromatographic 99 Mo→ 99m Tc generator. This results in large elution volumes containing relatively high 99 Mo breakthrough and low concentrations of 99m TcO 4 - . The decrease in specific volume of 99m Tc places a limitation on reconstitution of some kits for 99m Tc radiopharmaceuticals applied in diagnostic nuclear medicine. Hence concentration technique is mandatory for effective utilization of ( n ,γ) produced 99 Mo/ 99m Tc generators at the start of its life whereas in case of fission 99 Mo/ 99m Tc generator the technique may be quite useful at the end of first week of its life. We report post elution concentration of 99m Tc using in house prepared Pb column. The high bolus volumes (10–60 ml saline) can conveniently be concentrated in ∼1 ml of saline.

Thallium-201 ( T 1/2 =3.04 d) in Tl + form was converted to Tl 3+ cation in presence of O 3 in 6 M HCl controlled by RTLC/gel electrophoresis methods and used in the labeling of human polyclonal antibody (HIgG) after conjugation with freshly prepared cyclic DTPA-dianhydride. The best results of the conjugation were obtained by the addition of 1 mL of a HIgG pharmaceutical solution (5 mg/ml, in phosphate buffer, pH=7) to a glass tube pre-coated with DTPA-dianhydride (0.01 mg) at 25 °C with continuous mild stirring for 30 min. The final isotonic [ 201 Tl](III)-DTPA-HIgG complex was checked by radio-TLC using several solvent systems to ensure the formation of only one species followed by filtration through a 0.22 μ filter (specific activity= 33.7 TBq/mM, radiochemical purity >95%). Preliminary bio-distribution studies in normal and inflammation-bearing rats were performed. The target/skin and target/blood ratios were 4 and 6 after 28 h respectively, showing the selectivity of the radiopharmaceutical for the inflammatory lesions.