Band 99, Heft 12 -

Proton irradiation of natural and enriched SrCl 2 targets was used to produce PET radioisotope 86 Y. The proton energy was degraded from the incident 117.8 MeV to induce the 88 Sr( p ,3 n ) reaction. For the irradiation three pellets made of nat SrCl 2 (6.61 and 74.49 g) and 88 SrCl 2 (5.02 g) were pressed and individually encapsulated in stainless steel target bodies. The two smaller targets were irradiated for 0.5–1 h at the energy ∼ 46→37 MeV to take advantage of the peak in the excitation function of the 88 Sr( p ,3 n ) reaction. The larger target was irradiated at 66.4→44.6 MeV. The irradiated pellets were chemically processed to selectively separate 86 Y radioisotope using Eichrom DGA ( N , N , N´ , N´ -tetra- n -octyldiglycolamide) resin. The production yields of 86 Y were determined to be 10–13 mCi/μA h. Coproduction of 87m Y in the final product was 34% for nat SrCl 2 and 54% for 88 SrCl 2 target. The chemical separation yield of yttrium reached 88–92%. The developed chemical procedure allows for the same day processing and shipment of the isotope to users.

The experimental proton induced reaction cross sections on some elements of the Havar alloy were measured using the activation method and the well established stacked-foil technique combined with high resolution gamma-ray spectroscopy. They included the reactions nat Ni( p,x ) 57 Ni, nat Co( p,x ) 58(m+g) Co and nat Mo( p,x ) 94g,95g,96(m+g) Tc, the aim being to obtain reliable data in the proton energy range up to 26 MeV for some important reactions to be used in the proton activation analysis of steel or other alloys. Irradiations were performed using the CS-30 Cyclotron at KFSH and RC, Riyadh, Saudi Arabia. The activity measurements were carried out in PNU laboratories, Riyadh, Saudi Arabia. The experimental excitation functions for the investigated reactions were constructed and compared with the performed computed theoretical nuclear model calculations using two different codes: ALICE-IPPE and TALYS. A comparison between our measured cross-section values and the available published data is also presented, with a view to checking the consistency of the reported experimental work from various laboratories.

The half-life of 67 Cu was newly determined by measurement of its 185 keV γ -ray (48.7%) over the period of 13 d (approx. 5 ×  T 1/2 ). 67 Cu was prepared by deuteron irradiation of enriched 70 Zn targets. The 67 Cu half-life value which resulted from five independent measurements is estimated to be 61.81(22) h.

The formation of aqueous Cm(III) phosphate complexes was studied at room temperature by time-resolved laser-induced fluorescence spectroscopy (TRLFS) in 0.1 M NaClO 4 solutions. The experiments were perfomed at a fixed total Cm(III) concentration of 3 × 10 7 or 2 × 10 8  M by varying the phosphoric acid concentration (3 × 10 5 –0.1 M) and the pH (1.4–6.0). The red shift of the excitation and emission spectra, as well as the increase of luminescence lifetimes clearly showed the influence of phosphate on the aqueous Cm(III) speciation. In acidic phosphate solutions ([H 3 PO 4 ] ≤0.1 M, pH 1.4–2.6) an increase in luminescence intensity was detected due to complexation with H 2 PO 4 − . At [H 3 PO 4 ] ≥4 × 10 4  M and between pH 4.0 and 6.0 in general a decrease in luminescence intensity affiliates the complexation with HPO 4 2− . Two Cm(III)-phosphate complexes could be identified from the emission data, CmH 2 PO 4 2+ and CmHPO 4 + , having peak maxima at 599.6 and 600.8 nm, respectively. TRLFS in combination with ultra-filtration (1 kD) showed that the formation of CmHPO 4 + is accompanied by the generation of Cm(III)-phosphate colloids especially at [H 3 PO 4 ] ≥0.002 M and pH ≥ 5. Cm(III)-phosphate colloids formed at pH 5 and 6 are characterized by an emission maximum at 603.1 nm. Based on the factor analysis of the emission data the stability constants of the two complexes were calculated to be log β 121 = 20.23 ± 0.13 and log β 111 = 16.54 ± 0.80 at an ionic strength of 0.1 M (NaClO 4 ).

The preferential solvation of Cm(III) in binary aqueous mixtures of MeOH, t BuOH, DMSO, MeCN and acetone is studied at varied solvent composition. Solvation is investigated by time-resolved laser fluorescence spectroscopy and emission spectra and fluorescence lifetime data are obtained. At high mole fractions of organic solvent, preferential solvation of Cm(III) increases in the order: Me 2 CO < t BuOH ≈ MeOH < MeCN < H 2 O < DMSO. Thermodynamic data are derived from the spectroscopic results showing small positive standard Gibbs energies for the transfer of Cm(III) into the various solvent mixtures except for DMSO mixtures where negative values are found. The spectroscopically obtained enthalpies of transfer are fitted to a solvation model using the model parameters Δ Δ Hº 12 and ( αn + βN )º, rendering valuable information on the interaction of Cm(III) with the solvent molecules. Cm(III)-solvent interaction increases in the order: t BuOH < MeCN < MeOH < DMSO.

According to performance assessment reports for high-level radioactive waste repositories, 79 Se is a radionuclide that could represent a potential threat to the biosphere. Therefore knowledge of its geochemical behavior during its transport in aqueous solutions is fundamental to assess the safety of repository sites. Selenium is often associated with sulfides such as pyrite, a frequent minor constituent of host rocks and bentonite backfills considered for radioactive waste disposal. In this study, we investigated the uptake of Se by Fe sulfides synthesized in batch experiments under anoxic conditions. Results from X-ray diffraction and scanning electron microscopy analyses reveal the formation of pyrite and mackinawite. More than 98% of the Se added to solutions (initial concentration: 10 −3 –10 −6  mol/l) was taken up by the Fe sulfide minerals. Focused ion beam analysis shows an inhomogeneous Se distribution with a higher accumulation in the center of the pyrite grains, probably due to the progressive depletion of Se from solution with regard to S. The results imply that pyrite and its most important precursor phase, mackinawite, are efficient in removing selenium from solution, which may contribute in reducing the mobility of 79 Se released from radioactive waste.

In this study a ZrO 2 -MgO inert matrix fuel containing UO 2 (a PuO 2 homolog) and Er 2 O 3 (burnable poison) was evaluated under environmental conditions to assess its performance as a waste form should a direct disposal scheme be adopted. A Soxhlet degradation study was used to assess the durability of the ceramic in contact with water for 2000 h over a range of ZrO 2 to MgO ratios. This quantified the amount of ZrO 2 required to stabilize the material against degradation. A pulse flow dissolution study was used to investigate the stability of the material in aqueous environments relevant to a repository. Although the MgO phase was dissolved, the material was found to retain Zr, U, and Er oxides while immersed in brine, silicate-bicarbonate solution, or deionized water for 3700 h. Aqueous media with a high level of silicate formed a Mg 2 SiO 4 phase at the surface, which retarded further degradation of the material. Brine was found to be the most aggressive solution in altering the material. The data provides an evaluation of the mixed inert matrix behavior under a range of potential repository conditions.

In this work the applicability of Fourier-transform infrared spectrometry (FTIR) for nuclear forensic studies of uranium ore concentrates (UOC) are investigated. The technique was used for the identification of the type of uranium compound and various process-related impurities, which can give information on the production method of the material. The measured spectra were evaluated also by statistical means, using the soft independent modelling of class analogy (SIMCA) technique to reveal less apparent similarities between the measured UOC samples.

‘Actinide partitioning’ studies were attempted by hollow fibre supported liquid membrane (HFSLM) technique using pressurized heavy water reactor simulated high level waste (PHWR-SHLW) as the feed. Two diglycolamide extractants for actinide partitioning, viz. 0.1 M TODGA ( N , N , N´ , N´ -tetraoctyl diglycolamide) + 0.5 M DHOA ( N , N -dihexyl octanamide) and 0.2 M T2EHDGA ( N , N , N´ , N´ -tetra-2-ethylhexyl diglycolamide) + 30% iso -decanol in n -dodecane were used as the carrier solvent. Quantitative recovery of all trivalent actinides and lanthanides from PHWR-SHLW was achieved with both the carriers within 30 min when the feed volume was 0.5 L. On the other hand, about 18 h were necessary for a similar study carried out using a feed volume of 20 L. None of the other elements present in the PHWR-SHLW were transported, except small quantities of Sr and Mo. The product could be concentrated to two and four times by maintaining the feed to receiver phase volume ratio of 2:1 and 4:1, respectively. The transport behaviour of trivalent actinides and lanthanides by the two diglycolamide extractants were remarkably similar. The present studies revealed that diglycolamide-HFSLM system offers a promising alternative approach for ‘actinide partitioning’, where the use of organic solvent inventory could be drastically reduced. A mathematical model was developed and there was good agreement between the predicted and experimentally obtained data.