Irradiated Uranium Target Research Articles

Recovery of high specific activity molybdenum-99 from accelerator-induced fission on low-enriched uranium for technetium-99m generators

A new process was developed to recover high specific activity (no carrier added) 99Mo from electron-accelerator irradiated U3O8 or uranyl sulfate targets. The process leverages a novel solvent extraction scheme to recover Mo using di(2-ethylhexyl) phosphoric acid following uranium and transuranics removal with tri-n-butyl phosphate. An anion-exchange concentration column step provides a final purification, generating pure 99Mo intended for making 99Mo/99mTc generators. The process was demonstrated with irradiated uranium targets resulting in more than 95% 99Mo recovery and without presence of fission products or actinides in the product.

Development and trials of a process for extraction recovery of 99Mo for medical purposes from dissolved irradiated uranium targets

A process was developed for extraction recovery of 99Mo from irradiated enriched uranium target. Dissolution of the uranium–aluminum composite in nitric acid in the presence of fluoride ions with the addition of mercury ions, which are subsequently separated by precipitation in the form of iodide, was suggested. Conditions were determined for joint recovery of uranium and molybdenum into the organic phase with 10–15% solutions of HDEHP in a paraffin diluent in the presence of equimolar amounts of TBP, and also for selective backwashing of Mo into a strongly acidic H2O2 solution with the backwash reflux. The efficiency of using a mixture of DTPA with methylamine carbonate for uranium backwashing and solvent regeneration was demonstrated. The recovery and separation process was successfully tested on simulated and real solutions in 20- and 19-step cascades of centrifugal contactors with the feed adjuster without Mo backwash reflux and with its reflux, respectively.

Ion-pair extraction of uranyl ion from aqueous medium using crown ethers

Ion-pair extraction behaviour of uranyl ion from aqueous solutions was studied at pH 3.0 employing crown ethers viz. benzo 15 crown 5 (B15C5), 18 crown 6 (18C6), dibenzo 18 crown 6 (DB18C6), and dibenzo 24 crown 8 (DB24C8) in chloroform as the organic phase and picric acid as the organophilic counter anion. The stoichiometry of the extracted species corresponded to [UO 2(crown ether) n] 2+·[pic −] 2 where n=1.5 for benzo 15 crown 5 and 1 for 18 crown 6 as well as dibenzo 18 crown 6. Adducts of DB24C8 could not be observed as practically no extraction was possible using this reagent. The separation behaviour of fission products from an irradiated uranium target was also studied. An interesting observation on the separation of trivalent lanthanides from uranyl ion is reported.

Seperation of neptunium from irradiated uranium targets

A new chemical method based in two separation steps was developed to isolate235Np from uranium targets irradiated with charged particles. Neptunium and plutonium are separated from uranium and most of the fission products by ion exchange. Then, neptunium is isolated from plutonium and remaining contaminants by extraction chromatography with tributyl phosphate in hydrochloric acid solution. High decontamination was achieved.

Radioiodine Speciation in the Hot Cell Effluent Gases of a Radiopharmaceutical Production Facility

In order to characterize the various chemical forms of airborne radioiodine species, grab-sampling measurements were conducted at the hot cell laboratory of a radiopharmaceutical production facility, using a selective-adsorbent-iodine filter system. Volatile radioiodine species were produced in the hot cell process which extracted the fission product 99Mo from the irradiated uranium target. The effluent gases were then released through the hot cell filter bank and the main filter bank. Two samplings were made, one at the inlet and one at the outlet of the hot cell filter bank. In comparison with other radioiodine isotopes detected, higher than expected concentrations of 132I were found, primarily in the form of organic iodide--an observation that could be explained by the beta decay of 132Te, the precursor of 132I, in the hot cell waste solution. The relative distribution of airborne 132I was considerably different from that of other iodine radioisotopes. An unexpected component of these distributions was radioiodine penetrating the silver zeolite filter and adsorbed on a triethylenediamine (TEDA) impregnated charcoal filter.

Study on the Separation of Fission Products of Uranium Fission at High Temperatures during Irradiation in the Reactor

Using the earlier investigations into the fission-product separation from irradiated uranium-targets, a special irradiation capsule equipped with U3O8-impregnated ceramic target, which allows transfer of the fission-heat preferentially by radiation, was developed. In the irradiation experiments it was demonstrated that a target temperature desired is adjustable in the range from 1100 to 1500°C by variation of the target parameters resp. neutron flux density. The fission products, released from two target-types during irradiation by this method, were detected by a remote-controlled dissolution process in the capsule. The values obtained as the fractional release of 5 fission products can be applied to the development of a new thermal process for the production of fission molybdenum.

Chemical Separations of Actinide Elements from Heavy-Ion Irradiated Uranium Targets

Chemical Separations of Actinide Elements from Heavy-Ion Irradiated Uranium Targets

Separation of heavier rare earths from neutron irradiated uranium targets

A radiochemical method is described for the separation of heavier rare earths from the fission of uranium. The method is particularly suitable for the separation of low yield (10−5%–10−7%), highly asymmetric rare earth fission products viz.179,177Lu,175Yb,173Tm,172,171Er,167Ho and161,160Tb in the neutron induced fission of natural and depleted uranium targets. Additional separation steps have been incorporated for decontamination from239Np (an activation product) and93-90Y (a high fission-yield product) which show similar chemical behaviour to rare earths. Separation of individual rare earths is achieved by a cation exchange method performed at 80°C by elution with α-hydroxyisobutyric acid (α-HIBA).

Chemical separations for super-heavy element searches in irradiated uranium targets

A chemical procedure is outlined for super-heavy element searches in irradiated uranium targets. The separation scheme is based on the wide range in stability and extractability of chlorometallic complexes by alkyl tertiary and quaternary ammonium chlorides and the wide range of extractability of metal ions by di-2-ethylhexylorthophosphoric acid. These two properties are utilized in various extraction chromatographic systems. The procedure was developed using elements in the sixth period as chemical homologues of super-heavy elements and tested on 100–200 mg irradiated uranium targets. The separation schemes are also applicable to other irradiated targets.