G.F. Steyn

The production of 88Y in the proton bombardment of natSr: new excitation and separation studies

The cyclotron production of (88)Y at iThemba LABS is performed via the reaction (88)Sr(p,n)(88)Y. The yields obtained were inconsistent with nuclear data obtained from the literature and the excitation function of the nuclear reaction was re-measured, using a differentiation of thick-target production rate measurements. Ion exchange chromatographic methods are described to separate (88)Y from (nat)Sr target material using AG MP-1 resin and AG 50W-X4 resins, respectively.

Carbon radioactivity of 223Ac and a search for nitrogen emission

A very intense 227Pa source was produced in order to study the possible 14C and 15N spontaneous emission from 223Ac. After the irradiation of a hemispherical, highly efficient array of nuclear track detectors, about 350 Carbon events were found leading to a branching ratio with respect to alpha decay B = 3.2 10−11. Comparison with other 14C emitters allows the study of the influence of even-odd effects on cluster radioactivity.

Design calculations for a local radiation shield of a radioisotope production target bombardment station

Abstract Multigroup discrete ordinates radiation transport calculations were performed to evaluate the present configuration of the local radiation shield of the target bombardment station for radioisotope production at the National Accelerator Centre. Calculated neutron and γ-ray dose rates and dose attenuation factors for this shield were compared with experimental measurements. Finally, a parametrical shield optimization study was performed.

Excitation Functions and Production Rates of Radionuclides Produced in the Proton Bombardment of natPr and natLa

Excitation functions and production rates are presented for various radionuclides formed in the bombardment of natPr and natLa with protons. Comparisons are made with theoretical predictions based on the geometry dependent hybrid model. Alternative production routes for 139Pr and 139Ce are investigated.

The production of 82Sr using larger format RbCl targets

The production of (82)Sr at iThemba LABS is performed by the proton bombardment of a RbCl target using the facilitys Vertical-Beam Target Station (VBTS). (82)Sr is separated from the target material using a method based on target dissolution, using dilute ammonium chloride solution, and the use of chromatographic methods on Purolite S950 ion exchange resin. After performing a further purification step using AG MP-50 macroporous cation exchange resin, the result is a product with a high radionuclidic purity and negligible Rb and Fe impurity content.

The use of selective volatization in the separation of 68Ge from irradiated Ga targets

Cyclotron-produced (68)Ge can be separated from its Ga target material by dissolving the target in aqua regia and collecting the volatile (68)Ge in a solution containing 1.0M NaOH and 2% Na₂SO₃. The solution is then acidified with HF before being loaded onto a column containing AG MP-1 anion exchange resin. The column is rinsed with dilute HF to remove any remaining impurities, before eluting the desired product with 0.1M HCl. A radiochemically pure product is obtained.

Production of 28 Mg by bombardment of nat Cl with 200MeV protons: Proof-of-concept study for a stacked LiCl target

A stacked target consisting of ten Al-encapsulated LiCl discs, for producing (28)Mg via the (nat)Cl(p,X)(28)Mg process in the energy region 50-200MeV, is described. This target was irradiated with a 200MeV beam at an intensity of 100nA, providing information on both yield and outscattering losses. Results of a Monte Carlo modelling of the beam and target, by means of the code MCNPX, are also presented. Similar Al-encapsulated LiCl discs were individually irradiated with 66MeV proton beams of 65 and 90μA, respectively, to study their behaviour under high-intensity bombardment. Once removed from the Al encapsulation, the (28)Mg can be separated from the LiCl target material efficiently, using a 12.5cm x 1cm(2) column containing Purolite S950 chelating resin. The eluate contains (7)Be but no other measurable radio-contaminants. The removal of the (7)Be contaminant is performed by cation exchange chromatography in malate media, with (28)Mg being retained by the resin and (7)Be eluted.

Excitation functions for the production of some radioisotopes of Cs, Xe and I in proton bombardment of natXe up to 100 MeV

Abstract Integral excitation functions for the production of 16 radioisotopes of Cs, Xe and I in the bombardment of natXe with protons were measured up to 100 MeV. The results were compared with geometry-dependent hybrid-model calculations performed by means of the computer code ALICE/85/300, employing both the standard methods offered by the code to take nucleon pairing and shell-structure effects into account. Good overall agreement was obtained in both cases.

The production of 127Xe via natXe(p,xn)127Cs → 127Xe

Abstract Effective cross-sections for the production of 127Cs in the bombardment of natXe with protons were measured from threshold up to 100 MeV. From the integral excitation function obtained, yield curves for 127Xe, produced via the natXe(p,xn)127Cs → 127Xe route, were derived for a full range of gas target thicknesses. These curves can be used for the optimization of the production of 127Xe within specific practical incident energy and target thickness constraints. The expected optimum yield for a representative production gas target (1.64 g/cm2 thick) is 6.7 MBq/μAh (obtained at an incident energy of 39.3 MeV).

Concurrent spectrometry of annihilation radiation and characteristic gamma-rays for activity assessment of selected positron emitters

A method is described to determine the activity of non-pure positron emitters in a radionuclide production environment by assessing the 511keV annihilation radiation concurrently with selected γ-lines, using a single High-Purity Germanium (HPGe) detector. Liquid sources of 22Na, 52Fe, 52mMn, 61Cu, 64Cu, 65Zn, 66Ga, 68Ga, 82Rb, 88Y, 89Zr and 132Cs were prepared specifically for this study. Acrylic absorbers surrounding the sources ensured that the emitted β+-particles could not escape and annihilate away from the source region. The absorber thickness was matched to the maximum β+ energy for each radionuclide. The effect on the 511keV detection efficiency by the non-homogeneous distribution of annihilation sites inside the source and absorber materials was investigated by means of Monte Carlo simulations. It was found that no self-absorption corrections other than those implicit to the detector calibration procedure needed to be applied. The medically important radionuclide, 64Cu, is of particular interest as its strongest characteristic γ-ray has an intensity of less than 0.5%. In spite of the weakness of its emission intensity, the 1346keV γ-line is shown to be suitable for quantifying the 64Cu production yield after chemical separation from the target matrix has been performed.