Band 101, Heft 8

Nuclear reaction cross section data are of great significance in optimisation of production routes of radionuclides. This article deals with some newer aspects of data research related to production of both standard and novel radionuclides. The recent work to standardise the known data is discussed and new measurements with regard to further optimisation of production routes of some commonly used radionuclides are mentioned. Attempts to increase the specific activity of some reactor-produced radionuclides through the use of charged-particle induced reactions are outlined. The jeopardy in the supply of 99m Tc via a fission-produced 99 Mo / 99m Tc generator is considered and its possible direct production at a cyclotron is briefly discussed. Regarding the novel radionuclides, development work is presently focussed on non-standard positron emitters for diagnosis and on low-range highly ionising radiation emitters for internal radiotherapy. Recent nuclear reaction cross section measurements related to the production of the two types of radionuclides are briefly reviewed and some anticipated trends in nuclear data research are considered.

Targets withstanding high beam power for production of 68 Ge by proton irradiation of Ga were developed using electrodeposition of Ga/Ni alloy (70/30%) on thick Cu backings. Cross sections for reactions, induced by protons (up to 36MeV) and deuterons (up to 50MeV), producing γ-emitting radioisotopes with half-lives longer than 2 h were measured in a stacked-foil irradiation using thin Ga/Ni targets produced with this technique. Excitation functions for 68,69 Ge are discussed, relative to the monitor reactions nat Cu(p, x) 62 Zn or nat Al(d, x) 24,22 Na. The results are compared to the scarce literature values. From derived thick target yields, optimal energy domain and batch yields for 68 Ge production were calculated and contamination (from 69 Ge and 71 Ge) is discussed. A PC-controlled, automated dissolution and separation chemistry set-up for delivery of nca 69 Ge was developed (yield about 90%) and implemented in an industrial system ready to be mounted in a hot cell.

With respect to the production of no-carrieradded 52 Mn nuclear reactions on natural chromium were investigated. Cross sections of the reactions nat Cr( p, x ) 48 V, 48 , 49 , 51 Cr, 52g,m Mn were determined in the proton energy range of 7.6 to 45MeV. Additionally, production yields of 52g,m Mn and 51 Cr were measured in the energy range from 8.2 to 16 . 9MeV and therefrom the calculated saturation thick target yields were obtained as (2 . 55±0 . 31), (6 . 96±0 . 57), and (1 . 53±0 . 15) GBq / μA, respectively. For in vivo applications like PET, low toxicity is critical and sufficient activity of a radiolabelled compound mandatory. Thus, additional purification steps after separation of radionuclides and target materials have to be avoided. However, no isolation procedure has been reported in the literature so far where radiomanganese is directly obtained in a nonhazardous solution. Therefore a new separation procedure was developed utilizing the cation-exchange resin DOWEX 50W×8 (H + -form). 52g Mn was quantitatively isolated from “bulk” chromium after 3 to 4 h in non-hazardous 0 . 067M ammonium citrate solution. Up to 99% of 52g Mn activity was harvested within 10 to 15 mL eluent solution with no measureable 51 Cr impurities.

The interactions of high-energy protons with matter produce a large variety of radionuclides due to the diversity of the induced nuclear reactions. Some of those isotopes are very rare, exotic, and, in many cases, difficult to produce by complementary methods. Valuable isotopes, interesting for scientific and technological applications, can be extracted from samples stemming from the surroundings or components of a proton accelerator, in particular if the load of the initial particle current is relatively high (esp. in the Megawatt range). Since PSI operates one of the most powerful high-energy proton accelerators world-wide, this facility is best-suited for an R&D program aimed at “harvesting” such isotopes. An initiative called ERAWAST (Exotic Radionuclides from Accelerator Waste for Science and Technology) was started in 2006 in order to identify and motivate potential users. After six years, first achievements as well as realistic future plans for front-end experiments are available. The present contribution describes radiochemical separation techniques for selected examples, summarizes the most prominent results and gives an outlook on the upcoming experiments within the scope of the ERAWAST program.

7 Be is a key radionuclide for investigation of several astrophysical processes and phenomena. In addition, it is used as a tracer in wear measurements. It is produced in considerable amounts in the cooling water (D 2 O) of the Spallation Induced Neutron Source (SINQ) facility at PSI by spallation reactions on 16 O with the generated fast neutrons. A shielded ion-exchange filter containing 100 mL of the mixed-bed ion exchanger LEWATIT was installed as a bypass for the cooling water into the cooling loop of SINQ for three months. The collected activity of 7 Be was in the range of several hundred GBq. Further, the 7 Be was separated and purified in a hot-cell remotely-controlled using a separation system installed. With the exception of 10 Be, radioactive byproducts can be neglected, so that this cooling water could serve as an ideal source for highly active 7 Be-samples. The facility is capable of producing 7 Be with activities up to 1 TBq per year. The 7 Be sample preparation is described in detail and the possible uses are discussed. In particular some preliminary results of 7 Be ion beam production are presented.

For the solvent extraction experiment on element 104 (Rf), solvent extraction of Zr and Hf as its homologues was performed in tributylphosphate (TBP) / hydrochloric acid (HCl) system using the carrier-free radiotracers 88 Zr and 175 Hf. Time dependences of the distribution ratios of Zr and Hf were investigated using 6.1 and 10 . 0M HCl and 0.5 and 2 . 0M TBP benzene solutions. The distribution ratios in equilibrium were determined for these elements as a function of HCl concentrations in the range of 4 . 1-10 . 2M. We found that the neutral chloride complexes of Zr and Hf were formed and extracted into the organic phase within 20 min in HCl with a concentration higher than 6 M. From the results, we propose that solvent extraction of Rf from 4-8M HCl into 2 . 0M TBP benzene is suitable for investigating the chloride complexation properties of Rf. In addition, for the development of the rapid liquid-liquid extraction apparatus, three types of microchannel devices, namely, a micro reactor, capillary tube and micro-chemical chip, were tested as a mixing-solution part in the apparatus. The chemical reactions of Zr and Hf in the extraction were found to be fast only when using the microchemical chip, which is important for investigations with the 68-s 261 Rf.

Different radiometric techniques for the determination of 238 U, 226 Ra and 210 Pb are presented and compared in terms of detection limits with mass spectrometric techniques. It can be concluded that when samples with low activity concentrations have to be measured, the method of choice in the case of 238 U should be either RNAA / INAA or alpha particle spectrometry. In the case of 226 Ra and 210 Pb the best performance can be expected by the alpha spectrometry, whereas drawback of waiting for establishing secular radioactive equilibrium of 210 Pb with 210 Po makes techniques like beta counting and LSC more attractive for the determination of 210 Pb. In addition, a case study on monitoring the former uranium mine Žirovski vrh is presented along with the used methodology and the summarised measurement results.

129 I, a long-lived radionuclide, is important in view of geological repository of nuclear waste, and environmental tracing applications related to diverse natural processes of iodine. The environmental behaviors and bioavailability of 129 I are highly related to its species. A number of methods have been reported for speciation analysis of 129 I in a variety of environmental samples. These methods have been applied in many researches, including conversion processes of iodine species in marine and terrestrial systems, migration and retention of iodine in soil and sediment, geochemical cycling of iodine, as well as studies on atmospheric chemistry of iodine. This article aims to review these methods and their applications in environmental research.