Pre-feasibility Study for Establishing Radioisotope and Radiopharmaceutical Production Facilities in Developing Countries.

BACKGROUND: A significant number of developing countries have no facilities to produce medical radioisotopes and radiopharmaceuticals. OBJECTIVE: In this paper we show that access to life-saving radioisotopes and radiopharmaceuticals and the geographical distribution of corresponding infrastructure is highly unbalanced worldwide. METHODS: We discuss the main issues which need to be addressed in order to establish the production of radioisotopes and radiopharmaceuticals, which are especially important for developing countries as newcomers in the field. The data was gathered from several sources, including databases maintained by the International Atomic Energy Agency (IAEA), World Health Organization (WHO), and other international organizations; personal interactions with representatives in the nuclear medicine field from different regions of the world; and relevant literature. RESULTS: Developing radioisotope and radiopharmaceutical production program and installing corresponding infrastructure requires significant investments, both man-power and financial. Support already exists to help developing countries establish their medical radioisotope production installations from several organizations, such as IAEA. CONCLUSION: This work clearly shows that access to life-saving radioisotopes and the geographical distribution of corresponding infrastructure is highly unbalanced. Technology transfer is important as it not only immediately benefits patients, but also provides employment, economic activity and general prosperity in the region to where the technology transfer is implemented.

Photonuclear production of yttrium-88 - A high energy gamma emitter for hydrocarbon extraction applications.

The use of fracing has risen over the past decade and revolutionized energy production in the US. However, there is still an impetus for further optimization of the extraction of oil and natural gas from vast shale reservoirs. In this work, we discuss photonuclear production of yttrium-88 as a promising radiotracer for fracing operations. Single neutron knock-out from natural monoisotopic yttrium-89 is an inexpensive process resulting in high activity of 88Y with minimal impurities. MCNPX simulations were performed to estimate the 88Y yield. Irradiations of natural yttrium using a 32 MeV electron linac equipped with a tungsten bremsstrahlung converter were done to benchmark the simulations. Activities of 88Y, 87gY, and 87mY were measured and found to be in good agreement with the predictions.

Sc-47 production from titanium targets using electron linacs.

In this work we have studied the feasibility of photonuclear production of (47)Sc from (48)Ti via (48)Ti(γ,p)(47)Sc reaction. Photon flux distribution for electron beams of different energies incident on tungsten converter was calculated using MCNPX radiation transport code. (47)Sc production rate dependence on electron beam energy was found and (47)Sc yields were estimated. It was shown that irradiating a natural Ti target results in numerous scandium isotopes which can reduce the specific activity of (47)Sc. Irradiating enriched (48)Ti targets with a 22MeV 1mA beam will result in hundreds of MBq/g activity of (47)Sc and no other isotopes of scandium. Decreasing the size of the target will result in much higher average photon flux through the target and tens of GBq/g levels of specific activity of (47)Sc. Increasing the beam energy will also result in higher yields, but as soon as the electron energy exceeds the (48)Ti(γ,np)(46)Sc reaction threshold, (46)Sc starts being produced and its fraction in total scandium atoms grows as beam energy increases. The results of the simulations were benchmarked by irradiating natural titanium foil with 22MeV electron beam incident on the tungsten converter. Measured (47)Sc activities were found to be in very good agreement with the predictions.

(47)Ca production for (47)Ca/(47)Sc generator system using electron linacs.

In this work we have studied the feasibility of photonuclear production of (47)Ca from (48)Ca for (47)Ca/(47)Sc generators. Photon flux distribution for electron beams of different energies incident on a tungsten converter was calculated using the MCNPX radiation transport code. The (47)Ca production rate dependence on electron beam energy was found and (47)Ca/(47)Sc yields were estimated for a 40MeV electron beam. It was shown that irradiating enriched targets with a 40MeV, 1mA beam will result in tens of MBq g(-1) (few mCi g(-1)) activity of (47)Sc. The results of the simulations were benchmarked by irradiating 22.5g of CaCl2 powder with a 39MeV electron beam incident on a tungsten converter. Measured (47)Ca/(47)Sc activities were found to be in very good agreement with the predictions.

Target optimization for the photonuclear production of radioisotopes.

In this paper we discuss the optimum shape of a target for photonuclear production of radioisotopes using an electron linear accelerator. Different target geometries such as right cylinder, conical frustum, Gaussian volume of revolution and semi-ellipsoid have been considered for the production of (67)Cu via (68)Zn(γ,p)(67)Cu photonuclear reaction. The specific activity (SA) of (67)Cu was simulated for each target shape. Optimum ratio of radius to height for cylindrical targets was found to be between 0.2 and 0.25 for target masses ranging from 20 g to 100 g. It was shown that while some unconventional target shapes, such as semi-elliptical volume of revolution, result in slightly higher specific activities than cylindrical targets, the advantage is not significant and is outweighed by the complexity of the target production and handling. Power deposition into the target was modeled and the trade-off between the maximization of (67)Cu yield and the minimization of target heating has been discussed. The (67)Cu case can easily be extended for production of many other isotopes.

Production of medical radioisotopes with linear accelerators.

In this study, we discuss producing radioisotopes using linear electron accelerators and address production and separation issues of photoneutron (γ,n) and photoproton (γ,p) reactions. While (γ,n) reactions typically result in greater yields, separating product nuclides from the target is challenging since the chemical properties of both are the same. Yields of (γ,p) reactions are typically lower than (γ,n) ones, however they have the advantage that target and product nuclides belong to different chemical species so their separation is often not such an intricate problem. In this paper we consider two examples, (100)Mo(γ,n)(99)Mo and (68)Zn(γ,p)(67)Cu, of photonuclear reactions. Monte-Carlo simulations of the yields are benchmarked with experimental data obtained at the Idaho Accelerator Center using a 44MeV linear electron accelerator. We propose using a kinematic recoil method for photoneutron production. This technique requires (100)Mo target material to be in the form of nanoparticles coated with a catcher material. During irradiation, (99)Mo atoms recoil and get trapped in the coating layer. After irradiation, the coating is dissolved and (99)Mo is collected. At the same time, (100)Mo nanoparticles can be reused. For the photoproduction method, (67)Cu can be separated from the target nuclides, (68)Zn, using standard exchange chromatography methods. Monte-Carlo simulations were performed and the (99)Mo activity was predicted to be about 7MBq/(g(⁎)kW(⁎)h) while (67)Cu activity was predicted to be about 1MBq/(g(⁎)kW(⁎)h). Experimental data confirm the predicted activity for both cases which proves that photonuclear reactions can be used to produce radioisotopes. Lists of medical isotopes which might be obtained using photonuclear reactions have been compiled and are included as well.

Long-term variations in the surface air 7Be concentration and climatic changes.

We have used EML Surface Air Sampling Program (SASP) data to analyze the long-term trend in (7)Be surface concentration and address possible correlation between this long-term trend and climatic changes, namely changes in precipitation patterns and temperature. In this paper we present (7)Be concentration data from 23 sites, spanning over 25 years, all over the world, and extract long-term trend parameter using two independent techniques. The (7)Be concentrations in most stations show a pronounced decreasing trend, potentially corresponding to statistically significant changes in transporting (7)Be from upper atmosphere source to these sites. Weak negative correlation between (7)Be concentration and amount of precipitation was also observed. However, more data from more representative sites around the world are needed the statistical robustness of this trend.