On line isotope separation techniques (ISOL) for production of ion beams of short-lived radionuclides require fast separation of nuclear reaction products from irradiated target materials followed by a transfer into an ion source. As a first step in this transport chain the release of nuclear reaction products from refractory metals has been studied systematically and will be reviewed. High-energy protons (500 -1000 MeV) produce a large number of radionuclides in irradiated materials via the nuclear reactions spallation, fission and fragmentation. Foils and powders of Re, W, Ta, Hf, Mo, Nb, Zr, Y, Ti and C were irradiated with protons (600 -1000 MeV) at the Dubna synchrocyclotron, the CERN synchrocyclotron and at the CERN PS-booster to produce different nuclear reaction products.The main topic of the paper is the determination of diffusion coefficients of the nuclear reaction products in the target matrix, data evaluation and a systematic interpretation of the data. The influence of the ionic radius of the diffusing species and the lattice type of the host material used as matrix or target on the diffusion will be evaluated from these systematics. Special attention was directed to the release of group I, II and III-elements. Arrhenius plots lead to activation energies of the diffusion process. Results:1. 2.A strong radius determined diffusion behaviour was found: Rare earth elements diffuse as Me3+-species.Within the host elements of one period of the periodic table the diffusion of the DVIB'3. In a given target trace elements of group I and II of a lower period diffuse faster than the corresponding elements of the higher period of the periodic table. 132nd period > DSth period > 136th period (DBe >> DSr > DBa)• The diffusion determined transport rate of nuclear reaction products in solid target materials is often satisfactory, and consequently several refractory metals are suited as targets for fast on-line separation of short lived nuclear reaction products. The delay times measured in on line mode at ISOLDE, however, are significantly shorter. An enhancement of the diffusion under radiation condition is considered, subject for further systematic studies. The results obtained in this systematic study may also be applied in the development of alternative separation technologies in medical radionuclide production.

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SummaryThe partial alpha emitting lanthanide isotopeThe excitation functions for light- and heavy ion induced reactions have been calculated using the ALICE91 code. The direct nuclear reactionThe lower cross section of the spallation process can be compensated by using very thick targets. On-line mass separation technique provides high purity isotopically clean

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