MODELING OF THERMAL PROPERTIES OF SOLID TARGETS FOR CYCLOTRON PRODUCTION OF RADIOISOTOPES
by Žarko STEVANOVIĆ, Milan RAJČEVIĆ, Jožef J. ČOMOR

Abstract: Most of the radioisotopes produced by accelerators are obtained by irradiation of solid targets. The design of solid targets for routine production of radioisotopes relies on the thermal and radiation properties of the selected materials and on the applied geometry. The proper engineering design of a target can be done by simulating the behavior of the target during the irradiation. A numerical method for the prediction of the thermal properties of the solid target has been developed and presented. The approach presented in this paper is based on calculations without using the common practice of Prandtl and Nusselt empirical correlation. The fluid flow description in the boundary layer was refined in such a way, that the heat flux, exchanged between the solid and fluid, is obtained directly from Fourier law. The governing equations are based on the local thermodynamic equilibrium and conservation equation of mass, momentum and energy. In order to solve the set of governing equations, the finite-volume method is used. This procedure gives rapid answers whether the proposed geometry satisfies the design criteria. The method was tested on a three dimensional model of a real target using realistic models for the irradiation conditions.

Key words: thermal properties, conjugate heat transfer, production of radioisotopes, targetry, solid target design, numerical simulation

THE BUDAPEST RESEARCH REACTOR
LAST RECONSTRUCTION AND PRESENT USE
by István VIDOVSZKY

Abstract: The Budapest Research Reactor, the first nuclear facility of Hungary was put into operation in 1959. The reactor served as the basis for Hungary's nuclear programme, which started at that time. It played a significant role in the training of nuclear engineers as well. The reactor was first reconstructed and upgraded in 1966, and between 1986 and 1992 for the second time. Today isotope production, industrial applications and basic neutron physics research are the main components of the utilization of the almost lonely reactor in Central Europe.

Key words: research reactor, reactor reconstruction, production of radioactive isotopes, neutron radiography

ABSORBED DOSE RATE EFFECTS IN THE RESPONSE OF KODAK X-OMAT V RADIOGRAPHIC FILM
by Milan VUČKOVIĆ, Nikola MIKANOVIĆ, Bratoljub MILOSAVLJEVIĆ

Abstract: Kodak X-Omat V radiographic film and FWT-60 radiochromic film were used for mapping the radiation field of a Febetron pulsed electron accelerator. Prior to use both films were calibrated utilizing a ⁶⁰Co gamma ray source. A difference of four orders of magnitude in the dose readings between gamma rays and pulsed electrons was found. The phenomenon observed is attributed to solarization reversal effect rather than to the chemical dose rate effect.

Key words: dosimetry, radiographic and radiochromic films, gamma source, accelerated electrons