Diffusion of uranium in molybdenum,niobium, zirconium,and titanium

The diffusion of uranium was studied in molybdenum, niobium, zirconium, and titanium. The diffusion coefficients were determined by measuring the over-all activity of the residue of the sample, using the a-radiation of uranium enriched with the U²³⁵ isotope to 90% at temperatures 1500 to 2000° C (molybdenum, niobium) and 915 to 1200° C (zirconium, titanium). The temperature dependence of the diffusion coefficients was given by the equationsD _Mo ^U=7.60.10³ exp (–76 400/RT) cm²/sec;D _Nb ^U=8.90.10^–2 exp (–76 800/RT) cm²/sec;D _Zr ^U=7.77,10^–5 exp (–25 800/RT) cm²/sec;D _Ti ^U=4.90. t0^–4 exp (–29 300/RT) cm²/sec.The considerable differences between the diffusion mobilities and activation energies of molybdenum and niobium on the one hand and zirconium and titanium on the other were probably due to the effects of lattice defects, for example, excess vacancies arising in zirconium and titanium during polymorphic transformations.Translated from Atomnaya Énergiya, Vol. 19, No. 6, pp. 521–523, December, 1965Report read by G. I. Budker at the International Conference on High-Energy Accelerators (Frascati, Italy).