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Latest News
First astatine-labeled compound shipped in the U.S.
The Department of Energy’s National Isotope Development Center (NIDC) on March 31 announced the successful long-distance shipment in the United States of a biologically active compound labeled with the medical radioisotope astatine-211 (At-211). Because previous shipments have included only the “bare” isotope, the NIDC has described the development as “unleashing medical innovation.”
Ashok Kumar, Feroz Ahmed, L. S. Kothari
Nuclear Science and Engineering | Volume 67 | Number 1 | July 1978 | Pages 120-129
Technical Note | doi.org/10.13182/NSE78-A27242
Articles are hosted by Taylor and Francis Online.
Using multigroup diffusion theory with energy-dependent boundary conditions, the propagation of thermal-neutron waves has been studied in finite assemblies of beryllium and beryllium oxide. At different frequencies, we have calculated α and ξ for the discrete (or pseudo-discrete) mode as well as effective values of α(z) and ξ(z) (which include the effect of the source and higher modes) at a distance, z, from the source plane. In the case of beryllium, the results are in agreement with experimental findings of Miles et al. As observed by Miles et al., we find oscillations in the calculated values of α(z) and ξ(z) in a certain distance range beyond a certain frequency, which decreases with the decrease of transverse size of the assembly. Furthermore, in conformity with the experimental results of Miles et al., we find that with a decrease in the transverse dimensions of the assembly, the oscillations become larger, until one goes to very small assemblies, where these oscillations tend to smooth out. In the case of beryllium oxide, since no agreed value of Debye temperature exists and since the energy distribution of source neutrons is not known, only a qualitative comparison with the experimental results of Ritchie and Whittlestone has been possible.