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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.”
J. B. Yasinsky
Nuclear Science and Engineering | Volume 29 | Number 3 | September 1967 | Pages 381-391
Technical Paper | doi.org/10.13182/NSE67-A17285
Articles are hosted by Taylor and Francis Online.
A variational principle, which has as its stationary conditions the direct and adjoint time-dependent group diffusion equations, is modified to admit time-discontinuous approximating functions. This extended principle is used to develop a synthesis approximation for the time-dependent group diffusion equations which permits the use of different sets of trial functions at different times during a transient analysis. The necessary equations are derived in detail, and two numerical examples are presented. These examples show that the time-discontinuous synthesis method is capable of constructing accurate space-time neutron fluxes, which vary smoothly in time, from spatial trial functions which are discontinuous in time. In addition, these examples display the potential of the new time synthesis for yielding computationally less expensive solutions than are possible with the time-continuous synthesis procedure.