Measurements and analysis of transmitted spectra from LOTUS fission-suppressed hybrid blanket driven by D-T neutrons

The neutron spectra transmitted across a fission-suppressed hybrid blanket and its components, driven by a low intensity 14 MeV Haefely neutron generator, were measured with a 2×2 NE213 detector at LOTUS facility. These experiments have been analyzed with 2D and 3D codes DOT3.5 and MCNP, respectively. The spectral integrals between 15 to 1 MeV show good agreement among the 2D, the 3D, and the NE213 for 15 cm lead, 18 cm beryllium, and 25 cm graphite slabs. However, there are large discrepancies for 6.2 cm stainless steel and 15 cm lithium carbonate slabs. The assemblies involving two or more of these slabs reflect these tendencies. We observe also considerable disagreement over pointwise spectra for a number of assemblies.Work done while on visiting assignment to Institut de Génie Atomique, E.P.F.L.     

Distribution of the number of jobs in a GI/GI/1/∞ queue with a constant flow time constraint

We derive the Laplace transform of the joint distribution density of the number of jobs and of the vector of their flow time in a GI/GI/1/ queue with a constant constraint on job flow time.Translated from Kibernetika, No. 1, pp. 78–81, January–February, 1889.     

Martensitic transformation in alloys of the system TiNi-TiCu prepared by ultrarapid melt cooling

Conclusion In alloys of the TiNi-TiCu system prepared in the form of thin tapes by ultrarapid melt cooling the B2-phase, which is unstable towards martensitic transformation B2B19, contains up to 35% Cu, whereas in bulk alloys prepared in the form of an ingot cooled at normal rates it contains about 10% Cu close to the M_S. In alloys containing up to 35% Cu there are no untransformed brittle phases preventing development of martensitic transformation throughout the volume of the material. The structure of alloys is quite uniform, particularly those obtained by crystallizing from the amorphous condition, and the grain size of the high-temperature phase is a fraction of a micron. The fine structure of alloys close to a globular at a high cooling rate. Thus, range of practically important alloys of the B2 type with inelastic behavior effects, e.g., the shape memory effect, is considerably expanded.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 38–41, November, 1988.     

Inherent limitations in ectomography

Ectomography, a general tomographic method currently being implemented in nuclear medicine, is described. The object is viewed from different directions from the same projection angle, and the reconstruction process can be described as a two-dimensional filtered back-projection technique. One limitation of this limited-angle approach is that a three-dimensional Fourier representation of the acquired projections has a cone where data are missing. This empty cone can cause distortions in the tomogram by insufficient elimination of details outside the reconstructed tomographic section and by distortion of details in the section. The degree of distortion is dependent on the extension of the object in all directions and on the projection angle. Despite these limitations ectomography can be superior to single-photon-emission computed tomography for imaging sections that are close and parallel to the surface of the object, as in imaging of the hip joint or the heart.