Analytical and experimental investigations of the behavior of thermal neutrons in lattices of uranium metal rods in heavy water

Statement of responsibility on title-page reads: R. Simms, I. Kaplan, T. J. Thompson, D. D. Lanning"October 11, 1963.""NYO-10211."Also issued by the first author as a Ph. D. thesis, Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1964Includes bibliographical references (leaves 193-199)Measurements of the intracellular distribution of the activation of foils by neutrons were made in lattices of 1/4-inch diameter, 1.03% U-235, uranium rods moderated by heavy water, with bare and cadmium-covered foils of gold, depleted uranium, lutetium, europium and copper. The measurements were made in the M.I.T. Heavy Water Lattice Facility with source neutrons from the M.I.T. Reactor. Two lattices were studied in detail in this work. The more closely packed lattice had a triangular spacing of 1.25 inches, and the less closely packed lattice had a triangular spacing of 2.5 inches. The results of the experiments were compared to one-dimensional, 30-energy group, THERMOS calculations based on the available energy exchange kernels. The comparison indicated that the approximation that the hexagonal cell may be replaced by an equivalent circular cell (the Wigner-Seitz approximation) can lead to serious discrepancies in closely packed lattices moderated b! y heavy water.A modified one-dimensional, and a two-dimensional, calculation were shown to predict the intracellular activation distribution in the closely packed lattice. An analytical treatment of the problem of the flux perturbation in a foil was developed and compared to the experimental results obtained by using gold foils of four different thicknesses in the lattice cell; the method was shown to be adequate. An analytical method to treat the effect of leakage from an exponential assembly was formulated; the results indicated that only in small exponential assemblies would leakage be a significant problem in intracellular flux measurements. A method was developed to predict the cadmium ratio of the foils used in the lattice cell; comparison with available measurements with gold foils indicated good agreement between theory and experiment, except for a lattice having very large ratios of moderator volume, to fuel volume, e.g., 100:1.Calculations of the fuel disadvantage factor by the method of successive generations for gold, lutetium and europium detector foils were compared to the results of THERMOS calculations, because THERMOS was shown to predict the experimental distributions. The comparison indicated that the method of successive generations is a good alternative to the THERMOS calculation, if all that is required is 17 and the thermal utilization.U.S. Atomic Energy Commission contract AT(30-1)234

A Spectroscopic Reconnaissance of UV-Bright Stars

We have carried out spectroscopic observations and made preliminary classifications of 62 UV-bright stars identified by Lanning on plates taken by A. Sandage. The goal was to search for "interesting" objects, such as emission-line stars, hot sub-dwarfs, and high-gravity stars. Our targets were grouped into two samples, a bright, B < 13, sample of 35 stars observed with the Kitt Peak 2.1m telescope and a faint, 13< B < 16, sample of 27 stars observed with the Hobby-Eberly Telescope. We find 39% fairly normal O-mid B stars, 15% late ~B-late A stars and 32% F-G stars, with 13% of the stars being high gravity objects, composite, or otherwise peculiar. Included are four emission-line stars, three composite systems. Thus one out of every ten Lanning stars is "interesting" and may deserve individual study. Stars in the bright sample are often found to be late F or early G stars, although this sample does include interesting stars as well. No such large contamination occurs among the fainter stars, however, owing to "deselection" of these stars by interstellar reddening in the low-latitude fields of the survey.Comment: 9 pages in total, to appear in February 2002 issue of P.A.S.

Design innovation for the 1990's

Statement of responsibility on title-page reads: Richard K. Lester, Michael J. Driscoll, Michael W. Golay, David D. Lanning, Lawrence M. Lidsky, Norman C. Rasmussen and Neil E. Todreas"September 1983."Includes bibliographical reference

Demonstration of methods for analytical measurement of natural circulation flow in EBR-II

Statement of responsibility on title page reads: R. J. Witt and J. E. Meyer, Includes MIT technical contributions from J. I. Choi, D. D. Lanning, J. E. Meyer, A. L. Schor, R. J. Witt and R. D. Wittmeier.""February, 1986."Includes bibliographical references (leaf 44)Final project reportSupported by U.S. Dept. of Energy, Breeder Technology Program, Division of Educational Programs, Argonne National Laborator

Progress report no. 1

Statement of responsibility on title-page reads: Editors: I.A. Forbes, M.J. Driscoll, D.D. Lanning, I. Kaplan, N.C. Rasmussen; Contributors: S.A. Ali, S.T. Brewer, D.K. Choi, F.M. Clikeman, W.R. Corcoran, M.J. Driscoll, I.A. Forbes, C.W. Forsberg, S.L. Ho, C.S. Kang, I. Kaplan, J.L. Klucar, D.D. Lanning, T.C. Leung, E.L. McFarland P.G. Mertens, N.R. Ortiz, A. Pant, N.A. Passman, N.C. Rasmussen, M.K. Sheaffer, D.A. Shupe, G.E. Sullivan, A.T. Supple, J.W. Synan, C.P. Tzanos, W.J. Westlake"MIT-4105-3."Includes bibliographical referencesProgress report; June 30, 1970U.S. Atomic Energy Commission contracts: AT(30-1)410

The steady-state work density gradient: A new parameter and strategies for characterizing crack propagation in thin ductile sheets

This dissertation presents a new parameter for characterizing the crack growth resistance of thin ductile sheets: the steady-state work density gradient. The steady-state work density gradient describes the stress necessary to drive crack propagation in the late stages of mode I crack growth as the crack tip approaches a specimen edge and crack propagation is at steady-state. This parameter was discovered by comparison of different specimen types (edge notch and middle notch) cut from thin (25.4, 50.8, and 127 µm thick) annealed aluminum sheet specimens using plots of nominal stress vs. normalized crack length. The steady-state work density gradient may also be used in conjunction with digital image correlation and tracking (DICT)-based strain increment maps to spatially resolve the work density along contours of constant strain which run from the crack tip to the specimen boundaries. Thus, the spatial distribution of energy absorption around a steady-state crack tip may be experimentally measured, and the magnitude of energy absorbed can be compared between different specimens. This dissertation demonstrates the application of the steady-state work density gradient to thin sheet systems, including the aforementioned aluminum sheets, 120 nm thick gold sheets, thin tin sheets, and thin copper sheets. The dissertation also explores other fracture toughness approaches such as the linear-elastic K parameter, the elastic-plastic J concept, and essential work of fracture (EWF) to give context to the steady-state work density gradient and its applicability to a variety of thin ductile systems.Ph.D

Stopping Rules in Information Acquisition at Varying Probabilities andConsequences: an EEG Study

An experiment aiming to assess the use of stopping rules ininformation acquisition was performed. Participants wererequested to make a decision in 24 financial scenarios withthe possibility of buying information pieces. Behavioral andEEG data were recorded for analysis. Results showed thatparticipants followed Bayesian calculations in order todetermine a stop on information acquisition and decide.Moreover, the information acquisition strategies wereconsistent with prospect theory, in which participants willweigh information pieces differently and seek more or lessinformation given different manipulations in scenarioprobability and consequences. EEG data suggest SlowCortical Potentials at fronto-central electrodes