In 1961, large-size, smooth-bore, Zircaloy process tubes were installed in C-Reactor graphite channels that had been enlarged to 2.275 inches. These tubes were installed to provide a test and demonstration facility for the concept of overboring as a means of securing significant improvement in the production capability of the reactors, After two years of facility operation, it is now appropriate to consider the extent to which original objectives have been achieved, to re-examine the original objectives, and to consider the best future use of this unique facility. This report presents the general results of such a review and re-examination in more detail.

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Activities in a program to develop techniques in the use of pulsed neutron sources to measure shutdown parameters related to large thermal power reactors are reported. In the course of this program, a new theory was suggested and an experimental apparatus was designed and built. Experiments were carried out to test the new model. This present report contains additional data and information extracted from the experiments at PG&E Humboldt Bay Power Reactor at Eureka, California. During the last days of 1963 a number of control rod and fuel bundle worth measurements were made in the ESADA Vallecitos Experimental Superheat Reactor (EVESR) using the (k[beta]/[script l] technique. A description of the experiments is given in the text of the report and some results are reported. A computer program was written to perform the data analysis of the pulsed neutron experiments and the code is discussed in the Appendix.

Recent underground nuclear tests conducted by the U.S. Atomic Energy Commission have yielded data on the effects of contained nuclear explosions in four rock mediums: tuff, alluvium, rock salt, and granite. This report presents and compares data obtained primarily through exploratory mining and drilling into the postshot environment of 35 such events.

In any underground nuclear explosion, the shock front that propagates from the shot point carries with it energy from the explosion, and distributes this energy by doing work on the surrounding material. In the process, the material undergoes changes in both its physical and mechanical states. If enough energy is deposited in the material, it will vaporize or melt thus changing its physical state, or cause it to crush or crack. During the past few years, special computer codes have been developed for predicting the close-in phenomena of underground nuclear explosions using the laws of physics, and the knowledge of the properties of the materials in which the detonations occur. As a consequence, a better understanding of experimental observations and measurements has evolved.

The effects of explosion-induced ground motion must be evaluated in planning and executing any nuclear excavation project. For some projects ground use intensity may dictate the use of less-than-optimum yields to minimize damaging effects. In remote areas, weighing the alternatives of outright purchase of some property or use of smaller yields may be required. The cost of indemnifying owners against damage must be considered in any case. Discussions of the effects of ground motion on three broad types of facilities - engineered structures, residential buildings, and equipment required for the support of nuclear excavation operations - are presented. A method of predicting the response of single- and multi-storied buildings, the response spectrum technique, is discussed, with emphasis on the application of explosion-induced spectra.

In this study, a physical-numerical model is used to investigate processes important for cratering, or excavation, physics for high-explosive sources in desert alluvium. High explosives do not vaporize much of the geological environment surrounding the initial cavity containing the explosive. Thus, a relatively simple, and in some cases a well-known, equation of state exists for the high-explosive cavity gas for pressure greater than 1 atmosphere. However, nuclear explosives are known to vaporize a great deal of surrounding geological environment during the early part of cavity life history. This vaporized material is believed to condense late in the life history of the cavity, and prior to vent of the cavity gas to the atmosphere, such that the latent heat of condensation plays an important role in nuclear excavation. So far, no numerical-physical models of the response of a geologic environment to a nuclear explosive includes the effect of condensation on the hydrodynamics of late times. Thus, the calculation of the cavity pressure at late times including the effect of condensation is one of the current unsolved problems in the calculation of a crater formed by nuclear explosives. This study, then, develops a predictive, numerical-physical model for H.E. sources of the cavity …

The production of energy by nuclear reactions results in the production of radioactive nuclei. Therefore, in considering the possible utilization of nuclear explosives for peaceful purposes it is necessary to be able to predict the expected activities, their amounts, and dispositions. The amounts and kinds of radioactivities produced by detonation of a nuclear explosive are dependent upon the specific design of the explosive. The behavior and ultimate fate of the activities produced by the explosion depend on the composition of the medium in which the detonation occurs, the nature of the detonation, and the chemical species involved.

In November 1952 an event took place which was to have a profound effect on political alignments of the world. This event was the detonation of "Mike", the first large thermonuclear device. The political implications of this experiment overshadowed what has come to be a major advance in the development of scientific tools; the experimentally verified, extremely high thermal neutron flux observed in Mike. Subsequent to this observation, the Atomic Energy Commission established a study program to investigate this particular characteristic of nuclear devices. Under the program, Los Alamos Scientific Laboratory and Lawrence Radiation Laboratory, Livermore, have studied the mechanisms of high fluxes, capture systematics, general stability characteristics, and more specifically, nuclear design to accomplish this massive neutron irradiation. Utilization of these greatly increased fluxes can be expected to significantly advance understanding in many fields.