During the past several years higher pile power levels, variations in the uranium goal exposure, changes in reactor loadings, and resulting changes in operating practices have steadily increased reactivity transients following the reacotr shutdowns and start-ups. Consequently, since conditions influencing activity transient predictions have becomeincreasingly more varied, it has become more difficult to maintain prediction accuracy Trends related to operating practices, reactivity variables, and critical predictions have been presented previously for the years 1950 thorugh 1957. It is the purpose of this report to include the data for the year 1958. In addition to presenting the data for reference purposes this document discusses the trends in operting pratices reactivity variable evaluations, and the accuracy of reactivity predictions during the past five years. Bar graphs show the yearly averages of selected data obtained from the shutdown data sheets, montly reports, and routinereactivity balance reports. In addition to these averages a table presents maximum and minimum values wherever they are applicable.

The question of the conditions under which living matter originated on the surface of the earth is still a subject limited largely to speculation. The speculation has a greater chance of approaching the truth insofar as it includes and is based upon the ever wider variety of established scientific fact. One of the purposes of the herein reported observation was to add another fact to the ever increasing information which might have any bearing upon this most interesting question. It is not our purpose in the present communication to discuss the various proposals or the arguments which have been adduced for and against them. One of the most popular current conceptions is that life originated in an organic milieu on the surface of the earth, (1,2,3,4,5). The problem to which we are addressed is the origin of that organic milieu in the absence of any life. It appeared to us that one source, if not the only source, of reduced carbon compounds in complex arrangements might be the interaction of various high energy radiations with aqueous solutions of inorganic materials, particularly carbon dioxide, and nitrogenous compounds such as ammonia and nitrogen, since it appears that these compounds were the commoner …

Dimensions for the circular fuel element which allow for thermal growth, swelling due to irradiation, and estimates for practical manufacturing tolerances are determined. (W.L.H.)

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A summary of operating experience and observations obtained during approximately 5OO hrs of running time on the PuP lead-bismuth forced circulation system is given. (auth)

Graphite was prepared by means of hydraulic extrusion, with densities as high as 1.90 gm/cc, in rods of up to 9/4-in. in diam. Densities higher than 1.90 gm/cc can be obtained by impregnating the graphite. It may be possible, by properly controlling the particle size distribution in the feed material, to achieve higher densities without impregnation. Variables studied included die temperature, mixing technique, binder material, baking procedures, some lubricants and additives, and preliminary work on the investigation of the effect of particle size. (auth)

This program, using the lBM 650 electronic data processing machine, is used primarily as a tool in order to prepare input data for an lBM 704 code ATBAC. The code calculates steady state thermal characteris tics of a plate type fuel element for both a nominal and adverse chanael. (auth)

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Uranium--niobium alloys were prepared by direct reduction with calcium of urardum tetrafluoride and niobium pentoxide. The reduction of potassium oxyfluoniobate did not give satisfactory results. Alloys containing up to 20% niobium have been successfully achieved. Ternary alloys containing chromium and vanadium have been prepared by simultaneous reduction of chromium anhydride and vanadium pentoxide. The preparation of the alloys is described and the results are discussed. (auth)

A proposal is given of an approach to a fission-product trapping system which appears feasible on the basis of thermodynamic and other data available. Reactor and trapping conditions are outlined. The half-lives, fission yields, and volatility of the fission products of interest are described. To provide the most effective retention at elevated temperatures, two types of reagents are required: a highly electropositive metal that will not melt or appreciably vaporize and which will form stable non-volatile compounds with non-metallic or near non-metallic fission products; and a reagent to provide a highly electronegative element to form stable, non-volatile compounds with metallic fission products. Thermodynamic properties are included for compounds formed by reactions between the fission products and the trapping reagents. (B.O.G.)

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