Dye-macromolecule complexes provide good models for the study of the effects of coupling between chromophores. In addition to modifications of the visible and UV absorption spectra of the dyes at small interchromophore distances, very efficient energy transfer has been demonstrated at longer distances. The probability of nonradiative transition increases with the number of excitation transfers so that an array of oscillators close to one another becomes nonfluorescent. The insertion of a dye molecule, acting as a trap for the excitation energy, in the highly ordered system of chromophores constituted by the purine and pyrimidine bases of native DNA has given results supporting the intercalation model of Lerman and providing an experimental approach to the problem of the path length of energy migration in the DNA molecule. The average excitation path length seems to be of the order of only ten base pairs, a result which can explain the lack of fluorescence of the DNA.

A half-plant low alum water treatment test began at F Reactor on January 16, 1963. The test, which had been prompted by the analysis of ledge corrosion attack on fuel elements, will demonstrate whether or not high alum feed is responsible for increasing the frequency of ledge and groove corrosion attack on fuel element surfaces. The effect will be evaluated by comparing visual examination results obtained from normal production fuel irradiated in process water treated with two different alum feed rates. Three 20 column fuel discharges, ten from each side of the reactor, have been taken during the test as follows: (1) One discharge prior to the start of the test. (2) One discharge such that the test side was exposed to coolant treated with both high and low alum feed. (3) One discharge under test conditions. This report presents the results from the second discharge under test conditions.

This summary on various flow induced vibration tests considers the four major types of tests which could accomplish, in part or in entirey, the experimental verification of design concepts for the support system for the NRX-A design.

All of the properties of plutonium hexfluoride reported up to May 1983 are summarized, andd pentinent data are presented in detail. Included are the preparation of plutonium hexafluoride, physical properties, absorption spectra, chemical reactions, decomposition of plutonium hexafluoride by radiation and heat, the corrosion of materials of construction by plutonium hexafluoride, and a summary of the biological and radiological hazards from plutonium hexafluoride. An expanded vapor pressure table is appended. 122 references are included. (auth)

The modular designs appear attractive in that the reactor core lateral support is provided by the modules themselves rather than externally as with a bundled core. Types B and C provide a means of reducing the inter-element and intermodular leakage flow. This tends to enhance the reliability of the reactor core by decreasing the probability of a progressive overall failure of the core initiated by a mid-core rupture of one of the fuel elements. The graphite inner reflector and lateral support mechnism are eliminated in this design. The assembly of the modular core design is probably simplified by the smaller number of modular elements to be handled and by the elimination of the lateral support mechanism. The modular core has several potential problem areas which will be examined by further analysis and testing.

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The components, operation, and performance of the beam extraction system are described, and the selection and proporties of particle orbits in the extraction channel are discussed. Single accelerated beam pulses were observed to last 37 nsec, and 40 mamp per pulse currents were measured in the extracted beam. The 45-Mev stacked beam was also extracted in a single turn from the 50- Mev electron accelerator. (D.C.W.)

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Results are reported for tensile and notched tensile tests on unirradiated and irradiated A-302B steel. The tensile results indicate that neutron irradiation decreases the uniform strain, increases the yield point, and decreases the strain hardening. The notched tensile results showed an increase in the ultimate tensile strength with irradiation. (D.L.C.)

Test results are presented that show that a strong concrete weighing approximately 185 lb/ft/sup 3/ can be made using water, waste lead slag, and Ciment Fondu. Feasibility, materials, mortar tests, concrete tests, and Ciment Fondu concretes are discussed. A 24-in.-thick concrete shield wall would have to be increased in thickness by 5 in. if slag concrete is used in place of barytes or magnetite concrete. On a pound-for-pound basis, the waste lead slag concrete materials were 30% cheaper than barytes and magnetite concrete materials. (M.C.G.)

Progress in various aspects of thermonuclear research is reported. Separate abstracts were prepared for ten of the twelve sections of the report. Design and engineering service notes and a report list are given in the remaining sections. (D.C.W.)

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An experimental determination of the reduced prompt neutron generation time LAMBDA / BETA in the Spert IV reactor utilizing a technique based on the statistical behavior of the neutron population is described. A mathematical model including the effects of delayed neutrons that relates the statistic variance-to-mean ratio of the count rate as a function of counting time'' to integral reactor parameters is derived. This model is used in conjunction with subcritical counting measurements from the Spert IV reactor to provide a value of LAMBDA / BETA that is in good agreement with an independent measurement obtained from super promptcritical excursion experiments. (auth)

Five melt refining demonstration experiments were conducted with highly irradiated EBR-II prototype fuel to verify earlier data on fission product removals obtained with unirradiated and lower-activity alloys. In each experiment, approximately 0.4 kg of uranium-fissium fuel pins irradiated to burnups ranging from 0.22 to 1.75 total atom percent was melt refined for 1 or 3 hr at 1400 C in a limestabilized zirconia crucible. The behavior of fission products was consistent with the earlier results. Fission product removals were over 99 per cent for krypton, xenon, iodine, cesium, barium, and strontium, over 95 percent for yttrium, rare earths, and tellurium, and zero for the noble metals. Because of the small scale of the experiments and necessary exposure of the irradiated fuel to air in the cave facility, it was not possible to obtain definitive data on product yields. Swelling of the fuel pins and the associated release of fission product gases during the heating cycle caused no difficulty in the melt refining process on this scale. (auth)

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This report covers the round-trip demonstration shipment of an instrtumented NRX-A reactor from Large, Pennsylvania, to Las Vegas, Nevada. The major goal of this demonstration was to gather data relative to shipping loads. In an overview sense, it can be said that the demonstration showed that transportation environment and maximum acceleration loads are well within the requirements established by the reactor design criteria.

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Measurements were made of radiation exposures to the hand and wrist from a 41-g Pu source. A plaster hand with film badges attached at several locations was used in the measurements. A ratio of 4: 1 in determining the exposure of hand and wrist by large radiation sources was estimated to allow for a safety factor of about 2. Small sources held directly on the hand resulted in a greater exposure. (C.H.)

A two-stage absolute counting facility for large liquid samples of aqueous Mn/sup 56/SO/sub 4/, primarily intended for better than 1% precision measurements of neutron source strengths by the manganese bath technique, is described. Two-liter samples are counted in a gamma - gamma coincidence arrangement that greatly improves long-term reproducibility at some sacrifice in counting statistics; this sacrifice is, however, lessened through a novel pulse- distribution scheme that allows fall utilization of the output of each detector channel. The system is calibrated on an absolute scale through another unit which counts aliquots of strongly activated samples mixed with liquid scintillator in a 4 pi BETA / gamma coincidence mode. The entire facility is designed to be readily adaptable to other radioisotope-counting requirements. (auth)