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The nature of two simultaneous processes is analyzed in detail. It is found that the experimental activation enthalpy increases with temperature for parallel processes and decreases with temperature for consecutive processes. Similarly the activation volume increases with pressure for consecutive processes and decreases with pressure for parallel processes. The creep rate stress exponent increases with stress for parallel processes and decreases with stress for consecutive processes. Each activation parameter is the weighted average of the corresponding ones for the individual processes. Several ways are indicated for the determination of individual activation parameters. The nature of three and four simultaneous processes is discussed briefly. When several processes are operating simultaneously, one of them may be rate controlling under certain conditions. This rate-controlling process may change with deformation parameters and a transition'' can be defined. The relation between transition parameters and the construction of deformation mechenism diagrams are also discussed. (auth)

From European conference on irradiation embrittlement and creep in fuel cladding and core components; London, UK (9 Nov Theoretical models for the deformation of metals subjected simultaneously to external loads and fast-neutron irradiation are discussed. The following models have been analyzed in detail: dislocation climb; climb controlled glide; and nucleation, growth, and unfaulting of dislocation loops. It is shown that the strains produced only by the climb of dislocations are equal to the isotropic swelling strains plus the thermal creep strains due to climb of dislocations. No irradiation-induced creep results from the climb of dislocations or growth of loops. The climb controlled glide of dislocations is a viable irradiation creep mechanism for low fluences at all temperatures or for all fluences at high temperatures. At low temperatures the hardening occurs by the elastic interaction of loops and dislocations. It is shown that the climb controlled glide of dislocations through the loop structure can explain the transient irradiation creep behavior. Steady-state creep, however, at low temperatures is explained by the stressaffected nucleation of dislocation loops. Comparison of the theoretical prediction with the experimental results suggests that stress not only influences the orientation of the loop nuclei but also enhances the interstitial …

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From 11th international symposium on free radicals; Berchtesgaden, F.R. Germany (4 Sep 1973). The results of a preliminary study of the interactions of positronium with nitrobenzene and ontho, meta, and para derivatives of nitrotoluene and dinitrobenzene in benzene solutions are reported. Distinct differences in the rate constants for the reaction of positronium with the organic molecules were observed for the various systems, and an attempt was made to correlate these changes to certain molecular parameters and to the effects of steric interactions in these molecules. (JFP)

From symposium on noble gases; Las Vegas, Nevada, USA (24 Sep 1973). Exposures of rats, mice, and hamsters for 90 hours per week to radon daughters nanging from 2000 to 8500 WL, with and without 18 mu g per liter uranium ore dust, caused marked lifeshortening in all three species. Marked reduction in body weights occurred in all three species, with weight losses of 30 to 50% of control animal values in all species after 31/2 months of exposures. Mice exposed to radon daughters and ore dust were particularly susceptible in terms of mortality, although the lungs of these animals showed very little pathological change. Classical radiation pneumonitis with alveolar septal fibrosis and occasional bronchiolar epithelial hyperplasia were the predominant deep lung lesions seen in all species. In contrast to hamsters exposed 30 hours per week to 1200 WL of radon daughters and uranium ore dust, proportionately more of the pathology was seen in the upper respiratory tracts of the hamsters in the present study. The contrast between markedly affected trachea and major bronchi vs. relatively little effects in deep lung was most evident in rats. Findings of severe suppurative laryngitis and bronchitis were frequent in rats, and may have …

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From thirteenth international congress of genetics; Berkeley, Ca1ifornia, USA (20 Aug 1973). The specific-locus method was used to investigate the effect of various biological and physical factors on radioinduced mutation frequency at a sample of seven gene loci of mice. The biological factors include sex, cell stage, and the interval between irradiation and fertilization. The physical factors include radiation dose, dose rate, dose fractionation, and radiation quality. It is suggested that the studies be extended to determine the effects of the various biological and physical factors on mutation frequency at low radiation dose rates in mouse spermatogonia and dictyate oocytes; investigations on the actual nature and effect of the individual mutations induced by radiation; and studies on the nature, extent, and persistence of the actual anatomical and physiologica1 damage expressed in the descendents of irradiated populations. (CH)

From effects of neutron irradiation upon cell function conference; Munich, F. R. Germany (22 Oct 1973). Improvements in neutron dosimetry and additional information about the effects of neutrons caused renewed interest in fast neutrons for cancer therapy. The availability of encapsulated /sup 252/Cf has introduced the need for data on the response of normal tissues that are at risk during an intracavitary exposure to a /sup 252/Cf implant. The anatomical characteristics of the Hanford Miniature Swine make them useful for studies to determine the short- and long-term effects of intracervically implanted /sup 226/ Ra or /sup 252/Cf. Capsules containing 50 mg Ra or 50 mu g Cf were inserted in the cervix with a tandem applicator by an after-loading technique. Therrmoluminescent dosimeters were attached to organs adjacent to the sources during laparotomy in some animals. The Ra pigs received a fractionated dose calculated as 7,000 to 14,000 rad at a point 2 cm lateral to the source. The Cf swine received between 2,000 and 6,000 rad. Pigs were either killed weekly to determine the early changes or brought to autopsy later because of delayed effects. Others are being killed from 1 to 3 yr after treatment for studies of long-terna …

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We consider whether the long term perturbation of radiocarbon dates, which is known to be approximately a sin function of period about 8000 years and amplitude of about 8% peak-to-peak, could have been caused in any major part by vulcanism. We conclude that this is not the case. On the contrary, present day volcanoes are a far less important source of inert CO{sub 2} (about 100 fold less) than is man's burning of fossil fuels which has caused the Suess dilution of about 2%. (auth)

From Winter meeting of American Society of Mechanical Engineers; Detroit, Michigan, USA (11 Nov 1973). The probability of failure corresponding to specified levels of allowable design stress was calculated for pressure vessels designed in accordance with the ASME Boiler and Pressure Vessel Code. The analysis was performed for maximum shear stress failure and for cyclic stress failure. The significance of such failure prediction is ddscussed and a rationale for selecting an allowable stress is presented. Examples are presented that demonstrate the estimation of vessel failure probability as a function of load variation, strength variation, and design safety factor. (auth)

From symposium on environmentl surveillance around nuclear installation; Warsaw, Poland (5 Nov 1973). A new concept in the sizing of radioactive or nonradioactive airborne Particulate matter has been assembled into a mobile field unit and is being applied to present environmental and health physics particle size information needs. The glow-discharge perturbat ion method economically generates particle size data which can be directly accumulated and spectrometrically analyzed by a multichannel analyzer. The basics of the glow- discharge technique are touched upon and compared to other instrumentation presently available in this province of the environmental sciences. The physical description, operational characteristics and current uses of the apparatus are detailed, along with importnt design and operational parameters. Particle size distribution data and analysis techniques illustrating the utility of this system are presented. (auth)

The history of radiocarbon dating from 1939 to the present is reviewed. The basic principles of radiocarbon dating are that cosmic rays make living things radioactive with {sup 14}C to a certain level fixed by the environment and that at death the intake of food stops so no replenishment of the {sup 14}C steadily lost by the immutable decay occurs. Therefore measurement of the degree of decay gives the time lapse since death, i.e., the radiocarbon age. The equipment developed and experiments performed to measure the specific activity of specimens to be dated are described. The results obtained by world-wide experimenters are discussed. These showed that on simultaneity radiocarbon dating is apparently reliable but that absolute dates may be incorrect by as much as 600 to 700 y. The value of radiocarbon dating to archaeologists, geologists, climatologists, and historians is stressed. (LCL)

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