Factors Affecting Loadbreak Elbow Connector Switching Speeds

A test program to assess the factors affecting loadbreak elbow switching speeds was initiated after several field failures suggested that inadequate switching speeds are increasingly common, especially with higher voltage elbows. It was found that tool type greatly affects switching speeds, that loadbreak elbow condition affects the range of speeds attained with any tool, and that lineman chacteristics only minimally influence speeds. To date, none of the above factors are included in the ANSI/IEEE-386 test Standard. The results of these tests underscore the importance of incorporating additional parameters into switching test clauses in future revisions of the Standard.     

Use of the Hot-Electron Mirror Machine Interem as a High-Z Ion Source

Production of the high-Z charge states in helium, nitrogen, and argon has been measured in the INTEREM device at the Oak Ridge National Laboratory. The INTEREM device contains a hot electron (~500 keV) plasma trapped in a minimum B geometry. The device is of interest because its parameters, electron density and energy, and ion lifetime are consistent with those required for the production of highly charged ions. Ion charge and ion energy spectra were measured independently using an einzel lens type energy analyzer combined with a quadrupole mass filter. For helium, most of the ions were doubly charged under proper operating conditions. For nitrogen, we found the ion yield to be peaked at Q = 4, and under these conditions the yield at Q = 6 was down by a factor of about 20. Energy distribution curves for different charge states show interesting features, from which important information may be inferred about the plasma in INTEREM. Although discrepancies exist in the ion yields we conclude that an INTEREM-like device employing a minimum B geometry and electron cyclotron resonance heating may be expected to be a good high-Z ion source.     

Studies on chicken actomyosin. I. Effect of storage on muscle enzymic and physico-chemical properties

Experiments were conducted to study the effect of storing broiler chicken muscle at 25°C on certain properties of actomyosin of the pectoralis major. Storage for 3 h or more resulted in the Mg²⁺-activated ATPase of actomyosin becoming less sensitive to inhibition by increasing concentrations of KCl and in an increased rate of superprecipitation of the complex. The analytical ultra-centrifuge pattern of the actomyosin of stored muscle differed from that of fresh muscle. Some evidence was obtained for the observed changes being partly dependent upon the pH of the muscle used as the source of actomyosin.     

The influence of iodine vapour on creep rupture properties of 20%Cr/25%Ni/Nb stabilised stainless steel

Interactions between volatile fission products, such as iodine, and fuel cladding have been observed in a number of reactor systems. To determine the effect of iodine on the mechanical properties of the 20Cr/25Ni/Nb steel used as fuel cladding in UK advanced gas-cooled reactors, stress rupture tests have been performed in environments of iodine vapour, air and vacuum under initial stresses of 47 to 130 MN/m² at 750° C. Iodine vapour promoted surface-nucleated, intergranular cracking which significantly reduced the specimen rupture life and strain at fracture compared with tests in air or vacuum. Increasing the iodine vapour pressure from 0.04 to 56 mbar resulted in further embrittlement. Examination of the surface regions of a specimen after long-term exposure to iodine vapour revealed a porous duplex surface scale and significant depletion of chromium from the metal associated with sub-surface void formation. Embrittlement mechanisms and some possible implications for fuel clad behaviour are discussed.     

Coolant cavitation in dynamic containment loading

After a brief introduction to the subject of cavitation in subcooled liquids and a survey of what is known regarding the key parameters in the cavitation process for water and for sodium, the basic equations of the SIMON cavitation model for use with Lagrangian containment codes and the assumptions behind them are reviewed.Some calculations using this model are then presented which show the dissipative effect of cavitation both in uncavitated liquids transmitting tension waves and in cavitated liquids transmitting pressure waves. The cavitation which develops when pressure waves are reflected at free surfaces is also examined, and some calculated results are compared with an experiment involving this phenomenon found in the literature. The role of cavitation in the containment loading process is then discussed, and examples taken from model test calculations are adduced to show that cavitation occurs at all stages of the loading process and involves a high proportion of the total liquid volume. Again by example the point is made that in certain simple circumstances a crude pressure cut-off model of cavitation is adequate but that for other major aspects of the containment loading process such as roof impact pressures and structural deformations a more refined model is necessary.