Logic Rating of Electromechanical Relays
Electromechanical relays were the first logic element used in a computer. Today, small compact reed relays are again being extensively used as logic elements. A logic factor, FL, measures the improvement that a logic device can affect if interposed between a logic source and logic detector. A logic figure of merit, TFM, determined when FL = 1.0 can be used for comparison of the logic performance of logic devices. TFM is developed for an arbitrary electromechanical relay. For a miniature reed relay packaged for printed circuit boards, TFM = 1.7 milliseconds. For comparison, solid-state devices have TFM ¿ 1 nanoseconds and COSMOS (complementary symmetry metal oxide semiconductor) devices have TFM ¿ 20 nanoseconds.
On measures of logic performance: logic quantum, factor, and figure of merit
A basic logic operation is considered of transferring a logic decision from one point to another point. A certain energy level, WL, corresponding to decision threshold and a time delay, TL, are encountered in the transfer process. The product, WLTL, is a logic quantum, HL. If the logic transfer takes place through an intermediate device, a logic factor, FL, can be introduced to describe the reduction in logic quanta that the device can produce under optimum conditions. Optimization is carried out, as for instance with ideal transformers, to "match" the logic source to the device and the device to the logic detector. The condition FL = 1 marks a boundary between a useful and a uselessd evice, and a logicf igure of merit, TPH,in units of time corresponds to the fastest source-detector combination such that FL = 1. Logic performance is considered in some detail for a particular linear model of a device. Nonlinear devices and relay devices are considered in less detail, although some numerical calculations are given for a current-switch, two-transistor computer device. The logic figure of merit represents a unique measure of high-speed logic performance and is therefore valuable in comparing devices including associated circuitry on a common basis.
Numerical tools applied to power reactor noise analysis
In order to be able to calculate the space- and frequency-dependent neutron noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor noise analysis are then described, including the unfolding of the parameters of the noise source from the induced neutron noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor noise analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.