Abstract:
An improved control circuit that is structured to energize another device such as a squib. A first portion of the circuit includes a first transistor and is structured to discharge at a first rate a first portion of a charge stored by a capacitor. Another portion of the circuit includes a second transistor and is structured to discharge a second portion of the charge subsequent to the discharge of the first portion of the charge and at a second rate greater than the first rate.
Abstract:
A solid state reversing DC motor starter that is testable on-line and satisfies the requirements for nuclear safety grade equipment. The motor starter employs a bridge of solid state switches which connect the polarity of the motor winding to conform to the desired direction of travel. The reversing switch bridge is in series with the main switch that is coupled in parallel with a reduced current by-pass flow path.
Abstract:
The dynamic logic of each channel of a multichannel protection system for a nuclear power plant provides a trip logic path and a global bypass logic path by which pulse signals from a clock source may be transmitted to a dc-to-dc power converter which energizes the undervoltage coils for a pair of contactors in the reactor trip switchgear. Each of the logic paths is constructed of basic logic units which in turn, each include a toroidal core of rectangular hysteresis loop magnetic material having a control winding which must be energized by a dc current in order for pulses applied to an input winding to appear at an output winding. Blockage of pulses through any one of the serially connected basic logic units in a logic path terminates the flow of pulses to the converter through that logic path. The control windings of corresponding logic units of the trip logic path in each channel are energized by one of a set of redundant sensors which monitor one of a plurality of reactor trip parameters. Dynamic voting logic appropriate for existing conditions is implemented in part by microprocessors in each channel which gather status information from the other channels through isolated, fiber optic, multiplexed data links and provide the switching logic for alternate paths for energization of the individual basic logic unit control windings, so that for instance, coincidence of trip signals from corresponding sensors in at least two out of four unbypassed channels is required to trip the reactor switchgear. Local bypasses provide additional energization paths for the control windings of basic logic units associated with sensors which are out of service or being repaired. Pulses propagate through the basic logic units of the global bypass path when an entire channel is taken out of service for treating or maintenance. Interlocks between logic units in the trip logic and global bypass logic paths permit only one path to deliver pulses to the converter at any given instant.
Abstract:
A blocking device for preventing the actuation of an automatic depressurization system in a pressurized nuclear reactor system due to spurious signals resulting from a software failure. The blocking signal is removed when the coolant level within the core makeup tanks drop below a predetermined level.
Abstract:
A control system for a nuclear reactor is disclosed. A control rod strategy computer provides for dynamic control of core power distribution in both radial and axial directions and forms the basis for a partial trip capability. Several microprocessor-based computation centers are combined together in a data-sharing network which processors determine local power density, determine the instantaneous differential and integral reactivity worth of each group of control rods, determine and effectuate partial trip for immediate power reduction, determine and provide for uniform core burnup, and effectuate core reactivity changes by directing the movement of groups of four control rods from zero to one hundred percent of travel while minimizing power distribution factors throughout the core. The power control circuitry to move the groups of control rods are bus arranged such that the power circuitry is shared among the groups of control rods. In this manner, the power to the control rod drive mechanisms is controlled and bus arranged for distribution to these drive mechanisms. This arrangement allows separate housings or cabinets for each holding circuit for each group of control rods and one housing or cabinet for the moving circuit for all of the groups of control rods.
Abstract:
Each parameter of the processes of the nuclear reactor and of the components of a power supply which convert the thermal energy generated by the reactor into electrical power is monitored by a set of four like sensors. One each of the unlike sensors which monitor the different parameters is contained in a reactor-trip logic channel. Each such unlike sensor is referred to here as a "local sensor". Each channel is interlocked with the other three channels and receives the signals sensed by the other three sensors, herein called "remote sensors". Each channel also includes means for processing the signals from the local and remote sensors. The apparatus also includes means for tripping the reactor to deenergize or trip the control rod drive and insert the control rods fully into the core so that the reactor stops supplying power. The apparatus normally operates on a "two out of four" configuration. This assumes that all sensors are in normal operating condition. To achieve this purpose, eight circuit breakers are provided. Two breaker contactors are controlled by each channel. The control is through the undervoltage relays of the respective breakers. To trip the reactor, it is necessary that at least four breaker contactors be opened by operation of two channels.
Abstract:
A solid state reversing AC motor starter that employs a DC power source and a power bridge employing insulated gate bipolar transistors that provide an ungrounded three phase AC output. The AC output is connected to the power input of the motor starter, which requires simultaneous RUN and Directional Commands to initiate valve actuation.
Abstract:
A current limiting DC motor starter employing a closed loop current measurement to provide precise current control that adapts to changing motor conditions, integrated with a solid state reversing motor starter. The motor starter further includes a calibrated overcurrent indication and a control system interface that reduces the likelihood that cable faults and other single failures will cause spurious actuation of the motor.
Abstract:
Excessive swing of the feedwater in power supply apparatus on the occurrence of a transient is suppressed by injecting an anticipatory compensating signal into the control for the feedwater. Typical overshoot occurs on removal of a large part of the load, the steam flow is reduced so that the conventional control system reduces the flow of feedwater. At the same time there is a reduction of feedwater level in the steam generator because of the collapse of the bubbles under increased steam pressure. By the time the control responds to the drop in level, the apparatus has begun to stabilize so that there is overshoot. The anticipatory signal is derived from the boiling power which is a function of the nuclear power developed, the enthalpy of saturated water and the enthalpy of the feedwater injected into the steam generator. From the boiling power and the increment in steam pressure resulting from the transient are anticipatory increment of feedwater flow is derived. Thus increment is added to the other parameters controlling the feedwater.
Abstract:
A blocking device for preventing the actuation of an automatic depressurization system in a pressurized nuclear reactor system due to spurious signals resulting from a software failure. The blocking signal is removed when the coolant level within the core makeup tanks drop below a predetermined level.