Abstract: A communication network for nuclear plant protection systems includes monitoring and control channels, including a first pair of channels having first and second channels, the first pair of channels communicating through fiber optic data paths with a second pair of channels having third and fourth channels; a plurality of engineered safety feature trains, including first and second trains, the first train communicating directly with the first pair of channels and the second train, the second train communicating directly with the second pair of channels and the first train; a first vital power bus powering the first channel; a second vital power bus powering the second channel, and redundantly powering the first train and first vital power bus; a third vital power bus powering the third channel; and a fourth vital power bus powering the fourth channel, and redundantly powering the second train together with the third vital power bus.

Abstract: An interface between a Plant Protection System and Engineered Safety Features in a nuclear power plant is disclosed for continuously monitoring the plant protection system initiation circuit for each remotely actuated Engineered Safety Feature system to effect remedial action in the event that the Plant Protection System generates a ‘trip’ signal. By using actuation inputs from the Plant Protection System and manual, operator implemented inputs, controls are provided for remote equipment components, such as solenoid valves, motor operated valves, pumps, fans and dampers.

Abstract: An automatic self-testing system includes a plurality of sensor processing channels or paths each having a sensor for providing, either directly or indirectly, a digital value to a comparator which compares the measured value with predetermined value that is, in turn, provided to coincidence logic that evaluates the output of its comparator with the output of the comparators of the other paths to provide an output indicative of a pass/fail condition. Each sensor processing path includes two sub-paths that can be associated with or switched into the processing path while the disassociated sub-path undergoes off-line testing by a test processor. Testing is effected by providing a digital value to the sub-path under test while sensing the output to determine the functional validity of the sub-path under test. The combinational logic state of the system is monitored and converted into a decimal value that is compared with the set of decimal values corresponding to the finite known-good logic states of the system.

Abstract: To prevent damage to the electrical connections between PLC modules and a backplane during seismic and other vibrational disturbances, a bracket is used having two parallel side members attached to the backplane and a lower support bar connected between the side members to support the PLC modules in the vertical direction. An upper support bar may also be provided between the side plates to hold the PLC modules in the bracket and further prevent vertical movement. The upper and lower support bars may also provide vertical members or a rest in contact with the PLC modules and having a high coefficient of friction to prevent lateral movement of the PLC modules with respect to the backplane.

Abstract: A digital plant protection system for use in nuclear power plants of the pressurized water type includes cross-connected sensed-parameter processing channels that provide a suitably conditioned digital value to a digital comparator that tests the conditional digital value against a predetermined value to determine whether or not the sensed parameter has been exceeded. A comparator is associated with each of the plural channels and receives a separate measurement of the sensed parameter for each channel. If a sensed-parameter is determined to be out-of-specification by 2 of 4 or more channels, a `trip` signal is generated to effect remedial action.