Trip signals

For both failure modes, terminations caused by conditions other than the DG and its immediate support systems were not counted. Conditions that invalidated tests or demands for this study Include any operating errors that would not have prevented the DG from being restarted and brought to load in a few minutes without corrective maintenance incorrect trip signals that would not have been operative in the emergency mode and minor water or oil lea)cs that would not have precluded operation of the DG in an emergency. 

Reactor trip signal reactor coolant pumps tripped 4,685... 

The generator switchgear is recommended to have two separate lockout relays. One will receive all the electrical protection relay trip signals, and denoted as 86-1. The other will receive a master trip signal (or several trip signals) from the turbine unit control panel, and denoted as 86-2. 

DVS rods fall-down due to trip signal by flowrate measurement when changing over one primary pump to pony motor primary sodium flowrate measurement design of the primary flowrate measurement... 

The outlet temperature monitoring of 84 core SA is done by means of thermocouples housed in Core Cover Plate Mechanism (CCPM). The fuel SA thermocouples are scanned by central data processing system (CDPS) to generate trip signals. The CCPM (Fig 12) is a 6 m... 

Control rod withdrawal occurs when rotation of a selected drive motor is commanded by the rod control instrumentation. Control rod insertion can occur either by actuation of the drive motor or as a gravity powered movement following receipt of a reactor trip signal. 

The gravity powered insertion of the control rods is accomplished by disconnecting power to the holding brakes of the CRD motors. This disconnect is part of the PPIS and operates upon various reactor trip signals. Opening... 

Undesirable rod motion can result from control system failure and can be either inward or outward. Inward motion is a plant availability problem, but is not a safety concern. The extreme case of undesirable inward motion is an inadvertent reactor trip. This event might be caused by a loss of power or erroneous trip signals. This event places the plant in a safe condition. 

Outward motion can be a more significant threat to equipment and people. The consequence of control system failures which cause rod withdrawal are limited by several system features. The first is the limit on rod withdrawal speed due to the maximum amount of power that can be delivered to the CRD motor. Second is the control circuitry which limits the number of control rods that may be withdrawn at any one time. Third is the alarm system which will inform the operator of the improper rod motion so that he may take corrective action. Finally, a reactor trip signal will cause rods to be inserted. 

The outlet temperature of 84 core SA is monitored by thermo couples which are housed in CCPM. The fuel SA thermo couple signals are scanned by computer to generate trip signals. 

At several stages in the events leading to the accident, the operators defeated a trip signal or other protection system because it seemed likely to interfere with the test. Eventually, a significant part of the system had been disabled. Similarly, the operator ran the control rods much further out from the core than his operating rules permitted. These actions... 

Electrically powered actuators have not historically been able to provide fail safe functionality. Today there are some smaller partial turn electric actuators that have a spring return in the event of total loss of power. While these have the ability to close without power, there is a significant addition of complication that impacts the reliability when compared to a simple spring return hydraulic or pneumatic actuator. A response to this has been the electro-hydrauUc actuator that permits the safety functionality of a hydraulic piston fail safe actuator. The electrical portion provides power to the hydraulic system and the loss of which may be treated as a trip signal in addition to the basic shutdown signal. 

The APS design includes an Alternate Reactor Trip Signal (ARTS) and Alternate Feedwater Actuation Signal (AFAS) that are separate and diverse from the PPS (CESSAR-DC, Section 7.7.1.1.11). The APS equipment provides diverse and independent mechanisms to reduce the possibility of an ATWS and to provide additional assurance that an ATWS event could be mitigated. 

The ARTS will initiate a reactor trip when pressurizer pressure exceeds a predetermined value (see CESSAR-DC, Table 7.7.1). Turbine trip signals can also initiate ARTS if the Reactor Power Cutback System is out of service. The ARTS turbine trip input is manually enabled from the main control panel. 

A momentary trip of any channel is annunciated and causes that channel to lock out until manually reset. Sufficient annunciation trip signals are used so that the operator can determine the particular sensor or sensors, which caused the channel trip. The computer also prints out the identificahon of sensors, which have caused scram and, if several variables are involved, it prints out the sequence of events in which they occurred. 

SDS2 utilizes liquid poison (absorber) injection into the moderator. Upon receipt of a reactor trip signal, fast-acting valves between a high-pressure helium tank and the poison tanks open to pressurize and inject the liquid poison into the moderator. Injection occurs from several perforated horizontal tubes in the calandria, through which gadolinium nitrate solution jets into the moderator. An earlier design, the 220-MWe Indian HWRs, employs a set of vertical empty tubes in the reactor core that can be filled with a liquid poison (lithium pentaborate solution). 

The reactor is shut down with various trip signals that are indicative of the abnormal transient status of reactor. To avoid false trip two or more independent detectors for trip signal are used. Typical trip signals used in PWR are... 

In case of BWR the following trip signals can shut down the reactor ... 

NUclear Instrumentation measures the levels the distribution and the rate of change of neutron flux density in the reactor. Monitoring data and safety circuit trip signals are provided as appropriate over the full range of neutron flux levels from those existing during sub-critical shutdown conditions to those characteristic of full production level operation. 

Reactor Protection System (RPS)-list of Deleted (unnecessary detailed information multiple data required) reactor trip signals parameters... 

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