Emergency system failure

Example 11-2 assumes that all failures in either the alarm or the shutdown system are immediately obvious to the operator and are fixed in a negligible amount of time. Emergency alarms and shutdown systems are used only when a dangerous situation occurs. It is possible for the equipment to fail without the operator being aware of the situation. This is called an unrevealed failure. Without regular and reliable equipment testing, alarm and emergency systems can fail without notice. Failures that are immediately obvious are called revealed failures. 

All process components demonstrate unavailability as a result of a failure. For alarms and emergency systems it is unlikely that these systems will be unavailable when a dangerous process episode occurs. The danger results only when a process upset occurs and the emergency system is unavailable. This requires a coincidence of events. 

The electric back-up to this process is independent of that of the isolation system, the diesel generator is a different brand and capacity, therefore common cause failure will not be considered (Fullwood, 2000). The activation of the neutralisation process is carried out by the emergency system EAS-200, and leak detectors AI201 and AI202, as shown in Figure 4. 

In indications such as diseases of the central nervous system (CNS), the respiratory system, or the cardiovascular system, failure is often through the emergence of side effects. This is because the intended targets have other biological functions in other organ systems. The side effects come directly Irom the biology of the systems, they are mechanism-based. ... 

The vision of braking and steering by wire will demand new, extremely reliable sensors. Even in early implementations of steer-by-wire systems, in which manual control can override any system failure, more than one sensor is normally used for the sake of redundancy. Many of the sensor principles required are already established in the market, including steering-angle sensors (e.g., for vehicle dynamics control) and pedal-position sensors. Mechanical action or feedback control, however, will drive the emergence of torque and force sensors. 

Totally 104 failures have occurred over a total operation period. The abnormal operation events due to equipment and system failures resulted in 28 plant shutdowns of which 18 shutdowns involved reactor scrams (5 events involved manual reactor emergency shutdowns). In the remainder the plant power reductions took place. 

There are several types of emergencies. Some result from the forces of nature. Some involve fire and explosion. Some involve system failures. Some emergencies entail traffic or transportation problems. Some result from the behavior of people. For others, there are police, military, and public safety actions to assist people and protect property. 

There are many kinds of system failures that can create emergencies. For example, intermption of operations may create hazardous conditions. Boiler overheating can cause dangerous conditions requiring quick action. Failure of temperarnre limit controls can lead to runaway processes. Failure of pressure limit controls can lead to rupmre of pipes, gaskets, vessels, and other equipment. Sudden releases of steam, gas, fuel, or hazardous chemicals can create dangers... 

A failure of the grid and emergency power supply -with attendant safety system failure (ULOF). 

Emergency water injection system for reactor flooding under LOCAs is designed as active one because of certain size limitations in the FNPP. It includes 3 high pressure and 2 low pressure pumps Water recirculation system for long term decay heat removal is also provided It is essential that even in case of all emergency heat removal and water injection systems failure under LOCA the reactor core uncovery starts only after 3 hours of the accident initiation... 

Stop feed water at 100% power Scram + active trains of emergency heat removal systems failure NN VL... 

Scram + all trains ot emergency heat removal system failure Restoration of one heat removal train 4 -5 h... 

Beyond DBA (BDBA) and severe accidents can result from one of fhe initiating events as in case of DBA however combination of failure of ECCS system and emergency systems can lead to these events. Such accidents include those initiated by events, such as RPV rupture or a seismic event more severe than the safe shutdown earthquakes, that... 

This equation will formally have the form of a life function with constant failure rate. A5 can be viewed as the system failure rate in the case of a preset inspection interval. Such a view will of course make sense only when inspection intervals are small in comparison to the entire operation period to be considered. For the OR linkage, the following emerges from Equation (4-56) ... 

Accidents resulting from two simultaneous Independent system failures are considered credible accidents. For example a major primary loop rupture combined with failure of the emergency once-through cooling system to supply coolant Is the maxlmimi credible accident. 

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