Electrical power failure

Low-loss system. In a low-loss system the winding also resides in a reservoir of liquid helium but a very efficient insulation system enables the magnet to operate for long periods, typically I year or more, between liquid helium refills. An important feature of these systems is that they are relatively immune to short-term electrical power failures, which has enabled complete reliability even in extremely difficult environments. 

Valve Failure Positions In the event of instrument air or electrical power failure, valves either Fail Closed (FC), Fail Open (FO), or Fail in the last position (FL). The position of failure must be carefully selected so as to bring the system to, or leave the system in a safe operating state. 

Step 6. Acceleration calculations should be made to determine the effects of electrical power failure. Overspeeding of the train can be destructive if controls are inadequate to limit the peak speed within reasonable bounds. 

Normal Individual and Process Unit Basis for PR Sizing Considerations -The following single contingencies should be considered as the normal basis for evaluating overpressure that can result from electric power failures ... 

A standard UPS battery system is capable of running the cooler, allowing us to prepare unexpected electric power failure or to carry the system to a place without power supply. 

Electricity is so prevalent in modern society that an electrical power failure, such as the blackout in the northeastern part of the United States and parts of Canada on August 14, 2003, causes a major inconvenience. People rely on electricity to heat and light their homes, to operate many different kinds of appliances and motors, and to run subways, commuter trains and similar transportation systems. There is also a great deal of reliance on batteries, which store electricity and allow the portability of small devices that would otherwise require the use of wires to carry the required current from a generator. 

An actuator fault can be generated by a malfunction of the cooling system, such as electric-power failures, pomp failures, valves failures, and leaking pipes. Without loss of generality, actuator faults may be modeled as an unknown additive term affecting the state equation in (6.5), due to unexpected variations of the input u with respect to its nominal value, i.e., the value computed by the reactor control system. 

Type of power or prime mover available or allowable (see item 3 above). Plant steam balance should be considered. Is there need for emergency standby equipment of special type, with special drives in ease of electric-power failure ... 

Physical independence does not always equate to statistical independence. Although P-101 A and P-lOlB are physically independent of one another, they are not completely statistically independent of one another due to common cause effects such as electric power failure (if power fails, then the electrically driven pump will stop and the steam-driven pump will also stop also because the loss of electricity leads to a shutdown of the boilers that generate steam). 

In conventional fault tree analysis, one of the biggest benefits of the technique is that it highlights common cause events, i.e., those events that occur in two or more places on the tree and thus bypass safeguards. A common example would be electrical power failure. Loss of power could cause equipment to fail and could also lead to failure of some of the backup systems. 

Once more, the overall system failure rate appears not to have changed. Figure 15.25 does not present an accurate picture, however, because the Electrical Power Failure occurs twice, once to do with P-IOIA and once to do with P-IOIB. Hence it is a common cause effect Failure of Electricity leads to an immediate failure of the pumping system, so the fault tree should have the... 

Now comes the earthquake it knocks out electrical power. Hence all three of the operating pumps fail due to the first common cause Electrical Power Failure caused by the earthquake. This is bad, but the backup pumps, which together have a probability of failure of 1 in a 1000, can be trusted to work since they have their own, independent source of power (diesel). But, 40 minutes later, the tsunami disables the backup pumps due to a second common cause sea water flooding. The reactor core continues to generate substantial amounts of heat, but there are no means of removing that heat. 

Air. This tends to be less cool than all sources of cooling water and, because of low air-side heat transfer coefficients, needs finned tubes. The fins are hard to keep clean in areas where the air is dirty or is liable to contain (seasonally) large numbers of insects. On the other hand in the event of an electric power failure stopping the cooling air fans, natural convection through the banks of warm finned tubes can provide up to a quarter of the full condensing capacity subject to temperature. 

Abnormal shutdown Abnormal shutdown circumstances are those where the reactor is scrammed down After the cause of the shutdown has been determined and the reactor is Judged to be safe, then the shutdown caxi be considered normal For example, if the reactor was scrammed due to an electrics, power failure, the abnormal shutdown would last until BPA power was restored and primary pumping equipment returned to operation ... 

Detection of either punqping or electric power failure is accomplished through relaying located in the I90 Buildings. 

There are five levels of control to enable the manipulator to be used in a wide range of circumstances and be safely withdrawn from the reactor even in the event of complete electrical power failure ... 

The No. 3 Safety Circuit Is actuated If a process water pressure decay rate Is sustetlned which Is significantly greater than the pressure decay rate dxlch occurs following electrical power failure In the Primary Coolant System. 

Electrical power failure results In Insertion of the Vertical Safety Rods... 

A prolonged electrical power failure to the dissolver and loop pump could iallow the concentration of uranium in the stagnant dissolver to build to 610 g U(52.6)Aiter. Transfer of 610 g U(52.6) to the surge tank followed by dilution indicates a maximum k ff of 0.90 would be obtained for the most reactive concentration in the surge tank, 240 g U/liter with 2.6 g Gd/liter present. 

The ball safety channels provide a completely Independent nuclear control system to back-up the shutdown function of the horizontal rods. The control elements for this system are 3/8 Inch diameter ceramic balls containing neutron absorbers. Ball hoppers are embedded In the top biological shield over each of the IO8 vertical channels. The hopper gates, designed to open In case of an electric power failure, as well as upon appropriate safety-circuit signal, allow the balls to enter the channels by gravity. 

Electric power Is required to keep the safety balls and control rods out of the reactor. Upon electric power failure the safety balls would fall into the reactor by gravity, and the rods would be driven into the the reactor by compressed nitrogen. 

In the event of an electrical power failure, the vertical safety rods will fall because of the force of gravity. Where is the energy to insert the horizontal rods stored ... 

Some communities have created a system under which home care patients are transferred to local hospitals in anticipation of an electric power failure or flood disaster. Local fire departments will also assist in the event of a power failure or need for evacuation. Some electric power companies will arrange power generators available for 24-hour ventilator users in case of an electrical failure. 

The most serious problem is loss of fuel oil circulation in case of an electrical power failure. The fuel oil can then solidify in the circulating... 

Incidentally, this is a true story. Can you imagine what would have happened if all six pumps failed simultaneously due to an electric power failure The result would be a dramatic lesson in the meaning of water hammer. 

But it is important to watch for common causes of seemingly independent events. For example, electrical power failure could cause both low flow out of a vessel and an uncontrolled chemical reaction. 

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