Total loss of power

Ride through — Measure of the ability of control devices to sustain operation when subjected to partial or total loss of power of a specified duration. 

Buono, S., Rubbia, C. (1996). Simulation of total loss of power accident in the energy amplifier. CERN/ET internal note 96-015,10 pp. 

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. 

A deficiency which could lead to a total loss of power or thrust due to common mode failure. 

Figure 4-8. Total loss of power supply to the pumps coast-down of the flow rate.

Sequence D This scenario assumes that the total loss of power occum simultaneously with failure of a target during processing, at the time that the inventory is most voiatiie. In this case, the contents of the SCB at the time of loss of power are 100% of the volatile inventory of the target. 

Total loss of power with primary feed and bleed, analysis of the optimnm B F configuration... 

There were 3 cases calculated using results of calculations of total loss of power. Primary B F was initiated at different core outlet temperatures (320°C, 500°C and 650°C). Results show that bleed and feed process was effective in all 3 cases. The overall conclusion that operator can wait until core outlet temperature begin to rise and primary B F should initiate at 300 mm in all SGs. 

Total loss of power, Allorsz/R06/A, KFKI-AEKI, Budapest, September/December 1998. 

Total loss of power, with cooling required for unlimited time, etc. 

Total loss of power supply (station blackout) - Emergency power supply (gas turbmes, battenes) (R) Adequate design and supply of/for magnetic beanngs at compressor and helium turbine (R)... 

Total loss of power supply (station black out)... 

Total loss of power supply Evacuation of water entered in the primary system by the water separator of the helium purification system (L)... 

Outage / -/, . Planned or accidental total loss of power in a localized area. A blackout is a wide-ranging outage. Minutes to a few days Catastrophic system failure, weather, small animals, human error (auto accidents, kites, etc.). System shutdowns. 

Three main safety concerns have to be considered in case of total loss of power ... 

For PWRs, practically, two systems of diesel generators are provided as emergency on-site power systems in addition to the external power system which is firmly connected to the power distribution grid. Therefore, a change of loss of power source is considered extremely limited even for a short duration. Even if total loss of power sources occurs for a short duration, the reactor could be brought to a safe shutdown through actuation of the safety protection systems and the control rod clusters. 

The decay heat and residual heat could be cooled for about 30 minutes through the natural circulation of primary coolant in the primary system, and through the operation of turbine operation auxiliary water supply pump and the main steam safety valve. Necessary power for the safety protection systems and the turbine-driven auxiliary feedwater systems is supplied from highly reliable batteries to secure the safety of reactor even during the total loss of power. 

For BWRs, the basic concept is almost the same as for PWRs. Reactor can be shutdown and cooled safely even after total loss of power sources for a short duration. 

The dissipation factor is the ratio of the parallel reactance to parallel resistance, i.e. the tangent of the loss angle (tan 8). The loss factor is the product of tan 8 and the dielectric constant and is a measure of the total loss of power occurring in the insulating material. Dissipation factors for most plastics tend to decrease with increasing frequency and... 

Since that time, NRC has been using risk assessment and directing the issuance of decisions on complex items associated with or related to safety, such as (a) total loss of power (station blackout) (b) Anticipated Transients Without reactor Shutdown (ATWS) (c) Pressurized Thermal Shock events (PTS) and (e) Maintenance Rule. 

Total loss of power. In the event of on-site total loss of power, aU of the pumps are stalled in the fuel, intermediate, and conversion circuits, and aU active systems connected to the power supply are assumed nonoperational. In this type of accident, the on-site security power supply is also considered deficient. 

The layout of the RCS should be such that, in the event of a total loss of power supplies to pumps in operational states as well as in specific design basis accident conditions, the removal of residual heat is ensured by the natural circulation of the reactor coolant. 

Total loss of power may not necessarily mean the total loss of steam. With loss of power, the boiler can still operate for some time at reduced capacity, and all the steam turbines can operate at reduce capacity. This impact needs to be considered carefully. 

For a cogeneration system, the total plant power may be available from generators powered by steam. In such a case, the total loss of steam will be equal to tire total loss of power. 

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