Safeguards passive

Mitigation measures can also be passive safeguards, meaning that they require no human intervention and no engineered sensing and actuation system to work. Examples of passive mitigation measures are secondary containment systems, blast-resistant and fire-resistant structures, insulated or low-heat-capacity spill surfaces to reduce the rate of evaporation, and an increased distance between the hazardous materials and energies and the sensitive receptors. 

Passive Fire Protection (PFP)—barrier, coating, physical condition (i.e., spacing), or other safeguard that provides protection against the heat from a fire without the need for action to be taken. 

The inner mitochondrial membrane may function primarily as a calcium sink, taking up excess calcium in the cytosol that results from hormonal activation of the cell. At cytosolic Ca + concentrations greater than 0.6 /rmol/L, the mitochondrial calcium pump is activated and stores calcium in the mitochondrial matrix as a nonionic, rapidly exchangeable, phosphate salt. At low cytosolic calcium concentrations, the inner mitochondrial membrane allows Ca + to leak into the cytosol. The capacity of the active influx pathway (the pump) is much greater than that of the passive efflux route (the leak). The mitochondrial pump-leak system may serve to fine-tune the cytosolic calcium concentration while the plasma membrane is the principal safeguard against entry of toxic amounts of calcium into the cell. 

Active safeguards are those that require human procedures or mechanical initiation to operate (e.g., work permit procedures, scrubber caustic circulation). Passive safeguards are those that do not require any initiation (e.g., concrete fireproofing, elevated vent stack for dispersion). 

Both active and passive safeguards can be defeated through inadequate safety management systems. A safety management system is the most efficient way to... 

We may note in Table 1.4 that the vent gas scrubber was an active safeguard, while a passive type (as well as a change from active to passive of the other safeguards) would probably have avoided the accident, as discussed later. 

Stainless steel is attacked, but it is possible to use plant constructed out of stainless steel made with a high molybdenum content provided certain precautions are taken. One safeguard is to passify the surface at intervals by filling the machine with a nitric acid solution of 10 to 20 per cent concentration, and treating at 50° to 60°C (122° to 140°F) for about 30 minutes, or alternatively, the addition of 8 to 12 oz of sodium nitrate per 100 gallons to every bleach is effective. Stainless steel lasts quite well if a chlorite bleach is followed by a peroxide treatment since the latter assists in the maintenance of the passive surface. Polarization of the stainless steel has been pro-... 

Passive safeguards The berm can contain 110% of the tank s volume None... 

A passive safeguard controls a hazard simply through its presence such a safeguard does not have to do anything or to respond to unsafe conditions. An example of a passive safeguard is a tank berm. 

Another common example of a passive safeguard is a flare system. Any flammable vapors that are released from the process will be burned in the flame of the flare. 

An IPL is a safeguard that will prevent an unsafe scenario from progressing regardless of the initiating event or of the performance of another layer of protection IPLs can be either active or passive. AU IPLs are safeguards, but not all safeguards are IPLs. Examples of IPLs include ... 

Engineered safeguards are innovative and completely passive type... 

The primary philosophy is to follow the principles of inherent safety. This implies a systematic effort to apply the principles of hazard elimination, minimization/ intensification, hazard substitution, moderation/attenuation, and simplification. However, additional controls will still be required to control a hazardous situation, prevent escalation, and mitigate the risk to people, to the environment, asset, and reputation. Preferably, these safeguards will be passive- or active-engineered controls rather than administrative controls (i.e., dependent on direct human intervention). 

The characteristics in this group identify the systems used to maintain reactor core cooling if there is a loss of the normal reactor coolant. These systems usually include both active and passive systems (safety injection pumps and core flooding hydroaccumulators). Safety injection pumps should be considered as such pumps if they can be automatically started by an Engineered Safeguard Feature Actuation System (ESFAS) or a similar safety signal. 

The AP1000 PMS and passive safeguards systems are not dependent on offsite power or on any backup diesel generators. Following a loss of ac power, the protection and safety monitoring system and passive safeguards are able to perform the safety fimctions and there are no additional time delays for these functions to be completed. 

The small-break LOCA analyses performed show that the performance of the APIOOO plant design to small-break LOCA scenarios is excellent and that the passive safeguards systems in the APIOOO are sufficient to mitigate LOCAs. Specifically, it is concluded that ... 

Injection Ifom the core makeup tanks, accirmulators, and IRWST prevents excessive cladding heat up for small-break LOCAs analyzed, including double-ended ruptures in the passive safeguards system lines. The peak APIOOO heat flux during the accumulator injection period is below the predicted critical heat flux. 

Figure 1-2 shows the simplified schematic diagram of the SMART nuclear steam supply system (NSSS) and exhibits the safety systems and the primary system as well as auxiliary systems. The engineered safety systems designed to function passively on demand consist of a reactor shutdown system, passive residual heat removal system, emergency core cooling system, safeguard vessel and reactor overpressure protection system. 

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