Emergency containment systems

The fourth level of defense-in-depth is activated if all of the previous levels fail and radioactivity is released from the power-generating system. This level consists of containment systems and accident management processes that prevent the dissernination of radioactivity to the atmosphere even if it is released from the nuclear systems. The fifth level is the provision for emergency planning outside the plant boundary in the highly unlikely event that all of the first four levels of defense were to fad. 

Install automatic or manual activation of bottom discharge valve to drop batch into a dump tank with diluent, poison, or inhibitor, or to an emergency containment area (May not be effective for systems such as polymerization reactions where there is a significant increase in viscosity.)... 

The safety improvements use redundancy and diversity to prevent and mitigate lents. The safety injection system (SIS) and emergency feedwater system (EFWS) are dedicated four train systems. Containment spray and safety injection pumps take water from the in-containment water storage tank (IRWST), thus, eliminating the need to switch from an external source and provide a. semi-closed system with continuous recirculation. Emergency core coolant flows direc nto the... 

Grossel, S. S., Vn Overriew of Equipment for Containment and Disposal of Emergency Relief System Effluents, y(ntrnaZ Loss Prevention Process Industries, (3), 112-124, January 1990. 

Mitigating events or mitigating factors act to impede the accident sequence, resulting in less severe consequences. Examples include detection and activation of emergency shutdown systems, operator intervention, spill containment, equipment spacing, natural dispersion, and reducing the... 

Good housekeeping Keep toxicants and dusts contained. Use dikes around tanks and pumps. Provide water and steam connections for area washing. Provide lines for flushing and cleaning. Provide well-designed sewer system with emergency containment. 

Containment within the vessel for the credible worst-case scenario reducing the design requirements for the emergency relief system this step is frequently too expensive and impractical in a multipurpose facility. 

A chemical engineer may have a choice of inherent safety variables, such as quantity stored or process temperatures and pressures, or process safety measures such as emergency isolation valves or containment systems, all of which may greatly reduce the vulnerabilities or the consequences of intentional loss. These are in addition to traditional security measures, which may include physical security, background checks, administrative controls, access controls, or other protective measures. For a more complete discussion of the options, refer to the AIChE Center for Chemical Process Safety Guidelines for Analyzing and Managing the Security Vulnerabilities of Fixed Chemical Sites and other references.f... 

A transfer vessel is a device that receives the contents of another vessel for emergency or nonemergency purposes. It can be as simple as a vacuum truck or as complex as a hard-piped, dedicated system. For liquids, the system typically consists of a container or containment system located below the protected vessel where gravity will promote a rapid transfer. In the few instances where a transfer vessel is used with gases, it assists in the depressurization of a process. In other instances, it may consist of a spare vessel capable of accepting the contents of a nearby vessel (in case of fire or leak) so that the damaged vessel s entire contents are not destroyed or released (Lees, 1980). In this case, a pump may be used to make the transfer between vessels. 

Work unit plans should contain guidelines for assuring uniformity in the assessment of and reaction to unusual events. An effective approach is to develop an emergency classification system that includes criteria for classification and guidance for the appropriate... 

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