Engineered safeguards systems

Engineered safeguards systems are integrated with the other main and auxiliary systems to protect the plant, its personnel, and the general public. After 2001, security systems were beefed up in the United States and elsewhere to meet the terrorist threat. These latter... 

Fig. Vll/1.0.1-1 shows various methods of risk reduction in a common figure to include all risk reduction methods. Here, SIS is of main concern to us, so it is shown separately (in dark box). SISs are one of the most commonly used, engineered safeguard systems offering good flexibility to the designers. On account of safety life cycle requirements of lEC 61508/61511, and for better SIS design, experts need to analyze the risk associated with process under control at the beginning. SISs are risk-based systems. When in the subject, it is better to address the first barrier, then to SIFs. Barrier functions are planned for prevention, regulation, and mitigation of undesired events. In safety barriers, such barrier functions are used to combat undesired events. A safety function could be a technical or organizational function, human action, or a combination of them, used to reduce risks. Therefore, safety functions are a type of barrier.

A large or sudden loss of primary coolant would result in a shutdown of the GTR and potentially activation of engineered safeguards systems. 

The containment spray system (CSS) (Figure 2.23) is an engineered safeguards designed to limit the peak pressure in the reactor containment building to a pressure less than the containment design pressure, in the event of a LOCA or a steam break accident inside the containment. The system also acts to remove airborne fission products (principally iodine) from the contaiiunent atmosphere should they be present due to a fuel cladding break. 

The separation of redundant equipment of the various systems that make up the ECCS is maintained to assure maximum operational availability. Electrical equipment and wiring for the engineered safeguard features of the ECCS are broken into segregated divisions, further assuring a high degree of redundancy. 

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. 

Engineered Safeguard Feature Actuation System (ESFAS)... 

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. 

Balducelli, C., Bologna, S., Lavalle, L. Vicoli, G. 2007. Safeguarding information intensive critical infrastructures against novel types of emerging failures. Reliability Engineering and System Safety, Vol.92, p.1218-1229. 

In both approaches - SMA and seismic PSA - the focus is on the plant-level robustness, i.e., it is essential that the safeguard systems of the plant be able to fulfill their safety function, even if individual equipment items may have failed. The analysis of the plant-level robustness takes into account the multiple lines of defense and the safety concepts - such as redundancy and diversity - implemented in the engineered safeguards. Ultimately, however, the plant-level robustness can be traced back to the seismic margin of individual systems, structures, and components (SSC). Hence, before discussing seismic robustness in terms of plant-level safety functions, the concept of seismic margin is introduced for individual SSC. 

Core spray and safety injection systems. .. might not function for several reasons in the event of an accident... Therefore, reliance cannot be placed on systems such as these as the sole engineered safeguards in the plant. Nevertheless, prevention of core melting after an unlikely loss of primary coolant would greatly reduce the exposure of the public. Thus, the inclusion of a reactor core fission product heat removal system as an engineered safeguard is usually essential. 

KTA-3501 Reactor Protection System and Monitoring of Engineered Safeguards. 

Records or describes engineering controls and safeguards at specific facilities Detection, fire suppression, and security systems containment and drainage systems and utility shutoffs. 

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. 

Personal protective equipment (PPE) is the term used for a variety of physical devices used to protect the body from hazards. Industrial hazards include impact, excess noise, heat, cold, and noxious chemicals of many different kinds and actions. The type of PPE we are concerned with here, of course, is equipment that can provide protection against hazardous chemicals. Protection may be required specifically for the face and eyes, skin, and the respiratory system, and each may need a different kind of safeguard. However, as previously stated, except in emergencies and special circumstances, PPE should not be relied on as the primary or sole approach to protection. Primary attack at the source by administrative and engineering means must always be considered paramount. 

The heater system was not engineered with the complement of flame management and tube protection safeguards recommended by insurance guides. 

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