Design safety feature

Inherently design safety features at facilities provides for adequate spacing, arrangement and segregation of equipment from high hazard to low hazard. The least hazardous process systems should be used for obtaining the desired product or production objectives. Protective systems are provided to minimized the effects that may occur from a catastrophic incident. 

It is obvious that our on-road behavior is determined by both motivational factors - long-term and short-term - and information processing limits. Both models acknowledge the existence of the other factors, and therefore to truly understand behavior and design safety features we must consider both. 

See Design Safety Feature, Design Safety Measure,Design Safety Mechanism, and Hazard Countermeasure for additional information. 

See Design Safety Feature (DSF) and Safety Order of Preference (SOOP) for additional related information. 

Ibid. W. J. McCarthy, Jr., "Some Inherent and Design Safety Features of the ADPA Fast Breeder Reactor," n.d., ACRS File, AEC/NRC Alfred Amorosi, "Concept and Design," in Fermi-1, ed. Alexanderson, pp. 131-162. 

The manufacture of sealed sources, devices and radiation generators should also be subject to the requirements of quality management systems such as ISO 9001 [37-39]. Effective implementation of quality management procedures ensures that the designed safety features are consistently reproduced during production. 

Fig. 13. Proposed advanced PWR design having passive safety features (79). Courtesy of Westiaghouse Electric Corp.

The above are the more obvious constructional, design and safety features for a switchgear or a controlgear assembly. For more details and additional requirements refer to lEC 60439-1 for LT, lEC 60298 and lEC 60694 for FIT and ANSI-C-37/20C, common for LT and FIT switchgear and controlgear assemblies. 

An applicant for a construction permit files a Preliminary Safety Analysis Repori (PSAR) presenting design criteria and preliminary design information, hypothetical accident analyses, safety features, and site data. An Environmental Report (ER) must be submitted to evtiluatc the env ironmental impact of the proposed facility, and information must be submitted to the. Uornev Cieneral and the NRC staff for antitrust review. 

Another required safety feature on water heaters is a temperature and pressure relief valve. This is mounted near or on top of the tank. The temperature and pressure valves are designed to vent water if the temperature or pressure in the tank becomes too high. If there is no relief valve and the controls fail to limit water temperature, there is a danger of a powerful explosion from superheated, pressurized water flashing to steam as the water heater bursts. 

Any process which is a consequence of discrete tasks that have to follow a predefined sequence from raw materials to final products is a batch process. This predefined sequence is commonly known as a recipe. The primary features of any comprehensive recipe are the quantities of materials that have to be processed by individual tasks as well as the duration of each task within the recipe. The secondary features are the operating conditions of the various tasks, and in less common circumstances, the locality or geographic position of the task at hand. In processes wherein safety is of great concern, it might be necessary to perform a particular task in a designated area equipped with relevant safety features. 

An important safety feature is provided by the spring in an actuator. It can be designed to position a control valve in a safe position if a loss of supply air occurs. On a loss of supply air, the actuator in Figure 36 will fail open. This type of arrangement is referred to as "air-to-close, spring-to-open" or simply "fail-open." Some valves fail in the closed position. This type of actuator is referred to as "air-to-open, spring-to-close" or "fail-closed." This "fail-safe" concept is an important consideration in nuclear facility design. 

Operating with chemicals and pressurized containers always carries a certain risk, but the safety features and the precise reaction control of the commercially available microwave reactors protect the users from accidents, perhaps more so than with any classical heating source. The use of domestic microwave ovens in conjunction with flammable organic solvents is hazardous and must be strictly avoided as these instruments are not designed to withstand the resulting conditions when performing chemical transformations. 

When new plants are constructed or when modifications are needed in existing plants, detailed process designs are required. These designs must include special safety features to protect the system and operating personnel. The following case histories emphasize the importance of these special safety design features. 

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