Safety System Controls

The development of computer capabiUties in hardware and software, related instmmentation and control, and telecommunication technology represent an opportunity for improvement in safety (see COMPUTER TECHNOLOGY). Plant operators can be provided with a variety of user-friendly diagnostic aids to assist in plant operations and incipient failure detection. Communications can be more rapid and dependable. The safety control systems can be made even more rehable and maintenance-free. Moreover, passive safety features to provide emergency cooling for both the reactor system and the containment building are being developed. 

Emergency Shutdown System The safety control system that overrides the action of the basic control system and shuts down the process when predetermined conditions are violated. 

Arrangement of the semicommercial pilot plants permitted supervision and operation of the plant from a central control panel. The installed safety control system was tested successfully during several emergency shutdowns with no effect on reactor material and catalyst. 

A burner safety control system required to ensure proper operating sequences are employed. 

Safety checklists, 13 155 Safety control systems, nuclear power facility, 17 554... 

Topics Include methods lor calculating damage resulting from the physical effects of accidental releases, using risk assessment Information to specify safety control systems, fault tree analysis, hazards of trace substances, warehouse fires, human exposure to process systems, and solutions to human factor problems. 

As the European Union enlarges, it is essential that the ACC and NMS have implemented food safety control systems equivalent to those in place within the Community. This represents a significant challenge to those countries, in terms of ... 

Cables that must function as long as possible in safety control systems e.g., fire and gas detection systems, ventilation damper control and power systems, UPS, public address and communication systems, intrinsically safe systems. 

To understand the dynamic aspects of accidents, the process leading to the loss can be viewed as an adaptive feedback function where the safety control system performance degrades over time as the system attempts to meet a complex set of goals and values. Adaptation is critical in understanding accidents, and the adaptive feedback mechanism inherent in the model allows a STAMP analysis to incorporate adaptation as a fundamental system property. 

The used approach for the Static Analysis of software used for the Independent Assessment of the Temelin Safety System Software was cost consuming. However it makes possible to discover software anomalies which could be not found in manual check. It results from experience, that this way of assessment software is suitable not only for safety control system analysis in nuclear power systems but for transport and aviation as well. 

Protection against disabling the primary safety control system shall be provided and operation of a backup safety control system shall be automatic in case of failure of the primary system. 

The type of accidents in which the Doppler effect plays a crucial role are those resulting from very high rates of reactivity increase, say l/sec or greater. Normal safety control systems are adequate to cope with accidents resulting from lesser rates of insertion. In the safety studies for the earlier small alloy fuel reactors, the main type of accident leading to the reactivity increase was core meltdown (8), which was in turn considered to result from either coolant failure or some less severe type of reactivity transient. In many of the large breeder reactor concepts of the future, the coolant has a positive void coefficient of reactivity (77, 12a) which could conceivably lead to an autocatalytic expulsion of the coolant and consequently high rates of reactivity increase. 

There must be two safety control systems One of the systems, depending on the nature of the accident. Is to provide the primary protection the other, then, will function as a backup. The safety control systems must meet the following requirements ... 

Both primary and backup system must have adequate strength to maintain the reactor subcrltical for all credible accidents at least until the reactor Is damaged beyond repair as a result of the causative accident. Beyond this point the Inserted safety control system or systems are required to maintain control only to the extent that the consequences of the incident are no worse than those which would resxilt from the causative accident alone. 

Before investing in a sophisticated safety control system, adopt an inherent safety philosophy [18] and in sequence consider... 

Are safety control systems tested at least aimually ... 

The safety philosophy requires that the primary safety control system has a response which is fast enough to limit any credible power excursion to one of a magnitude that no damage beyond mild fisel stressing will result. Since the magnitudes of the credible reactivity ramps in N Reactor are considerably smaller than in the older Hanford reactors, speed of control in H Reactor is not so severe a problem as it is in the present reactors, nevertheless, the scram... 

Mobility of international capital and foreign managerial structures has had a positive influence on a broader introduction of the occupational health and safety control systems. There are ever more frequent requirements within the supplier-customer relationship to present evidence of the safety control systems efficiency. 

Finally, as Rinard (1990) has poignantly noted, The regulatory control system affects the size of your pay-check the safety control system affects whether or not you will be around to collect it. ... 

Safety-relevant but not part of the Profisafe profile Safety I/O and the safety control systems... 

This standard is the first international standard that sets out a complete management procedure and design requirements for overall safety control systems. Hence it opens up the way for conformance to be enforced by legislation. 

Most significantly one of the most valuable assets of a process control system is its flexibility and ease of access for making changes. Operators may need to disable or bypass some portions of the control system at different times. This is exactly what we want to avoid in a safety control system. 

This table summarizes some of the differences between process control and safety control systems. 

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