Alarm reduction in nuclear power plants: results of an international survey

Problems with industrial alarm systems are well documented and the implications of poor alarms and consequently inadequate operator responses are factors in many incidents in a wide variety of industries. It should be noted that if an alarm system is large, this is not in itself regarded as problematic, provided that the system is well engineered. In 1995, against this background, a group of UK companies involved in nuclear power generation commissioned Tekton Engineering to carry out research into the effectiveness and application of alarm reduction facilities in nuclear power-related facilities. The study revealed a wide range of approaches which embraced low-tech organisational solutions, such as engineering reviews and re-classification of existing alarms, but which extended to the provision of sophisticated logic processing schemes which take into account plant operating mode, plant item status, and in some cases, operator intent. A total of 53 alarm reduction techniques were identified. At the most fundamental level are those which affect the basic design of an alarm system, including alarm system philosophy, scope and coverage and choice of alarm conditions. Whilst many companies base alarm system design decisions on structured safety studies and HAZOPs, many systems are designed on a more ad hoc basis. Often alarm system design is left to the process computer supply contractor, who may not have sufficient operating knowledge to make appropriate decisions. Rarely are user performance criteria included in alarm system specifications. Many improvements can be achieved through organisation and specification work.