26 Feb (NucNet): During the Fukushima-Daiichi accident in March 2011 the instrumentation provided for accident monitoring proved to be ineffective and existing strategies for accident monitoring, developed before the accident, need to be re-evaluated, the International Atomic Energy Agency says in a new publication.
The publication, ‘Accident Monitoring Systems for Nuclear Power Plants’, says accident monitoring instrumentation at Fukushima-Daiichi was ineffective for a combination of reasons that “appeared to include” a loss of power, evaporation of liquid in sense lines, failure of sensors due to environmental conditions, instrument ranges that were not suitable for monitoring plant conditions, and a lack of alternative data for use in validating instrument readings.
Lessons learned from the accident highlight the importance of accident management systems, including the availability of instrumentation systems that can monitor relevant plant parameters in the reactor and inside containment during and after a severe accident.
These parameters are needed to support “the execution of severe accident management guidelines to mitigate the consequences of such accidents and to disseminate information to external technical support staff”, the publication concludes.
Furthermore, parameters collected during severe accident conditions could allow experts to predict how an accident will evolve, and to implement and coordinate mitigation efforts and rescue actions.
Generally, existing accident monitoring systems were designed for design basis accidents, but not for “design extension conditions”. When designing accident monitoring instrumentation at new nuclear power plants, or when carrying out improvements to existing nuclear power plants, recent lessons need to be taken into account.
The publication says accident management strategies should consider the importance of monitoring spent fuel pools in addition to the reactor.
The publication provides an overview of instrumentation for monitoring accident conditions in land-based, stationary nuclear power plants designed for electricity generation or for other heat production applications.
Critical issues discussed include lessons learned from Fukushima-Daiichi; accident management and monitoring strategies; the selection of plant parameters for monitoring plant status; the establishment of performance, design, qualification, display and quality assurance criteria for designated accident monitoring instrumentation; and design and implementation considerations.
‘Accident Monitoring Systems for Nuclear Power Plants’ is online: http://bit.ly/1LGI2JE
