Abstract
The accidents in the nuclear power plants of Three Mile Island and Fukushima Daiichi have clearly shown that the monitoring of the coolant level and the core state would have been highly advantageous. In the Three Mile Island accident the decreasing coolant level could have been detected early, which would have prevented the meltdown. Even during the meltdown, knowledge about the core state would have mitigated the risk of a steam explosion. In the Fukushima accident the monitoring of the reactor pressure vessel inventory could have detected the states of the reactor, resulting in a better foundation for extenuating emergency measures as well as ongoing and future clean-up operations. In line with the cooperative project "Non-invasive Condition Monitoring of Nuclear Reactors for the Detection of Level Change and Deformation of the Core" between the Technical University Dresden and the Institute of Process Technology, Process Automation and Measurement Technology (IPM) of the University of Applied Sciences Zittau/Goerlitz, an innovative core state diagnosis system for detection of the coolant level and the state of the core during severe accidents in PWR is going to be developed. The operational principle of this system is based on the measurement of the continuously changing gamma radiations (caused by the shifting of melted materials and fission products) at the outside of the reactor pressure vessel by means of several gamma radiation detectors. The detectors are arranged over the height of the core and the lower head. By using computer based and real-time capable methods for evaluating the measured gamma radiations conclusions about the core state can subsequently be drawn. This paper deals with the description of the functionality of the innovative core state diagnosis system for PWR as well as the validation methodology. For the validation of the core state diagnosis system an experimental rig will be used. The description of the experimental rig is a further main part of this paper.
