The influence of coolant level height on dynamic properties of core barrel

From practice of nuclear reactor operations a few cases of large accidents are known. One of them is the accident on the Three Mile Island Unit 2 nuclear power plant. The recovery operations at TMI-2 are very difficult and costly. The insufficient knowledge of real coolant level height in the region of fuel assemblies was one of the causes of mentioned accident. This misunderstanding of factual real state inside the reactor lead to confused decisions. As a consequence of that the active zone was uncovered, stripped of coolant. According to our meaning the coolant level height in PW reactors under operation can be identified by means of the core barrel dynamic properties monitored through, e.g. neutron flux fluctuations. This paper is devoted to the analysis of the mentioned phenomena, i.e. to the evaluation of coolant level height in a reactor by the change of the dynamic behaviour of its core barrel. (orig.)