The search for baseline events for assessing the safety of nuclear refueling operations at nuclear power plants

The relevance of the topic of the safety of nuclear refueling operations is associated with the specificity of exploitation of RBMK units. One of the most hazardous, from the perspective of accidents at modern nuclear power plants, is the process of nuclear fuel reloading. The operations on rearrangement of fuel cartridges entail the risk of fuel damage, and thus, the likelihood of the release of radioactive substances exceeding the permissible limits. The process of reloading RBMK, if the reactor is at full capacity, consists of the vast number of complex operations characterized by a range parameters. Non-observance of the criteria for carrying out operations, or if the parameter values exceed permissible limits, with high probability leads to an accident. This article explores the possibility of application of formalized approach towards determination of the baseline events that may cause accidents for the purpose of the development of essential protection instruments. The formal approach would allow detecting the excessiveness in protection instruments on the existing blocks, as well as revealing the accident situations that cannot be prevented using these protection instruments. The author formulated systemic approach towards comprehensive assessment of the accident rate of structurally complex systems. Adaptation of this method relative to REM allows systematizing the search for baseline vents that entail uncontrolled situations, as well as optimizing the protection instruments that would ultimately enhance reliability of the system, simplify the exploitation process, and reduce the time of operating cycle of the controller for processing of the protection.