Abstract: 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.

Abstract: Proper functioning of a turbogenerator set depends on continuous functioning of the system of regulation and protection of valves of a steam turbine. Proper functioning of a turbogenerator set is important in the case of accident threat caused by the increase of turbine rotation speed over a particular value within the operational range with insensitivity maximum 0,5% of an average operational rotation frequency. The protection of a steam turbogenerator set is guaranteed by cut-out, control and back-flow valves. By a signal of a sensor element of protection, a turbogenerator can be stopped by closing cut-out valves of a high-pressure and an intermediate pressure cylinders or their control valves and a grid valve, or simultaneous closing of the above mentioned cut-out and control units. Such a system operates on the basis of an automated system used for support of the key regulated parameters of a turbogenerator in electric load and heat load modes. The authors of the article study electro-mechanical drive used for moving a riding cutoff valve in a turbogenerator control system. The authors describe the requirements to it. Based on dynamic characteristics of the electro-mechanical drive produced by the joint company “Diakont”, the authors construct a model of a control system, which guarantees the emergency shut-down mode operation. The protection control system structure guarantees the independence of its operation from the condition of a turbogenerator control system.