Methodology of Nuclear Research Reactor Conversion at the Decommissioning Stage

The authors consider the creation of scientific and technical programs for conversion of nuclear research reactors at the decommissioning stage in terms of extending the designated service life of all operating nuclear research reactors (RRs) in Russia. To solve this problem, a methodology is proposed that includes an information model and a description of the necessary step-by-step actions, along with a set of appendices in the form of documents describing the best ways of creating a project for managing the quality of RR conversion in relation to special conditions of the life cycles of specific nuclear reactors. The methodology is described in the form of principles and means of construction and structure. An example of applying this methodology to the conversion of the Hydra salt solution pulse nuclear research reactor at the stage of decommissioning is presented. The reason for converting the Hydra reactor is to extend the designated service life by replacing nonrepairable equipment (the vessel). The main criteria for confirming the remaining service life of the vessel are formulated. They include the safety margin of the vessel’s material with allowance for the fluence accumulated on the more vulnerable areas and confirming the integrity and tightness of the vessel. For clarity, the conceptual information model of the methodology for confirming the safety of replacing the Hydra reactor vessel is given in the form of an Ishikawa diagram. The methodology consists of a number of consecutive scientific and technical activities, studies, and a finite number of actions in order to achieve the ultimate goal of extending the service life. The stages of the methodology for confirming the safety of replacing the Hydra reactor vessel are described. These include clarifying the initial data, performing computational studies and laboratory experiments, clarifying the requirements of methodological documentation, creating a working plan, and preparing license documents of operation.