Monitoring the Condition of Safety Barriers in Nuclear Power Plants

Abstract

The technical requirements of a system that continually monitors the condition of the safety barriers of nuclear power plants are substantiated. It is shown for the example of the Rostov NPP that power units with VVER which are operating, under construction, or in the design stage can be equipped with a measuring system for monitoring radiation leaks from the steam generators. This improves safety (by not allowing emergency situations) and increases the installed capacity utilization factor (by eliminating unjustifi ed shutdowns of power units) of operating power plants.When any physical safety barrier provided in the design of a nuclear plant is found to be unserviceable, the reactor must be shut down and measures taken to put the power-generating unit into a safe condition. This means that deeply echeloned protection must provide a system of technical means and methods for reliably monitoring the condition of the corresponding physical barriers of the nuclear power plant. The assessment of their integrity in operating power-generating units must be done by comparing the results and uncertainties of monitoring for confi dence probability P = 0.95 with the safety limits established for these barriers, viz., the operational limit and the safe operation limit [1][2][3][4]. Given the present status of nuclear power, it should be noted that as a general problem of operating nuclear power plants the operational limits and the safe operation limits, which were established during the early years of the operation of nuclear power plants, must be given scientifi c substantiation.An important requirement of radiological safety during the operation of nuclear power plants is the use of, together with laboratory methods of monitoring the integrity of the safety barriers, automatic means (systems) making it possible to continually track the dynamics of the temporal changes occurring in the quantities being monitored and to record the moment when the corresponding limits are reached, i.e., systems functioning in measurement and not indicator modes. On the basis of such results of the indicated monitoring operations, it is necessary to make timely and substantiated decisions concerning the degree to which a monitored object meets the regulatory standards [3]. In the general case, the object certainly meets the standards if [1-3] B * (1+U ) L ≤ 1,