Dukovany NPP - reconstruction of the instrumentation and control system. Safety analyses. Rev. 1

The report contains a summary of analyses performed with a view to assessing the effect of reconstruction of the Dukovany instrumentation and control system on the plant's nuclear safety status. The system calculations were made by using the RELAP5/MOD3.1 and DYNAMIKA-UJV computer codes. The following initiation events were considered: Opening of all steam dump valves to the condenser; Steam line break beyond the hermetic compartment; Steam line break inside the hermetic compartment; Main steam header break; Uncontrolled closings of the fast-acting valve on one steam line; Loss of normal steam generator feedwater; Failure of 3 out of the 6 main coolant pumps; Closing of one main closing valve on one loop; Inadvertent closing of one safety valve at the pressurizer; Break of one steam generator pipe; Leaktightness failure of a steam generator cold header lid; Large, medium and small break LOCA. The results largely demonstrate a favourable effect of the instrumentation and control system upgrading. The safety criteria are invariably met. (author)