Design and validation of state based accident control instructions on a full scale simulator

The general state based approach to accident control procedures which EDF has been developing on a theoretical level since 1982 will be applied at pressurized water reactors from 1989 onwards. The objective of the original work being carried out is to design operating manuals (control instructions) which can be easily understood and applied by operators in the control room so that they can derive the maximum practical benefit from this approach. Tests on a simulator have shown that these instructions make it possible to control effectively not just all 'simple' accidents (primary or secondary breaks, steam generator pipe ruptures, etc.) but also any combination of accidents. About 80 different scenarios have been tested successfully, including more than 60 scenarios representing simultaneous or staggered multiple accidents or incidents. Operators have very quickly gained great confidence in these instructions, which appear to be simple and to provide a feeling of security, for two reasons: first, they always propose a solution, whatever the combination of equipment and/or human failures (utilization of substitution systems); and secondly, they make it easy to check at any time that the control sequence in progress is well suited to even the most complicated situation (utilization of periodic reorientation criteria). The positive results of the current tests mean that these new state-based instructions can already be regarded as a very powerful tool enabling operators to control the simplest to the most complex accident situations at PWRs. The state-based instructions will be introduced first at the Penly plant towards the end of 1989, then gradually at other PWRs in subsequent years. (author). 4 refs, 2 figs