ASSESSING INFORMATION NEEDS AND INSTRUMENT AVAILABILITY FOR A PRESSURIZED-WATER REACTOR DURING SEVERE ACCIDENTS

A five-step methodology was developed to evaluate information needs fo r nuclear power plants under accident conditions and the availability of plant instrumentation during severe accidents. Step 1 examines the credible accidents and their relationships to plant safety functions. Step 2 determines the information that personnel involved in accident management will need to understand plant behavior. Step 3 determines t he capability of the instrumentation to function properly under severe accident conditions. Step 4 determines the conditions expected during the identified severe accidents. Step 5 compares the instrument capab ilities and severe accident conditions, to evaluate the availability o f the instrumentation to supply needed plant information. This methodo logy was applied to a pressurized water reactor with a large dry conta inment and the results are presented. A companion article describes ap plication of the methodology to a boiling water reactor with a Mark I containment.