Influence of control rod worth interactions on LMFBR control systems design

These design criteria are interpreted to define the reactivity worth requirements for the primary and secondary control systems in terms of the minimum control systems capability under faulted conditions which will assure that the reactor can be safely shut down. The faulted conditions are postulated to occur upon the simultaneous failure of one of the redundant safety control systems to scram, a stuck rod in the scramming system, and a reactivity insertion resulting from the uncontrolled withdrawal of the highest worth control rod inserted in the reactor. The resulting positive reactivity insertion from the rod runout envelopes other postulated operational faults and is imposed on the shutdown requirements of both the primary and secondary control systems. In order to determine the minimum shutdown capability, an evaluation is made of the worst combination of control rod runout (reactivity fault) and stuck rod worth