Real Time Analyzer for Inverse Kinetics Rod Drop Experiments

A system is described that measures subcritical reactivity in nuclear reactors by the Inverse Kinetics Rod Drop (IKRD) technique. The analyzer was used in a large scale reactivity experiment performed in the Fast Flux Test Facility (FFTF) engineering mock-up core loaded in the ZPR-9 at Argonne National Laboratory. The hardware used in the system included (1) a computer operating in a real time environment, (2) an interface to condition the signals from seven neutron sensors located in the reactor core and to transfer them into the computer at fixed time intervals (provisions were made to interface signals from individual neutron detectors operating in either the current or the pulse mode of operation), and (3) a cassette tape recorder for permanent storage of the raw data. This system performs the following functions: (1) Examination of data from a Preselected neutron sensor during the steady state operation to determine when the transient (rod drop) begins, (2) Simultaneous acquisition and storage of data from all sensors once the test is in progress, (3) Solution of the inverse kinetics equation for each of the seven sensors in real time by the three point method, and (4) Display of significant results immediately after the conclusion of the test. The system allows the operator to determine the reactivity condition of the reactor immediately.