Analyzing a Rod-Drop Experiment in the IRR-1 MTR Reactor with Substantial Corrections to the Point-Kinetics Equations

A control rod drop experiment, that was taken place in the Israeli pool-type MTR reactor IRR1, was analyzed using the inverse-kinetics method, and the measured reactivity drop was compared to calculated estimation using MCNP simulations.

It was found that in order to estimate accurately the reactivity drop from the experiment, corrections to the point-kinetics naive analysis of the measurement were needed. The corrections, namely the shape factor and the ratio between the static to dynamic reactivity, were calculated by additional MCNP simulations, using the fixed delayed source approximation. The corrections increased the measured value of the control rods by 30%, and after the correction, a very good agreement was found between the measured and calculated values of the control rods worth; with deviation of 5%, which is less than the estimated measurement uncertainty.