Abstract

Calibration of the Control Rod (CR) is extremely important in compensating for the loss of reactivity and other reactivity-related parameters of the f Nigeria Research Reactor-1 (NIRR-1) Low Enriched Uranium (LEU) core. It is also important for the safe and stable operation of the reactor during and post-zero power critical experiments. The present work calibrated the entire length of the CR (0 – 230 mm) using the period method, at zero power, for the NIRR-1 LEU core. The integral worth for the entire length of the CR is found to be 6.49 mk. This is 0.51 mk (7.0 %) less than the 7.0 mk calculated worth by design. The maximum DRW was found to be 0.043 mk when the CR is midway out of the core. This implies that there is sufficient worth to shut down and operate the reactor safely but the reactor cannot operate at a maximum allowed excess reactivity of 4.0 mk in order to meet the allowed shutdown margin of ≥ 2.5 mk.

Key words: Control Rod,Nigeria Research Reactor-1, Low Enriched Uranium, Reactivity worth, Excess reactivity.