Experimental study of voiding effects with thorium based MOX fuel cluster in Critical Facility

Abstract

An Advanced Heavy Water Reactor (AHWR) based on thorium fuel is being designed and developed in India. The design has many inherent safety features; the most important among them is its negative coolant void coefficient. An experimental facility, named AHWR Critical Facility, has been built to validate the physics design parameters. Coolant void worth which is an important safety parameter was measured using differential critical height in a thoria based experimental MOX fuel assembly placed in the center of the core. The voiding effects were experimentally determined with both water and high density polyethylene (HDP) coolant. Different fractional voids were obtained using combinations of HDP block of compatible shape and sizes.The aim of the experiment was to validate the code systems used in physics design and in particular, to assess their capability of modeling the voiding conditions in thorium based fuel cluster. The validation exercise was performed with both deterministic and stochastic methods. The theoretical estimates of the void worth were found in very good agreement with that of the measurement. The results have enhanced the confidence in the code system used for AHWR physics design.