Development of an Open Loop Test Facility for HWRR fuel assembly irradiation experiments in Tehran Research Reactor

Abstract Test of nuclear material and fuels under neutron irradiation is one of the major applications of research reactors. HWRR is a newly fabricated domestic rod-type fuel assembly that is planned to be tested in Tehran Research Reactor (TRR). This paper presents neutronic and thermal-hydraulic safety evaluation of HWRR irradiation in TRR core. The comparisons of neutronic safety parameters of TRR core before and after HWRR loading are also provided. CFD thermal-hydraulic analysis of HWRR cooling channel reveals the necessity of increasing the coolant flow rate to satisfy safety limits. In this regard, a special setup called Open Loop Test Facility (OLTF) is developed to make possible irradiation experiments under safe and controlled condition inside TRR core. The OLTF provides a solution to overcome the main challenge of irradiating rod-type fuels inside TRR core at high thermal powers and neutron fluxes by providing sufficient heat removal capacity. OLTF uses reactor pool water as coolant source and injects a controllable flow into HWRR loaded channel through a pipe which is connected to the desired position in the core grid plate. OLTF can control various process parameters of the fuel test experiment such as coolant velocity and flow rate and it also measures important parameters of under irradiation fuel including inlet pressure, pressure drop, coolant and clad temperatures of the test fuel. An experiment is performed to evaluate hydraulic influences of OLTF exploitation on TRR fuel assemblies flow and its results are presented.