Instrumentation for experiments on a fuel element mock-up for the study of thermal hydraulics for loss of cooling or coolant scenarios in spent fuel pools

Beside the nuclear reactor and its primary circuit the spent fuel pool is yet another safety-critical part in a nuclear power plant which has gained increasing focus after the Fukushima accident. Loss of coolant or enduring loss of cooling conditions would ultimately result in loss of cladding integrity at elevated temperatures with excessive release of fission products and hydrogen. To predict the available response time and to assess the efficacy of mitigating measures computer simulations can be employed. Their validity, however, needs to be proven by dedicated experiments at small scale but relevant thermal hydraulic conditions. For that purpose, the test facility ALADIN was designed, which enables conduction of experiments on a single BWR fuel element mock-up under loss of coolant and loss of cooling accident conditions. In this paper we introduce the facility and its instrumentation, with a focus on temperature sensors and a new thermal anemometry grid sensor for flow velocity measurement in one quadrant of the rod bundle with a resolution of one point per subchannel together with the affiliated calibration procedure for a potential application in superheated steam and air in a wide range of fluid temperatures.