Conservative analytical and experimental investigation of all pumps failure event in the primary cooling system for a 5 MWth research reactor

Abstract

The 5-MWth Jordanian Nuclear Research Reactor is an open-tank and open-pool research reactor which uses narrow rectangular fuel. The reactor is cooled by demineralized water in downward forced flow and natural circulation in transient events. The reactor performed a loss of flow test in the Primary Cooling System (PCS) by turning off all PCS pumps at full-power operation. The reactor then displayed safe behavior in thermal-hydraulic, neutronics, and acceptable radiological values. Besides, the RELAP5 MOD3.3 code was used to implement the reactor in three different comprehensive models according to several safety analysis conservatisms, such as assuming a lower total core flow rate by −12% or assuming failure in a safety valve. After that, a benchmark was conducted between the experimental results, and the code calculations of implemented models showed well agreement in general thermal-hydraulic and safety analysis parameters. The code proved a safe reactor trend that used all conservative assumptions even in the most conservative implemented model. The primary safety parameters, the Maximum Temperature of Fuel Clad (MTFC) and the Minimum Critical Heat Flux Ratio (MCHFR), were 421 K and 1.82 for a short time, respectively. The resulting parameters underwent the event's acceptance criteria, where the limits of the set values are 673 K and 1.5 for MTFC and MCHFR, respectively. As a result of the study, several models illustrated differences in thermodynamic parameter effects and gave higher and additional reactor safety levels. Moreover, the test comprehensively investigated the reactor behaviors and ensured the reactor cooling system capability by free convection cooling during the event.