Modelagem e análise termo-hidráulica do reator de pesquisa IEA-R1 utilizando o código RELAP

Abstract

This work will present the development of a thermal-hydraulic model using the RELAP code for the IEA-R1 reactor, encompassing the pool, reactor core, all primary circuit piping and valves, decay tank, two main circulation pumps, two heat exchangers, and the Emergency Cooling System. All the most important parts of the developed circuits will be described in detail, and several simulations will be presented to demonstrate the satisfactory operation of the produced model. The steady-state flow in the cooling channels of the fuel elements showed a difference of approximately 6.4% compared to experimental flow data, and the open channels between adjacent elements exhibited a stronger lateral inflow from the pool to the core in the lower region. A series of simulations was also conducted to show the temperature distribution along the core components, and the comparison between an average channel and a conservative channel demonstrated temperature increments ranging from 85.6% to 88.4%, close to the expected theoretical value of 84.4%. The heat exchanger models accurately reproduced temperature behavior for both countercurrent and parallel flows. Finally, a simulation of slow flow loss accident in the core faithfully depicted the event's phenomenology: temperature drop after circulation loss followed by the opening of the natural circulation valve and flow reversal in the reactor core. A comparison with experimental results showed temperature differences of 2.3°C for the fluid and up to 4°C for the cladding. In summary, the RELAP model developed for the IEA-R1 successfully replicated the main reactor systems and equipment, enabling simulations for systemic evaluations.