Abstract
This work presents the thermal hydraulic simulation of the Brazilian multipurpose reactor (RMB) using a RELAP5/MOD3.3 model. Beyond steady state calculations, three transient cases of loss of flow accident (LOFA) in the primary cooling system have been simulated. The RELAP5 simulations demonstrate that after all initiating events, the reactor reaches a safe new steady state keeping the integrity and safety of the core. Moreover, a sensitivity study was performed to verify the nodalization behavior due to the variation of the thermal hydraulic channels in the reactor core. Transient calculations demonstrate that both nodalizations follow approximately the same behavior.
Highlights
The Brazilian Nuclear Energy Commission (Comissao Nacional de Energia Nuclear—CNEN) is leading the project of the Brazilian Multipurpose Reactor (RMB) envisaged to be projected, constructed, and operated to attend the present Brazilian need for a multipurpose neutron source, which will be able to supply the demand of radioisotopes, carry out material tests, and develop scientific, commercial, and medical applications with the use of neutron beams
In order to allow the establishment of natural circulation when the primary cooling system (PCS) pumps are not in operation three special flap valves are located in two lines returning to the pool, which are represented by component 360
To simulate the first shutdown system (FSS) action using the RELAP5, $10 of negative reactivity was inserted in 0.5 seconds of simulation time, when the mass flow in core inlet decreases below 50% of steady state value
Summary
The Brazilian Nuclear Energy Commission (Comissao Nacional de Energia Nuclear—CNEN) is leading the project of the Brazilian Multipurpose Reactor (RMB) envisaged to be projected, constructed, and operated to attend the present Brazilian need for a multipurpose neutron source, which will be able to supply the demand of radioisotopes, carry out material tests, and develop scientific, commercial, and medical applications with the use of neutron beams. Some authors consider the onset of significant void point as a conservative estimate of the onset of flow instability [16] Some of these criteria are widely used and some of them are implemented in computer codes such as RELAP5/Mod. The assessment and validation of thermal-hydraulic system code have been performed in order to investigate the applicability of RELAP5/Mod3.2 to evaluate safety margins of an MTR research reactor [17]. In group B, we can see the initiating event frequency (per year) relative to loss of flow accident, and as it can be observed there is probability of occurrence of this event in consequence of the primary pump failure (B3). According to OPAL safety analysis report (SAR), the probability of occurrence of a pump shaft seizure is considered to be very low due to the high quality of manufacture. This work focuses the investigation of the time evolution of the temperature in the core, cladding, and pool reactor after a LOFA transient and their consequences
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