Following the Fukushima-Daiichi nuclear accident in March 2011, innovations are needed to improve the reliability of new generation nuclear power plants toward scenarios where electrical power and ultimate heat sink are lost. This paper describes an integral design and basic passive safety strategy of a Small Modular Reactor (SMR) submerged in the sea or in an artificial lake, then performing a preliminary analysis of the long-term decay heat removal. The analysis considers a pressurized reactor placed in a horizontal cylindrical hull, which is surrounded by the external water. The simulated system is based on the Flexblue concept, developed by French company DCNS (now Naval Group). The object of the investigation is the natural circulation in the submerged containment, which is the key component for the long-term cooling. Following a rupture in the primary circuit, decay heat must be removed according to a fully passive safety strategy for an indefinitely long period. The purpose of this work is to study the effectiveness of a sump natural circulation flow to cool the fuel rods, up to several days after the scram. Decay heat generates steam in the core, which is released in the containment and condensed on the metal surface, transferring the heat to the exterior. Relap5-Mod3.3 has been employed to simulate the accident scenario. Results show the consistency of the safety principles and stimulate experimental investigations. However, the sensitivity analysis identifies the nodalization of the reactor containment as a modeling and numerical issue, deserving further analyses.

Long-term decay heat removal in a submerged SMR

marco santinello;marco ricotti
2019-01-01

Abstract

Following the Fukushima-Daiichi nuclear accident in March 2011, innovations are needed to improve the reliability of new generation nuclear power plants toward scenarios where electrical power and ultimate heat sink are lost. This paper describes an integral design and basic passive safety strategy of a Small Modular Reactor (SMR) submerged in the sea or in an artificial lake, then performing a preliminary analysis of the long-term decay heat removal. The analysis considers a pressurized reactor placed in a horizontal cylindrical hull, which is surrounded by the external water. The simulated system is based on the Flexblue concept, developed by French company DCNS (now Naval Group). The object of the investigation is the natural circulation in the submerged containment, which is the key component for the long-term cooling. Following a rupture in the primary circuit, decay heat must be removed according to a fully passive safety strategy for an indefinitely long period. The purpose of this work is to study the effectiveness of a sump natural circulation flow to cool the fuel rods, up to several days after the scram. Decay heat generates steam in the core, which is released in the containment and condensed on the metal surface, transferring the heat to the exterior. Relap5-Mod3.3 has been employed to simulate the accident scenario. Results show the consistency of the safety principles and stimulate experimental investigations. However, the sensitivity analysis identifies the nodalization of the reactor containment as a modeling and numerical issue, deserving further analyses.
2019
SMR; Passive safety; Submerged reactor; Long-term cooling
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1121675
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