The accidental reduction of the mass flow rate through a channel of a RBMK type nuclear reactor is expected to determine, besides other effects, the failure of the pressure tube. Due to the steam exiting with high velocity from the crack on the pressure tube, strong static pressure gradients interest the fuel pins closest to the opening. As a result, a “suction effect” takes place which might be strong enough to break the fuel pins and to cause them to be entrained out of the pressure tube. After introducing some hypotheses about the parameters governing the steam flow throughout the tube and the geometry crack, a CFD model was developed aimed at estimating, to a first approximation, the hydrodynamic loads acting on the fuel pins, and assessing the influence of several geometric and physical parameters on the loads. In addition, a simplified structural model for the fuel pin was used in order to estimate a range of loads which are expected to cause the failure of the pin, and a comparison was made against the hydrodynamic loads obtained through the CFD model. The result is that if the crack is large enough the loads are sufficient to cause the fuel pin collapse.
Analysis of the hydrodynamic loads on RBMK fuel pins in the event of Pressure Tube Cracking
D'AURIA, FRANCESCO SAVERIO
2004-01-01
Abstract
The accidental reduction of the mass flow rate through a channel of a RBMK type nuclear reactor is expected to determine, besides other effects, the failure of the pressure tube. Due to the steam exiting with high velocity from the crack on the pressure tube, strong static pressure gradients interest the fuel pins closest to the opening. As a result, a “suction effect” takes place which might be strong enough to break the fuel pins and to cause them to be entrained out of the pressure tube. After introducing some hypotheses about the parameters governing the steam flow throughout the tube and the geometry crack, a CFD model was developed aimed at estimating, to a first approximation, the hydrodynamic loads acting on the fuel pins, and assessing the influence of several geometric and physical parameters on the loads. In addition, a simplified structural model for the fuel pin was used in order to estimate a range of loads which are expected to cause the failure of the pin, and a comparison was made against the hydrodynamic loads obtained through the CFD model. The result is that if the crack is large enough the loads are sufficient to cause the fuel pin collapse.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
