Effect of inertial pressure on criticality excursion and radiolytic gas bubbles for fuel solution system

The prediction of criticality excursion in fuel solution system has a significant impact on criticality safety analysis. The behavior of radiolytic gas bubbles, which may be influenced by inertial pressure, is crucial for the progression of criticality excursions. A two-dimensional model is proposed to calculating the bubble growth in order to simulate power and pressure in fuel solution system. The model is verified with experiments conducted at the SILENE facility and the influence of inertial pressure on radiolytic gas bubbles is analyzed by comparing the calculation results with and without the consideration of pressure changes. The comparison results indicate that pressure initially slows down the rate of power decline, while it speeds up the rate of power decline in the later stage of power decrease. Neglecting the pressure change during fast pulse transients may leads to a significant underestimation of the energy in the first burst. However, as the maximum inverse period of those experiments decreases, this underestimation becomes less significant and may even be overestimated slightly in turn.