Systematic experimental investigation on pressure build-up characteristics of water-jet injection into a molten LBE pool

In the scenario of a steam generator tube rupture accident in a lead-cooled fast reactor, secondary circuit subcooled water under high pressure is injected into an ordinary-pressure primary vessel, where a molten lead-based alloy(typically pure lead or lead–bismuth eutectic(LBE)) is used as the coolant. To clarify the pressure build-up characteristics under water-jet injection, this study conducted several experiments by injecting pressurized water into a molten LBE pool at Sun Yat-sen University. To obtain a further understanding, several new experimental parameters were adopted, including the melt temperature, water subcooling, injection pressure, injection duration, and nozzle diameter. Through detailed analyses, it was found that the pressure and temperature during the water–melt interaction exhibited a consistent variation trend with our previous water-droplet injection mode LBE experiment. Similarly, the existence of a steam explosion was confirmed, which typically results in a much stronger pressure build-up. For the non-explosion cases, increasing the injection pressure, meltpool temperature, nozzle diameter, and water subcooling promoted pressure build-up in the melt pool. However, a limited enhancement effect was observed when increasing the injection duration, which may be owing to the continually rising pressure in the interaction vessel or the isolation effect of the generated steam cavity. Regardless of whether a steam explosion occurred, the calculated mechanical and kinetic energy conversion efficiencies of the melt were relatively small(not exceeding 4.1% and 0.7%, respectively). Moreover, the range of the conversion efficiency was similar to that of previous water-droplet experiments, although the upper limit of the jet mode was slightly lower.