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

Abstract: In the scenario of a steam generator tube rupture (SGTR) accident in a lead-cooled fast reactor (LFR), 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 buildup. For the non-explosion cases, increasing the injection
pressure, melt-pool 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.