<p>When pressurized water vapor leaks from a heat transfer tube of a steam generator (SG) of a sodium-cooled fast reactor, the vapor jet reacts with liquid sodium. This corrosive, high-temperature, and high-velocity jet may cause tube failure propagation. To evaluate the effects of sodium-water reaction phenomena is important for safety assessment of a SG. A numerical analysis code called LEAP-III was developed to simulate the event progress including sodium-water reaction. The LEAP-III offers the advantage in evaluating water leak rate caused by the tube failure propagation with low computational time; however, a current temperature distribution model in the LEAP-III provides an excessive conservativeness in some cases. In order to reduce this excess without significantly increasing computational time, we have developed an alternative evaluation model based on several engineering approaches with a Lagrangian particle method. This paper provides the newly developed evaluation model and its application to the gas flow with the chemical reaction in a tube bundle domain.&nbsp;<br>
Water vapor flow is represented as aggregation of particles which follow the Newton’s equation of motion, and liquid sodium is treated as background, that is, the equation of particle motion includes physical parameters of liquid sodium such as density, temperature, and velocity. A position and velocity of the gas-phase particles are updated from the equation of particle considering buoyancy and interphase interaction force. We also applied an elastic collision model to the particle-particle interaction, and a Lennard-Jones (L-J) model to particle-tube interaction. In the L-J model, a particle is attracted to the tubes until a distance between the particle and a tube becomes closer than a certain distance. On the other hand, repulsive force acts on the particle. This attractive and repulsive force makes the particle pass through between the tubes without calculating pressure. Temperature distribution is evaluated by considering heat of chemical reaction determined from the particle distribution.<br>
We performed test analysis using the current evaluation model. In this test analysis, gas-particles flow at 10 m/s from a leak point into the tube bundle domain which simulates a SG. Velocities of the particles converged to a terminal velocity due to interphase interaction and buoyancy force. The current model evaluated the temperature distribution which varied according to gas flow and chemical reaction. Through this test analysis, we confirmed that the Lagrangian particle model has a basic capability of simulating time development of the vapor jet in a SG.</p>

Numerical Evaluation of Sodium-Water Reaction Based on Engineering Approach With Particle Method

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.