Enhancement of the SPARC90 code to pool scrubbing events under jet injection regime

Abstract

[EN] Submerged gaseous jets may have an outstanding relevance in many industrial processes and may be of particular significance in severe nuclear accident scenarios, like in the Fukushima accident. Even though pool scrubbing has been traditionally associated with low injection velocities, there are a number of potential scenarios in which fission product trapping in aqueous ponds might also occur under jet injection regime (like SGTR meltdown sequences in PWRs and SBO ones in BWRs).

The SPARC90 code was developed to determine the fission product trapping in pools during severe accidents. The code assumes that carrier gas arrives at the water ponds at low or moderate velocities and it forms a big bubble that eventually detaches from the injection pipe. However, particle laden gases may enter the water at very high velocities resulting in a submerged gas jet instead.

This work presents the fundamentals, major hypotheses and changes introduced into the code in order to estimate particle removal during gas injection in pools under the jet regime (SPARC90-Jet). A simplified and reliable approach to submerged jet hydrodynamics has been implemented on the basis of updated equations for jet hydrodynamics and aerosol removal, so that gas-liquid and droplet-particles interactions are described.

The code modifications have been validated as far as possible. However, no suitable hydrodynamic tests have been found in the literature, so that an indirect validation has been conducted through comparisons against data from pool scrubbing experiments. Besides, this validation has been forcefully limited since very few pool scrubbing tests are available in the jet injection regime (i.e., ACE, LACE, POSEIDON II and RCA). But nevertheless, a considerable improvement in the estimation of the Decontamination Factor (DF) has been reached, as well as it has been proven that sizes of aerosol particles and submergencies are factors of major influence, however there is still a long road ahead.

We have extended the SPARC90 capabilities to study jet discharge processes, then the new SPARC90-Jet version is able to study globular and jet discharge processes, i.e. pool discharges under low and high velocity conditions. Therefore, the work here presented should be understood as a promising first step toward an effective code extension to the jet regime