During some pressurized water reactor risk-dominant sequences, most of the radioactivity is discharged at very high velocities into nearly saturated pools. An experimental plan for pool scrubbing and its associated hydrodynamics under representative boundary conditions is carried out in the PECA facility. The retention tests show that a substantial fraction of particle absorption takes place at the pool entrance because of inertial removal mechanisms. This submergence-independent component of the decontamination factor (DF) becomes dominant for small submergences (S ≤ 1.25 m). The behavior of the gas at the pool entrance is investigated experimentally, and a close relation between primary bubble size and inlet gas flow is observed. In addition, the retention tests are modeled with the SPARC90 and BUSCA-AUG92 codes. SPARC90 shows fairly good agreement with the experimental data and indicates the importance of the entrance region in particle absorption. Nonetheless, the approximations and drawbacks of the aerosol removal models used in SPARC90 at the injection zone suggest the need for further separate-effects tests to validate, improve, and/or develop specific models for the entrance region and the need for additional hydrodynamic tests to better describe primary bubble behavior under a jet injection regime.
