Mechanistic dry-pressure-containment LOCA analysis

Procedures for performing mechanistic dry-pressure-containment LOCA analyses are presented, evaluated, applied, and compared with other approaches. The procedures are based on (1) the blowdown-introduced small drops (10 to 100 μm) being homogeneously mixed into the atmosphere, (2) drop (particle) turbulent deposition on vertical surfaces, and (3) terminal velocity gravity deposity on the floor. Variation of drop size and mass transfer deposition velocity was found to have a small effect on calculated results, except for the atmospheree water mass retention. The primary effect of the mechanistic approach was a saturated containment atmosphere, with significant atmospherewater retention. The calculated containment pressure of the mechanistic approach was lower, before the spray initiation, than that calculated by other current procedures