Abstract
During a nuclear power plant severe accident, discharging gas mixture into the spent-fuel pool is an alternative containment depressurization measurement through which radioactive aerosols can be scrubbed. However, it is necessary to develop a code for analyzing the decontamination factor of aerosol pool scrubbing. This article has established the analysis model considering key aerosol pool scrubbing mechanisms and introduced the Akita bubble size relationship. In addition, a code for evaluating the decontamination factor of aerosol pool scrubbing was established. The Advanced Containment Experiment and Light Water Reactor Advanced Containment Experiment were simulated with the code considering different bubble sizes of the Akita model and MELCOR default value to verify the suitability of the Akita bubble size model for simulating aerosol pool scrubbing. Furthermore, the simulation results were compared with the results analyzed by MELCOR code and COCOSYS code from literature, and equivalent predictive ability was observed. In addition, a sensitivity analysis on bubble size was conducted, and the contribution of different behaviors and mechanisms has been discussed. Finally, the bubble breakup equation was revised and verified with the conditions of the multi-hole bubbler in the Advanced Containment Experiment and Light Water Reactor Advanced Containment Experiment.
Highlights
Aerosol pool scrubbing is a specific phenomenon wherein aerosol particles carried by mixing gas are transported into the pool; thereafter, the gas condenses and cools, depositing the aerosol particles in the pool
The main thermal-hydraulic characteristics of aerosol pool scrubbing have been theoretically modeled in detail, including steam condensation, inertial impaction, gravitational, centrifugal, and diffusional deposition within the injection zone, gravitational deposition, centrifugal capture, Brownian diffusion, bubble breakup and resistance due to the steam flow within the rise zone, and bubble size in the rising zone
The Advanced Containment Experiment (ACE) and LACE experiments were simulated with the code, considering different bubble size values of the Akita bubble size model and MELCOR default bubble diameter value
Summary
Aerosol pool scrubbing is a specific phenomenon wherein aerosol particles carried by mixing gas are transported into the pool; thereafter, the gas condenses and cools, depositing the aerosol particles in the pool. The temperature, pressure of the pool, and the volumetric flow of the injected gas under three LACE-Espana experimental conditions were similar; the average bubble diameter estimated by the Akita relational equation was approximately 0.482 cm (dB-A), which was less than the recommended value of MELCOR (0.7 cm, dB-M). The results of their application to pool scrubbing calculation correspond to DF-A and DF-M, respectively. It proves that the modification of the bubble breakup equation is beneficial to improve the simulation precision about the aerosol pool scrubbing decontamination factor in the case of the multi-hole bubbler
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