The dependence of pool scrubbing decontamination factor on particle number density: modeling based on bubble mass and energy balances

ABSTRACT

Pool scrubbing is one of the promising means for mitigating radioactive aerosol release into the environment in nuclear severe accident scenarios. The influence of operational conditions on its performance is therefore of much interest. This paper focuses on the influence of particle number density found in our experiments. The experiments, conducted for insoluble monodispersed (0.5 µm) particles, indicated a sharp decrease in the decontamination factor (DF) for inlet number densities higher than ~1 × 10¹¹ m⁻³. A model is proposed based on a hypothesis that particle removal becomes inefficient at high number densities because particle condensational growth is limited by the depletion of vapor supersaturation in rising bubbles. The model calculates the magnitude of supersaturation from the bubble mass and energy balances considering the condensational vapor consumption and heat addition by all particles in the bubble, where the rate of condensation on each particle is dependent on supersaturation. The particle size, condensationally growing with time, is then used in the calculation of centrifugal particle removal. It is shown that the model reproduces qualitatively the experimental dependence of DF on particle number density, providing further proof that such dependence is a physical reality deserving attention in the evaluation of pool scrubbing performance.

KEYWORDS:

• Pool scrubbing
• condensation
• particle growth
• decontamination factor
• particle number density
• modeling

Nomenclature

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Acknowledgments

The experimental system was developed under the financial supports of the Nuclear Regulation Authority, Japan (NRA).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Nuclear Regulation Authority, Japan.