Jet Scrubbing in Pools: New Research on a Key Source Term Issue

• Autores: Luis Enrique Herranz Puebla, Claudia López del Prá, Jaime Penalva
• Localización: Nuclear España: Revista de la Sociedad Nuclear española, ISSN 1137-2885, Nº. 396, 2018, págs. 78-81
• Idioma: inglés
• Enlaces
  • Texto completo (pdf)
• Resumen

  • The Fukushima accident occurred on March 11th 2011 stressed the need of providing Nuclear Power Plants (NPP) with technological safeguards capable of effectively mitigating severe accidents in case all the preventive measures have been unsuccessful. Pool scrubbing or wet scrubbing (i.e., the removal of contaminant particles and/or vapors carried by a gas when passing through an aqueous pond) is far from being restricted to nuclear BWR reactors, so that it is present in scenarios like meltdown SGTR sequences or gas bubbling over a water layer overlaying corium-concrete interaction in the ex-vessel phase of a severe accident. This generic nature has become even more true with the implementation of wet Filtered Containment Venting Systems (FCVS) in many NPPs worldwide.

    Pool scrubbing was heavily investigated in the 80’s and 90’s of last century.

    However, jet injection was hardly addressed at the time, most of tests being focused on what is called “globule regime” (Herranz et al., 2014). According to Zhao and Irons (1990), the transition from globule to jet regime occurs at values of the Weber non-dimensional number (We) higher than a threshold defined by, Wec (1) =10.5 ⋅ ρℓ ρg which for aqueous and carrier gases anticipated during a severe accident ranges in the interval 300 - 400. The significance of such regime is that gas-liquid interface phenomena change drastically and, as a consequence, the aerosol removal mechanisms also do: liquid drops are entrained in the gas bulk and sweep out a fraction of airborne particulate matter and fission product vapours. Even though recently some studies have analytically addressed these scenarios (Berna et al., 2016), the database to develop an empirical model and/or to validate any mechanistic or semi-mechanistic modelling is scarce and not fully representative.

    This paper summarizes the research carried out by CIEMAT within the PASSAM project (Albiol et al., 2017) on the scrubbing efficiency of pools when the particle carrier gas enters the liquid phase at high velocity forming a submerged jet (hereafter PSP test campaign). The experiments have been conducted in the PECA-PS facility of the Laboratory for Analysis of Safety Systems (LASS). A preliminary correlation encapsulating the observations into an empirical correlation has been intended on the bases of an extended database