ARTIST: Introduction and First Results

Abstract

ARTIST (Aerosol Trapping In a Steam Generator) is a seven-phase international project (2003–2007) which investigates aerosol and droplet retention in a model steam generator under dry, wet and accident management conditions, respectively. The test section is comprised of a scaled steam generator tube bundle consisting of 270 tubes and 3 stages, one 1:1 separator unit, and one 1:1 dryer unit. As a prelude to the ARTIST project, four tests are conducted in the ARTIST bundle within the 5th EU FWP SGTR. These first tests address aerosol deposition phenomena on two different scales: near the tube break, where the gas velocities are sonic, and far away from the break, where the flow velocities are three orders of magnitude lower. With a dry bundle and the full flow representing the break stage conditions, there is strong evidence that the TiO2 aerosols used (AMMD 2–4 μm, 32 nm primary particles) disintegrate into much smaller particles because of the sonic conditions at the break, hence promoting particle escape from the secondary and lowering the overall DF, which is found to be between 2.5 and 3. With a dry bundle and a small flow reproducing the far-field velocities, the overall bundle DF is of the order of 5, implying a DF of about 1.9 per stage. Extrapolating the results of the dry tests, it turns out that for steam generators with 9 or more stages, it is expected that substantial DF’s could be achieved when the break is located near the tube sheet region. In addition, better decontamination is expected using more representative proxies of severe accident aerosols (sticky, multicomponent particles), a topic which is yet to be investigated. When the bundle is flooded, the DF is between 45 and 5740, depending on the mass flow rate, the steam content, and the water submergence. The presence of steam in the carrier gas and subsequent condensation inside the broken tube causes aerosol deposition and blockages near the break, leading to an increase in the primary pressure. This has implications for real plant conditions, as aerosol deposits inside the broken tube will cause more flow to be diverted to the intact tubes, with a corresponding reduction in the source term to the secondary.

Integral analyses of fission product retention at mitigated thermally-induced SGTR using ARTIST experimental data

“…Results of the ARTIST project (Guentay et al, 2004;Lind et al, 2011) which investigated the aerosol retention in the steam generator during SGTR show the following: The larger the particle size and the velocity through the break, i.e., the inertia of the particles, the higher the retention close to the break. Here we define the break zone to be typically a distance of the order of about 10 diameters of the equivalent break area.…”

“…Retention of radioactive materials on their way out of the SG to environment was the object of studies in the international ARTIST research program (AeRosol Trapping In STeam generator, Guentay et al, 2004). The project investigated experimentally the aerosol and droplet retention in a model PWR steam generator, under dry, wet and accident management conditions.…”

Fission Product Release and Transport

“…Due to lack of an alternative, these models are also used in turbulent conditions, though the justification for this is slender and requires validation. Validation of models is necessary in this area, and it is hoped that the ARTIST program [82] will allow assessment of the tube bundle, separator, and dryer models. Neither is deposition in tube bundles considered where this will occur to perhaps a limited extent in the reactor vessel where flow passes through upper core structures on its way to the hot leg as well as in the steam generator tube bundle in the case of a steam generator tube rupture.…”