Ruthenium release modelling in air and steam atmospheres under severe accident conditions using the MAAP4 code

Thermodynamic Properties of Gaseous Ruthenium Species

“…It was concluded that additional data are required in order to make a reliable assessment of the ruthenium outside releases in case of severe accident. Since this literature survey in 1986, many works were performed on this topic − to fill the gap in the prediction of ruthenium behavior. Ruthenium is usually considered as a low volatile fission product, with less than 5% releases, but in some conditions involving ruthenium oxides formation, as shown during the VERCORS HT2 tests dealing with the fission product release from UO 2 fuel with a moderate burn-up [48 (GWd/tU)], in pure steam, the ruthenium released amounted to 60% of the fuel inventory and a relevant part (12%) was transported as the oxide form and not deposited in the experimental line, even at quite a low temperature (150 °C).…”

“…Ruthenium is usually considered as a low volatile fission product, with less than 5% releases, but in some conditions involving ruthenium oxides formation, as shown during the VERCORS HT2 tests dealing with the fission product release from UO 2 fuel with a moderate burn-up [48 (GWd/tU)], in pure steam, the ruthenium released amounted to 60% of the fuel inventory and a relevant part (12%) was transported as the oxide form and not deposited in the experimental line, even at quite a low temperature (150 °C). Some modelings were performed , to predict ruthenium release from the fuel. Concerning ruthenium transport in the reactor coolant system, recent experimental works ,,, were devoted to better characterize deposits and gas phase of ruthenium oxides along a thermal gradient.…”

Thermodynamic assessment of RuO4 oxide

“…RuO 4 (g) shows a high volatility at low temperatures and many groups suspect that it is the source of ruthenium transport in a carrier gas flowing over organic or aqueous solutions used in nuclear effluent treatment. [6][7][8][9][10][11][12][13]. In previous studies -(i) we proposed new thermodynamic data for RuO 2 (s) [14] i.e.…”

Fission products and nuclear fuel behaviour under severe accident conditions part 1: Main lessons learnt from the first VERDON test

“…These experimental sequences were carried out in a very high activity cell and were commonly considered to be complementary to the PHEBUS FP [4] integral tests and comparable with certain tests carried out abroad: HI/VI [5] in the United States, VEGA [6] in Japan or the program conducted in Canada [7]. The experimental results of this program are used to (a) define the envelope values for released fraction within the scope of assessing reference source terms for all French PWRs, and (b) validate the semi-empirical or mechanistic models regarding FP release and transport while qualifying the simulation codes by integrating these models [8], [9], [10], [11].…”