Experimental studies and thermodynamic modelling of volatilities of uranium, plutonium, and americium from their oxides and from their oxides interacted with ash

Abstract

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Characterization of urania vaporization with transpiration coupled thermogravimetry

“…Since the integral (reacting) system can be considered U-O-H, the UO 2 (OH) 2 oxyhydroxide species will only form in very small relative concentrations due to the low partial pressure of water vapor and high temperature of the measurements [1]. The mass loss from UO 2 (OH) 2 has been documented to be well within experimental error and undetectable by the transpiration technique at similar conditions [2]. From Eqn.17 in [1], the following relation can be derived:…”

“…In Fig. 5, the results from this study, along with one from [2], are plotted against calculated p from four different sources. The two relations, the Lindemer and Besmann [14] and Blackburn [3] models, describing the activity of UO 2 in UO 2+x with 2 O p along with the thermodynamic data used to compute the curves labeled Blackburn [3], Ozrin [5] , and AECL [4] are well described in [1].…”

“…6 compares the p relation is operative. Olander [1] reviewed the available thermodynamic data and recommended K eq based on transpiration measurements of UO 3 (g) over U 3 O 8 determined by Kirkorkian [2]. Fig.…”

“…A breach of cladding allows pressurized water or steam to contact and oxidize UO 2±x forming both UO 3 and UO 2 (OH) 2 vapors. Knowledge of the thermochemistry of UO 3 and H 2 O facilitate determining equilibrium UO 2 (OH) 2 pressures for UO 2±x in steam from experimentation [2] and allow for a better understanding of fuel response to severe accident conditions. While the behavior of H 2 O is well understood from a computational thermodynamic standpoint, Olander [1] reviewed several studies [3; 4; 5]…”

Thermodynamic constants for actinide oxides and oxyhydroxides relevant to actinide volatility calculations for thermal oxidation processes

“…The AH o values for all of the gaseous species are calculated from our data f,298 [3] using the 3'a law method The AH°• " f,298 values for PuO3(g), PuO2(OH)2(g), AmO3(g), and AmO2(OH)2(g)…”