Melting Temperature of Mixed Oxide Fuels for Fast Reactors.

Abstract

Alternation of the melting temperature of irradiated mixed oxide (MOX) fuel in fast reactors with progress of burnup was determined in relation to the actinide fractions contained and of the oxygen-to-metal (O/M) ratio. Based on ideal solution models of UO 2 -PuO 2 and UO 2 -PuO 2 -Am 2 O 3 systems and on correlations obtained of the measured melting with O/M ratio and with burnup, an equation was derived expressing the estimated melting temperature T rev (K) as function of the factors mentioned above that affect the temperature:, where X 1 is the plutonium fraction (Pu/(Pu+U)), X 2 the americium fraction (Am/(Pu+U+Am)), X 3 the burnup (GWd/t), and X 4 the O/M ratio (−) (not exceeding 2.00). Toward advanced stage of burnup, the tendency of irradiated fuel melting temperature to lower with burnup progress presented a tendency to level off its rate of descent.

Solidus and liquidus of plutonium and uranium mixed oxide

“…Fig. 5 compares the melting point of UO 2 observed in previous studies [6,7,9,12,[20][21][22][23][24][25][26]. The melting point of UO 2.00 observed in the present work was 3128 ± 35 K which is in good agreement with the average of those earlier works.…”

“…The apparatus and procedures for determining the solidus and the liquidus of MOX used in this work were similar to those described previously [6][7][8][9][10][11]. Samples of about 10 g were taken from crushed pellets.…”

“…The maximum temperature of the fuel pellets during irradiation is limited to prevent fuel melting. So, the solidus and the liquidus of the mixed oxides have been investigated ever since the development of fast reactors was started [1][2][3][4][5][6][7][8][9][10][11]. However, the measured data are still limited because of difficulties in preparing MOX samples with precise oxygen-to-metal (O/M) ratios and in conducting accurate measurements at high temperature on plutonium containing samples.…”

Solidus and liquidus temperatures in the UO2–PuO2 system

“…1 were heated above the melting points at a constant heating rate of 40-80 K/min, and heating temperature curves were obtained. The apparatus and procedures used in this experiment were similar to those described previously [4][5][6][7][8][9][10] for determining the melting point of MOX.…”

Liquidus Temperature of Irradiated Mixed Oxide Fuels for Fast Reactors

“…(K) of irradiated fast breeder MOX fuel has been derived in the author's previous report 11) in the form:…”