Thermodynamics of the O–U system: III – Critical assessment of phase diagram data in the U–UO2+x composition range

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.…”

“…Lyon and Baily [6] reported the melting point was 3113 K, while Latta and Fryxell [7] measured the solidus and the liquidus of UO 2±x and reported 3149 K for the melting point of UO 2.00 . Recently Baichi et al [12] reviewed the melting temperature of UO 2±x and recommended a value of 3138 ± 15 K for UO 2.00 . Fig.…”

“…Many studies [12,33,34] on the phase diagram of the U-O system have been reported, and a ther- modynamics database of the system has been constructed. It was reported that UO 2±x has a congruent melting point at O/Uratio of 2.00 and that the solidus and the liquidus decreases with increasing and decreasing x.…”

“…Consequently, the solidus and the liquidus can be derived in a more reliable manner from the thermal arrests observed by measuring the temperature during heating or cooling of samples encapsulated in tungsten capsules. Baichi et al [12] fully explained the reason of the large error in the V-filament method and concluded that the samples have to be encapsulated. Lyon and Baily [6] and Aitken and Evans [8] measured the solidus and the liquidus of the mixed oxide systematically by the thermal arrest method.…”

“…The sum of metallic impurities in the pellet was less than 500 ppm and the Am-contents contained in the (Pu 0. 12 …”