SCDAP/RELAP5/MOD 3.1 code manual: MATPRO, A library of materials properties for Light-Water-Reactor accident analysis. Volume 4

Melting behavior of (Th,U)O2 and (Th,Pu)O2 mixed oxides

“…Our MD calculated melting temperatures are also compared with previous experimental investigations by Latta et al [30] and Böhler et al [32]. These calculated melting temperatures are in very good agreement for the ThO2 rich part of the phase diagram compared to the ideal solidus line calculated using Equation 15 and experimentally determined values by Böhler et al [32]. In the UO2 rich part, the MD calculated values slightly underestimate the ideal solidus line but the estimated values are within the error bars of experimental measurements by Böhler et al [32] (except at the 60 % composition).…”

“…Experimentally reported melting temperatures of UO2 vary from 3050 K to 3138 K ( Table 2) [11][12][13][14][15][16][17][18]. The melting point of UO2 given in MATPRO [15] is 3113.15 K, based on the equations for the solids and liquids boundaries of the UO2-PuO2 phase diagram given by Lyon et al [11].…”

“…The melting point of UO2 given in MATPRO [15] is 3113.15 K, based on the equations for the solids and liquids boundaries of the UO2-PuO2 phase diagram given by Lyon et al [11]. The recommended value by ORNL [17] for UO2.00 is 3120 ± 30 K. In recent experimental measurements of the heat capacity of liquid UO2, using laser heating of a UO2 sphere, Ronchi et al [13] made several measurements of the freezing temperature of UO2 on different samples.…”

Behavior of Coated Fuel Particle of High-Temperature Gas-Cooled Reactor under Reactivity-Initiated Accident Conditions

“…The density of UO 2 decreases discontinuously when the phase of UO 2 changes from solid to liquid. 10) Theoretically, this phase change causes volume and diameter increases of approximately 17 and 6%, respectively. Therefore, it is considered that the melted and swelled fuel kernel compresses the low-density buffer layer in the radial direction, and finally, the fuel particle is failed by the mechanical interaction between the swelled fuel kernel and the coating layer when the energy deposition during the pulse irradiation is higher than 1.40 kJ/gUO 2 .…”

“…The target fuel temperatures of the lower segment (2L) in Test 522-2 and upper segment (3U) in Test 522-3 were about the melting point of UO 2 (3,113 K). 10) If the condition is achieved, the expected fuel temperature of the upper segment (2U) in Test 522-2 was below the melting point of UO 2 and that of the lower segment (3L) in Test 522-3 was above the melting point of UO 2 . In Test 522-4, the inserted reactivity was selected to heat the fuel of both segments (4U and 4L) to temperatures sufficiently above the melting point of UO 2 .…”