Vapor pressures of species in the Pu-C system were reviewed by Marcon,207 Holley et al.,4 and Matzke.5 The vapor phase in equilibrium with Pu carbides is always richer in plutonium than the condensed phase is. The partial pressure of Pu(g) dominates over other gaseous species, to the point that those are almost negligible in comparison. Therefore, any vaporization study on this system should take into account segrega­tion effects in the condensed phase, and it is impossible to treat the different Pu-C compounds separately. Marcon’s results,207 summarized in the following equa­tions, were obtained with longer measurement times in order to vent out oxygen impurities, leading to vapor pressures in equilibrium with pure carbides.

18 800
T

in the Pu-PuC and PuC-Pu2C3 domain, from room

temperature to the melting point

20200 r n log pPu = — + 4.23 [49]

in the Pu2C3-C domain, between 1500 and 2000 K; 25200

log pPu = — T + 6.8 [50]

in the Pu2C3-PuC2 domain, between 2000 and 2300 K;

, 18 150 r n

log pPu =— — + 3.15 [51]

in the PuC2-C domain, between 2000 and 2500 K.

Pu(g) partial pressure over Pu-C system is higher than U(g) pressure over U-C system in the same
temperature and composition ranges (Figure 16). The partial pressure pC1of C(g) is much higher than the partial pressures of other carbon-bearing species, which can be neglected in comparison to it. In Figure 16, the partial pressure values in equilibrium with PuC(liq) were extrapolated from those in equi­librium with PuC(s) including a correction for the enthalpy of melting.