Vaporization thermodynamics of fission products from fuel under nuclear-accident conditions

Partial pressures of the refractory-metal-type (Zr, Nb, Mo, Tc, Ru, Rh, Pd) fission products were evaluated for conditions anticipated to exist in-core during the core-dryout phases of a nuclear-reactor accident. Measured or estimated thermodynamic quantities for the gaseous elements, oxides, and hydroxides; the solid solutions in UO/sub 2/; and the metals were used to evaluate partial pressures as a function of fuel temperature and coolant-gas composition (i.e., ratio of H/sub 2/ to H/sub 2/O). Simplified equations for the total effective pressure of each fission product are derived from the calculations. Thermodynamic values whose experimental evaluation would be most likely to improve the accuracy of this assessment are identified