Radiation-to-steam model for reactor core thermal analysis

A radiation-to-steam heat transfer model has been included in the MOXY/SCORE adaptation of the SCORE/EVET code. MOXY/SCORE is a subchannel thermal-hydraulic computer program with models for fuel rod conductive, radiative, and convective heat transfer, for metal-water reaction heat addition, for fuel-to-cladding gap heat transfer, and for fuel rod mechanical response. To assess the impact of radiation-to-steam on transient reactor core behavior, MOXY/SCORE has been used to analyze a sample transient with conditions typical of those to be encountered in a proposed inlet flow blockage test at the INEL Power Burst Facility. The conditions are characterized by a high void fraction (approaching 100%), high fuel pin power (70 to 80% of operating power), and high pressure (approximately 7 MPa). Under these conditions radiation will be a dominant mode of heat transfer and steam participation in radiative heat transfer will be significant