Thermodynamic properties and equations of state for fast reactor safety analysis. Pt. I. Analytic equation-of-state model

For pt.II see ibid., vol.183, p.193-211, 1998. Numerical simulation of postulated severe-accident sequences in liquid-metal fast reactors (LMFRs) requires thermodynamic properties of reactor-core materials over wide temperature and pressure ranges. Here an improved analytic equation-of-state (EOS) model using flexible thermodynamic functions is newly developed for a multiphase, multicomponent fluid-dynamics code for LMFR safety analysis. Extension of a van der Waals type equation for vapor phase is also proposed to include the dimerization process of sodium vapor and thereby enables us to predict sodium vapor properties with adequate accuracy. The present EOS model is designed to have adequate accuracy at high temperature and high pressure and to consistently satisfy basic thermodynamic relationships over a wide temperature range without deterioration of the computing efficiency. The newly introduced fluid-dynamic algorithm for pressure iteration consistently coupled with the EOS model is also described in the present paper. (orig.)