CATHENA Validation Against MAPLE Subcooled Boiling Data

Abstract

The MAPLE-X10 (Multipurpose Applied Physics Lattice Experimental-NRX 19 MW) reactor developed by AECL Research [1] is a light-watercooled pool-type reactor. The reactor it currently being built at AECL's Chalk River Laboratories, and will be used as a dedicated isotope producer. The non-equilibrium effects of subcooled boiling are predicted to strongly affect the transient behaviour of the reactor under some postulated upset conditions in MAPLE-X10. It is necessary to be able to predict the local subcooled void fraction accurately to be able to determine the core pressure drop, the mass flux and void reactivity effects. CATHENA, an advanced two-fluid thermalhydraulics code [2,3], was wed to predict the void fractions during subcooled boiling for conditions measured in the MAPLE single-pin heat transfer teat facilities at AECL's Whiteshell Laboratories (WL) and at the University of British Columbia (UBC). Subcooled boiling void fractions must be predicted accurately by CATHENA, especially if the code is intended to simulate the void reactivity feedback effect on power in the MAPLEX10 reactor. The data provide void fractions measured at a fixed location near the top of the Fuel Element Simulator (FES) for high flows (WL) and for low flows (UBC). These data cover pressures between 110 and 328 kPa, local subcooling between 8 and 66 C and flow velocities from 0.1 to 1.0 m/s. Good agreement was obtained with CATHENA void fraction calculations for the majority of the cases analyzed.