CATHENA Prediction of MAPLE-X10 Performance During a Complete Pipe Severance

Abstract

A prototype MAPLE reactor called MAPLE-X10 (Multipurpose Applied Physics Lattice Experimental NRX for 10 MW) is planned for construction at the Chalk River Nuclear Laboratories. One unique design feature of MAPLE-X10 is a sealed equipment room that helps to prevent loss of primary fluid into tho environment in the event of a primary pipe rupture. The thermalhydraulics computer code CATHENA war used to demonstrate the safety advantage of the sealed equipment room design to support the safety analysis of MAPLE-X10 CATHENA is a one-dimensional two-fluid thermalhydraulics computer code developed at the Whiteshell Nuclear Research Establishment primarily to analyze postulated loss-of-coolant accident scenarios for CANDU nuclear reactors. CATHENA uses a semi-implicit, staggered-mesh, finite difference solution method that is not transit-time limited. It is capable of modelling the non-equilibrium effects of subcooled boiling at low pressures. These conditions dominate the transient behaviour of the MAPLE-X10 reactor for the upset conditions studied. This paper presents the CATHENA idealization used to model the reactor with and without the sealed equipment room design. CATHENA prediction results are shown for a complete pipe severance scenario. These results demonstrate that the sealed equipment room design contributes to the safety of the MAPLE-X10 reactor.