Analysis of LMFBR containment response to an HCDA using a multifield Eulerian code

This paper describes a computer code, MICE (Multifield Implicit Continuous-fluid Eulerian Containment Code), which is being developed at Argonne National Laboratory (ANL) for the analysis of containment response to a hypothetical core disruptive accident (HCDA). The code is applicable to multifield flow problems where material fields are allowed to have penetrations. Reactor structures are treated as axisymmetrical shells and solved by the large-displacement and small-strain theory. The numerical technique used for the solution of the multifield fluid flow code consists of two principal steps. In the first step, the material fields in each cell are treated independently; coupling effects are evaluated by binary interactions between fields. In the second step, a pressure equilibration is performed among all fields in each cell; volume fractions are also adjusted in this step. A partial donor-cell form is adopted for calculating the convective fluxes to minimize the truncation errors; a Newton-Raphson formula is used for the numerical iteration. Implicit treatment of the mass transport and state equations allows the flow speeds to range from far subsonic (incompessible flow) to supersonic. The coupling drag forces between fields can vary from very weak to those strong enough to tie the fields together completely. Phase transition and heat transfer between fields are also considered into calculation. Two sample problems have been performed using the MICE code. The first illustrates the relative motions of the material fields after the initiation of a core disassembly accident. Core support structure and core barrel are modelled as rigid obstacles. The second demonstrates the interactions between fluid and structures