Federal regulations (10CFR71) require radioactive material transport packages to safely withstand a 30min fully engulfing fire. The three-dimensional Container Analysis Fire Environment (CAFE-3D) computer code was developed at Sandia National Laboratories to simulate the response of massive packages to large fires for design and risk studies. These studies require rapid and accurate estimates of the package temperature distribution for a variety of package designs and fire environments. To meet these needs CAFE-3D links a finite element model that calculates the package response to the Isis-3D CFD fire model. ISIS-3D combines computational fluid dynamics with reaction chemistry and thermal radiation models to rapidly estimate the heat transfer from a fire. In the current work, parameters used in the fire model were determined. Simulations were then performed of a test that modeled the conditions of a truck-sized nuclear waste package in a regulatory fire under light wind conditions. CAFE-3D underestimated the ability of the wind to tilt the fire and deliver oxygen to the region above the fuel pool. However, it accurately and rapidly estimated the total heat transfer to the test object. CAFE-3D will become a more useful tool for estimating the response of transport packages to large fires once it has been benchmarked against a larger range of fire conditions.

The Container Analysis Fire Environment (CAFE-3D) is a computer code developed at Sandia National Laboratories to simulate heat transfer from large fires to engulfed packages for transportation risk studies. These studies require accurate estimates of the total heat transfer to an object and the general characteristics of the object temperature distribution for a variety of fire environments. Since risk studies require multiple simulations, analysis tools must be rapid as well as accurate. In order to meet these needs, CAFE-3D links Isis-3D (a general purpose computational fluid dynamics/radiation heat transfer code that calculates fire behavior) to commercial finite element (FE) codes that calculates package response. In this scheme, CAFE-3D runs Isis-3D only periodically during the calculation to update local fire boundary conditions to the FE model. The frequency and duration of the fire update calculations are user controlled based on the fire time and/or package temperature rise. In this paper we outline various models employed by Isis-3D and the method for finding the soot volume fraction used to define the edge of the diffusively radiating fire zone. Then, the linkage between Isis-3D and the MSC P\Thermal finite element code is explained. Finally a benchmarking simulation, which reproduced the temperature data from the 30-minute light-crosswind fire using only 10 hrs of computational time on a standard workstation, is described.