COBRA-PI: an extension of the COBRA-3M code dynamically dimensioned to accept pin bundles of any size. [LMFBR]

COBRA, in general, performs a thermal-hydraulic analysis of an actual pin bundle by subdividing the bundle cross-section into coolant subchannels, pin sectors, duct wall sectors. Its calculation includes heat convected axially upward through coolant mass flow, heat flow between pin sectors and adjoining subchannels, and heat and mass flow between coolant subchannels. COBRA-3M is a version of COBRA built for LMFBR applications, that includes a sophisticated thermal model of fuel pins and duct wall. COBRA-3M that can explicitly model a wider variety of pin bundle configurations than 3M would allow and includes significant improvements to its thermal modeling. COBRA-PI is currently being used for thermal-hydraulic analysis of hypothetical LMFBR accident transients in both power and flow. Pin bundles currently being analyzed explicitly range from 7 to 37 pins of axial lengths ranging from approx. 0.3-2.0 meters.