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COTTAP: A Computer Code for Simulation of Thermal Transients in Secondary Containments of Boiling Water Reactors

Mark A. Chaiko, Michael J. Murphy

Nuclear Technology

Volume 94 / Number 1 / April 1991 / Pages 44-55


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The Compartment Transient Temperature Analysis Program (COTTAP) was developed by the Pennsylvania Power & Light Company for postaccident boiling water reactor (BWR) secondary containment thermal analysis. The code makes use of previously developed implicit temporal integration methods and sparse matrix inversion techniques to allow modeling of an entire BWR secondary containment. Investigations were made with a model consisting of 121 compartments and 767 heat-conducting slabs. The simulation presented involves the numerical integration of 20 101 ordinary differential equations over a 30-h simulation period. Two hours of CPU time were required to carry out the calculation on an IBM 3090 computer. The COTTAP code considers natural convection and radiation heat transfer between compartment air and walls through a detailed finite difference solution of the slab conduction equations. Heat addition from hot piping and operating equipment, and cooling effects associated with ventilation flows and compartment heat removal units are also included. Additional capabilities of COTTAP include modeling of compartment heatup resulting from steamline breaks and simulation of natural circulation cooling in compartments with flow paths at differing elevations.

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