W.H. McCulloch ... [and others] ; prepared for Severe Accident Assessment Branch, Division of Accident Evaluation, Office of Nuclear Regulatory Research, and Chemical Engineering Branch, Division of Engineering, Office of Nuclear Reactor Regulation [U.S. Nuclear Regulatory Commission], under interagency agreement DOE 40-550-75 ; [prepared by Sandia National Laboratories, for the United States Department of Energy, under contract DE-AC04-76DP00789]