A standard problem for HECTR-MAAP comparison: Incomplete burning

Technical Report · Mon Aug 01 04:00:00 EDT 1988

OSTI ID:6945306

Wong, C C

To assist in the resolution of differences between the NRC and IDCOR on the hydrogen combustion issue, a standard problem has been defined to compare the results of HECTR and MAAP analyses of hydrogen transport and combustion in a nuclear reactor containment. The first part of this standard problem, which addresses incomplete burning of hydrogen in the lower and upper compartments, has been completed. In this report, a critical review and comparison of the combustion models in HECTR and in MAAP will be presented, and HECTR analyses of this standard problem and its comparison with MAAP predictions will be discussed. Review of these two combustion models shows that HECTR and MAAP yield very different pictures of the burning process. MAAP calculations, which implicitly employ a 5% hydrogen ignition criterion, yield a burn time on the order of two hours, i.e., the burning process resembles a standing diffusion flame, rather than a flame propagating through a homogeneous mixture. Such predictions are not unreasonable for some accidents in ice-condenser plants. However, there are accident scenarios in which high concentrations of steam exist in the lower compartment (e.g., about 27% as in this standard problem). Ignition occurs at a higher concentration of hydrogen (about 7%). This will produce a propagating flame rather than a diffusion flame. Hence MAAP-calculated combustion pressures and temperatures appear to be much lower than one would expect. HECTR, on the other hand, predicts that ignition occurs at hydrogen concentration of 7% and the burning takes only a few seconds. This leads to a sharp, short but higher pressure increase.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (USA). Div. of Systems Research; Sandia National Labs., Albuquerque, NM (USA)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 6945306
• Report Number(s): NUREG/CR-4993; SAND-87-1858; ON: TI88017185
• Country of Publication: United States
• Language: English

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