### Abstract

The characteristics of the thermohydraulic solutions in
APROS are considered for the nuclear power plant
modelling. The thermohydraulic model of the APROS plant
analyzer includes three levels of solutions, homogeneous
3-equation model, 5-equation drift flux model and
6-equation two-fluid model. In practical modelling of
versatile process systems different approaches are
selected for different types of the power plant sections.
The 3-equation model is used for turbines and auxiliary
systems. The 5-equation model and 6-equation model are
alternative models for main process sections of the
primary and secondary sides. The 5-equation model has
been typically selected for the real time applications
and the 6-equation model for the safety analysis
applications. The validation needs for both approaches
are the same. Because the change of the solution mode is
an easy task in APROS, the validation tasks are typically
performed in parallel for 5-equation and 6-equation
models. By calculating in parallel with both models
systematic errors in solutions may be pointed out. The
testing against both separate effects tests and integral
tests is an essential part in the thermohydraulics. In
different plant applications different physical features
are important. The analysis requirements vary from one
application to another. When nodalizations together with
increased computer speed are growing up, the earlier
validation cases may be insufficient. That is why the
content of the code has to be known in detail. Such an
expertise in the code development has to be gained that
properties of the code against other thermohydraulics
codes are known.

Original language | English |
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Title of host publication | Proceedings of the 2nd CSNI Specialist Meeting on Simulators and Plant Analysers |

Place of Publication | Espoo |

Publisher | VTT Technical Research Centre of Finland |

Pages | 378-389 |

ISBN (Print) | 951-38-5269-5 |

Publication status | Published - 1999 |

MoE publication type | A4 Article in a conference publication |

Event | 2nd CSNI Specialist Meeting on Simulators and Plant Analysers - Espoo, Finland Duration: 29 Sep 1997 → 2 Oct 1997 |

### Publication series

Series | VTT Symposium |
---|---|

Number | 194 |

ISSN | 0357-9387 |

### Conference

Conference | 2nd CSNI Specialist Meeting on Simulators and Plant Analysers |
---|---|

Country | Finland |

City | Espoo |

Period | 29/09/97 → 2/10/97 |

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## Cite this

Miettinen, J., Karppinen, I., Hänninen, M., & Ylijoki, J. (1999). Evaluation of two-fluid and drift flux thermohydraulics in APROS code environment. In

*Proceedings of the 2nd CSNI Specialist Meeting on Simulators and Plant Analysers*(pp. 378-389). VTT Technical Research Centre of Finland. VTT Symposium, No. 194