Determination of Blowdown Heat Transfer Based on Experimental Investigation of RD14 Experiments. Analysis with the Code SLLOH
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Abstract
This paper presents the results of analysis performed to better understand blowdown cooling phenomena associated with a rapid depressurisation in a high pressure, high enthalpy system. Large conservatisms are used for the heat transfer coefficients during the blowdown phase of a large loss-of-coolant accident (LOCA) analysis and it is believed that higher heat transfer coefficients can be used if they can be experimentally supported. Detailed analyses of the experimental results obtained in the RD14 facility during rapid depressurisation transients serve this purpose. The SSLOH code (1) was employed to quantify the heat transfer rates during blowdown.
A large amount of data has been gathered during the performance of experiments B8607 to B8610 which has to be analysed in such a way that it can be used for model development and model verification purposes. A particular effort has been made to better understand the behaviour of the system and to relate it back to anticipated behaviours.
The area of interest was the channel thermalhydraulic behaviour during blowdown and the modes of heat transfer which take place during that period. It is important to be able to assess the amount of water that is left in the channel since it can be credited for fuel cooling before the Emergency Cooling Injection (ECI) reaches the core. In general, system codes using the homogeneous approximation such as SOPHT predicts a very sustained channel voiding leading to high fuel and fuel sheath temperatures.
Because the experimental data indicated stratified conditions in the heated sections toward the end of the initial blowdown period, it was decided to employ the SLLOH code to analyse theses tests. This proved successful and serves as a validation of the models employed in this code.
A large amount of data has been gathered during the performance of experiments B8607 to B8610 which has to be analysed in such a way that it can be used for model development and model verification purposes. A particular effort has been made to better understand the behaviour of the system and to relate it back to anticipated behaviours.
The area of interest was the channel thermalhydraulic behaviour during blowdown and the modes of heat transfer which take place during that period. It is important to be able to assess the amount of water that is left in the channel since it can be credited for fuel cooling before the Emergency Cooling Injection (ECI) reaches the core. In general, system codes using the homogeneous approximation such as SOPHT predicts a very sustained channel voiding leading to high fuel and fuel sheath temperatures.
Because the experimental data indicated stratified conditions in the heated sections toward the end of the initial blowdown period, it was decided to employ the SLLOH code to analyse theses tests. This proved successful and serves as a validation of the models employed in this code.
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