There are several structures internal to reactor pressure vessel (RPV), where gravity drainage of liquid can be obstructed by upward flowing vapor. These include the upper core tie plate (UTP), where the counter current flow limiting (CCFL) mechanisms may occur during refilling and reflooding phases. Many CCFL data have been carried out with air and water as well as with steam and water, e.g. UPTF, MHYRESA and Hannover separate test facilities. In case of steam/water, the CCFL involves not only the mechanical interactions but also the thermal exchanges, due to steam condensation on subcooled emergency core cooling (ECC) water, which might lead to water breakthrough. The experiments carried out at University of Hannover (i.e. the tests with a 16x16 rod bundle) constitute a suitable database to validate RELAP5 code and to support its application in accident analysis (e.g. Atucha-2). These data have been used to study the CCFL phenomenon. The different options of RELAP5’s CCFL model are tested to assess the code performance, following the set up of the input deck through the optimization of the energy loss coefficients (Reynolds independent and dependent as well). Sensitivities are also performed to address the effect of the time step and of the nodalization on the results. The activity is concluded by investigating the phenomenon in Atucha2 reactor channel geometry.
Study of CCFL Phenomenon Based on University of Hannover Experiments
D'AURIA, FRANCESCO SAVERIO
2010-01-01
Abstract
There are several structures internal to reactor pressure vessel (RPV), where gravity drainage of liquid can be obstructed by upward flowing vapor. These include the upper core tie plate (UTP), where the counter current flow limiting (CCFL) mechanisms may occur during refilling and reflooding phases. Many CCFL data have been carried out with air and water as well as with steam and water, e.g. UPTF, MHYRESA and Hannover separate test facilities. In case of steam/water, the CCFL involves not only the mechanical interactions but also the thermal exchanges, due to steam condensation on subcooled emergency core cooling (ECC) water, which might lead to water breakthrough. The experiments carried out at University of Hannover (i.e. the tests with a 16x16 rod bundle) constitute a suitable database to validate RELAP5 code and to support its application in accident analysis (e.g. Atucha-2). These data have been used to study the CCFL phenomenon. The different options of RELAP5’s CCFL model are tested to assess the code performance, following the set up of the input deck through the optimization of the energy loss coefficients (Reynolds independent and dependent as well). Sensitivities are also performed to address the effect of the time step and of the nodalization on the results. The activity is concluded by investigating the phenomenon in Atucha2 reactor channel geometry.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
