Passive systems are being considered for advanced reactor designs because of their enhanced reliability against an extended loss of offsite power. Particularly, the SAfety COndenser (SACO) stands out because of its capacity of passively removing core decay heat through the steam generators by condensing steam inside a immersed heat exchanger. This article presents recent experimental data and the associated numerical calculations on the vertical straight-tube SACO installed at the PKL facility. In particular, the SACO power removal capacity has been studied within the frame of test P1.1 consisting of steady state phases A, B, C and D with varying pool liquid levels and a Core Exit Temperature of 237 °C i.e. 20 K subcooling. Experimental results show the SACO capability to transfer its nominal power of 450 kW despite the accumulation of nitrogen in the straight tubes. Improved venting procedures of phases A2 and C2 allowed a partial removal of nitrogen from the tubes and hence, an increase of the maximum core power to keep the CET constant in comparison to their counterpart phases A and C. The accumulation of nitrogen in the tubes leads to the formation of passive zones characterised by a degraded heat transfer towards the pool and significant cool-down of the liquid film. An important numerical work has also been conducted using the CATHARE-3, ATHLET, TRACE, RELAP-5 system thermalhydraulic codes and Neptune_cfd, either in standalone mode or coupled with CATHARE-2. Several approaches have been adopted in order to model the primary system, SACO pool, straight tubes, boundary and initial conditions (e.g. nitrogen content, heat losses), auxiliary components (heaters, pump cooling), which add up to the physical models when analysing discrepancies with experimental results. Generally, codes are able to predict the phenomena happening in PKL, although further efforts should be invested in the use of 3D approaches to model the pool and the improvement of condensation modelling in vertical tubes for the SACO-operating region.
Experimental and numerical analysis on safety condenser performance based on P1 experiments at the PKL facility
Polidori M.;
2025-01-01
Abstract
Passive systems are being considered for advanced reactor designs because of their enhanced reliability against an extended loss of offsite power. Particularly, the SAfety COndenser (SACO) stands out because of its capacity of passively removing core decay heat through the steam generators by condensing steam inside a immersed heat exchanger. This article presents recent experimental data and the associated numerical calculations on the vertical straight-tube SACO installed at the PKL facility. In particular, the SACO power removal capacity has been studied within the frame of test P1.1 consisting of steady state phases A, B, C and D with varying pool liquid levels and a Core Exit Temperature of 237 °C i.e. 20 K subcooling. Experimental results show the SACO capability to transfer its nominal power of 450 kW despite the accumulation of nitrogen in the straight tubes. Improved venting procedures of phases A2 and C2 allowed a partial removal of nitrogen from the tubes and hence, an increase of the maximum core power to keep the CET constant in comparison to their counterpart phases A and C. The accumulation of nitrogen in the tubes leads to the formation of passive zones characterised by a degraded heat transfer towards the pool and significant cool-down of the liquid film. An important numerical work has also been conducted using the CATHARE-3, ATHLET, TRACE, RELAP-5 system thermalhydraulic codes and Neptune_cfd, either in standalone mode or coupled with CATHARE-2. Several approaches have been adopted in order to model the primary system, SACO pool, straight tubes, boundary and initial conditions (e.g. nitrogen content, heat losses), auxiliary components (heaters, pump cooling), which add up to the physical models when analysing discrepancies with experimental results. Generally, codes are able to predict the phenomena happening in PKL, although further efforts should be invested in the use of 3D approaches to model the pool and the improvement of condensation modelling in vertical tubes for the SACO-operating region.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
