The NC-1 natural circulation test with stepwise reduction of the primary coolant inventory has been performed within the framework of the OECD PSB-VVER Project. This test is aimed at providing data to get further understanding about the relation between the natural circulation modes and the mass inventory in VVER-1000 like designs. The NC-1 test was designed to follow the usual procedure of obtaining a set of quasi-steady states at different primary mass inventories. Due to this, the test does not simulate a real accident but provides data for code assessment regarding the prediction of different mechanisms of core cooling at different natural circulation modes. The simulation of this test using RELAP5/MOD3.3 has been performed. Boundary conditions have been imposed following the experiment specification data, in particular the imposed mass inventory time history. Some installation peculiarities, like significant concentrated heat extraction, required particular attention and data have been taken from the experimental database. The results obtained show reasonable good agreement with the experiments. All the stages of the transient have been properly simulated, among them the time for natural circulation “flow interruption” (reflux condensation is not present because of the geometry) and the time for the cladding temperature excursion. Simulation difficulties have been found in relation with the time of loop seal clearance, which are attributed to errors inherent to the mass inventory. The results, both experimental and numerical, have been presented using natural circulation flow maps that are well established for PWRs of Western design. It has been shown that results for this installation fit advantageously within the limits already known for natural circulation
Simulation of a Natural Circulation Test in the PSB-VVER Installation
D'AURIA, FRANCESCO SAVERIO;
2005-01-01
Abstract
The NC-1 natural circulation test with stepwise reduction of the primary coolant inventory has been performed within the framework of the OECD PSB-VVER Project. This test is aimed at providing data to get further understanding about the relation between the natural circulation modes and the mass inventory in VVER-1000 like designs. The NC-1 test was designed to follow the usual procedure of obtaining a set of quasi-steady states at different primary mass inventories. Due to this, the test does not simulate a real accident but provides data for code assessment regarding the prediction of different mechanisms of core cooling at different natural circulation modes. The simulation of this test using RELAP5/MOD3.3 has been performed. Boundary conditions have been imposed following the experiment specification data, in particular the imposed mass inventory time history. Some installation peculiarities, like significant concentrated heat extraction, required particular attention and data have been taken from the experimental database. The results obtained show reasonable good agreement with the experiments. All the stages of the transient have been properly simulated, among them the time for natural circulation “flow interruption” (reflux condensation is not present because of the geometry) and the time for the cladding temperature excursion. Simulation difficulties have been found in relation with the time of loop seal clearance, which are attributed to errors inherent to the mass inventory. The results, both experimental and numerical, have been presented using natural circulation flow maps that are well established for PWRs of Western design. It has been shown that results for this installation fit advantageously within the limits already known for natural circulationI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
