NUMERICAL AND EXPERIMENTAL INVESTIGATION OF 3D COOLANT TEMPERATURE DISTRIBUTION IN THE HOT LEGS OF PRIMARY CIRCUIT OF REACTOR PLANT WITH WWER-1000
24th Symposium of AER on VVER Reactor Physics and Reactor Safety (2014, Sochi, Russia)
Core surveillance and monitoring
Abstract
NUMERICAL AND EXPERIMENTAL INVESTIGATION OF 3D COOLANT TEMPERATURE DISTRIBUTION IN THE HOT LEGS OF PRIMARY CIRCUIT OF REACTOR PLANT WITH WWER-1000
Saunin Yu., Dobrotvorski A., Semenikhin A., Ryasny S. JSC «ATOMTECHENERGO», Mytishchi, Russia
Kulish G., Abdullaev A.
Scientific-Technical Center “Nuclear fuel cycle”, Kharkov Physical-technical Institute, Kharkov, Ukraine
ABSTRACT
When implementing programs to increase capacity of the existing NPPs with WWER-1000 significantly increased demands on the accuracy of determining the weighted average reactor power depends strongly on the temperature stratification in the main circulation pipes, especially in the hot legs.
The paper presents the full-scale experimental data on the coolant temperature distribution in the hot legs obtained with help of regular I&C systems and first of all in-core monitoring system. These data was obtained at the pilot operation stage of unit-4 Kalinin NPP in a stationary condition at nominal power level. For the same condition the results of calculating simulation are presented under using the CFD code.
For the calculations of the temperature distribution in the main circulation pipes had used the computer code Solid Works Flow Simulation (COSMOSFloWorks). Simulation is carried out under the following conditions:
- calculation of the coolant velocity and temperature distribution, temperature condition of the reactor pressure vessel and its internals was performed by solving of the thermal conductivity dual problem;
- due to the small differences between loops coolant temperatures at the reactor inlet the stream swirling in the downcomer was not taken into account. Distribution of flow rates and coolant temperature at the core outlet was led to a 60° symmetry;
- in order to reduce the amount of calculations was simulated only “hot” part of primary
circuit from the exit of coolant from the reactor core till turning pipe to steam generator.
It was confirmed the presence of previously noted to all reactors common mechanism of formation stratified flows in the reactor vessel at the inlet of hot legs. According this mechanism the most heated jet of fluid and jet with an average temperature from the fuel assemblies at the central part of the core pass tube space up to perforation shell of the protective tube block without significant mixing and localized in the upper parts of the outlet nozzles. The coldest jet fuel assemblies from a number of peripheral and cold jets of leakage through the enclosure and annular gap localized at the bottom of outlet nozzles almost without mixing. Noted that the nature of localization is different in different loops with even and odd numbers.
A satisfactory convergence of the experimental and calculated data was obtained. Noted some underestimation of the using the CFD code calculation of influence of perforation asymmetry in the protective tube block, and also noted the possible influence on the calculation results of exceptions of swirling in the downcomer of the reactor, to which impel the test results of the temperature field testing at the core inlet.
Based on a comparative analysis of experimental and calculated data suggests possible solutions and the amount of further research.