Abstract
The results of experimental studies of local hydrodynamics and mass exchange of coolant flow behind spacer and mixing grids of different structural versions that were developed for fuel assemblies of domestic and foreign nuclear reactors are presented in the article. In order to carry out the study the models of the following fuel assemblies have been fabricated: FA for VVER and VBER, FA-KVADRAT for PWR-reactor and FA for KLT-40C reactor. All the models have been fabricated with a full geometrical similarity with full-scale fuel assemblies. The study was carried out by simulating the flow of coolant in a core by air on an aerodynamic test rig. In order to measure local hydrodynamic characteristics of coolant flow five-channel Pitot probes were used that enable to measure the velocity vector in a point by its three components. The tracerpropane method was used for studying mass transfer processes. Flow hydrodynamics was studied by measuring cross-section velocities of coolant flow and coolant rates according to the model cells. The investigation of mass exchange processes consisted of a study of concentration distribution for tracer in experimental model, in determination of attenuation lengths of mass transfer processes behind mixing grids, in calculating of inter-cellar mass exchange coefficient. The database on coolant flow in fuel assemblies for different types of reactors had been accumulated that formed the basis of the engineering substantiation of reactor cores designs. The recommendations on choice of optimal versions of mixing grids have been taken into consideration by implementers of the JSC “OKBM Afrikantov” when creating commissioned fuel assemblies. The results of the study are used for verification of CFD-codes and CFD programs of detailed cell-by-cell calculation of reactor cores in order to decrease conservatism for substantiation of thermal-mechanical reliability.
Highlights
The results of experimental studies of local hydrodynamics and mass exchange of coolant flow behind spacer and mixing grids of different structural versions that were developed for fuel assemblies of domestic and foreign nuclear reactors are presented in the article
Flow hydrodynamics was studied by measuring cross-section velocities of coolant flow and coolant rates according to the model cells
The investigation of mass exchange processes consisted of a study of concentration distribution for tracer in experimental model, in determination of attenuation lengths of mass transfer processes behind mixing grids, in calculating of inter-cellar mass exchange coefficient
Summary
Важными задачами атомной энергетики РФ являются: повышение мощности и надежности работающих АЭС, создание первой в мире плавучей АЭС, выход на западный рынок ядерного топлива и др. Нижний Новгород) выполняются разработки ТВС для реакторов различных типов. Для получения высокой интенсивности теплообмена в данной кассете предложено использовать два конструктивно различных типа решеток – «закрутка вокруг твэла» и «порядная прогонка» Опыт по созданию перемешивающих решеток был применен и в конструкции кассеты ТВС-КВАДРАТ, для которой разработаны свои типы перемешивающих и комбинированных перемешивающих ДР 1. Фрагменты перемешивающих решеток для ТВСА: а – перемешивающая решетка с дефлектором типа «закрутка вокруг твэла»; b – то же с дефлектором «порядная прогонка». 3. Тепловыделяющие сборки для реакторных установок КЛТ-40С: а – поперечное сечение ТВС; b – пояс дистанционирующей решетки. При помощи капилляров или трубки Пито, используемой в качестве отборного зонда и линии транспортировки пробы газа, за исследуемым поясом перемешивающей решетки производили замер концентрации трассера по длине и сечению ЭМ Данным зондом (рис. 6) измеряли полный вектор скорости в точке по трем его компонентам путем измерения давлений в отверстиях чувствительной головки зонда и последующего пересчета по определенному алгоритму
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