Secondary thermal barrier for the main circulation pump of nuclear power plant primary circuit and method of modifying that pump by making use of the barrier

摘要

The secondary thermal barrier for the main circulation pump of nuclear power plant primary circuit is arranged between the cooled upper side of a diffusion ring and the snail shell and comprises at least one lower base (1) in the form of an annulus, wherein an internal height-compensation wall (3) and an external height-compensation wall (2) are attached to the lower base (1) internal and external circumferences, wherein the lower base (1) is made for mounting on a primary heat barrier (5) and both, the internal height-compensation wall (3) and the external height-compensation wall (2) are made for sealed connection with the snail shell. The method of modifying the main circulation pump of the nuclear power plant primary circuit for preventing occurrence of cracks in the diffusion ring flange and/or in the snail shell flange in the main parting plane of the pump, which the diffusion ring flange abuts, is characterized in that first, there are carried out shape modifications on the pressure flange of the main circulation pump main parting plane and namely at the point of possible occurrence of stress damages, particularly at points adjoining the attached flange of the diffusion ring, whereupon the space extending between the primary heat barrier and the main parting plane pressure flange is divided into at least three temperature-separated spaces by installing the secondary heat barrier. When making a repair work, first material containing indications is removed poor making the shape modifications.