Increasing the operational reliability of the collectors of PGV-1000,-1000M steam generators

The possibilities for lowering the tensile stresses acting in the zone of weld seam No. 111 are studied. Stresses above the yield point can arise in this zone during operation because of the presence of stress concentrators and deep ribs and cuts, formed when the steam generator is manufactured, on the inner surface of pockets in the collectors. The tensile stresses can be decreased without decreasing the pressure of the medium in the second loop by using mechanical compressing devices. A variant for producing a compressive stress on branch pipe Du 1200 using a collapsible ring is examined. The reliability of the unit attaching the coolant collector to the branch pipes of PGV-1000 in the zone of weld seam No. 111 can be increased by effectively removing deposits from the pockets. It is suggested that a mechanical compressing device be used to decrease the stresses on the inner surface of a pocket in the collector and to decrease the cycling damage in the region of weld seam No. 111. __________ Translated from Atomnaya énergiya, Vol. 108, No. 1, pp. 9–12, January, 2008.