The intravessel separator drums, which have an inner diameter of 2.3 m and were installed in all nuclear power plants with the first-generation RBMK-1000 reactors and at the third and fourth power-generating units of the Leningrad nuclear power plant, do not permit storing enough water so as to eliminate the danger of cutoff of the main circulation pumps (MCPs) when the emergency shielding is actuated at nominal power. The design intravessel devices do not give sufficiently uniform steam distribution over the width of the inserted perforated sheet and reliable operation of the. hydroseals when water is drained from the sheet. A break through the hydroseal and a local increase of the steam velocity over the width-of the inserted perforated sheet degrade the characteristics of the separator drums.One way to improve the reliability and safety of nuclear power plants with RBMK-1000 reactors is to update the intravessel drum separator units with an inner diameter of 2.3 m. This will make it possible to increase the store of water and will allow for long-time emergency cooldown of the steam generating channels through the steam-water pipelines in the case if the pipeline in the head part of the loop ruptures. This can be done by using, instead of the design coustruetion of the intravessel units, systems with a collector-type distribution of the steam-water mixture inside the separator drums, as shown in Fig. 1. These devices include transversely arranged perforated collectors with input pipes, each of which is connected with the corresponding connection to the steam-water pipeline. The perforated collectors, placed under the inserted perforated sheet, have 10 mm in diameter openings, placed in two rows at angles of 25 and 45 ~ with respect to the horizontal direction on both sides of its vertical axis. A nozzle insert is installed at the base of the input pipe, and a special drainage opening is made, through which the steam-generating channels will be cooled by a back flow of water from the separator drums in the case of an accident with rupture of the pipeline in the head part of the multiple forced-circulation loop (MFCL). During normal operation, on account of the rarefaction produced by the nozzle, water from the water volume of the separator is constantly fed through the above-mentioned opening and therefore it is impossible for steam to enter the channel directly from the steam-water pipelines. The diameter of the opening is chosen according to the water flow rate required for emergency cooling of the channel. Components of the design construction, such as the inserted perforated sheet and the perforated cover shield, are left in the reconstructed intravessel units. The steam-water mixture is fed into the input pipes and then into the perforated collectors, after which preliminary distribution of steam and water occurs under the perforated sheet. The steam, together with the remaining water, flows through the opening through the perforated sheet into the steam volume, where it dries.To assess the outlook for the ...
