The sludge collector is a passive device located in the upper internals of a Pressurized Water Reactor (PWR) recirculating steam generator. The sludge collector’s function is to trap sludge, particulates of small size, i.e., diameters ranging from 1 micron to 64 microns, suspended in the secondary side recirculating flow and entrained from the feedwater inlet flow. Sludge present in the secondary fluid results in degraded thermal performance if deposited on the heat transfer tubing. Another significant contributor to tube degradation is the presence of loose parts in the steam generator. The loose parts weir is a separate passive device located around the sludge collector, which is expected to serve two main purposes: first, to act as a barrier to prevent any loose parts with relative larger size, i.e., greater than 1mm, in the upper internals region from reaching the tube bundle; second, to aid in directing more flow through the sludge collector and improving its efficiency. The loose parts weir is considered for installation in combination with the sludge collector for both new and existing steam generators. Inclusion of the loose parts weir significantly alters the flow field of the sludge collector and thus its performance. A computational fluid dynamics (CFD) study was performed utilizing CFX computer code [1] to explore the performance and interaction of the sludge collector and the loose parts weir. The numerical study results were used to optimize the sludge collector design (inlet and outlet holes sizes, internal configuration) and determine the best placement for the loose parts weir. Particle tracking simulation was also employed to track the path of sludge and loose parts. The sludge deposition on the plates of the collector and the entrapment of the relative larger particles due to the loose parts weir were observed.

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