Leak detection system for a steam generator

Claim 1

In a steam generator having at least one tube sheet supported therewithin so as to extend transversely of the major axis of the steam generator, said tube sheet embodying a unitary construction operable to define the thickness thereof, said tube sheet having a multiplicity of tube holes formed through the thickness thereof, and a multiplicity of duplex tubes embodying a double wall form of construction each having one end thereof retained by welding in a corresponding one of said multiplicity of tube holes, the improvement comprising a leak detection system operable to detect the occurrence of a leak that could give rise to the commingling of a pair of operating fluids that desirably are designed to flow through the steam generator in fluid isolation one to the other as well as to provide a determination as to the probable source of the leak and the direction of flow of the leaking fluid, one of the pair of operating fluids that flow through the steam generator being at a pressure greater than the pressure of the other one of the pair of operating fluids that flow through the steam generator, said leak detection system comprising: a. interconnecting means establishing a fluidic interconnection between pairs of said multiplicity of tube holes; b. plenum means fluidically interconnecting selective ones of said interconnecting means so as to establish within said tube sheet a plurality of separate and independent fluidic circuits each isolated from all the others, said plenum means being filled with fluid having a different composition than either of the pair of operating fluids that are made to flow through the steam generator, the fluid of said plenum means having a pressure intermediate the pressures of the pair of operating fluids that flow through the steam generator, said plenum means forming a portion of the leakage path when a leak occurs such that the leaking fluid becomes commingled with the fluid filling said plenum means thereby causing a change to occur in the pressure and/or composition of the fluid filling said plenum means; c. instrument tube means connected in fluid flow relation with said plenum means, said instrument tube means being operative to receive from said plenum means information in fluidic form as to the occurrence of a change in the pressure and/or composition of the fluid filling said plenum means; and d. an instrumentation package fluidically interconnected with said instrument tube means and therethrough to said plenum means, said instrumentation package being operative to indicate from the information received in fluid form from said instrument tube means that when the pressure of the fluid in said plenum means is sensed to have decreased the leaking fluid is the lower pressure fluid flowing through the steam generator and the direction of flow of the leaking fluid is away from said plenum means, and to indicate that when the pressure of the fluid in said plenum means is sensed to have increased the leaking fluid is the higher pressure fluid flowing through the steam generator and the direction of flow of the leaking fluid is towards said plenum means.