Patent Number: 053217314
Section: description

DETAILED DESCRIPTION OF THE INVENTION In order to appreciate the conventional wisdom of steam separator and dryer design, reference is made FIG. 1 which shows a simplified BWR generally at 10. BWR 10 may be seen to comprise a reactor pressure vessel (RPV), 12, configured to admit feedwater via a feedwater inlet, 14, and to exhaust steam via a steam outlet, 16, thus providing for the ultimate operation of the BWR. A nuclear core, 18, is provided and is disposed within a core shroud, 20. Core shroud 20 and RPV 12 define a core annulus region, 22, through which sub-cooled water flowing downwardly through a downcomer region, 24, may enter a core lower plenum region identified at 26 before flowing through core 18. A water and steam mixture exits core 18 and flows into a core upper plenum region identified at 28, which is defined by a shroud head, 30, disposed atop core 18. From core upper plenum 28, the two-phase mixture enters a plurality of standpipes, 32, which, together with RPV 12, define downcomer region 24. Standpipes 32 are disposed atop shroud head 30 and extend in fluid communication between core upper plenum 28 and a corresponding number of individual steam separators, 34. Steam separators 34 have outlet communications for water separated from the two-phase mixture flowing therethrough to enter downcomer region 24. The separated water in downcomer region 24 combines with the feedwater entering from inlet 14 to provide an accumulation of water for continuous and endless flow through core 18. A representative water level is shown at 36. Steam separators 34 also have outlet communications for wet steam to pass into a wet steam plenum region identified at 38. Conventionally, a separate dryer assembly, 40, is provided having inlets, 42, in fluid communication with wet steam plenum 38. The collective steam throughput of steam separators 34 is, accordingly, passed into wet steam plenum 38 and then, via inlets 42, into dryer assembly 40. Water removed from the steam is returned to downcomer region 24 via drains, 44. The dried steam, essentially water-free, is passed via outlets, 46, into a steam dome region, identified at 48, to be withdrawn from RPV 12 via steam outlet 16. A wall, 45, separates dryer assembly 40 and steam dome region 48 from wet steam plenum 38. Looking now to FIG. 2, the instant, inventive modular steam separator with integrated dryer is shown generally at 50 as a steam separator, 54, having an integrated steam dryer, 56. Steam separator 54, for example, may be of a conventional centrifugal type. See U.S. Pat. No. 3,902,876 and Wolf et al., "Advances in Steam-Water Separators for Boiling Water Reactors", ASME Paper No. 73-WA/Pwr-4, November 1973. Steam dryer 56, for example, may have internal vanes. Modular steam separator with integrated dryer 50 may be especially adapted for employment in either forced or natural circulation BWRs such as, for example, conventional BWRs, the advanced BWR (ABWR), and the simplified BWR (SBWR). Reactor internals, construction and operation are well known in the art, such as illustrated by reference to the following publications: Glasstone and Sesonske, Nuclear Reactor Engineering, pp. 748-753, 3d Edition, VanNostrand, Reinholt (New York, N.Y., 1981); Wolfe and Wilkens, "Improvements in Boiling Water Reactor Designs and Safety", presented at the American Nuclear Society Topical Meeting, Seattle, Wash., May 1-5, 1988; Duncan and McCandless, "An Advanced Simplified Boiling Water Reactor", presented at the American Nuclear Society Topical Meeting, Seattle, Wash., May 1-5, 1988; and Lahey and Moody, The Thermal Hydraulics of a Boiling Water Nuclear Reactor, especially Chapter 2, pp. 15-44, American Nuclear Society (LeGrange Park, Ill. 1977). Conventional BWRs, the ABWR and the SBWR all are described and discussed in the foregoing references, each of which is expressly incorporated herein by reference. Advantageously, a multiplicity of modular steam separators with integrated dryers 50 may be incorporated into a BWR, thereby eliminating the need for a wet steam plenum, and discrete steam separator and dryer components. The incorporation of modular steam separator with integrated dryer 50 into a BWR may be effected by connecting the proximal end of standpipe 58 of steam separator 54 to an outlet in core upper plenum 60. Core upper plenum 60 may be seen to be defined by shroud head 61 of core shroud 65. A two-phase water and steam mixture, 62, formed from the passage of feedwater and recycled coolant in heat transport relationship with the reactor core may be passed into steam separator 54 from core upper plenum 60 via standpipe 58. As water and steam mixture 62 is transported through barrel 64 of steam separator 54, a helical motion may be imparted thereto by an inlet swirler positioned at the proximal end of barrel 64 for the purpose of generating centrifugal forces to effect separation of the entrained water from the steam. As a result of the helical motion imparted to water and steam mixture 62 by the inlet swirler, a portion of the denser water phase, 66, of water and steam mixture 62 is directed to vanes 68a-c in each of three representative stages of steam separator 54. In each of the representative stages shown, separated water phase 66 is removed form barrel 64 via, respectively, pickoff rings 70a-c and is passed via annuli 72a-c into downcomer region 74 for addition to the feedwater of the reactor via core annulus 75 which is defined by the region bounded by shroud 65 and reactor pressure vessel 77. Annuli 72a-c are formed within the regions bounded by outer skirts 76a-c and vanes 68a-c. To prevent any entrained steam separated by a free surface separation mechanism from water phase 66 from bypassing steam dryer 56, steam connection 73 is provided for its passage to steam dryer 56 via barrel 64. Separated steam phase 78 is passed from the distal end of steam separator 54 into steam dryer 56 via a steam inlet distribution channel, 80. Preferably, steam inlet distribution channel 80 decreases in cross-sectional area as it extends in fluid communication from barrel 64 into dryer 56. Within dryer 56, any unseparated water, 82, is removed from steam phase 78 and is passed into downcomer region 74 via dryer drain 84. Drain 84 may be seen to extend below water level 85 for addition of unseparated water 82 to the feedwater of the reactor via core annulus 75. Dried steam phase 90, now essentially moisture-free, is passed via vent 86 into steam dome region 88 for ultimate use as the working fluid for a turbine used, for example, in the generation of electric power. A wall, 76, separates steam dome region 88 from downcomer region 74. Preferably, vent 86 increases in cross-sectional area as it extends away from steam dryer 56. Regarding materials of construction, preferably all components are manufactured from materials appropriate for their use within a nuclear BWR. Since certain modification can be made in accordance with the precepts of the present invention, the description herein is illustrative rather than limitative.