PATENT SPECIFICATION <n) 1421907 (21) Application No. 39315/72 (22) Filed 23 Aug. 1972 (19) O ON (23) Complete Specification filed 13 Aug. 1973 (44) Complete Specification published 21 Jan. 1976 H (51) INT. CL.8 F22G 5/18 F22B 1/06 (52) Index at acceptance H F4A 8C Gil G19 G20 (72) Inventors: ANTHONY RANDLE LUNT and THOMAS DAVID ROBERTS (54) STEAM GENERATING PLANTS (71) We, UNITED KINGDOM ATOMIC superheater 2 for heat exchange with liquid ENERGY AUTHORITY LONDON, a British sodium. The liquid sodium is supplied from a Authority do hereby declare the invention, sodium cooled nuclear reactor which also is 50 for which we pray that a patent may be not shown as it forms no part of the present 5 grantedjjto us, and the method by which it is to invention. Between the steam drum 1 and the be performed, to be particularly described superheater 2 there is an injector 3 which is in and by the following statement:— connected by a branch line 4 to the outlet 5 This invention relates to steam generating of the superheater. The outlet 5 is also con- 55 plants. nected to a turbine stop valve (not shown). 10 In one known construction of steam gen- The branch line includes a control valve 6. erating plant wet steam is separated from the Referring now to Figure 2 the injector 3 liquid phase in a steam drum and the wet comprises a housing 7 having a nozzle 8 and steam is fed to a superheater constructed from a diffuser 9. The nozzle 8 is connected to the 60 stainless steel and through which liquid metal steam drum 1 whilst the diffuser 9 is con- 15 is passed in heat exchange with the steam. In nected to the superheater 2. The housing 7 the event that water droplets suspended has an inlet port 10 which is connected to the within the wet steam are carried into the branch line 4. stainless steel superheater there is a grave risk In use, relatively wet steam flows from the 65 that stress-corrosion will occur and, sub- steam drum through the nozzle 8. The pressure 20 sequently, this corrosion could prove hazard- at the nozzle exit is lower than the pressure at ous by enabling steam to come into contact the superheater outlet and this causes a frac- with the liquid metal. tion of the superheated steam leaving the According to the invention in a steam superheater to be recirculated to the wet 70 generating plant having a stainless steel super- steam flow by way of the branch line 4 and 25 heater for effecting heat exchange between housing 7. The superheat of the re-circulated liquid metal and steam, there is means for fraction provides latent heat for evaporating recirculating a fraction of the superheated water droplets in the wet steam leaving the steam leaving the superheater to the inlet side nozzle 8. The construction thereby provides 75 of the superheater to provide latent heat for that the superheater receives steam which is 30 evaporating water droplets in the wet steam. substantially free from water droplets and In a preferred construction of steam thereby subject to lower stress-corrosion. generating plant the means for recirculating a WHAT WE CLAIM IS:— fraction of the superheated steam comprises 1. A steam generating plant having a 80 an injector in the wet steam supply line to the stainless steel superheater for effecting heat 35 superheater and connected to receive a exchange between liquid metal and steam, and fraction of the superheated steam from the means for recirculating a fraction of the outlet of the superheater. superheated steam leaving the superheater A construction of steam generating plant to the inlet side of the superheater to provide 85 according to the invention is described, by latent heat for evaporating water droplets in 40 way of example, with reference to the dia- the wet steam. grammatic drawings accompanying the Pro- 2. A steam generating plant according to visional Specification wherein:— claim 1 wherein the means for recirculating a Figure 1 is a flow diagram, and fraction of the superheated steam comprises- 90 Figure 2 is an injector. an injector in the wet steam supply line to the 45 Referring to Figure 1, a steam drum receives superheater and connected to receive a frac- two phase water coolant from an evaporator tion of the superheated steam from the outlet (which is not shown) and is connected to a of the superheater. 1,421,907 2 3. A steam generating plant substantially L. A. DUNNHILL, as hereinbefore described with reference to , , n , , , * the drawings accompanying the Provisional Chartered Patent Agent. Specification. Agent for the Applicants. Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon), Ltd.—1976. Published at The Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained. 1419073 PROVISIONAL SPECIFICATION 1 SHEET drawing is a reproduction of the Original on a reduced scale FIG. I j- JVWWWW- jvw/vwwwj FIG. 2. .