Patent Number: 050892185
Section: claims

1. A water cooled nuclear reactor comprising a pressure vessel, a reactor core, a primary water coolant circuit, a pressurizer, the reactor core and at least a portion of the primary water coolant circuit being located in a pressure vessel, the primary water coolant circuit being arranged to cool the reactor core, the pressurizer having a diaphragm and a pressurizer pressure vessel, the diaphragm being movable and being sealingly secured to the pressurizer pressure vessel to divide the pressurizer pressure vessel into a first water space and a second fluid space, the second fluid space being arranged to contain a gas, and at least one surge port means which communicates between the pressurizer and the primary water coolant circuit to connect the first space of the pressurizer with the primary water coolant circuit, the diaphragm being movable so as to allow changes in the volume or pressure of the water in the first space of the pressurizer and the primary water coolant circuit, sealing means interconnecting and securing the diaphragm to said pressurizer pressure vessel to form a seal and for allowing relative movement between said diaphragm and said pressurizer pressure vessel. 2. A water cooled nuclear reactor as claimed in claim 1 in which the reactor core, the primary water coolant circuit and the pressurizer are arranged as an integral unit enclosed by an integral pressure vessel, at least one casing being located in the integral pressure vessel to substantially divide the integral pressure vessel into a first chamber and a second chamber, the pressurizer being located in the first chamber, the reactor core and the primary water coolant circuit being located in the second chamber. 3. A water cooled nuclear reactor comprising a pressure vessel, a reactor core, a primary water coolant circuit, a pressurizer, the reactor core and at least a portion of the primary water coolant circuit being located in a pressure vessel, the primary water coolant circuit being arranged to cool the reactor core, the presurizer having a diaphragm and a pressurizer pressure vessel, the diaphragm being movable and being sealingly secured to the pressurizer pressure vessel to divide the pressurizer pressure vessel into a first water space and a second fluid space, the second fluid space being arranged to contain a gas, and at least one surge port means which communicates between the pressurizer and the primary water coolant circuit to connect the first space of the pressurizer with the primary water coolant circuit, the diaphragm being movable so a to allow changes in the volume or pressure of the water in the first space of the pressurizer and the primary water coolant circuit, the reactor core, the primary water coolant circuit and the pressurizer being arranged as an integral unit enclosed by an integral pressure vessel, at least one casing being located in the integral pressure vessel to substantially divide the integral pressure vessel into a first chamber and a second chamber, the pressurizer being located in the first chamber, the reactor core and the primary water coolant circuit being located in the second chamber. 4. A water cooled nuclear reactor as claimed in claim 2 in which the casing divides the pressure vessel into a first vertically upper chamber and a second vertically lower chamber. 5. A water cooled nuclear reactor as claimed in claim 4 in which the casing comprises an annular member which extends downwards from the peripheral region thereof, the annular member being sealingly secured to the pressure vessel to form an annular lower portion of the first water space. 6. A water cooled nuclear reactor as claimed in claim 2 or 3 in which the casing comprises an annular member which is sealingly secured to and extends downwards from the pressure vessel, the annular member having the at least one surge port means at its lower end. 7. A water cooled nuclear reactor as claimed in claim 1 or 3 in which the diaphragm is sealingly secured to the pressure vessel by bellow means. 8. A water cooled nuclear reactor as claimed in claim 6 in which the diaphragm is sealingly secured to the casing by bellow means. 9. A water cooled nuclear reactor as claimed in claim 1 or 3 in which the diaphragm is spring loaded. 10. A water cooled nuclear reactor as claimed in claim 6 in which the bellow means comprises a spring. 11. A water cooled nuclear reactor as claimed in claim 1 or 3 in which the diaphragm has damper means. 12. A water cooled nuclear reactor as claimed in claim 11 in which the diaphragm has at least one rod and piston, the casing having at least one cylinder, the at least one rod and piston being arranged to move coaxially within the cylinder to damp oscillations of the diaphragm. 13. A water cooled nuclear reactor as claimed in claim 7 in which the bellow means are arranged to expand with an increase in the volume or pressure of the water. 14. A water cooled nuclear reactor as claimed in claim 7 in which the bellow means are arranged to contract with an increase in the volume or pressure of the water. 15. A water cooled nuclear reactor as claimed in claim 2 or 3 in which the reactor core is arranged in the lower region of the second chamber, the primary water coolant circuit comprising a riser passage to convey relatively hot water to a heat exchanger, and a downcomer passage to convey relatively cool water from the heat exchanger to the reactor core. 16. A water cooled nuclear reactor as claimed in claim 15 in which the riser passage is defined by a hollow cylindrical member, the downcomer passage being defined between the hollow cylindrical member and the pressure vessel. 17. A water cooled nuclear reactor as claimed in claim 15 in which the heat exchanger is positioned in an upper region of the downcomer passage. 18. A water cooled nuclear reactor as claimed in claim 6 in which the reactor core is positioned in the lower region of the second chamber, the primary water coolant circuit comprising a riser passage defined by a hollow cylindrical member to convey relatively hot water to a heat exchanger, and a downcomer passage defined between the hollow cylindrical member and the pressure vessel to convey relatively cool water from the heat exchanger to the reactor core. 19. A water cooled nuclear reactor as claimed in claim 18 in which the casing is positioned coaxially with the hollow cylindrical member, the casing extending downwards from the pressure vessel into the hollow cylindrical member. 20. A water cooled nuclear reactor as claimed in claim 1 or 3 in which the pressure vessel has a vent to inter-connect the second fluid space with atmosphere. 21. A water cooled nuclear reactor as claimed in claim 20 in which the vent has a relief valve and the space between the diaphragm and the relief valve is filled with a predetermined mass of gas. 22. A water cooled nuclear reactor as claimed in claim 1 or 3 in which the diaphragm is an elastic membrane. 23. A pressurizer for a water cooled nuclear reactor comprising a pressure vessel, a diaphragm, the diaphragm being movable and being sealingly secured to the pressure vessel to divide the pressure vessel into a first space and a second space, sealing means being provided to interconnect and secure said diaphragm to the pressure vessel to form a seal and to allow relative movement between the diaphragm and the pressure vessel, the first space being arranged to interconnect with the water cooled nuclear reactor for the supply of water therebetween, the second space being arranged to contain a gas, the diaphragm being movable so as to allow changes in the volume or pressure of the water in the first space of the pressurizer and the water cooled nuclear reactor. 24. A pressurizer for a water cooled nuclear reactor comprising a pressure vessel, a diaphragm, the diaphragm being movable and being sealingly secured to the pressure vessel to divide the pressure vessel into a first space and a second space, the first space being arranged to interconnect with a water cooled nuclear reactor for the supply of water therebetween, the second space being arranged to contain gas, the diaphragm being movable so as to allow changes in the volume or pressure of the water in the first space of the pressurizer and the water cooled nuclear reactor, said diaphragm being sealingly secured to the pressure vessel by bellows means. 25. A pressurizer as claimed in claim 23 in which the diaphragm is sealingly secured to the pressure vessel by bellow means. 26. A pressurizer as claimed in claim 23 or 24 in which the diaphragm is spring loaded. 27. A pressurizer as claimed in claim 25 in which the bellow means comprises a spring. 28. A pressurizer as claimed in claim 23 or 24 in which the diaphragm has damper means. 29. A pressurizer as claimed in claim 25 in which the bellow means are arranged to expand with an increase in the volume or pressure of the water. 30. A pressurizer as claimed in claim 25 in which the bellow means are arranged to contract with an increase in the volume or pressure of the water. 31. A pressurizer as claimed in claim 23 or 24 in which the pressure vessel has a vent to interconnect the second space with atmosphere. 32. A pressurizer as claimed in claim 31 in which the vent has a relief valve. 33. A pressurizer as claimed in claim 23 or 24 in which the diaphragm is an elastic membrane.