Patent Number: 
Section: claims

1. A system for regulating a liquid in a circuit, with the system comprising:a plug valve comprising at least one inlet and one outlet, the plug comprising an internal passage through which is intended to pass the liquid flowing from the inlet to the outlet of the valve when the valve is open at least partially,an expansion reservoir in communication with the liquid flowing in the circuit and intended to contain liquid and a compensating gas,wherein the plug comprises at least a part of an expansion channel which has at least one lateral opening located on a lateral face of the plug and which is conformed to provide in operation a communication between said lateral opening and the expansion reservoir, the valve being conformed in such a way that:at least when the valve is closed: the lateral opening is in direct communication with the liquid coming from the inlet or from the outlet of the valve;when the valve is partially open and when the valve is fully open, the lateral opening cooperates with an inner wall integral with a body of the valve in such a way as to form a conduit in communication on the one hand with the expansion reservoir and on the other hand with the internal passage. 2. The system according to claim 1, wherein the conduit opens on the one hand into the expansion reservoir and opens on the other hand into a space formed by a lower face of the plug and a bottom of the body of the valve, with this space being in communication with the internal passage by said part of the expansion channel, said part of the expansion channel being made in the plug. 3. The system according to claim 1, wherein the lateral opening is a recess, with the cooperation of the recess and the inner wall forming the conduit when the valve is open at least partially. 4. The system according to claim 2, wherein the lateral opening is a recess, with the cooperation of the recess and the inner wall forming the conduit when the valve is open at least partially and wherein the recess extends from the expansion reservoir to the lower face of the plug. 5. The system according to claim 1, wherein the plug is a spherical plug. 6. The system according to claim 1, wherein the plug is a cylindrical plug. 7. The system according to claim 6, wherein the conduit opens on the one hand into the expansion reservoir an opens on the other hand into a space formed by a lower face of the plug and a bottom of the body of the valve, with this space being in communication with the internal passage by a part of the expansion channel, said part of the expansion channel being made in the plug, the system being conformed in such a way that when the valve is open, the expansion reservoir communicates with the liquid passing through the valve solely through the recess, of said space and of the lower channel. 8. The system according to claim 1, wherein the inlet and the outlet of the valve form an angle between 130° and 180°. 9. The system according to claim 1, wherein the valve is a straight valve. 10. The system according to claim 1, wherein the inlet and the outlet of the valve forming an angle less than 130°. 11. The system according to claim 1, wherein the valve comprises a cover forming with the body an enclosure and wherein the expansion reservoir is housed in the enclosure. 12. The system according to claim 1, configured in such a way as to orient the direction of closing of the plug according to the direction of the circulation of the liquid in the circuit. 13. The system according to claim 1, wherein the plug is actuated by a control device comprising a reduction gear housed inside the expansion reservoir. 14. The system according to claim 13, wherein the reduction gear is immersed in the compensating gas. 15. The system according to claim 14, comprising an overflow in order to limit the level of liquid in the expansion reservoir and wherein the reduction gear is arranged above the overflow. 16. The system according to claim 15, comprising an aerator device arranged in the expansion reservoir, under the overflow and configured to break the jets of liquid coming from the expansion channel. 17. The system according to claim 13, comprising a thermal protection device housed inside the expansion reservoir and conformed to thermally insulate the reduction gear from the heat of the liquid. 18. The system according to claim 1, comprising a rotational guiding bearing of the plug and wherein the bearing is housed inside the expansion reservoir. 19. The system according to claim 18, configured in such a way that in operation the bearing is immersed in the liquid contained in the expansion reservoir. 20. The system according to claim 19, wherein the bearing comprises a passage allowing the free circulation of the liquid contained in the expansion reservoir through the bearing. 21. The system according to claim 1, wherein the valve is a throttle valve. 22. The system according to claim 1, wherein the plug is movable with respect to the expansion reservoir. 23. The system according to claim 1, wherein the expansion reservoir is vertically arranged higher than the plug. 24. The system according to claim 1, wherein the expansion reservoir surmounts the plug valve. 25. The system according to claim 1, wherein the expansion reservoir is fixed with respect to the body of the valve during the displacement of the plug valve. 26. The system according to claim 25, wherein the expansion reservoir is formed at least partially by the inner wall of the valve. 27. The system according to claim 26, wherein the expansion reservoir is connected to the valve by being arranged at a distance from the latter. 28. The system according to claim 1, wherein the valve comprises a cover, wherein the cover comprises an inner wall and wherein the expansion reservoir is formed by the inner walls of the body of the valve, by the inner wall of the cover and by an upper face of a body of the plug valve. 29. A circuit comprising the system according to claim 1 and a pump able to deliver in two opposite directions. 30. The circuit according to claim 29, wherein the plug comprises the expansion channel for the passing of the liquid opening into the inner passage of the plug in order to place in communication the expansion reservoir with the circuit, the circuit being configured in such a way as to orient the direction of closing of the plug according to the direction of the circulation of the liquid in the circuit. 31. The circuit according to claim 29, configured in such a way that, during the closing of the valve, the plug is turned in such a way that the expansion channel remains in communication with a portion of the circuit separating the valve from an inlet of the pump. 32. A method of using a system according to claim 1 comprising a step of providing the circuit with the liquid to be regulated, the liquid having a temperature greater than or equal to 350° C. 33. The method according to claim 32 wherein the liquid to be regulated is liquid sodium intended to provide for the heat transfer in a circuit of a sodium cooled nuclear reactor.