FR2995628A1 - STEAM ENERGY CONVERSION CYCLE PRODUCED BY A SODIUM-COOLED QUICK-SOURCE REACTOR - Google Patents

Abstract

The present invention relates to a steam energy conversion cycle produced by a sodium-cooled fast neutron reactor, having a first stage, in which a first expansion of the steam from an associated steam generator (2) is carried out. to the reactor (1) to return it from a "fossil cycle" start state (21) to an intermediate state of temperature and vapor pressure corresponding to a "nuclear cycle" start state (22), a second a step in which a second expansion of the steam from the intermediate state (22) is carried out until a vapor is obtained in a first wet state (23) under the steam saturation curve (S), a third step in wherein the steam is dried and superheated, and a fourth step in which a third expansion of the steam is performed from its superheated state (24) to a second wet state (25).

Description

The present invention relates to a conversion cycle of the energy provided by a sodium cooled fast neutron reactor (known as sodium RNR).

It relates to a nuclear facility that includes at least one nuclear reactor, a steam generator, steam turbines, and a dryer and / or superheater. The assembly is traversed by gaseous or liquid water which circulates in a closed circuit and which is subjected to temperature and pressure variations. The term "cycle" refers to variations in the temperature and pressure of the gaseous or liquid water between its exit from the steam generator and its return to the steam generator. In order to obtain better cycle yields, the use of a sodium-cooled fast neutron reactor is advantageous. However, the temperature and pressure values at the outlet of a sodium cooled fast neutron reactor are much higher than those generally encountered in a "nuclear cycle", and are close to those generally encountered in a "fossil cycle". A "nuclear cycle" corresponds to the temperature and pressure variations generally encountered in a nuclear installation that usually operates with steam at the outlet of the steam generator close to the saturation curve.

A "fossil cycle" corresponds to the temperature and pressure variations generally encountered in thermal power plants using combustion boilers.

The sodium-cooled fast neutron reactor of the French Phénix RNR plant presents steam turbine technologies that allow operation with steam working under conditions of temperature and pressure close to those encountered in a "fossil cycle" and which allow Steam to relax during its passage in a high-pressure turbine and a medium-pressure turbine under dry steam conditions. It is necessary that the temperature and pressure conditions in the various components of the installation, including the turbines and the superheater, are not too high in order to achieve lifetimes of the order of 60 years. lower temperatures reduce the creep risks of the various components. In this context, the present invention aims to provide a steam energy conversion cycle produced by a sodium cooled fast neutron reactor, improving the life of the equipment. To this end, the cycle according to the invention for converting energy by steam produced by a sodium-cooled fast neutron reactor is remarkable in that it has: a first stage, in which a first expansion of steam from a steam generator associated with the reactor to return it from a "fossil cycle" start state to an intermediate state of temperature and vapor pressure corresponding to a "nuclear cycle" start state, a second step in which a second expansion of the steam from the intermediate state is carried out until a vapor is obtained in a first wet state under the steam saturation curve; a third step in which the steam is dried and 10 the steam is superheated from its first wet state to a state of drying and overheating above the saturation curve, and - a fourth step in lacquer A third expansion of the steam is carried out from its superheated state to a second wet state below the steam saturation curve, the steam then being condensed and fed back to the steam generator. The sodium-cooled fast neutron reactor cycle according to the invention is located more in the saturated vapor zone than the cycles of the state-of-the-art sodium cooled fast neutron reactors, while working with the same temperature and pressure conditions directly at the outlet of the steam generator that are close to those encountered in thermal power plants. The cycle according to the invention makes it possible to increase the yield relative to that obtained with the sodium-cooled fast neutron reactor of the French Phenix RNR plant.

It can be used for reactors of high electrical power up to classes above 1500 MWe. The invention makes it possible to use a sodium-cooled fast neutron reactor with standard components currently used for fossil or nuclear plants. The invention thus makes it possible to avoid making superheaters on the model of those used for the sodium-cooled fast neutron reactor of the French RNR plants, which are difficult to design and expensive to manufacture. The vapor in its "fossil cycle" starting state is at a pressure of between 150 and 200 bar and at a temperature of between 450 and 570 ° C. The intermediate state is defined for a pressure between 30 and 50 bar and a temperature between 234 and 300 ° C. The steam in its first wet state is at a temperature between 152 and 188 ° C and a pressure between 5 and 12 bar after the second expansion. The steam in its state of drying and overheating is at a temperature between 215 and 255 ° C and a pressure between 5 and 12 bar. The vapor in its final state is condensed at a temperature which depends on the cold source used. The present invention also relates to a steam turbine plant comprising a sodium-cooled fast neutron nuclear reactor, for the implementation of a previously defined cycle and: at least one steam generator, a very high pressure turbine / high temperature connected to the steam generator of the nuclear reactor, in which a first expansion of the steam from the reactor steam generator is carried out to bring it back from a starting state of "fossil cycle" to an intermediate temperature state and steam pressure corresponding to a "nuclear cycle" starting state, - an intermediate turbine connected to the very high-pressure / high-temperature turbine and operating in part in saturated steam, in which a second expansion of the turbine is carried out; steam from the intermediate state until a vapor is obtained in a first wet state below the saturation curve steaming, - a dryer and a superheater connected to the intermediate turbine, in which the steam is dried from its first wet state and then overheated to a state of drying and overheating above the saturation curve, and - output turbines connected to the dryer and the superheater, in which a third expansion of the steam is carried out from its superheated state to a second wet state, the steam then being condensed and redirected to the generator of steam.

Advantageously, a pipe connecting the outlet of the very high pressure turbine and the superheater allows a sample of heating steam downstream of the very high pressure turbine which is used by the superheater.

The intermediate turbine is a high pressure turbine and the output turbines are either medium and low pressure turbines or low pressure turbines alone. The low-pressure turbines are fed in parallel. The high pressure turbine and the medium pressure turbine (when it exists in the second embodiment) are arranged in a combined body. The very high pressure / high temperature turbine and the intermediate turbine are arranged to relax the steam from a fossil cycle start state at a pressure between 150 and 200 bar and at a temperature between 450 and 570 ° C. in a wet vapor state whose temperature is between 152 and 188 ° C and the pressure is between 5 and 12 bar after the first expansion and the second expansion. The dryer and the superheater allow the steam to pass from a first state of wet vapor having a temperature of between 152 and 188 ° C and a pressure of between 5 and 12 bars after the second expansion to a state of drying and overheating whose pressure is between 5 and 12 bar and the temperature is between 215 and 255 ° C. The very high pressure / high temperature turbine, the intermediate turbine, and the output turbines (without medium pressure turbine) rotate at the mains frequency, for example at 3000 rpm, an input shaft of an alternator that produces an electric power of less than 1200 MWe. The very high-pressure / high-temperature turbine, the intermediate turbine, and the output turbines (with medium-pressure turbine) drive in rotation at the half-frequency of the network, for example at 1500 rpm, an input shaft. an alternator that produces an electric power exceeding 1200 MWe. The invention will be better understood and its advantages will appear better on reading the following detailed description given for information only and in no way limitative, with reference to the appended figures. FIG. 1 schematically represents a first embodiment according to the invention of the fast neutron reactor cooled with sodium RNR. FIG. 2 schematically shows a second embodiment according to the invention of the sodium cooled fast neutron reactor RNR. FIG. 3 represents an enthalpic diagram, called a Mollier diagram, showing, on curve A, an example close to a part of the cycle used on the fast reacted fast neutron reactor RNR of the French plant of Phénix and, on curve B, an example of a part of the cycle according to the invention used on a fast neutron reactor cooled with sodium. The cycle according to the invention illustrated in FIG. 3 can be carried out by two different steam turbine plants, each of which has a sodium-cooled fast neutron reactor 1, 1 'which makes it possible to release energy in order to produce energy. steam in a steam generator 2, 2 ', a very high-pressure / high-temperature turbine 3, 3', an intermediate turbine 4, 3 ", and outlet turbines 5, 4 ', 5', these turbines being capable of rotating an input shaft 6a, 6a 'of an alternator 6, 6' 30 which produces electricity The very high-pressure / high-temperature turbine 3, 3 'is connected to one or more generators of steam 2, 2 'of the nuclear reactor 1, 1', by one or more pipes, and allows a first expansion of the steam to bring it back from a starting state of "fossil cycle" at the outlet of the steam generator 2, 2 'of reactor 1, 1' to an intermediate state of temper Ature and steam pressure characteristic of a "nuclear cycle" starting state. The valves V, V 'make it possible to regulate the flow rate of steam coming from the steam generator or generators 2, 2'. In the first embodiment illustrated in FIG. 1, the intermediate turbine is a high-pressure turbine 4 connected by a pipe to the very high-pressure / high-temperature turbine 3 and operating largely in saturated steam. The high-pressure turbine 4 makes it possible to carry out a second expansion of the steam from the intermediate state corresponding to a "nuclear cycle" starting state until obtaining a vapor in a first wet state under the saturation curve S The drying and overheating of the steam are then carried out by successively passing through a drier 7 physically separating the liquid water and the steam and then a superheater 8, these devices being situated in a pipe 12 between the high-pressure turbine 4 and Low-pressure turbines 5. The superheater 8 located downstream of the dryer 7 and upstream of the low-pressure turbines 5 and a sample taken on the steam leaving the very high-pressure / high-temperature turbine 3 make it possible to overheat the steam. to bring it into a superheated state above the saturation curve S. A line 13 connecting the output of the very high pressure turbine 3 and the superheater 8 makes it possible to Aliser this steam tapping downstream of the heated high pressure turbine 3 which is used by the superheater 8.

The two low-pressure turbines 5 supplied in parallel and connected to the dryer 7 and the superheater 8 via a pipe 12 make it possible to carry out a third expansion of the steam from its superheated state to a final state. It can be used more than two low-pressure turbines 5 to achieve this third relaxation. The water recovered at the level of the dryer 7 and the superheater 8 is returned to the cycle by pipes 11.

A device 9, 10 for condenser, heaters and pumps is used to return the condensed vapor to the steam generator 2, but is not described here and is known from the state of the art.

This installation can produce electrical powers of the order of 600 to 1200 MWe. In the second embodiment illustrated in FIG. 2, the intermediate turbine is a high-pressure turbine 3 "connected to the very high-pressure / high-temperature turbine 3 'by a pipe and operating largely in saturated steam. high-pressure 3,, makes it possible to carry out a second expansion of the steam from the intermediate state corresponding to a "nuclear cycle" start state until a vapor is obtained in a first wet state under the saturation curve S.

The drying and superheating of the steam are then performed by successively passing through a dryer 7 'physically separating the liquid water and the steam and a superheater 8', these devices being located in pipes between the high-pressure turbine 3 "and a medium-pressure turbine 4 'The superheater 8' downstream of the dryer 7 'and upstream of the medium-pressure turbine 4' and a sample taken on the steam leaving the very high pressure / high temperature turbine 3 'allow to superheat the steam to bring it into a superheated state above the saturation curve S. A pipe 13 'connecting the outlet of the very high pressure turbine 3' and the superheater 8 'allows this 15 sampling of heating vapor downstream of the super-high-pressure turbine 3 'used by the superheater 8' It is illustrated here in FIG. 2 that the high-pressure turbine 3 "and the medium-pressure turbine 4 'are arranged in one and the same combined body ed. The medium-pressure turbine 4 'and the two low-pressure turbines 5' fed in parallel and connected to the medium-pressure turbine 4 'via a pipe 12' make it possible to carry out a third expansion of the steam since its superheated state. up to 25 final state. It can be used more than two low-pressure turbines 5 'to achieve this third relaxation. The water recovered at the dryer 7 'and the superheater 8' is returned to the cycle by pipes 11 '. A condenser, heater and pump device 9 ', 10' is used to return the condensed vapor to the steam generator 2 ', but is not described here and is known from the state of the art. As illustrated in FIG. 3, a Mollier diagram represents, on the abscissa, the entropy and in ordinate, the enthalpy of a fluid. It allows to include changes in state of a fluid, depending on temperatures and pressures. Here the fluid is water and a saturation curve S of water is shown in this diagram. The saturation curve S corresponds to the limit between two domains, the water presenting, for a given entropy, in the form of dry vapor for the enthalpies greater than the enthalpy of the saturation curve S and of saturated vapor ( or wet vapor) for enthalpies less than the enthalpy of the saturation curve S. The name saturated dry steam is given in the state of water just on the saturation curve S. The water content of the steam As the enthalpy decreases, the moisture level increases until it reaches a titer of 1 when the entire vapor phase is condensed into liquid water. In other words, the saturation curve S delimits a saturated wet steam domain S2, with respect to a gaseous domain of dry and superheated steam S1. Curve A represents a cycle similar to that used on the fast reactor fast neutron reactor RNR of the French plant Phénix. Curve B represents a ring used on the RNR-cooled fast neutron reactor according to the invention.

In the cycle of the curve A of the state of the art, steam at the outlet of one or more steam generators of the reactor is at a temperature around 500 ° C. and at a pressure of about 180 ° C. bars.

After a first expansion in a very high-pressure turbine between points 11 and 12, the steam is at a temperature of the order of 250 ° C and at a pressure of about 30 bars. Then, the steam is superheated to point 13. Between points 12 and 13, the temperature increases from 250 ° C to 380 ° C, while the pressure remains generally constant of the order of 30 bars. The steam is then expanded to point 14 by a medium-pressure turbine. Between points 13 and 14 the pressure decreases from 30 bar to 5 bar and the temperature decreases from 380 ° C to 180 ° C. Then the steam is expanded to point 15 by low pressure turbines. A condenser and heat exchanger and pump systems are then used to reinject the condensed vapor into the steam generator (s) of the reactor. In a cycle according to the invention, as shown in FIG. 3, the steam at the outlet of the steam generator or generators 2, 2 'of the reactor 1, 1' is at a temperature of approximately 500 ° C. and a pressure of about 180 bar, this starting state being represented by the point 21 which coincides with the point 11. However, in a "nuclear cycle", the starting point is generally close to the saturation curve S.

A first expansion therefore reduces the steam which is at a temperature of 500 ° C. and at a pressure of 180 bar at point 21, to an intermediate state at a temperature and a pressure corresponding to point 22, characteristics close to the starting point of 'a traditional nuclear cycle'. The first expansion thus brings the steam from point 21 to point 22 corresponding to the "nuclear cycle" starting state, located above the saturation curve S. At point 22, the vapor is substantially at a temperature of 280 ° C. ° C and at a pressure of 40 bar in Figure 3. The steam is expanded between point 22 and point 23 where it is in a first wet state. At point 23, the steam is substantially at a temperature of 170 ° C and a pressure of 7 bar. The steam is dried and superheated from its first wet state at point 23 to a first dried and superheated state represented by point 24, the pressure remaining substantially constant. At point 24, the steam is substantially at a temperature of 240 ° C and a pressure of 7 bar. Then, the steam is expanded between point 24 and an end point 25. At point 25, the vapor is substantially at a temperature of 35 ° C and a pressure of 60 mbar. These values are given for illustrative purposes only and depend on the vapor conditions given from the hot source at point 21 and from the cold source at point 25.

For point 21, it may be provided that the vapor is at a temperature between 450 and 570 ° C and at a pressure between 150 and 200 bar in the starting state of "fossil cycle".

For point 22, it may be provided that the steam is at a temperature between 234 and 300 ° C and at a pressure between 30 and 50 bar after the first expansion. For point 23, it can be provided that the vapor, in the first wet state, is at a temperature between 152 and 188 ° C and a pressure between 5 and 12 bar after the second expansion. For point 24, after drying and overheating, it can be provided that the steam is at a temperature between 215 and 255 ° C and a pressure between 5 and 12 bar. For point 25, after the third expansion, the steam in the second wet state is condensed at a temperature which depends on the cold source used for the reactor.

Claims (15)

REVENDICATIONS1. Vapor energy conversion cycle produced by a sodium-cooled fast neutron reactor, characterized in that it has: a first stage, in which a first expansion of the steam from a steam generator ( 2) associated with the reactor (1) to return it from a "fossil cycle" start state (21) to an intermediate state of temperature and vapor pressure corresponding to a "nuclear cycle" start state (22) a second step in which a second expansion of the steam is carried out from the intermediate state (22) until obtaining a vapor in a first wet state (23) situated under the saturation curve of the vapor (S), a third step in which the steam is heated and superheated from its first wet state (23) to a drying and overheating state (24) above the saturation curve (S), and fourth step in laqu a third expansion of the steam is effected from its superheated state (24) to a second wet state (25) under the saturation curve of the vapor (S), the steam then being condensed and rerouted to the generator of steam. 2. Cycle according to claim 1, characterized in that the steam in its starting state of "fossil cycle" (21) is at a pressure between 150 and 200 bar and at a temperature between 450 and 570 ° C. 3. Cycle according to any one of claims 1 or 2, characterized in that the intermediate state (22) is defined for a pressure between 30 and 50 bar and a temperature between 234 and 300 ° C. 4. Cycle according to any one of claims 1 to 3, characterized in that the vapor in its first wet state (23) is at a temperature between 152 and 188 ° C and a pressure between 5 and 12 bar after the second relaxation. 5. Cycle according to any one of claims 1 to 4, characterized in that the steam in its state of drying and overheating (24) is at a temperature between 215 and 255 ° C and a pressure between 5 and 12 bars. 6. Cycle according to any one of claims 1 to 5, characterized in that the vapor in its final state (25) is condensed at a temperature 25 which depends on the cold source used. 7. A steam turbine plant comprising a sodium-cooled fast neutron nuclear reactor (1, 1 '), characterized in that it comprises, for implementing a cycle according to any one of claims 1 to to 6: - at least one steam generator (2, 2 '), a very high-pressure / high-temperature turbine (3, 3') connected to the steam generator (2, 2 ') of the nuclear reactor (1, 1 '), in which a first expansion of the steam from the steam generator (2, 2') of the reactor (1, 1 ') is carried out to return it from a starting state of "fossil cycle" (21) to at an intermediate state of temperature and vapor pressure corresponding to a "nuclear cycle" start state (22), - an intermediate turbine (4, 3 ") connected to the very high pressure / high temperature turbine (3) , 3 ') and operating in part in saturated steam, in which a second expansion of the steam is carried out from the int ermediaire (22) to obtain a vapor in a first wet state (23) located under the steam saturation curve (S), - a dryer (7, 7 ') and a superheater (8, 8') connected to the intermediate turbine (4, 3 "), in which the steam is dried from its first wet state (23) and then overheated to a state of drying and overheating (24) above the saturation curve (S), and - exit turbines (5, 4 ', 5') connected to the dryer (7,7 ') and the superheater (8,8'), in which a third expansion of the vapor from its superheated state (24) to a second wet state (25), the vapor then being condensed and rerouted to the steam generator (2, 2 '). Steam turbine plant according to Claim 7, characterized in that a line (13, 13 ') connecting the outlet of the very high pressure turbine (3, 3') and the superheater (8, 8 ') allows a sample of heating steam downstream of the very high pressure turbine (3, 3 ') which is used by the superheater (8, 8'). 9. Steam turbine plant according to claim 7 or 8, characterized in that the intermediate turbine is a high-pressure turbine (4) and the output turbines are low-pressure turbines (5) fed in parallel. Steam turbine plant according to claim 7 or 8, characterized in that the intermediate turbine has a high-pressure turbine (3 "), the output turbines have a medium-pressure turbine (4 ') and low turbines - pressure (5 ') fed in parallel. 11. Steam turbine plant according to claim 10, characterized in that the high pressure turbine (3 ") and the medium pressure turbine (4 ') are arranged in a combined body. 12. Steam turbine plant according to one of claims 7 to 11, characterized in that the very high-pressure / high-temperature turbine (3, 3 ') and the intermediate turbine (4, 3 ") are arranged in whereby the vapor is released from a fossil cycle start state (21) at a pressure of between 150 and 200 bar and at a temperature of 450 to 570 ° C at a wet vapor state (23) having a temperature is between 152 and 188 ° C and the pressure is between 5 and 12 bars after the first expansion and the second expansion. 13. Steam turbine plant according to one of claims 7 to 12, characterized in that the dryer (7, 7 ') and the superheater (8, 8') allow the steam to pass from a first state wet steam (23) having a temperature of from 152 to 188 ° C and a pressure of from 5 to 12 bar after the second expansion to a state of drying and overheating (24) whose pressure is between 5 and 12 bar and the temperature is between 215 and 255 ° C. 14. Steam turbine plant according to one of claims 7, 8, 9, 12, 13, characterized in that the very high-pressure / high-temperature turbine (3), the intermediate turbine (4), and the turbines output means (5) rotate in rotation at the mains frequency, an input shaft of an alternator (6) which produces an electric power of less than 1200 MWe. 15. Steam turbine plant according to one of claims 7, 8, 10, 11, 12, 13, characterized in that the very high-pressure / high-temperature turbine (3 '), the intermediate turbine (3 ") ), and the output turbines (4 ', 5') rotate at the half-frequency of the network an input shaft of an alternator (6 ') which produces an electric power greater than 1200 MWe.