KR20140037778A - Energy conversion cycle for the steam produced by a sodium-cooled fast neutron reactor - Google Patents

Abstract

The present invention relates to an energy conversion cycle for the stem which is produced by a sodium-cooled fast neutron reactor having; a first stage which is performed so that a first expansion of the steam from a steam generator (2) with regard to a neutron reactor induces the steam to an intermediate state of temperature and pressure corresponding to a″nucleus cycle″ initial state (22) from a ″fossil fuel cycle″ initial state (21); a second stage in which a second expansion of the steam from the intermediate state (22) is performed till the steam of a first wetting state (23) located under a steam saturation curve (S) is obtained; a third stage in which the steam is dried and over-heated; and a fourth stage in which a third expansion of the steam is performed from an overheating state (24) to a second wetting state (25). [Reference numerals] (AA) Enthalpy (kJ/kg); (BB) Entropy (kJ/kg/K)

Description

ENERGY CONVERSION CYCLE FOR THE STEAM PRODUCED BY A SODIUM-COOLED FAST NEUTRON REACTOR}

The present invention relates to an energy conversion cycle for converting energy supplied by sodium cooled fast neutrons (so-called sodium fast neutrons-FNR).

The present invention relates to a nuclear plant comprising at least a reactor, a steam generator, a steam turbine and a dryer and / or a superheater.

Gas or liquid water circulates through the unit in a closed circuit and is subject to variations in temperature and pressure.

The term "cycle" refers to the change in temperature and pressure of a gas or liquid water between an outlet of a steam generator and its return into the steam generator.

To achieve the best cycle efficiency, use as sodium cooled fast neutrons is advantageous.

However, the temperature and pressure values at the outlet from the sodium cooled fast neutron are much higher than those normally encountered in the "nuclear cycle" and approach those commonly encountered in the "fossil fuel cycle".

The "nuclear cycle" generally corresponds to the change in temperature and pressure encountered in a nuclear plant operating with steam coming from the steam generator's outlet, the steam approaching a saturation curve.

The "fossil fuel cycle" corresponds to the changes in temperature and pressure commonly encountered in thermal power stations using fossil fuel fired boilers.

The sodium-cooled fast neutron reactor (FNR) in the French Pheonix power station enables operation with steam operating at temperature and pressure conditions close to those encountered in "fossil fuel cycles", thereby reducing the dry steam conditions. Steam turbine technology is used to allow steam to expand when passing through high and medium pressure turbines.

The different components of the plant, ie the temperature and pressure conditions in the turbine and superheater, should not be too high to have a working life of around 60 years.

Low temperatures reduce the risk of creep in different components.

In this regard, the subject of the present invention is an energy conversion cycle for steam produced by sodium cooled fast neutrons which improves the life of the equipment.

To do this, the energy conversion cycle for the steam produced by the sodium cooled fast neutron of the present invention is

A first expansion of the steam coming from the steam generator associated with the neutron to carry out the steam from the "fossil fuel cycle" initial state to an intermediate state of the temperature and pressure of the steam corresponding to the "nuclear cycle" initial state stage,

A second stage in which the second expansion of the steam from the intermediate state is carried out until a first wet state vapor is obtained which is located below the vapor saturation curve,

A third stage wherein the steam is dried from its first wet state and superheated to lead the steam to a dry and superheated state located above the saturation curve, and

A third expansion of the steam is carried out from its superheated state to a second wet state located below the steam saturation curve, the steam having a fourth stage which is then condensed and led back to the steam generator.

The cycle to sodium cooled fast neutrons as claimed in the present invention is located in the zone of saturated steam more than the cycle to sodium cooled fast neutrons of the prior art while operating at the same temperature and pressure conditions directly at the outlet of the steam generator, This condition is close to those encountered at thermal power stations.

The cycle as claimed in the present invention results in increased efficiency compared to what is currently obtained with sodium fast neutron (FNR) power stations in French Phoenix.

This cycle can be used for high power neutrons up to a class above 1500 MWe.

The present invention allows sodium cooled high speed neutrons to be used with standard components currently used for fossil fuels or nuclear power stations.

Thus, the present invention makes it possible to avoid the implementation of superheaters such as those used for French sodium cooled fast neutron (FNR) power stations, which are difficult to design and expensive to manufacture.

The steam is at a pressure comprised between 150 and 200 bar and a temperature comprised between 450 and 570 ° C. in its initial state of “fossil fuel cycle”.

The intermediate state is defined for the pressure comprised between 30 and 50 bar and the temperature comprised between 234 and 300 ° C.

The vapor in its first wet state is at a temperature comprised between 152-188 ° C. and a pressure comprised between 5-12 bar after the second expansion.

The steam in its dry and superheated state is at a temperature comprised between 215 and 255 ° C. and a pressure comprised between 5 and 12 bar.

In its final state the vapor condenses at a temperature depending on the cooling source used.

The invention also relates to a steam turbine installation comprising sodium cooled high speed neutron reactors, for the implementation of the cycles defined above,

At least one steam generator,

An ultrahigh pressure / high temperature turbine connected to a steam generator to a neutron furnace, wherein the temperature and pressure of the steam in which the first expansion of the steam from the steam generator into the neutron corresponds to the "nuclear cycle" initial state from the "fossil fuel cycle" initial state; Ultra-high pressure / high temperature turbine, which is carried out to induce steam to an intermediate state of

An intermediate turbine, connected to an ultrahigh pressure / high temperature turbine and partially operating with saturated steam, wherein the second expansion of the steam is carried out from the intermediate state until a first wet state vapor is obtained, located below the steam saturation curve; turbine,

A dryer and superheater connected to the intermediate turbine, wherein the steam is dried from its first wet state and then superheated to lead the steam to a dry and superheated state located above the saturation curve, and

An outlet turbine connected to the dryer and the superheater, wherein a third expansion of the steam is carried out from its superheat state to the second wet state, where the steam is subsequently condensed and directed back to the steam generator. will be.

Advantageously, the pipe connecting the outlet and superheater from the ultrahigh pressure turbine causes the heated steam to be discharged downstream of the ultrahigh pressure turbine, which steam is used by the superheater.

The intermediate turbine is a high pressure turbine and the outlet turbine is a medium and low pressure turbine or just a low pressure turbine. Low pressure turbines are fed in parallel.

The high pressure turbine and the medium pressure turbine (when this is present in the second embodiment) are arranged in combined units.

The ultrahigh pressure / high temperature turbine and the intermediate turbine have a temperature between 152 and 188 ° C. after the first expansion and the second expansion from the fossil fuel cycle initial state at a pressure comprised between 150 and 200 bar and a temperature between 450 and 570 ° C. The pressure is arranged to expand the steam to a wet steam state comprised between 5 and 12 bar.

The dryer and superheater have a pressure between 5 and 12 bar and a temperature between 215 and 255 ° C. from the initial wet steam state after which the temperature is between 152 and 188 ° C. and the pressure is between 5 and 12 bar after the second expansion. Allows steam to pass through in a dry and superheated state.

Ultrahigh / high temperature turbines, intermediate turbines and outlet turbines (without medium pressure turbines) rotate the alternator input shafts producing less than 1200 MWe of power at network frequencies, for example at 3000 rpm.

Ultrahigh / high temperature turbines, intermediate turbines and outlet turbines (with intermediate pressure turbines) rotate alternator input shafts that produce more than 1200 MWe of power at half the network frequency, for example at 1500 rpm.

The invention will be better understood and the advantages thereof will become more apparent by reading the following detailed description, given as a non-limiting example, with reference to the accompanying drawings.

1 schematically illustrates a first embodiment as claimed in the present invention of sodium cooled fast neutron furnace (FNR).
FIG. 2 shows schematically a second embodiment as claimed in the present invention of sodium cooled fast neutron reactor (FNR).
3 shows an example close to the portion of the cycle used for sodium cooled fast neutron furnace (FNR) of a French Phoenix power station in curve A, of the cycle as claimed in the invention used for sodium cooled fast neutron furnace in curve B. An enthalpy diagram, also called the Mollier diagram, showing an example of the portion.

The cycle as claimed in the present invention as shown in FIG. 3 is a sodium cooled fast neutron (1, 1 '), ultra-high pressure / high temperature, which allows energy to be released to produce steam in the steam generator (2, 2'). It can be implemented by two different steam turbine installations presenting the turbines 3, 3 ', the intermediate turbines 4, 3 "and the outlet turbines 5, 4', 5 ', respectively. It is suitable for rotating the input shafts 6a, 6a 'of the alternators 6, 6' that it produces.

The ultra high pressure / high temperature turbines 3, 3 ′ are connected to one or a plurality of steam generators 2, 2 ′ of the neutrons 1, 1 ′ by one or a plurality of pipes and a first expansion of the steam is achieved. In the middle of the temperature and pressure of the steam, which is characteristic of the "nuclear cycle" initial state from the "fossil fuel cycle" initial state at the exit from the steam generators 2 and 2 'of the neutron (1, 1'). To guide.

The valves V, V 'allow the flow rate of steam coming from the steam generator (s) 2, 2' to be adjusted.

In the first embodiment shown in FIG. 1, the intermediate turbine is a high pressure turbine 4 connected to an ultrahigh pressure / high temperature turbine 3 which is operated primarily by saturated steam.

The high pressure turbine 4 allows a second expansion of the steam from an intermediate state corresponding to the "nuclear cycle" initial state until steam is obtained in the first wet state under the saturation curve S.

Drying and overheating of the steam is then carried out by successively passing into a dryer 7 which physically separates the liquid water and steam and then into the superheater 8, these devices being connected between the high pressure turbine 4 and the low pressure turbine 5. Is located in the pipe 12.

The discharge of steam exiting the superheater 8 and the ultrahigh pressure / high temperature turbine 3 located downstream of the dryer 7 and upstream of the low pressure turbine 5 causes the steam to overheat resulting in overheating on the saturation curve S. To state. A pipe 13 connecting the outlet from the ultrahigh pressure turbine 3 and the superheater 8 causes the heated steam used by the superheater 8 downstream of the ultrahigh pressure turbine 3 to be discharged.

Two low-pressure turbines 5 fed in parallel and connected to the dryer 7 and the superheater 8 by a pipe 12 allow a third expansion of the steam from its superheated state to its final state. More than two low pressure turbines 5 can be used to perform this third expansion.

The water recovered from the dryer 7 and from the superheater 8 is again sent out in cycles by the pipe 11.

The systems 9, 10 of the condenser, reheater and pump are used to direct the condensed vapor into the steam generator 2 but are not described herein and are known from the prior art.

The plant generates power on the order of 600-1200 Mwe.

In the second embodiment shown in FIG. 2, the intermediate turbine is a high pressure turbine 3 ″ connected to an ultrahigh pressure / high temperature turbine 3 ′ which is operated primarily by saturated steam by pipes.

The high pressure turbine 3 "enables a second expansion of the steam from an intermediate state corresponding to the" nuclear cycle "initial state until steam is obtained in the first wet state below the saturation curve S.

Drying and superheating of the steam is then carried out by successively passing into a dryer 7 which physically separates the liquid water and steam and then into the superheater 8, these devices being connected to a high pressure turbine 3 "and a medium pressure turbine 4. ') Is located in the pipe between.

The discharge of steam exiting the superheater 8 'and the ultrahigh pressure / high temperature turbine 3' located downstream of the dryer 7 'and upstream of the intermediate pressure turbine 4' causes the steam to overheat, resulting in a saturation curve ( S) Induce the steam to the superheated state above.

A pipe 13 'connecting the outlet from the super high pressure turbine 3' and the superheater 8 'causes the heated steam downstream of the super high pressure turbine 3' used by the superheater 8 'to be discharged. .

The high pressure turbine 3 "and the medium pressure turbine 4 'are shown in Figure 2 as being arranged in a single combined unit.

The medium pressure turbine 4 'and two low pressure turbines 5' fed in parallel and connected to the medium pressure turbine 4 'by a pipe 12' have a third expansion of the steam from its superheated state to its final state. To be performed. More than two low pressure turbines 5 'can be used to perform this third expansion.

The water recovered from the superheater 8 'at the level of the dryer 7' is again sent out in cycles by the pipe 11 '.

The systems 9 'and 10' of the condenser, reheater and pump are used to direct the condensed vapor into the steam generator 2 ', but are not described herein and are known from the prior art.

As shown in FIG. 3, the Moliere plot represents entropy on the abscissa and enthalpy of the fluid on the ordinate.

In particular, this causes the fluid to change state as a function of temperature and pressure.

Here, the fluid is water and the saturation curve S of the water is shown in this diagram.

The saturation curve (S) corresponds to the limit between the two regions, and water forms the form of dry vapor for a given entropy, for an enthalpy greater than the enthalpy of the saturation curve (S), rather than the enthalpy of the saturation curve (S). It takes the form of saturated steam (or wet steam) for low enthalpy. The name of the dry saturated steam is given in the state of water just above the saturation curve (S). The water content of the wet steam increases as the enthalpy decreases until a water content of 1 is obtained when all vapor states condense to the liquid state.

In other words, the saturation curve S delimits the region of saturated wet steam S2 relative to the gas region of dry superheated steam S1.

Curve A represents a cycle similar to that used for the fast neutrons (FNR) of the French Phoenix Power Station.

Curve B represents the cycle used for sodium cooled fast neutron reactor (FNR) as claimed in the present invention.

In the cycle of curve A of the prior art, the steam coming from one or a plurality of steam generators to the neutrons is at a temperature of approximately 500 ° C. and a pressure of about 180 bar.

After the first expansion in the ultrahigh pressure turbine between points 11 and 12, the steam is at a temperature on the order of 250 ° C. and a pressure on the order of 30 bar.

The steam is then superheated to point 13. Between points 12 and 13, the temperature increases from 250 ° C. to 380 ° C., while the pressure remains constant throughout, on the order of 30 bar.

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.

The steam is then expanded to point 15 by the low pressure turbine.

The system of condenser and heat exchanger and pump allows the condensed steam to be reinjected into the steam generator or generators into the neutron.

In the cycle as claimed in the present invention, as shown in FIG. 3, steam coming from the neutron reactor 1, 1 ′ or generators 2, 2 ′ has a temperature of approximately 500 ° C. and approximately 180. At the pressure of bar, this initial state is shown by point 21 coinciding with point 11.

However, in the "nucleus cycle", the initial point is generally close to the saturation curve (S).

Thus, the first expansion leads the steam at a temperature of 500 ° C. and a pressure of 180 bar at point 21 to an intermediate state with a temperature and pressure corresponding to point 22 which is a characteristic close to the initial point of the “traditional nuclear cycle”.

Thus, the first expansion leads the vapor from point 21 to point 22 corresponding to the "nuclear cycle" initial state located above the saturation curve S.

At point 22 the steam is at a temperature of 280 ° C. and a pressure of 40 bar substantially in FIG. 3.

The vapor expands between point 22 and point 23 in the first wet state.

At point 23, the vapor is at a temperature of 170 ° C. and a pressure of 7 bar.

The steam is dried and overheated from its first wet state at point 23 to the first dry heated state represented by point 24, and the pressure remains substantially constant.

At point 24 the steam is at a temperature of 240 ° C. and a pressure of 7 bar.

The vapor then expands between point 24 and end point 25.

At point 25 the steam is at a temperature of substantially 35 ° C. and a pressure of 60 mbar.

These values are given by way of example only and depend on the steam conditions provided for the heat source at point 21 and the cooling source at point 25.

For point 21, the steam may be arranged to be at a temperature comprised between 450 and 570 ° C. and a pressure comprised between 150 and 200 bar in the “fossil fuel cycle” initial state.

For point 22, the steam may be arranged to be at a temperature comprised between 234 and 300 ° C. and a pressure comprised between 30 and 50 bar after the second expansion.

For point 23, the vapor may be arranged in the first wet state, after the second expansion, at a temperature comprised between 152 and 188 ° C. and a pressure comprised between 5 and 12 bar.

For point 24, after drying and superheating, the steam may be arranged to be at a temperature comprised between 215 and 255 ° C. and at a pressure comprised between 5 and 12 bar.

For point 25, the vapor condenses in the second wet state at a temperature that depends on the cooling source used for the neutrons after the third expansion.

Claims (15)

Energy conversion cycle for steam produced by sodium cooled high speed neutrons,
The intermediate of the temperature and pressure of the steam in which the first expansion of the steam coming from the steam generator 2 associated with the neutron furnace 1 corresponds to the "nuclear cycle" initial state from the "fossil fuel cycle" initial state 21. A first stage performed to direct the vapor to state 22,
A second stage in which a second expansion of the steam from the intermediate state 22 is carried out until a vapor of the first wet state 23 located below the steam saturation curve S is obtained,
A third stage in which the steam is dried from its first wet state 23 and overheated to direct the steam to a dry and superheated state 24 located above the saturation curve S, and
A third expansion of the steam is carried out from its superheated state 24 to a second wet state 25 located below the steam saturation curve S, which is then condensed and led back to the steam generator An energy conversion cycle with a fourth stage. 2. The energy conversion cycle according to claim 1, wherein in its "fossil fuel cycle" initial state (21) the steam is at a pressure comprised between 150 and 200 bar and at a temperature comprised between 450 and 570 ° C. The energy conversion cycle according to claim 1 or 2, wherein the intermediate state (22) is defined for a pressure comprised between 30 and 50 bar and a temperature comprised between 234 and 300 ° C. 4. The vapor according to claim 1, wherein in its first wet state 23 the steam is at a temperature comprised between 152 and 188 ° C. and a pressure comprised between 5 and 12 bar after the second expansion. Energy conversion cycle. The energy conversion cycle according to any one of claims 1 to 4, wherein in its dry and superheated state (24) the steam is at a temperature comprised between 215 and 255 ° C and a pressure comprised between 5 and 12 bar. The energy conversion cycle according to any one of claims 1 to 5, wherein in its final state (25) the steam is condensed at a temperature depending on the cooling source used. A steam turbine installation comprising sodium cooled high speed neutron furnaces (1, 1 '), the steam turbine being configured for the implementation of a cycle according to any one of claims 1 to 6,
At least steam generators 2, 2 ',
An ultrahigh pressure / high temperature turbine 3, 3 ′ connected to the steam generators 2, 2 ′ of the neutron furnaces 1, 1 ′, coming from the steam generators 2, 2 ′ of the neutron furnace 1. Wherein the first expansion of the steam is performed to direct the steam from an “fossil fuel cycle” initial state 21 to an intermediate state 22 of the temperature and pressure of the steam corresponding to the “nuclear cycle” initial state. High temperature turbines (3, 3 '),
An intermediate turbine 4, 3 ″ connected to the ultra high pressure / high temperature turbine 3, 3 ′ and partially operating with saturated steam, wherein the second expansion of the steam is located below the steam saturation curve S; The intermediate turbine 4, 3 ″, which is carried out from the intermediate state 22 until steam in a first wet state 23 is obtained,
A dryer 7, 7 ′ and a superheater 8, 8 ′ connected to the intermediate turbine 4, 3 ″, wherein the steam is dried from its first wet state 23 and then superheated to give the saturation curve ( The dryers 7, 7 ′ and the superheaters 8, 8 ′, which direct the steam to a dry and superheated state 24 located above S), and
Outlet turbines 5, 4 ′, 5 ′ connected to the dryer 7, 7 ′ and the superheater 8, 8 ′, wherein the third expansion of the steam is second from its superheated state 24. Steam turbine installation comprising the outlet turbines (5, 4 ', 5'), carried out to a wet state (25), wherein the steam is subsequently condensed and directed back to the steam generator (2, 2 '). 8. The ultra-high pressure turbine (3, 3 ') according to claim 7, wherein the steam heated by the pipes (13, 13') connecting the outlets of the ultra-high pressure turbines (3, 3 ') and the superheaters (8, 8') are heated. Steam turbine installation, the steam being used by the superheater (8, 8 '). 9. The steam turbine installation according to claim 7 or 8, wherein the intermediate turbine is a high pressure turbine (4) and the outlet turbines are low pressure turbines (5) fed in parallel. 9. The steam turbine installation according to claim 7 or 8, wherein the intermediate turbine is a high pressure turbine (3 ") and the outlet turbines are a medium pressure turbine (4 ') and low pressure turbines (5') fed in parallel. The steam turbine installation according to claim 10, wherein said high pressure turbine (3 ") and said medium pressure turbine (4 ') are arranged in a combined unit. 12. The turbine according to any one of claims 7 to 11, wherein the ultra high pressure / high temperature turbines 3, 3 'and the intermediate turbines 4, 3 "are at a pressure comprised between 150 and 200 bar and at 450 to 570 ° C. From the fossil fuel cycle initial state 21 at the included temperature to the wet steam state 23 after the first expansion and the second expansion, the temperature is comprised between 152 and 188 ° C. and the pressure is between 5 and 12 bar. A steam turbine installation arranged to expand the steam. 13. The dryer (7, 7 ') and the superheater (8, 8') have a temperature between 152 and 188 ° C after the second expansion and the pressure is increased according to any one of claims 7 to 12. Vapor to allow the steam to pass from an initial wet steam state 23 comprised between 5 and 12 bar to a dry and superheated state 24 whose pressure is included between 5 and 12 bar and whose temperature is between 215 and 255 ° C. Turbine fittings. 14. The ultrahigh pressure / high temperature turbine (3), the intermediate turbine (4) and the outlet turbines (5) according to any one of claims 7, 8, 9, 12 or 13. A steam turbine installation that rotates an alternator input shaft 6 that generates less than 1200 MWe of power at a network frequency. 14. The ultrahigh pressure / high temperature turbine 3 ', the intermediate turbine 3' and the outlet according to any one of claims 7, 8, 10, 11, 12 or 13. The turbines 4 ', 5' rotate the alternator input shaft 6 ', which generates more than 1200 MWe of power, at half the network frequency.

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