of the evaporator in the first stage are heated by steam from a boiler or ..... Turbine. Reactor. Recuperator. Intercooler. HP Compressor. Precooler. Flash tank.
Apresentação oral Acta da conferência: ICAPP 2002 – International Conference on Advanced Power Plants, 10-13 Junho 2002, Florida USA
Optimal Coupling of a Nuclear Reactor and a Thermal Desalination Plant O. Asuar Alonsoa, B. Bielakb, L. Cinottic, J. R. Humphriesd, N. Martinse, L. Volpif, S. Nisan,f, G. Carusog, A. Navigliog 1
Abstract - The present study, performed in the framework of the EURODESAL Project (5 th EU FWP), deals with the analysis of the "optimum" coupling of a PWR and of a HTGR plant with a thermal desalination plant, based on the Multiple Effects process. The reference reactors are the AP600 and the PWR900 as Pressurized reactors and the GT-MHR as Gas reactor. The calculations performed show that there are several technical solutions allowing to couple PWRs and GRs to a ME desalination plant. The optimization criteria concern the technical feasibility of the coupling, producing the maximum quantity of fresh water at the lower cost, without unacceptable reduction of the electrical power produced and without undue health hazard for population.
I. INTRODUCTION
600 PWR), presenting enhanced safety features and cost advantages. Major objectives of the project are [2]: Coherent demonstration of the technical feasibility of nuclear desalination through the development of technical principles for optimum cogeneration of electricity and water and by exploring the unique capabilities of the innovative nuclear reactors and desalination technologies. Objective assessment of the competitiveness and sustainability of proposed solutions through comparison with fossil and renewable energy based solutions. Enlargement of the role of nuclear energy and of its increased public acceptance by meeting a fundamental human need, water.
The increasing potable water demand, the shortage of available water sources and the growth of environmental pollution are the main reasons for the rising interest in nuclear desalination [1]. With "nuclear seawater desalination" we mean the production of potable water from the seawater in an integrated facility in which both the nuclear reactor and the desalination systems are located in a common site with the sharing of common systems and facilities. The energy required by the desalination systems is supplied by the nuclear power plant. The heat energy required for distillation is taken from the steam cycle of the nuclear power plant, while electricity, which is required for all desalination processes, can be taken either from power plant or from electrical grid. The present work has been carried out in the framework of the EURODESAL Project (5th EU FWP). EURODESAL basically aims at investigating the technical and economic feasibility of seawater desalination with innovative nuclear reactors (e.g. the GT-MHR and the AP-
The present study was undertaken in the view of a renewed interest in nuclear desalination, with the main purpose of optimizing the coupling of a PWR and a HTGR plant to a thermal desalination plant, based on a wellknown thermal process, the Multiple Effect Desalination process. The nuclear reactors considered for the study are Pressurized Water Reactors AP600 and PWR900 and the
a
EMPRESARIOS AGRUPADOS INTERNACIONAL, SA (Spain); b FRAMATOME ANP (France); c ANSALDO Nucleare (Italy); d CANDESAL Technologies (Canada); e IRRADIARE (Portugal); f CEA, CEN Cadarache, DER/SERI (France); gUniversity of Rome "La Sapienza" - DINCE
1
Gas-cooled reactor GT-MHR. Data about the nominal thermal cycle of these three reactors have been provided by ANSALDO (AP600), CEA (PWR900) and FRAMATOME (GT-MHR). Two coupling schemes have been analyzed: Flash tank connected to the cooling loop of the condenser; Intermediate water loop. The analyses performed show that the flash loop scheme is the optimum solution for PWRs, and the intermediate water loop with the Heat Run Out scheme provides the better performance in coupling a GT-MHR to a MED plant.
Only a part of the sea water flowing through the tubes in the first stage is evaporated. The remaining feed water is fed to the second stage, where it is again sent to a tube bundle. These tubes are, in turn, heated by the steam created in the first container. This steam is condensed into a fresh water product, while giving up heat to evaporate a portion of the remaining sea water in the next effect. This process continues for several effects. A typical large plant includes from about 8 to 16 stages. MED plants are typically built in units of 2000 to 10000 m3/d. Some of the more recent plants have been built to operate with top temperatures (in the first stage) of about 70°C (which reduces the potential for scaling of sea water within the plant but in turn increases the need for an additional heat transfer area in the form of tubes). The study has been carried out considering two different process schemes for the MED desalination plant: the parallel configuration and the serial configuration. In the parallel scheme (fig. 1) the sea water, after preheating in the final condenser, is introduced at the same conditions in all the stages (or effects) of the plant. In the serial configuration (fig. 2) the sea water is preheated in all the stages with the exception of the first one (at higher temperature), where it receives heat from the heat source. The parallel configuration is characterized by a GOR (Gain Output Ratio, kg of distillate produced per kg of steam in the first effect) generally lower than in serial scheme, in particular for a number of stages greater than 4 or 5, and the difference increase with the number of stages of the plant. Therefore, for a limited number of stages, the parallel scheme is preferred, due to its simplicity and low plant cost.
II. DESALINATION PLANT The Multiple Effects Desalination process (MED) takes place in a series of stages and adopts the principle of creating a decreasing pressure in the various stages holding the water [3, 4]. This permits the sea water feed to undergo multiple boiling without supplying any additional heat after the first stage. In a MED plant, the sea water enters the first stage and is brought to boiling point, after being pre-heated in tubes. The sea water is either sprayed or otherwise distributed in a thin film over the surface of the evaporator tubes to promote rapid boiling and evaporation. The tubes of the evaporator in the first stage are heated by steam from a boiler or other source. The steam produced in a stage may be partially condensed on the external side of the tubes crossed by feed water flow, but mainly it is sent to the evaporator of the following stage, at lower pressure, where it provides heat for water boiling and evaporation.
Fig. 1 - MED process scheme (parallel configuration)
2
A make-up flow to the flash tank loop is the sea water or the pre-heated sea water from MED, depending on the operating temperatures of the scheme. The double barrier is assured by the steam generator and the condenser tubes. In the intermediate water loop scheme, the coolant transfers heat from the condenser or the coolers of the nuclear plant directly to the brine heater of the desalination plant. The brine heater is the first stage of the MED plant. The steam produced, after condensing inside the plant, is mixed with the distillate produced. In this case, for a PWR plant, there are three barriers between the primary coolant of the reactor and the distillate: the steam generator, the condenser and the brine heater.
Fig. 2 - MED process scheme (serial configuration)
III. COUPLING SCHEMES Two coupling schemes have been analyzed: a flash tank connected to the cooling loop of the condenser (fig. 3) and an intermediate water loop (fig. 4). In the first scheme, the rejected heat from the nuclear plant (through the condenser for PWRs or the pre-cooler and intercooler for GRs) is used to heat-up a coolant at a temperature as high as possible. Then the coolant is introduced in a flash chamber where a fraction of the flow evaporates. The steam produced is the heat source for the desalination plant. This steam, after condensing in the first stage of the MED plant, is mixed to the distillate produced, increasing the GOR of the plant.
Fig. 4 - Intermediate water loop scheme
IV. COUPLING THE PWR900 AND THE AP600 NUCLEAR REACTORS WITH A MED DESALINATION PLANT The thermodynamic nominal conditions in the condenser for the two reactors are summarized in Table I Table I - Condenser parameters [5]: PWR900 0.055 bar Pressure: 34.75 °C Temperature: Coolant flow rate: 37.7 m3/s 12 °C Coolant T: 1866 MWth Thermal power: Electrical power: 919 MWe
AP600 0.085 bar 42.6 °C 25.103 m3/s 12 °C 1244 MWth 675 MWe
The sea water characteristics assumed are the following: temperature 20 °C, salinity 41000 ppm The conditions at the condenser have been analyzed: the coolant flow rate has been calculated for a constant temperature increase in the condenser (12 °C) in all the conditions.
Fig. 3 - Flash tank scheme
3
A minimum value of 0.12 bar has been considered, to obtain in the condenser a temperature suitable for an efficient desalination process. The higher value of 0.474 bar has been limited to avoid an excessive loss of power in the turbine.
The calculation have been performed with a TTD (Terminal Temperature Difference) at the condenser of 2°C. Therefore, the inlet and outlet temperatures of the coolant summarized in Table II have been considered.
Table II - Assumed conditions in the nuclear plant condenser Pressure, bar 0.12 0.14 0.18 0.22 49.45 52.6 57.8 62.2 Temperature, °C 50.6 55.8 60.2 Outlet Temperature, °C 47.45 35.45 38.6 43.8 48.2 Inlet Temperature, °C AP600 657 647 628 607 Electrical power, MWe 1262 1273 1293 1313 Thermal power, MW Coolant flow rate, kg/s 25240 25460 25860 26260 PWR900 861 843 807 771 Electrical power, MWe 1921 1938 1972 2006 Thermal power, MW Coolant flow rate, kg/s 38420 38760 39440 40120 IV.A. PWR/MED Flash Tank Coupling
0.3 67.1 65.1 53.1
0.4 75.9 73.9 61.9
0.474 80 78 66
567 517 1353 1403 27060 28060
480 1440 28800
699 609 2070 2155 41400 43100
542 2218 44360
be higher than the produced steam flow rate to be reintroduced in the loop. Therefore a fraction of the water, after the exchanger, is rejected (r). Referring to fig. 3, the following balance equations have been applied:
The flash tank loop has the following requirements: 1. Constant salinity in the circulating water; 2. Design temperature at the condenser inlet. A make-up flow with water at a fixed salinity (lower than in the water loop) allows to respect the Requirement n° 1. An heat exchanger in the water loop, cooled by external sea-water, has been introduced to respect the Requirement n° 2. For the make-up flow (r), the drain (preheated seawater) from the desalination plant may be used, to avoid consumption of fresh water. Nevertheless, in this case, a constant salinity higher than in sea water has to be accepted in the water loop of the flash tank. This salinity has to be limited to avoid corrosion problems. A value of 60000 ppm has been selected, and sensitivity analyses at 50000 and 70000 ppm have also been performed. A temperature of 32 °C for the drain has been selected, considering a preheating of 12 °C of sea water in the MED pre-heater. In the flash tank, pressure must be lower than the saturation value at the coolant outlet temperature to have a high flashing ratio (evaporating fraction of the coolant flow rate c). But the Requirement n° 2 needs to be met and the saturation temperature in the flash tank has to be higher than the inlet coolant temperature. After the mixing of the condensate from the flash tank and the make-up flow (drain from MED), the temperature may need a limited correction through the heat exchanger, to match the required value. The drain flow rate is a consequence of the maximum required salinity in the water loop and this flow rate may
Energy balance in the flash tank:
c hc,o s hs c s hl
(1)
from which:
s c
hc,o hl hs hl
(2)
Salt balance:
c s r sc r sr c sc
(3)
from which:
r s
sc sc s r
(4)
Energy balance of the heat exchanger:
c s hl r hr c s r hc,i Q
(5)
Mass balance:
c s r j c
4
(6)
from which: M ED PLANT
j r s
(7)
18
N u m b er o f stag es
16
The coolant flow rate c and its inlet and outlet enthalpies hc,i , hc,o are known from the condenser conditions, and its salinity sc is selected. Two ways to proceed are possible for closing the heat and mass balances: 1. saturation conditions in the flash tank are fixed such as:
14 12 10 8 6 4 2 0 35
hc,i < hl < hc,o
40
45
(8)
50
55
60
65
70
75
80
85
S te a m te m p e ra tu re °C
In this case, Eqs. 2, 4, 5 and 7 allow to define the system. In this case a quantity of heat Q will be rejected through the heat exchanger.
Fig. 5 -
2. Through Eq. 5 the rejected heat is assumed =0 (or minimized, to always satisfy the condition (8)) and using a quite complicated iterative procedure, saturation conditions in the flash tank can be found. This second way maximizes the utilization of heat and the flashing ratio inside the flash tank (more steam produced for unit coolant flow rate). In this case, Eqs. 2, 4, 5 and 7 allow to define the system. In this case a quantity of heat Q will be rejected through the heat exchanger. Therefore, this procedure seems to be more attractive than the first one. But, to maximize water production in the desalination plant, we have to consider the GOR also (energy required for unit of distillate produced), which depends on the steam temperature produced by the flash tank. Therefore, we can have a lot of steam produced at a low temperature for which the GOR is lower with respect to a situation with a lower production of steam at a higher temperature. In conclusion, the saturation conditions in the flash tank are first evaluated minimizing (if possible =0) the heat rejected Q . Then these conditions are manually modified to match the condition for which the desalination plant GOR is maximized. This is not a simple procedure because GOR is not a linear function with the temperature but it depends on the number of stages of the desalination plant (that is not a continuous function of the temperature). In fig. 5, the number of stages for a MED desalination plant is shown as a function of the steam temperature, for the following conditions: sea water temperature: 20°C; temperature increase in the pre-heater: 12 °C TTD at the preheater: 2.5 °C. In fig. 6 the steam consumption for a MED plant (in parallel configuration or in serial configuration with preheaters) is shown.
Number of effects for different heat source temperatures M ED PLANT
S team co n su m p tio n kg /h p er 1000 t/h d ist
4 .0 E + 0 5 3 .5 E + 0 5 3 .0 E + 0 5 p a ra lle l
2 .5 E + 0 5
s e ria l
2 .0 E + 0 5 1 .5 E + 0 5 1 .0 E + 0 5 5 .0 E + 0 4 0 .0 E + 0 0 35
40
45
50
55
60
65
70
75
80
85
S te a m te m p e ra tu re °C
Fig. 6 -
Steam consumption of a MED plant for different heat source temperatures
The described optimization procedure has been applied (with the restriction imposing that the desalination plant needs at least 2 stages to operate) and the results obtained are reported in the following Table III (only results for a maximum value of 60000 ppm of salinity in the loop are shown).
IV.B. PWR/MED Intermediate Water Loop Coupling The coupling of a PWR with conventional MED plant is simpler to analyze as comparing to the coupling through the flash tank. The condenser coolant transfers heat directly to the brine heater (the first stage of the MED plant), with the flow rate and temperatures described in the previous Table II for different condenser conditions. As in the previous analysis, two different configurations of the desalination plant have been considered: parallel and serial with preheaters.
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Table III - Results of the flash-tank coupling scheme calculations (in bold the maximum values of distillate production) condenser pressure, bar 0.12 0.14 0.18 0.22 0.3 0.4 0.474 condenser temperature, °C 49.45 52.6 57.8 62.2 67.1 75.9 80 39.5 39.5 44.5 49.5 54.5 63.2 67.5 flash tank temperature, °C 2 2 4 6 8 11 13 Number of MED stages AP600 (parallel) production, m3/d 84390 118691 195080 256055 318248 418629 464227 2.9 2.9 4.72 6.33 7.73 9.34 10.21 GOR (parallel) 84027 118179 194751 258418 327438 453209 529575 (serial) production, m3/d 2.9 2.9 4.69 6.37 7.96 10.23 11.67 GOR (serial) PWR 900 (parallel) production, m3/d 128707 181019 297523 391200 486898 643012 715039 2.9 2.9 4.72 6.33 7.73 9.34 10.21 GOR (parallel) 128152 180239 297022 394810 500959 696127 815692 (serial) production, m3/d 2.9 2.9 4.69 6.37 7.96 10.23 11.67 GOR (serial)
The lowest available flash tank temperature has to be higher than 45 °C to couple an efficient MED plant. For this reason, calculations have been limited to condenser pressures higher than 0.22 bar (see Table III) Table IV shows the results obtained in these calculations.
safety requirement of "minimum two barriers plus pressure reversal" between the reactor and the desalination plant. Reference is made to the General Atomic study for a flash tank coupling and the Framatome-CEA study for a water loop coupling.
Table IV - Results of the intermediate loop coupling scheme Condenser press., bar 0.22 0.3 0.4 0.474 67.1 75.9 80 Condenser Temp., °C 62.2 60.2 65.1 73.9 78 Outlet Temp., °C 48.2 53.1 61.9 66 Inlet Temp., °C 5 7 11 12 N° of MED Stages AP600 (parallel) prod., m3/d 214679 295029 428029 459531 4.24 5.65 7.91 8.26 GOR (parallel) 3 (serial) prod., m /d 214923 301457 468273 519341 4.24 5.77 8.65 9.33 GOR (serial) PWR900 (parallel) prod., m3/d 327987 451374 657450 707805 4.24 5.65 7.91 8.26 GOR (parallel) (serial) prod., m3/d 328359 461209 719264 799930 4.24 5.77 8.65 9.33 GOR (serial)
V.A. GT-MHR/MED Flash Tank Coupling The Gas Turbine - Modular Helium Reactor (GTMHR), is an ultra-safe, meltdown-proof, helium-cooled reactor, developed to meet the need for safe and economical nuclear-generated electricity and process heat [6]. The reactor is characterized by inert helium coolant; graphite as the core structural material; and refractorycoated particle fuel which retains fission products at very high temperatures. In the GT-MHR, the high temperature helium coolant directly drives a gas turbine coupled to an electric generator. The efficiency of the system is about 48%. This is about 50% more efficient than first generation reactors. A typical GT-MHR module, rated at 600 MW(t), yields a net output of about 285 MW(e). This system permits sequential construction of modules to match the user's growth requirements. Since December 1995, General Atomics, Minatom, Framatome, and Fuji Electric have been working together on the design of a GT-MHR. In fig. 7 the scheme proposed by General Atomics is presented [5]. Heat is transferred from the precooler (170.5 MW) and the intercooler (131.5 MW) through two water loops in parallel. In the first one water reaches a temperature of 120 °C, in the second one a temperature of about 96 °C is obtained. From a simple heat balance, the two flow rates are quite similar and a mixing temperature of about 108 °C may be supposed.
V. COUPLING THE GT-MHR NUCLEAR REACTOR WITH A MED DESALINATION PLANT The coupling of the GT-MHR with a MED desalination plant can be analyzed through the same solutions adopted for pressurized reactors, but an intermediate heat transformer is required to satisfy the
6
GT-MHR Reactor Unit
Desalination Unit (MED)
Heat Transformer Unit Intermediate Water Loop
Generator
Seawater out
Turbine MED
Flash tank Reactor Recuperator
Seawater in Fresh water
26 °C
HP Compressor
128.3 °C
Switch Cooling Unit
Seawater out
Intercooler Precooler Heat sink
Seawater in
105.6 °C LP Compressor
26 °C
Blowdown
Fig. 7 - GT-MHR / MED coupling scheme with a flash tank
The lowest water temperature must be lower than 22 °C, to cool helium at 26 °C, as shown in the scheme. Therefore, in the heat transformer unit, assuming a minimum T of 2°C, the coolant temperature range is between 106 °C and 22 °C, also considering that 20 °C have been assumed as sea water temperature. It should be remarked that all the calculations have been performed considering a 60000 ppm salinity in the coolant loop. Results obtained are reported in Table V. A low temperature configuration has been analyzed: it is that proposed by FRAMATOME ANP and CEAGRETH (80 - 22 °C) for the cooling fluid [5]. This configuration allows a lower production of distillate with respect the previous one. In this case, two optimal temperature levels have been found for the flash tank temperature: 52 °C and 57 °C, providing quite the same distillate production. The lowest temperature produces more steam in the flash tank but the MED plant has a lower GOR with respect to the previous one. Optimization criteria suggest, in this case, to adopt this solution with a lower number of stages, because, for quite the same production, the cost of the desalination plant is lower.
Table V - GT-MHR coupling with a flash tank °C 106 80 80 Coolant high temperature °C 22 22 22 Coolant low temperature 895.4 1313.9 1313.9 Coolant flow rate kg/s (60000 ppm) °C 69.5 52 57 Flash tank T kg/s 57.1 61.6 51.0 Steam produced 180.2 194.7 161.0 Make-up flow rate kg/s 123.1 133.0 110.0 Rejected flow rate kg/s Heat rejected in the MW 155.7 145.81 172.4 heat sink Total heat rejected MW 166.2 157.2 181.8 14 7 9 N° of MED stages parallel MED m3/d 52382 37633 36535 distillate prod. 10.62 7.07 8.29 GOR kJ/kg 247.03 367.20 313.91 H.P. serial MED m3/d 61508 38306 38098 distillate prod. 12.48 7.19 8.65 GOR kJ/kg 210.37 360.75 301.03 H.P.
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V.B. GT-MHR/MED Intermediate Water Loop Coupling According to the previous scheme, the coolant temperature range available from the Heat Transformer Unit is 106 °C to 22 °C. The highest temperature is suitable to provide heat directly to an high-efficiency MED plant. The lowest temperature is not adequate to this purpose. Therefore a consistent fraction of the heat available has to be rejected. A temperature range from 106°C to 50°C has been selected to transfer about 200 MW to the desalination plant. Other 100 MW will be rejected through an heat exchanger to match the temperature of 22 °C for coolant at the inlet of the Heat Transformer Unit (figs. 8 and 9).
Fig. 9 - GT-MHR coupling with the water loop: Heat Run Out scheme Table VI- GT-MHR coupling with an intermediate loop (High temperature configuration) In-out n° of Temp Prod. MED GOR 3 m /d °C stages Base scheme 6 5.02 In/Out temperatures 106/50 38880 Total 38880 Fig. 8 - GT-MHR coupling with the water loop As suggested by a FRAMATOME ANP/CEAGRETH study, two configurations have been analyzed: a base scheme with the coolant temperature from 106°C to 50°C (fig. 8) and the "Heat run-out " configuration, where two, three and four steps have been assumed (106-78 °C, 78-50 °C or 106-87°C, 87-68°, 68-50 °C or 106-92 °C, 92-78 °C, 78-64 °C, 64-50 °C respectively, fig. 9). The coolant flow rate in the loop, assumed at null salinity, is about 853.2 kg/s. Calculations have been performed using the serial MED process, with a sea water temperature of 20 °C, 41000 ppm salinity and a concentration ratio 1.75. Table VI underlines the fact that the Heat Run-Out scheme provides a bigger amount of distillate (more than a factor 2). But it must be remarked that, in this scheme, the gain in distillate production from two to three (+13%) or four (+19%) temperature intervals is probably lower than the increment of costs for the construction of three or four desalination plants, even if they are smaller than in the previous two-plants scheme. However, it is possible to envisage Heat Run-Out schemes with only one line and a periodic re-injection of hot water. This may lead to much lower costs.
Heat Run Out sch 2 In/Out temperatures In/Out temperatures Total
106/78 50400 78/50 19920 70320
17 6
12.63 5.02
Heat Run Out sch 3 In/Out temperatures In/Out temperatures In/Out temperatures Total
106/87 39600 87/68 27120 68/50 12816 79536
20 13 6
14.68 10.07 5.02
Heat Run Out sch 4 In/Out temperatures InOut temperatures In/Out temperatures In/Out temperatures Total
106/92 31440 92/78 25056 78/64 17136 64/50 9936 83568
22 17 11 6
16.36 12.63 8.65 5.02
The same analysis has been performed for the Framatome-ANP/CEA-GRETH scheme (80 - 22°C). In this case only 156 MW of thermal energy are available for the desalination plant with a minimum useful temperature of 50°C. The coolant flow rate in the loop, as fresh water, is 1239.5 kg/s. In this case, due to the limited high 8
temperature, two and three steps (80-65°C, 65-50 °C and 80-70 °C, 70-60 °C, 60-50°C, respectively) are compared with the base solution (80-50°C), as reported in Table VII.
ACKNOWLEDGMENTS This work was performed in the framework of the EURODESAL project (contract n° FIKI-CT-2000-20078, 5th EU FWP).
Table VII- GT-MHR coupling with an intermediate loop (Low Temperature configuration) In-out n° of Prod. Temp MED GOR 3 m /d °C stages Base scheme 6 5.02 In/Out temperatures 80/50 30000 Total 30000 Heat Run Out scheme 2 12 In/Out temperatures 80/65 27888 6 In/Out temperatures 65/50 15000 Total 42888
9.33 5.02
Heat Run Out scheme 3 14 In/Out temperatures 80/70 21360 10 In/Out temperatures 70/60 15840 6 In/Out temperatures 60/50 10008 Total 47208
10.67 7.95 5.02
NOMENCLATURE GOR s h Q
kg of distillate/kg of steam input flow rate [kg/s] salinity [g/kg] specific enthalpy [J/kgK] heat [W]
suffixes c i j l o r s w
coolant inlet reject from the flash tank loop saturated liquid from the flash tank outlet reject from the desalination plant steam sea water
The same considerations as in the previous scheme may be applied. The increase of distillate production from 2 desalination plant to 3 plants is only 10%.
REFERENCES 1.
INTERNATIONAL ATOMIC ENERGY AGENCY, Examining the economics of seawater desalination using the DEEP code, IAEA TECDOC-1186, Vienna December 2000.
2.
S. NISAN et al., "Applications of Innovative Nuclear Reactor Concepts for Sea-water Desalination in Southern Europe; The EURODESAL project" FISA 2001 Conference, Luxembourg, Nov. 12-14, 2001.
3.
A. H. KHAN Desalination Processes and Multistage Flash Distillation Practice” Elsevier, 1986
4.
"The desalting ABC’s” Prepared by O.K.Buros for the desalination association; modified and reproduced by research department saline water conversion corporation of Riyad; 1990; pag. 1-49 Riyadh, (Saudi Arabia); IDA
5.
S. NISAN, "Meeting Report, EURODESAL First Technical Meeting", Madrid, (May 4-5, 2001).
6.
L. S. Blue, K. T. Etzel, W. A. Simon, J. D. Wistrom. "The GT-MHR - Clean, Economic, and Safe Power for the Pacific Rim" American Nuclear Society, Transaction, vol.70 supplement 1994, pp.291-295.
VI. CONCLUSIONS The calculations performed show that there are several solutions to couple PWR plants and GCR plants to a ME desalination plant. Referring to pressurized reactors, the flash tank solution provides a greater production of distillate for all the condenser conditions analyzed. Furthermore, this type of coupling is the only solution to couple the MED plant in the case of low pressure condenser conditions. The optimal value of the condenser pressure depends on the specific site requirements of power and water and on economic considerations. The optimal solution for the GT-MHR nuclear plant is the coupling with an intermediate water loop, adopting an heat run out scheme with only 2 temperature steps. As discussed, the gain in distillate production from two to three (+13%) or four (+19%) temperature intervals is probably lower than the increment of costs for manufacturing three or four desalination plants, even if they are smaller than the previous two plants. With heat run-out schemes with only one line, the economics may be much more favourable.
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