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Nuclear power and the desalination of salt waters
Journal of Nuckar Encqy,
1967. Vol. 21. pp. 585 to 600.
NUCLEAR
Per&vmtoa Press Ltd.
printed in Northern Irclsnd
POWER AND THE DESALINATION OF SALT WATERS*? Yu.
I.
KORYAKIN
and A. A.
LOGINOV
(Received21 October 1965) INTRODUCTION As
A RESULT of the considerable success in recent years in the building of nuclear power reactors, interest has been growing in many countries of the World in the possibility of using nuclear reactors to augment the rapidly diminishing supplies of fresh water. The Soviet Union (or rather a number of its regions) is one of the large group of countries who are experiencing such a shortage of fresh water . The extent of the interest of the U.S.S.R. in solving this problem is brought out particularly clearly in the papers presented by the Soviet Union to the First International Symposium on Water Desalination. Altogether 21 papers were presented, covering a variety of aspects pertaining to the desalination of salt and brackish waters. The main object of the present article is to review those problems presented in these papers which relate to the economics, techniques and heat technology involved in using nuclear reactors in desalination plants employing the distillation method. The distillation method embraces two distinct techniques for desalinating salt water, namely evaporation and flash distillation, and it is the most suitable way of using nuclear reactors in atomic desalination plants. In this review, a general outline is also given of the technology of obtaining fresh water in the distillation type of desalination plant and methods are described of producing fresh water from salt and brackish waters which do not involve distillation (for example, electrodialysis and ion-exchange methods). ECONOMICS
OF
DESALINATION
The question of the economics of operating nuclear reactor desalination plants is naturally the one receiving most attention at the present time. There is no doubt at all that any of the several different types of power reactor which have proved themselves in actual operation could be used as the basis of a successful nuclear desalination plant. The reactor in a nuclear desalination plant is used as the heat source for distilling water with a heightened mineralization. In dual-purpose installations, the production of the distillate takes place simultaneously with the production of electrical energy, since the heat potential is high enough to generate steam with parameters suitable for driving a turbine. The question of the economics of dual-purpose nuclear desalination plants is a more complicated matter, however. Such installations have the special feature that two kinds of product are produced at one and the same time-the distillate and the * Translated by D. L. ALLAN from Atomnaya Energiya 20,232 (1966). $ Survey of papers presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 585
586
Yu. I. KORYAKIN and A. A. Locmov
electrical energy, Since the assessment of the production costs for these two types of product may be arrived at in different ways, there are good reasons for using various approaches and procedures when determining the economic indices of the installations. To find the conditions necessary for economically competitive dual-purpose nuclear desalination plants, the most acceptable method of calculating the technological and economic indices is one which enables comparisons to be made between installations incorporating different types of nuclear reactors and the conventional methods of generating electrical power and of producing fresh water. The proposed construction site should be taken into account but no account should be given to any local economic peculiarities of the region. These factors are the main ones to be considered during the economic and design studies of dual-purpose installations for the conditions existing in the U.S.S.R., where both of the products from dual-purpose plants are equally important from the point of view of the national economy. The procedure of analysis we adopt here has already been described elsewhere”). The essence of the method is to take the prime cost of the heating steam in nuclear dual-purpose plants as being equal to the cost of the lost electricity that could have been produced were the reactor operating in a condensing atomic power station. The annual cost of the lost electricity production is considered to be the cost of generating the heat of the steam used to distil the water. In this case the annual production costs of a dual-purpose plant are obtained by adding the electricity and distillate production costs. As in the case of a condensing atomic power station, the electricity production costs are found first by determining the prime cost of the electricity and then allowing for the lost electricity production and the small saving arising from the fact that some of the equipment needed in a condensing atomic power station will not be required. The distillate production costs are found by adding the production costs of the desalination section of the plant and the heating steam generation costs. A nuclear power source combined with a desalination plant represents a complex engineering installation characterized by a large number of heat technology, physics and technical indices which directly or indirectly affect the prime costs of the products. It is clear therefore that the optimization of the technical and economic factors involved in a dual-purpose nuclear plant would be an impossible task without the help of electronic computer techniques. L~GINOVet ~1.‘~)have given details of a methodical approach to this problem for three types of U.S.S.R. reactor, namely those at the Beloyarsk, Novo-Voronezh and Shevchenko nuclear power stations and for two versions of thermal installation in the desalination part of the plant, namely one with vertical evaporation equipment and one with flash distillation equipment. The method they describe is suitable for optimization purposes and permits comparisons to be made over a wide range of variation of the technical characteristics of both the reactor and the desalination sections of the plants. In addition, the capital outlay for the nuclear (including the power circuit) and the desalination sections are considered separately. With this approach to estimating the capital cost, one makes the best possible use of the available nuclear energetics data. It is also possible to allow for certain trends and economic peculiarities which are observed when the unit power of the reactors is significantly increased above that for existing reactors.
Nuclear power and the desalinationof salt waters
587
On the basis of the data published by SINEVet ,Z.c3)and by SBRGFXNKO(~), approximate relationships have been obtained (Table 1) giving the capital expenditure on the nuclear section of desalination installations as a function of the thermal power of the reactor, and also the dependence of the capital expenditure on the water purifying section as a function of distillate output for 7-stage vertical evaporators and for 30-stage flash-distillation installations. Table 1 also gives the prime cost of the electricity from condensation nuclear power stations, incorporating the reactors indicated, as a function of their thermal power for an installed power utilization coefficient equal to 0.8. Curves showing how the cost of the heating steam depends on the thermal power of the reactor for various heating steam temperatures are presented in Fig. 1. It is evident that for a reactor of the Novo-Voronezh type, the cost of the heat depends strongly not only on the thermal power of the reactor (up to ~2000 MW) but also on the temperature of the heating steam whereas, for a reactor of the Beloyarsk type, these dependences are less pronounced. This is explained by the higher steam parameters of the Beloyarsk type of reactor and, consequently, by the smaller effect introduced by the relative loss of electricity production. For the Shevchenko type of reactor, the steam heating costs depend markedly on the thermal power of the reactor and reach lower values in comparison with other types of reactor. Table 2 gives the preliminary, generalized results of an analysis which yielded the indices for dual-purpose plants. An analysis of the thermal and economic indices has been carried out also by several other authors.@-‘) The main interest here was the estimation of the thermal desalination section of dual-purpose plants; the nuclear section was hardly considered. Thus, SERGEENKO’analyses ~) three desalination layouts : (1) multi-stage flash evaporation with surface condensation; (2) multi-stage surface evaporation with non-surface (mixing) condensation; (3) once-through, sequential multiple evaporation. The dependence of the distillate costs on the number of stages of the plant was found for all three schemes for various assumed values for the cost of the heating steam. In addition, the dependence of the unit capital outlay on plant construction (referred to a productive capacity of 1 tonne/hr) on the number of stages for different iixed values of the other determining parameters was calculated. A procedure for determining the optimum heat economy for dual-purpose nuclear plants based on the use of a Novo-Voronezh type of reactor is explained by STEFMAN and GUBENKO(~).Results are also given of an analysis in which it was assumed that the coolant temperature was equal to that of the reactor at the Novo-Voronezh nuclear power station (275280°C). GOLUBKOVand KORNEICHEVw have obtained curves enabling one to find the basic technical indices of thermal desalination plants. They also give a method for making the technical and economic calculations needed for determining the optimum (for minimum outlay) parameters of thermal desalination plants, and have derived analytical expressions for determining the optimum number of evaporation stages and the optimum amount of sub-cooling of the water in the surface condensers. Three types of desalination layout were examined: (i) with surface evaporators (with a falling film); (ii) with flash distillation; (iii) with a hydrophobic coolant. Whereas the last three pape#+ are of a rather theoretical nature, the aim of the paper by GOLUBet ~1.“) is to give a comparative appraisal confined to those thermal
C a* - 87-45 x exp (-1.195 x lo-’ Qr) [million roubles]
[q=ks/kW . hl
csms = 0.457 + 3.8 exp (-0.418 x lo-‘QI)
Beloyarsk Nuclear Power Station
Qr
*w
rcopeckslkw. hl
Cfme = 3442 x Qr-I’“”
C caD= 87-45 C csp - 107~2.5 x ex (-0.73 x lO+ Q,) x exp (-0.982 x lo-” Q,) [million roubles] Pmillion roubles]
bp=wkw
cg&, = 0.457 + 3.8 exp (-a253 x lo-‘Q,>
c&t = 1800 + 44.75 x lo” G-o“*’ [roubles/torme/hr]
7-stage equipment (evaporation)
c&t = 2210 + 218.2 x lo” G-e’6’s [roubles/tonne/hr]
3Mage e@pment @ash distlllatioll)
G = (0.1-30) x lO’tonne/hr
AND CApmu Cosr c,., ON THE THERMAL CAPACITY OF THE DWllLLATB G
Shevchenko Nuclear Power station
OF THE PFWE OF ELw;TRIcITy Cgime OF TEE REACKJR AND ON THE PRODU~
Nuclear Power station
Q’
POWER
TABLE l.-D~NDENCE
?
E ?
Q
%
L
Nuclear power and the desalination of salt waters
0.50
500
1000
I500 Q ,*
050
0
500
500
1000
1000
1500
1500
a r.
2500
2000
2500
2000
2500
MW of the cost C, of the heating steam on the thermal power of the (a) Beloyarsk t of reactor; (b) Novo-Voronezh type of reactor; (c)y!ehevchenko type of reactor.
FIG l.-Dependence
reactor Q.:
2000 MW
YIJ. I. KORYAKINand A. A. LOGINOV
590
TABLET.-TECHNICAL
Type of reactor Novo-Voronezh Nuclear Power Station
Steam temperature (“C)
750
100 120 100 120 100 120 100 120
135 108 270 216 338 271 405 324
100 120 140 100 120 140 100 120 140 100 120 140
242 235 228 485 470 456 606 588 570 727 706 684
100 120 140 100 120 140 100
242 235 228 485 470 456 606
120 140 100 120 140
588 570 727 706 684
1500 1875 2250
Beloyarsk Nuclear Power Station
760 1520 1900 2280
Shevchenko Nuclear Power Station
Useful electrical
Thermal power (Mw)
760 1520
1900 2280
gq
Capital cost of nuclear section [million roubles]
Prime cost of electricity (copecks/ /kW . hr)
61.0
1.012
71.9
0.542
75.6
0.488
78.3
O-470
68.9
0609
79.3
0.464
82.3
0.458
84.0
o-457
86.9
O-736
97.4
0.300
100.4
0.233
102.5
0.177
AND ECONOMIC
Prime cost of heating Heat for steam desalination (cope&/ (g-cal/hr) g-cal/hr) 494 509 988 1018 1235 1272 1482 1527 368 373 380 735 747 .-760
153.5 203.0 83.0 108-O 74.8 97.6 71.9 94.0 96.0
934 950 1104 1121 1140
106.0 115.3 73-l 80.9 88-O 72.2 79.8 87.0 72-O 79.6 86.7
368 373 380 735 747 760 920
116-O 128-O 139.5 47.0 52.3 57.7 36-5
934 950 1104 1121 1140
z.: 27.7 30.6 33-5
920
* Flash distillation. t Evaporation.
desalination schemes which could actually be built now and which could be operated with reasonably good efficiency. According to these authors(‘), such schemes are the following: (a) flash distillation schemes with preliminary acid treatment of the intake water to prevent salt-deposition; (b) flash distillation with re-cycling of the sea-water and acid treatment, or with the addition of seeding crystals; (c) evaporation in vertical long-pipe equipment with a falling fihn together with a preliminary acid treatment of the intake water; (d) evaporation with natural circulation and evaporation with forced circulation of sea-water accompanied in both cases by seeding with crystals. A comparative analysis was made with respect to thermal economics, the conditions for preventing salt-deposition, cost of equipment and reliability. The authors conclude that for the conditions prevailing in the U.S.S.R., and within the range of productive capacity of fresh water considered, the flash distillation
Nuclear power and the desalinationof salt waters INDICES OF DUAL-PURPOSE
Distillate productive
PLANTS
Prime cost of
Capital cost of desalination
distillate without allowing for heat (copecks/toMe) Flash Vertical
SWtiOll
(lO-%$a,,, Flash* Vertical?
591
[million roubles] Flash Vertical
Prime cost of distillate (cope&s/tonne) Flash Vertical
Type of reactor
166.5 168.0 333.0 336.0 418.0 490.5 502 564
139.2 143.8 278.4 287.6 349.5 359.0 419.5 430.5
18.4 20.4 34.6 38.7 42.6 47.6 50.6 565
11.5 11.8 22.2 23.0 27.7 28.5 33.0 34.0
7.87 7.79 7.57 7.53 7.49 7.46 744 741
5.96 5.94 5.83 5.83 5.81 5.81 5.78 5.78
18.67 20.99 13.46 14.57 12.80 13.81 12.54 13.52
19.01 2324 12.89 14.99 12.15 14.02 11.89 13.77
Nova-Voronezh Nuclear Power Station
204.2 381.0 429.0 249.3 2760 285.7 311.3 344.7 357.2 374.0 416.0 428.0
103.8 105.2 107.3 207.1 211.0 214.8 259.2 263.8 267.2 312.1 317.0 322.0
14.3 15.7 16.1 26.4 29.1 30.0 32.4 35.7 36.8 38.4 42.4 43.7
8.8 8.9 9.0 16.8 17.1 17.4 20.8 21.1 21.5 24.8 25.2 25.6
8.06 8.02 8.00 7.68 7.65 7.64 7.61 7.57 7.56 752 7.49 7.48
6.05 605 6.04 5.89 5.89 5.88 5.85 585 5.84 5.83 5.83 5.83
14.88 14.91 15.36 12.87 1290 13.27 12.72 12.76 13.13 12.62 1265 13.02
14.21 15.06 15.84 12.10 12.76 13.36 11.99 12.62 13.23 11.95 12.59 13.19
Beloyarsk Nuclear Power Station
204.2 381.0 429.0 249.3 2760 285.7 311.3 344.7 357.2 374.0 416.0 428.0
103.8 105.2 107.3 207.1 211.0 214.8 259.2 263.8 267.2 312.1 317.0 3220
14.3 15.6 16.1 26.4 29.1 30.0 32.4 35.7 36.8 38.4 42.4 43.7
8.8 8.9 9.0 16.8 17.1 17.4 20.8 21.1 21.5 24.8 25.2 25.6
8.06 8.02 .;::
6.05 6.05 6.04 5.89 5.89 5.88 5.85 5.85 5.84 5.83 5.83 5.83
16.31 16.35 16.94 11.01 11.05 11.33 10.20 10.19 10.37 9.49 9.47 9.69
15.90 16.95 17.89 9.89 10.33 10.78 8.95 9.29 9.58 8.20 8.43 8.68
Shevchenko NUClWU Power Station
7.65 764 7.61 7.57 7.56 7.52 7.49 7.48
method was not quite so competitive conclusion
economically
as the evaporation
method.
This
is in accord with the results of LOGINOV et ,Z.@) and is also partly in
accord with the findings of SERGEENKO(*) and it is based on the fact that
one has had more experience in operating evaporation equipment compared with flash distillation equipment. However, because of the increased productivity of desalination plants when operated in conjunction with reactors having thermal powers of the order 2-3000 MW, the economic indices of these two types of plant will eventually become comparable. With an even greater increase in the thermal power of the reactor, the advantage will evidently lie with the flash distillation plants. POSSIBLE
TECHNICAL
SOLUTIONS
KORYAKIN et ,Z.@) have attempted to estimate the technical and economic characteristics which a relatively high-power dual-purpose nuclear plant with a Beloyarsk 4
Yu. I.
592
and A. A. L~GINOV
KOXYMIN
type of reactor would have. This type of reactor belongs to the channel class and is capable of developing a high unit thermal power, this being one of the decisive conditions for attaining the break-even point with nuclear dual-purpose plants. Other factors in favour of this type of reactor are that the coolant loop presents no radiation hazards, it has high efficiency (ensuring a high production ratio of electricity to distillate), the fact that one can use standard steam power equipment, there is a reasonably efficient nuclear fuel utilization, there exists a considerable amount of experience in the planning, construction and operation of such a reactor. All these considerations lead one to believe that a promising future lies ahead for dual-purpose nuclear plants. We considered two technological schemes: (1) a scheme with sub-critical coolant parameters (90 atm, 535’0; (2) a scheme with super-critical parameters (240 atm, 535/535’C). The first scheme is illustrated in Fig. 2. Both schemes make use of a 363
tonne/
hr.
90
otmos,
535%
,
298
5 \c
17.7 tonne/hr,
31.2
16.2 tonne /hr. 19.5 atmos,
2
I I.6 363
tonne/hr,2,0
atmos,
12O’C
atmos,404T
346T
8.7 tonne / hr, atmos 294’C
7.8 tonne/ 6.0 atmos
hr,
‘14 IO
FIG. 2.-Basic diagram of the thermal circuit of the power loop of a plant incorporating a Beloyarsk type reactor with a thermal power of 520 MW: l-reactor; 2-evaporator channels; 3-superheating channels; 4-separator drum; 5-preheater; 6-turbine; 7-generator; 8-condenser-sea-water boiler; g-condensation pump; lO-regenerative pre-heater; 1l-de-aerator; 12-feed pump; 13-circulating pump; !Athrottle. flash-distillation installation in the desalination section of the plant. Below we give the results of a calculation of the fundamentaleconomicindices of dual-purpose plants incorporating a Beloyarsk type of reactor:
30-stage
Thermal power of reactor (MW) Electrical power (MW) Heat consumed in distillation (kcal/br) Distillate production (tonne@) Capital outlay on electricity generating section of plant (millions of roubles) Prime cost of electricity (copecks/kWh) Capital outlay on desalination section of plant (millions of roubles) Prime cost of distillate without allowing for cost of heat @pecks/ tonne) Unit heat consumption expended on distillate &xl/kg) Prime cost of heat for the heating steam (copecks/g-cal) Prime cost of distillate (copecks/tonne)
90 atm 520 150 312 x 10’ 4.8 x 10’
240 atm 1950 600 1080 x 10” 16.8 x 108
62.5 1.060
83.0 0.458
13.35
40.60
8.11 65 170 19.12
7.43 64 127 13.57
Nuclear power and the desalination of salt waters
593
In most cases, the design specifications of dual-purpose nuclear plants call for the use of back-pressure turbines. Although such turbines have their advantages they have also a number of disadvantages; in particular, the lack of flexibility in operation of dual-purpose plants arising from the fact that the productive capacity for the distillate is rigidly tied to that for the electricity during possible appreciable fluctuations of the power and thermal loads. Greater flexibility can be provided if turbines with controllable steam extraction are used. For this reason, in the paper by DMITRIEV(~), turbines with controllable steam extraction were specified in all the schemes considered. Three schemes for dual-purpose plants were compared employing reactors of the Beloyarsk, Novo-Voronezh and Shevchenko types with identical fresh-water outputs (95 million m3/year) but with different electrical power outputs. The comparison was made with respect to the total capital costs (with a breakdown into consolidated items of expenditure) and with respect to a nominal distillate selling price for an assumed electricity selling price. It was concluded that for the highest water productivity the best scheme from the economic point of view is a version of a plant with a fast reactor of the Shevchenko type (Fig. 3). As well as high-power nuclear desalination plants, there is interest also in building nuclear desalination plants of relatively low power (producing 150-500 tonne/hr). The need for such plants is determined by the geographic and economic peculiarities of a number of regions and locations where fresh water conveyance is difficult and where the transport of conventional fuels for salt-water distillation and electricity generation involves considerable expense. In addition, in some cases, a desalination plant may be required to play a single-purpose role. POLUSHKIN et uZ.(~O) have considered the possibility of building low-power desalination plants, the prototype of which is the ARBUSplant (where the coolant is hydroterphenyl) with the use of multiple sequential evaporation. The basic scheme of the plant is shown in Fig. 4. These authors analysed plants incorporating reactors with thermal powers equal to 15,30 and 70 MW. The organioorganic type of reactor is more suitable for installations based on reactors with thermal powers up to 30 MW; for higher power reactors it is more efficient, from economic considerations, to use reactors with an organic coolant and a solid moderator. The basic technical and economic indices of these plants (calculated according to the procedure described by Koryakin) are given in Table 3. The equipment and individual components of the plant can be delivered to the construction site in the form of separate, completely assembled units which have already been tested at the factory where they were manufactured. The weight and dimensions of the units are such that they can be delivered to the site by any form of transport (the weight of the units does not exceed 20 tonne). The plant is housed in a prefabricated building with a frame-shield type of construction. ECONOMIC
COMPETITIVENESS
We have discussed above the prime costs of the electricity and distillate for large capacity nuclear desalination plants incorporating various types of reactor. These costs permit one to assess the economic effectiveness of dual-purpose nuclear plants, i.e. the costs of producing the electricity and distillate. The procedure we used(l) for allocating the cost enables us to avoid the uncertainties in calculating economic indices of dual-purpose installations which arise when one designates the
Yu. 1. KORYAKINand A. A. LOGINOV
hi r.+--___---___
__._.,
Nuclear power and the desalination of salt waters
595
TABLE3.-TECHNICAL AND ECONOMIC INDICESOF DESALJNATION PLANTS
Characteristics Useful electrical power (kw) Plant power requirements (kW) Heat consumed by desalination process (lccaljhr) Unit heat consumption expended on distillate (kcal/hr) Distillate production (tonne/h@ Capital cost of desalination section (million roubles) Total capital cost of plant (million roubles) Prime cost of electricity (copecks/kW . hr) Prime cost of distillate (copecks/tonne)
Thermal power of reactor (Mw) 15 30 70 400 11 x 106 86.7 127.5 0.493 2.093 68
7.50 22 x 10” 867 2550 0.801 3.201 57
1500 1500 43.8 x lOa 86.7 505 1.350 4650 2.1 42
FIG. 4.-Basic diagram of thermal circuit of a desalination plant incorporating an Aanus-type reactor: l-reactor; 2-steam generator; 3-evaporator (first stage); 4-volume compensator; 5-receiver; 6-regeneration unit; 7-evaporator; S-condenser; g-settling tank.
cost of the electricity (price fixing), as is done abroad. Price-fixing of any of the products for the purpose of estimating the economics of dual-purpose plants during the design stages of the project precludes one from analysing the effect of individual technical characteristics on the prime costs of the distillate and electricity, although this aspect is very important. Moreover, when the conditions are such that both products are equally important from the point of view of the national economy (and this is typically the case for the U.S.S.R.), to make one product cheaper at the expense
596
Yu. I. KORYAKINand A.
A. Lucmov
of the other is inadmissible. Finally, at the present time, it is being suggested that one should approximate the costs to the level demanded by the needs of the community, and this makes price fixing impossible. In the actual operation of dual-purpose plants it may prove expedient to vary the nominal selling prices of the electricity and distillate within the limits of the total production costs of these two products. In that case one could fix the nominal selling price of one of the products on the basis of commercial considerations. This automatically ties the selling price of the other product since the total costs of producing the distillate and the electricity naturally remain unchanged for each plant regardless of the way in which the individual prices are allocated between them. Another similar approach is to regard the dual-purpose plant as a cost-accounting concern. In that case one should fix the nominal electricity selling price from the standpoint of the average net cost of the electricity in the power grid, since a high-power dual-purpose plant will presumable be comected into the power grid. Figure 5 gives graphs plotted from the data of Table 2 showing the dependence of the selling price of the distillate on the selling price of the electricity for the case of dual-purpose plants with vertical equipment incorporating reactors of the Beloyarsk, Novo-Voronezh and Shevchenko types, with equal thermal powers (1500 MW) and steam temperatures (120°C). Points corresponding to the prime costs of the electricity and distillate are plotted on the graphs. 40
C,,
copecks
/ kW hr
FIG. 5.-Dependence of the selling price of the distillate Ca on the selliig p&e of the electricity C, for dual-purpose plants incorporating various reactors: O-calculated points corresponding to the data given in Table 2; 1Shevchenko type of reactor; 2-Beloyarsk ty-pe of reactor; 3-Novo-Voronezh type of reactor.
The drop in the distillate selling price due to increasing the electricity selling price is greatest when reactors ensuring high initial steam parameters are used, since they have a high ratio of electricity output to distillate output (Beloyarsk and Shevchenko nuclear power stations). This is due to the fact that in reactors with high initial steam parameters a greater fraction of the available heat transfer is used for electricity production. Another economically advantageous way of increasing the absolute output of electrical power for a given distillate production capacity is to employ both condensing and back-pressure turbines in a dual-purpose nuclear plant. An additional
Nuclearpowerandthe desalination of saltwaters
597
advantage of such a combination plant is its greater flexibility should any n&match arise between the electricity and distillate load graphs. For reactors working with saturated steam, the choice of the initial steam pressure turns out to have no substantial effect upon the prime cost of the electricity and distillate; the effect of increasing the selling price of the electricity with the aim of decreasing the selling price of the distillate for this type of reactor is considerably less than for reactors working with superheated steam. It should be emphasized that under present-day conditions, when the development of nuclear power has reached a point where the prime cost of the electricity produced is only marginally competitive with that of electricity from conventional sources, there is little scope for reducing the distillate selling price at the expense of raising that of the electricity, and the economic effect of such a measure is negligible. DISTILLATION
TECHNOLOGY
The reports on distillation plant technology presented at the symposium are concerned with two of the most important problems, namely heat exchange and the corrosion of materials in sea-water. CHERNOZUBOV et uL(~) have generalized the results of their work since 1954 on the prevention of precipitation of scale on heat-exchanging surfaces (which causes an abrupt deterioration in the heat exchange and, consequently, of the distillate production capacity) in which they added a seeding material to the sea-water in the form of finely ground natural chalk. As a result of a long period of working with both laboratory and semi-industrial scale plants, these authors have been able to show that the use of seeding under conditions such that the boiling section is taken beyond the heat-exchange limits is a reliable and guaranteed method for the complete prevention of scale formation on heat-exchange surfaces. An intensification of the heat-exchange leads to a substantial improvement of the economic indices for operating distillation desalination plants. Investigations discussed in another paper by CHERNOZUBOVet CZ~.(~~) were conducted along the following lines: (1) the elimination of the harmful effects of non-condensible gases in the heating steam on the heat transfer coefficient during condensation by inducing a turbulent steam flow which destroys the steam-gas layer in the vicinity of the heating surface; (2) inducing rain-like condensation of the steam on the heating surfaces by making use of hydrophobic substances to stimulate rain-like condensation; (3) devising economic methods of raising the heat-transfer coefficient from the side of the liquid in the heat-exchange equipment by jet-feeding the liquid (experiments showed that it was possible to increase ccto (30-35) x 103 kcal . /m2. hr. deg). KONSTANTINOVA et LzL(~~)have studied the corrosion of materials in water from the Caspian Sea, which has a high oxygen content. They conclude that amongst the cheapest and most readily available constructional materials for use in desalination plants, one can recommend St.3 carbon steel (provided that the sea-water is de-aerated and that there is no contact with electropositive materials) and alloys with a copper base LO70-1, MNZhS-1, LA 77-2 (for heating pipes). An eighteen months test of pipes made of LO70-1 brass in an industrial plant revealed no corrosion damage. Investigations carried out by FOKIN and KURTEPOV(~~) on the corrosion of stainless steels in an acidified 3 per cent solution of sodium chloride showed that the molybdenum stainless steel Khl7Nl3MZT has a greater resistance to failure caused by
598
Yu. I. KORYAIUN and A. A. LOOINOV
pitting than KhlSNlOT stainless steel. The same result was obtained in a study of crevice corrosion of these steels. DESALINATION PLANTS NOW OPERATING A Cstage industrial plant has been successfully desalinating water from the Caspian Sea since October 1963 in the town of Shevchenko in the Soviet Union. This plant(ll) uses a system for recirculating the chalk seed with external zones of boiling in the evaporator equipment. The design of this plant alows for the possibility of operating it not only with extraction steam from the turbines at a pressure of 5-6 atm, but also with water heated to 150°C from a water-heating boiler. The distillate is fed, into the town water supply system. In addition to its operation as an industrial plant, water desalination schemes are being developed on it for future application to a fast reactor dual-purpose nuclear plant being constructed at Shevchenko. A detailed description of the plant has been given elsewhere( During its two-year running period, the plant has shown itself to be simple and reliable in operation and stable with respect to coolant parameter variations down to the point where a prolonged cessation of intake occurs. The more important characteristics of the 4-stage desalination plant at Shevchenko(16) are given below: Productive capacity for distillate(toMe/br) 200-210 Sea-waterboiling temperature (“C) in the 6rst stage 106-110 in the fourth stage 45-50 Salt content of concentrated sea-waterat plant outlet (kg/m’) 40-45 Seed concentration (kg/m*) in the lirst stage lo-15 in the fourth stage 40-42 Heat-transfer coefficients,kcal/m* . hr. deg. in the first stage 2700-2800 in the fourth stage 2100-2200 Salt concentration of distillate (mgll) in the first and second stages
Nuclear power and the desalination of salt waters
599
greater than the cost of the softened water because the system used to interconnect the evaporators leads to almost no heat losses (a very small fraction of the heat is lost to the blow-through water and to the external cooling). In addition, the complete automation of the plant eliminates the need for operating staff. The prime cost of the distillate is 9421.6 copecks/tonne (16),depending on the operating conditions and running schedules of the plant. Several papersu7-20) were devoted to problems connected with the desalination of salt and brackish waters by methods which do not involve distillation (electrodialysis, gas-hydrate, ion exchange). MAL’TSEV(~~) considers the feasibility of desalinating salt-water by distillation using a hydrophobic coolant. The essence of the method is to effect a contact heat exchange between a hydrophobic heat-transfer agent and the liquid being desalinated with subsequent separation of the distillate, hydrophobic coolant and brine. The heattransfer agent consists of diphenyl mixtures and parafhn. This type of thermaldesalination plant has a number of advantages which suggest that such plants may have a promising future when used in conjunction with nuclear reactors, but so far this method has not passed beyond the laboratory and test-rig stage. A rather different topic is discussed in a paper by SHTANNIKOV(~~). This concerns the medical and biological aspects of the use of desalinated water which arise in connexion with the numerous methods of desalination based on the use of chemically active polymers, and of substances used in water technology which have received scant attention from toxicologists. The author points out that from the medical and biological point of view the majority of existing methods for desalinating water require additional measures to be taken in order to improve the quality of the water. Such measures are quite practicable and are comparatively simple. Finally, in a paper by KLYACHKO(~),a review is given of the U.S.S.R. work on desalinating salt and brackish water, including descriptions of the methods being used. The papers presented by the U.S.S.R. to the First International Symposium on show that the Soviet Union is engaged in research on these Water Desalination problems along a wide front. The use of heat provided by nuclear reactors is an entirely feasible and economically desirable method of obtaining fresh water on a large scale in regions of the U.S.S.R. which suffer from a water shortage. REFERENCES 1. KORYAKINYu. I. et al. Atomn. Energ. 19, 138(1965). 2. L~GINOVA. A. et al. An Analysis of the Technical and Economic Indices of Nuclear Power3. 4. 5.
6.
Producing Desalination Plants, Paper No. SWD/56, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965) SINEVN. M. et al. Proceedings of the Third International Conference on thepeaceful Uses of Atomic Energy, Geneua, Vol. 1, p. 80. United Nations, New York (1965). SERGEENKO I. L. Analysis of the Economics of High-Power Thermal Desalination Plants, Paper No. SWD/71, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). STERMAN L. S. and GUBENKOV. V. Analysis of the Thermal Economics of Power Generating Plants Incorporatiq Distillation Units of High Productive Capacity, Paper No. SWD/70, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). GOLUBKOV B. N. and KORNEICHWA. I. An Analytical Method of Determining the Optimum SteamParameters of Thermal Desalination Plants, Paper No. SWD/69, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965).
600
Yu.
I. KORYAKIN and. A. A. LOOINOV
7. GOLUB S. I. et al. An Analysis of Various Schemes for Distillation Desalination Plants and their Equipment Layout, Paper-No. SWD/76, presented by the U.S.S.R. at the First International Svmoosium on Water Desalination. Washineton. 3-9 October (1965). 8. Ko~Y~ Yu. I. et al. Use of Reactors Ofthe’Beloyarsk Type for Dual-Purpose Desalination Plants, Paper No SWD/57, presented by the U.S.S.R. at the First Znternational Symposium on Water Desalination, Washington, 3-9 October (1965).
9. D~~RIEV I. D. Application of Nuclear Power Plants to the Desalination of Salt Waters with Simultaneous Electricity Generation, Paper No. SWD/72, presented by the U.S.S.R. at the First International Symiosium on Water ~esalhation, W&>on, 3-9 October (1965). 10. POLUSHKINK. K. et al. Low Power Nuclear Desalination Plants. Paoer No SWD158. oresented by the U.S.S.R. at the First International Symposium on W&erLDesalination,’ W*&hington, 3-9 October (1965). 11, CHERNOZUBOVV. B. et al. Prevention of Scaling in Distillation Desalination Plants with the aid of Seeding, Paper No. SWD/64, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 12. CHERNOZUBOVV. B. et al. Intensification of Heat Exchange in Evaporator Plants, Paper No. SWD/62, presented by the U.S.S.R at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 13. KONSTANTINOVAE. V., SEMENOVAL. S. and D’YAKOV A. A. The Corrosion Resistance ofMaterials in Sea-Water, Paper No. SWD/73, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). M. M. Crevice and Pitting Corrosion of Stainless Steels in Chloride 14. FOKINM. N. and KURTEPOV Solutions at Temperatures up to lOO”C,Paper No. SWD/63, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 15. Z~osr~ovsrcn F. P. et al. The Distillation Desalination Plant at Shevchenko, Paper No. SWD/61, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 16. MAKINSKIII. Z. The Power Desalination Plant at Baku, Paper No. SWD/68, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 17. KLYACHKO V. A. et al. The Desalination of Salt Waters by Electrodialysis, Paper No. SWD/59, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). I. N. A Study of the Gas-Hydrate Process of Desalination, Paper 18. PAVLOV G. D. and MEDW?.DIW No. SWD/67, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 19. SMAGINV. N. Desalination of Salt Waters by the Ion-Exchange Method, Paper No. SWD/75, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). A. P. et al. Ionic Membranes for Salt Water Desalination and their Properties, Paper 20. PASHKOV No. SWD/74, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 21. MAL’TSEVE. D. Desalination of Sea-Water by the Distillation Method with the aid of a Hydrophobic Heat-Transfer Agent, Paper No. SWD/66, presented by the U.S.S.R. at the First Znternational Symposium on Water Desalination, Washington, 3-9 October (1965). E. V. Medical and Biological Aspects of Water Desalination, Paper No. SWD/65, 22. SHTANNIKOV presented by fhe U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 23. KLYA~HKO V. A. Research in the Field of Water Desalination in the U.S.S.R. Paper No. SWD/60, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965).
1967. Vol. 21. pp. 585 to 600.
NUCLEAR
Per&vmtoa Press Ltd.
printed in Northern Irclsnd
POWER AND THE DESALINATION OF SALT WATERS*? Yu.
I.
KORYAKIN
and A. A.
LOGINOV
(Received21 October 1965) INTRODUCTION As
A RESULT of the considerable success in recent years in the building of nuclear power reactors, interest has been growing in many countries of the World in the possibility of using nuclear reactors to augment the rapidly diminishing supplies of fresh water. The Soviet Union (or rather a number of its regions) is one of the large group of countries who are experiencing such a shortage of fresh water . The extent of the interest of the U.S.S.R. in solving this problem is brought out particularly clearly in the papers presented by the Soviet Union to the First International Symposium on Water Desalination. Altogether 21 papers were presented, covering a variety of aspects pertaining to the desalination of salt and brackish waters. The main object of the present article is to review those problems presented in these papers which relate to the economics, techniques and heat technology involved in using nuclear reactors in desalination plants employing the distillation method. The distillation method embraces two distinct techniques for desalinating salt water, namely evaporation and flash distillation, and it is the most suitable way of using nuclear reactors in atomic desalination plants. In this review, a general outline is also given of the technology of obtaining fresh water in the distillation type of desalination plant and methods are described of producing fresh water from salt and brackish waters which do not involve distillation (for example, electrodialysis and ion-exchange methods). ECONOMICS
OF
DESALINATION
The question of the economics of operating nuclear reactor desalination plants is naturally the one receiving most attention at the present time. There is no doubt at all that any of the several different types of power reactor which have proved themselves in actual operation could be used as the basis of a successful nuclear desalination plant. The reactor in a nuclear desalination plant is used as the heat source for distilling water with a heightened mineralization. In dual-purpose installations, the production of the distillate takes place simultaneously with the production of electrical energy, since the heat potential is high enough to generate steam with parameters suitable for driving a turbine. The question of the economics of dual-purpose nuclear desalination plants is a more complicated matter, however. Such installations have the special feature that two kinds of product are produced at one and the same time-the distillate and the * Translated by D. L. ALLAN from Atomnaya Energiya 20,232 (1966). $ Survey of papers presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 585
586
Yu. I. KORYAKIN and A. A. Locmov
electrical energy, Since the assessment of the production costs for these two types of product may be arrived at in different ways, there are good reasons for using various approaches and procedures when determining the economic indices of the installations. To find the conditions necessary for economically competitive dual-purpose nuclear desalination plants, the most acceptable method of calculating the technological and economic indices is one which enables comparisons to be made between installations incorporating different types of nuclear reactors and the conventional methods of generating electrical power and of producing fresh water. The proposed construction site should be taken into account but no account should be given to any local economic peculiarities of the region. These factors are the main ones to be considered during the economic and design studies of dual-purpose installations for the conditions existing in the U.S.S.R., where both of the products from dual-purpose plants are equally important from the point of view of the national economy. The procedure of analysis we adopt here has already been described elsewhere”). The essence of the method is to take the prime cost of the heating steam in nuclear dual-purpose plants as being equal to the cost of the lost electricity that could have been produced were the reactor operating in a condensing atomic power station. The annual cost of the lost electricity production is considered to be the cost of generating the heat of the steam used to distil the water. In this case the annual production costs of a dual-purpose plant are obtained by adding the electricity and distillate production costs. As in the case of a condensing atomic power station, the electricity production costs are found first by determining the prime cost of the electricity and then allowing for the lost electricity production and the small saving arising from the fact that some of the equipment needed in a condensing atomic power station will not be required. The distillate production costs are found by adding the production costs of the desalination section of the plant and the heating steam generation costs. A nuclear power source combined with a desalination plant represents a complex engineering installation characterized by a large number of heat technology, physics and technical indices which directly or indirectly affect the prime costs of the products. It is clear therefore that the optimization of the technical and economic factors involved in a dual-purpose nuclear plant would be an impossible task without the help of electronic computer techniques. L~GINOVet ~1.‘~)have given details of a methodical approach to this problem for three types of U.S.S.R. reactor, namely those at the Beloyarsk, Novo-Voronezh and Shevchenko nuclear power stations and for two versions of thermal installation in the desalination part of the plant, namely one with vertical evaporation equipment and one with flash distillation equipment. The method they describe is suitable for optimization purposes and permits comparisons to be made over a wide range of variation of the technical characteristics of both the reactor and the desalination sections of the plants. In addition, the capital outlay for the nuclear (including the power circuit) and the desalination sections are considered separately. With this approach to estimating the capital cost, one makes the best possible use of the available nuclear energetics data. It is also possible to allow for certain trends and economic peculiarities which are observed when the unit power of the reactors is significantly increased above that for existing reactors.
Nuclear power and the desalinationof salt waters
587
On the basis of the data published by SINEVet ,Z.c3)and by SBRGFXNKO(~), approximate relationships have been obtained (Table 1) giving the capital expenditure on the nuclear section of desalination installations as a function of the thermal power of the reactor, and also the dependence of the capital expenditure on the water purifying section as a function of distillate output for 7-stage vertical evaporators and for 30-stage flash-distillation installations. Table 1 also gives the prime cost of the electricity from condensation nuclear power stations, incorporating the reactors indicated, as a function of their thermal power for an installed power utilization coefficient equal to 0.8. Curves showing how the cost of the heating steam depends on the thermal power of the reactor for various heating steam temperatures are presented in Fig. 1. It is evident that for a reactor of the Novo-Voronezh type, the cost of the heat depends strongly not only on the thermal power of the reactor (up to ~2000 MW) but also on the temperature of the heating steam whereas, for a reactor of the Beloyarsk type, these dependences are less pronounced. This is explained by the higher steam parameters of the Beloyarsk type of reactor and, consequently, by the smaller effect introduced by the relative loss of electricity production. For the Shevchenko type of reactor, the steam heating costs depend markedly on the thermal power of the reactor and reach lower values in comparison with other types of reactor. Table 2 gives the preliminary, generalized results of an analysis which yielded the indices for dual-purpose plants. An analysis of the thermal and economic indices has been carried out also by several other authors.@-‘) The main interest here was the estimation of the thermal desalination section of dual-purpose plants; the nuclear section was hardly considered. Thus, SERGEENKO’analyses ~) three desalination layouts : (1) multi-stage flash evaporation with surface condensation; (2) multi-stage surface evaporation with non-surface (mixing) condensation; (3) once-through, sequential multiple evaporation. The dependence of the distillate costs on the number of stages of the plant was found for all three schemes for various assumed values for the cost of the heating steam. In addition, the dependence of the unit capital outlay on plant construction (referred to a productive capacity of 1 tonne/hr) on the number of stages for different iixed values of the other determining parameters was calculated. A procedure for determining the optimum heat economy for dual-purpose nuclear plants based on the use of a Novo-Voronezh type of reactor is explained by STEFMAN and GUBENKO(~).Results are also given of an analysis in which it was assumed that the coolant temperature was equal to that of the reactor at the Novo-Voronezh nuclear power station (275280°C). GOLUBKOVand KORNEICHEVw have obtained curves enabling one to find the basic technical indices of thermal desalination plants. They also give a method for making the technical and economic calculations needed for determining the optimum (for minimum outlay) parameters of thermal desalination plants, and have derived analytical expressions for determining the optimum number of evaporation stages and the optimum amount of sub-cooling of the water in the surface condensers. Three types of desalination layout were examined: (i) with surface evaporators (with a falling film); (ii) with flash distillation; (iii) with a hydrophobic coolant. Whereas the last three pape#+ are of a rather theoretical nature, the aim of the paper by GOLUBet ~1.“) is to give a comparative appraisal confined to those thermal
C a* - 87-45 x exp (-1.195 x lo-’ Qr) [million roubles]
[q=ks/kW . hl
csms = 0.457 + 3.8 exp (-0.418 x lo-‘QI)
Beloyarsk Nuclear Power Station
Qr
*w
rcopeckslkw. hl
Cfme = 3442 x Qr-I’“”
C caD= 87-45 C csp - 107~2.5 x ex (-0.73 x lO+ Q,) x exp (-0.982 x lo-” Q,) [million roubles] Pmillion roubles]
bp=wkw
cg&, = 0.457 + 3.8 exp (-a253 x lo-‘Q,>
c&t = 1800 + 44.75 x lo” G-o“*’ [roubles/torme/hr]
7-stage equipment (evaporation)
c&t = 2210 + 218.2 x lo” G-e’6’s [roubles/tonne/hr]
3Mage e@pment @ash distlllatioll)
G = (0.1-30) x lO’tonne/hr
AND CApmu Cosr c,., ON THE THERMAL CAPACITY OF THE DWllLLATB G
Shevchenko Nuclear Power station
OF THE PFWE OF ELw;TRIcITy Cgime OF TEE REACKJR AND ON THE PRODU~
Nuclear Power station
Q’
POWER
TABLE l.-D~NDENCE
?
E ?
Q
%
L
Nuclear power and the desalination of salt waters
0.50
500
1000
I500 Q ,*
050
0
500
500
1000
1000
1500
1500
a r.
2500
2000
2500
2000
2500
MW of the cost C, of the heating steam on the thermal power of the (a) Beloyarsk t of reactor; (b) Novo-Voronezh type of reactor; (c)y!ehevchenko type of reactor.
FIG l.-Dependence
reactor Q.:
2000 MW
YIJ. I. KORYAKINand A. A. LOGINOV
590
TABLET.-TECHNICAL
Type of reactor Novo-Voronezh Nuclear Power Station
Steam temperature (“C)
750
100 120 100 120 100 120 100 120
135 108 270 216 338 271 405 324
100 120 140 100 120 140 100 120 140 100 120 140
242 235 228 485 470 456 606 588 570 727 706 684
100 120 140 100 120 140 100
242 235 228 485 470 456 606
120 140 100 120 140
588 570 727 706 684
1500 1875 2250
Beloyarsk Nuclear Power Station
760 1520 1900 2280
Shevchenko Nuclear Power Station
Useful electrical
Thermal power (Mw)
760 1520
1900 2280
gq
Capital cost of nuclear section [million roubles]
Prime cost of electricity (copecks/ /kW . hr)
61.0
1.012
71.9
0.542
75.6
0.488
78.3
O-470
68.9
0609
79.3
0.464
82.3
0.458
84.0
o-457
86.9
O-736
97.4
0.300
100.4
0.233
102.5
0.177
AND ECONOMIC
Prime cost of heating Heat for steam desalination (cope&/ (g-cal/hr) g-cal/hr) 494 509 988 1018 1235 1272 1482 1527 368 373 380 735 747 .-760
153.5 203.0 83.0 108-O 74.8 97.6 71.9 94.0 96.0
934 950 1104 1121 1140
106.0 115.3 73-l 80.9 88-O 72.2 79.8 87.0 72-O 79.6 86.7
368 373 380 735 747 760 920
116-O 128-O 139.5 47.0 52.3 57.7 36-5
934 950 1104 1121 1140
z.: 27.7 30.6 33-5
920
* Flash distillation. t Evaporation.
desalination schemes which could actually be built now and which could be operated with reasonably good efficiency. According to these authors(‘), such schemes are the following: (a) flash distillation schemes with preliminary acid treatment of the intake water to prevent salt-deposition; (b) flash distillation with re-cycling of the sea-water and acid treatment, or with the addition of seeding crystals; (c) evaporation in vertical long-pipe equipment with a falling fihn together with a preliminary acid treatment of the intake water; (d) evaporation with natural circulation and evaporation with forced circulation of sea-water accompanied in both cases by seeding with crystals. A comparative analysis was made with respect to thermal economics, the conditions for preventing salt-deposition, cost of equipment and reliability. The authors conclude that for the conditions prevailing in the U.S.S.R., and within the range of productive capacity of fresh water considered, the flash distillation
Nuclear power and the desalinationof salt waters INDICES OF DUAL-PURPOSE
Distillate productive
PLANTS
Prime cost of
Capital cost of desalination
distillate without allowing for heat (copecks/toMe) Flash Vertical
SWtiOll
(lO-%$a,,, Flash* Vertical?
591
[million roubles] Flash Vertical
Prime cost of distillate (cope&s/tonne) Flash Vertical
Type of reactor
166.5 168.0 333.0 336.0 418.0 490.5 502 564
139.2 143.8 278.4 287.6 349.5 359.0 419.5 430.5
18.4 20.4 34.6 38.7 42.6 47.6 50.6 565
11.5 11.8 22.2 23.0 27.7 28.5 33.0 34.0
7.87 7.79 7.57 7.53 7.49 7.46 744 741
5.96 5.94 5.83 5.83 5.81 5.81 5.78 5.78
18.67 20.99 13.46 14.57 12.80 13.81 12.54 13.52
19.01 2324 12.89 14.99 12.15 14.02 11.89 13.77
Nova-Voronezh Nuclear Power Station
204.2 381.0 429.0 249.3 2760 285.7 311.3 344.7 357.2 374.0 416.0 428.0
103.8 105.2 107.3 207.1 211.0 214.8 259.2 263.8 267.2 312.1 317.0 322.0
14.3 15.7 16.1 26.4 29.1 30.0 32.4 35.7 36.8 38.4 42.4 43.7
8.8 8.9 9.0 16.8 17.1 17.4 20.8 21.1 21.5 24.8 25.2 25.6
8.06 8.02 8.00 7.68 7.65 7.64 7.61 7.57 7.56 752 7.49 7.48
6.05 605 6.04 5.89 5.89 5.88 5.85 585 5.84 5.83 5.83 5.83
14.88 14.91 15.36 12.87 1290 13.27 12.72 12.76 13.13 12.62 1265 13.02
14.21 15.06 15.84 12.10 12.76 13.36 11.99 12.62 13.23 11.95 12.59 13.19
Beloyarsk Nuclear Power Station
204.2 381.0 429.0 249.3 2760 285.7 311.3 344.7 357.2 374.0 416.0 428.0
103.8 105.2 107.3 207.1 211.0 214.8 259.2 263.8 267.2 312.1 317.0 3220
14.3 15.6 16.1 26.4 29.1 30.0 32.4 35.7 36.8 38.4 42.4 43.7
8.8 8.9 9.0 16.8 17.1 17.4 20.8 21.1 21.5 24.8 25.2 25.6
8.06 8.02 .;::
6.05 6.05 6.04 5.89 5.89 5.88 5.85 5.85 5.84 5.83 5.83 5.83
16.31 16.35 16.94 11.01 11.05 11.33 10.20 10.19 10.37 9.49 9.47 9.69
15.90 16.95 17.89 9.89 10.33 10.78 8.95 9.29 9.58 8.20 8.43 8.68
Shevchenko NUClWU Power Station
7.65 764 7.61 7.57 7.56 7.52 7.49 7.48
method was not quite so competitive conclusion
economically
as the evaporation
method.
This
is in accord with the results of LOGINOV et ,Z.@) and is also partly in
accord with the findings of SERGEENKO(*) and it is based on the fact that
one has had more experience in operating evaporation equipment compared with flash distillation equipment. However, because of the increased productivity of desalination plants when operated in conjunction with reactors having thermal powers of the order 2-3000 MW, the economic indices of these two types of plant will eventually become comparable. With an even greater increase in the thermal power of the reactor, the advantage will evidently lie with the flash distillation plants. POSSIBLE
TECHNICAL
SOLUTIONS
KORYAKIN et ,Z.@) have attempted to estimate the technical and economic characteristics which a relatively high-power dual-purpose nuclear plant with a Beloyarsk 4
Yu. I.
592
and A. A. L~GINOV
KOXYMIN
type of reactor would have. This type of reactor belongs to the channel class and is capable of developing a high unit thermal power, this being one of the decisive conditions for attaining the break-even point with nuclear dual-purpose plants. Other factors in favour of this type of reactor are that the coolant loop presents no radiation hazards, it has high efficiency (ensuring a high production ratio of electricity to distillate), the fact that one can use standard steam power equipment, there is a reasonably efficient nuclear fuel utilization, there exists a considerable amount of experience in the planning, construction and operation of such a reactor. All these considerations lead one to believe that a promising future lies ahead for dual-purpose nuclear plants. We considered two technological schemes: (1) a scheme with sub-critical coolant parameters (90 atm, 535’0; (2) a scheme with super-critical parameters (240 atm, 535/535’C). The first scheme is illustrated in Fig. 2. Both schemes make use of a 363
tonne/
hr.
90
otmos,
535%
,
298
5 \c
17.7 tonne/hr,
31.2
16.2 tonne /hr. 19.5 atmos,
2
I I.6 363
tonne/hr,2,0
atmos,
12O’C
atmos,404T
346T
8.7 tonne / hr, atmos 294’C
7.8 tonne/ 6.0 atmos
hr,
‘14 IO
FIG. 2.-Basic diagram of the thermal circuit of the power loop of a plant incorporating a Beloyarsk type reactor with a thermal power of 520 MW: l-reactor; 2-evaporator channels; 3-superheating channels; 4-separator drum; 5-preheater; 6-turbine; 7-generator; 8-condenser-sea-water boiler; g-condensation pump; lO-regenerative pre-heater; 1l-de-aerator; 12-feed pump; 13-circulating pump; !Athrottle. flash-distillation installation in the desalination section of the plant. Below we give the results of a calculation of the fundamentaleconomicindices of dual-purpose plants incorporating a Beloyarsk type of reactor:
30-stage
Thermal power of reactor (MW) Electrical power (MW) Heat consumed in distillation (kcal/br) Distillate production (tonne@) Capital outlay on electricity generating section of plant (millions of roubles) Prime cost of electricity (copecks/kWh) Capital outlay on desalination section of plant (millions of roubles) Prime cost of distillate without allowing for cost of heat @pecks/ tonne) Unit heat consumption expended on distillate &xl/kg) Prime cost of heat for the heating steam (copecks/g-cal) Prime cost of distillate (copecks/tonne)
90 atm 520 150 312 x 10’ 4.8 x 10’
240 atm 1950 600 1080 x 10” 16.8 x 108
62.5 1.060
83.0 0.458
13.35
40.60
8.11 65 170 19.12
7.43 64 127 13.57
Nuclear power and the desalination of salt waters
593
In most cases, the design specifications of dual-purpose nuclear plants call for the use of back-pressure turbines. Although such turbines have their advantages they have also a number of disadvantages; in particular, the lack of flexibility in operation of dual-purpose plants arising from the fact that the productive capacity for the distillate is rigidly tied to that for the electricity during possible appreciable fluctuations of the power and thermal loads. Greater flexibility can be provided if turbines with controllable steam extraction are used. For this reason, in the paper by DMITRIEV(~), turbines with controllable steam extraction were specified in all the schemes considered. Three schemes for dual-purpose plants were compared employing reactors of the Beloyarsk, Novo-Voronezh and Shevchenko types with identical fresh-water outputs (95 million m3/year) but with different electrical power outputs. The comparison was made with respect to the total capital costs (with a breakdown into consolidated items of expenditure) and with respect to a nominal distillate selling price for an assumed electricity selling price. It was concluded that for the highest water productivity the best scheme from the economic point of view is a version of a plant with a fast reactor of the Shevchenko type (Fig. 3). As well as high-power nuclear desalination plants, there is interest also in building nuclear desalination plants of relatively low power (producing 150-500 tonne/hr). The need for such plants is determined by the geographic and economic peculiarities of a number of regions and locations where fresh water conveyance is difficult and where the transport of conventional fuels for salt-water distillation and electricity generation involves considerable expense. In addition, in some cases, a desalination plant may be required to play a single-purpose role. POLUSHKIN et uZ.(~O) have considered the possibility of building low-power desalination plants, the prototype of which is the ARBUSplant (where the coolant is hydroterphenyl) with the use of multiple sequential evaporation. The basic scheme of the plant is shown in Fig. 4. These authors analysed plants incorporating reactors with thermal powers equal to 15,30 and 70 MW. The organioorganic type of reactor is more suitable for installations based on reactors with thermal powers up to 30 MW; for higher power reactors it is more efficient, from economic considerations, to use reactors with an organic coolant and a solid moderator. The basic technical and economic indices of these plants (calculated according to the procedure described by Koryakin) are given in Table 3. The equipment and individual components of the plant can be delivered to the construction site in the form of separate, completely assembled units which have already been tested at the factory where they were manufactured. The weight and dimensions of the units are such that they can be delivered to the site by any form of transport (the weight of the units does not exceed 20 tonne). The plant is housed in a prefabricated building with a frame-shield type of construction. ECONOMIC
COMPETITIVENESS
We have discussed above the prime costs of the electricity and distillate for large capacity nuclear desalination plants incorporating various types of reactor. These costs permit one to assess the economic effectiveness of dual-purpose nuclear plants, i.e. the costs of producing the electricity and distillate. The procedure we used(l) for allocating the cost enables us to avoid the uncertainties in calculating economic indices of dual-purpose installations which arise when one designates the
Yu. 1. KORYAKINand A. A. LOGINOV
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TABLE3.-TECHNICAL AND ECONOMIC INDICESOF DESALJNATION PLANTS
Characteristics Useful electrical power (kw) Plant power requirements (kW) Heat consumed by desalination process (lccaljhr) Unit heat consumption expended on distillate (kcal/hr) Distillate production (tonne/h@ Capital cost of desalination section (million roubles) Total capital cost of plant (million roubles) Prime cost of electricity (copecks/kW . hr) Prime cost of distillate (copecks/tonne)
Thermal power of reactor (Mw) 15 30 70 400 11 x 106 86.7 127.5 0.493 2.093 68
7.50 22 x 10” 867 2550 0.801 3.201 57
1500 1500 43.8 x lOa 86.7 505 1.350 4650 2.1 42
FIG. 4.-Basic diagram of thermal circuit of a desalination plant incorporating an Aanus-type reactor: l-reactor; 2-steam generator; 3-evaporator (first stage); 4-volume compensator; 5-receiver; 6-regeneration unit; 7-evaporator; S-condenser; g-settling tank.
cost of the electricity (price fixing), as is done abroad. Price-fixing of any of the products for the purpose of estimating the economics of dual-purpose plants during the design stages of the project precludes one from analysing the effect of individual technical characteristics on the prime costs of the distillate and electricity, although this aspect is very important. Moreover, when the conditions are such that both products are equally important from the point of view of the national economy (and this is typically the case for the U.S.S.R.), to make one product cheaper at the expense
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of the other is inadmissible. Finally, at the present time, it is being suggested that one should approximate the costs to the level demanded by the needs of the community, and this makes price fixing impossible. In the actual operation of dual-purpose plants it may prove expedient to vary the nominal selling prices of the electricity and distillate within the limits of the total production costs of these two products. In that case one could fix the nominal selling price of one of the products on the basis of commercial considerations. This automatically ties the selling price of the other product since the total costs of producing the distillate and the electricity naturally remain unchanged for each plant regardless of the way in which the individual prices are allocated between them. Another similar approach is to regard the dual-purpose plant as a cost-accounting concern. In that case one should fix the nominal electricity selling price from the standpoint of the average net cost of the electricity in the power grid, since a high-power dual-purpose plant will presumable be comected into the power grid. Figure 5 gives graphs plotted from the data of Table 2 showing the dependence of the selling price of the distillate on the selling price of the electricity for the case of dual-purpose plants with vertical equipment incorporating reactors of the Beloyarsk, Novo-Voronezh and Shevchenko types, with equal thermal powers (1500 MW) and steam temperatures (120°C). Points corresponding to the prime costs of the electricity and distillate are plotted on the graphs. 40
C,,
copecks
/ kW hr
FIG. 5.-Dependence of the selling price of the distillate Ca on the selliig p&e of the electricity C, for dual-purpose plants incorporating various reactors: O-calculated points corresponding to the data given in Table 2; 1Shevchenko type of reactor; 2-Beloyarsk ty-pe of reactor; 3-Novo-Voronezh type of reactor.
The drop in the distillate selling price due to increasing the electricity selling price is greatest when reactors ensuring high initial steam parameters are used, since they have a high ratio of electricity output to distillate output (Beloyarsk and Shevchenko nuclear power stations). This is due to the fact that in reactors with high initial steam parameters a greater fraction of the available heat transfer is used for electricity production. Another economically advantageous way of increasing the absolute output of electrical power for a given distillate production capacity is to employ both condensing and back-pressure turbines in a dual-purpose nuclear plant. An additional
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advantage of such a combination plant is its greater flexibility should any n&match arise between the electricity and distillate load graphs. For reactors working with saturated steam, the choice of the initial steam pressure turns out to have no substantial effect upon the prime cost of the electricity and distillate; the effect of increasing the selling price of the electricity with the aim of decreasing the selling price of the distillate for this type of reactor is considerably less than for reactors working with superheated steam. It should be emphasized that under present-day conditions, when the development of nuclear power has reached a point where the prime cost of the electricity produced is only marginally competitive with that of electricity from conventional sources, there is little scope for reducing the distillate selling price at the expense of raising that of the electricity, and the economic effect of such a measure is negligible. DISTILLATION
TECHNOLOGY
The reports on distillation plant technology presented at the symposium are concerned with two of the most important problems, namely heat exchange and the corrosion of materials in sea-water. CHERNOZUBOV et uL(~) have generalized the results of their work since 1954 on the prevention of precipitation of scale on heat-exchanging surfaces (which causes an abrupt deterioration in the heat exchange and, consequently, of the distillate production capacity) in which they added a seeding material to the sea-water in the form of finely ground natural chalk. As a result of a long period of working with both laboratory and semi-industrial scale plants, these authors have been able to show that the use of seeding under conditions such that the boiling section is taken beyond the heat-exchange limits is a reliable and guaranteed method for the complete prevention of scale formation on heat-exchange surfaces. An intensification of the heat-exchange leads to a substantial improvement of the economic indices for operating distillation desalination plants. Investigations discussed in another paper by CHERNOZUBOVet CZ~.(~~) were conducted along the following lines: (1) the elimination of the harmful effects of non-condensible gases in the heating steam on the heat transfer coefficient during condensation by inducing a turbulent steam flow which destroys the steam-gas layer in the vicinity of the heating surface; (2) inducing rain-like condensation of the steam on the heating surfaces by making use of hydrophobic substances to stimulate rain-like condensation; (3) devising economic methods of raising the heat-transfer coefficient from the side of the liquid in the heat-exchange equipment by jet-feeding the liquid (experiments showed that it was possible to increase ccto (30-35) x 103 kcal . /m2. hr. deg). KONSTANTINOVA et LzL(~~)have studied the corrosion of materials in water from the Caspian Sea, which has a high oxygen content. They conclude that amongst the cheapest and most readily available constructional materials for use in desalination plants, one can recommend St.3 carbon steel (provided that the sea-water is de-aerated and that there is no contact with electropositive materials) and alloys with a copper base LO70-1, MNZhS-1, LA 77-2 (for heating pipes). An eighteen months test of pipes made of LO70-1 brass in an industrial plant revealed no corrosion damage. Investigations carried out by FOKIN and KURTEPOV(~~) on the corrosion of stainless steels in an acidified 3 per cent solution of sodium chloride showed that the molybdenum stainless steel Khl7Nl3MZT has a greater resistance to failure caused by
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pitting than KhlSNlOT stainless steel. The same result was obtained in a study of crevice corrosion of these steels. DESALINATION PLANTS NOW OPERATING A Cstage industrial plant has been successfully desalinating water from the Caspian Sea since October 1963 in the town of Shevchenko in the Soviet Union. This plant(ll) uses a system for recirculating the chalk seed with external zones of boiling in the evaporator equipment. The design of this plant alows for the possibility of operating it not only with extraction steam from the turbines at a pressure of 5-6 atm, but also with water heated to 150°C from a water-heating boiler. The distillate is fed, into the town water supply system. In addition to its operation as an industrial plant, water desalination schemes are being developed on it for future application to a fast reactor dual-purpose nuclear plant being constructed at Shevchenko. A detailed description of the plant has been given elsewhere( During its two-year running period, the plant has shown itself to be simple and reliable in operation and stable with respect to coolant parameter variations down to the point where a prolonged cessation of intake occurs. The more important characteristics of the 4-stage desalination plant at Shevchenko(16) are given below: Productive capacity for distillate(toMe/br) 200-210 Sea-waterboiling temperature (“C) in the 6rst stage 106-110 in the fourth stage 45-50 Salt content of concentrated sea-waterat plant outlet (kg/m’) 40-45 Seed concentration (kg/m*) in the lirst stage lo-15 in the fourth stage 40-42 Heat-transfer coefficients,kcal/m* . hr. deg. in the first stage 2700-2800 in the fourth stage 2100-2200 Salt concentration of distillate (mgll) in the first and second stages
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greater than the cost of the softened water because the system used to interconnect the evaporators leads to almost no heat losses (a very small fraction of the heat is lost to the blow-through water and to the external cooling). In addition, the complete automation of the plant eliminates the need for operating staff. The prime cost of the distillate is 9421.6 copecks/tonne (16),depending on the operating conditions and running schedules of the plant. Several papersu7-20) were devoted to problems connected with the desalination of salt and brackish waters by methods which do not involve distillation (electrodialysis, gas-hydrate, ion exchange). MAL’TSEV(~~) considers the feasibility of desalinating salt-water by distillation using a hydrophobic coolant. The essence of the method is to effect a contact heat exchange between a hydrophobic heat-transfer agent and the liquid being desalinated with subsequent separation of the distillate, hydrophobic coolant and brine. The heattransfer agent consists of diphenyl mixtures and parafhn. This type of thermaldesalination plant has a number of advantages which suggest that such plants may have a promising future when used in conjunction with nuclear reactors, but so far this method has not passed beyond the laboratory and test-rig stage. A rather different topic is discussed in a paper by SHTANNIKOV(~~). This concerns the medical and biological aspects of the use of desalinated water which arise in connexion with the numerous methods of desalination based on the use of chemically active polymers, and of substances used in water technology which have received scant attention from toxicologists. The author points out that from the medical and biological point of view the majority of existing methods for desalinating water require additional measures to be taken in order to improve the quality of the water. Such measures are quite practicable and are comparatively simple. Finally, in a paper by KLYACHKO(~),a review is given of the U.S.S.R. work on desalinating salt and brackish water, including descriptions of the methods being used. The papers presented by the U.S.S.R. to the First International Symposium on show that the Soviet Union is engaged in research on these Water Desalination problems along a wide front. The use of heat provided by nuclear reactors is an entirely feasible and economically desirable method of obtaining fresh water on a large scale in regions of the U.S.S.R. which suffer from a water shortage. REFERENCES 1. KORYAKINYu. I. et al. Atomn. Energ. 19, 138(1965). 2. L~GINOVA. A. et al. An Analysis of the Technical and Economic Indices of Nuclear Power3. 4. 5.
6.
Producing Desalination Plants, Paper No. SWD/56, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965) SINEVN. M. et al. Proceedings of the Third International Conference on thepeaceful Uses of Atomic Energy, Geneua, Vol. 1, p. 80. United Nations, New York (1965). SERGEENKO I. L. Analysis of the Economics of High-Power Thermal Desalination Plants, Paper No. SWD/71, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). STERMAN L. S. and GUBENKOV. V. Analysis of the Thermal Economics of Power Generating Plants Incorporatiq Distillation Units of High Productive Capacity, Paper No. SWD/70, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). GOLUBKOV B. N. and KORNEICHWA. I. An Analytical Method of Determining the Optimum SteamParameters of Thermal Desalination Plants, Paper No. SWD/69, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965).
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7. GOLUB S. I. et al. An Analysis of Various Schemes for Distillation Desalination Plants and their Equipment Layout, Paper-No. SWD/76, presented by the U.S.S.R. at the First International Svmoosium on Water Desalination. Washineton. 3-9 October (1965). 8. Ko~Y~ Yu. I. et al. Use of Reactors Ofthe’Beloyarsk Type for Dual-Purpose Desalination Plants, Paper No SWD/57, presented by the U.S.S.R. at the First Znternational Symposium on Water Desalination, Washington, 3-9 October (1965).
9. D~~RIEV I. D. Application of Nuclear Power Plants to the Desalination of Salt Waters with Simultaneous Electricity Generation, Paper No. SWD/72, presented by the U.S.S.R. at the First International Symiosium on Water ~esalhation, W&>on, 3-9 October (1965). 10. POLUSHKINK. K. et al. Low Power Nuclear Desalination Plants. Paoer No SWD158. oresented by the U.S.S.R. at the First International Symposium on W&erLDesalination,’ W*&hington, 3-9 October (1965). 11, CHERNOZUBOVV. B. et al. Prevention of Scaling in Distillation Desalination Plants with the aid of Seeding, Paper No. SWD/64, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 12. CHERNOZUBOVV. B. et al. Intensification of Heat Exchange in Evaporator Plants, Paper No. SWD/62, presented by the U.S.S.R at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 13. KONSTANTINOVAE. V., SEMENOVAL. S. and D’YAKOV A. A. The Corrosion Resistance ofMaterials in Sea-Water, Paper No. SWD/73, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). M. M. Crevice and Pitting Corrosion of Stainless Steels in Chloride 14. FOKINM. N. and KURTEPOV Solutions at Temperatures up to lOO”C,Paper No. SWD/63, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 15. Z~osr~ovsrcn F. P. et al. The Distillation Desalination Plant at Shevchenko, Paper No. SWD/61, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 16. MAKINSKIII. Z. The Power Desalination Plant at Baku, Paper No. SWD/68, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 17. KLYACHKO V. A. et al. The Desalination of Salt Waters by Electrodialysis, Paper No. SWD/59, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). I. N. A Study of the Gas-Hydrate Process of Desalination, Paper 18. PAVLOV G. D. and MEDW?.DIW No. SWD/67, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 19. SMAGINV. N. Desalination of Salt Waters by the Ion-Exchange Method, Paper No. SWD/75, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). A. P. et al. Ionic Membranes for Salt Water Desalination and their Properties, Paper 20. PASHKOV No. SWD/74, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 21. MAL’TSEVE. D. Desalination of Sea-Water by the Distillation Method with the aid of a Hydrophobic Heat-Transfer Agent, Paper No. SWD/66, presented by the U.S.S.R. at the First Znternational Symposium on Water Desalination, Washington, 3-9 October (1965). E. V. Medical and Biological Aspects of Water Desalination, Paper No. SWD/65, 22. SHTANNIKOV presented by fhe U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965). 23. KLYA~HKO V. A. Research in the Field of Water Desalination in the U.S.S.R. Paper No. SWD/60, presented by the U.S.S.R. at the First International Symposium on Water Desalination, Washington, 3-9 October (1965).