m
..-
-
-
.
:
:
.
LOFT
ORNL P.
2071
:
.
:.
.
O
e
..
$
*
;
4
EEEFE EEE
I
...
?
LOGO
MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARDS -1963
"
Otrier P-2011 MASTER syntes

uraft:
CONF - 6603162
CFSTI PRICES
1966
H.C. $ 1.00; MN .50
MAY 5
-
-
AGRICULTURAL WATER BY NUCLEAR DESALINATION
AND TECHNICAL ROUTES TO ITS ACHIEVEMENT
-

L .
li T
.
RELEASED FOR A ROUNCE KNI
2 1.
-
-.
IN KUALZAR SCIENCE ABSTRACTS
..!
! VIE W-
R. Philip Hammond, Director
Nuclear Desalination Program
Oak Ridge National Laboratory
Oak Ridge, Tennessee
.
LEGAL NOTICE
This report was prepared as an account of Government sponsored work. Neither the United
States, por the Commission, nor any person acting on beball of the Commission:
A. Makes any warranty or representation, expressed or implied, wtih respect to the accu-
racy, completeness, or usefulness of the information contained in this report, or that the use
of any information, apparatus, method, or process disclosed in this report may not infringe
privately owned rights; or
B. Assumes any liabilities with respect to the use of, or for damages resulting from the
use of any information, apparatus, metbod, or process disclosed in this report.
Ao used in the above, "person acting on behalf of the Commission" Includes any em-
ployee or contractor of the Commission, or employee of such contractor, to the extent that
sucb employee or contractor cf the Commission, or employee of such contructor prepares,
disseminates, or provides access to, any information pursuant to his employment or contract
with the Commission, or dio employment with such contractor.
For Presentation at
ANS Symposium on "Water Production Using Nuclear Energy"
The University of Arizona
Tuscon, Arizona
March 30, 31, and April 1, 1966
Research sponsored by the U. S. Atomic Energy Commission.
under contract with the Union Carbide Corporation.
with deliberation
A i
!
sil
------
Draft
3/24/66
---
AGRICULTURAL WATER BY NUCLEAR DESALINATION
AND TECHNICAL ROUTES TO ITS ACHIEVEMENT
-------------
R. Philip Hammond, Director
Nuclear Desalination Program
Oak Ridge National Laboratory
Oak Ridge, Tennessee
..***- arst-
The application of nuclear energy to the task of desalting seawater.
(.
has changed in a few short years from a dream of a few to an importnat
.
t's
encer n
activity with dozens of firms and hundreds of engineers busily engaged.
piiri
,
..
The Metropolitan Water District of Southern California has just under-
.'.''
.
taken to construct the first major nuclear powered desalting station.
This station completes the transition of nuclear desalination from
dream to reality. There is no question but that an increasing number
-
Pyt
of cities around the world will find this kind of plant their best choice
?
for meeting new water demands.
As important as this development is for the future well-being of
cities, it becomes insignificant in comparison with the impact which a
successful application to large scale agriculture would have on the
destiny of mankind. If only a tenth of the world's need for new food
supplies in the next 30 years were met in this way, the growth of desalina-
tion reactors would rival or exceed the growth rate for electric power
reactors. In a previous article) I have explored the general feasi-
bility of providing nuclear desalination plants as major agricultural
sources. In this report I present some newly available information which
leads to a somewhat, more specific definition of the problem itself and
.....
of the nature which a successful solution will have. It must be made
......
.
clear at the outset, however, that not all the elements of the solution
are available, nor is it even clear that they can be found. My purpose
..
..........
.
-
.
.
.
.
. .
-
-
-
:.......
-
-
-
- -
-
-
:.
..
•
•
- 2.
in this report is essentially threefold: to define the nature of the
technical achievements which are missing, to underline their difficulty,
and to add my voice to those who are attempting to show how urgent it. :
is that we seek the goal in spite of its difficulties. ..
1. The Crisis in Food Supply.
In a country which has lately been concerned mainly with problems
* of food surplus it is difficult to make the imminence of a 'catastrophic
worldwide shortage of food seem very real or very near. Yet experts in
demography and food production and an increasing number of political and
scientific leaders are taking up the cry. Indeed, the facts are plain
and their meaning inexorable to anyone who takes the trouble to look at
them. I quote from a recent address) by the Hon. Frank Carlson, u.s..
Senator from Kansas:
.
.
"...the impending world crisis of mass starvation - a crisis which
is coming about at such an amazing pace that mir national attitude
and agricultural policies which, for 30 years, have centered upon
ways to deal with crop surpluses, must be abruptly and unmistakably :
changed. Abundant evidence – supported by cold facts – undeniably:
points to a world calamity, the true impact and effects of which
are terrifying to consider."
....:.: :
.............
The statistics of the increase of population and the growing defi-
.
ciency of food are readily available(3,4,5,6,7,8,9) and I will
..
.
peat them here. Their import can be summarized in a few statements :
.... ......::::: :,nimepiggerhana..
..
...
1) The world at present produces less food than an adequate
:.
.
:
minimum dieti requires.
.:
.....
..
.
:::
.
.
2) "The world has a very youthful population, and it is rapidly
getting younger, so that the doubling of the population within :
about 35 years seems certain, even allowing for the most....
optimistic success with birth control efforts.
...3) As a very minimum, the output of food must double within the
. next 30 years. .
....
.
:...
.
..
.
sam.neonors
- 3 -
4) In the past food output has been increased primerily by cul-
tivating more land, but this will no longer be possible. The .
warm, fertile, well waterea land is essentially all under culti-
vation, and only less favored or marginal 19nd is available. To
find enough for a doubling of the world food output is beyond
hope.
...
:
..
a)
The rapid dissemination of birth control iníormation and
materials is, of course, an important first step, but it
is not enough.
b) A number of measures have been proposed as partial solu-
tions to the food problem itself'. These include major
increases in world fertilizer output, attempts to control
weather and rainfall, major projects to develop and con-
trol water resources, development of methods of "farming"
the sea for fish, cultivation of tropical rain forests,
development of edibie algae, fed either in the sea or by
our petroleum resources, an all-out effort to increase the
yield per acre on presently cultivated land, and, finally,
bringing some of the immense areas of fertile arid land
into production using desalted water from the sea.
All of these methods have a certain amount of promise. But Dr.
Roger Revelle, Director of the Harvard Center for Population Stuły,
in a recent address to the Washington Colloquium on Science and Society,
stated that there was serious doubt whether even all of them together
-
4-
would be enough. The main problem, ne pointed out, was time. It takes
tizie to develop new agricultural techniques, tu educate illiterate
Tarrers, to develop new strains o: nia yield crops which can withstand
the fungus, insects, and other problems ci agriculture in the under-
developed countries. It will even take a considerable time to alert the
developed countries to the significance and extent of the problem and get.
them to corrmit the necessary resources to coinbat it. And yet the exponen-
tial nature of population explosions gives us very little time to initiate
any counter measures. We have, Dr. Revelle indicated, only about 10,
or at most, 15 years to to get anything we are going to attempt into
full scale action. An solution which arrives after that time will be
too late, since the pressures of the explosion itself will be starting
to be felt, and any rational activities inside the underdeveloped
countries may be impossible.
.
2. Arid Land Farming with Distilled water.
I shall not attempt to assess the various proposed measures
listed above, nor to relate the prospects for arid land cultivation to
the other methods; as Dr. Revelle says, all of them may be needed.
The cultivation of arid land has the major advantage, however, that
presently available crop varieties and farming techniques of the U..s.
.
arid West can probably be used. The use of desalinated water will it-
.
self dictate the preferred choices of irrigation technique, but these
will be adaptations of proven methods.
In order to assess the nature of such a route to major food supplies,
however, it is important to emphasize the major differences which this
type of agriculture would have from our usual farming methods. The
following list summarizes the salient points, most of which were developed
more fully in my previous article.
.....
.
....
........
...
...
1) The land used must have essentially a year-round growing season, :-
in order that the investment in water supply, water distribu-
tion, sprinklers, etc., can be used at high load factor.
2) Crop utilization of water must be high to minimize the consump-
tion of desalinated water. The U. S. Department of Agriculture,
Agricultural Research Service, has shown that cver 5000 pounds of
grain (wheat and corn) can be produced per acre foot of water
applied, and their experts have indicated that these results
should be readily transferable to the field conditions which
:
com
.
.
..
..
DO
.
would obtain in arid land irrigated with distilled water. Com- :
.
. .
.
pared with present average yields, such efficiency would be
equivalent to a 90% cut in the cost of water.
.
. .
.
Sprinkler irrigation would be preferred. In order to achieve
.
.
.
high efficiency of water use by the crop, water application must
.
.
.
be even and controllable. Sprinkler irrigation best meets.
.
.
.
these requirements, although for some crops and soils other
.
.
.
.
methods would be acceptable.
.
H)
The optimum amount of fertilizer should be used. The tests of
high efficiency of water use by the Agricultural Research Service
.
- 6-
showed that when less water is wastea, less fertilizer is wasted.
.
also, since there is little percolation below the root zone.
The fertilizer application must be made at the right time in the
growth cycle, so that the plant does not produce rank growth
IS
which would increase its ĝemand for water without increasing
yield.
5) With distilled water less drainage would be required. If
properly conducted with high efficiency of water use, farming
operations with distilled water should not require artificial
drainage in most soils. The high purity of the water means
that evapotranspiration will not increase the salinity of the
soil, so that after any initial salinity is flushed out, the
water table would not be expected to be greatly affected.
However, the process of initial leaching must be carried out
carefully, since too rapid an upset of the calcium-sodium ratio :
in the soil can lead to deflocculation and an impervious soil.
The proper' techniques for this leaching process are well known,
having been perfected by the Dutch in the reclaiming of their
polders.

- î -
3. Dual.- Purpose vs. Single-Purpose Water Piants.
If nuclear desalination is to have a major role in world food produc-
tion, it must be available in underdeveloped lands where agriculture is
..
still the principal activity. This means that, while some electric power
would be needed, the ratio of water to power would have to be much higher
.
than could be obtained fro:n present power reactors using back-pressure
.
."
,..
turbines, Table 1 shows several types of reactors, their steam condi-
tions, and the resulting values of w (Mga/Mwe), with 35 psia back pressure.
Table 1
Type
Steam Pres.
Temp.
R=10
Mga/Mwen
965
0.47
640
0.56
BWR (OC)
PWR (c.7.)
ETWOCR (AI-CE)
AGCN (PB)
SGR
900
0.46
540
493
725
1000
1000
760
0.44
1450
3500
576
0.21
0.69
Fermi
-
If, as seems likely, it will be essential to achieve higher values
of w, or even plants which produce no power other than their own require- .
ments, there are two main routes which appear feasible. One route is to use
the shaft energy of the back-pressure turbine to drive some other kind
of desalting process. The other route would be to develop evaporators
capable of high temperature operation and couple these directly to
special low-temperature or process-heat reactors. These two approaches to
.
a water-only or high w plant are shown schematically in the sketches below. .
The low-temperature evaporator referred to is the technology we have now,
in which the problems of scale formation and corrosion are fairly well :
understood up to a maximum brine temperature of about 250°F, which
would require a turbine back pressure of about 35 psia.
- 8 -
".indir?
1
na2

1
OVCI
Paciendo
-
-
.-.
-
.-
-
-
The upper diagram shows that for the first route the same reactor
could be used to produce energy for either a dual-purpose plant or a
.
water-only plant having two types of water conversion. The conventional
low temperature evaporator utilizing the 35 psia steam from the back-
pressure turbine is the same, but the shaft energy of the turbine drives
(a) an electric generator to give a dual-purpose plant, (b) a high pres-
sure water pump for a reverse osmosis plant, or (c) a steam compressor
or a freezing plant compressor.
- 9 -
The lower diagram shows a low-temperature process-heat reactor
which delivers heat directly to a high-temperature (325°F, for example).
evaporator. The lov temperature portion of this evaporator would, of
course, be very similar to the low temperature evapcrator in the upper
diagrari.
Let us examine briefly what we would have to accomplish to develop
a successful water-only plant with each of these approaches, as compared
with dual-purpose plants. As is clear from the diagram, the first route
woul, use the same type of reactor, turbine, and low temperature evapora-
tor as the dual-purpose plani, except that they must be larger and cost
less. The counterpart of the electric generator, however, does not exist
in a suitably developed form for the purpose. Of the several possibili-
jies, only the vapor compressor evaporator can so far be characterized
sufficiently to permit economic projections and to define the scope of
a development program. (The membrane and freezing processes, however,
must not be neglected. When sufficient engineering data are available,
they should be compared with the vapor compressor evaporator .)
The
heat transfer equipment used with a vapor compressor would represent
the same general block of technology as the exhaust steam evaporator.
The principal new element then is the compressor itself. Because of the
work which OSW has done at Roswell the operating factors for such com-
pressors are known. The development of several very large wind tunnels
in this country and the compressor technology developed at the Oak Ridge

Gasecus Diffusion flants make it possible to assess the aerodynamic
and engineering problems of developing a very large steam vapor compressor:
- 10 -
The second route requires two new major blccks of technical progress -
the low temperature reactor and the high temperature portion of the
evaporator. The high temperature evaporator is a relatively formidable
technical problem, since it requires a method ci controlling alkaline
and sulfate scales which is effective up to about 325°F and costs very
little to employ. It also requires suitable and inexpensive construc-
tion materials which will not corrode at the elevated temperature. The
low terperature or process-heat reactor would not have to explore new
realms of materials technology, but could probably count upon making use
primarily of information found in the course of power reactor development.
Yet it would still require a substantial development expense, since
the heat cost from such a reactor must be very low, and this would necessi-
tate detailed development and pilot scale trials of fuel manufacturing
and processing methods. A prototype reactor woulå also be necessary.
At first glance it would seen easy to make a selection between
these routes to water-uly technology. The cost of the vapor compressor
is a relative].y small item in the cost of water, and the main elements
of its development to large size already exist. The principal uncertainty
is whether this route would ever produce cheap enough water, since it
is clear that the water-only station must not only use a more expensive.
form of heat than a dual-purpose evaporator, but must support the cost
of the turbine and compressor to convert it for use. Thus, with the
sane cost for heat transfer surface, the vapor compressor plant can only
agproach but never equal the economics of the dual-purpose plant.
- ll-
The process deat reactor matched to a high temperature evaporator,
though requiring a more difficult development, holds strong promise of
ending up with lower cost water than a dual-purpose plant using a power
-
.
-
v
reactor enerzy source. There is not enough information at the present
-
time to make a correct choice between these two routes. The exigencies
of the world i'ood situation seem to comrel that both be explored through
some initial phase. The very short time available would make the vapor
compressor route attractive in order that a pilot food-growing experiment
could be set up as soon as possible. On the other hand, every decrease
in the cost of water would mean enormous savings of capital resources
if the use of such stations became widespread. Whether the cost can
be reduced low enough by any method is the paramount uncertainty of all.
Let us attempt to see how distant this goal might be by estimating the
value of agricultural water under present conditions, and then relate
this to present trends in water cost.
.
4. The Present Economic Value of Water in Agriculture.
In my previous paper cited above I have shown that several methods
can be used to show the range of prices that farmers of high value crops :
can afford to pay for water. One extreme is shown by areas such as
Israel, Egipt, etc., where local conditions make export crops profit-
able with water costing over $100 per acre foot, especially if it can be
blended with brackish water. Such cases need not concern us here, except'.
...
.
to show that the market for agricultural water overlaps substantially
the market for municipal and industrial water. In the United States
:
the range of prices actually paid by private irrigators extends up to
$45 per acre foot.
A
- 12 -
The large western irrigation projects in the U. S. are arranged so
that title to the land carries with it right to purchase project water
at a determined price. The extent that land values in such areas have
risen above the cost of preparing the zround provides a measure of the
economic value of the water rights. Such a calculation indicates that
Colorado River water is worth from $30 to $50 per acre foot to an effi-
cient irrigator in the Southwest, if his investment in land were only
the cost of preparation. This checks well enough with the $45 figure
mentioned above.
V. W. Ruttan in a recent study of the economic opportunity for
irrigation projects in the U. S.,' concluded that an average economic.
incentive (increased yieza) for irrigating an acre of lard was over
$400 per acre in the Southwest and even higher in some parts of the eastern
United States. Deductirg the cost of preparing the land, etc., this
would correspond to water values greater than $50 per acre foot.
At the other end of the value range, the basic food grains corn and
wheat are already grown extensively in the West on irrigated land with
water costing (incrementally) about $10-20 per acre foot. These crops
are usually part of a multi-crop sequence, and perhaps the grain does not
bear its full share of water rights cost.
The value of water roted above is (in the West) based on Colorado
River water, wnose high salinity requires extensive flushing and other
waste. We have noted above that farming with distilled water could be
accomplished with much less water per unit of food output, so the economic
value of desalted water sould be corrected to allow for this increased
efficiency, Although the water use efficiency experiments would indicate
- 13 -
the value could be more than doubled, I have added only 50% to the value
when used on grain crops, and much less when used on high value crops.
'
Thus the range of economic value for distilled water might extend from
:
$65 per acre foot downward for high value crops, and from $30 per acre
foot and down for grains.
Provided that low cost land is available, then it would seem reason-
able to expect that some use of water for agriculture would begin at .
$65 per acre foot and substantial quantities would find a market at any
price below $145. The production would be primarily high value crops :
(wnich constitute about half the dollar value of all crops in the U. S.).
At $30 per acre foot or below, the market would be very large, would
include basic food grains, and desalinated water could be considered a
strong possibility for assisting in the world food crisis. This is a
conservative assumption, since it is based on the present price of 2¢
per pound for grain. The relative value of food would, of course, be
expected to rise in times of worldwide famine. A one cent rise in price
would increase the value of water used in its production by about $30 :
per acre foot.
..
.
...
:
.
..
Water at $65 per acre foot seems to be easily within the reach of
.
present technology, since the projected cost of water for the MWD project
.....
is nearly that low. But for $45 and $30 costs, some improvement in
.
technology will be necessary. Let us now see what degrees of improvement :
.
.
.
are thus implied.
.
. .
.
.
1
.
.
. .
.
.
.
-
..
.
—
- 14 -
5. Components of the cost of water.
The cost of water as received by the farmer includes several components
Whic. we must identify and subtract in order to choose the types of
energy source which may be suitable. The se components include delivery
cost, capital cost of the evaporator pla », operation and maintenance of
the water plant, and heat cost. The only size plant which is considered
in the following analysis is one billion gallons per day. This choice
was made for two reasons: It is the largest size for which extensive
design and cost studies have been made, and it is small enough so that
.
all its water output can be consumed on farms within 20 miles of the
plant, thus keeping delivery costs low.
5.1 cost of Distribution.
At 90% load factor, the annual output of a 1-Bgd plant is one
million acre feet of water, which would provide 4 feet of water to an
area of 250,000 acres. Let us assume that the water is to be distributed
to such an area lying within a 400,000 acre semi-circle surrounding the
plant; the rest of the land is available for other purposes. The cost
of distribution facilities would be about $45 million dollars, made up
as follows:
1.8
1.4
10.0
Main Canals
Bridges (2/mi)
Pumping Stations
Transmission Lines :
Turnouts, Gates, etc.
Lateral Canals
at $120/acre)
0.9
0.4
30.0
44.5
- 15 -
This estimate was made using information furnished by the Bureau of
:
Reclamation for lined, open ditches, and appropriate other facilities.
For dead losses of about 50 feet and a capital charge rate of 4% the
total annual costs for distribution would be about $2 million, or $2 per
acre foot oi water. For our range of costs to the farmer of $30-$45
per acre foot, then, we have an equivalent cost at the plant of $28-
$43 per acre foot.
5.2 Cost of Evaporator.
In spite of the fact that no one has yet constructed a very large sea-
water evaporator, the costs of constructing such a plant can be estimated
with reasonable accuracy provided the fundamental process parameters are
well known and these are preserved in the scaled-up plant. At Oak Ridge
we have just completed for the Office of Saline Water a study in depth of
flash type evaporators in sizes ranging from 150 to 1000 Mgr. For this
study we utilized proven process characteristics, but introduced improve-
ments in plant arrangement, method of construction, and auxiliary systems
--
-
-
--
which we found were suited to the large scale of the installation. The
experience of the ORGDP staff in engineering of very large plants contributed
substantially to the soundness and ingenuity of the design. The cost esti-
mates in this study are very detailed and are believed to be easily realiz-
able in the field by the time that anyone could undertake to construct a
1000 Mgd plant. Table _ lists the construction and operating costs of
such a station for one case studied, where the evaporator was coupled to
a 350.) VWt HWOCR to form a dual-purpose plant of 250-Mgd capacity.
- ló -
5.2 (continued)
In order to illustrate the relationship between the cost of water and
the cost of the heat supplied to tre evaporator, we must develop the cost of:
the evaporator system at various performance ratios, since this parameter.
of the evaporator is always adjusted to make the most economical choice for
the cost of heat. As part of the Atomic Energy Commission program at Oak
Ridge we are studying intensively certain aspects of this coupling economics.
A computer code has been developed which constructs an accurate model of the
OSW conceptual design and which can optimize the plant for any given condi-
tions, making changes in 58 different parameters as it does so. The code
has been equipped with a cost storage library using the detailed informa- .
tion obtained in the osw design study.
For the purposes of this article I could have requested the code to
print out a curve showing the cost of water versus heat cost, but this
would probably be acceptable only to those readers who were thoroughly
Tamiliar with the Oak Ridge code and the assumptions used in the calcula-
tion. Instead, I would like to start only with information about the cost
of certain components of the plant and develop the cost of water:cost of
heat curve in a visible fashion,
5.2.1 Cost of Components vs. R.
Figures_ through_ show how the cost of eight major components
or systems in the plant varied as the design was optimized in turn for per-
formance ratios of 7 through 12, for a plant of 1000 Gpd capacity. 'Sepa-
rate cases were run for different maximum brine temperatures, but today I
shall refer only to the 250°F cases. In Table I have listed each systein
- 17 -
and its construction cost when R = 10. The cost unit used is cents per
..........--------
daily gallon of water output capacity and includes 22% indirect costs
such as engineering, interest during construction, and contingency. The
eight major systems accounted for nearly all the cost of the plant; the:
remainder were collected into a miscellenous item.
-
.
..
It was found to be quite easy to fit the curves in Figures _ through
with simple analytic expression in R which gave an excellent match
between R = 7 and R = 12. These expressions are listed in the third
column of Table _ The sum of these expressions, with only a minor
rounding, gives the expression at the bottom, which gives the cost of the.
whole plant with good accuracy.
..
..
..
..
5.2.2 Advanced Plants,
.
Although the OSW's program for development of advanced evaporators
is just getting under way, it is already evident that some remarkable improve -
ments in the performance of heat exchangers and in the prevention of chemi-
cal scale may be in the offing. So that we do not imply that the entire
burden for improvements in water cost must come from reactor improvements,
we must take some account of these advanced flash evaporators. In the
fourth column of Figure _ I have tried to estimate the way each 'major
component would be affected if improved heat transfer tubing of the types
already being tested in our loops at Oak Ridge were successful and if
scale control means, such as carbin dioxide injection, could be worked out
.....
.
..
.....
.
to eliminate the addition of sulfuric acid. Naturally, there is no assurance
...
...
.
that the improvements will all be successful or that they will have the
.
-- -- ..
economic effect.Which I have ussumed in column 4.
: --, -...
-
-
-
-
--
=
-
-
- 18 -
Figure _ shows a plot of the total cost expressions from Table. -
The plot extends from R = 3 to R = 15, although we must remember that the
information used extended only between 7 and 12. (The extension to
higher R is quite probably valia). Over the range which we wish to use,
one can readily see that the curve is, in fact, straight enough to permit
the three-term expression to be replaced by a linear equation without loss
of accuracy.
5.2.3 Calculation of Water Cost.
The ground rules used for the water cost calculation are as follows:
1) Load factor 0.9.
2) Fixed charge rate on capital (interest, amortization, and insurance) =
;
5.6%.
3) Operating labor for a 2000 Mga plant will be 0.27€ per 1000 gal.
($888,000 per year) for a current plant and 0.25€ for a more auto-
mated one.
4) Sulfur, if used, costs 1.3¢ per 1000 gal. of product. (The cost of
the plant includes an on-site acià plant).
5) Pumping power will cost 1.3¢ per 1000 gallon of product for a cir-
rent plant, 0.70 for an advanced plant, The decrease is primarily
in the expected cost of power, although the amount used may go
down also.
6) Ada miscellanous costs of 0.134 and 0.054, respectively, to round
the sum of the operating costs to 34 and 1¢/1000 gal., respectively.
- 19 -
The fixed charges and maintenance charges can be easily converted to
¢/1000 gallons of product by multiplying the construction cost in ¢ per.
daily gallon by 0.2, since i Gpd is .329 kilogallon per year, and
.066/-320 = .20. The cost of heat in ¢ per million Btu can be converted :
to ¢/1000 gallons by multiplying by 8.3/R, since it requires 8.3 MBtu to.
distill 1000 gallons, and R is the number of times the heat is reused..
The cost of water, then, can be calculated for any value of heat by.
the following expressions:
Evaporator
Current Designs
: Advanced
14 + R + 20/R
15 + 2R + 20/R
Capital Cost («/daily
gallon)
20 + 1.TR
Equivalent Expression
Water Cost (4/1000 gal.)
3+.2(20 + 1.7R) +
8.3 H/R
4,94 /H.
17.5 + .85R
1 +:2 (17.5 + .85R) +
8.3 H/R
7NH
Optimum R
Minimum Water Cost
(¢/1000 gallon)
7, + 3.36 /H .
4.5 + 2.38 N
(R is eliminated by substituting the optimum R in the water cost equation,
which makes the second and third terms equal.)
Figure_shows a plot of the two curves in cents per 1000 gallons
· and in $ per acre foot versus the cost of the heat supplied to the evapora-
tor (at about 260°F). The region between these curves covers a range of
water costs which encompasses the agricultural market; the range of evapora-
tor technology extends, as noted above, from essentially current (except
for size) to hoped for future advances. The range of heat shown covers an
equally wide spread of technological progress. The reminder should be
made that these curves apply only to 1000 Mgd dual-purpose plants. Smaller
plants would produce more costly water, larger ones less costly water, at
the same technological level.
..
......
...
-
ORNL-DWG 66-2442
COST OF. PRIME HEAT (4/406 Btu)
. 5
0 R 15 20

CURRENT EVAPORATOR DESIGNS
_HIGH VALUE
CROPS.
ADVANCED PLANTS
COST OF WATER (6/1000 gailons)
MAJOR
FOOD GRAINS_
COST OF WATER ($/acre-ft)
_
-
--
-
-
--
.
.
LILI_1_
:
.
-10.
2 : 4 6
8
. COST OF HEAT TO EVAPORATOR (C/106 Btu)
ORNL-0146 66-2443
ㅜㅜㅜㅜ
​40
CURRENT DESIGNS
.....-
-...
15+2R+20%
ADVANCED FLASH PLANTS
20+1.7R
------------
14+R+2%
.
TRT
.
...
:
1000 Mgd WATER PLANT COST (cents per daily gallon)
17.5-0.85R
ADVANCED VTE
10:10.7R+ 20%R.
Succm
*.
comiciliari in
*.
14+0.5R
tenzite
ALDIS
0...:
ILI
4
6
R, PERFORMANCE RATIO
8
10
12
.
40
CURRENT DESIGNS
-
15+2R 1. 20/R.
ADVANCED FLASIL PLANTS
--
+1.7R_.--
144-17.4.20/12
1000 Miga WATER PLANT COST (cern, wer daily callon)
20 |
17.5.1-0.85R
201...00
L
__II
. 2 .
.4.
LILI
8
10
R, PREFORMANCE RATIO
12

- 20 -
5.3 Relation or Exhaust Steam Cost to Prime Steam Cost.
Ide zeat supplied to the evaporator in a dual-purpose plant has a lower
value than the prime steam. To convert the exhaust steam costs along the
cottom of Figure _ into the equivalent values for the prime steam requires
in effect an allocation of prime steam cost to water and power. Our basis .
for this will be one which does not convey any subsidy to water from the
sale of power, since we wish to determine whether desalted water for agri-
culture can pay the full costs of its production.
The method of allocation used has been fully described elsewhere ?.
It is based on allocating the steam costs according to the amount of avail-
able energy (sometimes called exerky) which each product consumes. The
available energy is proportional to the amount of electric power which the
.
!
steam could nave produced in a full concensing turbine. Since we wish to
consider only cases where the back-pressure turbine exhausts at 260°F, for
any initial prime steam condition and cost there will be a definite ratio
between ire prime steam cost and the 260° exhaust steam value, according
Q
to e relation:
H/S= a1 = By,
where a and 8 are the efficiencies of the condensing and back-pressure steam
cycles, respectively. (A small correction for condenser credit is neglected
here.)
When such a calculation is made for various energy sources, the 255 °F
exhaust steam is found to have a value .3 to .5 of the prime steam cost..
For the most common nuclear systems the fraction is close to .4, which will
.
-
- 21 -
do Por our préser.i discussion.. rlons the top om Figure_ I have sro:n
the prime steam cost waich corresponds to the exhaust steam value with
this assumption. The allocation in any actual plant ray differ substantially
from the ratio I have used.
5.4
Prime Steam Cost Required to Reach fgricultural Water Goals.
If the opportunity for desalted water in agriculture begins as we have
assumed at a water cost of $43 per acre l'oot at the plant, Figure _
shows that current evi. porator technolozy will require a prime energy cost
oí less than 10¢ per vBtu. With the advanced evaporator, however, the mar-
.
ket is reached and well entered, even with steam costs of about 25€ per
MBtu, which is attainable with commercially available reactors under munici-
pal. financing.
For a major influence on the agricultural water market, we have
assumed above that $30/ft. must be reached, or $28 at the plant. This cost
appears attainable with the advanced flash plant at an energy cost of about
8¢ per MBtu.
In summary, then, iſ one is optimistic about advances in the evapora-
tor art, artificial agricultural water is definitely in the picture, regard-
less of any major improvements in the cost of energy. If, at the same time,
one could see a way to expect energy costs below 8¢ per MBtu, desaiination
would have a major impact on the market for water and for nuclear reactors.
If one is skeptical about evaporator improvements, then a 10¢ energy source
is necessary, even for "openers" in the game. The difference between $45
- 22 -
ara $30 water would not be an important factor in its acceptability for
..
municipal use, but in agriculture the difference is crucial. To produce
-
-
-
.
this much improvement in the cost we must reduce the cost of prime energy
-
to less than one-third of its present cost.
- --
-
-
-
-
-
- -
-

LI
NLY
WIB
..
i
END
;
=
5
.
.
Ver
061
DATE FILMED
12/ 8 / 66





ma
:
-
Ei
Ay
MINI
MANY
1
0
.
11.
ww
403
w
www
AN
W
with wel een
dwi
'.
2
:
i
.
.'
...
W