perm filename NUCLE1[L,VDS] blob sn#255255 filedate 1976-12-08 generic text, type T, neo UTF8

	          	        Thermal Pollution

	Americans use an incredible amount of energy each year.  In fact,
with only about 6% of the total world's population, the U.S. uses 35% of 
the world's energy.  In l970, the U.S. consumption of total energy per capita
was about 250 KWh per day, and of that, the electrical consumption per day was
about 21 KWh per person.  Last year, in l975, the FEA's estimate of the year's
electrical production alone was 1.9 x l0  KWh per year.  (That is l.9 TRILLION

KWh per year!)  And, more importantly, the present doubling time of electrical
generation in the U.S. is l0 years, its present growth rate is 2%, which itself
is accelerating.  If Americans continue their present energy utilization trends,
they can expect an astronomical amount of over three and a half trillion KWH of

electricity needed in the year l985!

	Unfortunately, as America's electrical energy consumption steadily soars,
the amount of fossil fuel resources steadily declines.  Now, as the fossil fuel 
resources continue to become more and more scarce, the price correspondingly becomes
more and more expensive.  (The beginnings of which were demonstrated in the "energy
crisis" of l973.)  Americans are now being forced to seriously seek other energy
alternatives which can competitively compete with the rising fossil fuel costs.
And, the people must find another means for supplying these enormous amounts of 
energy within the next two decades if they are planning to keep up their present
patterns of energy consumption.  Although coal, solar, geothermal, and hydro power
are being considered as major contributors to the future energy needs, it looks as
if nuclear power will, by necessity, become the dominant source of electricity 

generation before the year 2000. 

	In l975, nuclear power supplied only 11% of the total electrical energy
needs, but the FEA predicts a 27% share in l985, while the Exxon Company forecasts
a possible 50% share in l980.  Even though nuclear power is presently being hotly 

debated by a substantial number of concerned Americans, the fact remains that 
there are 58 nuclear power plants on line today, with a projected number of 170 in
the year l985.  With energy utilization rates increasing now, we can expect that
nuclear power use will most likely increase greatly within the next decade.  This 
new power source will bring along with it not only the problems such as those  

involved with waste disposal, fuel processing, and plant safety, but also the 
possible problems arising from thermal pollution.  
	Thermal pollution is caused when the heat that is wasted in industrial 
processes is transferred to a body of cooling water, raising its temperature 10  to
20 C., and then dumped back into the waterways.  This temperature rise can cause
a great deal of harm to the water ecology and its dependent life, thus making this
a potentially serious pollution problem.
	It must be stressed that thermal pollution is not a new problem which has 
been caused only by nuclear power plants. ALL power plants reject this unusable heat,
which is known as waste heat, whether they are coal, oil, nuclear, solar, or any 
type of heat source.  The reason for this is summed up in the second law of thermo-
dynamics which says that all processes cannot be l00% efficient.  There is simply a
thermodynamical limit on the conversion of random heat energy to organized energy
(work). This is a limit imposed upon us from nature, and cannot be argued with.

The reason that people are becoming very concerned about it now though, is because a

nuclear power plant gives off about l5% more waste heat than a fossil fuel plant, 

which gives off some of its heat directly into the atmosphere through the stacks.
	The efficiency of a power plant can easily be calculated by employing the     
Carnot equation, since the majority of plants today operate by using the steam cycle.
In this cycle, pressurized hot steam drives a turbine, which turns fuel energy into
mechanical energy in the turbine.  This energy is converted into electrical energy, 

in the form of electricity, and is then distributed to the consumers.  The Carnot 

equation allows us to calculate the actual amounts of waste heat which is produced 
in this cyclic process.  Pictured on the next page is a typical plower plant using 
the Rankine Cycle (a steam cycle.)  1→2 is the conversion of thermal energy to 
mechanical energy.  2→3 is the heat rejection due to condensing.  3→4 is the only 
work input into the cycle, the work needed to run the water pump.  Finally, 4→1 is 
the heat input provided by the boiler.

	The maximum efficiency of the power plant's heat engine is determined              
by the Carnot efficiency, which is simply: MAXIMUM EFFICIENCY = 1-(T(2)/T(1)).
By looking at this equation, we can see that we want a very high entering temper-
ature (T(1)), and a very low exit temperature (T(2)), in order to obtain a high 
engine (cycle) efficiency.  Thus, the efficiencies depend on the temperature and 
pressure of the steam generated, which is limited by the temperature capacity of the
metal which must enclose this heat, and also, by the temperature of the environmental
cooling water.                                                   
	Let us look at some typical power plant efficiencies.  A modern fossil fuel
plant has a thermal efficiency of 40%, if it uses a steam cycle with superheat.  
This is quite a high temperature; most plants have efficiencies around 35%.  The
efficiencies of nuclear plants are varied, it depends on the type of reactor.  A 
Light Water Reactor (LWR), with a T(1) pf 277 C and a T(2) of l7 C, has an efficiency

33%.  A High Temperature Reactor, (HTR) is 40% efficient, because T(1) can be 
increased to 530 C.  Generally speaking, nuclear power plants using the steam cycle
have low efficiencies and reject low-grade heat (usually about 30 C), while gas                    
turbines can produce high quality heat with efficiencies on the order of 40%.  High
grade heat can be obtained from the steam engine, by extracting some of the higher     
temperature steam from the turbine, but only at the expense of reducing electricity   
production.  High grade heat can be much more easily used than the low-grade heat,
as other none-electrical applications of this heat need higher temps.  Now, the major      
emphasis by the power stations is on producing maximum ELECTRICAL efficiency.  Should
this emphasis be shifted towards an emphasis on maximum ENERGY efficiency ?  (That is,
obtaining some of the high grade heat from the steam engine in order to effectively use
it.  Would the benefits derived from the possible uses of the high grade waste heat 
outweigh the disadvantage of decreasing the electrical capacity?  I think so, and
have included at the end of this paper some uses of waste heat which I think can become
greatly beneficial.  ENERGY efficiencies of 80% have been agreed upon to be possible     
if this waste heat is used effectively.      
	Present research in areas such as fluid mechanics, combustion, heat transfer      
and lubrication is striving to improve the Carnot efficiencies.  Research is still

being devoted towards finding the "miracle metal" which will be able to extend

the present metallurgical limit of 1100  F. in the modern steam cycle power plants.

Some research is now directed towards finding alternatives to the low efficient  
Rankine cycle.  Those being explored are magnetohydrodynamics (MHD) and fuel cells.
No major breakthroughs on them have been discovered as of now to make the replacement. 
 	With an efficiency of 33%, a 3,000 MW LWR would dump 2,000 MW of heat into 
the environment.  With hundreds of nuclear power plants each dumping out amounts 
such as these, we can see where the temperature of the receiving water could become
quite high if the waste heat was continually dumped into the rivers, lakes, and  
estuaries.  This is where the problem of thermal pollution comes in.       
	By a rough estimate, it is assumed that 1 GW of electrical capacity causes
a body of water to be raised 10 C, (Assuming an efficiency of 33%), and requires 50
cubic meters per second of cooling water.  The Environmental Protection Agency (EPA)
has limited the maximum temperature increase in receiving waters to be 5 C.  Thus, 
we can see that l GW will require 100 cubic meters per second of cooling water to
meet these limits! These huge water withdrawals can cause water shortages in areas
where water supplies are already deficient.
	The U.S. has a run-off of 53,000 cubic meters per second, making a limit
of only 530 GW of power then to be obtained from the nuclear power plants.  With
our high energy consumption rates, this figure should be reached by around l980.
Therefore, it is obvious that this heat will have to be dissipated elsewhere 
besides in the runoff water.  This is why I feel that immediate emphasis should  

be placed on obtaining the high-grade heat and effectively using it, instead of
just throwing it away into the rivers.  
	But, WHAT IF the waste heat is continued to be dumped into the rivers?
What are the effects of adding this heat to the water ecosystem and life?
 	Probably the most important effect in raising the water temperature of
river water is the decrease of oxygen solubility; the oxygen capacity of the 
water is reduced, which always spells out trouble.  Thus, the river re-aeration 

rate is decreased, due to the reduced oxygen saturation deficit.  Along with all
of this is, of course, an  increase in Biological Oxygen Demand.  This is why dumping
sewage into warm water can be very serious--the wastes are oxidized at a much  

faster rate, which requires a very high BOD.  If there is not enough oxygen in the
water, the decomposition of the wastes will be anaerobic, which is undesirable 
because it leads to such end products as methane, ammonia, hydrogen sulfide, and 
CO .  Thus, there is a lower waste assimilation capacity.
	Other effects of the temperature rise include increase in evaporation 
rates (which causes increased consumption rates of water), a reduction in ice
formation in winter, and an increase in chemical reactions.  The viscosity of the
water can also be decreased, which can result in increased sedimentation, leading to
possible sludge problems.  And, of course, raising the temperature also leads to a 
qualitative  and quantitative change in the aquatic population, and an increase in 
the undesirable aquatic flora.
	When we look at the effects of thermal pollution, we must be sure to 
not just look at the direct effects that it has on the fish, which has been done so
often in the past.  We must remember that the surface waters which can be penetrated
by sunlight and that can receive nutrients can support an active ecosystem, so the 
added heat will effect the decomposers and producers, as well as the consumers.  Because
all three groups are so tightly interdependent upon eachother for survival, it is of
utmost importance to weigh  the effects on every living creature in the ecosystem--
the zooplankton, the phytoplankton, the microorganisms, the fish, and all the rest.
This over-all view, which deals with communities and the interrelationships of popu-
lations within them, and determines the over-all effect of any given factor on all the
species, is known as synecology.
	Each species has its own tolerance range for temperature; one that has a wide
range is called Eurythermal,whereas those with a narrow range is called Stenothermal.
Some organisms can live in near freezing water, whereas some can survive at temperatures
at 88 C.(some bacteria).  Thus, we can see that by raising the temp. of water 10 C.,
some may not be affected at all, others might be beneficially affected, and others
just might be completely wiped out. Physiologically, the  upper lethal temperature
is determined by the degree of enzyme inactivation in a particular species.  With 
increased temperatures, respiration is increased, which means an increased rate of 
chemical reactions within the body.  These reactions must be catalyzed by temp.-dependent
enzymes.  Above an optimum temp., these enzymes become inactivated and can't keep up 
with the reactions.  With higher temps., and more and more inactivation of the enzymes,
the organism eventually dies.  Inefficient oxygen transport to cells, central nervous
system malfunctioning, or changes in the lipid structure of cell membranes might be
other reasons for deaths caused at elevated temperatures.
 	Autecology is the ecology of individual species, involving studies of factors
influencing their distribution in nature.  Because fish are economically important,
let us look at some actual effects of thermal pollution upon them. Because temperature 
is probably the single most important factor governing life, the possible consequences
of thermal pollution are very serious.  Fish are very sensitive to temperature changes
in their waters, and they are unable to quickly regulate their body temperature.
	An 18 F. increase causes the basic metabolic rate of fish to double, which
is in accordance with the Van't Hoff Principle, which states that the rate of chemical
reactions increase with increased temperature.  This principle is very important, because
this increase of metabolic rate includes the increased rate of respiration, which of  

course increases the need for oxygen.  At the same time, an increase in water temp.
directly correlates with a decrease in the amount of DO in the water because of a 
decrease of oxygen solubility, a decrease in the river re-aeration rate, and an 
increase in the Biological Oxygen Demand (BOD).  All of this spells disaster for the
fish.  And, to make matters even worse, the respiration difficulties are coupled with
the problem of the reduced hemoglobin affinity for oxygen, which means that there will
be a reduced efficiency of carrying oxygen to the tissues.  These two effects alone
put the fish under severe stress.  
	Another serious problem occurs in he reproduction cycle of the fish.  Usually,
fish spawn in the Fall or Spring.  The temperature of the waters induce the seasonal
development of the gonads.  At the critical temperature, the female deposits her eggs.
For instance, estuarine shellfish such as oysters and clams spawn within hours of the
critical temperature.  With the temp. being increased artificially through the waste
heat, the hatching time of fish are greatly effected.  Atlantic Salmon have a normal
hatch time of 114 days at 36 F., but only a 90 day period at 45 F.  This then prevents
normal development of the eggs.  The tiny crustacean, Gammarus, reacts to this in a  
strange temperatures greater than 46 F., the species lays only female offspring! 
D'Arcy W. Thompson has also established the fact that accelerated stage development
by warmth shortens the duration of the life.  Thus, the longevity of the fish are 
threatened by the increased temperature. 
	Fish are fortunately able to acclimate to temperature shifts, providing that
they are not too sudden.  An example of this is shown by the reaction by the largemouth
bass.  When they are transferred suddenly to 85 F. temperature, from 65 to 70  F. 
temperatures, 90% of their eggs will perish.  However, if one gives them enough time
to adjust to the change, in this case, 40 hours, only 20% will die.  Fish, as a general
rule, acclimate to elevated temperatures much more quickly than they acclimate to 
decreased temperatures.  
	Again, though, it is important to emphasize that the fish are only a part of
a very delicately balanced ecosystem.  The food chains in the oceans consist of long
food chains, as opposed to relatively short one on land.  Man must be very careful to
avoid  destroying any link of this tightly woven, interdependent food chain.  Ecosystem
stability is weakened by an increased water temperature environment, because the warmer
water usually causes a decline in species diversity.  
	We have seen then that thermal pollution can cause serious effects to the water
ecosystem if action is not done.  The good thing now is that most of the nuclear power
plants have not yet been built, and so plans can be made to incorporate methods into 
the plants for properly disposing of this waste heat and controlling thermal pollution
from the very start.  For instance, proper siting of the plant can reduce the harmful
impact of the heat.  Many factors must be considered, such as the atmosphere.  How 
much wind, rain, humidity is there?  What is the average temperature?  The receiving
water must also be evaluated...what are the flow characteristics, the turbulence, the
stratification, and the volume?  One must look at the biological factors...what types of
aquatic flora and fauna is there?  What are the ecosystems?  What is the DO and the 
BOD levels?  How much waste and pollution is already present in the water?  And finally,
one must ask what the other uses of the receiving water are...recreation, irrigation,
water  supplies?   Everything  must be taken into account and carefully evaluated.
	By using cooling towers or cooling ponds, the problem of thermal pollution     
may have been taken care of (depending upon the validity of assumptions that thermal
air pollution will not cause detrimental effects to the environment).  However, it is
obvious that this energy in the form of waste heat is simply being wasted.  With energy
costs and possible future environmental problems, serious attempts should be made to
effectively utilize this heat energy.  
	Realizing the importance of utilizing as much of this waste heat as we can,    
research is advancing rapidly in this field.  Provisions must be made now for waste   
heat use in the original designs of the nuclear reactors.  The two main considerations 
that must be taken into account when developing uses for the heat is reducing enivron-
mental effects and in creating an overall economic gain.  The most important difficulty
which limits the development of the heat uses is the economic factor.  Much progress 
has been made in developing uses for the waste heat in areas such as aquaculture, mari-
culture, agriculture, airport deicing, space heating, airconditioning, and uses in 

many industrial processes.  However, much more research is needed to actually turn these
experimental programs into working realities.
	One promising use of the waste heat could be in using it for heating the  
sewage in a secondary sewage treatment plant, which uses the activated sludge process.
This process involves running the sewage effluent into an aeration tank, where the 
bacteria feed upon the organic matter and converts it into the end products of H O,
CO , sulfates, nitrates, and new bacterial cells.  This process can be greatly acceler-
ated by increasing the temperature,  because a 10 C. rise can double the biochemical
reaction rate. The removal of suspended solids at normal temperature of 10 C. is between

35 and 65%.  With each 5 C. rise in temperature, there  is an increase of 20% removal

of suspended solids.  BOD is yet another very important factor in determining water
purity; at 2.5 C. above normal sewage temperature, the upper limit of removal efficiency

of BOD (40%) is obtained.  With each additional 10 C. rise, the removal of BOD can be

increased by 15% over that 40% level.  Also, the decreased water viscosity can cause a

a faster sedimentaion of the activated sludge particles.  An estimate is that if the

sewage temp. could be raised from 70 to 100 F., by passing the sewage effluent through

the power plant condenser, the sewage could be treated at twice the normal rate of a   
70 F. facility.  This means that the sewage plant will be able to save money by having
less capital investment costs, (they would only need half as much equipment because they
could send the sewage through the plant at twice the normal rate), while the power 

plant could save money by having less capital investments and operating expenses in

large cooling towers.          

	Not only can the waste heat be effectively used in doubling the speed of the

activated sludge process, but it can also be used in another aspect of waste water

treatment--for reducing the amount of total dissolved solids (TDS) in the water.  

Usually, a city adds about 250 to 300 ppm of TDS to the water as it is used by the

consumers.  Each city is responsible for making sure that the water that it discharges

back into the stream does not have a level of over 500 ppm.  Over three million people

today are served with water having a concentration exceeding 1000 ppm--those unlucky

people whose city happens  to be at the end of the river.  Water entering Mexico after

having passed through the western states of America have levels far exceeding 500 ppm,

which is causing a considerable amount of international hostility.  Thus, it is important

to find a way to economically lower these levels to a value below 500 ppm.  In the past,

this has been difficult to do because most of the methods for desalting have required

large amounts of energy, which have been too costly to obtain. Irving Spiewak now

believes that with the potentially cheap waste heat energy, the process can be comple-

tely done  at a fraction of the former cost.  The method that he has chosen to desalt

the water is that of evaporation, using a vertical tube evaporator.  By evaporating

34.5 million gallons/day (mgd) with 400 MW heat and blending the distillate with 65.5

mgd of filtered, carbon-treated, secondary effluent and 50 mgd from the treated water

supply, the full 150 mgd supply for a city of one million could be provided at 20 to 

22 cents/l,000 gallons.  This seems to be a very low cost estimate which would be

impossible to realize in 1976, but in any event, it must be stressed that this evaporat-

ing technique probably can be carried out within a reasonable cost range.  This appears

to be an excellent way to utilize this waste heat, and the power plant could again

benefit by having a smaller load on the cooling towers.

	It would be highly desirable to locate the waste plant close to the nuclear
power plant, or vice versa, so that the two could take advantage of each other's 
contributions and requirements. This is known as the group utility concept.  This  
could easily be done by combining a power generation plant with a seawater  desalting
plant, or perhaps a  huge greenhouse or animal shelter complex.  Grouping them together
is important because of the costs that would be involved in otherwise transporting the
heat through a system of pipes to the desired place. For instance, if a 10 MGD treatment

plant was situated one mile from the power plant, it would cost from 1.5 to 3.9 cents
per 1,000 gallons.  (Depending if the sewage plant is located downhill from the power
plant, which would not require the high pumping costs.)  Located five miles away, the
cost would be higher; from 2.9 to 5.4 cents per 1,000 gallons.  Thus, we can see that    
locating the two together is very important in the economic analysis.

	A market for the waste heat just might be in the area of agriculture.  

Presently, information is limited on many aspects concerning this topic, but there 

are many experiments now in progress which will produce more concrete evidence so 

that this use of waste heat just might become a very real possibility.  For instance,

one such experiment is one which is trying to determine what the effects are of irri-

gation water temperature on crop production.  Although we do not know exactly what

these effects are, we do know that crops do  grow best under specific environmental

conditions--which is of course why greenhouses are used for certain crops.  The specific

temperature may vary from species to species and at different growth stages, but unfor-

tunately, nature does not always provide them.  By using the waste heat to warm up the

soil, perhaps these temperatures  could be obtained and could lead to a much better 

crop production.

	The waste heat can be used for open-field agricultural uses, or for green-

house uses, both which can be economically sound.  Some of the potential benefits of

temperature control to open-field agriculture are prevention of damage caused by 

temperature extremes, extension of the growing season, promotion of growth, improvement

of crop quality, and control of some diseases and pests.  A 1000 MWe nuclear plant

rejects enough heat to irrigate 1,000 acres. In Oregon, an experiment was conducted

to determine if the 95 F waste water which was sprayed over 170 acres of fruitland

and farmland could prevent frost on the orchard crops and extend the growing season 

for the other crops.  The results showed that the spraying could protect the fruit

for temperatures down to 27 F.  Because of this, the farmers were able to get their

fruits into the market ten days earlier, and so received a 25% greater profit.  

	The temperature of the soil is one of the most important factors governing

the germination, emergence, and early growth of plants.  With optimal temperatures

of the soil at this critical time, the crop could have a much greater yield and crop

quality.  Some results of experiments point this out; by increasing root temperatures

from 18 to 30 C., rice yields were increased from 32 to 55%.  Corn yields increased

by 68% when the soil temperature was increased from 12 to 27 C.  Thus, soil warming

and irrigation just might offer a good potential for the use of waste heat from 

power plants.  The overall economics have not been established as of now though.

Also, testing must be done to see if any problems in plant disease and pest control
might arise because of the added heat.  Finally, the question of radioactive contam-

ination would have to be settled.  

	The utilization of waste heat for greenhouse operation has long been suggested.

In many areas, heating costs run from about 10 to 30% of the operating cost, a cost

of $2,000 to $11,000 per acre.  If the waste heat could be obtained at a much lower

cost, these large energy costs could be substantially reduced.  Most crops do best at

soil temperatures around 75 F, and if the waste heat could be pumped through piping

systems buried under the greenhouse's soil, the crops could grow much better.  Another

good thing about greenhouse utilization is that temperatures below 100 F are sufficient

for greenhouse heating; therefore, the efficiency of the power plant would not be

reduced.  A 1000 MWe plant could heat up about 300 to 500 acres of greenhouses, so

possible lack of heat would not be a problem.  Beall has studied the city of Denver

and has suggested that greenhouse heating for the production of the city's supply of

tomatoes, peppers, cucumbers and lettuce would be profitable.  He suggests that the

cooling tower be completely replaced by special greenhouses, which could be cooled to

75 F. in the summer and could be kept at temperatures over 65 F. in the winter.  Beall

argues that if present production of vegetables in greenhouses is profitable using  

gas or oil fired heaters at $1.00 or $1.50 per million BTUs, then the reactor heat

which could be obtained at 20 cents for the same amount (for piping and pumping costs

if the greenhouse complex is located on the reactor exclusion area) would produce an

additional profit of $4000 to $6000 per acre.  Idealized growth curves for lettuce,

tomatoes, and cucumbers are drawn below.  If these optimal temperatures could be

maintained, and if the waste heat could be obtained at such a low price (the heat 

itself at almost no cost), perhaps the figures that Beall presents might be reasonable.

	Space heating and airconditioning remain one of the most promising applications
for the use of the waste heat.  Already, there are systems operating today which uses
the heat from various sources--mostly from fossil fuel plants.  Iceland has used geo-
thermal steam for forty years now to heat the hot water used in space heating.  The
city of Reykjavik has a population of 80,000, and its residences are now heated with

hot water which is transported 10 miles.  They report a savings of 40% when they 

compare their system with a similar heating system with oil fuel.  There is only one

district heating system which is associated with a nuclear reactor--one in Agesta,
Sweden, which is a 65-MWe HWR.  It has 55 MW of heat in the form of hot water piped
2.5 miles to the suburb of Farsta.
	The heat could also be used in the summer to provide space cooling.  An
ammonia-water system is usable with an air-cooled condenser and absorber that requires
a 250 F. heat supply.  A lithium-bromide system could also work; it requires 220 F.
heat and is about 50% more efficient.  A three-bedroom house would need about 75,000
BTUs in the winter and 72,000 BTUs in the summer.  It is estimated that a 1000 MWe
reactor could provide a population of about 450,000 with electricity, space heating

and air conditioning.
	Beall has studied the situation involving space heating and air conditioning
with heat from two 500-MWe reactors which could produce heat at 300 F.  He has added
oil-fired boilers which is capable of 1500 MWt heat for standby units.  With heat at
a cost of 30 cents per million BTU and delivery costs of 20 cents per million BTU (for
ten miles of piping),he feels that the system could be very economical.  (His estimate

is that the price could be $1.50 and still be competitive with fossil-fuel heat).
	Of course, there are many problems which must be solved before programs can
be started for using this waste heat.  A major problem is the unreliability of the 
nuclear reactor.  A nuclear reactor can shutdown unpredictably, for various reasons,
such as for maintenance or malfunctions.  This can cause real problems for those people

people who are utilizing the waste heat for fish farms, as fish cannot take sudden drops

in temperature.  In January of 1972, after a shutdown of the Oyster Creek Station, 

about one to two hundred thousand Atlantic Menhaden fish were killed during the period

when the temperature of the discharge water from the condenser dropped from 22 to 15 C.

(These were not fish in a fish farm, but still the results would hold true for a fish 

farm.)  Thus, we can see that in many uses of the waste heat, back up structures bought
by the consumer would  be  necessary.   Would the added extra cost of buying another     
structure for the utilization of the waste heat be worth it economically?  For example,

if a consumer is using the waste heat for space heating, and he had to pay for a back

up house heater, would he be willing to pay more money for a waste heat  heat exchanger 

too?  Would it be economical?  Another factor which is yet another setback is the
variation in the availability and temperature of the thermal effluent, due to the 
load variation of the plant.  At the peak production of the waste heat, will the user

also correspondingly need a peak amount of waste heat?  Will the supply of waste heat

always exactly match the needs of the consumer?  If not, the waste heat will have to

be disposed of in other ways, which is an added problem for the power plant company.

Take for example the idea of using the waste heat to defog and deice airports; what 

will be done in the summer with the waste heat when the airport does not need the heat?

The fact that a 1000 MWe power plant produces such huge quantities of low grade waste
heat is a real problem for the company.  For instance, the heat produced from such a

plant  would  be able to heat 4.4 square miles of greenhouses.  There would have to

to be a lot of piping involved in the complete dispersal of this heat--which would cost!

Another problem is the consumptive use of the water in applications where the water is 

directly used, as in warm water irrigation.  Other problems include the quality of the

waste heat--will the consumer receive too much radioactivity in his supply from the

plant?  Of course, the major problem is the large distances between the plant and the

point of heat application--this presents a lot of expensive piping and pumping costs--

but people are very reluctant now to site the plant within l5 miles of a major city

because of safety reasons.
	These have been only a few of the many possible ways of utilizing the 
waste heat energy.  A lot of work is going to have to be done in order to have some
of these plans developed to the point where they would be seriously considered by
the power plant companies.  There are many problems still.  But, it is important
to continue to try to find the solutions to them.  With electrical production 
growing at such high rates, we simply cannot afford to waste two-thirds of the energy
used in the process.  Economic and environmental considerations, along with the fact
that fuel sources are becoming rare, will someday force the utilization of the waste
heat energy.  Therefore, we must plan now, before the reactors are built, to incorporate
some devices in the plants to use this extra energy, so that a possible transition
later will not be so difficult and costly.