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Carta de Cuba, la escritura de la libertad |
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JURAGUA: RADIOACTIVE FALLOUT THREAT MANUEL CEREIJO AUGUST 2000 CONTENTS - Introduction INTRODUCTION
Over the past 20 years Cuba has been faced with an ongoing
energy crisis. Depending heavily upon imported oil, the Cuban government has
attempted to seek an alternative to oil through nuclear energy. In
cooperation with the former Soviet Union, Cuba embarked on a project to
construct and operate a nuclear power plant in Cienfuegos, known as Juragua.
However, the collapse of the Soviet Union halted construction at Juragua.
In 1976 Cuba and the Soviet Union signed an agreement to
construct two 440 megawatt nuclear reactors in the south central province of
Cienfuegos, about 180 miles south of Key West, Florida. Juragua's reactors
are the first Soviet designed reactors to be built in the Western Hemisphere
in a tropical environment. Actual construction of the reactors began in
1983.
The loss of Soviet subsidies to Cuba after 1990 has sent the
Cuban economy into decline. Also, the newly formed Russian Federation
established new economic ties with Cuba based on a market economy. As a
result, on September 5, 1992, Cuba announced suspension of construction at
Juragua due to Cuba's inability to meet the financial terms set by Russia to
complete the reactors.
After 1995, bilateral cooperation between Cuba and Russia has
re-ignited the possibility of Juragua's completion in the near future.
Recently, as of July 2000, an official from the Russian Federation announced
the intention to resume construction of Juragua. The United States views a
nuclear reactor in Cuba as a threat to its national security. The U.S. has
cited numerous safety concerns associated with Juragua, believing in the
event of an accident it would be exposed to radioactive fallout.
The possibility of an accident occurring at Juragua, upon its
operation, according to experts, is 15 times greater than the probabilities
in a United States plant. According to air weather patterns around
Cienfuegos, it would take only 24 hours for radioactive materials to reach
Florida.
This monograph, the result of a research project
conducted by the author, presents a comprehensive analysis of the Juragua
plant, its design and construction problems which represents a
radioactive fallout threat for Cuba, Latin America, the Caribbean, and the
United States. The Juragua nuclear plant should not be permitted to start
operation under present conditions.
Energy Resources
Energy resources are the various materials that contain
energy in usable quantities. These are present in any of the various energy
forms that are transformable to other forms, including electrical,
mechanical, chemical, and nuclear energy.
The main energy forms include chemical, hydro, nuclear, and
geothermal energy. Chemical energy includes such fuels as coal, oil, and
natural gas. Energy resources are usually classified in two general
categories: renewable resources and expendable resources. Renewable
resources, such as water, wind, solar, and tide, are replaced continuously
by nature. Expendable resources, such as oil and coal, are expended when
used.
Energy may be classified as either primary energy, which is
obtained directly from nature, or secondary energy, which is energy derived
from primary energy. Primary energy sources include hydro, solar, wind, oil,
natural gas, and geothermal. Electrical energy is a form of secondary
energy. It is derived from primary energy by using thermal power plants to
convert heat energy and hydroelectric plants to transform the energy of
water under pressure.
Energy resources are being consumed at a high rate because of
the growing requirements of industries and the increasing demands of people.
It has been predicted that the world's supply of fossil fuels will be used
up within a few hundred years.
The rate of consumption of oil has been rapidly growing. In
many countries, oil has been the primary fuel used for electricity
generation. The fast growth of oil consumption is due mainly to its use as
fuel for automobiles and airplanes and the fact that it is easier to recover
and transform to other energy forms than solid fuels.
The distribution of natural gas reserves is not accurately
known. Estimates of these reserves are approximate. In the United States,
the use of natural gas has risen consistently because of its relatively low
cost. It has been estimated that the world's hydropower resources amount to
twice the current annual generation of all hydroelectric plants in the
world. The available hydropower depends on water inflows, and estimates of
the available hydro energy could be very approximate.
Geothermal energy is an almost limitless reserve. The
temperature of the Earth increases with depth in the Earth's crust.
Geothermal energy has been used very limited to supply hot water or as
geothermal power plants of low consumption.
It has been estimated that the heat content of the world's
reserves of uranium is more than 300 times the heat content of the world's
reserves of fossil fuels. Using nuclear fission, current nuclear power
plants convert only a small fraction of the energy present in the nuclear
fuel. However, the unexpended fuel can be reprocessed for use in breeder
reactors.
The oceans regularly rise and fall in response to the
relative positions of the Sun, Earth, and moon. The water elevation is not
the same at different places. The variation of water elevation can be used
by electric power plants to produce electric energy. However, such power
plants are extremely expensive, and the power output is quite variable.
Wind energy has been used in windmills around the world. Wind
turbines have also been used for electrical energy production in many
countries, but these have been in the low power levels. The Sun is the
ultimate source of energy because it has immense energy reserves. Solar
energy is usually used for space heating and water heating. Large collectors
are necessary to accumulate small amounts of power.
Electrical Energy
In 1878 Thomas A. Edison began work on the electric light and
formulated the concept of a centrally located power station with distributed
lighting serving a surrounding area. He perfected his light by October 1879,
and the opening of his historic Pearl Street Station in New City on
September 4, 1882, marked the beginning of the electric utility industry.
At Pearl Street, dc generators, then called dynamos, were
driven by steam engines to supply an initial load of 30 kW for 110-V
incandescent lighting to 59 customers in a 1-square mile area. From this
beginning in 1882 through 2000, the electric utility industry has grown at a
remarkable pace- a growth based on continuous reductions in the price of
electricity due primarily to technological accomplishment and creative
engineering.
At present, two methods are commonly used for electric
bulk-power generation. Both methods employ an electric generator that
converts the mechanical energy of the prime mover to electrical energy. The
main difference between the two methods is the source of the mechanical
energy used to rotate the generator.
One method makes use of water under hydraulic pressure to
provide the mechanical energy to rotate a hydraulic turbine whose shaft is
coupled to the generator shaft. The efficiency of conversion of the energy
available from the water to electric energy is quite high- up to 80% to 90%.
The other method employs a boiler to convert the energy of
the fuel coal, oil, or nuclear fuel-into heat energy, which is used to
transform water into high temperature steam at very high pressure. The
steam rotates the steam turbine in the same way as the water turns the
hydraulic turbine. The efficiency of conversion of the energy available from
the fuel to electric energy is much lower than the first method, typically
ranging from 30% to 40%.
The steam turbine generating units are the most widely used
in the United States to produce electricity. In a fossil-fueled steam
turbine, the fuel is burned in a boiler to produce steam. The resulting
steam then turns the turbine blades that turn the shaft of the generator to
produce electricity. In a nuclear-powered steam turbine, the boiler is
replaced by a reactor containing a core of nuclear fuel. Heat produced in
the reactor by fission of the uranium is used to make steam. The steam is
then passed through the turbine generator to produce electricity.
Steam turbine generating units are used primarily to serve
the base load of electric utilities. Fossil-fueled steam turbines generating
units range in size from 1 megawatt to more than 1,000 megawatts. The size
of nuclear powered steam turbine generating units ranges from 75 megawatts
to more than 1,400 megawatts.
Hydroelectric power is the result of a process in which
flowing water is used to spin a turbine connected to a generator. The two
basic types of hydroelectric systems are those based on: falling water;
natural river current. These conventional hydroelectric generating units
range in size from less than 1 megawatt to 700 megawatts. Because of their
ability to start quickly and make rapid changes in power output,
hydroelectric generating units are suitable for serving peak loads and
providing spinning reserve power, as well as serving base load requirements.
The ultimate objective of any power system is to deliver
electrical energy to the consumer safely, reliably, economically, and with
good quality. Operation of the power system requires that proper attention
be given to the safety not only of the utility personnel but also of the
general public. At the consumer load centers, electrical energy is converted
to other more desirable and useful forms of energy. This implies that the
supply of electricity should be available where, when, and in whatever
amount the consumer requires.
Electrical loads are commonly grouped into four categories:
residential, commercial, industrial, and other.
Residential loads are private homes and apartments. They
include lighting, cooking, heating and cooling, refrigerators, water
heaters, washers and dryers, and many other different appliances.
· Commercial loads include office buildings, department
stores, grocery stores, and shops.
· Industrial loads consist of factories, manufacturing
plants, and other industrial factories. Industrial loads contain various
types and sizes of motors, fans, presses, furnaces, and so on.
Electrical load refers to the amount of electrical energy or
electrical power consumed by a particular device or by a whole community. It
is also referred to as electrical demand. At the individual consumer level,
the electrical demand is quite unpredictable. However, as the demands of the
various users are accumulated and added at a feeder or a substation, they
exhibit a definite pattern.
The U.S. electric power industry is organized to ensure that
an adequate supply of electricity is available to meet all demand
requirements at any given instant, both now and in the future. The rating of
a generator is a measure of its ability to produce electricity. The capacity
of the generator is the full load continuous rating of the generator under
specified conditions. Net capability is the steady hourly output that the
generating unit is expected to supply to the system load. The capacity of a
generator is generally higher than its net capability.
The generating units operated by an electric utility vary by
intended usage; that is, by the three major types of load-base,
intermediate, and peak-requirements the utility must meet.
*A base- load generating unit is normally used to satisfy all
or part of the minimum or base load of the system and, as a consequence,
produces electricity at an essentially constant rate and runs continuously.
Base-load units are the newest, largest, and most efficient of the three
types of units.
*A peak-load generating unit, normally the least efficient of
the three unit types, is used to meet requirements during the periods of
greatest or peak load of the system.
*Intermediate-load generating units meet system requirements
that are greater than base load but less than peak load. Intermediate-load
units are used during the transition between base-load and peak load
requirements.
*Utilities also have reserve or standby generating units,
which are available to the system in the event of an unexpected increase in
load or an unexpected outage of the system.
From both an operational and functional point of view the
power network can be divided into several substructures based upon operating
voltage levels. Highest on the voltage scale is the transmission or the
power grid. The power is transformed in bulk power substations and fed into
the sub-transmission system. The sub-transmission system forms and
intermediate and more fine meshed link between the grid and the distribution
circuits. The power finally is fed into the fine meshes of the distribution
system via distribution substations
In the United States, the voltage of large generators is
usually in the range13.8 to 2.4kv (kilovolts). Large modern generators,
however, are built for voltages ranging from 18 to 24kV. However, there is
no standard for generator voltages. The voltage generated at a station is
stepped up to transmission levels in the range 115 to 765kV. The standard
high voltages are 115, 138, and 230kV. Extra high voltages are 345, 500, and
765kV. High voltage transmission usually employs overhead lines supported by
steel, cement, or wood structures. The application of underground
transmission is mostly confined to urban areas and wide bodies of water. The
power is then stepped down depending on the use or application.
As of January, 1999, the existing capacity of U.S. electric
utilities totaled 686,692 megawatts. Based on primary energy source,
coal-fired capacity represented 44% (299,739 megawatts) of the nation's
existing capacity. Gas-fired capacity accounted for 18%(125,386
megawatts); nuclear, 14%(97,070 megawatts);petroleum, 9%(62,959 megawatts);
hydroelectric,11% (77,593 megawatts; other, 11% (77,593 megawatts).
Of the existing capacity, we have:
(a) Conventional
steam-electric units accounted for 62%.
(b) Nuclear units accounted for 14%
(c) Hydroelectric,11%.
The approximate existing capacity in the United States is of
3,300 watts per person. Construction costs for a typical plant range from
$450 per kilowatt for combined-cycle technologies to $1,100 per kilowatt for
coal steam technologies. Refurbishment of existing plants is sometimes less
expensive and a better option to consider.
Cuba: Electrical Energy
Up to 1959, Cuba was supplied of electrical energy by the
following major utilities:
(1) Compaņia Cubana de Electricidad (CCE). CCE was a
subsidiary of the American and Foreign Power Company, previously part of the
Electric Bond and Share Co.-EBASCO. CCE's service territory included the
Eastern part of Pinar del Rio province, La Habana, Matanzas, Las Villas,
Camaguey, and the Southern part of the Oriente province.
(2) Hernandez y Hermanos. Its service
territory included the western part of Pinar
del Rio province and the cities of Trinidad, Casilda and several towns in
Las Villas province.
(3) Tabares. Its service territory included the
northern and central part of the Pinar del Rio province
(4) Islas de Pinos utility. Covering Isla de
Pinos
(5) Many other spotted areas were served by the large
sugar mill industry or the larger industrial complexes in the Island.
All these utilities were franchised and regulated by the
Public Service Commission, under the Ministry of Communications. Presently,
all electric generation, transmission, and distribution of electric energy
in Cuba is controlled by the government through the entity Empresa Electrica
Cubana, under the Ministry of Basic Industries. There are no private
electric utility companies in Cuba.
Cuba has an installed generating capacity of 3,500 megawatts.
However, the net generating capacity is only 1,200 megawatts. The industry
employs some 29,000 workers, of which, 4000 are technicians, and 850 are
engineers. The electrical energy demand was in 1996 of 2,500 megawatts,
distributed as follows:
*60% industrial
*4% agricultural
*8% commercial
*25% residential
The rest is for miscellaneous loads. However, in 1999 the
demand diminished to 950 megawatts, mainly due to the large decrease in the
industrial and residential loads.
The composition of the main units, equipment, instruments,
and components is very diverse. The main suppliers are: United States (pre
Castro), former Soviet Union, Japan, Italy, France, Czech Republic, Germany.
The main generating plants are:
(1) Mariel, capacity 600 megawatts
(2) Tallapiedra, capacity 200 megawatts
(3) Regla, capacity 200 megawatts
(4) Santa Cruz del Norte, capacity 300 megawatts
(5) Antonio Guiteras, capacity 350 megawatts
(6) Cienfuegos, capacity 400 megawatts
(7) Felton, capacity 250 megawatts
(8) Nuevitas, capacity 200 megawatts
(9) Rente, capacity 300 megawatts
(10) Hanabanilla, ( Hydroelectric), capacity 45 megawatts.
There are a total of 46 operating units located in 20
different sites. The transmission voltage is 110 kV and 220 kV. The country
is mainly interconnected with a 220kV grid. Transmission conductors are ACSR
150mm. Transmission structures are concrete, metal, and H frame made of
wood. Distribution voltages are 4.16 kV and 13.8 kV, and the system operates
at 60 Hz. Distribution conductors are 150 mm, 70 mm, and 35 mm ACSR. Almost
all distribution is overhead, except some underground in La Habana.
Approximately 95% of the generating units in Cuba use No. 6
fuel oil. A 4% use No. 2 fuel oil. Due to the wide range of unit
ages and country of origin present in the system, the sizes and operating
parameters are very diverse. The age range of the units vary from 8 years,
the newest one installed in Felton, to over 45 years for the ones present in
Cuba before 1959. Usually accepted economical and technical life for steam
generating units is 30 t0 35 years. An estimated 35% of the units installed
in Cuba are small, inefficient, and over the accepted range of operating
life.
Cuba consumed 13 million tons of oil in 1989, of which, 7
million tons, or 40 million barrels were for the generation of electricity.
In 1999, Cuba consumed, for all needs, 6.3 million tons of oil. Of these,
approximately 1.3 millions were domestic oil . Domestic oil is not suitable
as a fuel for the generating units because of the high content of sulphur,
9%, which if used in the boilers, creates sulphuric acid, which corrodes the
boilers.
The percentage of Cuba's oil consumption is as follows:
· 50% imported crude oil
· 35% imported, refined
· 15% domestic production crude oil.
Cuba's domestic oil reserves are scant, so increasing
domestic production is not feasible.
Cuba has presently an installed capacity of 290 watts per
person. However, it has a net generating capacity of 100 watts per
person. It is estimated that a country, in order to sustain a stable
economic and industrial growth should have available at least 500 watts per
person of net generating capacity.
The most prevalent problems with the electrical energy system
in Cuba are:
(1) insufficient net generating capacity
(2) dependence on imported oil as fuel
(3) lack of reliability
(4) inefficiency of the system
(5) poor condition of the transmission and distribution
system.
This analysis take us to the fundamental question. Was it
necessary to install a nuclear power generating plant in Cuba? The answer is
a conditional yes. We will explain the reasons in the rest of the monograph.
What is nuclear power?
Nuclear power taps the ultimate source of energy which powers
the universe and its myriads of stars like our Sun. Nuclear engineers
deliberately arrange to split certain atoms-this is called nuclear fission.
When this happens, some matter gets destroyed, liberating huge amounts of
energy. This energy mostly ends up as heat from which you can make steam to
drive turbines and generators (referred to in sections above), and make
electricity in power stations.
By careful design using material like uranium, engineers
ensure that neutrons collide with uranium atoms, breaking them apart into
unequal size halves. This yields energy and more neutrons and is called
nuclear fission. Repeat this, and you have even more neutrons. If the
uranium is the right type-uranium 235, a potent heat-releasing but
controllable chain reaction starts up. This is what powers reactors.
Reactors use a low grade of U-235 which can not sustain the
atomic bomb type reaction. This is why reactors contain tons of uranium,
whereas a bomb needs only a few kilograms. Because reactor grade uranium,
most of which is uranium 238 which is not fissile, contains only 1 to 2%
U-235, neutrons have to be slowed or they simply bounce off other uranium
atoms.
Engineers slow down the neutrons with a moderator which
increases the likelihood of them smashing another U-235 atom to continue the
reaction. The moderator can be graphite or ordinary water, designated
pressurized Water reactors, PWRs, the most commonest reactor type around the
world. In PWRs, the water slows the neutrons and also cools the core.
Powerful pumps cycle the hot water out of the reactor core into enormous
steam generators.
JURAGUA
As seen above, over the past 20 years Cuba has been faced
with an ongoing energy crisis. Depending heavily upon imported oil, the
Cuban government has attempted to seek an alternative to oil through nuclear
energy. In cooperation with the former Soviet Union, Cuba embarked on a
project to construct and operate a nuclear power plant in Cienfuegos, known
as Juragua. However, the collapse of the Soviet Union halted construction at
Juragua. Recent bilateral cooperation between Cuba and Russia has re-ignited
the possibility of Juragua's completion in the near future. The United
States views a nuclear reactor in Cuba as a threat to its national security.
The U.S. has cited numerous safety concerns associated with Juragua,
believing in the event of an accident it would be exposed to radioactive
fallout. Figures #s 1, 2 and 3 show geographical location for Juragua.
Description
In 1976 Cuba and the Soviet Union signed an agreement to
construct two 440-megawatt nuclear power reactors in the south central
province of Cienfuegos, near Juragua, about 180 south of Key West, Florida.
Juragua's nuclear reactors are of the model VVER-440, of Soviet design and
are the first Soviet-designed reactors to be built in the Western Hemisphere
in a tropical environment.
The arrangement was aimed at alleviating Cuba's dependency
upon foreign oil while bolstering its electricity capacity. The importation
of oil has drained Cuba of its sparse hard currency. At the same time the
country's production of electricity has been fraught with difficulties. As
of 1992 Cuban power plants have been working at only 47% of their capacity,
leading to frequent blackouts. This figure has fallen further due to the
relative decline in the Cuban economy since 1998. Upon completion, the first
reactor, Juragua #1, would generate approximately 15% of Cuba's energy
demands. Figure #s 4 and 5 show construction site of Juragua at two
different years.
Actual construction of the reactors began in 1983. The Soviet
Union supplied a majority of the reactor parts, dispatched technicians to
supervise construction, and trained Cuban engineers to operate the reactors.
According to 1992 GAO report, Russia tentatively scheduled the first reactor
to be operational in late 1995. This was due in part to the Cubans
constructing the reactor lacking experience and with all critical work being
performed by Russians or under their supervision.
However, the breakup of the Soviet Union disrupted
construction at Juragua. The newly formed Russian Federation in conjunction
with its transitioning into a market economy established new economic ties
with Cuba. Current bilateral ties between Russia and Cuba, now, involve
providing technical assistance to Cuba on a commercial basis.
At the same time the loss of Soviet subsidies to Cuba
after 1990 has sent the Cuban economy into decline. As a result, on
September 5, 1992, Cuba announced a suspension of construction at Juragua
due to Cuba's inability to meet the financial terms set by Russia to
complete the reactors.
A September 1992 GAO report estimated that civil construction
on the first reactor ranged from 90% to 97% complete with only 37% of the
reactor equipment installed. About 25% of the civil construction on the
second reactor was completed with the status of the equipment unknown.
Cuban-Russian attempts to resume construction at Juragua took
place in October 1995. A high-level Russian delegation with full backing of
the government arrived in La Habana to conclude an agreement to complete
construction. To raise the $ 800 million dollars necessary to complete
the reactors, Russia and Cuba decided to form a syndicate with potential
third parties. Companies in Britain, Brazil, italy, Germany, and Russia
expressed interest in an economic association.
However, nothing concrete came out at that time. Cuba was
rewarded with a $50 million dollar grant loan from Russia for support work
at Juragua. Cuba now receives financial support for the Juragua plant from
the International Atomic Energy Agency (IAEA). The AIEA has provided nuclear
technical assistance in atomic energy development and in the application of
isotopes and radiation.
The AIEA has provided from 1991 to 1996 about $680,000 to
Cuba to develop the ability to conduct a safety assessment of Juragua
reactors, and in preserving or "mothballing"the reactors while
construction is suspended. This assistance increased during 1997 to 1999. It
is estimated that through the last 20 years the IAEA has provided Cuba with
some $14 million dollars. We will dealt with this topic in a following
section of the report.
Recent events have lead to the speculation of resumption of
construction in the near future. Recently, July 2000, an official from the
Russian Federation announced the intention to resume construction of
Juragua. This will be accomplished through an international consortium of
countries, including Russia. Upon resumption of construction, the Juragua
first reactor is expected to be operational within a 14 month timespan.
Impact
In the event of an accident during Juragua's operation
radioactivity could leak from the plant. Such an accident would have a
severely adverse effect upon Cuba, United States, Mexico, Central America,
and the Caribbean. Once the reactors are operational, Cuba will have to
develop plans to deal with nuclear waste generated by the reactors.
Currently there are no appropriate sites to deposit nuclear waste in Cuba.
The Cuban government plans to dump waste in an area at sea
level near the Juragua plant. This would contaminate flora, fauna and Cuban
population.
Cuba's attempt to establish a nuclear power plant has been
met with substantial opposition in the United States and from environmental
international agencies. Several experts indicate that the Juragua reactor is
inundated with safety problems: structural defects in support structure in
key reactor components, integral reactor systems, including the reactor
vessels, steam generators and primary cooling pumps were exposed to highly
corrosive tropical sea weather, poor training and experience level of the
Cuban personnel who were trained on Soviet model reactors which are
different from Juragua, and that as many as 10% of 5,000 approved
welds in key reactor equipment were found to be defective.
Four similar Juragua type reactors (VVER-440) in East Germany
were immediately shut down by West Germany upon reunification. Similar
plants in Hungary, Czechoslovakia and Bulgaria were under inspection, shut
down, or have received extensive modification.
The plant instrumentation and controls, for example, reactor
protection systems and diagnostics are behind Western standards. The
separation of the plant safety systems, to help assure that an event in one
system will not interfere with operation of others, fire protection, and
protection for control-room operators are below Western standards.
The reactors have poor leak-tightness of confinement. There
is also an unknown quality of plant equipment and construction, due to lack
of documentation on design, manufacturing and construction, and reported
instances of poor quality materials being re-worked at plant sites. There
are also major variations in operating and emergency procedures, operator
training, and operational safety among plants using VVER-440.
The possibility of an accident occurring at Juragua, upon its
operation, according to experts, is 15 times greater than the probabilities
in a United States plant. Currently, Cuba lacks a comprehensive system to
perform systematic readings that monitor radioactivity to prevent potential
accidents. According to air weather patterns around Cienfuegos, it would
take only 24 hours for radioactive materials to reach South Florida.
Meltdowns
How can radioactivity be released from a nuclear power plant?
The only way that potentially large amounts of radioactivity could be
released from a nuclear plant is by melting of the fuel in the reactor core.
The fuel that is removed from a reactor after use and stored at the plant
site also contains considerable amounts of radioactivity. To melt the fuel
requires a failure in the cooling system or the occurrence of heat imbalance
that would allow the fuel to heat up to its melting point, about 5000
degrees F.
It might seem that all that is required to prevent fuel from
overheating is to promptly stop, or shut down, the fission process at the
first sign of trouble. Although reactors have such fast shutdown systems,
they alone are not enough since the radioactivity decay of fission fragments
in the fuel continues to generate heat that must be removed even after the
fission process stops. Therefore, reactors should have redundant decay heat
removal systems. In addition, emergency core cooling systems should be
provided to cope with a series of potential accidents, caused by ruptures
in, and loss of coolant from, the normal cooling system.
There are two broad types of situations that might
potentially lead to a melting of the reactor core: the loss of coolant
accident (LOCA) and transients. In the event of a potential loss of coolant,
the normal cooling water would be lost from the cooling systems and core
melting would be prevented by the use of the emergency core cooling systems(
ECCS). However, melting could occur in a loss of coolant if the ECCS were to
fail to operate.
The term transient refers to any one of a number of
conditions which could occur in a plant and would require the reactor to be
shut down. Following shut down, the decay heat removal systems would operate
to keep the core from overheating. Certain failures in either the shutdown
or the decay heat removal systems also have the potential to cause melting
of the core.
The water in the reactor cooling systems is at a very high
pressure (between 50 to 100 times the pressure in a car tire) and if a
rupture were to occur in the pipes, pumps, valves, or vessels that contain
it, then a blowout would happen. The specific LOCA initiating events have
been identified as:
A. Small pipe breaks
B. Large disruptive reactor vessel ruptures
C. Gross steam generator ruptures
D. Ruptures between systems that interface with the cooling
system
Studies have indicated that a core meltdown in a large
reactor would likely lead to a failure of the containment. Therefore, the
containment integrity is very important.
Fuel melting accidents release more than 200 different
radioactive substances, of which, 54 are very dangerous. The Nuclear
Regulatory Commission, NRC, which oversees the United States' nuclear power
plants, says exposure should not exceed 25 millirem per year, while the
Environmental Protection Agency, EPA, has set a standard of 15 millirem,
with ground water levels not to exceed 4 millirem.
Aroutine chest X-ray contains 6 millirem. Dosages above
30,000 millirem are known to cause cancer, and levels of 400,000 millirem
can cause death in days. Another international unit used is the curie. For
example, the nuclear accident at Chernobyl, the worst nuclear accident to
date, spewing about 100 million Curies, or 4x10^18 becquerels, of
radioactive material into the environment. By contrast, the Three Mile
Island released only some 15 Curies.
Accidental Release of Radioactivity from Juragua
Radioactive pollutants released into the atmosphere will form
a plume that can be transported and dispersed by air currents, thus reaching
areas distant from the release location. It is therefore possible to
construct maps of a plume impact, average time of arrival, and relative
plume concentration from a single pollutant release, given the release
location, meteorological data, a transport and dispersion model, and a
statistical analysis program to determine useful and accurate results.
The release of radioactivity to the air from a nuclear power
station accident differs in at least one way from that produced by nuclear
tests. The radioactivity is injected near the ground and not at high
altitude as with tests. The two scavenging mechanisms that physically remove
the radioactivity from the air, namely, wet and dry fallout, are more
effective when a radioactive cloud is near the ground rather than at high
altitudes.
Meteorological data are routinely generated from the National
Oceanic Atmospheric Administration (NOAA). The NOAA, the Meteorological
Center and the Air Resources Laboratory (ARL) have conducted experimental
data on air emanating from Cienfuegos, in one complete year. The geographic
domain in the analysis for a Cienfuegos release was a grid (95 km. Spacing)
including all of the U.S., Mexico, the western Atlantic, Gulf of Mexico, and
the Caribbean sea.
A release was assumed every 6 hours for the month, with the
transport following each release continuing for a duration of 5 days. This
duration was chosen so all plumes would approach or cross the geographic
domain boundaries. Simplified graphs and maps are presented in the next
page.
The main feature of the probabilities is that shows
relatively higher values to the west and northwest of Cienfuegos. Relative
concentrations at Miami, Fl., and Houston, Texas are about the same during
the Summer. However, Miami and Tallahassee, Fl. show very high probability
of impact during the winter.
Average time of plume arrival, as well as earliest time of
plume arrival show Miami with the highest in all seasons. Central America,
the Gulf of Mexico, and the Caribbean, show very high probabilities of
impact as Tallahassee and Houston. The average time it would take for
radioactivity from Cienfuegos to reach southern Florida is 48 hours. The
shortest time would be less than 24 hours. Figures #s 6, 7, 8 show the
geographical impact areas in case of a fallout.
VVER-440 reactors
A VVER-440 reactor is a pressurized water reactor developed
from a reactor design based on the first nuclear submarine reactors in the
Soviet Union, where de-mineralized light water is applied as both cooling
agent and for moderating the neutrons. The first version, VVER-440/230, was
developed in the 60's, while the VVER-440/213 was introduced in the 80's. It
is a Russian version of the Pressurized Water reactor (PWR). There are three
standard designs-two 6 loop-440 megawatt(the 230 and 213 models), and 4
loop-1000megawatt output designs. Re-fuelings are conducted with the plant
shutdown. Figures 9, 10 show general diagrams of the VVER 440.
The reactor core in a VVER-440 reactor is 3 meters in
diameter, has a height of 2.5 meters, and is enclosed by a cylindrical
pressure receptacle of steel, of a diameter of 4.3 meters and a height of
11.8 meters. The total weight is 200 tons. The reactor core contains 312
fuel assemblies and 37 control assemblies. Each fuel assembly consists of
126 fuel pins, which in turn consists of uranium-dioxide pellets. The
content of 235U in the fuel is replaced by new, non-irradiated fuel
assemblies. The temperature of the cooling water as it leaves the reactor is
between 295 and 300 degrees Celsius.
Each reactor coolant loop includes a steam generator and a
reactor coolant pump. The water passes through the inside of the tubes in
the steam generator. The reactor coolant pump circulates the water for
cooling the reactor core. The system is pressurized to 2200+ pounds per
square inch by a pressurizer, which is connected to one of the reactor
coolant loops.
In the third schematic (model 230), Figure 11, the numbers
indicate:
1. Reactor
2. Steam Generator
3. Main Circulation Pump
4. Refueling Machine
5. Cooling pond
6. Deaerator
7. Steam Turbine
8. Generator
9. Steam Pipelines
10. Cooling Water Pipelines
11. Transformer
In the fourth schematic (model 213), Figure 12, the numbers
indicate:
1. Reactor pressure vessel
2. Steam generator
3. Refueling machine
4. Spent fuel pit
5. Confinement system
6. Make-up feedwater system
7. Protective cover
8. Confinement system
9. Sparging system
10. Check valves
11. Intake air unit
12. Turbine
13. Condenser
14. Turbine block
15. Feedwater tank with degasifier
16. Preheater
17. Turbine hall crane
18. Electrical instrumentation and control compartments
A major difference between western designed PWRs and the
VVERs is that the latter have horizontal steam generators. The older VVERs
have isolation valves in the reactor coolant loops and accident localization
compartments. Water passing on the outside of the steam generator tubes is
heated and converted to steam. Steam in the VVER design is not expected to
be radioactive. The VVER 440 design includes accident localization zones and
a confinement rather than a true containment.
The VVER-440 in Juragua belong to the "second
generation" of the VVER family. However, they do not meet western
standards. They also have an inadequacy of the upper portion of the
reactor's dome retention capability to withstand only 7 pounds of pressure
per square inch, given that normal atmospheric pressure is 32 pounds per
square inch and United States reactors are designed to accommodate pressures
of 50 pounds per square inch. Normal air pressure at sea level, the level at
which the plant is being constructed, is 14.7 pounds per square inch.
Therefore, the dome cannot survive when exposed to the atmosphere.
The design of the Cuban reactor has many features in common
with those of the U.S., but there are several differences that could lead to
significantly different reactions in the event of a serious accident. For
example, while the Cuban reactor, like the U.S. PWRs, use water to cool the
reactor core, the Cuban reactor uses a different system for handling the
steam pressure that would be generated by a severe accident.
In the Cuban reactor, the steam is condensed so that pressure
is reduced in the containment structure. If, in the case of a severe
accident, the system for condensing the steam is bypassed and the steam
reaches the upper portion of the containment in pressures greater than the
upper portion's designed pressure retention capability of 7 pounds per
square inch. The containment could be breached and a radioactive release
could occur. In contrast, U.S. PWRs are designed to accommodate pressures of
about 50 pounds per square inch throughout the containment structure.
Another main difference between the VVER-440 reactors and
reactors of Western type is the degree of safety containment surrounding the
reactor tank of the VVER-440.The airtight safety containment of Western
power plant encloses the reactor tank, the primary-and secondary circuits,
as well as the steam generators. At a possible leakage, the safety
containments will see that the radioactive steam does not escape to the
surroundings. At Western reactors, this safety containment is made of
prestressed concrete.
Also, there are devices for cooling the steam to decrease the
pressure. The construction surrounding the reactor systems of the VVER-440
has a volume too small to relieve the pressure arising should a breach occur
in pipes of more than 32 mm in diameter. The construction is fitted with
valves, which are released if the pressure gets too high.
Integral reactor systems, including the reactor vessel
itself, six steam generators, five primary coolant pumps, twelve isolation
valves and more, were stored outside for months, exposed to the highly
corrosive tropical sea air and weather. No nuclear reactor of Soviet design
has ever been constructed in a tropical climate.
The group of the world's seven richest countries (G7) has
concluded that all reactors of the VVER-440 type must be shut down as soon
possible, as the reactors are upgraded to Western safety standards. Even the
World Bank emphasizes the serious defects of reactors of this type,
rendering any reconstruction unprofitable. From an economical point of view,
the World Bank claims nuclear power plant with reactors of the VVER-440 type
to be the most expensive energy alternative for the years to come.
There are eight VVER-440 reactors in operation in former
Eastern Europe and Russia. These are localized in Bulgaria, Slovakia,
Russia. Refer to Figure 13. Six additional reactors of this type have
formerly been in operation in, but are now shut down. Four reactors were in
operation at the nuclear power plant of Greifswald in former DDR. The
reactors were dismantled by the German authorities after the reunion due to
the lack of security at this type of reactor. There are two reactors in
Armenia, but they are temporarily shut down due to their poor state.
On the construction side, the VVER-440 reactors deviate from
safety standards of Western reactors. IEAA performed in 1991 a safety
analysis of the 10 reactors in operation, and found 100 safety aspects
connected to the design and the operation of the plants. More than 60% of
these aspects are of great importance when safety is concerned.
The main problems concerning the design of the reactor type
is as following:
· Deficiencies in the construction concerning the limitation
of discharges to the surroundings in case of breaches in pipes of more than
32 mm in the primary circuit
· Lack of safety containment surrounding the core
· Limited capacity of the cooling system
· Unsufficient "backup" of the cooling system and
safety system
· Lack of distinction between control systems and safety
precautions concerning fire
· Obsolete control room technology
Neutron irradiation of the reactor tank, causing the steel to
become brittle, is a vital safety issue of the VVER-440 reactors. The
proximity of the fuel assemblies to the steel walls in the VVER-440 reactor
tank, causes higher neutron irradiation than in other types of reactors, and
the walls to become brittle at a higher pace than normal. The VVER-440
reactor tank is made up of welded rings. The welded seams are particularly
exposed to neutron irradiation. As a remedy, in some designs during the late
80's, the outermost assemblies were replaced with steel rods.
Light-water reactors are considered safer than the
graphite-cooled model that was in use in Chernobyl, Ukraine, site of the
world's worst nuclear accident. But the Russian-designed VVER-440 light
water reactors do not meet the safety standards of Western nations. The
design is considered unsafe and should not be in operation.
International Atomic Energy Agency (IAEA)
Since 1958, the IAEA, in promoting the peaceful uses of
nuclear energy, has been providing nuclear technical assistance to its
member states through projects that supply equipment, expert services, and
training. Currently, more than 90 countries receive nuclear technical
assistance, mostly through over 1,000 projects in IAEA's technical
cooperation program.
The United States is a member of IAEA and its major financial
contributor. IAEA is providing nuclear technical assistance to Cuba in
10 program areas, including general atomic energy development, the
application of isotopes and radiation in medicine, agriculture, and nuclear
safety. Most of the assistance, however, has been for Cuba's partially
constructed nuclear power reactors.
IAEA spent about $12 million on nuclear assistance projects
for Cuba since 1963 through 1996. About 75% of the assistance Cuba received
through these projects consisted of equipment, radiation related
instruments, and laboratory equipment. The rest was in the area of general
atomic energy development. IAEA recently approved an additional $1.7 million
for nuclear technical assistance projects for Cuba for 1997 through
1999.
In addition, IAEA spent about $2.8 million on training Cuban
nationals and research contracts for Cuba. The United States contributes
about 40% of the total funds of the agency for such projects. IAEA is
assisting Cuba in developing the ability to conduct assessments of the
nuclear power reactors and in preserving or "mothballing" the
reactors while construction is suspended.
Nuclear Waste Disposal
The disposal of radioactive waste from nuclear power plants
is a very serious problem. Nuclear waste can be generally classified as
either low level radioactive waste or high level radioactive waste. Low
level nuclear waste usually includes material used to handle the highly
radioactive parts of nuclear reactors, like cooling water pipes and
radiation suits, and waste from medical procedures involving radioactive
materials. Low level waste is comparatively easy to dispose of.
High level radioactive waste is generally material from the
core of the nuclear reactor. Most of the radioactive isotopes in high level
waste emit large amounts of radiation and have extremely long half-lives,
some larger than 100,000 years, creating long time periods before the waste
will settle to safe levels of radioactivity. Radioactive wastes, being
highly toxic, can destroy or damage living cells, causing cancer and
possibly death depending on the quantity and length of exposure. In
addition, radioactive material can be mutagenic, thereby transmitting
biological damage into the future.
Every 12-24 months the reactor of a nuclear power plant is
shut down and the oldest fuel assemblies, which have released their energy
but have become intensely radioactive as a result of fission, are removed
and replaced. The fuel which has been consumed is known as "spent"
nuclear fuel, SNF. Spent nuclear fuel can be dissolved in a chemical process
called "reprocessing", which is used to recover desired
radionuclides.
If SNF is not reprocessed prior to disposal, it becomes the
waste form without further modification. The only commercial reprocessing
facility to operate in the United States closed in 1972. Since that time, no
commercial SNF has been reprocessed in the United States. Where are the
wastes stored now?
Today, most SNF is stored in water pools or above-ground in
dry concrete or steel canisters at more than 70 commercial nuclear-power
reactor sites across the nation. Also, waste is stored underground in steel
tanks at four Federal facilities in Idaho, Washington, South Carolina, and
New York. Plans are to store SNF at Yucca Mountain repository in Nevada.
All high level radioactive waste must end its journey in long
term storage. The waste must not be allowed to escape to the outside
environment by any foreseeable accident, malevolent action, or geological
activity. This includes accidental uncovering, removal by groups intending
to use the radioactive material in a harmful manner, leeching of the waste
into the water supply, and exposure from geological movement activity.
The extreme lethality of a freshly removed spent fuel bundle
is such that a person standing within a meter of it would die within an
hour. The hazards associated with transportation, in particular the
possibility of accidents, are very serious. Therefore, the minimization of
handling and transporting spent fuel is a desirable objective.
Areas currently being evaluated for storage of nuclear waste
are space, under the sea bed, and large stable geologic formations on land.
Long term storage on land seems to be the favorite of most countries. Cuba
has not serious plans at this point for the proper disposal of nuclear
waste, neither is technical or economical prepared to dispose safely of the
nuclear waste.
Caribbean Early Warning System (CREWS)
The Caribbean Radiation Early Warning System, CREWS, is
designed in response to the technical challenges presented by the proximity
of the Juragua nuclear reactors to the U.S. and other Caribbean neighbors.
The primary objectives of CREWS are: (1) create an early warning system that
provides actionable and timely data for emergency preparedness in the event
of a catastrophic radioactivity release, and (2) establish a high
sensitivity regional monitoring network capable of detecting small releases
of radioactivity that could be pre-cursors of potentially larger operational
problems.
The components of the CREWS regional monitoring system are
comprised of field sensors, a central data analysis facility, a central
measurement facility, and a meteorological support group. The backbone of
the system is a network of airborne radioactivity monitoring stations that
are capable of meeting the early warning and high sensitivity objectives of
the mission. The primary functions are:
· Field sensors: Semi automatic sensors will collect, assay,
and transmit raw data.
· Central Data Analysis Facility: This facility houses the
processing and analysis capability to monitor the data from the field
sensors.
· Central Measurement Facility: This facility is capable of
achieving detection sensitivities of the order of micro becquerels per cubic
meter.
· Meteorological Support Group: A link will be created with
an existing facility to provide meteorological support in the event of a
significant release of radioactivity.
Conclusions
1. Three of the VVER projects started by the former Soviet
Union during the late 70's and early 80's encountered serious problems that
led to their suspension. Of these three, two found solutions to their
problems through the technical and financial help of other countries. Only
Juragua remains uncompleted
2. The Cuban government is actively seeking financial and
technical assistance to finish Juragua. Feasibility studies indicate
that $400 million dollars are needed to finish the first reactor. Once
construction is resumed, a 14 month time span will be needed to make
operational the reactor.
3. The civil construction of the first reactor is 97%
complete. Approximately 40% of the reactor equipment is installed.
4. In the event of an accident during Juragua's operation,
radioactivity could leak from the plant with an adverse effect upon Cuba,
United States, Mexico, Central America, and the Caribbean.
5. The release of radioactive to the air from a nuclear plant
is more effective than the one produced from nuclear tests. Meteorological
data conducted by the National Oceanic Atmospheric Administration, NOAA, and
the Air Resources Laboratory, ARL, show an early arrival of radioactivity to
Florida of less than 24 hours. The average time of arrival would be 48
hours. In 72 hours, areas affected will be Central America, Mexico,
the Caribbean, and most of the U.S. Eastern Seaboard.
6. The cities with a major impact in the U.S. will be Miami,
Florida; Houston, Texas, and Tallahassee, Florida.
7. The main problems concerning safety related to the
Juragua's reactor are:
· Deficiencies in the construction concerning the limitation
of discharges to the surroundings in case of breaches in pipes of more than
32 mm in the primary circuit.
· Lack of safety containment surrounding the core
· Limited capacity of the cooling system
· Insufficient backup of the cooling system and safety
system
· Lack of distinction between control systems and safety
precautions concerning fire
· Obsolete control room technology
· Neutron irradiation of the reactor tank could cause the
steel to brittle
· Reactor dome has a retention capability to withstand only
7 pounds of pressure per square inch. Standard in the U.S. is 50 pounds per
square inch
· Unknown quality of plant equipment and construction
· Lack of documentation on design, manufacturing and
construction
· Reported instances of poor quality materials being
re-worked at plant site.
· Reactor protection systems and diagnostic behind Western
standards
· Separation of the plant safety systems, and protection for
control room operators are below Western standards
8. The possibility of an accident occurring at Juragua, upon
its operation, is estimated to be 15 times greater than the probabilities in
a United States plant.
9. Cuba lacks a comprehensive system to perform systematic
readings that monitor radioactivity to prevent potential accidents.
10. Six similar reactors of the Juragua type operating in
Eastern Europe were shut down due to the lack of security of the reactors.
11. The IEAA performed in 1991 a safety analysis of the 10
reactors similar to the Juragua's, remaining in operation, and found 100
safety aspects connected to the design and the operation of the
plants. More than 60% of these aspects are of great importance, and are not
acceptable by Western standards.
12. The group of the world's seven richest countries (G7) has
concluded that all reactors of the VVER-440 type must be shut down as soon
as possible, and the reactors should be upgraded to
Western safety standards. The World Bank emphasizes the serious defects of
the reactors of this type, rendering any reconstruction unprofitable.
13. Integral reactor systems-including the reactor vessel
itself, six steam generators,
five primary coolant pumps, twelve isolation valves and
more-were stored outside for months, exposed to the highly corrosive
tropical sea air and weather. Also, no nuclear reactor of Soviet design has
ever been constructed in a tropical climate.
14. Cuba has not serious plans at this point for the proper
disposal of the nuclear waste generated in Juragua, once in operation. Cuba
is not technically or economically prepared to dispose safely of the nuclear
waste.
The Juragua nuclear plant should not be permitted to start
operation under the present design and construction deficiencies.
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