MANUEL CEREIJO

INTRODUCTION

Natural uranium- uranium that contains 99.3% of the isotope uranium-238 and 0.7 % of the fissionable isotope uranium-235

Low enriched uranium- uranium that contains the isotope uranium 235 in a concentration less than 20% and higher than 0.7%. Most commercial reactor fuel has been enriched to 3-5% of uranium 235

Highly enriched uranium- uranium that contains the isotope uranium-235 in a concentration above 20%. Highly enriched uranium is used in research reactors, naval propulsion reactors, and weapons.

Depleted uranium-uranium with less than 0.7% of the isotope uranium-235

What is Uranium enrichment?

Uranium enrichment is a critical step in transforming natural uranium into nuclear fuel or weapon grade uranium. Enrichment is the process of increasing the concentration of uranium 235 while decreasing the concentration of uranium 238.

Aluminum-clad cylinders or rods are essential in the production of enriched uranium.

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.

Since the early 1980s, Cuba started an intensive search for atomic minerals in its territory. The objective was to provide these materials to the nuclear industry of Cuba. The department is the DMBA, Departamento de Materiales Basicos. The department found uranium at the Northwest of Pinar del Rio, called the Hierro-Mantua ore.

Later, in the early 1990s, Cuba was able to obtain Yellow Kake (55% U308). One of the two experimental nuclear reactors in Cuba is located at the CIN, Centro de Investigaciones Nucleares, of Pedro Pi, Southwest of La Habana. This reactor is capable of converting U238 to Uranium 235 or Plutonium 239, basic primary components of an atomic bomb.

There are reports that the Soviet Union delivered in 1991, 70 pounds of enriched uranium to Cuba for the Juragua reactor. This amount is sufficient to build 5 atomic bombs.

Due to international regulations, Iran cannot purchased aluminum clad rods in the world market. Neither has Iran the manufacturing facilities in place to produce them. However, Cuba does.

Cuba has a large manufacturing plant-Planta Mecanica- that has the capacity, technology, and raw material to manufacture these kind of specialized aluminum rods, so much needed by Iraq to develop its nuclear weapon capabilities. Fuel element assemblies methods include welding, swaging, pinning, including box-type elements and cylindrical element assemblies.

Planta Mecanica is located north and west of the city of Santa Clara, in the center of Cuba. For the last few years its production has been dedicated to specialized needs for the biotechnology industry, as well as the nuclear related industry. Planta Mecanica has been a key factor in the development of Cuba’s biotechnology industry, as well as in assisting Iran with the equipment and machinery needed to develop its biotechnology industry, and that Iran cannot purchase in the world market.

For the last two years, a large part of Planta Mecanica production facilities has been dedicated to produce aluminum rods.

Cuba and Venezuela have started cooperation in nuclear development. Venezuela is about to purchase a 27 Mwatts reactor from Argentina. Cuba has sent to Venezuela nuclear engineers and physicists, to assist in the development of an infrastructute on nuclear power.

This new incursion on the nuclear development is a real threat for the security, not only of the United States, but all Latin America.

 
NUCLEAR REACTOR PURCHASED BY VENEZUELA

CUBA: JURAGUA EXPERIENCE

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.

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:

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.

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.

Conclusion