Nuclear Power Reactors example essay topic

O n April 26, 1986, a hellish white glow bejeweled a small, little-known town in central Ukraine, now notoriously recognized by the international community as Chernobyl. During the early morning hours of the twenty-sixth, operators had been running an ill-conceived experiment on reactor unit number four, during which a spike in the operating level of the core caused a catastrophic explosion. The resulting eruption of radionuclides, both from the initial explosion and from the subsequent fires, turned much of the Ukrainian countryside into a radioactive wasteland. Furthermore, prevailing winds blew radioactive clouds of particles over a large swath of Europe, irradiating many countries and endangering the overall food supply of the entire continent. Examining both short-term hazards, and long-term effects, many in the scientific community have proclaimed Chernobyl the worst environmental disaster ever (Read 66-73). It is the purpose of this paper to fully investigate every aspect of this colossal crisis.

How bad was the accident What caused it and how was it fixed Finally, and most importantly, can humanity learn from its mistakes and prevent further such mishaps The Accident Situated 65 miles north of Kiev in Ukraine next to the small town of Pripyat, the Chernobyl power station included four reactors, each with an estimated output of a thousand megawatts. Unbeknownst to the nearby residents, a dangerous experiment was conducted on reactor unit four during the early morning of April 26, 1986. Unfortunately, the Chernobyl operators breached numerous safety protocols in order to continue with their endeavor that hinted at disaster from the very beginning (Martin 16-19). At approximately 1: 23 AM on April 26, operators within the Chernobyl complex heard numerous thuds emanating from deep inside the reactor building. These ominous sounds were shortly followed by a horrifically sickening crash and an explosion whic ripped through the reactor complex and buckled the meter thick concrete walls of the containment building.

Emergency power units kicked on, revealing a dimly lit control room sparsely inhabited by frantic plant operators. Though nobody had a clear idea of the extent of the situation, foremost on everyone's mind was preventing a core meltdown. Numb with horror, Alexander Asimov, in command of the night reactor shift, watched as his corridors filled with dust and smoke, trapping men and machine in a furious inferno (Read 64-66). Those looking at the complex from the outside noticed a strange ghastly white glow, as did those looking down into the empty crater where the reactor core lay completely fragmented. Sparks eerily crisscrossed the morning air as electrical systems short-circuited, while operators-realizing for the first time the severity of the accident-frantically attempted to gain control over the situation.

Burst pipes allowed superheated steam to escape from many unpredictable points, scalding many workers who were attempting to fight the numerous graphite and electrical fires now raging like an uncontrollable beast throughout the building. Some of these workers stumbled about the plant, blisters covering every exposed patch of skin on their bodies, vainly trying to reach the apparent safety of the outdoors (Read 66-73). It was determined afterward that thirty-two firefighters and plant operators had been killed in the first few days of the Chernobyl tragedy. Worse yet, debris from the shattered reactor core, coupled with the burning graphite piles, released several times the amount of radiation discharged when the United States dropped both atomic bombs on the Japanese cities of Hiroshima and Nagasaki ("The Causes of the Accident and Its Progress" 1-2). Because of the general lack of radiation monitoring equipment, the Soviet government learned the true extent of the accident only after Swedish personnel working at nuclear power plants in Sweden began to notice elevated levels of radioactivity (Martin 19). Tragically, much of the radioactive material blown into the atmosphere was carried by the wind into the surrounding countryside, as well as distant republics.

Forests surrounding Chernobyl turned a rust color as a result of high levels of radioactive contamination. However, about seventy percent of the fallout ended up contaminating the republic of Byelorussian, endangering its water and food supplies while causing an increase in the number of reported cancer cases and deaths ("Belarus"). Nearby, in the city of Kiev, the radiation level peaked at an increase of 160 to 300 times what could be expected from normal background radiation. To give some appreciation of the extent of the environmental damage caused by the release of radioactive isotopes from Chernobyl, the Swiss government banned fishing in certain lakes for nearly a year after the explosion due to high concentrations of the radioisotope Cesium-137 in aquatic life. Chernobyl also takes blame for an incredible increase in the amount of radiation absorbed by livestock and agricultural products scattered over Europe, especially within the Scandinavian countries. For instance, because of excessive levels of radiation, about seventy-five percent of the reindeer slaughtered in Sweden could not be consumed by humans (Marples 61-77).

However horrible the environmental impact of radiation may seem, it is nothing compared to the individual tragedies experienced by people who were seriously radiated. Soviet doctors described the following at a meeting in Paris on "The Medical Handling of Skin Lesions following High Level Accidental Irradiation" in 1987: Male plant worker who received an estimated average total body dose of 9 Gy... He developed skin lesions from 5 days of irradiation, eventually involving 40% of the body surface area. He showed epilation of the scalp and eyelashes, but the eyebrows were not affected.

Lesions were severe over both buttocks as a result of his sitting on a contaminated surface. These areas of skin developed blisters and foci of ulceration, which required covering with free skin grafts taken from the patient's flak 2 months after the accident. (Mould 69) Many pregnant women who were exposed to radiation had abortions for fear of having offspring with serious physical defects or mental retardation. Lending some justification to these abortions, the U.S. Nuclear Regulatory Commission estimated that approximately five percent of the fetuses exposed to at least twelve rems-a measurement of the amount of ionizing radiation absorbed by body tissues ("Rem") -from Chernobyl would be born with serious mental retardation (Marples 43-44).

Some of the mutations caused by radiation were to prove both shocking and frightening to those who lived in the most heavily contaminated zones: "To the horror of the inhabitants, a sow in Narodici gave birth to a litter of piglets without eyes. News of this spread and further freaks were discovered in the same region: a foal with eight legs, a chicken with a head shaped like a dragon's, a piglet with an eye half the size of its head, a calf with a lip like an elephant's trunk, and a goat with its hind legs three times longer than its front ones" (Read 270). While scientists are sure that there will be many long-term deaths attributable to the exposure of people to radiation from the Chernobyl accident, many scientists are in serious disagreement as to the number of deaths and the severity of other long-term problems. Currently, scientists estimate that in the next seventy years, between 200 and 100,000 people will die because of radiation exposure to the fallout from the Chernobyl disaster. While this range is huge, most experts agree that the eventual number will finalize at about 10,000 deaths, mostly occurring because of an increase in leukemia cases in those areas most heavily radiated (Marples 52-53). Causes of Chernobyl The accident at Chernobyl has sparked much criticism about the safety of nuclear energy, while raising fears about nuclear power plants in the United States and other Western nations.

In the decade following the disaster, images of badly scarred workers and horrifically deformed animals gradually found their way into the hands of the media (Read 270). Thus, people throughout the globe began to question whether or not an accident on the scale of Chernobyl could happen at home (Goldin 20). Central to formulating a reasonable answer to this question is an in-depth understanding of how and why the situation in central Ukraine unfolded as it did; consequently, this section is dedicated to documenting the sequence of events that contributed to the cataclysmic accident at the Chernobyl plant. In 1949, Igor Kurchatov-already a prominent Soviet scientist-petitioned Joseph Stalin for permission to build an experimental nuclear power station using knowledge gained from captured German physicists.

With permission given, the first nuclear power station in the world was commissioned on July 27, 1954, and christened Obninsk. An early design, this power station produced a mere five megawatts of electricity, not even enough to provide for the electrical needs of the actual power complex. Therefore, when American designers began working on new pressurized water reactors, the Soviet Union immediately began similar work on a new power station in hopes of implementing the practical use of atomic fission to fulfill the country's burgeoning need for electrical energy. Design and building of this new power station was problematic at best, mainly due to deficiencies in quality control. Thus, when the Soviet Union later resolved to greatly expand its use of nuclear fission, experts decided that the safest, surest reactor design would be a large modified version of the early Obninsk reactor (Read 3-15).

Construction of several new RBMK-1000 reactors commenced immediately. Roughly translated, the acronym RBMK means "reactor cooled by water and modified by graphite" (Marples 3). Basically, a RBMK reactor is a huge stack of graphite with several hundred channels drilled vertically through the carbon matrix. Some of these channels contain boron rods; boron is an excellent neutron absorber which serves as a control mechanism for the reactor.

The rest of the channels contain small pipes-or pressure tubes-each of which contain thousands of enriched uranium pellets which undergo nuclear fission. Huge circulation pumps flush water through the tubes and over the uranium; this water serves as a thermal transfer medium, absorbing the heat from the nuclear fission of the uranium pellets, both to keep the core from melting and to provide steam to spin electricity producing turbines. However, as the graphite moderator is placed next to the uranium fuel elements, about five percent of the thermal energy released by the uranium is transferred to the graphite. This means that the graphite in RBMK reactors routinely functions at temperatures exceeding 700 Celsius, emitting a faint reddish glow. Unfortunately, graphite has the nasty tendency to burn at high temperatures when exposed to oxygen, so the entire core must be placed into a huge metal container where inert gases are constantly circulated (Marples 4-8).

While at first glance the RBMK may have seemed to be a safe alternative to more advanced pressurized water-cooled reactors, upon further inspection several major flaws became apparent. The British atomic Energy Authority released a list of seven reasons why RBMK reactors would not be licensed within the United Kingdom. Paramount on this list was the lack of a containment structure to provide protection in the event of a meltdown. Soviet designers felt that there was no need to provide a massive containment structure to protect against an apparently highly unlikely failure. Another major flaw of the reactor was that, in the event of an accident, it took a full eighteen seconds to lower the boron control rods into the graphite pile, an eternity in the world of nuclear reactions (Read 15).

Compounding the above design problems was the haste with which the Soviet Union built its nuclear power capacity. Because of the rapid expansion of its nuclear program, there were frequent shortages in precision parts needed in the construction of the nuclear power plants-including the Chernobyl plant. However, there was enormous pressure on those responsible for the construction of power plants to get the reactors producing electricity quickly. Thus, many components were built and improvised at the building site. Considering that piping and valve components must be assembled with extreme precision, it is unlikely that all of these make-shift components met even lenient Soviet safety standards (Read 30-31). The RBMK was the type of reactor chosen to power the new, enormous power-producing complex situated at Chernobyl.

Conceived in the late 1960's as the solution to energy shortages in the Eastern part of the Soviet Union, Chernobyl was to eventually accommodate six one-thousand megawatt RBMK reactors (Read 28-35). When the Chernobyl plant finally became operational in December 1978, several major difficulties were noticed in the operation of the huge RBMK reactors. First, the reactors tended to be highly unstable when run at low power settings. Under these circumstances, power could completely collapse within the reactor, necessitating lengthy restart procedures. Thus, when a collapse appeared imminent, operators frequently withdrew many more boron rods than was permitted by Soviet regulations, simply to give the reactor a surge of power to prevent shutdown. Second, the primitive computer used to process information and monitor reactor systems printed out incredibly complex, cryptic information, not easily understood by human operators.

This would pose problems in the event of a crisis, when information must be interpreted quickly and accurately. Finally, operators at the plant had to monitor a myriad of dials and switches, making it difficult for them to understand completely what the reactor was doing at all times, crucial knowledge in the event of an accident (Read 41-42). Besides the physical problems that hampered the RBMK reactors used at the Chernobyl plant, the mind-set of Soviet officials was such that information on past problems was withheld even from operators who could benefit from this information. To these officials, Soviet technology was infallible and the few problems that surfaced in the reactors could not possibly be due to faulty design. For instance, there was a meltdown within a reactor at a plant in Leningrad (now St. Petersburg).

Although this reactor was identical to the RBMK reactors used in the Chernobyl plant, Soviet officials did not see fit to warn the Chernobyl plant of a potential problem, fearing that this information might undermine the Soviet nuclear industry (Read 39-40). Despite the design failings of the RBMK reactors, an accident may never have occurred at Chernobyl had operators not attempted a foolishly designed experiment ("The Causes of the Accident and Its Progress"). Attempting to ascertain the length of time that inertia would keep the turbines spinning in the event that the reactors had to be shut down, operators gradually began decreasing the power output of reactor number four at 1: 05 on April 25, 1986 (Martin 16-19). However, unexpected demand for power forced operators to maintain the reactor at about fifty percent power for an additional nine hours. When the experiment finally resumed at 12: 28 AM, April 26, operators further reduced the power, accidentally reducing the reactor to one percent operating power. The RBMK reactor became unstable as xenon gas-a neutron absorber-formed in the core.

To prevent the reactor from completely shutting down, operators withdrew virtually all of the boron control rods between 1: 00 and 1: 20 AM, allowing power to rise to about seven percent. Afraid that the automatic shutdown systems would SCRAM-or immediately shut down-the reactor, plant operators flipped off the emergency shutdown systems. At 1: 23, steam was shunted to a previously idle turbine; at 1: 23: 40, power increased in the reactor as water began to flow more quickly over the fuel elements. As one Soviet expert explained, "The reactor was now running free, isolated from the outside world, its control rods out, and its safety system disconnected... The reactor was free to do as it wished" (Martin 17). The next events occurred very quickly as operators pressed the manual shutdown button-drastically reducing water flow over the fuel elements-to examine how long inertia would keep the turbines spinning and producing power.

Had the emergency systems been connected, the loss of the electrical load would have caused the reactor to SCRAM (Martin 17). However, all automatic emergency systems were off-line, and at this low power setting shutting off the turbines caused the RBMK reactor to spike at about 100 times its full operating power (Marples 14). Predictably, the reactor core shattered, spewing pieces of radioactive graphite and uranium throughout the destroyed reactor building and over the Ukrainian countryside. The hot graphite of the core-no longer isolated from oxygen-began to smolder, releasing tons of radioactive material, which was trapped within its carbon matrix mostly iodine-131 and cesium-137, into the atmosphere. (General Accounting Office 8). While the faulty experiment on the day of April 26 was the precipitating causal factor in the catastrophic destruction of reactor number four at the Chernobyl complex, faulty engineering and design problems with the RBMK reactor played major contributing roles.

However, the most significant contributing factor seems to have been a complacency of mind: a psychological phenomenon that seems to recur. For example, those who built the Titanic never imagined that this great ship could sink; hence, the lack of lifeboats onboard became a major factor in one of the worst tragedies of all time. In much the same way, Soviet designers never thought that their designs could fail. Thus, they did not see fit to build elaborate containment structures around their RBMK reactors. Also, test operators at Chernobyl never thought that their program could cause any real damage. For that reason, they proceeded even when problems immediately became apparent.

Catastrophes such as Chernobyl are rarely caused by a single event or problem; rather, they are usually the culmination of a string of circumstances which together point to disaster. Interests and Tradeoffs Throughout the course of human events, many mammoth projects have been undertaken for the benefit of society. However, frequently the same projects that are highly beneficial to large populations when successful are incredibly detrimental to a localized group when they fail. Chernobyl is an outstanding example of this interesting-and tragic-phenomenon. Its construction initially benefited many thousands of people in the eastern section of the Soviet Union.

Conversely, while its failure caused problems for many people, these problems were mainly focused on the relatively small population living in the countryside surrounding the reactor itself. This is an extreme example of the "Tragedy of the Commons": those receiving power from Chernobyl on average-had much more to gain from Chernobyl's construction than they stood to lose if something were to go awry; the risk population was much smaller than the benefiting population (Hardin 507). Because of the enormous complexity of this situation, it must be examined from a number of different and competing views. But, before the actual interests and tradeoffs involving Chernobyl are discussed, a little must be said about the initial development of the Soviet nuclear industry. Sadly, when the Soviet nuclear energy program was in its infancy, the main debate focusing on nuclear power revolved around the issue of money, not safety. Other factors, such as state secrecy and a sense of nationalism, were also placed above safety when the Soviet Empire erected its national nuclear program.

In particular, this sense of secrecy and nationalism caused many prominent Soviet leaders to ignore problems internal to the nuclear industry. For example: When the benefits of nuclear energy were being discussed by the Soviet Central Committee, members of the military establishment had information about a catastrophic accident at May ak-a small experimental reactor initially built to produce plutonium for nuclear weapons. However, the Central Committee felt that this failure was in no way due to problems in the reactor design itself, and that the important thing was to learn about the effects of massive doses of radiation on the human body. Thus, this extremely important issue was not even considered by those who could have steered Soviet nuclear industry in a different direction. Considering this information from a traditional Western slant on the value of human life, one must remember that the Soviet nuclear program was developed during the most intense period of the Cold War, when Soviet leadership was convinced that an atomic war was inevitable and that knowledge about radiation could allow Soviet society to weather a nuclear holocaust. Sadly, these views and attitudes fostered a rather lackadaisical approach to atomic safety among those of rank and stature in the Soviet government.

Why spend massive amounts of money on public safety if society is expected to be destroyed anyway (Read 10-11) Ranking monetary costs higher than atomic safety is one tradeoff that directly fueled the Chernobyl disaster. However, without the rising social pressures demanding energy, this lack of safety might never have had the chance to cause a major accident. It is this very craving for energy that has become the ultimate tradeoff in modern society; people want all the "goodies" that have been developed because of technology: electric stoves, air conditioning, computers, toasters, television, etc. Thus, developed nations are increasingly being forced to develop new sources of energy and implement them with an insufficient regard for proper testing.

When Soviet planners in the late 1960's decided to erect the huge Chernobyl power plant, their training did not tell them that RBMK reactors were inherently unsafe. Instead, they studied projections of power consumption by those living in the western part of the Soviet Empire; according to the Ukraine Department of Energy, consumption of electricity would triple by the year 1990 ("The Chernobyl Nuclear Power Plant: Design and Construction"). Consequently, the decision to build a new power plant was easy; the only questions involved were where it was to be built and what type would best suit the needs of Soviet society. At this point, one may ask: Why did the Soviet Union wish to fabricate nuclear power plants when they had huge reserves of natural gas and coal in eastern Siberia This question has no quick easy answer, but there appears to have been two major factors. First, the Soviet government was obsessed with staying in the forefront of nuclear technology. Western nations had already demonstrated the ability to build Pressurized Water Cooled Reactors far in advance of what Soviet technology could perform, and this made the Soviet government wary about delaying future production of nuclear power plants.

Second, most of the energy boom in the Soviet Union was occurring on the European side of the Empire while most of the resources were thousands of miles away in eastern Siberia. Because the density of energy obtained from nuclear fuel is thousands of times higher than that obtained from the best chemical processes, it was cheaper to transport small quantities of uranium ore thousands of miles than to send vast quantities of coal and natural gas ("Siberia"). This must be qualified with the fact that nuclear power plants are generally more expensive to run than conventional ones; but Soviet planners were betting that gradual improvements in nuclear technology would eventually allow it to shoulder the majority of electric production within the country (Read 10). Because Soviet technology generally lagged behind that of Western nations throughout the Cold War, attempted duplications of advanced American Pressurized Water Cooled Reactors failed. What was needed was a quick way to expand massively the production of electricity within the vast area of the Soviet Union (Read 9-10). An easy answer came in the RBMK reactor.

Because this reactor does not use a secondary thermal transfer loop to drive steam generators, Soviet officials felt that the massive containment structure needed for other nuclear reactor types was not needed in an RBMK. This would save money in two ways: first, the overall reactor would have a higher efficiency, using less uranium fuel per kilowatt hour of electricity produced; second, expenditures on building a massive steel and concrete containment structure could be eliminated. In this way, Soviet designers minimized costs at the expense of safety precautions (Read 15). Obviously, electricity generated by Chernobyl benefited thousands of people spread over the eastern sector of the Soviet Union. However, the cost of the tragic accident has been much more highly concentrated among those in a small geographical area.

In the case of Chernobyl, the Republic of Belarus and the Scandinavian countries-coupled with other European nations-took a large share of the released radiation. This tends to lead one to believe that the effects of this accident were spread over a vast area. But, this ignores the larger picture: while these other nations did absorb large quantities of radiation, the radionuclides that managed to travel such a distance from Chernobyl were mostly short-lived isotopes of cesium and iodine. In contrast, much of the radioactive particles spread over Pripyat and the immediate countryside near Chernobyl were heavier, longer-lived particles such as Uranium and Thorium. Thus, long after other European nations have healed from the harsh effects of radiation, Northern Ukraine will still be uninhabitable, unable to shake the lingering effects of radiation imposed upon it by Chernobyl (Marples 61-77). When examining the Chernobyl incident, it must be remembered that Chernobyl was an accident in the truest sense, for the fact remains that except for an unfortunate test run on the reactor, this nuclear tragedy may well have never occurred.

Thus, the costs and tradeoffs so far discussed cannot be viewed as results of decisions made by society to gain something at the expense of something else. Instead, the rather lax safety precautions undertaken in the Soviet nuclear industry must be considered in terms of the rather extreme set of circumstances created by Chernobyl operators that caused the accident. Soviet engineers might well have been right in their assessment that further shielding of the reactor was unnecessary; however, they were catastrophically wrong in their choice of personnel to run the reactor on a day to day basis ("The Causes of the Accident and Its Progress"). The only aspect of Chernobyl where traditional costs and tradeoffs can be examined involves the immediate aftermath of the disaster, when the Soviet bureaucracy consistently slowed down efforts to contain the problem.

When dispatched, Boris Scherbina, the minister responsible for fuel and energy within the Soviet Union, was faced with the crucial decision of evacuating the nearby town of Pripyat or trusting to the unpredictable Ukrainian winds. The physicists advising him favored immediate and complete evacuation of the town's fifty thousand members. However, Scherbina was worried that such a large evacuation could not be concealed from the rest of the Soviet population. Though the media could have been controlled, when rumors reached Kiev about the Chernobyl disaster, there might have been a mass exodus of over three million people, causing panic and unrest in one of the Soviet Union's largest cities. This would severely affect the international prestige of the Soviet Union, something that had to be protected at all costs according to Party indoctrination.

Finally, more than thirty-six hours after the initial disaster, Scherbina decided that evacuating Pripyat was the right course of action. Sadly, had this order been given immediately, many people would not have been needlessly exposed to radiation; saving thousands of potential cancer cases (Read 100-110). Solutions Attempted at Chernobyl and Recommendations for the Future The Chernobyl accident has been an eye opener in many respects. Not only did it force the international community to more closely scrutinize the nuclear industry, but it created a testing ground for untried techniques and equipment used to combat nuclear accidents. For the first time since Hiroshima and Nagasaki, the world would be confronted with the hellish images of radiated men, women, and children, living in a manmade radioactive wasteland. Globally, governments and high public officials wondered how the Soviet bureaucracy would react to the situation.

Simultaneously, people across the planet wondered what could be done to ensure that an accident of this magnitude would never occur again. The purpose of this section is both to detail the Soviet response to Chernobyl and to suggest possible actions that could be taken to prevent further nuclear catastrophes. Members of the fire station assigned to the Chernobyl power station were awakened at 1: 23 a.m. on the morning of April 26, 1986, by the sickening sound of the fourth unit reactor core exploding. When the commanding officer of the fire station ran outside, he was immediately besieged with an apocalyptic sight of the shattered reactor burning in the distance. Before thinking, he immediately ordered his men to combat the raging fire that now consumed the entire reactor unit. His immediate concern was the roof which joined reactor complex four to reactor complex three.

Obviously, the worst thing that could happen would to have the fire spread to the other reactors, possibly turning a horrible situation into something far worse. However, as the heroic firefighters battled the fires on the roof without radiation suits, not only did they have little success, but they began to feel giddy and weak, the first symptoms of severe radiation sickness. By 4: 00 a.m. the same morning, additional firefighters arrived on the scene; finally, they began to have some success combating the hellish fires which were releasing tons of radioactive material into the atmosphere every hour (Read 74-75). While the firefighters risked life and limb to combat a situation that they neither started nor could comprehend, plant operators-for the first time fully understanding the severity of the accident-frantically worked to drain hydrogen gas from the turbines in order to prevent further explosions. The other three reactors were then systematically shutdown to lessen the chance that another reactor would develop catastrophic problems due to the spreading fires. Meanwhile, Boris Scherbina, wrestled with the question of evacuating Pripyat.

The Ministry of Health concluded that evacuation was unnecessary; however, the scientists advising Scherbina argued that the safest, surest course of action was evacuation. Fearing the political and international repercussions of a general evacuation, Scherbina stalled, wasting precious time that could have prevented the needless exposure of thousands of citizens to unnecessary levels of radiation (Read 100-104). By 5: 00 p.m. April 26, all the fires-except for the fire raging in the reactor hall-were extinguished. Scherbina, who was visiting the Chernobyl site to get a firsthand view of the disaster, was faced with another decision: Allow the graphite in the reactor core to burn out, or devise some ingenious method of extinguishing it.

Advised both that it would take nearly two months for the graphite in the core to burn out, and that the uranium fuel left in reactor core could melt if the temperature rose too much, Scherbina decided that some way would have to be found to manually extinguish the fire. Water would have proved counterproductive; at the temperature that the reactor was burning, water would decompose into its component elements of hydrogen and oxygen, an explosive combination. The only method that the Soviet scientists could devise was to drop massive quantities of sand into the reactor building from hovering helicopters. The sand was laced with a mixture of boron, lead, and dolomite. The lead was used to cool the core because it has a boiling point of 1,744 C (a substance absorbs a great deal of energy during a change of state reaction). The dolomite broke down into magnesium, calcium and carbon dioxide, which further absorbed heat; furthermore, the carbon dioxide helped prevent oxygen from reaching the fire.

Finally, boron is an outstanding neutron absorber and its purpose was to stop any lingering fission occurring within the core (Read 106). This process seemed to worked; however, it was necessary to drop sand into the reactor for more than a month to ensure that the fire would not restart. In all, some 5000 tons of various substances were dropped into the disintegrated reactor core before helicopter operations were terminated ("The Cause of the Accident and Its Progress"). Finally, at 10: 00 a. m., April 27, Scherbina ordered a general evacuation of the town of Pripyat. Families were told to pack enough clothes and supplies to last three days; most administrators at this time thought the evacuation would be temporary. Those people fortunate enough to be forewarned by family or friends working at Chernobyl had time to pack suitcases; others were forced to leave virtually all of their possessions behind.

Because of the marvelous leadership skills of the army commander in charge of evacuation, General Ber dov, the town was completely evacuated within two hours (Read 110-112). By May 1, the reactor situation appeared to be under control. However, just when Soviet officials felt certain that the core would completely stabilize, radionuclides emanating from the reactor began to radically increase; the reactor was getting hotter, not cooler. Now Soviet scientists began to question the whole premise of dropping sand on the damaged reactor. Uranium does not need oxygen to undergo a chain reaction; also, with every load of sand dropped on the reactor, a large number of radioactive particles was thrown into the air. Furthermore, because sand is a good insulator, it was trapping the heat from the uranium in the core, the exact area that had to be kept cool.

Worse yet, underneath the shattered reactor core was a concrete base, situated just above a bubbler pool of water. If the uranium burned through the concrete, it would react with the water, turning it into hydrogen and oxygen which would promptly detonate with horrific results. Unfortunately, the water could only be drained through gate valves located at the bottom of the pool. Two brave engineers volunteered to dive to the bottom and open the flood gates; they succeeded despite great risk to personal health (Read 132-135). Though the bubbler pool was empty, more water was situated in the basement of the reactor building, poured there when operators tried to cool a non-existent reactor in the opening minutes of the accident.

A group of firefighters volunteered to run large hoses into the basement, which could be used to drain this dangerous amount of water. By May 7, all of this water was completely drained, eliminating the immediate concern of a catastrophic explosion which could destroy the other Chernobyl reactor units (Read 135-137). At this point, there was little chance that the reactor would disastrously explode again. Attention now turned to long-term containment of the radioactive wastes produced by the Chernobyl accident. Highly radioactive debris was buried in over 800 temporary burial sites, diminishing the immediate risk to the population of Ukraine, but potentially endangering future generations and the long term health of underground aqueducts. By the end of 1986, the extremely radioactive reactor core was encased in a large concrete-and-steel "sarcophagus" ("Chernobyl Accident").

This sarcophagus was built-using the remaining structural components of the unit four building for support-as a series of rising sections completely enclosing the reactor area. In addition, a huge concrete partition was erected to separate the unit four building from the adjacent unit three complex. Finally, over three hundred sensor devices have been embedded in the entombed reactor to monitor internal temperature and radiation levels ("Nuclear Power" 73-75). After the Chernobyl disaster, the international community became increasingly concerned with older "Soviet-designed nuclear power reactors operating without basic safety features such as emergency core cooling systems, protective structures to contain radioactive releases in the event of an accident, and skilled personnel" (GAO / N 8 IAD-92-28 4). Chernobyl has increased international debate about making the International Atomic Energy Agency's standards of safety mandatory for all nuclear powers.

However, as most nations-including the United States-do not want national sovereignty infringed by international organizations, adoption of new standards and their enforcement have been severely limited (GAO / N 8 IAD-92-28 4). While several measures have been devised to clean-up the immediate effects following the Chernobyl disaster, the most important issue-that of ensuring safe nuclear power for the future-has yet to be addressed. Nuclear power advocates must realize that another Chernobyl disaster may be the total death knell for practical uses of nuclear energy for at least the next generation. Therefore, engineers, scientists, and politicians must ensure that all new nuclear reactors meet highly stringent safety requirements, while old, obsolescent reactors are quickly and systematically retired from active service. As the scientific community has come to a general consensus that the world will soon be plagued with acute fossil fuel shortages, the most immediate solutions appear to lie with nuclear power. Ironically, the most long-term solution to the energy needs of the world also appear to lie with an advanced yet highly different form of nuclear energy.

In the next section, a few of the most promising nuclear technologies will be mentioned. One of the most promising nuclear technologies that could be implemented almost immediately is the so-called "inherently safe" nuclear reactor. In this type of reactor, the core is built below the ground, next to a large source of water. Therefore, if an accident were to occur, the core could instantly be flooded, preventing a Chernobyl-type explosion or a Three Mile Island type meltdown. Also, a reactor of this type would use negative power-reactivity feedbacks to keep it working in normal operating parameters. This means that if there were a leak in the reactor, the loss of water would cause fewer neutrons to be absorbed by the fuel elements, causing the overall power output of the reactor to reduce.

In this way, as coolant decreases, the power output of the reactor automatically adjusts to a safe level. This contrasts with the positive power-reactivity feedback systems in the RBMK reactor type used at the Chernobyl plant. When the plant began to lose coolant, it increased power, causing a massive and uncontrollable explosion ("Energy Conversion"). The energy that powers the sun is the ultimate goal for nuclear physics: fusion. In a nuclear fusion reactor, two light elements-usually two different forms of hydrogen, deuterium and tritium-are combined to form a single, heavier element.

In the process, however, some of the mass of each light particle is directly converted to energy. Because matter contains so much energy per unit of mass, a self-sustained nuclear fusion reactor would provide mankind with a virtually limitless supply of energy. Moreover, hydrogen the most likely candidate to power a fusion reactor is the most abundant element in the universe and is readily available for a nuclear reactor. However, a self-sustained fusion reaction has proven extremely difficult, mainly because fusion requires that a plasma of several hundred million degrees Celsius be held at a distance away from the reactor walls at a density sufficient to allow the plasma to be self-sustaining. In other words, the plasma must have enough average transitional kinetic energy to kindle a fusion reaction in particles ejected sometime after the initial ignition. Fusion has been successfully demonstrated in the laboratory despite the fact that it currently takes more energy to start fusion than can be obtained from the short pulses the reactors operate in (Knie f 506-510).

Conclusion In this incredible era of expanding knowledge and technology, man has been blessed with the power to create and destroy with unbelievable efficiency and ruthlessness. But with power comes responsibility, a responsibility all too neglected by even the most astute and learned within society. Because disasters such as Chernobyl are the pinnacle of long chains of carelessness, they serve to highlight this neglect and show how apparently infallible technologies can go disastrously wrong. Though Chernobyl was a tragedy in the worst sense, it forced a complete reevaluation of the nuclear industry and may prevent further such accidents. However, history has shown time and time again that man has an incredibly short memory and usually reverts back to old-habits, regardless of the cost.

It can only be hoped that the next century will be dominated by people of vision; those who would dare to dream the impossible, and then make it reality. These people must embrace nuclear fusion as the only energy source capable of providing humanity with a long term solution to its energy requirements. The old fears, hatreds, and ignorance of nuclear power must be erased, paving the way for a future dominated by this clean, awe-inspiring source of energy 31 a.