Visual History of the World

(CONTENTS)
 

 


HISTORY OF CIVILIZATION & CULTURE

From Prehistoric to Romanesque  Art
Gothic Art
Renaissance  Art
Baroque and Rococo Art
The Art of Asia
Neoclassicism, Romanticism  Art
Art Styles in 19th century
Art of the 20th century
Artists that Changed the World
Design and Posters
Photography
Classical Music
Literature and Philosophy

Visual History of the World
Prehistory
First Empires
The Ancient World
The Middle Ages
The Early Modern Period
The Modern Era
The World Wars and Interwar Period
The Contemporary World

Dictionary of Art and Artists

 



The Contemporary World

1945 to the present



After World War II, a new world order came into being in which two superpowers, the United States and the Soviet Union, played the leading roles. Their ideological differences led to the arms race of the Cold War and fears of a global nuclear conflict. The rest of the world was also drawn into the bipolar bloc system, and very few nations were able to remain truly non-aligned. The East-West conflict came to an end in 1990 with the collapse of the Soviet Union and the consequent downfall of the Eastern Bloc. Since that time, the world has been driven by the globalization of worldwide economic and political systems. The world has, however, remained divided: The rich nations of Europe, North America, and East Asia stand in contrast to the developing nations of the Third World.




The first moon landing made science-fiction dreams reality in the year 1969.
Space technology has made considerable progress as the search for new
possibilities of using space continues.

 

 


The Soviet Union and its Successor
States
 


SINCE 1945
 

 


see also: United Nations member states -
Russian Federation,
Ukraine,Belarus, Moldova,
Armenia, Azerbaijan, Georgia,
Estonia, Latvia, Lithuania,
Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan

 

After the Second World War, all of Eastern Europe came under the influence of Stalin's totalitarian system, which led the Soviet Union into the Cold War. The system was relaxed to a degree under his successors, who were increasingly bound to a "collective leadership." The party's claim to autocratic rule was not seriously questioned until Gorbachev. In the turbulent years of 1989-1991, the structure of the Eastern bloc crumbled, and then the Soviet Union itself collapsed, disintegrating into a federation of autonomous states. While the Central European countries sought bonds with Western Europe, autocratic presidential regimes established themselves in most of the former Soviet republics.

 


Gorbachev and the End of the Soviet Union
 

In 1985, a radical change in direction took place with the election of Gorbachev as general secretary. His reforms led to the collapse of Soviet Communism between 1989 and 1991.

 

   

Between Khruschev and Gorbachov:

Brezhnev's funeral:


Leonid Brezhnev, Yuri Andropov and Konstantin Chernenko
at a brunch sometimes in 1981
 


Leading representatives of the Soviet party
and government carry his open coffin, November 15, 1982

 

Following 9 Brezhnev's death, first 11 Yuri Andropov in 1982 and then 13 Konstantin Chernenko in 1984 took turns to hold power.
 

   

9. Leonid Ilyich Brezhnev (Russian: ́ ́ ́​ (helpinfo), Ukainian: ́ ́ ́), 19 December 1906 [O.S. 6 December 1906] 10 November 1982) was General Secretary of the Communist Party of the Soviet Union (and thus political leader of the Soviet Union) from 1964 to 1982, serving in that position longer than anyone except Joseph Stalin. He was twice Chairman of the Presidium of the Supreme Soviet (head of state), from 7 May 1960 to 15 July 1964, then from 16 June 1977 to his death on 10 November 1982.

 

 

11. Yuri Vladimirovich Andropov (Russian: ́ ́ ́, Yuriy Vladimirovich Andropov) (15 June [O.S. 2 June] 1914 9 February 1984) was a Soviet politician and General Secretary of the Communist Party of the Soviet Union from 12 November 1982 until his death fifteen months later.

 

 


 

13. Konstantin Ustinovich Chernenko (Russian: ́ ́ ́, Konstantin Ustinovič Černenko; 24 September 1911 10 March 1985) was a Soviet politician and General Secretary of the Communist Party of the Soviet Union. He led the Soviet Union from 13 February 1984, until his death just thirteen months later on 10 March 1985. Chernenko was also Chairman of the Presidium of the Supreme Soviet from 11 April 1984, until his death.

 

When Chernenko died on March 10,1985, 10 Mikhail Gorbachev was elected general secretary of the Soviet Communist party the next day.


10 Revolution from the top:
Mikhail Gorbachev outlines his
reform plans, involving perestroika
(reconstruction) and glasnost
(openness), to a Communist
party conference, 1988


Step by step, together with Foreign Minister Eduard Shevardnadze and his younger leadership cadre, Gorbachev carried out comprehensive reforms. He renewed the disarmament talks with the United States in Geneva right away and withdrew the Soviet army from Afghanistan in 1987-1989.


A convoy of Soviet Army armoured personnel vehicles crossing a bridge at the Soviet-Afghan
border during the Soviets phased withdrawal from Afghanistan, May 1988;
Mujahideen leader Ismail Khan walks among his fighters.



Domestically, the Soviet leadership began privatizing the economy in 1987 and legally established companies' independence in 1988. However, rapid inflation often impeded the economic reforms. Cultural and educational policies were liberalized with the slogans glasnost (openness) and perestroika (reconstruction), and Western cultural influences flooded the country. Gorbachev's reforms immediately radiated to the allied socialist states, where the people in the countries of Central and Eastern Europe forced the fall of the Berlin Wall in 1989 and the dissolution of the entire Eastern bloc. For his rejection of any form of violent course of action in this process, Gorbachev was awarded the Nobel Peace Prize in 1990.


The Fall of the Berlin Wall


Gorbachev, however, came under increasing internal pressure. The traditional party cadre sabotaged his reform course, while his efforts did not go far enough to satisfy Western-oriented reformers. The catastrophic economic situation led to strikes, and the Soviet Union became increasingly dependent on extensive financial assistance from Western countries.

To make matters worse, in April 1986 the worst nuclear power plant disaster to date occurred in Ukraine when the Chernobyl plant's 12 No. 4 reactor exploded.


12 Damaged reactor at the nuclear power
plant in Chernobyl, 1986


In addition to these problems, separatist conflicts broke out. As early as 1986, unrest began in Kazakhstan. National reform movements and representatives of the people, particularly in the Baltic republics, sought to leave the Soviet Union in 1990.

The same year, the first Russian 14 demonstrations against communist rule took place.

On August 19,1991, conservative hardliners attempted to execute a coup and isolated 15 Gorbachev, who was absent from Moscow.
 


14 Demanding freedom: more than 20,000 citizens demonstrate in Moscow on September 16, 1990


15 Meeting between Mikhail Gorbachev
and US President Ronald Reagan,
December 9, 1987

 


The Chernobyl disaster
 

From Wikipedia, the free encyclopedia
 



The nuclear reactor after the disaster. Reactor 4 (centre). Turbine building (lower left). Reactor 3 (centre right).


Date-
26 April 1986 (1986-04-26)
Time-
01:23 a.m. (UTC+3)
Location-
Pripyat, Ukraine
Casualties-
56 direct deaths
600,000 (est) suffered radiation exposure, which may result in as many as 4,000 cancer deaths over the lifetime of those exposed, in addition to the approximately 100,000 fatal cancers to be expected due to all other causes in this population.


The Chernobyl disaster was a nuclear reactor accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine (then part of the Soviet Union). It is considered to be the worst nuclear power plant disaster in history and the only level 7 event on the International Nuclear Event Scale. It resulted in a severe release of radioactivity following a massive power excursion that destroyed the reactor. Most deaths from the accident were caused by radiation poisoning.

On 26 April 1986 at 01:23 a.m. (UTC+3) reactor number four at the Chernobyl plant, near Pripyat in the Ukrainian Soviet Socialist Republic, exploded. Further explosions and the resulting fire sent a plume of highly radioactive fallout into the atmosphere and over an extensive geographical area. Four hundred times more fallout was released than had been by the atomic bombing of Hiroshima.

The plume drifted over large parts of the western Soviet Union, Eastern Europe, Western Europe, and Northern Europe, with some nuclear rain falling as far away as Ireland. Large areas in Ukraine, Belarus, and Russia were badly contaminated, resulting in the evacuation and resettlement of over 336,000 people. According to official post-Soviet data, about 60% of the radioactive fallout landed in Belarus.

The accident raised concerns about the safety of the Soviet nuclear power industry as well as nuclear power in general, slowing its expansion for a number of years while forcing the Soviet government to become less secretive[citation needed]. The countries of Russia, Ukraine, and Belarus have been burdened with the continuing and substantial decontamination and health care costs of the Chernobyl accident. It is difficult to accurately quantify the number of deaths caused by the events at Chernobyl, as over time it becomes harder to determine whether a death has been caused by exposure to radiation.

The 2005 report prepared by the Chernobyl Forum, led by the International Atomic Energy Agency (IAEA) and World Health Organization (WHO), attributed 56 direct deaths (47 accident workers, and nine children with thyroid cancer), and estimated that there may be 4,000 extra cancer deaths among the approximately 600,000 most highly exposed people.] Although the Chernobyl Exclusion Zone and certain limited areas remain off limits, the majority of affected areas are now considered safe for settlement and economic activity.
 


Location of the Chernobyl Nuclear Power Plant.

The Chernobyl station is near the town of Pripyat, Ukraine, 18 km (11 mi) northwest of the city of Chernobyl, 16 km (10 mi) from the border of Ukraine and Belarus, and about 110 km (68 mi) north of Kiev. The station consisted of four RBMK-1000 nuclear reactors, each capable of producing 1 gigawatt (GW) of electric power, and the four together produced about 10% of Ukraine's electricity at the time of the accident. Construction of the plant began in the late 1970s, with reactor no. 1 commissioned in 1977, followed by no. 2 (1978), no. 3 (1981), and no. 4 (1983). Two more reactors, no. 5 and 6, also capable of producing 1 GW each, were under construction at the time of the disaster.


Accident
On 26 April 1986 at 1:23 a.m., reactor 4 suffered a massive, catastrophic power excursion (the chain reaction grew out of control, similar to the initial stage in the detonation of a nuclear weapon). This caused a steam explosion, followed by a second (chemical, not nuclear) explosion from the ignition of generated hydrogen mixed with air, which tore the top from the reactor and its building, and exposed the reactor core. This dispersed large amounts of radioactive particulate and gaseous debris containing cesium-137 and strontium-90 which are highly radioactive reactor waste products. The open core also allowed air (oxygen) to contact the super-hot core containing 1,700 tonnes] of combustible graphite moderator. The burning graphite moderator increased the emission of radioactive particles, carried by the smoke. The reactor was not contained by any kind of hard containment vessel (unlike most Western plants, Soviet reactors often did not have them). Radioactive particles were carried by wind across international borders.

 

Planning the test of the safety device
During the daytime of 25 April 1986, reactor 4 was scheduled to be shut down for maintenance as it was near the end of its first fuel cycle. An experiment was proposed to test a safety emergency core cooling feature during the shut down procedure.

A very large amount of cooling water is needed to maintain a safe temperature in the reactor core. The reactor consisted of about 1,600 individual fuel channels and each operational channel required a flow of 28 tons of water per hour. There was concern that in case of an external power failure the Chernobyl power station would overload, leading to an automated safety shut down in which case there would be no external power to run the plant's cooling water pumps. Chernobyl's reactors had three backup diesel generators. The generator required 15 seconds to start up but took 6075 seconds to attain full speed and reach its capacity of 5.5 MW required to run one main cooling water pump.

The nuclear reactor needs coolant even when not actively operating. In case of an external power failure, the reactor would automatically scram; control rods would be inserted and stop the nuclear fission process (and hence steam generation). However, in the spent fuel, the fission products themselves were highly radioactive, and continued to produce heat as they decayed. This could amount to 1-2 percent of the normal output of the plant. If not immediately removed by coolant systems, the heat could lead to core damage.

This one-minute power gap was considered unacceptable and it was suggested that the mechanical energy (rotational momentum) of the steam turbine could be used to generate electricity to run the main cooling water pumps, while it was spinning down. In theory, it should have been able to provide power for 45 seconds and thus bridge the power gap between the onset of the external power failure and the full availability of electric power from the emergency diesel generators, but it needed to be tested. All previous tests ended unsuccessfully. The very first test in 1982 showed that the system voltage of the turbine-generator required refinement, it did not maintain the desired magnetic field during the rotation slowdown. The system had been refined, and in 1984 the test was repeated, but it also proved unsuccessful. In 1985 the test was attempted a third time, but it also gave no results. The exact same program was tested again in 1986.

The experiment concerned only different switchings in the electrical chains of power unit. Since the reactor was scrammed automatically at the very beginning of the experiment (as soon as it ceased to feed steam to the turbine,) the experiment should not have had any detrimental effect on the safety of the reactor. Therefore, the test program was apparently not coordinated with either the chief designer of the reactor, nor with the scientific manager. Instead, it was approved only by the director of the plant (and even this was done incorrectly). According to the test parameters, at the start of the experiment, the thermal output of the reactor should have been no lower than 700 MW. If the conditions of the reactor had been as planned, the test likely would have proceeded safely, as the eventual disaster resulted from unplanned attempts to boost the inadequate reactor output once the experiment had started.

The Chernobyl power plant had been in operation for two years without this important safety feature. The station managers must have wished to correct this at the first opportunity. This could explain why they were so determined to carry out the test, even when serious problems arose, and why the requisite approval for the test was not sought from the Soviet nuclear oversight regulatory body.

For the experiment, the reactor would be set at a low power setting and the steam turbine run up to full speed, at which point the steam supply would be closed off and the turbines allowed to freewheel, as the results were recorded.

 
The Chernobyl disaster
 

Conditions prior to the accident
Conditions to run the test were prepared prior to the day shift of 25 April 1986. The day shift workers had been instructed in advance about the test and were familiar with procedures. A special team of electrical engineers was present to test the new voltage regulating system. As planned, on 25 April a gradual reduction in the output of the power unit was begun at 01:06, and by the beginning of the day shift the power level had reached 50%. Another regional power station unexpectedly went off line, and the Kiev grid controller requested that the further reduction of Chernobyl's output be postponed, as power was consequently needed to satisfy the evening peak demand. The Chernobyl plant director agreed and postponed the test to comply.

At 11:04 p.m., the Kiev grid controller allowed the reactor shut-down to resume. This delay had some serious consequences: the day shift had long since departed, the evening shift was also preparing to leave, and the night shift wouldn't take over until 12:00 midnight, well into the job. Further rapid reduction in the power level from 50% was actually executed during the shift change-over. The special team of electrical engineers must have been exhausted from the long wait; according to plan, the test should have been finalized during the daytime and the night shift would only have had to maintain basic cooling systems in a plant otherwise shut down; the night shift had very limited time to prepare and carry out the experiment. Alexander Akimov was chief of the night shift and Leonid Toptunov was the operator responsible for the reactor's operational regime, including the movement of the control rods. Toptunov was a young engineer who had worked independently as a senior engineer for about only three months.

An emergency would not have occurred if the regulations  were followed. The operators of the power plant and the conductors of the experiment on the No. 4 reactor held too much faith in the reactor; to them, a catastrophe was simply inconceivable. Because of this, they had no qualms about disabling the safety features of the reactor and taking unnecessary risks to carry out the experiment.

The test plan called for the power output of reactor 4 to be reduced from its nominal 3200 MW thermal to 7001000 MW thermal. The power level established in the test program (700 MW) was achieved at 00:05 on 26 April; however, due to the natural production of a neutron absorber in the core, Xenon-135, reactor power continued to lower, even without operator action. As the power reached approximately 500 MW, Toptunov committed an error and inserted the control rods too far, bringing the reactor to a near shutdown. The exact circumstances will probably never be known as both Akimov and Toptunov died from radiation sickness.

The reactor power dropped to 30 MW thermal (or less)almost complete shut down level and approximately 5 percent of what was expected. Control room personnel made a decision to restore the power and extracted the reactor control rods, though several minutes lapsed after their extraction until the power output began to increase and subsequently stabilize at 160-200 MW (thermal). In this case the majority of control rods proved to be on their upper limits, the low value of the operational reactivity margin restricted further rise of reactor power. Rapid reduction in the power and subsequent work at the level of less than 200 MW led to that increased poisoning reactor core by the isotope of xenon-135, which made it necessary to additionally extract control rods from the reactor core.

The operation of the reactor at the low level of power with the small reactivity margin was accompanied by the instability of the thermohydraulic parameters and possibly by the instability of neutron flux. The control room received repeated emergency signals on the levels in the separator drums, the opening of the reduction valves which allow excess steam into a turbine condenser, large overregulation in the flow rate of feed water, and warning signals about the controllers of neutron power. For this very reason in the period 00:35 on 00:45, apparently, in order to preserve the reactor power level, emergency signals were ignored from the thermal-hydraulic parameters and signals from the Reactor Emergency Protection System (AZ-5) appeared on, turning off both turbine-generators.

After reaching more or less stable state at the level of the power of 200 MW the preparation for the experiment was continued. As part of the test plan, at 1:05 a.m. on 26 April extra water pumps were activated, increasing the water flow. The increased coolant flow rate through the reactor produced an increase in the temperature of heat-transfer agent at the entrance into the reactor core, which approached the temperature of the beginning of the effervescence of water. The flow exceeded the allowed limit at 1:19 a.m. From the other side the extra water lowered the core temperature and reduced steam voids. Since water also absorbs neutrons (and the higher density of liquid water makes it a better absorber than steam), it causes tendency to decrease the reactor power, prompting the operators to remove the manual control rods.

All these actions led to an extremely dangerous condition with nearly all of the control rods removed, a setup for a runaway reaction, as it was explained after emergency.



Experiment and explosion



Aerial view of the damaged core.
Roof of the turbine hall is damaged (image centre).
Roof of the adjacent reactor 3 (image lower left) shows minor fire damage.


At 1:23:04 a.m. the experiment began, the steam to the turbines was shut off, and a run down of the turbine generator began, together with four (from the total number of eight) Main Circulating Pumps (MCP). Start-up of the diesel generator and stepped pick-up of load ended by 01:23:43 and in this period power supply to these four MCPs was achieved due to the run down of the turbine generator. As the momentum of the turbine generator drove the water pumps, the water flow rate decreased, leading to the formation of steam voids. Because of the positive void coefficient of the RBMK reactor, it was now primed to embark on a deadly positive feedback loop, in which the formation of steam voids decreased the ability of the liquid water coolant to absorb neutrons, which led to a tendency towards an increase in the reactor's power output, causing yet more water to flash into steam, and yet more positive reactivity appearing in the reactor. However, in almost the entire period of the experiment the automatic control system successfully counteracted this, continuously inserting control rods into the reactor core.

At 1:23:39 (at 1:23:40 by the time of the centralized control system SKALA) the AZ-5 button of the reactor emergency protection system was pressed, which ordered a "SCRAM"a shutdown of the reactor, fully inserting all control rods, including the manual control rods that had been incautiously withdrawn earlier. The reason why the AZ-5 button was pressed has not been reliably verified and this gives occasion for different interpretations, whether it was done as an emergency measure, or simply as a routine method of shutting down the reactor upon the completion of the experiment. There is a view that the SCRAM may have been ordered as a response to the unexpected rapid power increase; although there is no recorded data which convincingly testifies to this.

Moreover, doubts have been expressed about the question as to whether the button was pressed at that moment. And it is asserted that the signal was not from the button but was automatically produced by the emergency protection system without any operators help. But, at the same time, SKALA clearly registered a signal from the button itself. In spite of all this, the question as to when the AZ-5 button was pressed (and indeed whether it really was pressed) is still the subject of debate. There are assertions that the pressure was caused by the rapid power acceleration at the start. It is alleged furthermore that the button was pressed during the time of the destruction of the reactor. According to other assertions, it happened earlier and was performed in calm conditions.

Dyatlov writes in his book:

Prior to 01:23:40, systems of centralized control did not register any parameter changes that could justify the SCRAM. The Commission gathered and analyzed large amounts of material and, as stated in its report, failed to determine the reason why the SCRAM was ordered. There was no need to look for the reason. The reactor was simply being shut down upon the completion of the experiment.

For whatever reason the SCRAM (AZ-5) command was executed, insertion of control rods into the reactor core began. The control rod insertion mechanism operated at a relatively slow speed (0.4 m/s) taking 1820 seconds to travel the full approximately 7 meter core-length (height). A bigger problem was a flawed graphite-tip control rod design, which initially displaced coolant, before the reaction was slowed. In this way, the SCRAM actually increased the reaction rate. At this point a massive energy spike occurred, and the core overheated. Some of the fuel rods fractured, blocking the control rod columns, and causing the control rods to become stuck after being inserted only one-third of the way. Within three seconds the reactor output rose above 530 MW. The subsequent course of events was not registered by instruments: it is known only as the result of mathematical simulation. According to some estimations, the reactor jumped to around 30 GW thermal, ten times the normal operational output but not immediately. First a great rise in power caused the rise of fuel temperature and massive steam buildup with rapid increasing in steam pressure. All that destroyed fuel elements and ruptured channels in which these elements located.

No coherent view exists as to the precise sequence of the processes that led to the destruction of the reactor and the power unit building. There is a general understanding that it was steam from the wrecked channels entering the reactor inner space that caused the destruction of the reactor casing, tearing off and lifting by the force of 2,000 tons the upper plate (to which entire reactor assembly is fastened). Apparently this was the first explosion, which many heard. This was a steam explosion like the explosion of a steam boiler from the excess pressure of vapor. This ruptured further fuel channels, the reactor core suffered total water loss and a high positive void coefficient could entirely appear. A second, more powerful explosion occurred about two or three seconds after the first.

There are different points of view regarding the nature of this explosion. There is the view that "the second explosion was caused by the hydrogen which had been produced either by the overheated steam-zirconium reaction or by the reaction of red-hot graphite with steam that produce hydrogen and oxygen". According to another hypothesis, this was an explosion of a nuclear nature, i.e., the thermal explosion of the reactor as a result of the uncontrollable escape of fast neutrons, caused by the complete water loss in the reactor core. The high positive void coefficient makes this version of the emergency entirely plausible. Finally, there is a version that the explosion was caused, exceptionally, by steam. According to this version, the flow of steam and the steam pressure caused all the destruction following the ejection from the shaft of the substantial part of the graphite and fuel.

According to observers outside Unit 4, burning lumps of material and sparks shot into the air above the reactor. Some of them fell onto the roof of the machine hall and started a fire. About 25 per cent of the red-hot graphite blocks and overheated material from the fuel channels was ejected. ... Parts of the graphite blocks and fuel channels were blown out of the reactor building. ... As a result of the damage to the building an airflow through the core was established by the high temperature of the core. The air ignited the hot graphite and started a graphite fire.

The graphite fire greatly contributed to the spread of radioactive material and the contamination of outlying areas.

Contrary to safety regulations, a combustible material (bitumen) had been used in the construction of the roof of the reactor building and the turbine hall. Ejected material had ignited at least five fires on the roof of the (still operating) adjacent reactor 3. It was imperative to put those fires out and protect the cooling systems of reactor 3. Inside reactor 3, the chief of the night shift, Yuri Bagdasarov, wanted to shut down the reactor immediately, but chief engineer Nikolai Fomin would not allow this. The operators were given respirators and potassium iodide tablets and told to continue working. At 05:00, however, Bagdasarov made his own decision to stop the reactor, leaving only those operators there who had to work the emergency cooling systems.



The Chernobyl disaster
 

Immediate crisis management

Radiation levels
The radiation levels in the worst-hit areas of the reactor building have been estimated to be 5.6 röntgen per second (R/s) (0.056 Grays per second, or Gy/s), which is equivalent to 20,000 röntgen per hour (R/hr) (200 Gy per hour, or Gy/hr). A lethal dose is around 500 röntgen (5 Gy) over 5 hours, so in some areas, unprotected workers received fatal doses within several minutes. However, a dosimeter capable of measuring up to 1,000 R/s (10 Gy/s) was inaccessible due to the explosion, and another one failed when turned on. All remaining dosimeters had limits of 0.001 R/s (0.00001 Gy/s) and therefore read "off scale". Thus, the reactor crew could ascertain only that the radiation levels were somewhere above 0.001 R/s (3.6 R/hr, or 0.036 Gy/hr), while the true levels were much higher in some areas.

Because of the inaccurate low readings, the reactor crew chief Alexander Akimov assumed that the reactor was intact. The evidence of pieces of graphite and reactor fuel lying around the building was ignored, and the readings of another dosimeter brought in by 4:30 a.m. were dismissed under the assumption that the new dosimeter must have been defective. Akimov stayed with his crew in the reactor building until morning, trying to pump water into the reactor. None of them wore any protective gear. Most of them, including Akimov, died from radiation exposure within three weeks.


Fire containment
Shortly after the accident, firefighters arrived to try to extinguish the fires. The first one to the scene was a Chernobyl Power Station firefighter brigade under the command of Lieutenant Vladimir Pravik, who died on 9 May 1986 of acute radiation sickness. They were not told how dangerously radioactive the smoke and the debris were, and may not even have known that the accident was anything more than a regular electrical fire: "We didn't know it was the reactor. No one had told us."

Grigorii Khmel, the driver of one of the fire-engines, later described what happened:

We arrived there at 10 or 15 minutes to two in the morning ... We saw graphite scattered about. Misha asked: What is graphite? I kicked it away. But one of the fighters on the other truck picked it up. It's hot, he said. The pieces of graphite were of different sizes, some big, some small enough to pick up ...
We didn't know much about radiation. Even those who worked there had no idea. There was no water left in the trucks. Misha filled the cistern and we aimed the water at the top. Then those boys who died went up to the roof - Vashchik Kolya and others, and Volodya Pravik ... They went up the ladder ... and I never saw them again.
 

The immediate priority was to extinguish fires on the roof of the station and the area around the building containing Reactor No. 4 to protect No. 3 and keep its core cooling systems intact. The fires were extinguished by 5 a.m., but many firefighters received high doses of radiation. The fire inside Reactor No. 4 continued to burn until 10 May 1986; it is possible that well over half of the graphite burned out. The fire was extinguished by a combined effort of helicopters dropping over 5,000 tonnes of materials like sand, lead, clay and boron onto the burning reactor and injection of liquid nitrogen. Ukrainian filmmaker Vladimir Shevchenko captured film footage of a Mi-8 helicopter as it lost its bearings while dropping its load and got its rotors tangled in the gibbets of a nearby construction crane, causing the wrecked helicopter to fall near the damaged reactor building and kill its two-man crew.

From eyewitness accounts of the firefighters involved before they died (as reported on the CBC television series Witness), one described his experience of the radiation as "tasting like metal", and feeling a sensation similar to that of pins and needles all over his face. (This is similar to the description given by Louis Slotin, a Manhattan Project physicist who died days after a fatal radiation overdose from a criticality accident.)

The explosion and fire threw particles of the nuclear fuel and also far more dangerous radioactive elements like caesium-137, iodine-131, strontium-90 and other radionuclides into the air: the residents of the surrounding area observed the radioactive cloud on the night of the explosion.




The abandoned city of Pripyat with Chernobyl plant in the distance.
 

Evacuation of Pripyat
The nearby city of Pripyat was not immediately evacuated.

Only after radiation levels set off alarms at the Forsmark Nuclear Power Plant in Sweden[38] did the Soviet Union admit that an accident had occurred, but authorities attempted to conceal the scale of the disaster. To evacuate the city of Pripyat, the following warning message was reported on local radio: "An accident has occurred at the Chernobyl Nuclear Power Plant. One of the atomic reactors has been damaged. Aid will be given to those affected and a committee of government inquiry has been set up." This message gave the false impression that any damage and radiation was localized.

The government committee formed to investigate the accident, led by Valeri Legasov, arrived at Chernobyl in the evening of 26 April. By that time two people were dead and 52 were in the hospital. During the night of 26 April / 27 Aprilmore than 24 hours after the explosionthe committee, faced with ample evidence of extremely high levels of radiation and a number of cases of radiation exposure, had to acknowledge the destruction of the reactor and order the evacuation of the nearby city of Pripyat.

The evacuation began at 14:00, 27 April. To reduce baggage, the residents were told the evacuation would be temporary, lasting approximately three days. As a result, Pripyat still contains personal belongings. An exclusion zone of 30 km/19 mi remains in place today.
 

Evacuation of Pripyat.

 

Steam explosion risk
There was a bubbler pool beneath the reactor. It served as a large water reservoir from the emergency cooling pumps and as a pressure suppression system capable of condensing steam from a (small) broken steam pipe. The pool and the basement were flooded due to ruptured cooling water pipes and accumulated fire water. It now constituted a serious steam explosion risk. The smouldering fuel and other material above, a corium at more than 1200C, started to burn their way through the reactor floor and mixed with molten concrete that had lined the reactor, creating a radioactive semi-liquid material comparable to lava. If this mixture had melted through the floor into the pool of water, it would have created a massive steam explosion which would eject more radioactive material from the reactor. It became an immediate priority to drain the pool.

The bubbler pool could be drained by opening its sluice gates. Heroic volunteers in diving suits entered the radioactive water and managed to open the gates. These were engineers Alexei Ananenko (who knew where the valves were) and Valeri Bezpalov, accompanied by a third man, Boris Baranov, who provided them with light from a lamp, though this lamp failed, leaving them to find the valves by feeling their way along a pipe. All of them returned to the surface and according to Ananenko, their colligues jumped from the happines when they heard they managed to open the valves. Despite their good condition after the task completion, all of them suffered from radiation sickness an at least two of them - Ananenko and Bezpalov - died in the process. Some sources, however, claim incorrectly that they died in the plant. It is likely that intense alpha radiation hydrolyzed the water generating a hydrogen peroxide (H2O2) solution with a low pH, akin to an oxidizing acid. Confirmation that bubbler pool waters were converted to H2O2 is confirmed by the identification of the minerals studtite and metastudtite in the Chernobyl lavas, the only minerals that contain peroxide. Fire brigade pumps were then used to drain the basement. The operation was only completed by 8 May, after having pumped out 20,000 tonnes of highly radioactive water.

With the bubbler pool gone, a meltdown was less likely to produce a powerful steam explosion. In order to do so, the molten core would now have to reach the water table below the reactor. To reduce the likelihood of this it was decided to freeze the earth beneath the reactor; this would also stabilize the foundations. Using oil drilling equipment, injection of liquid nitrogen began on 4 May. It was estimated that 25 tonnes of liquid nitrogen per day would be required to keep the soil frozen at -100 C.This idea was soon scrapped and the bottom room where the cooling system would have been installed was filled with cement.
 

Debris removal
The worst of the radioactive debris was collected inside what was left of the reactor, much of it shoveled in by liquidators wearing heavy protective gear (dubbed "bio-robots" by the military); these workers could only spend a maximum of 40 seconds at a time working on the rooftops of the surrounding buildings due to the extremely high doses of radiation given off by the blocks of graphite and other debris. The reactor itself was covered with bags containing sand, lead and boric acid thrown off helicopters (some 5,000 metric tonnes during the week following the accident). By December 1986 a large concrete sarcophagus had been erected, to seal off the reactor and its contents.

Many of the vehicles used by the "liquidators" remain parked in a field in the Chernobyl area to this day, most giving off doses of 10-30 R/hr (0.1-0.3 Gy/hr) over 20 years after the disaster.
 

Causes
There were two official explanations of the accident: the first, subsequently acknowledged as erroneous, was published in August 1986 and effectively placed the blame on the power plant operators. To investigate the causes of the accident the IAEA created the advisory group known as International Nuclear Safety Advisory Group (INSAG) which as a whole also supported this view, on the basis of the materials given by the Soviet side and the oral statements of specialists in its report of 1986 INSAG-1 . It was alleged that the accident which had such catastrophic consequences was caused by the gross violation of operating rules and regulations. "During preparation and testing of the turbine generator under run-down conditions using the auxiliary load, personnel disconnected a series of technical protection systems and breached the most important operational safety provisions for conducting a technical exercise".  This was probably due to their lack of knowledge of reactor physics and engineering, as well as lack of experience and training. According to these allegations, at the time of the accident the reactor was being operated with many key safety systems shut off, most notably the Emergency Core Cooling System (ECCS). Personnel had an insufficiently detailed understanding of the technical procedures involved with the nuclear reactor and knowingly infringed regulations in order to speed up completion of the test.

"The developers of the reactor plant considered this combination of events to be impossible and therefore did not allow for the creation of emergency protection systems capable of preventing the combination of events that led to the crisis, namely the intentional disabling of emergency protection equipment plus the violation of operating procedures. Thus the primary cause of the accident was the extremely improbable combination of rule infringement plus the operational routine allowed by the power station staff."

By this account, deficiencies in the reactor design and in the operating regulations that made this accident possible were cast to one side and mentioned only casually. Serious critical observations covered only general questions and did not address the specific reasons for the accident. The following general picture arose from these observations. Several procedural irregularities also helped to make the accident possible. One was insufficient communication between the safety officers and the operators in charge of the experiment being run that night. The reactor operators disabled safety systems down to the generators, which the test was really about. The main process computer, SKALA, was running in such a way that the main control computer could not shut down the reactor or even reduce power. Normally the reactor would have started to insert all of the control rods. The computer would have also started the "Emergency Core Protection System" that introduces 24 control rods into the active zone within 2.5 seconds, which is still slow by 1986 standards. All control was transferred from the process computer to the human operators.

This view is reflected in the numerous publications on the theme of the Chernobyl accident, in the artistic works that appeared immediately after the accident and in the long time that it reigned in the public consciousness and in popular publications. In 1993 the IAEA Nuclear Safety Advisory Group (INSAG) published an additional report INSAG-7  which reviewed that part of the INSAG-1 report in which primary attention is given to the reasons for the accident. Most of the accusations against staff for breach of regulations were acknowledged to be erroneous, based on incorrect information obtained in August 1986. This report reflected another view of the reasons for the accident, presented in appendix I.
According to this account, turning off the ECCS, and also interfering with the settings on the protection equipment and blocking the level and pressure in the separator drum, did not contribute to the original cause of the accident and its magnitude, though they were possibly a breach of regulations. Turning off the emergency system designed to protect against the stopping of the two turbine generators was not a breach of regulations. In fact, pushing the button on the AZ-5 emergency protection system was a normal initial emergency action for damping down the reactor.
Human factors contributed to the conditions that led to the disaster, namely working with a small operational reactivity margin (ORM) and working at a low level of power in the reactor, less than 700 MW - the level documented in the run-down test program. Nevertheless, working at this low level of power was not forbidden in the regulations, despite what Soviet experts asserted in 1986.
Regulations forbade work with a small margin of reactivity. However, ... post-accident studies have shown that the way in which the real role of the ORM is reflected in the Operating Procedures and design documentation for the RBMK-1000 is extremely contradictory , and more ORM was not treated as an operational safety limit, violation of which could lead to an accident.

According to this report, the chief reasons for the accident lie in the peculiarities of physics and in the construction of the reactor. There are two such reasons:

1.The reactor had a dangerously large positive void coefficient. The void coefficient is a measurement of how the reactor responds to increased steam formation in the water coolant. Most other reactor designs have a negative coefficient, i.e. they attempt to decrease the heat output in the presence of an increase of the vapor phase in the reactor, because if the coolant contains steam bubbles, fewer neutrons are slowed down. Faster neutrons are less likely to split uranium atoms, so the reactor produces less power (a negative feed-back). Chernobyl's RBMK reactor, however, used solid graphite as a neutron moderator to slow down the neutrons, and the water in it, on the contrary, acts like a harmful neutron absorber. Thus neutrons are slowed down even if steam bubbles form in the water. Furthermore, because steam absorbs neutrons much less readily than water, increasing the intensity of vaporization means that more neutrons are able to split uranium atoms, increasing the reactor's power output. This makes the RBMK design very unstable at low power levels, and prone to suddenly increasing energy production to a dangerous level. This behavior is counter-intuitive, and this property of the reactor was unknown to the crew.

2. A more significant flaw was in the design of the control rods that are inserted into the reactor to slow down the reaction. In the RBMK reactor design, the lower part of the control rods was made of graphite and was 1.3 meters shorter than necessary and in the space beneath them were hollow channels filled with water. The upper part of the rodthe truly functional part which absorbs the neutrons and thereby halts the reactionwas made of boron carbide. With this design, when the rods are inserted into the reactor from the uppermost position, initially the graphite parts displace some coolant. This greatly increases the rate of the fission reaction, since graphite (in the RBMK) is a more potent neutron moderator (absorbs far fewer neutrons than the boiling light water). Thus for the first few seconds of control rod activation, reactor power output is increased, rather than reduced as desired. This behavior is counter-intuitive and was not known to the reactor operators.

3. Other deficiencies besides these were noted in the RBMK-1000 reactor design, as were its non-compliance with accepted standards and with the requirements of nuclear reactor safety.

Both views were heavily lobbied by different groups, including the reactor's designers, power plant personnel, and by the Soviet and Ukrainian governments. The IAEA's 1986 analysis attributed the main cause of the accident to the operators' actions. But Report 1993 of the IAEA, a revised analysis, attributed the main cause to the reactor's design. The simultaneous existence of two such opposing viewpoints as to the reasons for the Chernobyl accident and the nonstop debate they engendered were made possible additionally because the primary data covering the disaster, as registered by the instruments and sensors, were not completely published in the official sources.

Once again, the human factor had to be considered as a major element in causing the accident. INSAG notes that both the operating regulations and staff handled the disabling of the reactor protection easily enough: witness the length of time for which the ECCS was out of service while the reactor was operated at half power. INSAGs view is that it was the deviation from the test program taken by the operating crew that was mostly to blame. Most reprehensibly, unapproved changes in the test procedure were deliberately made on the spot, although the plant was known to be in a very different condition from that intended for the test.

As in the previously released report INSAG-1, close attention is paid in report INSAG-7 to the inadequate (at the moment of the accident) culture of safety at all levels. Deficiency in the safety culture was inherent not only at the operational stage but also, and to no lesser extent, during activities at other stages in the lifetime of nuclear power plants (including design, engineering, construction, manufacture and regulation). The poor quality of operating procedures and instructions, and their conflicting character, put a heavy burden on the operating crew, including the Chief Engineer.

The accident can be said to have flowed from a deficient safety culture, not only at the Chernobyl plant, but throughout the Soviet design, operating and regulatory organizations for nuclear power that existed at that time.




 

Effects

International spread of radioactivity
The nuclear meltdown produced a radioactive cloud that floated not only over the modern states of Russia, Belarus, Ukraine and Moldova, but also Turkish Thrace, the Southern coast of the Black Sea, Macedonia, Serbia, Croatia, Bosnia-Herzegovina, Bulgaria, Greece, Romania, Lithuania, Estonia, Latvia, Finland, Denmark, Norway, Sweden, Austria, Hungary, the Czech Republic and the Slovak Republic, The Netherlands, Belgium, Slovenia, Poland, Switzerland, Germany, Luxembourg, Italy, Ireland, France (including Corsica) the United Kingdom and the Isle of Man.

The initial evidence that a major exhaust of radioactive material was affecting other countries came not from Soviet sources, but from Sweden, where on the morning of the 28 April  workers at the Forsmark Nuclear Power Plant (approximately 1,100 km (680 mi) from the Chernobyl site) were found to have radioactive particles on their clothes. It was Sweden's search for the source of radioactivity, after they had determined there was no leak at the Swedish plant, which at noon of 28 April led to the first hint of a serious nuclear problem in the western Soviet Union. Hence the evacuation of Pripyat on the 27 April 36 hours after the initial explosions was silently completed before the disaster became known outside the Soviet Union. The rise of radiation levels had at that time already been measured in Finland, but a civil service strike delayed the response and publication.

Contamination from the Chernobyl accident was scattered irregularly depending on weather conditions. Reports from Soviet and Western scientists indicate that Belarus received about 60% of the contamination that fell on the former Soviet Union. However, the 2006 TORCH report stated that half of the volatile particles had landed outside Ukraine, Belarus and Russia. A large area in Russia south of Bryansk was also contaminated, as were parts of northwestern Ukraine. Studies in countries around the area say that over one million people could have been affected by radiation.

Recently published data of a long-term monitoring programme (The Korma-Report) show a decrease of internal radiation exposure of the inhabitants of a region in Belarus close to Gomel. Resettlement may even be possible in prohibited areas provided that people comply with appropriate dietary rules.

In Western Europe, measures were taken including seemingly arbitrary regulations pertaining to the legality of importation of certain foods but not others. In France some officials stated that the Chernobyl accident had no adverse effects.
 

Radioactive release (source term)
Like many other releases of radioactivity into the environment, the Chernobyl release was controlled by the physical and chemical properties of the radioactive elements in its core. While plutonium is often perceived as particularly dangerous nuclear fuel by the general population, its effects are almost eclipsed by those of its fission products. Particularly dangerous are highly radioactive compounds that accumulate in the food chain, such as some isotopes of iodine and strontium.

Two reports on the release of radioisotopes from the site were made available, one by the OSTI, and a more detailed report by OECD, both in 1998. At different times after the accident, different isotopes were responsible for the majority of the external dose. The dose that was calculated is that received from external gamma irradiation for a person standing in the open. The dose to a person in a shelter or the internal dose is harder to estimate.

The release of the radioisotopes from the nuclear fuel was largely controlled by their boiling points, and the majority of the radioactivity present in the core was retained in the reactor.

1. All of the noble gases, including krypton and xenon, contained within the reactor were released immediately into the atmosphere by the first steam explosion.
2. About 55% of the radioactive iodine in the reactor was released, as a mixture of vapor, solid particles and as organic iodine compounds.
3. Caesium and tellurium were released in aerosol form.

Two sizes of particles were released: small particles of 0.3 to 1.5 micrometers (aerodynamic diameter) and large particles of 10 micrometers. The large particles contained about 80% to 90% of the released nonvolatile radioisotopes zirconium-95, niobium-95, lanthanum-140, cerium-144 and the transuranic elements, including neptunium, plutonium and the minor actinides, embedded in a uranium oxide matrix.

 

Health of plant workers
In the aftermath of the accident, 237 people suffered from acute radiation sickness, of whom 31 died within the first three months.[70][71] Most of these were fire and rescue workers trying to bring the accident under control, who were not fully aware of how dangerous the radiation exposure (from the smoke) was. 135,000 people were evacuated from the area, including 50,000 from Pripyat.
 

Residual radioactivity in the environment

Rivers, lakes and reservoirs



Satellite image of the reactor and surrounding area.

The Chernobyl nuclear power plant lies next to the Pripyat River which feeds into the Dnieper River reservoir system, one of the largest surface water systems in Europe. The radioactive contamination of aquatic systems therefore became a major issue in the immediate aftermath of the accident. In the most affected areas of Ukraine, levels of radioactivity (particularly radioiodine: I-131, radiocaesium: Cs-137 and radiostrontium: Sr-90) in drinking water caused concern during the weeks and months after the accident. After this initial period however, radioactivity in rivers and reservoirs was generally below guideline limits for safe drinking water.

Bio-accumulation of radioactivity in fish resulted in concentrations (both in western Europe and in the former Soviet Union) that in many cases were significantly above guideline maximum levels for consumption. Guideline maximum levels for radiocaesium in fish vary from country to country but are approximately 1,000 Bq/kg in the European Union. In the Kiev Reservoir in Ukraine, activity concentrations in fish were several thousand Bq/kg during the years after the accident. In small "closed" lakes in Belarus and the Bryansk region of Russia, activity concentrations in a number of fish species varied from 0.1 to 60 kBq/kg during the period 199092. The contamination of fish caused concern in the short term (months) for parts of the UK and Germany and in the long term (years-decades) in the Chernobyl affected areas of Ukraine, Belarus and Russia as well as in parts of Scandinavia.

 

Groundwater


Map of radiation levels in 1996 around Chernobyl.

Groundwater was not badly affected by the Chernobyl accident since radionuclides with short half-lives decayed away a long time before they could affect groundwater supplies, and longer-lived radionuclides such as radiocaesium and radiostrontium were adsorbed to surface soils before they could transfer to groundwaters. Significant transfers of radionuclides to groundwaters have occurred from waste disposal sites in the 30 km (19 mi) exclusion zone around Chernobyl. Although there is a potential for off-site (i.e. out of the 30 km (19 mi) exclusion zone) transfer of radionuclides from these disposal sites, the IAEA Chernobyl Report argues that this is not significant in comparison to current levels of washout of surface-deposited radioactivity.


Flora and fauna
After the disaster, four square kilometres of pine forest in the immediate vicinity of the reactor turned ginger brown and died, earning the name of the "Red Forest".[77] Some animals in the worst-hit areas also died or stopped reproducing. Most domestic animals were evacuated from the exclusion zone, but horses left on an island in the Pripyat River 6 km (4 mi) from the power plant died when their thyroid glands were destroyed by radiation doses of 150200 Sv. Some cattle on the same island died and those that survived were stunted because of thyroid damage. The next generation appeared to be normal.

A robot sent into the reactor itself has returned with samples of black, melanin-rich fungi that are growing on the reactor's walls.
 

Chernobyl after the disaster
Following the accident, questions arose about the future of the plant and its eventual fate. All work on the unfinished reactors 5 and 6 was halted three years later. However, the trouble at the Chernobyl plant did not end with the disaster in reactor 4. The damaged reactor was sealed off and 200 metres (660 ft) of concrete was placed between the disaster site and the operational buildings. The Ukrainian government continued to let the three remaining reactors operate because of an energy shortage in the country. A fire broke out in the turbine building of reactor 2 in 1991; the authorities subsequently declared the reactor damaged beyond repair and had it taken offline. Reactor 1 was decommissioned in November 1996 as part of a deal between the Ukrainian government and international organizations such as the IAEA to end operations at the plant. On 15 December 2000, then-President Leonid Kuchma personally turned off Reactor 3 in an official ceremony, effectively shutting down the entire plant transforming the Chernobyl plant from energy producer to energy consumer.

 

Chernobyl's Exclusion Zone
In his book, Disasters: Wasted Lives, Valuable Lessons, Economist and Crisis Consultant Randall Bell writes after his research at Chernobyl, "There is a 17-mile (sic) Exclusion Zone around Chernobyl where officially nobody is allowed to live, but people do. These "resettlers" are elderly people who lived in the region prior to the disaster. Today there are approximately 10,000 people between the ages of 60 and 90 living within the Zone around Chernobyl. Younger families are allowed to visit, but only for brief periods of time.

"Eventually the land could be utilized for some sort of industrial purpose that would involve concrete sites," Randall Bell continues. "But estimates range from 60 200 years before this would be allowed. Farming or any other type of agricultural industry would be dangerous and completely inappropriate for at least 200 years. It will be at least two centuries before there is any chance the situation can change within the 1.5-mile Exclusion Zone. As for the #4 reactor where the meltdown occurred, we estimate it will be 20,000 years before the real estate will be fully safe."

 

Controversy over "Wildlife Haven" claim
The Exclusion Zone around the Chernobyl nuclear power station is reportedly a haven for wildlife. As humans were evacuated from the area just over 23 years ago, existing animal populations multiplied and rare species not seen for centuries have returned or have been reintroduced e.g. Lynx, Wild Boar, Wolf, Eurasian Brown Bear, European Bison, Przewalski's horse and Eagle Owl. Birds even nest inside the cracked concrete sarcophagus shielding in the shattered remains of reactor number 4. The Exclusion Zone is so lush with wildlife and greenery that the Ukrainian government designated it a wildlife sanctuary in 2000, Chernobyl Special , at 488.7 km2 it is one of the largest wildlife sanctuaries in Europe.

According to a 2005 U.N. report, wildlife has returned despite radiation levels that are presently 10 to 100 times higher than normal background. Although they were significantly higher soon after the accident, the levels have fallen due to radioactive decay.

Some researchers claim that by halting the destruction of habitat, the Chernobyl disaster helped wildlife flourish. Biologist Robert J. Baker of Texas Tech University was one of the first to report that Chernobyl had become a wildlife haven and that many rodents he has studied at Chernobyl since the early 1990s have shown remarkable tolerance for elevated radiation levels.

However Møller et al. (2005) suggested that reproductive success and annual survival rates of barn swallows are much lower in the Chernobyl exclusion zone; 28% of barn swallows inhabiting Chernobyl return each year, while at a control area at Kanev 250 km to the SE the return rate is around 40%. A later study by Møller et al. (2007) furthermore claimed an elevated frequency of 11 categories of subtle physical abnormalities in barn swallows e.g. bent tail feathers, deformed air sacks, deformed beaks, isolated albinistic feathers.

However, another researcher criticised these findings and instead proposed that a lack of human influence in the exclusion zone locally reduced the swallows' insect prey and radiation levels across the vast majority of the exclusion are now too low to have an observable negative effect. But the criticisms raised were responded to in Møller et al. (2008). It is possible that barn swallows are particularly vulnerable to elevated levels of ionizing radiation because they are migratory; they arrive in the exclusion area exhausted and with depleted reserves of radio-protective antioxidants after an arduous journey.

Several researchers groups have suggested that plants in the area have adapted to cope with the high radiation levels by e.g. increasing the activity of DNA cellular repair machinery, hypermethylation etc. Given the uncertainties, further research is needed to assess the long-term health effects elevated of ionizing radiation on Chernobyl's wildlife.


 

Chernobyl today
The Chernobyl reactor is now enclosed in a large concrete sarcophagus which was built quickly to allow continuing operation of the other reactors at the plant.[95] However, the structure is not strong or durable. Some major work on the sarcophagus was carried out in 1998 and 1999. Some 200 tons of highly radioactive material remains deep within it, and this poses an environmental hazard until it is better contained.

A New Safe Confinement structure will be built by the end of 2011, and then will be put into place on rails. It is to be a metal arch 105 meters (344.4 feet) high and spanning 257 meters (842.9 feet), to cover both unit 4 and the hastily built 1986 structure. The Chernobyl Shelter Fund, set up in 1997, has received 810 million from international donors and projects to cover this project and previous work. It and the Nuclear Safety Account, also applied to Chernobyl decommissioning, are managed by the European Bank for Reconstruction and Development (EBRD).

As of 2006, some fuel at units 1 to 3 remained in the reactors, most of which is in each unit's cooling pond, as well as some material in a small interim spent fuel storage facility pond (ISF-1).

In 1999 a contract was signed for construction of a radioactive waste management facility to store 25,000 used fuel assemblies from units 13 and other operational wastes, as well as material from decommissioning units 13 (which will be the first RBMK units decommissioned anywhere). The contract included a processing facility, able to cut the RBMK fuel assemblies and to put the material in canisters, which were to be filled with inert gas and welded shut. The canisters were to be transported to dry storage vaults, where the fuel containers would be enclosed for up to 100 years. This facility, treating 2500 fuel assemblies per year, would be the first of its kind for RBMK fuel. However, after a significant part of the storage structures had been built, technical deficiencies in the concept emerged, and the contract was terminated in 2007. The interim spent fuel storage facility (ISF-2) will now be completed by others by mid 2013.

Another contract has been let for a Liquid radioactive Waste Treatment Plant, to handle some 35,000 cubic meters of low- and intermediate-level liquid wastes at the site. This will need to be solidified and eventually buried along with solid wastes on site.

In January 2008 Ukrainian government announced a 4-stage decommissioning plan which incorporates the above waste activities and progresses towards a cleared site.


 

Lava-like Fuel-Containing Materials (FCMs)
According to official estimates, about 95% of the fuel (about 180 tonnes) in the reactor at the time of the accident remains inside the shelter, with a total radioactivity of nearly 18 million curies (670 PBq). The radioactive material consists of core fragments, dust, and lava-like "fuel-containing materials" (FCM) that flowed through the wrecked reactor building before hardening into a ceramic form.

Three different lavas are present in the basement of the reactor building; black, brown and a porous ceramic. They are silicate glasses with inclusions of other materials present within them. The porous lava is brown lava which had dropped into water thus being cooled rapidly.

 

Degradation of the lava
It is unclear how long the ceramic form will retard the release of radioactivity. From 1997 to 2002 a series of papers were published which suggested that the self irradiation of the lava would convert all 1,200 tons into a submicrometre and mobile powder within a few weeks. But it has been reported that it is likely that the degradation of the lava is to be a slow and gradual process rather than a sudden rapid process. The same paper states that the loss of uranium from the wrecked reactor is only 10 kg (22 lb) per year. This low rate of uranium leaching suggests that the lava is resisting its environment. The paper also states that when the shelter is improved, the leaching rate of the lava will decrease.

Some of the surfaces of the lava flows have started to show new uranium minerals such as Na4(UO2)(CO3)3 and uranyl carbonate. However the level of radioactivity is such that during one hundred years the self irradiation of the lava (2 × 1016 α decays per gram and 2 to 5 × 105 Gy of β or γ) will fall short of the level of self irradiation which is required to greatly change the properties of glass (1018 α decays per gram and 108 to 109 Gy of β or γ). Also the rate of dissolution of the lava in water is very low (10−7 g-cm−2 day−1) suggesting that the lava is unlikely to dissolve in water.

 

Possible consequences of further collapse of the Sarcophagus


The Sarcophagus, the concrete block surrounding reactor #4

The protective box which was placed over the wrecked reactor was named object "Shelter" by the Soviet government, but the media and the public know it as the sarcophagus.

The present shelter is constructed atop the ruins of the reactor building. The two "Mammoth Beams" that support the roof of the shelter are resting partly upon the structurally unsound west wall of the reactor building that was damaged by the accident.[citation needed] The western end of the shelter roof was supported by a wall (at a point designated axis 50). This wall is reinforced concrete, which was cracked by the accident. In December 2006 the Designed Stabilisation Steel Structure (DSSS) was extended until 50% of the roof load (about 400 tons) was transferred from the axis-50 wall to the DSSS. The DSSS is a yellow steel object which has been placed next to the wrecked reactor; it is 63 metres (207 ft) tall and has a series of cantilevers which extend through the western buttress wall and is intended to stabilise the sarcophagus. This was done because if the wall of the reactor building or the roof of the shelter were to collapse, then large amounts of radioactive dust and particles would be released directly into the atmosphere, resulting in a large new release of radioactivity into the environment.

A further threat to the shelter is the concrete slab that formed the "Upper Biological Shield" (UBS), situated above the reactor prior to the accident. This concrete slab was thrown upwards by the explosion in the reactor core and now rests at approximately 15 from vertical. The position of the upper bioshield is considered inherently unsafe, as only debris supports it in its nearly upright position. A collapse of the bioshield would further exacerbate the dust conditions in the shelter, possibly spreading some quantity of radioactive materials out of the shelter, and could damage the shelter itself.

 

Grass and forest fires
It is known that fires can make the radioactivity mobile again. In particular V.I. Yoschenko et al. reported on the possibility of increased mobility of caesium, strontium, and plutonium due to grass and forest fires. As an experiment, fires were set and the levels of the radioactivity in the air down wind of these fires was measured.

Grass and forest fires have happened inside the contaminated zone, releasing radioactive fallout into the atmosphere. In 1986 a series of fires destroyed 23.36 km2 (5,772 acres) of forest, and several other fires have since burned within the 30 km (19 mi) zone. In early May 1992 a serious fire occurred which affected 5 km2 (1,240 acres) of land including 2.7 km2 (670 acres) of forest. This resulted in a great increase in the levels of caesium in airborne dust.
 

Recovery process
The Chernobyl Shelter Fund was established in 1997 at the Denver G7 summit to finance the Shelter Implementation Plan (SIP). The plan calls for transforming the site into an ecologically safe condition through stabilization of the sarcophagus, followed by construction of a New Safe Confinement (NSC). While original cost estimate for the SIP was US$768 million, the 2006 estimate is $1.2 billion. The SIP is being managed by a consortium of Bechtel, Battelle, and Electricité de France, and conceptual design for the NSC consists of a movable arch, constructed away from the shelter to avoid high radiation, to be slid over the sarcophagus. The NSC is expected to be completed in 2012, and will be the largest movable structure ever built.

Dimensions:
Span: 270 m (886 ft)
Height: 100 m (330 ft)
Length: 150 m (492 ft)

The United Nations Development Programme has launched in 2003 a specific project called the Chernobyl Recovery and Development Programme (CRDP) for the recovery of the affected areas. The programme launched its activities based on the Human Consequences of the Chernobyl Nuclear Accident report recommendations and has been initiated in February 2002. The main goal of the CRDPs activities is supporting the Government of Ukraine to mitigate long-term social, economic and ecological consequences of the Chernobyl catastrophe, among others. CRDP works in the four most Chernobyl-affected areas in Ukraine: Kyivska, Zhytomyrska, Chernihivska and Rivnenska.

The International Project on the Health Effects of the Chernobyl Accident (IPEHCA) was created and received $20 million US, mainly from Japan, in hopes of discovering the main cause of health problems due to I131 radiation. These funds that were given to IPEHCA were divided between Ukraine, Belarus, and Russia, the three main affected countries, for further investigation of health effects. As corruption played an important role of the former Soviet countries, most of the foreign aid was given to Russia, and no positive outcome from this money was ever shown.
 

Assessing the disaster's effects on human health
An international assessment of the health effects of the Chernobyl accident is contained in a series of reports by the United Nations Scientific Committee of the Effects of Atomic Radiation (UNSCEAR). UNSCEAR was set up as a collaboration between various UN bodies, including the World Health Organisation, after the atomic bomb attacks on Hiroshima and Nagasaki, to assess the long-term effects of radiation on human health.

UNSCEAR has conducted 20 years of detailed scientific and epidemiological research on the effects of the Chernobyl accident. Apart from the 57 direct deaths in the accident itself, UNSCEAR originally predicted up to 4,000 additional cancer cases due to the accident, however the latest UNSCEAR reports insinuate that these estimates were overstated. In addition, the IAEA states that there has been no increase in the rate of birth defects or abnormalities, or solid cancers (such as lung cancer) corroborating UNSCEAR's assessments.

Precisely, UNSCEAR states:

"Among the residents of Belaruss 09, the Russian Federation and Ukraine there had been, up to 2002, about 4,000 cases of thyroid cancer reported in children and adolescents who were exposed at the time of the accident, and more cases are to be expected during the next decades. Notwithstanding problems associated with screening, many of those cancers were most likely caused by radiation exposures shortly after the accident. Apart from this increase, there is no evidence of a major public health impact attributable to radiation exposure 20 years after the accident. There is no scientific evidence of increases in overall cancer incidence or mortality rates or in rates of non-malignant disorders that could be related to radiation exposure. The risk of leukaemia in the general population, one of the main concerns owing to its short latency time, does not appear to be elevated. Although those most highly exposed individuals are at an increased risk of radiation-associated effects, the great majority of the population is not likely to experience serious health consequences as a result of radiation from the Chernobyl accident. Many other health problems have been noted in the populations that are not related to radiation exposure."

Thyroid cancer is generally treatable. The five year survival rate of thyroid cancer is 96%, and 92% after 30 years, with proper treatment.

The Chernobyl Forum is a regular meeting of IAEA, other United Nations organizations (FAO, UN-OCHA, UNDP, UNEP, UNSCEAR, WHO and The World Bank) and the governments of Belarus, Russia, and Ukraine, which issues regular scientific assessments of the evidence for health effects of the Chernobyl accident. The Chernobyl Forum concluded that twenty-eight emergency workers died from acute radiation syndrome, 15 patients died from thyroid cancer, and it roughly estimated that cancers deaths caused by Chernobyl may reach a total of about 4000 among the 600 000 people having received the greatest exposures. It also concluded that a greater risk than the long-term effects of radiation exposure, is the risk to mental health of exaggerated fears about the effects of radiation:

" ... The designation of the affected population as victims rather than survivors has led them to perceive themselves as helpless, weak and lacking control over their future. This, in turn, has led either to over cautious behavior and exaggerated health concerns, or to reckless conduct, such as consumption of mushrooms, berries and game from areas still designated as highly contaminated, overuse of alcohol and tobacco, and unprotected promiscuous sexual activity."

While it was commented by Fred Mettler that 20 years later:

The population remains largely unsure of what the effects of radiation actually are and retain a sense of foreboding. A number of adolescents and young adults who have been exposed to modest or small amounts of radiation feel that they are somehow fatally flawed and there is no downside to using illicit drugs or having unprotected sex. To reverse such attitudes and behaviors will likely take years although some youth groups have begun programs that have promise.

In addition, disadvantaged children around Chernobyl suffer from health problems which are not only to do with the Chernobyl accident, but also with the desperately poor state of post-Soviet health systems.

Another study critical of the Chernobyl Forum report was commissioned by Greenpeace, which is well known for its anti-nuclear positions. In its report, Greenpeace alleges that "the most recently published figures indicate that in Belarus, Russia and Ukraine alone the accident could have resulted in an estimated 200,000 additional deaths in the period between 1990 and 2004." However, the Greenpeace report failed to discriminate between the general increase in cancer rates that followed the dissolution of the USSR's health system and any separate effects of the Chernobyl accident.

Lastly, in its report Health Effects of Chernobyl, the German affiliate of the International Physicians for the Prevention of Nuclear War (IPPNW) argued that more than 10,000 people are today affected by thyroid cancer and 50,000 cases are expected in the future. According to some commentators, both the Greenpeace and IPPNW reports suffer from a lack of any genuine or original research and failure to understand epidemiologic data. This said, it is important to bear in mind that many of the conclusions from reports such as UNSCEAR remain disputed by other commentators and scientists in the field.



 

In popular culture
The Chernobyl accident attracted a great deal of interest. Because of the distrust that many people had in the Soviet authorities (people both within and outside the USSR) a great deal of debate about the situation at the site occurred in the first world during the early days of the event. Due to defective intelligence based upon photographs taken from space, it was thought that unit number three had also suffered a dire accident.

A few authors claim that the official reports underestimate the scale of the Chernobyl tragedy, counting only 30 victims; some estimate the Chernobyl radioactive fallout as hundreds of times that of the atomic bomb dropped on Hiroshima, Japan, counting millions of exposed.

In general the public knew little about radioactivity and radiation and as a result their degree of fear was increased. It was the case that many professionals (such as the spokesman from the UK NRPB) were mistrusted by journalists, who in turn encouraged the public to mistrust them.

It was noted that different governments tried to set contamination level limits which were stricter than the next country.

In Italy, the fear of nuclear accidents was dramatically increased by the Chernobyl accident: this was reflected in the outcome of the 1987 referendum about the construction of new nuclear plants in Italy. As a result of that referendum, Italy began phasing out its nuclear power plants in 1988.

 

Commemoration of the disaster
The Front Veranda (1986), a lithograph by Susan Dorothea White in the National Gallery of Australia shows awareness of the event worldwide. Heavy Water: A film for Chernobyl was released by Seventh Art in 2006 to commemorate the disaster through poetry and first-hand accounts. The film secured the Cinequest Award as well as the Rhode Island 'best score' award along with a screening at Tate Modern.
 

Chernobyl 20
This exhibit presents the stories of 20 people who have each been affected by the disaster, and each person's account is written on a panel. The 20 individuals whose stories are related in the exhibition are from Belarus, France, Latvia, Russia, Sweden, Ukraine, and the United Kingdom.

Developed by Danish photo-journalist Mads Eskesen, the exhibition is prepared in multiple languages including German, English, Danish, Dutch, Russian and Ukrainian.

In Kiev, Ukraine, the exhibition was launched at the "Chernobyl 20 Remembrance for the Future" conference on 23 April 2006. It was then exhibited during 2006 in Australia, Denmark, the Netherlands, Switzerland, Ukraine, the United Kingdom, and the United States.

 


see also: United Nations member states -
Russian Federation,
Ukraine,Belarus, Moldova,
Armenia, Azerbaijan, Georgia,
Estonia, Latvia, Lithuania,
Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan

 

 

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