THE CHERNOBYL ACCIDENT, April 26, 1986
Phil Mershon
No one is talking about turning the remains of Chernobyl into an amusement park any longer. Now that the earthquakes, tsunamis and nuclear accidents have focused the world on Japan, this feels like a good time to set the Way Back Machine for April 1986, where we shall return to a friendly community that died.
The Chernobyl nuclear facility is located in Ukraine about twenty kilometers south of the border with Belarus. At the time of the accident, the plant had four working reactors. The accident which put the name of the town on everyone’s lips occurred in the very early morning of 26 April 1986 when plant operators ran a test on an electric control system of unit 4. The accident happened because of a combination of basic engineering deficiencies in the reactor as well as faulty actions by the operators. The safety systems had been switched off and the reactor was being operated under improper, unstable conditions, a situation which allowed an uncontrollable power surge. This surge caused the nuclear fuel to overheat and led to a series of steam explosions that severely damaged the reactor building and completely destroyed the unit 4 reactor.
The explosions started lots of fires on the roofs of the reactor building and the machine hall, which were put out by firefighters in a few hours. Approximately twenty hours after the explosions, a large fire started as the material in the reactor ignited combustible gases. The large fire burned for ten days. Helicopters repeatedly dumped neutron-absorbing compounds and fire-control materials into the crater formed by the destruction of the reactor and later the reactor structure was cooled with liquid nitrogen using pipelines originating from another reactor unit.
The radioactive materials from the damaged reactor were presumably released over a ten-day period. An initial high release rate on the first day resulted from the explosions in the reactor. There followed a five-day period of declining releases associated with the hot air and fumes from the burning graphite core material. In the next few days, the release rate increased until day ten, when the releases dropped abruptly, thus ending the period of intense release. The radioactive materials released by the accident deposited with greatest density in the regions surrounding the reactor in the European part of the former Soviet Union.
PHYSICAL CONSEQUENCES OF THE ACCIDENT
The accident at the Chernobyl nuclear power station occurred during a low-power engineering test of the Unit 4 reactor. Safety systems had been switched off, and improper, unstable operation of the reactor allowed an uncontrollable power surge to occur, resulting in successive steam explosions that severely damaged the reactor building and completely destroyed the reactor. An account of the accident and of the quantities of radionuclides released, to the extent that they could be known at the time, were presented by Soviet experts at the Post-Accident Review Meeting at Vienna in August 1986.
PHYSICAL CONSEQUENCES OF THE ACCIDENT
The accident at the Chernobyl nuclear power station occurred during a low-power engineering test of the Unit 4 reactor. Safety systems had been switched off, and improper, unstable operation of the reactor allowed an uncontrollable power surge to occur, resulting in successive steam explosions that severely damaged the reactor building and completely destroyed the reactor. An account of the accident and of the quantities of radionuclides released, to the extent that they could be known at the time, were presented by Soviet experts at the Post-Accident Review Meeting at Vienna in August 1986.
THE ACCIDENT
The Chernobyl reactor is of the type RBMK, which is an abbreviation of Russian terms meaning reactor of high output, multichannel type. It is a pressurized water reactor using light water as a coolant and graphite as a moderator. Detailed information about what is currently known about the accident and the accident sequence has been reported, notably in 1992 by the International Atomic Energy Agency, in 1994 in a report of the Massachusetts Institute of Technology, in 1995 by the Ukrainian Academy of Sciences, and in 1991 and 1996 by the Kurchatov Institute.
The events leading to the accident at the Chernobyl Unit 4 reactor at about 1.24 a.m. on 26 April 1986 resulted from efforts to conduct a test on an electric control system, which allows power to be provided in the event of a station blackout. Actions taken during this exercise resulted in a significant variation in the temperature and flow rate of the inlet water to the reactor core (beginning at about 1.03 a.m.). The unstable state of the reactor before the accident was due both to basic engineering deficiencies (large positive coefficient of reactivity under certain conditions) and to faulty actions of the operators (e.g., switching off the emergency safety systems of the reactor). The relatively fast temperature changes resulting from the operators actions weakened the lower transition joints that link the zirconium fuel channels in the core to the steel pipes that carry the inlet cooling water. Other actions resulted in a rapid increase in the power level of the reactor, which caused fuel fragmentation and the rapid transfer of heat from these fuel fragments to the coolant (between 1.23:43 and 1.23:49 a.m.). This generated a shock wave in the cooling water, which led to the failure of most of the lower transition joints. As a result of the failure of these transition joints, the pressurized cooling water in the primary system was released, and it immediately flashed into steam.
The steam explosion occurred at 1.23:49. It is surmised by what were then Soviet physicists that the reactor core might have been lifted up by the explosion, during which time all water left the reactor core. This resulted in an extremely rapid increase in reactivity, which led to vaporization of part of the fuel at the centre of some fuel assemblies and which was terminated by a large explosion attributable to rapid expansion of the fuel vapor disassembling the core. This explosion, which occurred at about 1.24 a.m., blew the core apart and destroyed most of the building. Fuel, core components, and structural items were blown from the reactor hall onto the roof of adjacent buildings and the ground around the reactor building. A major release of radioactive materials into the environment also occurred as a result of this explosion.
The core debris dispersed by the explosion started more than thirty fires on the roofs of the reactor building and the machine hall, which were covered with highly flammable tar. Some of those fires spread to the machine hall and, through cable tubes, to the vicinity of the Unit 3 reactor. A first group of fourteen firemen arrived on the scene of the accident at 1.28 a.m. Reinforcements were brought in until about 4 a.m., when 250 firemen were available and sixty-nine firemen participated in fire control activities. These activities were carried out at up to 70 meters above the ground under harsh conditions of high radiation levels and dense smoke. By 2.10 a.m., the largest fires on the roof of the machine hall had been put out, while by 2.30 a.m. the largest fires on the roof of the reactor hall were under control. By about 4.50 a.m., most of the fires had been extinguished. These actions caused the deaths of five firefighters.
It has never been established whether fires were originating from the reactor cavity during the first twenty hours after the explosion. However, there was considerable steam and water because of the actions of both the firefighters and the reactor plant personnel. Approximately twenty hours after the explosion, at 9.41 p.m., a large fire started as the material in the reactor became hot enough to ignite combustible gases released from the disrupted core, e.g. hydrogen from zirconium-water reactions and carbon monoxide from the reaction of hot graphite with steam. The fire made noise when it started (some witnesses called it an explosion) and burned with a large flame that initially reached at least 50 meters above the top of the destroyed reactor hall.
The further sequence of events is still somewhat speculative, but the following description conforms with the observations of residual damage to the reactor. It has been suggested that the melted core materials (also called fuel-containing masses, corium, or lava) settled to the bottom of the core shaft, with the fuel forming a metallic layer below the graphite. The graphite layer had a filtering effect on the release of volatile compounds. This is evidenced by a concentration of cesium in the corium of 35%, somewhat higher than would otherwise have been expected in the highly oxidizing conditions that prevailed in the presence of burning graphite. The very high temperatures in the core shaft would have suppressed plate-out of radionuclides and maintained high release rates of penetrating gases and aerosols. After about 6.5 days, the upper graphite layer would have burned off. This is evidenced by the absence of carbon or carbon- containing compounds in the corium. At this stage, without the filtering effect of an upper graphite layer, the release of volatile fission products from the fuel may have increased, although non-volatile fission products and actinides would have been inhibited because of reduced particulate emission.
On day eight after the accident, it would appear that the corium melted through the lower biological shield (LBS) and flowed onto the floor of the sub-reactor region. This rapid redistribution of the corium and increase in surface area as it spread horizontally would have enhanced the radionuclide releases. The corium produced steam on contact with the water remaining in the pressure suppression pool, causing an increase in aerosols. This may account for the peak releases of radionuclides seen at the last stage of the active period.
Approximately nine days after the accident, the corium began to lose its ability to interact with the surrounding materials. It solidified relatively rapidly, causing little damage to metallic piping in the lower regions of the reactor building. The chemistry of the corium was altered by the large mass of the lower biological shield taken up into the molten corium (about 400 of the 1,200-ton shield of stainless steel construction and serpentine filler material). The decay heat was significantly lowered, and the radionuclide releases dropped by two to three orders of magnitude. Visual evidence of the disposition of the corium supports this sequence of events.
On the basis of an extensive series of measurements in 1987 and 1990 of heat flux and radiation intensities and from an analysis of photographs, an approximate mass balance of the reactor fuel distribution was established. The amount of fuel in the lower regions of the reactor building was estimated to be 71% of the core load at the time of the accident.
Different estimates of the reactor fuel distribution have been proposed by others. Purvis indicated that the amount of fuel in the lava, plus fragments of the reactor core under the level of the bottom of the reactor, is between 27 and 100 t and that the total amount of the fuel in the reactor hall area is between 77 and 140 tons.
What was the extent of the Chernobyl accident?
The Chernobyl accident is the most serious accident in the history of the nuclear industry, at least until the full details of the Japanese accidents are known. Indeed, the explosions that ruptured one of the reactors of the Chernobyl nuclear power plant and the consequent fire that started on the 26 April 1986 and continued for ten days resulted in an unprecedented release of radioactive materials into the environment.
The cloud from the burning reactor spread many types of radioactive materials, especially iodine-131 and caesium-137, over much of Europe. Because radioactive iodine disintegrates rapidly, it largely disappeared within the first few weeks of the accident. Radioactive cesium however is still measurable in soils and some foodstuffs in many parts of Europe. The greatest concentrations of contamination occurred over large areas of the Soviet Union surrounding the reactor in what are now the countries of Belarus, the Russian Federation and Ukraine.
Since the accident, 600,000 people have been involved in emergency, recovery, containment, and cleaning operations although only a small proportion of them have been exposed to dangerous levels of radiation. Those who received the highest doses of radiation were the emergency workers and personnel that were on-site during the first days of the accident (approximately 1000 people).
More than five million people live in areas of Belarus, Russia and Ukraine that are significantly contaminated with caesium-137 from the Chernobyl accident. 400 000 of these people lived in very contaminated areas classified as “areas of strict control” by Soviet authorities. Within this region, the area closest to the Chernobyl power plant was most heavily contaminated and has been designated as the “Exclusion Zone." The 116 000 people who lived there were evacuated in the spring and summer of 1986 to non-contaminated areas, and 220 000 more were relocated in the following years.
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The following is selected from a speech by Dr. Vladimir Chernousenko, former head of the Ukrainian Academy of Science, and the lead investigator of the Chernobyl clean up, at a briefing of Texas officials organized by the Foundation for a Compassionate Society and co-sponsored by WEDO (Women's Environment and Development Organization) in February 1994 in Austin.
In my brief statement I will attempt to answer from the point of view of modern science several questions. First, "Have the discoveries (in radioactivity) over the last fifty years made our lives happy and safe? And I would also like to ask the question, "Can the women of.. the United States feel safe even though these accidents may occur quite a distance away?" And last,... "Does the atomic industry, which is such a hazardous industry, have a right to exist?"
I would like to inform you about the scientific data that have been gathered about exposure to radiation. We have conducted studies of the regions around 20 different nuclear plants in my country. In all of these territories we noticed an increase in the breast cancer rate—sometimes an increase of 15% over the normal level. We noticed a growth of anemia amongst children who lived in those areas, cardiovascular diseases, and cataracts. So from this you can conclude that even without the explosion of nuclear weapons there is quite a bit of danger to human lives.
For many years we believed that this is the most safe and ecological industry. But as a result of an accident of only one reactor..., an amount of radionuclides was emitted which is comparable to that... emitted from all the detonations of nuclear weapons and nuclear tests. So ... the statement that it is the most environmentally safe industry is not true. As a result of an accident at only one reactor, over 65 million people in my country were affected. And for at least the next 15 years, there will be radioactive fallout all over the globe.
We also hear that this is the most economical way of attaining energy. The analysis which we conducted shows that one kilowatt of energy ... from such a facility is the most expensive, because the problem of burying radioactive waste is not included in this ... analysis. Also excluded from this kind of analysis is the disassembling of these facilities ... So if we're to analyze ... all these (excluded) topics, we will see that it is absolutely not advantageous to continue this industry.
I would like to address the question of whether it's possible to feel safe in America when there are catastrophes occurring in Germany and Russia. Unfortunately the answer is "no."
Now I would like to address the question of whether it's possible to feel safe in America when there are catastrophes occurring in Germany and Russia. Unfortunately the answer is "no." Because an accident which happens tens of thousands of kilometers away will necessarily fall out on people in other parts of the world. So our conclusion is that every day that these hazardous industries are in existence brings closer the end of our civilization. That means that we must stop this nuclear madness if we want to continue to exist...
Question: I wonder if you would share with us the effect of your being in Chernobyl on your own personal condition.
Our participation in the clean up of such a catastrophe that is without boundaries completely altered our way of thinking and understanding. Because you have to see the scorched earth which occurs as a result of this accident. You must know about the radioactive zones in which people had to work ... zones (which) were often between 10,000 millirems per hour to 15,000 ... we know that of those persons who receive a dose of 500 rems, half are expected to die immediately... (T)raveling around the various contaminated zones in my country demonstrated that it is now practically impossible to live in the vast territories of Belarus, Ukraine, and two thirds of Russia. And our analysis has demonstrated that as a result of this, there will be over a million casualties. You see, American doctors in Germany said that I have three years left to live.
Question: You mentioned that 65 million people (were affected). Could you explain?
When I spoke of the 65 million, I took into account that various parts of the population received varying doses of radiation. First, there is the dose between 20 and 35 rems. This was the exposure level of the residents of almost one-third of Belarus, one-third of the Ukraine and nine regions of Russia. The next category is those who received between 5 and 1O rems. And the most terrifying thing about this story is that they received this exposure after the accident. Because they were forced to continue to live in the contaminated territories for the duration of eight years. What are the levels of contamination in these territories? The average level in Belarus is 20 curies per square kilometer. There are a number of territories where the level reached 200 and even 400 curies per square kilometer. This leads to women and children inhaling the radioactivity and also consuming it in their food. We're talking about the increase in cancer and anemia. But we've even noticed throat cancer among animals who live in the region.
Question: The question that's always asked of me when I say that nuclear power is dangerous is "where will we get our electricity?" Today on the radio I heard an ad saying that to phase out nuclear power we're going to have to burn down all the forests.
When we speak of energy, and the desire to extract it, we certainly understand that we must destroy something in order to get it. Up until now we've been destroying what's taken the sun millions of years—5 million years—to create one liter of oil. Certainly we're coming to the end of this supply. But you mustn't think that nuclear energy is the panacea for all of these problems ... (Not) because the supply of uranium is almost gone. The problem is that by the time we run out of the supply completely, which will take another 50 years, we will already have destroyed the entire population on the earth. That's why we speak about this. There is only one ecologically sound way of obtaining energy, and that is the utilization of solar energy ... And since our civilization only exists since the sun does shine, we will be able to exist as long as the sun continues to shine. And no nuclear energy can take the place of this...
Question: We hear a lot these days in the United States about what are called inherently safe nuclear reactors. Did you ever .. [?]
I have to disappoint you. To construct a safe reactor is practically impossible either here or in Russia ... we simply cannot get energy from such enterprises. Because we are dealing with nuclear processes, with uncontrolled reactions, which occur within millionths of a second, and no matter what kind of protection mechanism you design, sooner or later the object must explode and they will. Why were they created at all? When they were created, constructed, it was understood that they were extremely dangerous, but at that point the physicists were told that they must save the world from Hitler at any cost and as soon as possible. And unfortunately the physicists accomplished this, which they regret to this day. And I have to tell you that not a single self-respecting scientist, not a single nuclear physicist, not a single theoretical physicist who studied these problems will ever tell you that these enterprises can or should ever be used for energy.
Question: I wonder if you could share with us a little bit the reaction of the Soviet government..[?] to the magnitude of the danger ... [?]
The thing is that at the beginning of the electoral campaign, our representatives and President Kravchuk said that if they were elected they intended to close the Chernobyl power plant immediately. As soon as the people believed them and elected them, they immediately forgot about their promises. That was the reaction of the Ukrainian government. I must tell you that it has always been the case that the energy produced by the Chernobyl power plant has always been sold to the West. (Czechoslovakia, Bulgaria, Turkey, and so on.)
Question: What was the number - in the area directly downwind - what was the percentage of children who remained healthy?
That's zero.
Question: Right after Chernobyl, we had a large public relations campaign by the nuclear industry, and what they were saying was that a similar accident could not happen in this country because commercial nuclear reactors are surrounded by concrete protection.
We've discussed this in Germany, in England, and in America. It is true that the nuclear blocks in those places are surrounded by concrete containment. This was done, for example, to keep an airplane from failing on the heads of people who work at the facility. The force of the explosion at Chernobyl exceeded the protective capabilities of this containment by at least ten-fold. And Dr. Rosalie Bertell, who participated in the investigation of the accident at Three Mile Island, can tell you, if a miracle hadn't occurred, and the hydrogen bubble within that containment hadn't dissipated, the accident within the United States would be comparable to the accident at Chernobyl. And the containment wouldn't have been able to protect from these dangers.
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WHO Report - Health Consequences of the Chernobyl Accident
This provides a summary of a larger report of the results of a WHO-sponsored International Program to monitor the Health Effects of the Chernobyl Accident (IPHECA) and thus represents some of the most comprehensive and accurate information compiled to date.
WHO Report - Health Consequences of the Chernobyl Accident
This provides a summary of a larger report of the results of a WHO-sponsored International Program to monitor the Health Effects of the Chernobyl Accident (IPHECA) and thus represents some of the most comprehensive and accurate information compiled to date.
IPHECA Results in a Nutshell
Total radioactivity releases from the reactor was 200 times that of the combined releases from the atomic bombs dropped on Hiroshima and Nagasaki, mainly in the form of iodine-131, cesium-134, and cesium137.
Of these, the isotope with the greatest health impact is iodine-131 because it accumulates in the thyroid gland. Growing chldren are particularly susceptible because their thyroids are much more active.
Population Exposure Data
· Average Exposure Rate per Year Population Exposed Action Taken
· > 5mSv 135000 all evacuated
· up to 5mSv 270000 voluntary relocation
· compulsory monitoring
· up to 2 mSv 580000 special health monitoring
· up to 1mSv 4000000 regular health monitoring
Of these, the isotope with the greatest health impact is iodine-131 because it accumulates in the thyroid gland. Growing chldren are particularly susceptible because their thyroids are much more active.
Population Exposure Data
· Average Exposure Rate per Year Population Exposed Action Taken
· > 5mSv 135000 all evacuated
· up to 5mSv 270000 voluntary relocation
· compulsory monitoring
· up to 2 mSv 580000 special health monitoring
· up to 1mSv 4000000 regular health monitoring
Non-Radiation Effects Psychological effects due to fear and the stress of dislocation (evacuees). The evacuation caused financial hardships, restrictions of diet, uncertainty regarding housing and employment. The tense situation causes considerable stress which, combined with the constant fear of health damage from the radioactive fallout, led to a rising number of health disorders being reported to local outpatient clinics. The immediate psychological impact was similar to that caused by an earthquake, fire, or other natural disaster. Finally, the study reports a large increase in a number of specific diseases involving the endocrine, nervous, digestive, and genitourinary systems. The study also reports increases in the incidence of mental retardation, behavioral, and emotional problems in exposed children. Present evidence does not suggest that these diseases are radiation-induced, but may have resulted from the considerable stress experienced.
Radiation Effects
Immediate Effects - Limited to reactor plant personnel and firefighters.
Two people died during the accident. 444 people were at the site and were exposed to large amounts of radiation. About 300 were admitted to hospitals and 134 were diagnosed with acute radiation sickness. 28 of these people died within 3 months. Of those who recovered, most continued with emotional or sleep disorders. 30% suffered from various medical disorders that reduced their ability to work. No clinical symptoms of acute radiation syndrome were seen in the people evacuated from the 30-km evacuation zone or in residents of affected areas.
Long-Term Effects
Significant increases of childhood thyroid cancer have been measured in the region around the plant, particularly in the Gomel administrative district.
Usually, the thyroid can be succesfully removed so most of the victimns are expected to recover. Howver, more than 95% of the cases were reported to be highly invasive and the cancer spread to other soft tissues. In a few cases, the children died.
Other thyroid diseases, such as autoimmune thryroiditis, nodular goiter,, and hypothyroidism have been intensely studied, but show no reliable signs of increase.
Other Long-Term Effects
An increase in the occurrence of some blood disorders to cesium-137 contamination.
The death rate from these disorders showed no increase attributable to radiation. The morbidity rate in the uncontaminated region increased at the same rate as that in the contaminated region.
The incidence of childhood leukemia did not change significantly after the accident when compared with the period before 1986.
The incidence of diseases of the oral mucosa and periodontal and dental tissues was almost identical among residents of the contaminated and uncontaminated regions in Belarus.
Global Radiation Patterns
The spread of radioactive contaminates into the atmosphere from the Chernobyl accident was eventually detected all over the world. Events, such as volcano eruptions and nuclear bomb testings, result in major effluent emission that also can be detected with very sensitive equipment.
The risk to the public health of the people in neighboring countries from the nuclear accident at Chernobyl, USSR, has been a primary element in evaluating the magnitude this accident has had on the world. The citizens of eastern Europe and Scandinavia are the most concerned, because their countries received the majority of the exposure in the first week of the accident and thus, their health is at the highest risk.
On Friday, April 25, 1986, as a result of human error during experiments being performed by the staff at Chernobyl, the cooling system failed resulting in the melting of fuel and, of greater importance to the public, the graphite moderator ignited and began the release of what has been approximated as 1900 PBq of activity to the environment (it has been commented that had there been a containment building similar to the ones used in U.S. reactors, this value might have been greatly reduced). The most hazardous isotopes released in this accident are known to Cs-137, I-131, and Sr-90. These isotopes have half-lives sufficiently long to allow them to migrate into the body or, in the case of Iodine, have the tendency to accumulate in the thyroid gland.
The plume from the burning graphite initially traveled in a northwest direction toward Sweden, Finland and eastern Europe, exposing the public to levels up to 100 times the normal background radiation. A very serious concern involves the contamination of grain and dairy products from fallout. This contamination presents the chance for permanent internal contamination. Both Sr-90 and I-131 migrate to vital organs in the body where they are impossible to remove, serving as a constant source of unnecessary radiation and as a cause of cancer or other diseases.
Airborne radioactive effluents can enter the body by air inhalation, absorption through the skin, or food consumption. Exposure immediately following the accident involved air inhalation and absorption through the skin but, this exposure could have been minimized by staying indoors. The greatest threat for the public is from food contamination. In this case, fallout settles on farmland and grazing land. Cattle consume the grass and inadvertently contaminate themselves and their by-products such as milk and meat. In the case of farmland, radioactive dust settles on the crops. If well cleaned, this source of radiation is minimized but, for the people in eastern Europe and Finland, often sanitary conditions are not available on the small family-owned farms.
Radioactive effluents in water offer similar contamination threats from drinking water, fish consumption, and absorption through the skin. Again the greatest threat is from consumption of food. Small fish absorb the effluents through their skin and gills and from ingestion. Radioactive particulates in water are also reconcentrated in the aquatic food chain. The ingestion of fish then results in internal exposure.
The biological effects from radiation vary with dose. The science of health physics recognizes two types of exposure: (1) a single accidental exposure to a high dose of radiation during a short period of time, which is commonly called acute exposure, and which may produce biological effects within a short time after exposure; and (2) long-term, low level overexposure, commonly called continuous or chronic exposure, where the results of the overexposure may not be apparent for years, and which is likely to be the result of improper or inadequate protective measures.
Due to the varying sensitivity of body organs, the effects of acute whole body radiation depend on the magnitude of the dose. At lower levels (<100 rads), changes in the blood count can be expected. White blood cell count is reduced, making the body more susceptible to disease. At the same time there is also a reduction of granulocytes (essential in blooded clotting) and red blood cells. At higher levels destruction of bone marrow, the gastrointestinal system, and under very high intensity radiation, the central nervous system.
Airborne radioactive effluents can enter the body by air inhalation, absorption through the skin, or food consumption. Exposure immediately following the accident involved air inhalation and absorption through the skin but, this exposure could have been minimized by staying indoors. The greatest threat for the public is from food contamination. In this case, fallout settles on farmland and grazing land. Cattle consume the grass and inadvertently contaminate themselves and their by-products such as milk and meat. In the case of farmland, radioactive dust settles on the crops. If well cleaned, this source of radiation is minimized but, for the people in eastern Europe and Finland, often sanitary conditions are not available on the small family-owned farms.
Radioactive effluents in water offer similar contamination threats from drinking water, fish consumption, and absorption through the skin. Again the greatest threat is from consumption of food. Small fish absorb the effluents through their skin and gills and from ingestion. Radioactive particulates in water are also reconcentrated in the aquatic food chain. The ingestion of fish then results in internal exposure.
The biological effects from radiation vary with dose. The science of health physics recognizes two types of exposure: (1) a single accidental exposure to a high dose of radiation during a short period of time, which is commonly called acute exposure, and which may produce biological effects within a short time after exposure; and (2) long-term, low level overexposure, commonly called continuous or chronic exposure, where the results of the overexposure may not be apparent for years, and which is likely to be the result of improper or inadequate protective measures.
Due to the varying sensitivity of body organs, the effects of acute whole body radiation depend on the magnitude of the dose. At lower levels (<100 rads), changes in the blood count can be expected. White blood cell count is reduced, making the body more susceptible to disease. At the same time there is also a reduction of granulocytes (essential in blooded clotting) and red blood cells. At higher levels destruction of bone marrow, the gastrointestinal system, and under very radiationhigh intensity, the central nervous system.
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The Other Report on Chernobyl (TORCH) April 2006
An independent scientific evaluation of the health and environmental effects of the Chernobyl nuclear disaster with critical analyses of recent reports by the International Atomic Energy Agency (IAEA) and the World Health Organisation (WHO).
Summary and Conclusions
On 26 April 2006, twenty years will have passed since the Chernobyl nuclear power plant exploded and large quantities of radioactive gases and particles were spread throughout the
northern hemisphere. While the effects of the disaster remain apparent particularly in Belarus, Ukraine and Russia, where millions of people are affected, Chernobyl’s fallout also seriously contaminated other areas of the world. The disaster not only resulted in an unprecedented release of radioactivity but also a series of unpredicted and serious consequences for the
public and the environment.
The TORCH report aims to provide an independent scientific examination of available data on the release of radioactivity into the environment and subsequent health-related effects of the Chernobyl accident. Thousands of studies have been carried out on the issue but many are only available in Ukrainian or Russian. These constraints inhibit a full international understanding of the impacts of Chernobyl, and the authors draw attention to this difficulty
and to the need for it to be tackled at an official level. It is noted that some scientists from Belarus, Russia and Ukraine are highly critical of official versions of the impacts of the Chernobyl accident.
The Report critically examines recent official reports on the impact of the Chernobyl accident, in particular two reports by the “UN Chernobyl Forum” released by the International Atomic
Energy Agency (IAEA) and the World Health Organisation (WHO) in September 2005 which received considerable attention by the international media.
Many uncertainties surround risk estimates from radiation exposures. The most fundamental is that the effects of very low doses are uncertain. The current theory is that the relationship
between dose and detrimental effect is linear without threshold down to zero dose. In other words, there is no safe level of radiation exposure. However the risk, at low doses, may be supralinear, resulting in relatively higher risks, or sublinear, resulting in relatively lower risks.
Another main source of uncertainty lies in the estimates of internal radiation doses, that is, from nuclides, which are inhaled or ingested. These are an important source of the radiation from Chernobyl’s fallout. Uncertainties in internal radiation risks could be very large, varying in magnitude from factors of 2 (up and down from the central estimate) in the most favorable cases, to 10 or more in the least favourable cases for certain radionuclides.
How Much Radioactivity Was Released?
The World Health Organisation (WHO) has estimated that the total radioactivity from Chernobyl was 200 times that of the combined releases from the atomic bombs dropped on Hiroshima and Nagasaki. The amount of radioactivity released during a radiological event, is called the ‘source term’. It is important because it is used to verify nuclide depositions throughout the northern hemisphere. From these, collective doses and predicted excess illnesses and fatalities can be estimated. Of the cocktail of radionuclides that were released, the fission products iodine-131, caesium-134 and caesium-137 have the most radiological significance. Iodine-131 with its short radioactive half-life of eight days had great radiological impact in the short term because of its doses to the thyroid. Caesium-134 (half-life of 2 years) and caesium-137 (half-life of 30 years) have the greater radiological impacts in the medium and long terms. Relatively small amounts of caesium-134 now remain, but for the first two decades after 1986, it was an important contributor to doses.
The Other Report on Chernobyl (TORCH) April 2006
An independent scientific evaluation of the health and environmental effects of the Chernobyl nuclear disaster with critical analyses of recent reports by the International Atomic Energy Agency (IAEA) and the World Health Organisation (WHO).
Summary and Conclusions
On 26 April 2006, twenty years will have passed since the Chernobyl nuclear power plant exploded and large quantities of radioactive gases and particles were spread throughout the
northern hemisphere. While the effects of the disaster remain apparent particularly in Belarus, Ukraine and Russia, where millions of people are affected, Chernobyl’s fallout also seriously contaminated other areas of the world. The disaster not only resulted in an unprecedented release of radioactivity but also a series of unpredicted and serious consequences for the
public and the environment.
The TORCH report aims to provide an independent scientific examination of available data on the release of radioactivity into the environment and subsequent health-related effects of the Chernobyl accident. Thousands of studies have been carried out on the issue but many are only available in Ukrainian or Russian. These constraints inhibit a full international understanding of the impacts of Chernobyl, and the authors draw attention to this difficulty
and to the need for it to be tackled at an official level. It is noted that some scientists from Belarus, Russia and Ukraine are highly critical of official versions of the impacts of the Chernobyl accident.
The Report critically examines recent official reports on the impact of the Chernobyl accident, in particular two reports by the “UN Chernobyl Forum” released by the International Atomic
Energy Agency (IAEA) and the World Health Organisation (WHO) in September 2005 which received considerable attention by the international media.
Many uncertainties surround risk estimates from radiation exposures. The most fundamental is that the effects of very low doses are uncertain. The current theory is that the relationship
between dose and detrimental effect is linear without threshold down to zero dose. In other words, there is no safe level of radiation exposure. However the risk, at low doses, may be supralinear, resulting in relatively higher risks, or sublinear, resulting in relatively lower risks.
Another main source of uncertainty lies in the estimates of internal radiation doses, that is, from nuclides, which are inhaled or ingested. These are an important source of the radiation from Chernobyl’s fallout. Uncertainties in internal radiation risks could be very large, varying in magnitude from factors of 2 (up and down from the central estimate) in the most favorable cases, to 10 or more in the least favourable cases for certain radionuclides.
How Much Radioactivity Was Released?
The World Health Organisation (WHO) has estimated that the total radioactivity from Chernobyl was 200 times that of the combined releases from the atomic bombs dropped on Hiroshima and Nagasaki. The amount of radioactivity released during a radiological event, is called the ‘source term’. It is important because it is used to verify nuclide depositions throughout the northern hemisphere. From these, collective doses and predicted excess illnesses and fatalities can be estimated. Of the cocktail of radionuclides that were released, the fission products iodine-131, caesium-134 and caesium-137 have the most radiological significance. Iodine-131 with its short radioactive half-life of eight days had great radiological impact in the short term because of its doses to the thyroid. Caesium-134 (half-life of 2 years) and caesium-137 (half-life of 30 years) have the greater radiological impacts in the medium and long terms. Relatively small amounts of caesium-134 now remain, but for the first two decades after 1986, it was an important contributor to doses.
Most of the other radionuclides will have completely decayed by now. Over the next few decades, interest will continue to focus on caesium-137, with secondary attention on strontium-90, which is more important in areas nearer Chernobyl. Over the longer term
(hundreds to thousands of years), the radionuclides of continuing interest will be the activation products, including the isotopes of plutonium, neptunium and curium. However, overall doses from these activation products are expected to remain low, compared with the doses from caesium-137.
The authors have reassessed the percentages of the initial reactor inventories of caesium-137 and iodine-131 which were released to the environment.
During the 10 day period of maximum releases from Chernobyl, volatile radionuclides were continuously discharged and dispersed across many parts of Europe and later the entire northern hemisphere. For example, relatively high fallout concentrations were measured at Hiroshima in Japan, over 8,000 km from Chernobyl.
Rainfall resulted in markedly heterogeneous depositions of fallout throughout Europe and the northern hemisphere. Most ejected fuel was deposited in areas near the reactor with wide variations in deposition density, although some fuel hot particles were transported thousands of kilometres. The largest concentrations of volatile nuclides and fuel particles occurred in Belarus, Russia and Ukraine. But more than half of the total quantity of Chernobyl’s volatile inventory was deposited outside these countries.
(hundreds to thousands of years), the radionuclides of continuing interest will be the activation products, including the isotopes of plutonium, neptunium and curium. However, overall doses from these activation products are expected to remain low, compared with the doses from caesium-137.
The authors have reassessed the percentages of the initial reactor inventories of caesium-137 and iodine-131 which were released to the environment.
During the 10 day period of maximum releases from Chernobyl, volatile radionuclides were continuously discharged and dispersed across many parts of Europe and later the entire northern hemisphere. For example, relatively high fallout concentrations were measured at Hiroshima in Japan, over 8,000 km from Chernobyl.
Rainfall resulted in markedly heterogeneous depositions of fallout throughout Europe and the northern hemisphere. Most ejected fuel was deposited in areas near the reactor with wide variations in deposition density, although some fuel hot particles were transported thousands of kilometres. The largest concentrations of volatile nuclides and fuel particles occurred in Belarus, Russia and Ukraine. But more than half of the total quantity of Chernobyl’s volatile inventory was deposited outside these countries.
Extensive surveying of Chernobyl’s caesium-137 contamination was carried out in the 1990s under the auspices of the European Commission. The results indicate that about 3,900,000 km of Europe was contaminated by caesium-137 (above 4,000 Bq/m) which is 40% of the surface area of Europe. Curiously, this latter figure does not appear to have been published and, certainly has never reached the public’s consciousness in Europe. Of the total contaminated area, 218,000 km or about 2.3% of Europe’s surface area has been contaminated to higher levels (greater than 40,000 Bq/m2 caesium-137). This is the area cited by IAEA/WHO and UNSCEAR, which shows that they have been remarkably selective in their reporting. In terms of surface area, Belarus and Austria were most affected by higher levels of contamination However, other countries were seriously affected; for example, more than 5% of Ukraine, Finland and Sweden were contaminated to high levels (> 40,000 Bq/mcaesium-137). More than 80% of Moldova, the European part of Turkey, Slovenia, Switzerland, Austria and the Slovak Republic were contaminated to lower levels (> 4,000 Bq/m2 caesium-137). 44% of Germany and 34% of the UK were similarly affected.
In terms of total deposition of caesium-137, Russia, Belarus and Ukraine received the highest amounts of fallout while former Yugoslavia, Finland, Sweden, Bulgaria, Norway, Rumania, Germany, Austria and Poland each received more than one petabecquerel (10Bq or one million billion becquerels) of caesium-137, a very large amount of radioactivity.
Restrictions on Food Still in Place
In many countries, restriction orders remain in place on the production, transportation and consumption of food still contaminated by Chernobyl fallout.
• In the United Kingdom restrictions remain in place on 374 farms covering 750 km and 200,000 sheep.
• In parts of Sweden and Finland, as regards stock animals, including reindeer, in natural and near-natural environments.
• In certain regions of Germany, Austria, Italy, Sweden, Finland, Lithuania and Poland wild game (including boar and deer), wild mushrooms, berries and carnivore fish from lakes reach levels of several thousand Bq per kg of caesium-137.
• In Germany, caesium-137 levels in wild boar muscle reached 40,000 Bq/kg. The average level is 6,800 Bq/kg, more than ten times the EU limit of 600 Bq/kg.
The European Commission does not expect any change soon. It has stated:
“The restrictions on certain foodstuffs from certain Member States must therefore continue to be maintained for many years to come.”
The IAEA/WHO reports do not mention the existing comprehensive datasets on European contamination. No explanation is given for this omission. Moreover, the IAEA/WHO reports do not discuss deposition and radiation doses in any country apart from Belarus, Ukraine and Russia. Although heavy depositions certainly occurred there, the omission of any examination of Chernobyl fallout in the rest of Europe and the northern hemisphere is questionable.
The Health Impacts – So Far…
The immediate health impact of the Chernobyl accident was acute radiation sickness in 237 emergency workers, of whom 28 died in 1986 and a further 19 died between 1987 and 2004. More premature deaths may occur amongst this group.
The long-term consequences of the accident remain uncertain. Exposure to ionising radiation can induce cancer in almost every organ in the body. However, the time interval between the exposure to radiation and the appearance of cancer can be 50 to 60 years or more. The total number of cancer deaths from Chernobyl most likely will never be fully known. However the TORCH Report makes predictions of the numbers of excess cancer deaths from published collective doses to affected populations.
Thyroid Cancer
Up to 2005, about 4,000 cases of thyroid cancer occurred in Belarus, Ukraine and Russia in those aged under 18 at the time of the accident. The younger the person exposed, the greater
the subsequent risk of developing thyroid cancer.
Thyroid cancer is induced by exposures to radioactive iodine. It is estimated that more than half the iodine-131 from Chernobyl was deposited outside the former Soviet Union. Possible increases in thyroid cancer have been reported in the Czech Republic and the UK, but more research is needed to evaluate thyroid cancer incidences in western Europe. Depending on the risk model used, estimates of future excess cases of thyroid cancer range between 18,000 and 66,000 in Belarus alone. Of course, thyroid cancers are also expected to occur in Ukraine and Russia. The lower estimate assumes a constant relative risk for 40 years after exposure; the higher assumes a constant relative risk over the whole of life. Recent evidence from the Japanese atomic bomb survivors suggests that the latter risk projection may be more realistic.
Leukaemia
In terms of total deposition of caesium-137, Russia, Belarus and Ukraine received the highest amounts of fallout while former Yugoslavia, Finland, Sweden, Bulgaria, Norway, Rumania, Germany, Austria and Poland each received more than one petabecquerel (10Bq or one million billion becquerels) of caesium-137, a very large amount of radioactivity.
Restrictions on Food Still in Place
In many countries, restriction orders remain in place on the production, transportation and consumption of food still contaminated by Chernobyl fallout.
• In the United Kingdom restrictions remain in place on 374 farms covering 750 km and 200,000 sheep.
• In parts of Sweden and Finland, as regards stock animals, including reindeer, in natural and near-natural environments.
• In certain regions of Germany, Austria, Italy, Sweden, Finland, Lithuania and Poland wild game (including boar and deer), wild mushrooms, berries and carnivore fish from lakes reach levels of several thousand Bq per kg of caesium-137.
• In Germany, caesium-137 levels in wild boar muscle reached 40,000 Bq/kg. The average level is 6,800 Bq/kg, more than ten times the EU limit of 600 Bq/kg.
The European Commission does not expect any change soon. It has stated:
“The restrictions on certain foodstuffs from certain Member States must therefore continue to be maintained for many years to come.”
The IAEA/WHO reports do not mention the existing comprehensive datasets on European contamination. No explanation is given for this omission. Moreover, the IAEA/WHO reports do not discuss deposition and radiation doses in any country apart from Belarus, Ukraine and Russia. Although heavy depositions certainly occurred there, the omission of any examination of Chernobyl fallout in the rest of Europe and the northern hemisphere is questionable.
The Health Impacts – So Far…
The immediate health impact of the Chernobyl accident was acute radiation sickness in 237 emergency workers, of whom 28 died in 1986 and a further 19 died between 1987 and 2004. More premature deaths may occur amongst this group.
The long-term consequences of the accident remain uncertain. Exposure to ionising radiation can induce cancer in almost every organ in the body. However, the time interval between the exposure to radiation and the appearance of cancer can be 50 to 60 years or more. The total number of cancer deaths from Chernobyl most likely will never be fully known. However the TORCH Report makes predictions of the numbers of excess cancer deaths from published collective doses to affected populations.
Thyroid Cancer
Up to 2005, about 4,000 cases of thyroid cancer occurred in Belarus, Ukraine and Russia in those aged under 18 at the time of the accident. The younger the person exposed, the greater
the subsequent risk of developing thyroid cancer.
Thyroid cancer is induced by exposures to radioactive iodine. It is estimated that more than half the iodine-131 from Chernobyl was deposited outside the former Soviet Union. Possible increases in thyroid cancer have been reported in the Czech Republic and the UK, but more research is needed to evaluate thyroid cancer incidences in western Europe. Depending on the risk model used, estimates of future excess cases of thyroid cancer range between 18,000 and 66,000 in Belarus alone. Of course, thyroid cancers are also expected to occur in Ukraine and Russia. The lower estimate assumes a constant relative risk for 40 years after exposure; the higher assumes a constant relative risk over the whole of life. Recent evidence from the Japanese atomic bomb survivors suggests that the latter risk projection may be more realistic.
Leukaemia
The evidence for increased leukaemias is less clear. Some evidence exists of increased leukaemia incidence in Russian cleanup workers and residents of highly contaminated areas in Ukraine. Some studies appear to show an increased rate of childhood leukaemia from Chernobyl fallout in West Germany, Greece and Belarus.
Other Solid Cancers
Most solid cancers have long periods between exposure and appearance of between 20 and 60 years. Now, 20 years after the accident, an average 40% increased incidence in solid cancer has already been observed in Belarus with the most pronounced increase in the most contaminated regions. The 2005 IAEA/WHO reports acknowledge preliminary evidence of an increase in the incidence of pre-menopausal breast cancer among women exposed at ages lower than 45 years.
Heritable Effects It is well known that radiation can damage genes and chromosomes. However the relationship between genetic changes and the development of future disease is complex and the relevance of such damage to future risk is often unclear. On the other hand, a number of recent studies have examined genetic damage in those exposed to radiation from the Chernobyl accident.
Studies in Belarus have suggested a twofold increase in the germline minisatellite mutation rate. Analysis of a cohort of irradiated families from Ukraine confirmed these findings. However the clinical symptoms which may result from these changes remain unclear.
Mental Health and Psychosocial Effects
While seeming to downplay other effects, the recent IAEA/WHO reports clearly recognise the vast mental, psychological and central nervous system effects of the Chernobyl disaster: “The mental health impact of Chernobyl is the largest public health problem caused by the accident. The origins of these psychosocial effects are complex, and are related to several factors, including anxiety about the possible effects of radiation, changes in lifestyle – particularly
diet, alcohol and tobacco – victimisation, leading to a sense of social exclusion, and stress associated with evacuation and resettlement. It is therefore difficult to state exactly how much of these symptoms are directly related to Chernobyl related radiation exposures.
Conclusions
The full effects of the Chernobyl accident will most certainly never be known. However, 20 years after the disaster, it is clear that it is far greater than implied by official estimates. Our overall conclusion is that the unprecedented extent of the disaster and its long-term global environmental, health and socio-economic consequences should be fully acknowledged and taken into account by governments when considering their energy policies.
In summary, the main conclusions of the Report are:
• about 30,000 to 60,000 excess cancer deaths are predicted, 7 to 15 times greater than IAEA/WHO’s published estimate of 4,000
• predictions of excess cancer deaths strongly depend on the risk factor used
• predicted excess cases of thyroid cancer range between 18,000 and 66,000 depending on the risk projection model
• other solid cancers with long latency periods are beginning to appear 20 years after the accident
• Belarus, Ukraine and Russia were heavily contaminated, but more than half of Chernobyl’s fallout was deposited outside these countries
• fallout from Chernobyl contaminated about 40% of Europe’s surface area
• collective dose is estimated to be about 600,000 person Sv, more than 10 times greater than official estimates
• about 2/3rds of Chernobyl’s collective dose was distributed to populations outside Belarus, Ukraine and Russia, especially to western Europe
• Caesium-137 released from Chernobyl is estimated to be about a third higher than official estimates.
Our verdict on the two recent IAEA/WHO studies on Chernobyl’s health and environmental effects respectively is mixed. On the one hand, we recognise that the reports contain comprehensive examinations of Chernobyl’s effects in Belarus, Ukraine and Russia. On the other hand, the reports are silent on Chernobyl’s effects outside these countries. Although areas of Belarus, Ukraine and Russia were heavily contaminated, most of Chernobyl’s fallout
was deposited outside these countries. Collective doses from Chernobyl’s fallout to populations in the rest of the world, especially in western Europe, are twice those to populations in Belarus, Ukraine and Russia. This means that these populations will suffer
twice as many predicted excess cancer deaths, as the populations in Belarus, Ukraine and Russia.
The failure to examine Chernobyl’s effects in the other countries does not lie with the scientific teams but within the policy-making bodies of IAEA and WHO. In order to rectify this omission, we recommend that the WHO, independently of the IAEA, should commission a report to examine Chernobyl’s fallout, collective doses and effects in the rest of the world, particularly in western Europe.
diet, alcohol and tobacco – victimisation, leading to a sense of social exclusion, and stress associated with evacuation and resettlement. It is therefore difficult to state exactly how much of these symptoms are directly related to Chernobyl related radiation exposures.
Conclusions
The full effects of the Chernobyl accident will most certainly never be known. However, 20 years after the disaster, it is clear that it is far greater than implied by official estimates. Our overall conclusion is that the unprecedented extent of the disaster and its long-term global environmental, health and socio-economic consequences should be fully acknowledged and taken into account by governments when considering their energy policies.
In summary, the main conclusions of the Report are:
• about 30,000 to 60,000 excess cancer deaths are predicted, 7 to 15 times greater than IAEA/WHO’s published estimate of 4,000
• predictions of excess cancer deaths strongly depend on the risk factor used
• predicted excess cases of thyroid cancer range between 18,000 and 66,000 depending on the risk projection model
• other solid cancers with long latency periods are beginning to appear 20 years after the accident
• Belarus, Ukraine and Russia were heavily contaminated, but more than half of Chernobyl’s fallout was deposited outside these countries
• fallout from Chernobyl contaminated about 40% of Europe’s surface area
• collective dose is estimated to be about 600,000 person Sv, more than 10 times greater than official estimates
• about 2/3rds of Chernobyl’s collective dose was distributed to populations outside Belarus, Ukraine and Russia, especially to western Europe
• Caesium-137 released from Chernobyl is estimated to be about a third higher than official estimates.
Our verdict on the two recent IAEA/WHO studies on Chernobyl’s health and environmental effects respectively is mixed. On the one hand, we recognise that the reports contain comprehensive examinations of Chernobyl’s effects in Belarus, Ukraine and Russia. On the other hand, the reports are silent on Chernobyl’s effects outside these countries. Although areas of Belarus, Ukraine and Russia were heavily contaminated, most of Chernobyl’s fallout
was deposited outside these countries. Collective doses from Chernobyl’s fallout to populations in the rest of the world, especially in western Europe, are twice those to populations in Belarus, Ukraine and Russia. This means that these populations will suffer
twice as many predicted excess cancer deaths, as the populations in Belarus, Ukraine and Russia.
The failure to examine Chernobyl’s effects in the other countries does not lie with the scientific teams but within the policy-making bodies of IAEA and WHO. In order to rectify this omission, we recommend that the WHO, independently of the IAEA, should commission a report to examine Chernobyl’s fallout, collective doses and effects in the rest of the world, particularly in western Europe.
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