Chernobyl: Five years of disaster

Weak Points in Nuclear Power Plants

All types of nuclear power plants have their weak points, as is apparent from a study instigated by Greenpeace and carried out by the German Gruppe Okologie. After the accident, Chernobyl was described as extremely bad. The director of the nuclear power plant at Dodewaard, in the Netherlands, gave the impression that there was no safety containment present at all in the Chernobyl power plant, while the safety of the Dodewaard power plant was painted very favorably. The lack of any containment of steel and cement was especially seen as a serious defect. But it soon became apparent that in Western Europe there are more than 30 nuclear power plants without this sort of containment, among others the one in Dodewaard. This is glossed over by saying that "Dodewaard is only a very small fish as far as power plants go". By the end of 1986 it became clear that the discussion about the lack of containments was actually leading nowhere. The power of the explosion at the time of the accident was so great that any containment existing in Western nuclear power plants would have collapsed anyway.

During the first few months after the accident, when more information became available, it became apparent that Chernobyl had the following safety systems:

1. If one of the pressure tubes gives out, the steam and any hydrogen that has formed are collected in a steel enclosed system, able to withstand any over-pressure: through two pipes any overpressure can be transported to a condensation pool filled with water
2. The space containing the main circulation pump and the emergency cooling system can resist a high amount of overpressure (of 4.5 bar)
3. The steam separators are situated in a cement space able to resist overpressure
4. The organization and control system is carried out plurally, and for the main part automated, consequently it is considerably more modern than was first thought.

One of the problems with the Chernobyl design is the way in which it functions at a low level, when only the smallest amount of electricity that can be maximally delivered is actually produced. When the amount is slightly increased, the power plant is inclined to press on to higher production. In technical terms this is called "positive void coefficient". The chance of an increase in production ability which is difficult to control, is for instance, much lower in the Dutch nuclear power plants, but cannot be totally excluded.

However, there are Western nuclear power reactors which also have a positive void coefficient, namely the Canadian CANDU reactors and the breeder reactors. Although this coefficient was criticized in the Soviet reactors, advocates of nuclear energy did not think it necessary to plead for the closure of the Canadian nuclear plants. However, this was an argument used by the Dutch government for not choosing the Canadian design when it was planning new nuclear power plants in 1990.

After the nuclear accident, the suggestion was put forward that the disaster could have been averted if the control rods had been placed between the fuel elements more quickly. Western advocates of nuclear energy said that the lack of a scram system was a very important mistake; in the Chernobyl type the control rods take 20 seconds to get to the extreme position, while in Western nuclear plants this takes only one second. With a scram system, the temperature in the power plant changes quickly. At the end of 1989, it appeared that the pressure tubes in Chernobyl were not resistant to such fast temperature changes, therefore a slower scram system had been purposely chosen. In a study ordered by the US Department of Energy, the US research bureau EG&G even comes to the conclusion that the accident could have been avoided if the operators had not tried to put the control rods into place.

The Disaster Power Plant Made Operational Too Fast

At the time of the accident there were four nuclear power reactors in operation at the Chernobyl plant, each with a capacity of 1000 megawatts. Two more were under construction. These reactors, of the type RBMK (also called Light-Water-Cooled, Graphite-Moderated Reactors, or LWGRs), use light water as a coolant and graphite as a moderator.

In 1972 there was a discussion in Kiev about the type of nuclear plant to be built at Chernobyl. Chernobyl's director, Bryukhanov, supported construction of Pressurized Water Reactors (PWRs). He informed the Ukraine Minister of Energy, Aleksei Makukhin, that an RBMK releases forty times more radiation than a PWR. However, the scientist Alekzandrov opposed this, saying that the RBMK-1000 was not only the safest reactor, it produced the cheapest electricity as well. For this reason it was decided to build the RBMK pressure tube reactors.

The construction of Unit 4 at Chernobyl was completed by December 1983. On 21 December a press report was released which stated that the previous day the nuclear power plant had become operational. This news was reported by the media on 22 December, a festive day for workers in the energy industry. In the Soviet Union it is customary for all sections of public employment to have their own special day, when they receive public acclaim for their work and are given extra bonuses. That the production of electricity started on 20 December is quite remarkable, because usually there is a time lapse of about six months between the completion of the construction and the plant becoming operational. All the components have to be tested before the actual production process is started. But, in Unit 4 at Chernobyl there was a celebration in March 1984 (only three months later) to mark the fact that already one million kilowatt hours had been produced, even though at that time not all the components had been thoroughly tested.

One of the tests incompletely carried out was on the functioning of the turbine in the case of a defect. If a defect is present, the turbine should then slow down, but continue to produce electricity. This electricity is necessary to work the circulation pump and control rods, and to provide lighting for the control room and control panel. This supply of electricity is essential for the safety of the reactor, and on no account should it fail.

Because it takes twenty seconds for the control rods to reach their most extreme position in the case of a defect, it is of vital importance to know whether the turbine can produce the necessary electricity for those twenty seconds, until the emergency generator is able to take over the supply of electricity. This test was carried out on the night of 25 - 26 April 1986, and was the cause of the disaster.

This test should have been carried out before the power plant was put into operation. In actual fact, such a test was carried out earlier - but failed. This became apparent in July and August 1987 during the trial of the six people held to be responsible for Chernobyl. The judges' verdict states that on 31 December 1983, director Bryukhanov signed a document declaring that all the tests had been carried out successfully.

On this subject Zhores Medvedev noted that it is common practice in the Soviet Union for people to declare an industrial project to be ready for operation on the under-standing that any problems will be solved as quickly as possible. In this way, the production plan already set can still be met. Besides which, not signing the declaration on 31 December 1983 would have resulted in thousands of employees missing their chances of bonuses and other extras. This concerns bonuses of up to three months salary extra. During the above mentioned trial, it became apparent that in the period up to 1985 the turbine had been tested, but without results. The question is still why the test was not repeated again immediately, but had to be left until April 1986, even though the power plant was to be shut down shortly afterwards for repairs. On the basis of the available information Medvedev concludes that a safety problem had been discovered that necessitated making use of the first possible occasion for testing. Also, a team of experts from Moscow had been sent to Chernobyl.

Shortly after the accident, the operators were blamed for allowing the test to take place. The authorities wanted nothing to do with it. However, it is obvious that they must have known about the problems. Nuclear energy is under direct control of the Ministry of Energy and Electricity in the Soviet Union. Chernobyl was controlled by the Ukrainian department of the Ministry, which makes it all the more unlikely that the authorities were ignorant of the planned experiment.

(Un)reliable Information

In April 1985 the Minister of Energy, Anatoly Mayorets, decreed that information on any adverse effects caused by the functioning of the energy industry on employees, inhabitants and environment, were not suitable for publication by newspapers, radio or television. On 18 July 1986, shortly after the Chernobyl accident, this same minister forbade his civil servants from telling the truth about Chernobyl to the media.

From 26 April until 6 May 1986, journalists were not welcome in Chernobyl. After 6 May, Russian journalists were allowed to tell stories of the "heroic fight against radiation", but without giving any technical details. The 1987 trial of the people held responsible for the accident was not public there was only a summary of the trial published. Seen in this light, it seems surprising that the Soviets gave such extensive information about the accident during an international congress held in Vienna in August 1986. This would point to a struggle within the power systems. However, from further analysis it becomes clear that a great deal of data necessary for testing the reliability of the Soviet calculations was not available. Medvedev even calls the information given misleading. Nor were all the Soviets happy with the way things were handled.

Valery Legasov was the head of the Soviet delegation presenting the research report to the congress in Vienna. Legasov was the director of the Kurchatov Institute for Nuclear Energy, where the RBMK reactors were designed. He was also chairman of the scientific team sent to Chernobyl immediately after the accident on 26 April 1986. Two years later, on 27 April 1988, Legasov committed suicide. He left behind his memoirs in which he expresses his anger and despair about the safety of nuclear energy in the Soviet Union. He wrote that he wanted to study the safety problems of the RBMK reactors, and for this reason was opposed by people who said there were no problems. Legasov also wrote that there was a certain inevitability in working towards the accident at Chernobyl.

It remains uncertain whether the information on the course of the accident is completely reliable. In 1987, five possible courses of events leading up to the accident were put forward. However, the following account is the one generally accepted.

The Disaster

Friday 25 April.
13.05 hours
Preparations for the turbine test begin. For this test, the plant's capacity must be reduced and for this reason one turbine is turned off.

14.00 hours
The controller of the Ukraine electricity network requests that the test be delayed. All electricity from Unit 4 is necessary. It is not clear why it was not predictable beforehand that work would have to continue all through Friday afternoon in order to achieve the production planned for April.

16.00 hours
The day shift leaves. The members of this shift have been given information about the test during the previous days, and know about the entire procedure. A special team of electronic engineers is present.

23.10 hours
Preparations for the test start again. The ten hour delay has a large number of consequences. Firstly, the team of engineers is tired. Secondly, during the test, the evening shift is replaced by the night shift. This shift has fewer experienced operators, besides which they were not prepared for the test. Achier Razachkov, - Yuri Tregub and A. Uskov are the operators who were responsible for carrying out the test earlier in the day: later in interviews they declared that test procedures were only explained to the day and evening shifts. Yuri Tregub decides to stay and help the night shift.

Saturday 26 April.
01.00 hours
During preparations for the test, the operators have difficulty keeping the capacity of the nuclear plant stable. While doing this they make six important mistakes.

1. The control rods which can stop the reactor are raised higher than regulations permit. Operator Uskov of the day shift said later that he would have done the same. He said: "We often don't see the need to follow the instructions to the letter, because rules are often infringed all around us." As well as this, he pointed to the fact that during training it was repeated over and over again that "a nuclear power plant cannot explode". Operator Kazachkov said: "We have often had fewer control rods than were required, and nothing ever happened. No explosion, everything just went on as normal."
2. The plant's capacity decreases to below the safe level. Because of this the core becomes unstable. Preparations for the test should have been stopped by now. It should have been obvious that all attention should be given to measures for regaining the plant's stability.
3. In order to raise the capacity, an extra circulation pump is turned on. Because of the strong cooling down, the pressure falls, thus reducing the reactor's capacity rather than increasing it. Normally at this stage the scram system should start working, but in order to still be able to carry out the test, this system is turned off.
4. The automatic emergency shut-down system is turned off in order to prevent the reactor stopping itself.
5. The systems to prevent the' water level decreasing too much and the temperature of the fuel elements becoming too high are also turned off.
6. Finally, the emergency cooling system is turned off to prevent it working during the test.

1.23.04 hours
The real test now begins. The power plant's capacity suddenly increases unexpectedly.

1.23.40 hours
Leonid Toptunov, responsible for the control rods, presses a special button for an emergency shutdown. The test has been going on for 36 seconds.

1.23.44 hours
The control rods start to descend, but shocks can be felt. The operators see that the control rods have become stuck. The fuel tubes have become deformed because of the large increase in the steam pressure.

1.24.00 hours
The test has now been going on for 56 seconds. Pressure in the reactor is now so high that the fuel elements burst and small particles land in the cooling water. The cooling water turns into steam and pressure in the tubes increases: they burst.

The 1000 tonne lid above the fuel elements is lifted: the first explosion. The release of radiation starts. Air gets into the reactor. There is enough oxygen to start a graphite fire. The metal of the fuel tubes reacts to the water. This is a chemical reaction which produces hydrogen, and this hydrogen explodes: the second explosion. Burning debris flies into the air and lands on the roof of Chernobyl Unit 3. (There was barely any attention paid to this hydrogen explosion in the Soviet report about the accident. In studies com-missioned by the US government, however, it was concluded that the second explosion was of great significance, and that the original explanation of the accident was incorrect. Richard Wilson of the Harvard University in the US said this second explosion was small nuclear explosion.)

The head of the night shift, Alexander Akinhov, and the engineer responsible for industrial management, Anatoly Diatlov, do not believe that an accident has taken place. When somebody claims the core has exploded, they send out operators to examine the core. These people are killed by radiation. On hearing the report that the reactor has been destroyed Akimov cries out, "The reactor is OK, we have no problems."

Akimov and Diatlov, assisted by manager Bryukhanov and engineer N.Fomin, keep ordering the operators to add more cooling water. They remain convinced that there is nothing wrong. Akimov and Toptunov, who was responsible for the control rods, both died of radiation illness. Diatlov and Fomin were both sentenced to ten years imprisonment for infringement of the safety regulations. However, at the end of 1990 they were both released.

CHAPTER 2: THE BATTLE OF CHERNOBYL

Radioactive Fires

Saturday 26 April 1986.
Unit 4 of the Nuclear power plant at Chernobyl explodes. Debris flies into the air and lands on the roof of Unit 3 which is right next to the exploded Unit 4. The units share a communal machine turbine hall with a roof of bitumen, a flammable material. Thirty fires develop. The fact that the accident happens at night has one great advantage: in the daytime, 2000 people are working on the construction of Chernobyl Units 5 and 6. These people are now at home.

01.25 hours
The fire alarm rings at the local fire station. Meanwhile more people are killed: Valery Khodomchuk, who is working in the reactor hall and is blasted out by the force of the explosion, and Vladimir Shashenka, who is close to the reactor hall. The nuclear plant's fire fighters arrive with three fire engines. The leader, Lieutenant Pravik, quickly realizes that his team is too small and asks the fire brigades from Pripyat, the town of Chernobyl and the entire area of Kiev for their assistance. Pravik and his team climb onto the roof of the machine hail and start their attempts to extinguish the fire. The fire brigade, from Pripyat arrives minutes later and fights the fires in the reactor building. Pravik and several firemen from Pripyat die later of radiation illness.

01.45 hours
New teams of fire fighters from the area arrive. They know nothing about the danger of radiation, have no protective clothing or dosimeters. One of the fire engine drivers, Grigory Khmel said later: "We arrived at ten minutes to two in the morning. We saw graphite lying everywhere. I kicked a bit of it. Another fireman picked up a piece and said 'hot'. Neither of us had any idea of radiation. My colleagues Kolya, Pravik and others all went up the ladder to the roof of the reactor. I never saw them again."

02.15 hours
The Pripyat department of the Ministry of Home Affairs calls a crisis meeting. It is decided to organize a road block in order to prevent cars from entering or leaving the town. Police assistance is requested. Thousands of police arrive; and, as with the fire fighters, they have no knowledge of radiation, no dosimeters or protective clothing. Later, in 1988, it is admitted that a total of 16,500 police were deployed. Of those, 57 people developed chronic radiation illness, 1500 of them suffer from chronic respiratory problems and 4000 suffer from other symptoms.

03.12 hours
An alarm signal goes off at the army headquarters in the central area of the Soviet Union at 03.12 hours. General Pikalov decides to send in troops to help. They arrive in Kiev at 14.00 hours. These are the first people to arrive well prepared for their task. About the same time, the responsible authorities such as the Energy Minister, A. Mayorets, hear that an accident has occurred, but are led to believe it is a small defect.

05.00 hours
In spite of the fires, Chernobyl Unit 3 is not closed down until five o'clock am.

06.35 hours
No fewer than 37 fire brigades, with a total of 186 fire fighters, have been called in to extinguish all the fires; the fire in the reactor could not actually be extinguished. The importance of the deployment of these fire fighters cannot be emphasized enough. The roof of Unit 3 caught fire immediately, which meant that this reactor could have been seriously damaged as well. The nuclear plants' machine hell is also connected to Units 1 and 2. An explosion in the machine hall could have led to the destruction of all four Chernobyl reactors. An explosion was only averted by spraying nitrogen at the last minute. Four of the eight people who did this died shortly afterwards.

20.00 hours
A government committee is established, led by Valery Legasov; at eight o'clock in the evening the committee arrives in the area. They are surprised by the bits of graphite they see lying around. None of them suspect a graphite fire.

Sunday 27 April.
General Pikalov sets out at seven o'clock in a truck fitted out with radiation apparatus. He rams through the closed gates and stops at the nuclear power plant to measure the radiation. He establishes that the graphite in the reactor is burning, and that an enormous amount of radiation and heat is being given off. Shortly afterwards - the government in Moscow is warned. The government committee discusses the necessity of evacuation of the nearby town of Pripyat. Everyone supports evacuation except Professor A.L.Ilyin, chairman of the Soviet Council for Radiation Protection. He thinks the radiation situation will improve. The operation of Units 1 and 2 had already been stopped at 01.13 and 02.13 hours, twenty-four hours after the start of the accident. By now, as it is understood that graphite is burning and that radiation is being released, further steps are taken. Firstly, extinguishing water is added. This is a dangerous mistake. Due to the high temperature, the water separates into hydrogen and oxygen, and this mixture of gas can explode; an explosion like this releases heat. Thus, the- fire is not extinguished, but fanned by the water. After three fruitless attempts to extinguish the fire, the authorities decide to throw sand, lead and boron carbide onto the reactor from helicopters. Boron carbide can absorb neutrons and stop the uranium fissioning. Lead absorbs heat, enabling the temperature to drop. Sand is to extinguish the fires. Between 27 April and 1 May, 5000 tonnes of material are thrown onto the fire.

Monday 28 April.
Shortly after eight o'clock in the evening, Dutch time, with a short press report from the Soviet press bureau Tass, mention is made of an accident and the disaster is made known to the world.

Thursday 1 May.
In Gomel, Kiev and other towns around Chernobyl, Labor Day is celebrated. The authorities claim the situation is stable. Later it becomes clear that what they really meant was that the radiation release has gradually lessened since 26 April. But, the amount of radiation -is still enormous, besides which, the wind has changed direction and is now blowing in the direction of Kiev. The material thrown onto the plant does not completely extinguish the fire and in fact generates a rise in temperature. Scientists and engineers become aware of a new danger. The hot reactor core could melt into the cement and end up in the water reservoir underneath. A steam explosion would follow, even more powerful than the first explosion.

Friday 2 May.
More and more radioactivity is released into the area. Fire fighters start pumping the water out of the storage reservoir underneath the reactor, a long and dangerous task, not completed until 8 May. As a reward, the fire fighters receive 1000 rubles each (approximately 2000 US dollars according to the official rate of exchange).

Sunday 4 May.
A second step taken to prevent a steam explosion is that of making holes in the earth under the reactor. Fluid nitrogen is pumped into them to freeze the earth.

Monday 5 May.
To start with, there is a great deal of radioactivity released, nearly as much as on 26 April However, the release later stops almost entirely. No acceptable explanation has yet been found for this fact. According to Grigory Medvedev, who was a member of the government committee, the fire was extinguished because the graphite had burnt up. The radioactive release was there-fore not stopped by all the measures taken, but simply by the lack of graphite. The conclusion must be that the accident in Chernobyl was very serious, but not as serious as it could have been if the hot fuel had melted through the cement foundations and caused a steam explosion, or if all four Chernobyl reactors had been wrecked.

The Sarcophagus

During the following months a plan is developed to construct a building around the wrecked reactor. This building is called "the sarcophagus" (or grave tomb). It is a construction 70 meters high in which 300,000 cubic meters of cement and 6000 tonnes of steel have been processed. The inside is made of metal, and around this there is a cement wall one meter thick. A partition is built between Unit 4 and its neighboring reactor, Unit 3, because that unit is already back in operation. In October 1986, the sarcophagus is completed and the radioactive release stopped.

During construction, employees suffer from radiation illness. To reduce the radiation doses they receive, they are sometimes only allowed to work for five seconds. Anyone who absorbs more than 250 milliSieverts has to stop work on the Sarcophagus altogether. One problem is that the sarcophagus cannot be built on a sturdy foundation because of the high amount of radiation this would give the workers; another problem is the effect of heat and radiation on the building. There is radioactive material blowing about, and an attempt has been made to bind this with foam. (This was later explained by Y. Senin, director of the Chernobyl consortium, in June 1990, when he also announced a plan to inject fluid cement to prevent the melted fuel from moving. It is not known whether this plan was carried out.)

Holes are soon to appear in the sarcophagus. During the years following the accident, earth tremors are measured in the area around Chernobyl. Soviet experts become fearful that the sarcophagus might collapse under the strain of another earth tremor. This would result in a new release of radioactive material. The Soviet authorities say the situation is urgent, and in June 1990 ask the German Minister of the Environment for help. According to reports from the German minister, a considerable release would follow the collapse of the sarcophagus, perhaps even twice as much as was released during 1986. This radioactive material is expected to descend within a radius of thirty kilometers of the plant. Partly due to this, a proposal has been made to build a second sarcophagus around the first one.

Blotting Out Radiation

In the Soviet Union's view, the fight against the consequences of radiation has taken on heroic pro-portions. 'Blotting out radiation', calling fire fighters 'heroes' and the cleanup -workers 'liquidators' are just some of the terms used. The accident and the radiation are seen as enemies to be defeated. However, a triumph over radiation can only be achieved if the consequences are slight: if the death rate is not too high and the evacuated area decontaminated. But, shortly after the accident the death rate has risen to 31 and an area 30 kilometers around the power plant has to be declared uninhabitable.

The authorities want the three other reactors not damaged by the accident to start producing electricity again as soon as possible, which makes the required measures even more urgent. For this reason, in the area immediately surrounding the reactors, the top layer of soil is removed; this applies to a layer of about thirty centimeters. In its place, cement is laid down. The reactors themselves are decontaminated as far as is possible, inside and out. In October 1986, Chernobyl-1 becomes operational again, and Chernobyl-2 operational a month later. Getting Chernobyl-3 restarted takes more time, because that unit is right next to the one that was wrecked. Extensive and complicated decontamination work has to be carried out before the reactor can be put back into operation, which happens on 4 December 1987.

Meanwhile, it is decided not to continue the construction of Chernobyl Units 5 and 6 because of "the sensitivity of the local population on the question of nuclear energy", as Soviet Minister of Energy Lukonin puts it. He adds that the workers at the Chernobyl plant will be transported from Kiev and other areas along specially constructed roads to the site. In this way the authorities attempt to keep the contamination risk to the employees as low as possible.

In the summer of 1986 a great clean-up offensive is started. Measurements are taken and the most contaminated areas and objects are located. At this stage, according to Vladimir Komarov, the Soviet director of the World Association of Nuclear Operators, the sectors most dangerous to human life are given priority. During this decontamination operation, contaminated ground, amongst other things, is collected. According to Komarov, this involves collecting more than four million cubic meters of earth which are then stored at eight hundred points in the evacuated zone around Chernobyl.

By March 1987, 60,000 houses and other buildings in 500 towns and villages have been decontaminate. The houses and buildings are treated with - a special fluid to bind the radioactive material. Ten to twenty centimeters of earth is dug away from the streets, gardens and areas around the towns and villages, and removed to other areas. Old houses are demolished and many roofs removed and renewed. Asphalt is laid everywhere and hosed down daily to get rid of any radioactive material. This water ,drains off into the -drainage system, but it is still not known whether it was collected separately. Along the roads, signs appear warning people not to leave their cars. The embankments along the roads are of course contaminated. Even so, eye witnesses claim that cows graze in the fields next to these signs.

The great decontamination offensive does not achieve the results aimed for. Soviet radiation expert, Leonid Ilyin, who played a prominent role in planning all these measures, notes in October 1987 that even the authorities seem to be in no hurry to return the 140,000 strong population which was evacuated from the thirty kilometer zone around the nuclear power station. The reason he gives is the need to study the migration of radioactive material, and this cannot be started until 1988.

The decontamination is earned- out by army reserves and volunteers. However, these people receive insufficient protective clothing to carry out their work, in some cases none at all. Sometimes they have to lift pieces of graphite with their bare hands. In May 1986, there are nearly 40,000 soldiers working in the contaminated zone; this is roughly one third of the number of soldiers fighting at the same time in Afghanistan. After working for a certain amount of time, the soldiers are relieved from duty. All in all, there were between 600,000 and 700,000 people working on the decontamination offensive.

According to US doctor Robert Gale, who performed bone marrow transplants on some of the Chernobyl victims, between 25,000 and 40,000 decontaminators have been exposed to radiation levels of 400 milliSieverts, although the maximum level allowed is 250 milliSieverts. (For comparison: the Dutch standard for employees in the nuclear industry is 20 milliSieverts a year.) Thousands of the decontaminators have been exposed to high levels of radiation, but in spite of this, blotting out radiation damage has failed. The three Chernobyl nuclear plants now operating again will, according to the government, definitely be closed down beginning in 1993, one reactor per year. This, at the insistence of the local population who stage a massive demonstration against Chernobyl, in Kiev in April 1990.

CHAPTER 3: THE CONSEQUENCES

Foreword

The radiation from Chernobyl has consequences for people, animals and plants - in short - for the entire environment. Research is being carried out into the consequences for the environment. The forbidden zone is one great big laboratory. Very little has yet been made known, and in this chapter we will restrict ourselves to the consequences for human beings.

The Radioactive release

The Soviet report on Chernobyl indicates that it is impossible to establish precisely how much radiation was released. The amounts were monitored by special helicopters and aircraft. This makes the measurements imprecise, with a possible fault margin of 50%.

In 1989, A.Gaganinski of the Kurchatov Institute of Nuclear Energy stated that 96% of the radioactive contents of Chernobyl remained inside the power plant, which sets the tone for the analysis, of the accident. This is more than the 90% mentioned in the original estimates. According to Gaganinski, of the total of the core's contents, 3% descended in the Soviet Union and 1% in other countries. As far as the cesium is concerned, 25% of the amount released remained in the neighborhood of the nuclear plant, 40% descended on the Soviet Union and 35% on other countries.

Research carried out by the Dutch Government Committee for the Measurement of Radioactive Material reports that in the area around the nuclear power plant this cesium descended at a level of 2 million Becquerel per square meter (Bq/ m2); on the total surface area of Bulgaria, Yugoslavia, Poland and Rumania, there was an average fall-out of 20,000 to 30,000 Bq/m2. Then follow Finland, Sweden, Norway, Hungary, Austria, Germany, Italy and Switzerland with 5000 to 10,000 Bq/m2. According to the above Committee, the Netherlands is, on average, one of the countries with the lowest amount of fallout: 1800 Bq/m2. Not only was the amount of cesium fall-out in the Netherlands much lower than in the area around Chernobyl, but also the amount of radioactive iodine. The total fall-out of iodine in the Netherlands measured 11,400 Bq/m2, while in Kiev on one day - 2 May 1986 - there was a fallout of 87 times as much.

The Standards

When comparing a number of Dutch standards with those of the Soviet Union, large differences become apparent. According to the 'paper on Measures in the Case of Nuclear Accidents, from the Dutch Ministry of Environment, cows should not be allowed to graze if the amount of radioactive iodine in the air is more than 5000 Becquerels per cubic meter. In the Soviet Union, a standard like this would' have entailed moving all the cattle in an area as far away as Riga, 1000 kilometers to the north of Chernobyl, given the amount of contamination and the wind direction on 28 April 1986. By the 2nd of May, the direction of the wind had changed to the south, and this would have meant prohibiting grazing as f an away as Odessa, more than 600 kilometers south of Chernobyl.

On 30 May 1986, the European Commission established standards for radiation in food; in milk a maximum of 370 Bq cesium per liter was permissable; for other foods a standard of 600 Bq per kilo or liter was set.

Milk was given a separate standard because it forms a large part of the consumption of babies and young children. This standard was changed in 1989, under pressure from countries with a large number of nuclear power plants. Milk may now have a maximum of 1000 Bq cesium and 500 Bq of iodine, while other foods have a standard maximum of 1250 Bq cesium and 2000 Bq iodine. In the Soviet Union however, after the accident a standard of 3700 Bq iodine per liter of milk was set, even less stringent therefore, than the more lenient measures recently set by the European Commission.

By comparison with the European Community, the Soviet standards allow much more cesium in food: up to 70,000 Bq per kilo or liter. In spite of this, 10% of the meat in the Minsk area after the accident contained more than the permissable level; for the Gomel area this was 40% and for the regions of Mogilev and Brest, 20%.