Background to Chernobyl

By Edward Cowley

 A Brief History of the Chernobyl Disaster

Chernobyl is situated in the north of Ukraine, a few miles from the border with Belarus and 100 miles from the capital, Kiev. The nearest city of any size is Chernigov, about 60 miles to the East. This was a quiet agricultural area until in 1972 Gidroproyekt, the soviet ministry responsible for the construction of nuclear power stations, decided that they would build a nuclear power plant here. They named the power station after the ancient town of Chernobyl situated 6 miles away to the south east. The Russian translation for Chernobyl is wormwood.

Even by the standards of the USSR, Chernobyl was a huge enterprise. Initially two reactors were built; these came on line in 1978. Another two were constructed and these were powered up in 1983. A huge reservoir was dug to cool the reactors and an atomic town was built to house the workers and their families. The town was named after a local river, the river Pripyat’. By the time of the explosion in 1986 another two reactors were under construction; had these been completed Chernobyl would have been one of the biggest nuclear power stations in the world.

Even from the start, when it was nothing more than a blue print in Gidroproyekt’s offices in Moscow, Chernobyl was clouded with controversy. It featured an all soviet reactor design, the RBMK, which in Russian literally means “high-power channel-type reactor”, a reactor cooled by water and moderated by graphite, is not used anywhere outside the Soviet Union. It is a huge reactor and was favoured by the soviets not only for patriotic reasons but because it produced plutonium as a bye product, a crucial material in the manufacture of nuclear bombs.

The RBMK, unlike other soviet reactors such as VVER, does not have an outer protective shield and in certain extreme situations is considered less safe. For these reasons some very senior soviet scientists had grave doubts about building such a type of reactor in such close proximity to Kiev. Why not build them in Siberia, they suggested, where the population density is much lower and should an accident occur, the consequences would be much less serious? They were overruled. What was the point of building a nuclear power station where there was no demand for electricity?

Far more deadly than the lack of an outer protective shield, the RBMK has some very serious design faults, which were known about by the scientists who designed it and at least some of the engineers who operated Chernobyl on a daily basis. A reactor uses control rods to control its output. Control rods are made out of boron a substance, which quite literally soaks up radioactivity. When all the rods are outside the reactor in the upright position the reactor runs at full power. When they are fully inserted the chain reaction stops and the reactor shuts down.

When the RBMK type reactor is running at low power it can become unstable and has to be shut down. In an emergency the operator’s last resort is to push the panic button. This immediately inserts all the control roods into the reactor and so nuclear fission ceases; although it is still necessary to cool the reactor for some time after it has been shut down. Before the Chernobyl disaster, once the panic button had been pressed, it took 18 seconds for the control roods to be lowered into the fully inserted position for an RBMK type reactor. In comparison, it takes just two and half seconds in a VVER type reactor, a type which also used in the west.

An even more serious oversight in the design was that the tips of the control rods were actually made of graphite, a substance which has the opposite effect of boron and increases reactivity. Imagine a match; the phosphorus at the end is the graphite tip and the wood is the boron shaft. When the reactor is operating in a normal stable regime, the graphite tips make no difference but when the reactor is unstable they can create a positive void coefficient, in other words a power surge. This is what happened at Chernobyl.  Since the disaster all RBMK type reactors operating in the former Soviet Union have been modified. The graphite tips have been removed and emergency shut down can now be completed in less than 5 seconds.

The test to improve safety

Design, however, was not the only problem. Those old enough to remember the Chernobyl disaster may also remember the trials afterwards where three of the senior engineers on duty that night who were not killed were sentenced to five years in prison for their part in the events. It is a cruel irony that the conditions which precipitated the disaster were in part brought about by a test to improve safety.

When a nuclear reactor is shut down it is still necessary to keep it cool and water is pumped through it for a further for two or three days. Normally the electric power needed to fulfil this operation is taken from the reactors own power supply or from the national grid. In the event of an emergency, for example a war, it is possible that the national grid and the power station will have no electricity so diesel generators are on stand by to keep the water pumping round the reactor. The problem is that it takes 30 seconds for the diesel generators to start up. The soviets thought, that they could use the power from a down spinning turbine and convert this back into electricity to power the water pumps. It’s a clever idea but in practice it’s hard to implement and in order to test this theory it is necessary to run the reactor at low power. They were trying to carry out this test when Chernobyl exploded.

Russian roulette with the reactor

Any operating nuclear reactor has a number of safety systems, which are designed to prevent the set of circumstances, which occurred at Chernobyl from ever taking place. Normally the emergency power reduction system switches itself on when the reactor becomes unstable. All 211 of the boron controlling rods are lowered automatically into the reactor, cooling water is fed from the Emergency Core Cooling System tanks, the emergency feed water pumps switch themselves on and the standby diesel generators start up. These systems are normally controlled through the MPA (maximum design-basis accident) button. But this, astoundingly, had been switched off. Why? The engineers in charge of the reactor unit A.S. Dyatlov and his absent colleagues V.P Brukhanov and N. M. Fomin wanted to ensure a “pure” experiment and gave their express permission to turn off all of the reactor’s emergency safety systems. 

The staff at Chernobyl had been trying to perform this experiment for months. They had attempted to do it during the day on the 25th April but were prevented by the load dispatcher in Kiev, who needed all the electricity produced by Chernobyl. It got pushed back and the less experienced night shift would have to see whether they could pull it off.

By 12:00 am on the 26th April 1986, almost an hour an a half before the explosions, the control room of reactor number 4 would have been full activity and nervous anticipation. These were men vehemently proud of their professions and working in one of the most prestigious and modern nuclear power stations in the USSR. About 15 people were in the control room that night. To the left were the team of mechanical engineers, who had come all the way from Kharkov. Their job was to monitor the power of the down spinning turbine. In the middle were the operators responsible for the reactor, Sasha Akimov and Leonid Toptunov. Striding up and down between these two teams was Anatoly Stepanovich Dyatlov the senior engineer of the fourth block and the man ultimately in charge of the experiment.

Dyatlov was a pushy man and he was used to getting his own way. Prior to landing his job at Chernobyl he had worked with small water cooled reactors of the type used in nuclear submarines. His experience was not suited to working in nuclear power stations, particularly with large RBMK type reactors. According to Grigori Medvedev the author of the book, The Truth about Chernobyl, who knew most of the senior staff at Chernobyl and worked there himself in the early years of its operation, Dyatlov had a difficult character and was not a good manager. There was a large laboratory in Chernobyl, which, claims Medvedev, would have been a more suitable environment for him. The following is a testimony given by one of his colleagues,   “Dyatlov was a complex person with a difficult character. While masquerading as a stern, demanding boss, in fact Dyatlov really didn’t care what was happening. He was a stubborn tedious man who did not keep his word.” Testimony of Razim Ilgamovich Davletbaev, Deputy Chief of the Turbine Unit, No.4 reactor unit. 

Leonid Toptunov was in charge of the reactor. He was 26 and had only recently graduated from the Kurchatov Nuclear Institute in Moscow. Although he had been a good student and was dedicated to his profession, he lacked the experience required for an experiment as complicated as this.

He began to lower the power of the reactor, inserting virtually all of the control rods but for some reason power dropped to a point too low to conduct the experiment. The reactor was now in a dangerous state and needed to be shut down immediately. He requested permission to shut down the reactor; the experiment would therefore have to be cancelled. The experiment had already been delayed once, we can be sure that Dyatlov didn’t want to explain to his superiors, Brukanov and Fomin, why it had been delayed again. Permission was refused. Instead of making the only sensible decision and shutting down the reactor Dyatlov instead began screaming at the young operators, “If you don’t raise the power you half wits I’ll damn well do it myself!”

Toptunov couldn’t understand it, this flew in the face of everything he’d been taught. “If we raise power Anatoly Stepanovich” he stammered, “then we risk having a power surge.” This must have been an agonising moment for Toptunov and one he no doubt regretted for the rest of his life. A life soon to be brought to an abrupt and excruciating end in hospital number 6 in Moscow. “If I raise power” he would have thought to himself, “I risk having a power surge and the reactor could go completely out of control, but if I don’t do it I’ll be fired.”

Toptunov just didn’t have it in him to stand up to his boss, and so at 1:00 a.m. that fateful decision was made and in a desperate attempt to raise power all the control rods were pulled out except for 18. The exact number will never be known, but who cares, it was a direct breach of the operating rules, which clearly state that an operating reactor must never have less than twenty eight roods fully inserted.

Toptunov’s prediction proved to be accurate, at 1:22 and 30 seconds the power in the reactor began to increase at an astronomical level. “Anatoly Stepanovich, we’re having a power surge I’m activating the emergency power reduction system!” said Toptunov, desperately trying to sound decisive. The button was pressed and the rods began their decent into the reactor core, would 18 seconds be enough time to avert disaster? 

There were now loud banging noises coming from the central reactor hall. As the reactor was spinning out of control it was also getting hotter and hotter. The lines of communication that fed water in and out of the reactor and the channels that housed the control rods were beginning to break up in the intense heat.  After the rods had descended two and half meters they suddenly stopped. Akimov could not believe his eyes and in a last desperate attempt cut the power to the servos in the hope that they might drop into position with the force of gravity. But the rods had no where to go, their channels were buckled and mangled by the heat. The Selsyn dials that tell an operator the parameters of the reactor glared menacingly, alarms were going off throughout the control room. 20 seconds later the first, a steam explosion occurred. Then at 1:23 and 58 seconds there was a nuclear explosion that blew the roof off the reactor. 

The liquidators

The worst fallout from Chernobyl effected Belarus, Ukraine and a small area of Russia. However, the scale of the problem meant that men from all over the Soviet Union were drafted in as liquidators. Hundreds of thousands of soldiers, thousands of fireman pilots and engineers were called up. Some were unaware of the danger they were facing, others, in particular the engineers and scientists went without even the slightest hesitation, well aware that they were going into a lethal situation. “Esli ne ya a kto?” “If not me then who?” many would have asked themselves. 

This was the first time a nuclear accident on this scale had ever taken place and the Soviets had to solve problems as they arose in the best way they could. They somehow had to get highly radioactive graphite which had been blasted out of the reactor off the roof of the turbine hall. They ordered in robots from Germany and Japan to push the graphite back into the jaws of the smouldering reactor. The robots malfunctioned, their electronics disabled by the extremely high levels of radioactivity. Men were drafted in instead. Thousands of soldiers were given the only protection available, a primitive lead suit for the torso and genitals, a mask and rubber gloves. They were given one minute to go onto the roof of the turbine hall, pick up a piece of graphite with a shovel and throw into the reactor. In that minute they received their entire lifetime’s dose of radioactivity.

The Moscow based scientist Grigori Medvedev, in his book The Truth about Chernobyl recalls arriving in Chernobyl a few days after the disaster as part of The Special Commission sent from Moscow to try and find a way of bringing the appalling situation under some sort of control. This is what he found, “The soldiers on patrol were wearing for the most part “snout” respirators, but some wore the “petal” variety. Soldiers were sitting, smoking, on some of the armoured personnel carriers, with the hatches open. A number of them had removed their respirators altogether for the purpose, while others had poked a hole in their respirators through which they passed their cigarettes.” While travelling to Chernobyl from Kiev Medvedev recalls the following: “Mikhailov began urging the driver to stop outside a liquor store. “We need vodka to decontaminate ourselves. Once your balls are irradiated, that’s it. Is life worth living after that?” V.S. Mikhailov was deputy head of nuclear construction for the USSR.

Many people think that what happened at Chernobyl was a worst case scenario but this is not the case. Weeks after the explosion the reactor was still burning ferociously. The Scientists and engineers desperately trying to solve this appalling situation were petrified that the reactor could burn a hole in its concrete foundations and come into contact with the water in the suppression pools and the water table. The result would have been a hydrogen bomb making life in most of Europe and the western part of the Soviet Union unliveable.  Military divers and miners were rushed in to pump the water out and then pump concrete under the burning reactor. Virtually all of the miners, divers and those soldiers who went out onto the roof died long ago, most of them were relatively young.

Chernobyl since the Disaster

Many people in Britain are unaware that Chernobyl was still an operating power station until December 2000.After the explosion the Soviet Government made the controversial decision to reopen the remaining three reactors at Chernobyl. Opinion is divided over whether this was a wise move. Scientists such as Vladimir Chernousenko and Grigori Medvedev point to the waste in human life spent cleaning up after the explosion purely so that the power station could be reopened. They say that the decision to bring the other reactors back on line was political, so that the USSR could report to the world and to the IAEA in Vienna that Chernobyl was producing electricity again. Instead the power station should have been abandoned.

Other scientists, such as Zhores Medvedev and people who I met in Ukraine, including the journalist Mae Rubenko argue that Chernobyl had to be cleaned up regardless of whether it reopened or stayed closed.  They would still have had to build the sarcophagus over the remains of the fourth reactor as its contents were too radioactive to be left open. They say that the Ukraine badly needed the electricity produced by Chernobyl and point to the frequent power cuts when the USSR broke up and Ukraine split from Russia in 1991. Until Ukraine reduced its dependence on Russia for energy and restructured its electricity grid Chernobyl kept the lights on and the underground running in the capital Kiev. 

Reactor number one and two closed in 1996 after a fire in the turbine hall. Reactor number three was shut in December 2000 under huge political pressure from the west, although technically it had not reached the end of its life span. RBMK reactors in Russia, which were built at the same time and even before Chernobyl, are still operated and in some cases, such as the Leningrad nuclear power station, their lives will be extended to meet the growing demand on electricity.

Scientists and engineers still work at Chernobyl today, monitoring the decommissioning of the three reactors that were operational after the explosion and, most importantly, monitoring the sarcophagus and preparing for the second entombment of the reactor. The design for the second entombment is currently being finalised. A huge dome, a little bit like the millennium dome in Greenwich but the shape of the arch over the new Wembley Stadium and made of thick steel and concrete will be assembled adjacent to the power station and then manoeuvred over the current sarcophagus.

Scientists working in Chernobyl are worried that the current structure could collapse before the new one is ready. The Ukrainian government cannot afford to manage this huge engineering project on its own and needs money from the EU and the World Bank. Scientists such as Zhores Medvedev are cynical as to whether the money will be forthcoming. He argues that if the present structure does collapse it will only affect Ukraine and Belarus and therefore it is not top on the EU’s list of priorities.

The Zone

By early May 1986, the authorities had evacuated and sealed off everywhere with-in a 30 kilometre radius of the power station. This became known as the exclusion zone or simply the zone. While the official line is that it is forbidden to live or work in the zone without a special permit many people have moved back to their old houses and the authorities turn a blind eye. Even if the Ukrainian government relocated them to a flat in a Kiev suburb, they would probably refuse to move. They have always depended on the land for survival; they have grown their own vegetables and raised their own animals for generations. In practical terms they would be unable to survive on a tiny state pension without being able to grow their own food.  

Many of them are old and have no where else to go. Few of them really understand the dangers posed by living in an area contaminated by radioactivity and eating radioactive food and those that do don’t care. When I was in Ukraine recently I saw a home video of an old couple who lived in the zone because it was the only home they had. The old man cried because he missed his children so much and could hardly ever go and see them.

The following is a quote from Ablaze, by the British writer and historian Pierce Paul Read:

“Gathering berries and mushrooms in the forest and pickling tomatoes and cucumbers had been the peasant’s part time in the summer months from time immemorial. How could they be expected to stop doing so now? In winter, cutting down trees, chopping up logs and burning them in their stoves has also been part of the daily routine, but now each stove that burned the contaminated wood became a small version of Chernobyl’s fourth reactor.”   

In recent years Chernobyl has become something of a tourist attraction. Companies in Kiev charge $120 upwards for a guided tour of the Zone and the power plant. Military police, with much posturing and flustered document checking, issue jump suits and Geiger counters when you enter a 10 KM radius of the power station. Although this is quite unnecessary, it helps create dramatic effect and adds that special Soviet feel. The tour includes a visit to the atomic town of Pripayt’, built to house the workers of Chernobyl. It was hastily evacuated 2 days after the explosion on the 28th April 1986. Although the gardens are now overgrown and wild dogs roam the streets, it is frozen in the days of the Soviet Union. A stark reminder of how people lived, with red banners commemorating the 1st May celebrations, which never took place.

Although Chernobyl is hardly a nuclear wasteland, the current activity in the former power plant and in the Zone hides serious long term health risks. Doctors who work in the areas of Ukraine and Belarus that border the exclusion zone are clear that cancer rates in the local population are way above average. Heart defects and neurological disorders are also common and children are being born with weak immune systems. Although, the Ukrainian authorities fall short of blaming Chernobyl, the people themselves are in little doubt. The birth rate in Chernigov has plummeted since the early 1990’s. Parents are afraid that there children may be born with serious health problems.

Unfortunately there have been virtually no detailed examinations of the long term effects of eating contaminated food as there are not the resources to do so. No one can be sure of the precise nature of the long term effects of Chernobyl. This problem is exasperated by the poverty of most Ukrainian citizens. Wages are low, unemployment is high and alcoholism and drug abuse are rife. Not all of these problems can be blamed on Chernobyl and it can provide an easy reference of blame for problems that may be much more complicated.