Nuclear accident in America. Reactor emergency shutdown

Back in 1979, it was a glorious year. This year there were several revolutions, Soviet hockey players took the Challenge Cup from the NHL team, and Soviet troops entered Afghanistan, it snowed in the Sahara for half an hour, and Jimmy Carter was attacked by a rabbit. And three weeks before the memorable rabbit attack, the largest nuclear power plant accident in the United States (and at that time in the world) occurred. This catastrophe put an end to American nuclear energy and showed that nuclear energy, although peaceful, is not to be trifled with.

Three Mile Island accident: first nuclear

An object: Power unit No. 2 of the Three Mile Island nuclear power plant (Three Mile Island, “Three Mile Island”) on the island of the same name on the Susquehanna River, 16 km south of the city of Harrisburg, Pennsylvania, USA.

Victims: are missing.

Causes

There are two reasons for the disaster at the Three Mile Island nuclear power plant:

• The “trigger” of the accident was a failed feed pump of the second cooling circuit of the reactor.
• The emergency development of events was due to a simply incredible combination of a number of technical problems(valve jamming, incorrect instrument readings, failure of several pumps), gross violations of repair and operation rules, and the notorious “human factor”.

People who encountered such an accident for the first time were simply confused; they had neither the appropriate preparation (at that time no one was prepared for this kind of emergency situation) nor an understanding of what was happening. The situation was aggravated by shamelessly lying instruments and a large number of technical problems.

That’s why what happened happened - the first serious accident at a nuclear power plant, which, before the tragic events at Chernobyl nuclear power plant remained the largest in the world.

Chronicle of events

The accident at the second power unit of the nuclear power plant began at approximately four in the morning on March 28, and the fight for the reactor continued until the evening, and the danger was completely eliminated only by April 2. The chronicle of the events of this accident is extensive, but it makes sense to dwell only on its key moments.

Approximately 4.00. The secondary circuit feed pump stopped, as a result of which the water circulation stopped and the reactor began to overheat. It was here that the main event occurred, which served as the beginning of the accident: due to a gross error made during repairs, the emergency pumps of the secondary circuit did not start. As it turned out later, the repair technicians did not open the pressure valves, but the operators could not see this, since the pump status indicators on the control panel were simply covered with repair signs!

The first 12 seconds after the accident. An increase in temperature and pressure in the reactor triggered the system emergency protection, which shut down the nuclear boiler. A little earlier, a safety valve was activated, which began to release steam and water from the reactor (it accumulated in a special container - a bubbler). However, when normal pressure was reached, for some reason the valve did not close, which was noticed only after 2.5 hours - during this time the bubbler overflowed, due to critical level pressure, the safety membranes located on it burst, and the containment chambers began to fill with superheated steam and hot radioactive water.

4.02. The emergency cooling system of the reactor was activated - water began to flow into the core, which, due to the valve not closing, also entered the containment through the bubbler.

4.05. First blunder operators. Despite the fact that the reactor was practically empty, instruments showed that there was too much water in it, and so the operators gradually turned off all the emergency pumps pumping water into the primary circuit.

4.08. Operators finally discovered that the secondary circuit's emergency pumps were not working, but starting them up didn't do much to improve the situation.

Up to 6.18 people, relying on incorrect instrument readings (and, at the same time, for some reason not noticing other important indicators that indicated the nature of the accident), tried to determine the problem and performed various actions, but only aggravated the situation. As a result, the reactor core, deprived of cooling, began to literally melt, although the nuclear chain reaction had already been stopped. The overheating was caused by the decay of highly active fission products of uranium (it is because of this that a nuclear reactor cannot be stopped immediately, in an instant).

Only at 6.18 am the arriving engineer determined the true cause of the accident, and the drainage of water from the reactor core was stopped. However, the emergency cooling pumps, which had been stopped two hours earlier, various reasons It was possible to launch only at 7.20, which prevented a disaster - special borated water pumped into the core stopped its heating and further destruction.

It would seem that the accident has been averted, and now we can safely proceed to completely shut down the reactor. However, already in the afternoon of March 28 it turned out that a huge hydrogen bubble had formed in the reactor vessel, which could flare up and explode at any second - such an explosion at a nuclear power plant would lead to terrible disaster. But where did this hydrogen come from? It was formed due to the reaction of hot zirconium with hot water vapor, which literally disintegrated into oxygen and hydrogen atoms. Oxygen oxidized zirconium, and free hydrogen accumulated under the reactor lid - and an explosive bubble formed.

In the evening, at 19.50 managed to restore the operation of one of the primary circuit pumps, which, however, only worked for 15 seconds, but this made it possible to soon start the remaining pumps and restore more or less normal work primary circuit of the reactor cooling system.

Until April 2, operators worked to remove hydrogen from under the reactor lid - this operation was successful, and the danger of an uncontrolled development of the accident was completely eliminated.

It is interesting that at 6.30 in the morning the operators wanted to conduct reconnaissance inside the containment, so to speak, to look at the accident “from the inside,” but the station management did not give permission for the sortie. As it turned out later, this saved people from imminent death - by that time background radiation in containment rooms exceeded the norm hundreds of times!

And already on April 1, US President Jimmy Carter himself arrived at the Three Mile Island station for a visit, who reassured people and said that there was no danger. And if you believe the official data, then there really was no danger, but the excitement of people that arose due to the accident can be understood.

Three Mile Island Nuclear Power Plant

Consequences of the accident

Surprisingly, the accident at Three Mile Island did not have serious consequences for human health and the environment, but it had the most serious impact on the minds of people and American nuclear energy. But, despite this, all work to eliminate the consequences of the accident was completed only by 1993!

Core destruction. The temperature in the reactor during the accident reached 2200 degrees, as a result, about half of all components of the core melted. In absolute figures, this amounts to almost 62 tons.

Nuclear pollution. From nuclear reactor A large amount of radioactive water leaked out, causing the level of radioactivity in the containment rooms to be more than 600 times higher than normal. A certain amount of radioactive gases and steam entered the atmosphere, and as a result, every resident of the 16-kilometer zone around the nuclear power plant received no more radiation than during a fluorography session. The most dangerous thing - the release of highly active nuclides into the atmosphere and water - was avoided, so the area remained “clean”.

The collapse of US nuclear energy. After the accident at the Three Mile Island nuclear power plant in the United States, it was decided not to build any more nuclear power plants, which led to stagnation in the American nuclear energy.

Human psychology and the “Chinese syndrome”. By simply amazing coincidence, two weeks before the accident, the film “The China Syndrome”, which tells the story of the nuclear power plant disaster, was released on big screens. The slang term "China syndrome," coined in the 1960s by nuclear physicists, refers to an accident in which the fuel in a reactor melts and burns through the containment. But in the second power unit of the Three Mile Island nuclear power plant, it was precisely the melting of the reactor core that occurred! So there is nothing strange in the fact that after a real accident there was panic, and no assurances high-ranking officials, including the US President himself, could not completely calm people down.

A memorial sign telling about the incident at the nuclear power plant

Current situation

Currently, the Three Mile Island NPP continues to operate - power unit No. 1, which was under repair at the time of the accident, was launched in 1985. The second power unit is closed, inner part The reactor has been completely removed and disposed of, and the site is being monitored. The station will operate until 2034.

Interestingly, in 2010, the turbogenerator of the emergency second power unit was sold, removed and transported in parts to the Shearon Harris nuclear power plant (North Carolina, USA), where it took its place in the new power unit. Marvelous? Not at all. After all, this equipment only worked for six months, and during the accident it was not harmed or received radioactive contamination - don’t let multimillion-dollar assets go to waste!

What has been done to prevent this from happening again?

One of the results of the investigation into the causes of the accident was the understanding that the station operators were simply not prepared for the incident. This problem was solved by revising the concept of training for nuclear power plant operators: if earlier the emphasis was on people analyzing the situation and independently looking for a solution, now operators learned to work mainly according to pre-prepared “scenarios” of accidents.

Similar incidents

Seven years later, an accident occurred in the USSR that literally and figuratively overshadowed the incident at the Three Mile Island nuclear power plant - the infamous Chernobyl nuclear power plant disaster that occurred on April 26, 1986. It is interesting that the course of both accidents was similar, but in the fourth power unit of the Chernobyl nuclear power plant something happened that did not happen to the Americans - an explosion occurred, which had the most serious consequences.

The accident at the Three Mile Island nuclear power plant also pales in comparison to the accident at the Fukushima nuclear power plant, which occurred in Japan during the tsunami and earthquake on March 11, 2011. Both the Japanese and Soviet accidents are still troubling, and one can only hope that the world will not see any more nuclear disasters.

Analysis of accidents at nuclear power plants. Ways to solve security and non-proliferation problems. Energy and ecology.

Analysis of accidents at nuclear power plants.

Three Mile Island Nuclear Power Plant Accident

Three Mile Island Nuclear Power Plant Accident Three Mile Island accident) - one of the largest accidents in the history of nuclear energy, occurred on March 28, 1979 at the Three Mile Island nuclear power plant, located on the Susquehanna River, near Harrisburg (Pennsylvania, USA).

Before Chernobyl accident, which happened seven years later, the accident at the Three Mile Island nuclear power plant was considered the largest in the history of world nuclear energy and is still considered the worst nuclear accident in the United States, during which the reactor core was seriously damaged and part of the nuclear fuel melted.

The first signs of an accident were discovered at 4 a.m., when for unknown reasons the supply stopped. feed water main pumps to the steam generator. All three emergency pumps had already been under repair for two weeks, which was gross violation NPP operating rules.

As a result, the steam generator could not remove the heat generated by the reactor from the primary circuit. The turbine switched off automatically. In the primary circuit of the reactor block, the temperature and pressure of water increased sharply. Through a safety valve, a mixture of superheated water and steam began to be discharged into a special tank (barbater), however, after the water pressure dropped to normal level, the valve did not sit in place, as a result of which the pressure in the bubbler also increased beyond the permissible limit. The emergency membrane on the bubbler collapsed, and about 370 cubic meters of hot radioactive water spilled onto the floor.

The drainage pumps turned on automatically; the personnel should have turned them off immediately so that all the radioactive water would remain inside the containment, but this was not done. Water flooded the floor in a layer of several inches, began to evaporate, and radioactive gases, along with steam, penetrated into the atmosphere, which was one of the main reasons for the subsequent radioactive contamination of the area.

At the moment the safety valve opened, the reactor's emergency protection system was activated, releasing the absorber rods, as a result of which the chain reaction stopped and the reactor was practically stopped. The process of fission of uranium nuclei in the fuel rods stopped, but the nuclear decay of fragments continued... The safety valve remained open, the water level in the reactor vessel decreased, and the temperature quickly increased. Apparently, this led to the formation of a steam-water mixture, as a result of which the main circulation pumps failed and they stopped.

As soon as the pressure dropped, the emergency core cooling system was automatically activated, and the fuel assemblies began to cool. This happened two minutes after the accident began. (Here the situation is similar to Chernobyl twenty seconds before the explosion. But in Chernobyl, the emergency core cooling system was turned off by personnel in advance.) Water continued to evaporate from the reactor. The safety valve appeared to be jammed and operators were unable to close it using a remote control. The water level in the reactor dropped, and one third of the core was left without cooling. The protective zirconium shells of the fuel rods began to crack and crumble. Highly active fission products began to emerge from damaged fuel elements.

The primary circuit water became even more radioactive. The temperature inside the reactor vessel exceeded four hundred degrees, and the indicators on the control panel went off scale. The computer that monitored the temperature in the core began to produce continuous question marks and issued them over the next eleven hours...

On the night of March 28-29, a gas bubble began to form in the upper part of the reactor vessel. Core heated up to such an extent that due to chemical properties The zirconium shell of the rods split water molecules into hydrogen and oxygen. A bubble with a volume of about 30 cubic meters, consisting mainly of hydrogen and radioactive gases - krypton, argon, xenon and others - greatly impeded the circulation of cooling water, since the pressure in the reactor increased significantly. But the main danger was that the mixture of hydrogen and oxygen could explode at any moment (what happened in Chernobyl). The force of the explosion would be equivalent to the explosion of three tons of trinitrotoluene, which would lead to the inevitable destruction of the reactor vessel. In another case, a mixture of hydrogen and oxygen could penetrate from the reactor to the outside and accumulate under the dome of the containment shell. If it had exploded there, all the radioactive fission products would have been released into the atmosphere (which happened at Chernobyl). The radiation level inside the containment shell had reached 30 thousand rem per hour by that time, which was 600 times higher than lethal dose. In addition, if the bubble continued to grow, it would gradually displace all the cooling water from the reactor vessel and then the temperature would rise so much that the uranium would melt.

On the night of March 30, the volume of the bubble decreased by 20 percent, and on April 2 it was only 1.4 cubic meters. To finally eliminate the bubble and eliminate the danger of explosion, technicians used the so-called water degassing method...

On April 1, President Carter visited the power plant. He appealed to the population to “calmly and accurately” comply with all evacuation rules if the need arises.

In his April 5 speech on energy issues, President Carter spoke at length about alternative methods such as the use of solar energy, oil shale processing, coal gasification, etc., but made no mention at all of nuclear energy, whether fission of the atomic nucleus or controlled thermonuclear fusion.

Many senators say the accident could lead to a “wrenching re-evaluation” of nuclear energy, but they say the country will be forced to continue generating electricity from nuclear power plants because the United States has no other choice. The senators' ambivalent position on this issue clearly demonstrates the predicament in which the US government found itself after the accident...”

The Americans did not close nuclear power plants and abandon nuclear energy, and the share of nuclear energy in the energy balance continued to increase - from 11% of all electricity produced in 1980 to 20.1% in 1992. Now we can say that stabilization has occurred at a level of approximately 20%; since 1992 it has changed very little and in 2001 amounted to 20.7%.

Is it true that US nuclear energy policy is influenced by public anti-nuclear sentiment and numerous green movements? Rather, these sentiments are just an excuse for very specific policies, for example, to abandon the development of breeder reactor technology.

In June 1996, a Pennsylvania district court dismissed 2,100 lawsuits seeking compensation for personal injury related to the Three Mile Island spill. The court held: “The parties have had nearly two decades to present evidence in support of their claims... The insufficiency of the evidence pleaded in support of the plaintiff is obvious. The court examined all the materials of the case for evidence that, if presented in the most favorable light for the plaintiff, would allow on the basis material facts transfer consideration claims to the court. This attempt was in vain."

Although numerous studies have confirmed the absence radiation consequences accident at Three Mile Island, the public's attitude towards this accident and towards nuclear energy itself, formed by the media, has remained virtually unchanged. If, according to polls public opinion In 1971, 58% of Americans said they would welcome a nuclear power plant in the area where they live; later polls showed that 63% of Americans would avoid such a neighborhood. Polls also noted the following trend: if in the 1950s-1960s the public had even a fairly exaggerated belief in technical progress, then subsequently trust in science decreased more and more.

With a dual-circuit cooling system, two power units were operated, with a capacity of 802 and 906 MW, the accident occurred at unit number two (TMI-2) on March 28, 1979 at approximately 4:00.

For simplicity, in what follows, we will count from exactly 4:00:00.

4:00:00

The root cause of the accident was the failure of the feed pumps in the second circuit of the reactor cooling system, as a result of which the water supply to both steam generators was stopped. The turbogenerator automatically turned off and turned on emergency system supply of feed water to the steam generators, however, despite the normal functioning of all three emergency pumps, water did not flow to the steam generators. It turned out that the pump pressure valves were closed. This condition has been preserved since planned repairs that ended on the unit a few days before the accident.

4:00:00-4:00:12

Since the heat removal from the primary circuit stopped, the pressure in it began to increase, which after a few seconds exceeded permissible value. The pulse safety valve on the pressure compensation system opened, releasing steam into a special container, a bubbler. The pressure began to rise much more slowly. High pressure in the primary circuit, approximately 17 MPa, caused the reactor to be shut down by emergency protection 9 seconds after the initiating event. The coolant in the circuit stopped heating, the average temperature dropped, and the volume of water began to decrease. The increase in pressure sharply turned into a drop. At this moment, another technical malfunction appeared - the safety valve should have closed at the lower response setting, but this did not happen and the discharge of the primary circuit coolant continued. The indicator on the operator's console showed that the valve was closed, although, in fact, the light only indicated that power had been removed from the valve. No other controls were provided. The coolant leak continued for almost 2.5 hours until the shut-off valve was closed.

4:01

The time for complete drying in case of loss of feed water for steam generators of the type that were installed at this station is 30-60 seconds, which is determined by their low water content. Therefore, for several minutes, heat removal from the primary circuit almost completely stopped.

4:02

Two minutes after the initial event, automatically, as provided when the pressure drops below the permissible level, in this case 12 MPa, the emergency cooling system of the reactor core and high-pressure system pumps were turned on in the primary circuit system.

4:05

Control panel panel with repair markings hidden from personnel color indication about the closed position of the valves on the pressure of the emergency feedwater pumps.

At this moment, the nuclear power plant operators allowed the first serious mistake, which probably determined the nature of the accident and its scale. They turned off one, and then the second emergency pump out of three operating ones, and manually reduced the flow rate of the remaining one by more than 2 times; this amount of water was not enough to compensate for the leak. The reason for this decision was the readings of the level gauge of the volume compensator, from which it followed that water was supplied to the primary circuit faster than it exited through the faulty safety device. The reactor management personnel were trained to prevent the pressure compensator from filling with water (not to “stand on a rigid circuit”), since this would make it difficult to regulate the pressure in the circuit, which is dangerous from the point of view of its integrity, so they turned off what they considered “unnecessary” high-pressure pumps . As it turned out later, the level gauge gave incorrect readings. In fact, at this time there was a further drop in pressure in the primary circuit due to an uncompensated leak. When the pressure dropped to the saturation point, steam bubbles began to form in the core, which began to displace water from it into the pressure compensator, thereby increasing false testimony level gauge. Still concerned about keeping the compensator from overfilling, operators began draining it through the primary drain line as well.

4:08

At this moment, it was discovered that the valves on the pressure of the emergency feedwater pumps were closed; the indication of their condition was hidden by a marking repair plate, which the operators finally guessed to raise. The personnel realized that emergency feedwater was not entering the steam generators, the valves were opened and its flow began. The fact that the supply of feedwater to the steam generators was interrupted for 8 minutes could not in itself lead to serious consequences, but added confusion to the actions of the staff and diverted their attention from dangerous consequences jamming in open position pulse valve in the pressure compensation system.

4:14

Distracted from the main problem, the operators did not attach importance to several signs that the safety valve did not close - the temperature sensor on its discharge line showed an excess of 100 degrees, but its readings were attributed to residual heating from the release of steam at the beginning of the event and to an overestimation of the readings by the sensor, which was considered commonplace.

Also at this time, it was noticed that the safety membranes on the bubbler were triggered due to excess pressure in it, as a result of which steam with high parameters began to flow into the containment rooms.

4:38

The reactor room inspectors reported that the pumps had turned on, pumping out the overflowing pit tank of the hermetic volume. The operators at the control panel turned them off, still not realizing that there was a large amount of water in the containment rooms.

4:50-5:00

Final state of the reactor core:
1 - input of the 1st loop A
2 - input of 2nd loop B
3 - cavity
4 - top layer of partially fused fuel assembly fragments
5 - metal-fuel crust
6 - molten material
7 - lower layer of fragments of oxidized uranium and zirconium
8 - probable volume of uranium that flowed down
9 - damaged in-reactor control sleeves
10 - melted hole in the core baffle
11 - layer of molten structural materials on the bypass section of the internals
12 - damage to the plate of the protective pipe block

Another indirect sign leaks in the primary circuit were ignored - the temperature in the containment rooms increased by 50 degrees, and overpressure exceeded 0.003 kgf/cm².

Also at this time, another oddity was noticed - the concentration of the liquid absorber, boric acid, in the circuit decreased greatly and, despite the fully submerged control rods, the readings of the neutron flux monitoring devices began to increase. A decrease in boric acid concentration was also a consequence of a severe leak. The operators began an emergency injection of boron to prevent the reactor from becoming critical again, which was partly the right decision, but not decisive main problem, which has not yet been determined.

5:13

By this time, the circulation in the primary circuit was so disrupted that two of the four main circulation pumps began to vibrate strongly, due to the mixing of water and steam in the circuit. Operators turned off the pumps to prevent them from collapsing or damaging the primary piping.

5:45

For the same reason, the 2 remaining circulation pumps of the primary circuit were turned off. Forced coolant circulation has stopped.

It can be noted that turning off the circulation pumps in the primary circuit of reactors with pressurized water should not lead to the cessation of coolant circulation; natural circulation should continue. However, at that moment a vapor-gas bubble had accumulated under the reactor cover, the presence of which, coupled with the geometric arrangement of the core and steam generators in the design of this nuclear installation, prevented the occurrence of natural circulation in the primary circuit.

6:18

Almost 2.5 hours after the events began, their cause was determined by a newly arrived engineer. Operators closed a shut-off valve in line with a pulse valve that was stuck open. The flow of coolant from the primary circuit has stopped. However, the destruction of the exposed core, which by this time appeared, continued, as calculations subsequently showed, its exposed 2/3 heated up to a temperature above 2200 °C, which led to the rapid oxidation of the shells of the fuel elements (steam-zirconium reaction with the release of a large amount of hydrogen) and subsequently their extensive destruction due to the dissolution of uranium dioxide by zirconium and the flow of this mass downwards. According to experts, approximately 1/3 was oxidized total number zirconium.

6:30

The operators requested permission from the management for exploration by reactor shop workers in the hermetic volume. Fortunately, permission was not obtained; the people who entered there could have died.

7:10

At this moment, high radioactivity was recorded in the primary circuit, which indicated serious damage to the fuel rod cladding.

The personnel managing the power unit received their first understanding of the scale of the accident.

7:20-8:00

Finally, the emergency high-pressure cooling pumps were started again, worked for 40 minutes and turned off, and the emergency supply of borated water ran out. However, she managed to cover the core, preventing its further destruction, but this was only a temporary measure.

8:30-11:30

Operators, realizing that there is still no natural circulation in the circuit and no heat removal from the fuel, try to increase the pressure in order to condense the steam in the circuit and start the circulation pumps, but they do not know that a large amount of non-condensable gases, primarily hydrogen, has accumulated in it .

The control panel of the second power unit of the station a few days after the accident, work is underway to eliminate it.

11:40

The personnel, in the absence of an action plan and thoughts in the right direction, decided to carefully and slowly release the pressure in the primary circuit to initiate the activation of the hydraulic accumulators, another passive safety system. The whole next day they tried to do this, but in fact these actions were not successful and only a small amount of water from the hydraulic reservoirs entered the active zone. But now, due to the released pressure, it was impossible to start the circulation pumps.

Also during the day there were local combustions of hydrogen in the containment.

16:00

Finally, the station management accepted correct solution- raise the pressure in the primary circuit and try to start the circulation pumps. The emergency high-pressure pumps were turned on again.

19:50

The operators started one circulation pump of the primary circuit, which worked for only 15 seconds, but managed to throw several tens of cubic meters of water into the core, which condensed the steam and then allowed the circulation pumps to start. In the future, the staff did not make mistakes, dangerous amount The hydrogen accumulated under the reactor lid was gradually removed. In state cold stop the reactor was transferred only a month later.

Consequences

Decontamination of hermetic rooms.

Although nuclear fuel partially melted, it did not burn through the reactor vessel, so radioactive substances, mostly stayed inside. By different estimates, the radioactivity of the noble gases released into the atmosphere ranged from 2.5 to 13 million curies ( 480 10 15 Bq), however the release of hazardous nuclides such as iodine-131 was negligible. The station area was also contaminated with radioactive water leaking from the primary circuit. It was decided that there was no need to evacuate the population living near the plant, but the governor of Pennsylvania advised pregnant women and children to leave the five-mile (8 km) zone preschool age. The average equivalent radiation dose for people living within a 10-mile (16 km) zone was 8 millirem ( 80 µSv) and did not exceed 100 millirem (1 mSv) for any of the residents. By comparison, eight millirems is approximately equivalent to the dose received from fluorography, and 100 millirems is equal to one-third of the average dose received by a US resident per year due to background radiation.

A thorough investigation into the circumstances of the accident was carried out. It was recognized that the operators made a number of mistakes that seriously worsened the situation. These errors were caused by the fact that they were overloaded with information, some of which was not relevant to the situation, and some of which was simply incorrect. After the accident, changes were made to the operator training system. If before this the main attention was paid to the operator’s ability to analyze the situation and determine what caused the problem, then after the accident the training was concentrated on the operator’s implementation of predetermined technological procedures. Control panels and other station equipment were also improved. All nuclear power plants in the United States have emergency plans in place to quickly notify residents within a 10-mile radius.

Work to eliminate the consequences of the accident began in August 1979 and was officially completed in December. They cost 975 million US dollars. The station area was decontaminated and fuel was unloaded from the reactor. However, some of the radioactive water has been absorbed into the containment concrete, and this radioactivity is almost impossible to remove.

Operation of the station's other reactor (TMI-1) was resumed in 1985.

Film "The China Syndrome"

The accident at the Three Mile Island nuclear power plant occurred a few days after the release of the movie "The China Syndrome", the plot of which is built around an investigation into reliability problems nuclear power plant, conducted by a television journalist and a station employee. One episode depicts an incident very similar to what actually happened at Three Mile Island: an operator, misled by a faulty sensor, turns off the emergency water supply to the core and this almost leads to a meltdown (to " Chinese syndrome"). In another coincidence, one of the characters in the film says that such an accident could lead to the evacuation of people from an area “the size of Pennsylvania.”

Notes

Links

• Chronology of the accident (English)

The accident that occurred on March 28, 1979 at the Three Mile Island nuclear power plant, located near Harrisburg, the capital of Pennsylvania, is considered the worst nuclear accident in the United States. Before the Chernobyl accident, which occurred on April 26, 1986, the Three Mile Island accident was considered the world's worst nuclear accident. As a result of this accident, the station's reactor core was severely damaged, and part of the nuclear fuel melted. One of the results of this accident was that after it the development of nuclear energy in the United States was practically frozen. But despite this, the United States still has the most powerful nuclear power industry in the world.

(Total 18 photos)

1. A policeman and security guards of the nuclear power plant are on duty at the gates of the station. The accident was caused nearby technical faults and obvious errors in the work of the station personnel. Official statistics claims that as a result of this accident, no one died, or even received a serious dose of radiation. Work to eliminate the consequences of the accident was completed only in 1993, and their cost amounted to $975 million. Emergency power unit No. 2 is completely closed and is under constant surveillance. Another power unit of the station continues to operate today.

2. Night shift workers in protective suits enter the station to continue work to shut down the station during the accident. March 29, 1977.

3. The working personnel enters the airlock compartment of the shutdown emergency reactor to carry out the next technical expertise. February 11, 1982.

4. General form Three Mile Island Nuclear Power Plant. March 30, 1979. Power unit No. 2, where the accident occurred on March 28, 1979, is located in the center under the dome.

5. Julie Sipling walks with her one-year-old daughter Debbie near her home, which is located in close proximity to the Three Mile Island nuclear power plant. The photo was taken on the day of the accident, March 29, 1979. The authorities decided that a large-scale evacuation of the population was not necessary, but the governor of Pennsylvania still recommended that pregnant women and preschool children leave the 8-kilometer zone around the emergency reactor.

6. Photo taken on March 30, 1979. Mrs David Neal, along with her daughter Danielle and their pet, are about to leave danger zone around the emergency reactor. Their neighbor, John Switzer, helps them load their things into the car.

7. Cooling tower of the Three Mile Island Nuclear Power Plant for cooling heat exchangers. In the immediate vicinity of the cooling tower there is a children's playroom playground. The photo was taken on March 30, 1979.

8. Deserted street in Goldsboro, Pennsylvania March 31, 1979. Part of the population of this city moved away from the emergency nuclear power plant, while those who could not or did not want to leave tried not to go out unless absolutely necessary. The cooling towers of the Three Mile Island Nuclear Power Plant are visible in the distance. The authorities claimed that as a result of this accident, residents of the 16-kilometer zone around the nuclear power plant received equivalent dose exposure to no more than 100 millirem, which is about one-third of the annual radiation dose Americans receive from natural background radiation.

9. A worker at the Three Mile Island Nuclear Power Plant measures radiation levels on the Susquehanna River, on the banks of which the damaged nuclear power plant is located. The melted nuclear fuel still failed to burn through the reactor vessel, but radioactive water leaked into the concrete of the containment shell, and it was necessary to remove this Nuclear pollution turned out to be almost impossible. The photo was taken on February 11, 1980. The protective building of the shutdown reactor No. 2 can be seen on the right side of the image.

10. A photo of the Three Mile Island Nuclear Power Plant taken shortly before the accident on March 28, 1979 - the largest nuclear accident in USA.

11. Power unit No. 1 of the Three Mile Island nuclear power plant was not damaged during the accident and continues to operate today. In the photo taken on April 15, 1982, nuclear power plant workers inspect the removed reactor head of power unit No. 1.

12. A photo taken on October 31, 1983 shows damaged pipes of the fuel generating unit operating at the emergency power unit No. 2. This power unit was shut down after the accident and is under constant surveillance.

13. Reactor head of power unit No. 2. The photo was taken on August 22, 1980. Technical Experts They suggest that the head is damaged from the inside.

14. US President Jimmy Cartar (center), US Nuclear Energy Agency Director Harold Denton and Pennsylvania Governor Dick Thornburg walk around the emergency control room in protective boots on April 1, 1979.

15. Operating units of power unit No. 1 of the Three Mile Island Nuclear Power Plant. Power unit No. 1 was not damaged during the accident and resumed operation in 1985 after a vote was held among residents of the three districts closest to the station. The photo was taken on March 3, 1999.

Excerpts from the American magazine Nuclear News dated April 6, 1979: “...on March 28, 1979, early in the morning, a major accident occurred in reactor unit No. 2 with a capacity of 880 MW (electric) at the Three Mile Island nuclear power plant, located twenty kilometers from city ​​of Harrisburg (Pennsylvania) and owned by the Metropolitan Edison Company... Unit No. 2 at the Three Mile Island Nuclear Power Plant, as it turned out, was not equipped with an additional safety system, although similar systems are available at some units of this nuclear power plant...

According to Energy Secretary Schlesinger, radioactive contamination in the area around the nuclear power plant is “extremely limited” in size and scope and the public has no reason to worry. Meanwhile, on March 31 and April 1 alone, out of 200 thousand people living within a radius of thirty-five kilometers from the station, about 80 thousand left their homes.

People refused to believe representatives of the Metropolitan Edison company, who tried to convince them that nothing terrible had happened. By order of the state governor, an urgent evacuation plan was drawn up for the entire population of the district. In the area where the nuclear power plant is located, seven schools were closed. The governor ordered the evacuation of all pregnant women and preschool children living within a radius of eight kilometers from the station, and recommended that the population living within a radius of sixteen kilometers not go outside. These actions were taken at the direction of NRC Chairman J. Hendry after a leak of radioactive gases into the atmosphere was discovered. The most critical situation arose on March 30-31 and April 1, when a huge hydrogen bubble formed in the reactor vessel, which threatened to explode the reactor shell; in this case, the entire surrounding area would be subject to severe radioactive contamination.

From the description of the accident

The first signs of an accident were detected at 4 a.m., when for unknown reasons the supply of feedwater to the main pumps to the steam generator stopped. All three emergency pumps had already been under repair for two weeks, which was a gross violation of the operating rules of the nuclear power plant.

As a result, the steam generator could not remove the heat generated by the reactor from the primary circuit. The turbine switched off automatically. In the primary circuit of the reactor block, the temperature and pressure of water increased sharply. Through the safety valve, a mixture of superheated water and steam began to be discharged into a special tank (barbater), however, after the water pressure dropped to a normal level, the valve did not sit in place, as a result of which the pressure in the bubbler also increased beyond the permissible limit. The emergency membrane on the bubbler collapsed, and about 370 cubic meters of hot radioactive water spilled onto the floor.

The drainage pumps turned on automatically; the personnel should have turned them off immediately so that all the radioactive water would remain inside the containment, but this was not done. Water flooded the floor in a layer of several inches, began to evaporate, and radioactive gases, along with steam, penetrated into the atmosphere, which was one of the main reasons for the subsequent radioactive contamination of the area.

At the moment the safety valve opened, the reactor's emergency protection system was activated, releasing the absorber rods, as a result of which the chain reaction stopped and the reactor was practically stopped. The process of fission of uranium nuclei in the fuel rods stopped, but the nuclear decay of fragments continued... The safety valve remained open, the water level in the reactor vessel decreased, and the temperature quickly increased. Apparently, this led to the formation of a steam-water mixture, as a result of which the main circulation pumps failed and they stopped.

As soon as the pressure dropped, the emergency core cooling system was automatically activated, and the fuel assemblies began to cool. This happened two minutes after the accident began. (Here the situation is similar to Chernobyl twenty seconds before the explosion. But in Chernobyl, the emergency core cooling system was turned off by personnel in advance.) Water continued to evaporate from the reactor. The safety valve appeared to be jammed and operators were unable to close it using a remote control. The water level in the reactor dropped, and one third of the core was left without cooling. The protective zirconium shells of the fuel rods began to crack and crumble. Highly active fission products began to emerge from damaged fuel elements.

The primary circuit water became even more radioactive. The temperature inside the reactor vessel exceeded four hundred degrees, and the indicators on the control panel went off scale. The computer that monitored the temperature in the core began to produce continuous question marks and issued them over the next eleven hours...

On the night of March 28-29, a gas bubble began to form in the upper part of the reactor vessel. The core heated up to such an extent that, due to the chemical properties of the zirconium shell of the rods, water molecules split into hydrogen and oxygen. A bubble with a volume of about 30 cubic meters, consisting mainly of hydrogen and radioactive gases - krypton, argon, xenon and others - greatly impeded the circulation of cooling water, since the pressure in the reactor increased significantly. But the main danger was that the mixture of hydrogen and oxygen could explode at any moment (what happened in Chernobyl). The force of the explosion would be equivalent to the explosion of three tons of trinitrotoluene, which would lead to the inevitable destruction of the reactor vessel. In another case, a mixture of hydrogen and oxygen could penetrate from the reactor to the outside and accumulate under the dome of the containment shell. If it had exploded there, all the radioactive fission products would have been released into the atmosphere (which happened at Chernobyl). The radiation level inside the containment shell had reached 30 thousand rem per hour by that time, which was 600 times the lethal dose. In addition, if the bubble continued to grow, it would gradually displace all the cooling water from the reactor vessel and then the temperature would rise so much that the uranium would melt.

On the night of March 30, the volume of the bubble decreased by 20 percent, and on April 2 it was only 1.4 cubic meters. To finally eliminate the bubble and eliminate the danger of explosion, technicians used the so-called water degassing method...

On April 1, President Carter visited the power plant. He appealed to the population to “calmly and accurately” comply with all evacuation rules if the need arises.

In his April 5 speech on energy issues, President Carter spoke at length about alternative methods such as the use of solar energy, oil shale processing, coal gasification, etc., but made no mention at all of nuclear energy, whether fission of the atomic nucleus or controlled thermonuclear fusion.

Many senators say the accident could lead to a “wrenching re-evaluation” of nuclear energy, but they say the country will be forced to continue generating electricity from nuclear power plants because the United States has no other choice. The senators' ambivalent position on this issue clearly demonstrates the predicament in which the US government found itself after the accident...”

The Americans did not close nuclear power plants and abandon nuclear energy, and the share of nuclear energy in the energy balance continued to grow - from 11% of all electricity produced in 1980 to 20.1% in 1992. Now we can say that stabilization has occurred at a level of approximately 20%; since 1992 it has changed very little and in 2001 amounted to 20.7%.

Is it true that US nuclear energy policy is influenced by public anti-nuclear sentiment and numerous green movements? Rather, these sentiments merely provide justification for very specific policies, such as not developing breeder reactor technology.

In June 1996, a Pennsylvania district court dismissed 2,100 lawsuits seeking compensation for personal injury related to the Three Mile Island spill. The court held: “The parties have had nearly two decades to present evidence in support of their claims... The insufficiency of the evidence pleaded in support of the plaintiff is obvious. The court examined all the materials of the case for evidence that, if presented in the most favorable light for the plaintiff, would allow, on the basis of material facts, to transfer the consideration of the claims to the court. This attempt was in vain."

Although numerous studies have confirmed the absence of radiation consequences of the Three Mile Island accident, public attitudes towards this accident and towards nuclear energy itself, as shaped by the media, have remained virtually unchanged. While opinion polls in 1971 showed that 58% of Americans said they would welcome a nuclear power plant where they lived, more recent polls showed that 63% of Americans would avoid such a neighborhood. Polls also noted the following trend: if in the 1950s and 1960s the public had even a fairly exaggerated faith in technological progress, then subsequently trust in science decreased more and more.