Steel Liquidators
In the event of natural or man-made disasters, tanks are often used to deal with rubble and major fires. Converted into civilian versions, with the weapons removed, they are used as all-terrain vehicles, tractors, cleaning and grading equipment, as well as to penetrate into inaccessible places in the conditions of spreading fire or with the threat of collapse of structures. For the last task, the tank was also used during work in the Shelter, erected over the destroyed 4th power unit of the Chernobyl nuclear power plant.
The engineers who created the prototype dismantled the tower, installed a dosimeter, temperature sensor, and illuminator on the tank. The tank was equipped with a remote control, which was carried out by electric cable, in the same way received data from installed tools. From the very first sorties, the tank proved to be very useful for radiation reconnaissance: launching it ahead of people, it was possible to inspect the structures and measure the level of radioactive contamination promptly and without unnecessary risk to the liquidators. In addition, the machine turned out to be very maneuverable and passable due to its small dimensions, crawling among the rubble into the smallest and most uncomfortable passages, and the plastic case was easily amenable to subsequent cleaning and decontamination.
The tank was a toy, and it was one of the most successful robots created and applied at the emergency station.
There is such an Internet meme: at first glance, harmless pictures with the caption "When you notice THIS, you can do it with fear."
In the photo above ( link to the source and the author ) everything seems pretty: a red, seemingly toy excavator is a childhood dream; the same dump truck: kind of toy, but big and serious; between them is a silver lunar rover. This is probably a playground of some school or summer camp, and the APC in the background is, well, for patriotic education.
But no. The very “frightening detail” in the photo is a small triangular sign of radiation hazard in front of the truck. This is an exposition of a small museum of equipment that took part in the liquidation of the accident , and the sign eloquently shows why the exhibits should not be touched.
There is an opinion that when they tried to use robots, they all very quickly failed, they preferred to refuse them, and they began to clean the emergency station with their bare hands, that is, at the cost of the health and life of numerous liquidators. In fact, this is a very controversial statement, and the direct participants in those events argue among themselves. Indeed, during the work of extinguishing, cleaning the roof, decontamination and debris removal, the robots could not fully replace people. They had their serious disadvantages like problems with overcoming blockages and dusting when moving. However, their contribution was still significant - from the notorious roof of the 3rd power unit in two months, fifty tons of sticky bituminous-ruberoid coating was removed, which sorbed radioactive dust on itself in large quantities, and a little less - graphite fragments, the second most hazardous material of the reactor after FCM is fuel-containing materials, as they called ceramics or lava from the frozen melt of concrete and fuel elements. In the future, when it came to conservation, monitoring the state of the destroyed power unit and work inside the Shelter - that is, when there was no longer any need for emergency and dangerous work of hundreds of people at the same time - it was time for robots.
It seems counter-intuitive that metal inanimate robots suffer from radiation. But in fact, this is so: the failure of electronic components under the influence of radioactive radiation occurs much faster than the same radiation incapacitates a living organism. Small deadly shells will bombard a person for a long time from the outside and from the inside (with swallowed or inhaled dust or from neutron guidance) before a painful death occurs; but electronics, being in the limit of binary logic, immediately fails with the smallest, but critical violation.
Of course, in conditions of prolonged low-intensity exposure, the robot will benefit. But with hundreds and thousands of x-rays per hour on the edge of the collapsed roof of the Chernobyl nuclear power plant, its weakest link: semiconductors will very quickly fail. Semiconductors are both microcircuits and the simplest transistors that suffer from irradiation for exactly the same reason that they themselves work: the movement of charge carriers in a semiconductor material is disrupted by radioactive charge carriers piercing the robot body.
Under the deadly shower of charged particles, two main mechanisms of damage to electronics are realized.
First, neutrons, protons and alpha particles damage the crystal lattice of a semiconductorreplacing atoms with isotopes or even other elements, causing local defects. This greatly affects the mobility of charge carriers, the number of recombinations, as well as the properties of the pn junction in transistors. Interestingly, short-term high-energy irradiation causes a “tempering effect”, named after metal hardening: the grating is slightly restored compared to the degradation caused by continuous, but less powerful radiation. However, for bipolar transistors, this factor becomes the main reason for the loss of output characteristics.
Secondly, particles with lower energy than that required for atomic substitutions in the crystal lattice cause ionization effects. This results in all kinds of electrical noise, induced noise, photoelectric effect and transmission errors in the optocouplers, the degradation of MOS transistors, as well as software malfunctions.
Apart from all types of irradiation, neutrons are capable of both the above interaction with the atomic nuclei in the crystal and the generation of secondary radiation - “shrapnel” from collisions with the material. Bipolar transistors are most sensitive to them, because when neutrons penetrate the crystal lattice, they can create “deep traps” in it, that is, places with an anomalously large band gap- energy to transfer the charge carrier to the level of conductivity. They withstand flux densities up to the order of giga-neutrons per square cm, CMOS schemes - petaneutrons per square. see. In the general case, CMOS chips can withstand a dose of up to 100 gray radiation. For comparison, the lethal dose for a person is about 5 Gray, and given that Gray is the number of radiation joules per kg of mass and the difference in mass between a microcircuit and a person, this looks quite good. Until the robot is exposed to thousands of x-rays per hour. But there are technologies that make it possible to increase the radiation resistance of a semiconductor crystal by orders of magnitude, for example, growing it on a sapphire substrate . It is also possible both circuitry and logic (increasing the number of control bits) to increase the reliability of electronic systems.
At first, robots worked in parallel with human liquidators. Both on the ground and on the roof of the station, where soil or ruberoid flooring and concrete chips were mixed with real mines in the form of fragments of graphite assembly and fuel cells, it was necessary to carry out decontamination work as soon as possible.
One of the first to come into operation remotely controlled production complexes VNII-100 (now VNIITransmash). Already on May 18 from the chief designer Alexander Leonovich Kemurdzhian, urgently delivered to the disaster zone, the government commission demanded: "You made the country a Lunokhod remotely controlled - put it on the roof to clean it!" In response to irritated objections that the Lunokhod was not suitable for these tasks, Kemurdzhian received an even more categorical answer: “Then make us a new car!” The
new cars were made in a very short time. First of all, in just 44 days, Klin-1 was created. It was a calculation of two tracked vehicles: the Object 032 grader, created on the basis of the IMR-1 demolition engineering machine with additional decontamination equipment, shielding and a radio control system, as well as the Object 033 control vehicle based on the T-72 tank.
From top to bottom: Objects 032 and 033. The control car was inhabited and was in a safe place, while the radio-controlled bulldozer-deactivator worked in the most dangerous zone. The whole complex helped to remove, load into wagons and take out almost 1.5 thousand cubic meters of contaminated soil.
Lunokhod was also made. "Klin-2", better known as "STR-1" or a specialized transport robot, was the most effective in terms of cleaning the roof of the 3rd power unit.
The machine weighing almost a ton was delivered to the roof by helicopter or crane, and after work, drove into a special platform and moved the same way back to the ground for decontamination and recharging. Engineers took a serious approach to the chassis so that the robot could move as sticky as possible from the heat (and to prevent the erosion of radioactive contamination over a large area with sewage from showers, “Carcasses” with silver iodide charges circled for a long time) bitumen-ruberoid coverage. It was necessary that the bitumen does not stick to the wheels, and at the same time that the wheels cling well to it, removing it from the roof along with melted radioactive debris. Two machines STR-1 coped with this task, having cleared more than 3,000 square meters by the end of September. m of the roof.
The radiation stability of the components was manifested, firstly, in the inheritance of space technology - experience in the development of components protected from the action of cosmic rays already existed. Secondly, faultless control methods were used: in the circuitry itself, relay assemblies were used to the maximum, and remote control went through protected radio channels.
In addition to VNII-100, the machines of the Leningrad Central Research Institute of the RTK worked in the accident. There were more than different sizes, but they were subjected to significant criticism for poor handling, outages, and slowness. In the framework of this article, having been born after the events described and not being a specialist, I will not undertake to strictly affirm something. From the sources I found, the son of Kemurdzhian in his lecture on the 30th anniversary of the accident talks about about 1000 people (referring to work shifts equivalent to recruiting one permissible single dose for the liquidator), which were replaced by STR-1. Valery Starodumov in a television movie released at the same time speaks of 800 people who were required to service failed robots. I’ll just recommend that you yourself see both sources, they are very interesting.
Remote-controlled self-propelled units appeared after the analysis of the rubble and the construction of the Shelter. They solved other tasks - investigation of the state of structures, search for fuel (at first no one knew that there was no graphite assembly and fuel elements in the former reactor core - everything melted and leaked into the subreactor space) and especially infected places.
After the construction of the Shelter, at first no one used robots - the study of the premises was successfully carried out by drilling wells and introducing probes with the necessary sensors for exploration. Later, when primary intelligence provided basic data on the location of fuel-containing materials (FCM) and the state of structures, robots began to be actively developed and applied to obtain new data and a television picture from the workplace.
The requirements for finished machines were as follows. In addition to radiation protection, moisture and dust protection were required. A humid climate remained under the Shelter, and radioactive dust required the robots to be covered with a special cloth to facilitate decontamination. Reliability and throughput was ensured by the unification of nodes, the chassis, the reduction in size, the use of independent suspension of the wheels of the trolley. Remote control and reception of signals were carried out by cable - the radio signal was jammed by the concrete structures of the station.
Based on standard chassis, robots were created for the following tasks:
DUSA carts on trials. Pay attention to the insulating fabric. The source of the photo here and below.
Interesting examples are also robots with special ways of moving. In the completely destroyed area of the power unit, rails were laid along which the DUSA moved.
Moving in the air over colossal destruction, impassable for any kind of equipment, a robot with a television camera made it possible to map in great detail both the degree of damage to rooms and structures, and the location of radioactive debris.
A completely exotic machine was a magnetic sink. It was created for work on the walls and ceilings of rooms with cladding that can magnetize. The robot running gears contained powerful samarium-cobalt magnets, which allowed the robot moving along this surface to carry significant weight. Dual wheel blocks increased meshing reliability when overcoming welds and fragments of non-magnetic coatings. In 1990–91 the magnetic flux was tested in the laboratory and used at the Shelter to install heat sensors in the rooms of the steam distribution corridor. In preparation for the stabilization of the Shelter structures, he measured the dose fields on the north buttress wall:
In more detail, with all the technical characteristics, all these devices are described in this book:A.A. Borovoy, E.P. Velikhov. The experience of Chernobyl , and I do not see the need to re-word-by-word material from there, since that work covers many more aspects of the accident and is beautifully illustrated.
It is noteworthy that the robots still had to repeat this path a quarter century later on the other side of the globe in the well-known accident at Fukushima. And this path was also very thorny.
The engineers who created the prototype dismantled the tower, installed a dosimeter, temperature sensor, and illuminator on the tank. The tank was equipped with a remote control, which was carried out by electric cable, in the same way received data from installed tools. From the very first sorties, the tank proved to be very useful for radiation reconnaissance: launching it ahead of people, it was possible to inspect the structures and measure the level of radioactive contamination promptly and without unnecessary risk to the liquidators. In addition, the machine turned out to be very maneuverable and passable due to its small dimensions, crawling among the rubble into the smallest and most uncomfortable passages, and the plastic case was easily amenable to subsequent cleaning and decontamination.
The tank was a toy, and it was one of the most successful robots created and applied at the emergency station.
Gloomy toys
There is such an Internet meme: at first glance, harmless pictures with the caption "When you notice THIS, you can do it with fear."
In the photo above ( link to the source and the author ) everything seems pretty: a red, seemingly toy excavator is a childhood dream; the same dump truck: kind of toy, but big and serious; between them is a silver lunar rover. This is probably a playground of some school or summer camp, and the APC in the background is, well, for patriotic education.
But no. The very “frightening detail” in the photo is a small triangular sign of radiation hazard in front of the truck. This is an exposition of a small museum of equipment that took part in the liquidation of the accident , and the sign eloquently shows why the exhibits should not be touched.
There is an opinion that when they tried to use robots, they all very quickly failed, they preferred to refuse them, and they began to clean the emergency station with their bare hands, that is, at the cost of the health and life of numerous liquidators. In fact, this is a very controversial statement, and the direct participants in those events argue among themselves. Indeed, during the work of extinguishing, cleaning the roof, decontamination and debris removal, the robots could not fully replace people. They had their serious disadvantages like problems with overcoming blockages and dusting when moving. However, their contribution was still significant - from the notorious roof of the 3rd power unit in two months, fifty tons of sticky bituminous-ruberoid coating was removed, which sorbed radioactive dust on itself in large quantities, and a little less - graphite fragments, the second most hazardous material of the reactor after FCM is fuel-containing materials, as they called ceramics or lava from the frozen melt of concrete and fuel elements. In the future, when it came to conservation, monitoring the state of the destroyed power unit and work inside the Shelter - that is, when there was no longer any need for emergency and dangerous work of hundreds of people at the same time - it was time for robots.
Isn’t it?
It seems counter-intuitive that metal inanimate robots suffer from radiation. But in fact, this is so: the failure of electronic components under the influence of radioactive radiation occurs much faster than the same radiation incapacitates a living organism. Small deadly shells will bombard a person for a long time from the outside and from the inside (with swallowed or inhaled dust or from neutron guidance) before a painful death occurs; but electronics, being in the limit of binary logic, immediately fails with the smallest, but critical violation.
Of course, in conditions of prolonged low-intensity exposure, the robot will benefit. But with hundreds and thousands of x-rays per hour on the edge of the collapsed roof of the Chernobyl nuclear power plant, its weakest link: semiconductors will very quickly fail. Semiconductors are both microcircuits and the simplest transistors that suffer from irradiation for exactly the same reason that they themselves work: the movement of charge carriers in a semiconductor material is disrupted by radioactive charge carriers piercing the robot body.
Under the deadly shower of charged particles, two main mechanisms of damage to electronics are realized.
First, neutrons, protons and alpha particles damage the crystal lattice of a semiconductorreplacing atoms with isotopes or even other elements, causing local defects. This greatly affects the mobility of charge carriers, the number of recombinations, as well as the properties of the pn junction in transistors. Interestingly, short-term high-energy irradiation causes a “tempering effect”, named after metal hardening: the grating is slightly restored compared to the degradation caused by continuous, but less powerful radiation. However, for bipolar transistors, this factor becomes the main reason for the loss of output characteristics.
Secondly, particles with lower energy than that required for atomic substitutions in the crystal lattice cause ionization effects. This results in all kinds of electrical noise, induced noise, photoelectric effect and transmission errors in the optocouplers, the degradation of MOS transistors, as well as software malfunctions.
Apart from all types of irradiation, neutrons are capable of both the above interaction with the atomic nuclei in the crystal and the generation of secondary radiation - “shrapnel” from collisions with the material. Bipolar transistors are most sensitive to them, because when neutrons penetrate the crystal lattice, they can create “deep traps” in it, that is, places with an anomalously large band gap- energy to transfer the charge carrier to the level of conductivity. They withstand flux densities up to the order of giga-neutrons per square cm, CMOS schemes - petaneutrons per square. see. In the general case, CMOS chips can withstand a dose of up to 100 gray radiation. For comparison, the lethal dose for a person is about 5 Gray, and given that Gray is the number of radiation joules per kg of mass and the difference in mass between a microcircuit and a person, this looks quite good. Until the robot is exposed to thousands of x-rays per hour. But there are technologies that make it possible to increase the radiation resistance of a semiconductor crystal by orders of magnitude, for example, growing it on a sapphire substrate . It is also possible both circuitry and logic (increasing the number of control bits) to increase the reliability of electronic systems.
Wedge
At first, robots worked in parallel with human liquidators. Both on the ground and on the roof of the station, where soil or ruberoid flooring and concrete chips were mixed with real mines in the form of fragments of graphite assembly and fuel cells, it was necessary to carry out decontamination work as soon as possible.
One of the first to come into operation remotely controlled production complexes VNII-100 (now VNIITransmash). Already on May 18 from the chief designer Alexander Leonovich Kemurdzhian, urgently delivered to the disaster zone, the government commission demanded: "You made the country a Lunokhod remotely controlled - put it on the roof to clean it!" In response to irritated objections that the Lunokhod was not suitable for these tasks, Kemurdzhian received an even more categorical answer: “Then make us a new car!” The
new cars were made in a very short time. First of all, in just 44 days, Klin-1 was created. It was a calculation of two tracked vehicles: the Object 032 grader, created on the basis of the IMR-1 demolition engineering machine with additional decontamination equipment, shielding and a radio control system, as well as the Object 033 control vehicle based on the T-72 tank.
From top to bottom: Objects 032 and 033. The control car was inhabited and was in a safe place, while the radio-controlled bulldozer-deactivator worked in the most dangerous zone. The whole complex helped to remove, load into wagons and take out almost 1.5 thousand cubic meters of contaminated soil.
Lunokhod was also made. "Klin-2", better known as "STR-1" or a specialized transport robot, was the most effective in terms of cleaning the roof of the 3rd power unit.
The machine weighing almost a ton was delivered to the roof by helicopter or crane, and after work, drove into a special platform and moved the same way back to the ground for decontamination and recharging. Engineers took a serious approach to the chassis so that the robot could move as sticky as possible from the heat (and to prevent the erosion of radioactive contamination over a large area with sewage from showers, “Carcasses” with silver iodide charges circled for a long time) bitumen-ruberoid coverage. It was necessary that the bitumen does not stick to the wheels, and at the same time that the wheels cling well to it, removing it from the roof along with melted radioactive debris. Two machines STR-1 coped with this task, having cleared more than 3,000 square meters by the end of September. m of the roof.
The radiation stability of the components was manifested, firstly, in the inheritance of space technology - experience in the development of components protected from the action of cosmic rays already existed. Secondly, faultless control methods were used: in the circuitry itself, relay assemblies were used to the maximum, and remote control went through protected radio channels.
In addition to VNII-100, the machines of the Leningrad Central Research Institute of the RTK worked in the accident. There were more than different sizes, but they were subjected to significant criticism for poor handling, outages, and slowness. In the framework of this article, having been born after the events described and not being a specialist, I will not undertake to strictly affirm something. From the sources I found, the son of Kemurdzhian in his lecture on the 30th anniversary of the accident talks about about 1000 people (referring to work shifts equivalent to recruiting one permissible single dose for the liquidator), which were replaced by STR-1. Valery Starodumov in a television movie released at the same time speaks of 800 people who were required to service failed robots. I’ll just recommend that you yourself see both sources, they are very interesting.
DUSA
Remote-controlled self-propelled units appeared after the analysis of the rubble and the construction of the Shelter. They solved other tasks - investigation of the state of structures, search for fuel (at first no one knew that there was no graphite assembly and fuel elements in the former reactor core - everything melted and leaked into the subreactor space) and especially infected places.
After the construction of the Shelter, at first no one used robots - the study of the premises was successfully carried out by drilling wells and introducing probes with the necessary sensors for exploration. Later, when primary intelligence provided basic data on the location of fuel-containing materials (FCM) and the state of structures, robots began to be actively developed and applied to obtain new data and a television picture from the workplace.
The requirements for finished machines were as follows. In addition to radiation protection, moisture and dust protection were required. A humid climate remained under the Shelter, and radioactive dust required the robots to be covered with a special cloth to facilitate decontamination. Reliability and throughput was ensured by the unification of nodes, the chassis, the reduction in size, the use of independent suspension of the wheels of the trolley. Remote control and reception of signals were carried out by cable - the radio signal was jammed by the concrete structures of the station.
Based on standard chassis, robots were created for the following tasks:
- Deactivation. The robot drove into the room, spraying there with a hose and nozzle a decontamination solution and then applying a dust coating on the walls, ceiling and floor.
- Concrete sampling. Robots were created with manipulators that allowed drilling walls and samples of solidified fuel melt and structures for collecting samples for the purpose of subsequent analysis.
- Television intelligence. To assess the damage caused by the explosion, as well as to carry out many works, including other DUSA, specialized surveillance machines with powerful light sources and television cameras mounted on them were created.
DUSA carts on trials. Pay attention to the insulating fabric. The source of the photo here and below.
Interesting examples are also robots with special ways of moving. In the completely destroyed area of the power unit, rails were laid along which the DUSA moved.
Moving in the air over colossal destruction, impassable for any kind of equipment, a robot with a television camera made it possible to map in great detail both the degree of damage to rooms and structures, and the location of radioactive debris.
A completely exotic machine was a magnetic sink. It was created for work on the walls and ceilings of rooms with cladding that can magnetize. The robot running gears contained powerful samarium-cobalt magnets, which allowed the robot moving along this surface to carry significant weight. Dual wheel blocks increased meshing reliability when overcoming welds and fragments of non-magnetic coatings. In 1990–91 the magnetic flux was tested in the laboratory and used at the Shelter to install heat sensors in the rooms of the steam distribution corridor. In preparation for the stabilization of the Shelter structures, he measured the dose fields on the north buttress wall:
In more detail, with all the technical characteristics, all these devices are described in this book:A.A. Borovoy, E.P. Velikhov. The experience of Chernobyl , and I do not see the need to re-word-by-word material from there, since that work covers many more aspects of the accident and is beautifully illustrated.
It is noteworthy that the robots still had to repeat this path a quarter century later on the other side of the globe in the well-known accident at Fukushima. And this path was also very thorny.