Nuclear power plant for rockets. History of domestic space nuclear installations Nuclear power plant for rockets

In 2009, the Commission under the President of the Russian Federation for the modernization and technological development of the Russian economy decided to implement the project “Creation of a transport and energy module based on a megawatt-class nuclear power plant.”
JSC NIKIET was appointed as the Chief Designer of the reactor plant.
The Federal Space Agency issued NIKIET license No. 981K dated August 29, 2008 to carry out space activities.

From an interview with Yu.G. Dragunov RIA "". Published 08/28/2012

Russia is actively developing nuclear energy, relying on the enormous experience and knowledge accumulated over decades of the domestic nuclear program.
One of the pioneers in creating breakthrough technologies in our country and in the world is the Research and Design Institute of Energy Engineering named after N.A. Dollezhal (NIKIET), celebrating its 60th anniversary this year. The institute's specialists made an invaluable contribution to the defense capability of our country, developed designs for the first reactor for producing weapons-grade isotopes, the first reactor installation for a nuclear submarine, and the first power reactor for a nuclear power plant. Based on projects and with the participation of NIKIET, 27 research reactors have been created in Russia and abroad.
And today the Institute is constructing completely new reactors, working on creating a reactor installation for a unique megawatt-class nuclear power plant for a spacecraft, which has no analogues in the world.
Director - General Designer of NIKIET, Corresponding Member of the Russian Academy of Sciences Yuri Grigorievich Dragunov told RIA Novosti about how work is progressing in breakthrough areas of Russian nuclear science and technology.
- The Institute is creating a unique nuclear engine for a new Russian spacecraft. At what stage is this project now?
- Throughout the 60 years of its existence, the Institute has followed the motto of the founder and first director of NIKIET, academician N.A. Dollezhal: “If you can, go ahead of the century.” And this project is proof of this. The creation of this installation is a complex work of the State Research Center FSUE "Keldysh Center", OJSC RSC Energia, KBKhM im. A.M. Isaev and enterprises of the State Corporation "Rosatom". Our Institute is designated as the sole contractor for the reactor installation and is designated as the coordinator of work from Rosatom organizations. The work is truly unique, there are no analogues today, so it is quite difficult. Since we are a design organization, we have certain steps, stages, and we go through them step by step. Last year we completed the development of the preliminary design of the reactor plant, and this year we are completing the technical design of the reactor plant. A huge amount of testing is required, especially on fuel, including studies of the behavior of fuel and structural materials under reactor conditions. The work on the technical project will be quite long, approximately 3 years, but we will prepare the first stage of the technical project, the main documentation, this year. Today we have identified and made a technical decision on the choice of the fuel element design option and the final technical decision on the choice of the reactor design option. And just a couple of weeks ago we made a technical decision on the choice of design option for the core and its layout.
- What problems are there? Is everything really going that smoothly?
- Today we have quite broad cooperation, more than three dozen organizations are participating in the development of the reactor plant project. All agreements on this topic have been concluded, and there is complete confidence that we will complete this work on time. The work is coordinated by the project manager’s council, chaired by me, and we review the status of the work once a quarter. There is one problem, I cannot help but mention it. Unfortunately, as elsewhere on all subjects, our contracts are concluded for a period of one year. The conclusion process is drawn out, and, taking into account the time for competitive procedures, we are actually eating up our time. At NIKIET I made a decision; we are opening a special order and starting work on January 11th. But it is much more difficult to attract participants. There is a problem, so today we asked our participants to give plans for at least a three-year period before the development is completed. We are forming these proposals, and we will go to the government with a request to switch to a three-year contract for this project. Then we will clearly see the schedule and better organize and coordinate the work on the project. Solving this problem is very important for the successful implementation of the project.
- This will be a purely Russian project; you will not attract any foreign partners for R&D?
- I think that the project will be purely Russian. There is still a lot of know-how here, many new solutions and, in my opinion, the project should be purely Russian.
- What kind of fuel will be in the space reactor installation?
- Fundamentally, at this stage of the technical project, the option of dioxide fuel was adopted. The fuel that has experience in operation in installations with thermal emission. We made the fuel element sectional to ensure the conditions that have already been tested in operating reactors. Yes, this is a novelty, yes, this is an innovative project, but the key elements must be worked out and must be completed within the deadlines set by the presidential project.
- Are you considering the option of reloading fuel in the installation?
- No, we are not considering the option of overloading today. It may be reusable, but we expect 10 years of operation, and I believe, judging by the results of discussions in the scientific community, with Roscosmos, that today the task of making the installation work longer is not set. Roscosmos is discussing increasing the power of the installation, but this, in general, will not be a problem if we complete this project, implement it and, most importantly, test a ground-based prototype at the stand. After that, we can easily process it to greater power.

Creation of nuclear power and power propulsion systems for space purposes

From 1960 to 1989, work was carried out at the Semipalatinsk test site to create a nuclear rocket engine.

Were created:

IGR reactor complex;
bench complex "Baikal-1" with an IVG-1 reactor and two workstations for testing 11B91 products;
RA reactor (IRGIT).

IGR reactor

The IGR reactor is a pulsed thermal neutron reactor with a homogeneous core, which is a stack of uranium-containing graphite blocks assembled in the form of columns. The reactor reflector is formed from similar blocks that do not contain uranium.

The reactor does not have forced cooling of the core. The heat released during reactor operation is accumulated by the masonry, and then transferred through the walls of the reactor vessel to the water of the cooling circuit.

IGR reactor

IVG-1 reactor and component supply systems

Reactor RA (IRGIT)

Results achieved

1962-1966

The first tests of model NRE fuel rods were carried out in the IGR reactor. The test results confirmed the possibility of creating fuel elements with solid heat exchange surfaces operating at temperatures above 3000K, specific heat fluxes up to 10 MW/m2 under conditions of powerful neutron and gamma radiation (41 launches were carried out, 26 model fuel assemblies of various modifications were tested).

1971-1973

Dynamic tests of high-temperature NRE fuel for thermal strength were carried out in the IGR reactor, during which the following parameters were realized:

Specific energy release in fuel – 30 kW/cm3
specific heat flux from the surface of fuel elements – 10 MW/m2
coolant temperature – 3000K
rate of change in coolant temperature with increasing and decreasing power – 1000 K/s
duration of nominal mode – 5 s

1974-1989

In the IGR reactor, fuel assemblies of various types of nuclear-powered reactors, nuclear propulsion units and gas-dynamic plants with hydrogen, nitrogen, helium and air coolants were tested.

1971-1993

Research was carried out on the release of fuel into a gaseous coolant (hydrogen, nitrogen, helium, air) in the temperature range 400...2600K and the deposition of fission products in gas circuits, the sources of which were experimental fuel assemblies located in the IGR and RA reactors.

Comparative indicators of the results obtained at the IVG-1 reactor
and according to nuclear powered rocket development programs in the USA

USSR
1961-1989
Funds spent, $ billion ~ 0,3
5
element-wise
Fuel composition
UC-ZrC,
UC-ZrC-NbC

average/maximum, MW/l 15 / 33
3100
Specific thrust impulse, s ~ 940
4000

USA
Period of active actions on the topic 1959-1972
Funds spent, $ billion ~2,0
Number of reactor units manufactured 20
Principles of development and creation integral
Fuel composition Solid solution
UC2 in graphite
matrix
Thermal intensity of the active zone,
average/maximum, MW/l 2,3 / 5,1
Maximum achieved temperature of the working fluid, K 2550 2200
Specific thrust impulse, s ~ 850
Operating life at maximum working fluid temperature, s 50 2400

Yesterday, without any exaggeration, we witnessed an epoch-making event that opens up new, absolutely fantastic prospects for military equipment and (in the future) energy and transport in general.

But first, I would like to understand how the nuclear power plant for missiles and underwater vehicles that Putin spoke about works. What exactly is the driving force in it? Where does the traction come from? Not due to the neutrons escaping from the nozzle...

When I learned from a colleague’s words that we had created missiles with an almost unlimited flight range, I was stunned. It seemed that he was missing something, and the word "unlimited" was mentioned in some narrow sense.

But the information then obtained from the primary source did not raise any doubts. Let me remind you, it sounded like this:

One of them is the creation of a small-sized, super-powerful nuclear power plant, which is placed in the body of a cruise missile such as our newest air-launched X-101 missile or the American Tomahawk, but at the same time provides tens of times - tens of times! – long flight range, which is practically unlimited.

It was impossible to believe what he heard, but it was impossible not to believe - HE said it. I turned on my brain and immediately received an answer. Yes what!

Well, damn it! Well, geniuses! This would never even occur to a normal person!

So, until now we only knew about nuclear propulsion systems for space rockets. Space rockets necessarily contain a substance that, when heated or accelerated by an accelerator powered by a nuclear power plant, is forcefully ejected from the rocket nozzle and provides it with thrust.

In this case, the substance is consumed and the engine operating time is limited.

Such missiles have already existed and will continue to exist. But how does a new type of missile move if its range is “virtually unlimited”?

Nuclear power plant for rockets

Purely theoretically, in addition to the thrust from the substance available on the rocket, the rocket’s movement is possible due to the thrust of electric motors with “propellers” (screw engine). Electricity is produced by a generator powered by a nuclear power plant.

But such a mass cannot be kept in the air without a large propeller-driven wing, and even with small-diameter propellers - such thrust is too small. But this is a rocket, not a drone.

So, what remains is the most unexpected and, as it turns out, the most effective way of providing a rocket with substance for thrust - taking it from the surrounding space.

That is, no matter how surprising it may sound, the new rocket works “in air”!

In the sense that it is precisely heated air that escapes from its nozzle and nothing more! And the air will not run out while the rocket is in the atmosphere. That is why this missile is a cruise missile, i.e. its flight takes place entirely in the atmosphere.

Classic long-range missile technologies tried to make the missile fly higher to reduce friction with the air and thereby increase their range. As always, we broke the mold and made a rocket that was not just large, but had an unlimited range in the air.

Unlimited flight range makes it possible for such missiles to operate in standby mode. The launched missile arrives at the patrol area and circles there, waiting for additional reconnaissance of data about the target or the target's arrival in the area. After which, unexpectedly for the target, it immediately attacks it.

Nuclear power plant for underwater vehicles

I think the nuclear power plant for the underwater vehicles that Putin spoke about is similar. With the exception that water is used instead of air.

Additionally, this is evidenced by the fact that these underwater vehicles have low noise. The famous Shkval torpedo, developed back in Soviet times, had a speed of about 300 km/h, but was very noisy. Essentially it was a rocket flying in an air bubble.

Behind the low noise is a new principle of movement. And it is the same as in the rocket, because it is universal. There would only be an environment of the minimum required density.

The name “Squid” would be a good fit for this device, because in essence it is a water-jet engine in a “nuclear version” :)

As for speed, it is many times greater than the speed of the fastest surface ships. The fastest ships (namely ships, not boats) have speeds of up to 100-120 km/h. Therefore, with a minimum coefficient of 2 we get a speed of 200-250 km/h. Under the water. And not very noisy. And with a range of many thousands of kilometers... A nightmare for our enemies.

The relatively limited range compared to a missile is a temporary phenomenon and is explained by the fact that high-temperature sea water is a very aggressive environment and the materials of the combustion chamber, relatively speaking, have a limited resource. Over time, the range of these devices can be increased significantly only through the creation of new, more stable materials.

Nuclear power plant

A few words about the nuclear power plant itself.

1. Putin’s phrase amazes the imagination:

With a volume one hundred times smaller than that of modern nuclear submarine installations, it has greater power and 200 times less time to reach combat mode, that is, to maximum power.

Again some questions.
How did they achieve this? What design solutions and technologies are used?

These are the thoughts.

1. A radical, two orders of magnitude, increase in power output per unit mass is possible only if the operating mode of a nuclear reactor approaches an explosive one. At the same time, the reactor is reliably controlled.

2. Since near-explosive operation is reliably ensured, most likely this is a fast neutron reactor. In my opinion, only they can safely use such a critical operating mode. By the way, for them the fuel on Earth lasts for centuries.

3. If over time we find out that this is a slow neutron reactor, I take off my hat to our nuclear scientists, because without an official statement it is absolutely impossible to believe.

In any case, the courage and ingenuity of our nuclear scientists is amazing and worthy of the loudest words of admiration! It’s especially nice that our guys know how to work in silence. And then they hit you over the head with the news - either stand or fall! :)

How it works
An approximate, semantic diagram of the operation of a rocket engine based on a nuclear power plant looks like this.

1. The inlet valve opens, relatively speaking. The incoming air flow passes through it into the heating chamber, which is constantly heated by the operation of the reactor.

2. The inlet valve closes.

3. The air in the chamber heats up.

4. The exhaust valve opens and air escapes from the rocket nozzle at high speed.

5. The outlet valve closes.

The cycle repeats with high frequency. Hence the effect of continuous operation.

P.S. The mechanism described above, I repeat, is semantic. It is given at the request of readers for a better understanding of how this engine can generally work. In reality, it is possible that a ramjet engine was implemented. The main thing in this article is not determining the type of engine, but identifying the substance (incoming air) that is used as the only working fluid that provides thrust to the rocket.

Safety

The use of the discovery of Russian scientists in the civilian sector is closely related to the safety of the nuclear power plant. Not in the sense of its possible explosion - I think this issue has been resolved - but in the sense of the safety of its exhaust.

The protection of a small-sized nuclear engine is clearly less than that of a large one, so neutrons will certainly penetrate into the “combustion chamber,” or rather, the air heating chamber, thereby with some probability making everything radioactive that can be made radioactive in the air.

Nitrogen and oxygen have radioactive isotopes with a short half-life and are not dangerous. Radioactive carbon is a long-lived thing. But there is also good news.

Radioactive carbon is formed in the upper layers of the atmosphere under the influence of cosmic rays and so it will not be possible to blame everything on nuclear engines. But most importantly, the concentration of carbon dioxide in dry air is only 0.02÷0.04%.

Considering that the percentage of carbon that becomes radioactive is still several orders of magnitude smaller, we can tentatively assume that the exhaust from nuclear engines is no more dangerous than the exhaust from a coal-fired thermal power plant.

More accurate information will appear when it comes to the civilian use of these engines.

Prospects

Honestly, the prospects are breathtaking. Moreover, I’m not talking about military technologies, everything is clear here, but about the use of new technologies in the civilian sector.

Where can nuclear power plants be used? So far, offhand, purely theoretically, in the future 20-30-50 years.

1. Fleet, including civil and transport. Much will have to be converted to hydrofoils. But the speed can easily be doubled/tripled, and the cost of operation will only fall over the years.

2. Aviation, primarily transport. Although, if safety in terms of the risk of exposure turns out to be minimal, it may also be used for civil transport.

3. Aviation with vertical take-off and landing. Using compressed air tanks replenished during flight. Otherwise, at low speeds, the necessary traction cannot be provided.

4. Locomotives of high-speed electric trains. Using an intermediate electric generator.

5. Electric trucks. Also, of course, using an intermediate electric generator. This, I think, will happen in the distant future, when power plants can be reduced several times more. But I would not rule out this possibility.

This is not to mention the land/mobile use of nuclear power plants. One problem is that the operation of such small-sized nuclear reactors requires not uranium/plutonium, but much more expensive radioactive elements, the production of which in nuclear reactors is still very, very expensive and takes time. But this problem can also be solved over time.

Friends, a new era has been marked in the field of energy and transport. Apparently, Russia will become the leader in these areas for the coming decades.

Please accept my congratulations.
It will not be boring!

The first widespread use of atomic batteries was found in space, since it was there that energy sources were required that were capable of generating heat and electricity for a long time, under conditions of sharp and very strong temperature changes, under significant variable loads, and since, in conditions of unmanned flights, radio emission from the power source did not pose a big threat (there is enough radiation in space even without it). Chemical energy sources have not proven their worth. Thus, when the first artificial Earth satellite was launched into orbit on October 4, 1957 in the USSR, its chemical batteries could provide energy for 23 days. After this, their power was exhausted. Silicon solar cells are effective only for flights near the Sun; they are not suitable for flights to distant planets of the solar system.

There are two types of energy conversion methods on spacecraft: direct and mechanical. Types of thermal energy converters into electrical energy are divided into static (i.e. without moving parts) and dynamic (i.e. with moving, rotating or moving parts). The problem of choosing the type of energy conversion still remains relevant for developers of various converters and space nuclear power plants (SNPPs) based on them.

Thus, within the framework of the well-known NASA initiative on space nuclear power plants, a dynamic converter (gas-turbine installation based on the Brayton cycle) was selected for the implementation of the Prometheus program for the Jimo project (orbital expedition to the icy moons of Jupiter). The service life of the nuclear power plant is 10 years with an electrical output power of 250 kW(el).

Since the early sixties, work on the direct conversion of thermal energy into electrical energy based on thermoelectric and thermionic converters has gained quite a wide scope in the USSR, the USA and a number of other countries. Such energy conversion methods fundamentally simplify the design of installations, eliminate intermediate stages of energy conversion and make it possible to create compact and lightweight energy installations.

The USSR used nuclear batteries in Cosmos-type satellites. In September 1965, radioisotope thermoelectric generators (RTGs) Orion-1 with an electrical power of 20 W were launched as part of the Cosmos-84 and Cosmos-90 devices. The weight of the RTG was 14.8 kg, the design life was 4 months. RTG ampoules containing polonium-210 were designed in accordance with the principle of guaranteed integrity and tightness in all accidents. This principle was justified during launch vehicle accidents in 1969, when, despite the complete destruction of the objects, the fuel block containing 25,000 curies of polonium-210 remained sealed.

The Lunokhod 1 research vehicle, launched onto the lunar surface by the Soviet Union in November 1970, was equipped with radioactive isotopes (polonium-210) to regulate temperature. Lunokhod 1 operated for 322 days. Over 11 lunar days, he covered 10.5 km, exploring the region of the Sea of ​​Rains, and carried out a detailed topographic survey of 80,000 sq.m. lunar surface. During this time, 171 communication sessions were carried out using the Lunokhod-1 radio and television systems, and over 200 thousand images of the lunar surface were transmitted to Earth.” The radioisotope thermoelectric current generator also operated successfully on the Lunokhod-2 spacecraft.

Energy sources supplied with long-lived isotopes are especially necessary for space probes on “long journeys” to distant planets. Therefore, the American Viking probes, which were landed on Mars in July and September 1976 with the aim of searching for intelligent life there, had two radioisotope generators on board to provide energy to the descent vehicle. Space stations near the Earth, such as Salyut (USSR) and Skylab (USA), receive energy from solar panels powered by solar energy. However, probes for Jupiter cannot be equipped with solar panels. The solar radiation received by the probe near distant Jupiter is completely insufficient to provide energy to the device. In addition, during a space flight from Earth to Jupiter, it is necessary to overcome enormous interplanetary distances with a flight duration of 600 to 700 days. For such space missions, the basis of success is the reliability of power plants. Therefore, the American probes of the planet Jupiter - Pioneer 10, which launched in February 1972, and in December 1973 reached its closest approach to Jupiter, as well as its successor Pioneer 2 - were equipped with four powerful plutonium-238 batteries placed at the ends of brackets 27 m long. In 1987, Pioneer 10 flew past the most distant planet from the Earth - Pluto, and then this cosmic body produced on earth left our solar system.

Table 1 Main characteristics of nuclear power plants that have received real experience of use as part of spacecraft in the USA and the USSR/Russia

1 – reactor; 2 – liquid metal circuit pipeline; 3 – radiation protection; 4 – compensation tank ZhMK; 5 – refrigerator-emitter; 6 – TEG; 7 – load-bearing frame structure.

We can say that the use of radioisotope heat sources instead of chemical ones made it possible to increase the duration of satellites in orbit by tens and even hundreds of times. However, when using satellites with high energy consumption, the power of radioisotope generators is not enough. When power consumption is more than 500 W, it is more cost-effective to use a nuclear fission reaction, i.e. small nuclear power plants.

1 – block of the cesium steam supply system and control drives; 2 – TRP; 3 – ZhMK pipeline; 4 – RZ; 5 – compensation tank ZhMK; 6 – CI; 7 – frame structure.

NUCLEAR POWER INSTALLATIONS WITH THERMOELECTRIC GENERATORS

The space race, especially in the military sphere, required power supply of satellites, tens of times greater than what solar panels or isotope power sources could provide. Indeed, it is difficult to build a high-power direct heat-to-electricity converter (using thermoelements) based on a radioactive isotope. In this regard, the use of a nuclear chain reaction is much more promising. There were 55 nuclear reactors in outer space in 2000. The use of atomic-thermal energy can be divided into machine-based and machine-less. The required power is provided by compact nuclear power plants (NPPs), which, due to the limited size of satellites, must operate without large steam generators or turbines. Direct conversion of nuclear thermal energy into electrical energy has decisive advantages over mechanical conversion for autonomous reactor power plants of relatively low power (from 3 kW to 3-5 MW) and long resource capacity (from 3 years of continuous operation to 10 years in the future).

A nuclear power plant (NPP) is designed to supply electrical energy to spacecraft equipment, using the principle of direct conversion of the thermal energy of a nuclear reactor into electricity in a semiconductor thermoelectric generator. The disposal of nuclear power plants after the end of operation is carried out by transfer to orbit, where the lifetime of the reactor is sufficient for the decay of fission products to a safe level (at least 300 years). In the event of any accidents with a spacecraft, the nuclear power plant includes a highly effective additional radiation safety system that uses aerodynamic dispersion of the reactor to a safe level.

The use of thermoelectric and thermionic energy converters in combination with nuclear reactors made it possible to create a fundamentally new type of installation in which the source of thermal energy - a nuclear reactor and the converter of thermal energy into electrical energy - were combined into a single unit - the reactor-converter.

A typical nuclear power plant contains: a fast neutron reactor with a side beryllium reflector including 6 cylindrical control rods, a refrigerator emitter; 2 coolant circuits (sodium - potassium eutectic), electromagnetic pump, thermoelectric generator and control rod drives; shadow radiation protection of lithium hydride, which ensures attenuation of ionizing radiation from the reactor to a level acceptable for instruments and equipment of the spacecraft; - emitter for releasing heat into space from the second coolant circuit; attachment with units of the system for ejecting the assembly of reactor fuel elements from the reactor vessel. Electrical power - 3 kW, thermal power - 100 kW, nuclear power plant mass - 930 kg, uranium loading 235 - 30 kg.

In the 50s, work began in the USSR to create a reactor thermoelectric power plant “BUK” with a small-sized fast neutron reactor and a thermoelectric generator based on semiconductor elements located outside the reactor. More than 30 BUK installations were operated on spacecraft of the Cosmos series for a number of years.

In 1964 at the Institute of Nuclear Energy named after. I.V. Kurchatov launched the first reactor for direct conversion of heat into electricity, “Romashka”. The basis is a high-temperature fast neutron reactor, the active zone of which consists of uranium dicarbide and graphite. The reactor core (cylinder) is surrounded by a beryllium reflector. The temperature in the center of the active zone is 1770°C, on the outer surface of the reactor – 1000°C. On the outer surface of the reflector there is a thermoelectric converter consisting of a large number of silicon-germanium semiconductor wafers, the inner sides of which are heated by the heat generated by the reactor, and the outer sides are cooled. Unused heat from the converter is radiated into the surrounding space by a finned radiator refrigerator. The thermal power of the reactor is 40 kW. The electrical power removed from the thermoelectric converter is 500 W.

A high-temperature nuclear reactor-converter allows you to directly generate electricity without the participation of any moving working fluids or mechanisms. “Romashka” most fully embodies the ideas of a direct conversion reactor: there is nothing moving there. Unlike the American SNAP-10A reactor, there is no coolant or pumps. The Americans were forced to abandon their version of the reactor due to their fragile position in the field of high-temperature materials science.

The Romashka converter reactor successfully operated for 15,000 hours (instead of the expected 1,000 hours), and generated 6,100 kWh of electricity. The completed set of works with the Romashka installation showed its absolute reliability and
safety.

The operating efficiency of such generators can be increased by using, instead of a thermoelectric energy converter, flat modular thermionic elements located at the boundary of the core and radial reflector.

On the basis of the "Romashka" installation, the "Gamma" pilot plant was created - a prototype of an autonomous transportable nuclear power plant "Elena" with an electrical power of up to 500 kW, intended for power supply to remote areas.

Our country's first space nuclear power station (KNPP) "BES-5" with a homogeneous fast neutron reactor and a thermoelectric generator (TEG) was developed to power the equipment of the radar reconnaissance spacecraft at the launch site and during the entire period of the active existence of the satellite in a circular orbit altitude of about 260 km. The generating output power of "BES-5" is 2800 W, with a resource of 1080 hours. On October 3, 1970, the BES-5 nuclear power plant was launched as part of the radar reconnaissance spacecraft (Cosmos-367). After 9 launches of the BES-5 nuclear power plant, it was adopted by the USSR Navy in 1975. In total, by the time the BES-5 nuclear power plant was decommissioned (1989), 31 installations had been launched into space.

During the operation of the installation, work was carried out to refine and modernize the BES, associated with increasing radiation safety, increasing the electrical power at the end of the life to 3 kW and increasing the life to 6-12 months. The first launch of the modernized version of the nuclear power plant was carried out on March 14, 1988 as part of the Cosmos-1932 spacecraft.

Table.2 Radionuclide thermoelectric generators (RTG) and heating units (HU) based on polonium-210 and plutonium-238, gamma radiation source (IR) based on thulium-170

A typical representative of KNPP, used as power sources for powerful radio satellites (space radar stations and television broadcasters), with direct conversion of heat into electricity, is the Buk installation, which, in fact, was a TEG - a semiconductor Ioffe converter, only instead of a kerosene lamp it used a nuclear reactor. As usual, one semiconductor junction was placed in the cold, and the other in the heat: an electric current ran between them. There's nothing wrong with the cold in space - it's everywhere. For heat, the metal coolant that washed the portable nuclear reactor was suitable. It was a fast reactor with a power of up to 100 kW. The full load of highly enriched uranium was about 30 kg. Heat from the core was transferred by liquid metal - a eutectic alloy of sodium and potassium - to semiconductor batteries. Electric power reached 5 kW. Buk operating time is 1-3 months. now in quality, continued until the start of perestroika. From 1970 to 1988, about 30 radar satellites with Buk nuclear power plants with semiconductor converter reactors were launched into space. If the installation failed, the satellite was transferred to a long-term orbit at an altitude of 1000 km.

The main achievements of domestic science and technology in the field of thermoelectric technology for space missions are associated with R&D for the creation of the Romashka nuclear power plant, the BUK nuclear power plant and the real experience of its operation in space in the period 1970-1988. during 32 launches.

NUCLEAR POWER INSTALLATIONS WITH THERMAL EMISSION CONVERTERS

In the USSR, in parallel with the work on creating nuclear power plants with thermoelectric generators, work was carried out on nuclear power plants with thermionic converters that have higher technical characteristics. Essentially, the principle used here is the same as in a semiconductor converter, but instead of a cold and hot junction, a hot carbiduran cathode and a cold steel anode are used, and between them there are easily ionized cesium vapors. The effect is an electrical potential difference, that is, a natural cosmic power plant. Thermionic conversion, compared to thermoelectric conversion, makes it possible to increase efficiency, increase service life and improve the weight and size characteristics of the power plant and the spacecraft as a whole. The principle of thermionic conversion of thermal energy into electrical energy is that a metal surface, heated by the heat generated in the reactor, effectively emits ions that are adsorbed by a cooled wall located with a small gap.

In 1970-71, the thermionic nuclear power plant “Topaz” (Thermionic Experimental Converter in the Core) was created in the USSR, which used a thermal reactor with a power of up to 150 kW. The full uranium load was 31.1 kg of 90% uranium-235. Installation weight 1250 kg. The basis of the reactor were fuel elements - “garlands”. They consisted of a chain of thermoelements: the cathode was a “thimble” made of tungsten or molybdenum, filled with uranium oxide, the anode was a thin-walled niobium tube cooled by liquid sodium-potassium. The cathode temperature reached 1650oC. Electric power 10 kW. "Topazes" had a thermoelectric conversion efficiency of 5-10% versus 2-4% for previous reactors.

In addition to uranium-235, plutonium dioxide-238 is promising as a fuel for space reactors, due to its very high specific energy release. In this case, the relatively low efficiency of the direct conversion thermionic reactor is compensated by the active energy release of plutonium-238.

Two thermionic reactor-converters on intermediate neutrons (without a moderator) were tested - “Topaz-1” and “Topaz-2” with an electrical power of 5 and 10 kW, respectively. In the Topaz installation, direct (machine-free) energy conversion is carried out in power-generating channels built into the core of a small-sized thermal reactor. The Topaz-1 installation is equipped with a thermal reactor-converter and a liquid metal coolant (sodium-potassium or lithium). The principle of direct conversion of thermal energy into electrical energy consists in heating the cathode in a vacuum to a high temperature while maintaining the anode relatively cold, while electrons “evaporate” (emit) from the surface of the cathode, which, having flown through the interelectrode gap, “condense” on the anode, and when closed The external circuit carries an electric current through it. The main advantage of such an installation compared to electric machine generators is the absence of moving parts. The implementation of the concept of a lithium-cooled fast neutron reactor-converter in the future may make it possible to solve the problem of creating an installation with an electrical power of 500-1000 kW or more.

The nuclear power plant contains: a thermionic converter reactor with a zirconium hydride moderator and a side beryllium reflector, including rotary controls; reactor-converter system: drives of controls for the supply of cesium to power-generating channels, arranged in a unit located in front of the reactor-converter; shadow radiation protection made of lithium hydride, which ensures attenuation of reactor radiation to levels acceptable for spacecraft instruments; a system for removing unused heat from the reactor with a coolant (sodium-potassium eutectic), including an electromagnetic pump powered by electricity from the converter reactor, a radiator for discharging heat into outer space and other units. Electrical power - 5 kW, thermal power - 150 kW, service life, including operation for up to 1 year at 100 kW mode - 7 years, uranium loading 235 - 11.5 kg, weight - 980 kg.

Table 3 Brief characteristics of the Topaz 1 nuclear power plant

The nuclear fuel in Topaz-1 (uranium dioxide enriched with uranium-235) is enclosed in a core of refractory material that serves as a cathode (emitter) for electrons. The heat released as a result of the fission of uranium in the reactor heats the emitter to 1500-1800 degrees Celsius, resulting in the emission of electrons. When electrons hit the anode (collector), they have sufficient energy to perform work on an external load in an external closed circuit between the electrodes of the thermionic converter (emitter and collector). The interelectrode gap is several tenths of a millimeter. Cesium vapor introduced into the interelectrode gap (IEG) significantly activates the process of generating electricity in the reactor. The design of the power plant included a consumable cesium system, in which cesium vapor was pumped through the MEZ to remove impurities. Cesium vapors that passed through the MEZ were absorbed by a trap based on pyrographite, and gaseous impurities were removed into outer space. The cesium system had a thermostat-generator of cesium vapor with electric heaters, with the help of which the set temperature of the coldest zone of the thermostat was maintained. The cesium vapor generator used a number of devices that ensured the retention of the liquid phase in a certain position and prevented it from entering the vapor path under the influence of small overloads in space flight. In the applied design of the cesium vapor generator, the maximum amount of cesium was 2.5 kg, which, at a given vapor flow rate, determined by the conductivity of the choke at the outlet of the RP, clearly limited the possible resource of the nuclear power plant. The requirement to minimize mass and dimensions had to be implemented taking into account the fact that heat removal in outer space is possible only through radiation through the use of a special design of a refrigerator-emitter. The implementation of a heat removal system is significantly difficult, since it uses aggressive liquid metal sodium-potassium eutectic. Added to this are high requirements for the reliability of autonomous operation and resource capacity of nuclear power plants under conditions of overloads during launch into orbit, arbitrary orientation and the absence of gravity forces when operating in orbit, the need to ensure nuclear and radiation safety in the conditions of possible launch vehicle accidents when launching spacecraft from nuclear power plants into orbit, as well as ensuring meteor safety in space flight, etc. The Topaz nuclear power plant is designed to supply electrical energy to the equipment of spacecraft for military use. The use of nuclear reactors on satellites makes it possible to provide a stable power supply regardless of their location in orbit.
Nuclear and radiation safety is ensured by the design of a nuclear reactor. In case of any accidents, including hypothetical ones with the launch vehicle at the launch site and at the orbital launch site, the nuclear reactor remains subcritical. Due to the introduction of blockages, the launch of the reactor is impossible after reaching orbit. The blocking is removed by radio command from the Earth only after confirmation of the launch into the calculated orbit by direct trajectory measurements. The orbital altitude was chosen from the condition that the existence of the spacecraft after the termination of the functional installation, taking into account any emergency situations with the installation, would be sufficient for the decay of fission products to a safe level. This time exceeds 350 years. This ensures guaranteed safety of the world's population when using installations of this type.

The nuclear power plant "Topaz-1" was developed for radar reconnaissance satellites, "Topaz-2" - for spacecraft for direct television broadcasting from space. The first flight model - the Cosmos-1818 satellite with the Topaz installation - entered a radiation-safe stationary circular orbit at an altitude of 800 km on February 2, 1987 and worked flawlessly for six months, until cesium reserves were exhausted. The second satellite, Cosmos-1876, was launched a year later. He worked in orbit almost twice as long. The success of Topazes stimulated the development of a number of reactor projects with thermionic converters, in particular a nuclear power plant with an electrical power of up to 500 kW based on a lithium-cooled reactor.

Based on the BES and Topaz nuclear power plants, a number of plant designs with improved characteristics have been prepared. Technical proposals have been prepared for the Zarya-1 thermoelectric nuclear power plant for the optical-electronic reconnaissance spacecraft. The Zarya-1 nuclear power plant differs from the BES in the level of electrical power (5.8 kW versus 2.9 kW) and increased service life (4320 hours versus 1100 hours). In 1978, the Zarya-2 nuclear power plant with an electrical power of 24 kW and a service life of 10,000 hours was created, and then the space nuclear power plant Zarya-3 with an electrical power of 24.4 kW and a service life of 1.15 years was created. It was intended to create thrust impulses for satellite orbit correction and power supply for special equipment.

The thermionic space nuclear installation "TOPAZ 100/40" is a dual-mode nuclear power plant (NPP). It is designed to supply electrical power to electric propulsion engines (EP) when launching satellites of the Space Star satellite communication system into high (up to geostationary) orbits and to supply electrical power to on-board equipment. The power plant reactor reaches power only when the spacecraft reaches a radiation-safe orbit (800 km and above). The design of the nuclear power plant satisfies the document “Principles Relating to the Use of Nuclear Sources in Outer Space” adopted at the 47th session of the General Assembly of the United Nations. In the launch position, the nuclear power plant is located in a spacecraft compartment with a diameter of 3.9 meters and a length of 4.0 meters under the fairing. In the orbital position, the nuclear power plant is extended (the reactor is as far away from the equipment as possible) and has a length of 16.0 meters and a diameter of 4 meters.

A nuclear power plant contains: a thermionic converter reactor with servicing systems: drive of control elements, supply of working fluid (cesium) to power-generating channels; shadow radiation shielding made of lithium hydride, which ensures attenuation of reactor radiation to a level acceptable for spacecraft instruments; a system for removing unused heat from a reactor with a liquid metal (eutectic alloy of sodium and potassium) coolant, including an electromagnetic pump, a radiator refrigerator consisting of 9 panels on heat pipes for discharging heat into outer space and other units. Electrical power - 40 kW, electrical power in electric propulsion power mode - 100 kW, service life, including operation up to 1 year in 100 kW mode - 7 years, nuclear power plant mass - 4400 kg, uranium loading 235 - 45 kg To avoid the rapid fall of nuclear power plants to Earth satellites upon completion of active life, they are transferred to a burial orbit at an altitude of about 1000 km, where the spent reactor should last from 300 to 600 years. Emergency satellites are also transferred to a similar orbit. However, it was not always possible to do this. Over almost 20 years of launches, there have been four cases of a satellite falling to Earth: two in the ocean and one on land.

Historical leadership in space nuclear accidents belongs to the United States - in 1964, an American navigation satellite with a nuclear reactor on board failed to enter orbit, and this reactor fell apart in the atmosphere along with the satellite into pieces.

In the USSR, the first accident was associated with the 4300-kilogram US-A series satellite launched on September 18, 1977 (alias “Cosmos-954”, orbital parameters: perigee 259 km, apogee 277 km, inclination 65 degrees). The satellite was part of the MCRC Legend satellite system for maritime space reconnaissance and target designation, designed to detect ships of a potential enemy and provide data for the use of cruise missiles by our fleet. At the end of October 1977, Kosmos-954 stopped regular orbital corrections, but it was not possible to transfer it to a burial orbit. According to subsequent TASS reports, on January 6, 1978, the satellite suddenly depressurized, causing the onboard systems to fail. The uncontrolled descent of the vehicle under the influence of the upper atmosphere ended on January 24, 1978 with the deorbit and fall of radioactive debris in the north of Canada in the vicinity of Great Slave Lake. The satellite's uranium elements burned completely in the atmosphere. Only the remains of a beryllium reflector and semiconductor batteries were found on the ground. However, radioactive space debris ended up scattered in northwestern Canada over an area of ​​several thousand square kilometers. The USSR agreed to pay Canada $3 million, which was 50% of the cost of Operation Morning Light to clean up the area where Cosmos 954 fell.

On December 28, 1982, Cosmos-1402, which had been operating since August 30, could not be transferred to the burial orbit and it began an uncontrolled descent. Structural improvements after the previous accident made it possible to separate the core from the heat-resistant reactor vessel and prevent a compact fall of debris. The core entered the atmosphere on February 7, 1983 and radioactive fission products dispersed over the South Atlantic.

In April 1988, communication with Kosmos-1900, launched into orbit in December 1987, was lost. For five months, the satellite was descending uncontrollably, and ground services could not give the command either to move the reactor into a high orbit or to separate the core for more its safe deorbit. Fortunately, five days before the expected entry into the atmosphere, on September 30, 1988, the automatic reactor retraction system was activated, which was turned on due to the exhaustion of the fuel supply in the satellite’s orientation system.

A continuation of the Topaz type power sources was the Yenisei-Topaz thermionic nuclear power plant. The power generating channel is single-element, electrical power is 5 kW, resource is up to 3 years.

Although the accident itself did not cause material damage, its overlap with the earlier Challenger and Chernobyl disasters led to protests against the use of nuclear power in space. This circumstance became an additional factor that influenced the cessation of flights of satellites with space locators in 1988. However, the main reason for the abandonment of space locators with nuclear power was not the calls of the world community, and even more so, not the interference created by reactors for gamma-ray astronomy, but low operational characteristics.

PROSPECTS FOR THE DEVELOPMENT OF NUCLEAR POWER INSTALLATIONS

Table 4 Main characteristics of the nuclear power plant “BUK” and “BUK-TEM”

The full load of highly enriched uranium in the Buk is 30 kg, the coolant is liquid metal - a eutectic alloy of sodium and potassium. The source of electricity is a semiconductor converter. Electric power 5 kW. Topaz used a 150 kW thermal reactor. Full load of uranium 12 kg. The basis of the reactor were fuel-releasing elements - “garlands”, which were a chain of thermoelements: the cathode was a “thimble” of tungsten or molybdenum, filled with uranium oxide, the anode was a thin-walled tube of niobium, cooled by liquid sodium-potassium. Cathode temperature 1650oC, electrical power of the installation 10 kW.

From 1970 to 1988, the USSR (Russia) launched about 30 radar satellites into space with Buk nuclear power plants with semiconductor converter reactors and two with Topaz thermionic power plants.

Currently, the following requirements are imposed on space nuclear power plants (SNPPs) of the new generation: integration of a nuclear power plant in a spacecraft launched by modern launch vehicles (such as Proton, Proton-M, Angara); nuclear and radiation safety, incl. in case of a possible accident (a “clean” reactor falls to Earth); transport energy mode – at altitudes above the radiation-safe orbit of 800 km; subcritical state of the reactor in all types of accidents; negative temperature coefficient of reactivity at operating parameters; redundancy of nodes subject to resource degradation; combination of different energy conversion systems; preferential testing of elements and assemblies in out-of-reactor conditions; the possibility of a long stay in space before the start of operation of the nuclear power plant; output electrical power 50÷400 kWEL (at 115÷120 V), service life 7-10 (up to 20) years.

In the field of thermoelectric devices, a project has now been prepared in Russia for the transition from a nuclear power plant of the Buk type to a more advanced BUK-TEM (Table 4).

The experience of work carried out in the field of thermoelectricity for nuclear power plants allows us to draw a conclusion about the practical possibility of creating TEGs based on Si-Ge TB/TM of radial-ring geometry as part of either purely thermoelectric nuclear power plants or combined nuclear power plants (thermoemission + thermoelectricity) with an output electric power of the heat and power generator of 10 -100 kWEL for 21st century space missions.

The main directions of work in thermal emission after the completion of work on the programs for the creation of the TOPAZ nuclear power plant and the Yenisei nuclear power plant are associated with the need for a radical increase in efficiency. from a level of ~10% to 20-30%, the service life of electricity generating channels (EGC) and systems within nuclear power plants - from 1-2 years to 10-20 years with a significant limitation of weight and size characteristics. The choice of the thermionic EGC and nuclear power plant concept is determined by the requirements of the problem being solved, of which the most important are resource, energy intensity, including single- or dual-mode (with boosting electrical power), the magnitude of the output voltage of the electric current, the need for out-of-reactor confirmation of service life and testing of basic technical solutions on stands with simulated electric heating, etc.

Table 5 Main characteristics of TOPAZ and ELBRUS-400/200 nuclear power plants

Today it is clear that thermionic emission and thermoelectricity, both in thermionic and thermoelectric installations, and when combining them (thermoelectricity + thermal emission) in a new generation of nuclear power plants, have an undoubted prospect of use. At the same time, thermal emission has undoubted advantages over other static converters and known dynamic converters. Such installations can be effectively used to solve various problems in space missions of the 21st century.

Nuclear power plant - a power plant operating on the energy of a chain reaction of nuclear fission. The nuclear power plant, which is basically a modification of the steam turbine, began to be used on ships in the late 50s. XX century The power plant of a nuclear-powered ship includes a reactor, a steam generator and a turbine unit that drives the ship's propulsion system. A reactor is a facility for producing nuclear chain reactions, during which energy is generated that is further converted into mechanical energy. In a nuclear reactor, conditions are created such that the number of nuclear fission per unit time is a constant value, i.e. the chain reaction occurs constantly.

Design and principle of operation of a nuclear reactor.

1 - steel body; 2 - moderator; 3 - reflector; 4 - protection; 5 - fuel elements; 6 - coolant inlet; 7 - coolant outlet; 8 - control rods.

Nuclear fuel contains fissile material, usually uranium or plutonium. When atomic nuclei split into so-called fragments, or free high-energy neutrons, a lot of energy is released. To reduce the high energy of neutrons, a moderator is used: graphite, beryllium or water. In order to minimize the possibility of neutron loss, a reflector is installed. It consists mainly of beryllium or graphite. To avoid too strong a neutron flux in the reactor, control rods made of neutron-absorbing materials (cadmium, boron, indium) are installed at an appropriate depth. Energy exchange in the reactor occurs with the help of coolants, water, organic liquids, alloys of low-melting metals, etc. Currently, reactors cooled by water under pressure are usually used on ships.

Diagram of a nuclear power plant with a reactor cooled by pressurized water.

1 - reactor; 2 - primary biological protection; 3 - secondary biological protection; 4 - steam generator; 5 - heating coil of the primary circuit; 6 - primary circuit circulation pump; 7 - high pressure turbine; 8 - low pressure turbine; 9 - gearbox; 10 - capacitor; 11 - secondary circuit pump; 12 - sea water inlet; 13 - sea water outlet.

This installation has two circulation circuits. The first circuit is the circulation of water under high pressure. The primary circuit water also serves as a coolant for the nuclear reactor and has a pressure of approximately 5.8 to 9.8 MPa. It flows through the reactor and is heated, for example on the ships Otto Hahn (Germany) and Mutsu (Japan), to 278 ° C. In this case, water pressure counteracts evaporation. Hot water from the primary circuit, flowing through the heating coil, gives up its heat to the steam generator, then it returns to the reactor again. Condensate is supplied to the steam generator from the second low-pressure circuit. The water heated in the steam generator evaporates. This steam with relatively low pressure (for example, on the American ship Savannah it is 3.14 MPa) serves to power turbines, which drive the propeller through a gearbox.

The nuclear reactor is isolated from the environment by a protective shield that does not allow harmful radioactive rays to pass through. Usually double screens are used. The first (primary) screen surrounds the reactor and is made of polyethylene-coated lead plates and concrete. The secondary screen surrounds the steam generator and encloses the entire primary high-pressure circuit. This screen is mainly made of concrete with a thickness of 500 mm (Otto Hahn) to 1095 mm (Mutsu), as well as lead plates with a thickness of 200 mm and polyethylene with a thickness of 100 mm. Both screens require a lot of space and are very heavy. For example, the primary screen on the Savannah ship weighs 665 tons, and the secondary one weighs 2400 tons. The presence of such screens is a big disadvantage of nuclear power plants. Another, even more significant drawback is, despite all protective measures, the danger of environmental contamination both during the normal operation of the power plant due to waste of used fuel, release of bilge water from the reactor compartment, etc., and during accidental ship accidents and nuclear power plant.

The undeniable advantages include very low fuel consumption and an almost unlimited cruising range. For example, the ship "Otto Hahn" (Germany) did not even consume 20 kg of uranium in three years, while the fuel consumption of a conventional steam turbine power plant on a ship of this size was 40 thousand tons. The cruising range of the Japanese ship "Mutsu" is 145 thousand .miles Despite these advantages, nuclear power plants are widely used only on warships. It is especially advantageous to use them on large submarines, which can remain under water for a long time, since air is not required in the reactor to generate thermal energy. In addition, powerful icebreakers used in the northern latitudes of the globe are equipped with nuclear power plants.

1 - engine room; 2 - container with reactor; 3 - compartment of auxiliary mechanisms; 4 - spent fuel rod storage facility.

The principle of operation and design of power reactors under pressure.

Nuclear power plants (NPP). Currently, the issue of widespread use of nuclear fuel in ship power plants is becoming increasingly relevant. Interest in ships with nuclear power plants especially increased in 1973-1974, when, as a result of the global energy crisis, prices for fossil fuels sharply increased. The main advantage of ships with nuclear power plants is their virtually unlimited cruising range, which is very important for icebreakers, Arctic vessels, research vessels, hydrographic vessels, etc.

The daily consumption of nuclear fuel does not exceed several tens of grams, and the fuel elements in the reactor can be changed once every two to four years. Nuclear power plants on transport ships, especially those that make long-distance voyages at high speed, can significantly increase the ship's carrying capacity due to the almost complete absence of fuel reserves (this gives a greater gain than losses due to the significant mass of the nuclear power plant). In addition, the nuclear power plant can operate without air access, which is very important for underwater vessels. However, the fuel consumed by nuclear power plants is still very expensive. In addition, on ships with nuclear power plants it is necessary to provide special biological protection from radioactive radiation, which makes the installation heavier. It must be assumed that progress in the development of nuclear technology and in the creation of new designs and materials will make it possible to gradually eliminate these shortcomings of ship nuclear power plants.

All modern ship nuclear power plants use the heat released during the fission of nuclear fuel to generate steam or heat gases, which then enter a steam or gas turbine. The main link of the nuclear steam generating plant APPU reactor, in which a nuclear reaction occurs. Various fissile substances are used as nuclear fuel, in which the process of nuclear fission is accompanied by the release of a large amount of energy. These substances include isotopes of uranium, plutonium and thorium.

Rice. 6.1. Nuclear reactor diagram.

1- active zone; 2 -- uranium rods; 3 - moderator; 4 - reflector; 5 - coolant; 6 - biological protection; 7 - heat shield; 8 - regulation system

The most important elements of ship reactors are (Figure 6.2) active zone, in which uranium rods and a moderator are located, necessary to absorb the energy of neutron particles released during the decay of nuclei; neutron reflector, returning part of the neutrons emitted outside the core to the core; coolant to remove heat released during the fission of uranium from the core and transfer this heat to another working fluid in a heat exchanger; biological protection screen, preventing the spread of harmful radiation from the reactor; control and protection system, regulating the course of the reaction in the reactor and stopping it in the event of an emergency increase in power.

The moderator in nuclear reactors is graphite, heavy and ordinary water, and the coolant is liquid metals with a low melting point (sodium, potassium, bismuth), gases (helium, nitrogen, carbon dioxide, air) or water.

Reactors in which both the moderator and coolant are distilled water have become widespread in ship nuclear power plants, hence their name. pressurized water reactors. These reactors are simpler in design, more compact, more reliable in operation than other types, and cheaper. Depending on the method of transferring thermal energy from the reactor to the actuator (turbine), single-circuit, double-circuit and three-circuit nuclear power plant schemes are distinguished.

By single-circuit diagram(Fig. 6.2, A) the working substance - steam - is formed in the reactor, from where it enters directly into the turbine and from it through the condenser with the help of a circulation pump returns to the reactor.

By double-circuit circuit(Fig. 6.2, b) The coolant circulating in the reactor gives up its heat in a heat exchanger - a steam generator - to water, which forms steam, which enters the turbine. In this case, the coolant is passed through the reactor and steam generator by a circulation pump or blower, and the condensate formed in the turbine condenser is pumped by a condensate pump through the heating, filtration and make-up system and again supplied to the steam generator by the feed pump.

Three-circuit scheme(Fig. 6.2, V) is a double-circuit circuit with an additional intermediate circuit connected between the first and second circuits.

The single-circuit design requires biological protection around the entire circuit, including the turbine, which complicates maintenance and control and increases the danger for the crew. The double-circuit circuit is safer, since here the second circuit is no longer dangerous for I crew. Therefore, dual-circuit circuits are almost always used on nuclear ships. Three-loop circuits are used if the coolant in the reactor is highly activated and it must be carefully separated from the working substance, which is what the intermediate loop is designed for.

Rice. 6.2. Thermal diagrams of nuclear power plants:

A- single-circuit; b- double-circuit; V- three-circuit.

1 -reactor; 2 - turbine; 3 - capacitor; 4 - circulation pump; 5 - steam generator; 6 - condensate pump; 7 - filtration and recharge heating system; 8 - feed pump; 9 - heat exchanger; 10 - biological protection

Operating principle and design of power reactors. On ships with nuclear power plants, the main source of energy is a nuclear reactor. The heat released during the fission of nuclear fuel serves to generate steam, which then enters the steam turbine.

The reactor plant, like a conventional steam boiler, contains pumps, heat exchangers and other auxiliary equipment. A special feature of a nuclear reactor is its radioactive radiation, which requires special protection for operating personnel.

Safety. Massive biological protection has to be installed around the reactor. Common radiation shielding materials are concrete, lead, water, plastics and steel.

There is a problem of storing liquid and gaseous radioactive waste. Liquid waste is stored in special containers, and gaseous waste is absorbed by activated charcoal. The waste is then transported ashore to recycling facilities.

Ship nuclear reactors. The main elements of a nuclear reactor are rods with fissile material (fuel rods), control rods, coolant (coolant), moderator and reflector. These elements are enclosed in a sealed housing and arranged to ensure a controlled nuclear reaction and removal of the generated heat.

The fuel can be uranium-235, plutonium, or a mixture of both; these elements can be chemically bonded with other elements and be in the liquid or solid phase. Heavy or light water, liquid metals, organic compounds or gases are used to cool the reactor. The coolant can be used to transfer heat to another working fluid and produce steam, or it can be used directly to rotate the turbine. The moderator serves to reduce the speed of the neutrons produced to a value that is most effective for the fission reaction. The reflector returns neutrons to the core. The moderator and reflector are usually heavy and light water, liquid metals, graphite and beryllium.

All naval vessels, the first nuclear-powered icebreaker "Lenin", the first cargo-passenger ship "Savannah" have power plants made according to a dual-circuit design. In the primary circuit of such a reactor, water is under pressure up to 13 MPa and therefore does not boil at a temperature of 270 0 C, usual for the reactor cooling path. Water heated in the primary circuit serves as a coolant for producing steam in the secondary circuit.

Liquid metals can also be used in the primary circuit. This scheme was used on the US Navy submarine Sea Wolf, where the coolant is a mixture of liquid sodium and liquid potassium. The pressure in the system of such a scheme is relatively low.

The same advantage can be realized by using paraffin-like organic substances - biphenyls and triphenyls - as a coolant. In the first case, the disadvantage is the problem of corrosion, and in the second, the formation of resinous deposits.

There are single-circuit schemes in which the working fluid, heated in the reactor, circulates between it and the main engine. Gas-cooled reactors operate using a single-circuit design. The working fluid is a gas, for example helium, which is heated in a reactor and then rotates a gas turbine.

Protection. Its main function is to protect the crew and equipment from radiation emitted by the reactor and other elements that come into contact with radioactive substances. This radiation is divided into two categories: neutrons, released during nuclear fission, and gamma radiation, produced in the core and in activated materials.

In general, ships have two containment shells. The first is located directly around the reactor vessel. Secondary (biological) protection covers steam generating equipment, cleaning systems and waste containers. The primary shield absorbs most of the reactor's neutrons and gamma radiation. This reduces the radioactivity of reactor auxiliary equipment.

Primary protection can be a double-shell sealed tank with a space between the shells filled with water and an outer lead shield 2 to 10 cm thick. Water absorbs most of the neutrons, and gamma radiation is partially absorbed by the walls of the housing, water and lead.

The main function of the secondary protection is to reduce the radiation of the radioactive nitrogen isotope 16N, which is formed in the coolant passing through the reactor. For secondary protection, water containers, concrete, lead and polyethylene are used.

Efficiency of ships with nuclear power plants. For warships, the cost of construction and operating costs are less important than the advantages of an almost unlimited cruising range, greater power and speed of ships, compact installation and reduction of maintenance personnel. These advantages of nuclear power plants have led to their widespread use on submarines. The use of atomic energy on icebreakers is also justified.

Self-test questions:

What is the source of energy for nuclear power plants?

What is a double shell sealed tank?