The structure of a nuclear reactor of a submarine. Reactors of nuclear power plants for nuclear submarines. Boats serving in the US Navy

At the dawn of underwater shipbuilding, when the search for optimal engines for submarines was underway, designers experimented, among other things, with steam power plants.

After diesel-electric submarines had already crossed the 20-knot mark in the 1930s, it seemed that the era of “steam” submarines was over forever. But only a decade and a half passed, and they were remembered again. The only difference was that the steam for the turbine should be produced not by a conventional boiler burning organic fuel, but by a nuclear boiler.

PHYSICAL OPERATING PRINCIPLES

The operation of a nuclear power plant is based on a controlled nuclear chain reaction. This reaction is a self-sustaining process of fission of nuclei of uranium isotopes (or fissile isotopes of other elements) under the influence of elementary particles - neutrons, which, due to the absence of an electric charge, easily penetrate into atomic nuclei. When nuclei fission, new, lighter nuclei are formed - fission fragments, neutrons are emitted and a large amount of energy is released. Thus, the fission of each uranium-235 nucleus is accompanied by the release of approximately 200 megaelectronvolts of energy. Of this, approximately 83% comes from the kinetic energy of fission fragments, which, as a result of fragment deceleration, is converted mainly into thermal energy. The remaining 17% of nuclear energy is released in the form of energy from free neutrons and various types of radioactive radiation. The newly formed neutrons, in turn, participate in the fission of other nuclei.

FIRST STEPS

The development of nuclear power plants for submarines began in the United States in 1944, and four years later the first of them was designed. There, in June 1952, the laying of the first nuclear submarine, named Nautilus, took place. At first glance, she was the very embodiment of the human dream of a true submarine. Indeed, where, if not in dreams, could one imagine an underwater ship almost 100 m long capable of traveling at a speed of more than 20 knots for more than a month without surfacing? But, as often happens, a significant qualitative leap in one area of ​​technological progress entailed a whole bunch of related problems in related ones. In relation to nuclear power plants, these are primarily issues related to the nuclear safety of their operation and subsequent disposal. But in the early 1950s, no one simply thought about it.

GENERAL DESIGN

The main element of nuclear power plants is a nuclear reactor - a special device in which a controlled nuclear chain reaction occurs. It consists of a core, a neutron reflector, control and protection rods, and biological protection of the reactor. The reactor core contains nuclear fuel and a neutron moderator. A controlled chain fission reaction of nuclear fuel takes place in it. Nuclear fuel is placed inside so-called fuel elements (fuel elements), which have the form of cylinders, rods, plates or tubular structures. These elements form a lattice, the free space of which is filled with a moderator. The main materials for shells of fuel elements are aluminum and zirconium. Stainless steel is used in limited quantities and only in reactors using enriched uranium, as it strongly absorbs thermal neutrons. To remove heat, a coolant liquid is pumped through the core.

In water-cooled power reactors, both the moderator and the coolant of the systems are bidistillate (double-distilled water).

To make a chain reaction possible, the dimensions of the reactor core must be no less than the so-called critical dimensions at which the effective multiplication factor is equal to unity. The critical dimensions of the core depend on the isotopic composition of the fissile material (they decrease with increasing enrichment of nuclear fuel with uranium-235), on the amount of materials that absorb neutrons, the type and amount of moderator, the shape of the core, etc. In practice, the dimensions of the core are assigned larger than the critical ones so that the reactor has the reactivity reserve necessary for normal operation, which is constantly decreasing and by the end of the reactor’s campaign it becomes equal to zero. A neutron reflector surrounding the core should reduce neutron leakage. It reduces the critical dimensions of the core, increases the uniformity of the neutron flux, increases the specific power of the reactor, therefore, reduces the size of the reactor and ensures savings in fissile materials. Typically the reflector is made of graphite, heavy water or beryllium. Control and protection rods contain materials that intensively absorb neutrons (for example, boron, cadmium, hafnium). Control and protection rods include compensating, regulating and emergency rods.

MAIN VARIETIES

The Nautilus had a power plant with a pressurized water-cooled reactor. Such reactors are also used on the vast majority of other nuclear submarines.

In modern nuclear plants, nuclear energy is converted into mechanical energy only through thermal cycles. In all mechanical installations of nuclear submarines, the working fluid of the cycle is steam. A steam cycle with an intermediate coolant that transfers heat from the core to the working fluid in steam generators leads to a double-circuit thermal circuit of the power plant. This thermal design with a pressurized water reactor is most widely used on nuclear submarines. The primary circuit requires protection, since when coolant is pumped through the reactor core, the oxygen contained in the water becomes radioactive. The entire second circuit is non-radioactive.

In order to obtain steam of the specified parameters in the second circuit, the water in the primary circuit must have a sufficiently high temperature exceeding that of the steam produced. To prevent boiling of water in the primary circuit, it is necessary to maintain an appropriate excess pressure in it, ensuring the so-called “underheating to boiling”. Thus, in the first circuit of foreign ship nuclear power plants, a pressure of 140-180 atmospheres is maintained, which allows heating the circuit water to 250-280 ° C. At the same time, saturated steam is generated in the second circuit with a pressure of 15-20 atmospheres at a temperature of 200-250 ° C. On first-generation Soviet submarines, the water temperature in the primary circuit was 200 ° C, and the steam parameters were 36 atmospheres and 335 ° C.

WITH LIQUID METAL COOLANT

In 1957, the second nuclear submarine, Seawolf, entered service with the US Navy. Its fundamental difference from the Nautilus was its nuclear power plant, which used a reactor with sodium as a coolant. Theoretically, this should have reduced the specific gravity of the installation by reducing the weight of the biological protection, and most importantly, by increasing the steam parameters. The melting point of sodium, which is only 98 ° C, and the high boiling point - more than 800 ° C, as well as excellent thermal conductivity, in which sodium is second only to silver, copper, gold and aluminum, make it very attractive for use as a coolant. By heating liquid sodium in the reactor to a high temperature, at a relatively low pressure in the primary circuit - about 6 atmospheres, in the second circuit we obtained steam at a pressure of 40-48 atmospheres with a superheat temperature of 410-420 ° C.

Practice has shown that, despite all the advantages, a nuclear reactor with a liquid metal coolant has a number of significant disadvantages. To keep sodium in a molten state, including during periods of inactivity of the installation, the ship must have a special permanent system for heating the liquid metal coolant and ensuring its circulation. Otherwise, the sodium and intermediate circuit alloy will “freeze” and the power plant will be disabled. During the operation of the Seawolf, it was discovered that liquid sodium was chemically excessively aggressive, as a result of which the primary circuit pipelines and the steam generator quickly corroded, even to the point of the appearance of fistulas. And this is very dangerous, since sodium or its alloy with potassium reacts violently with water, leading to a thermal explosion. A leak of radioactive sodium from the circuit forced us to first turn off the superheating sections of the steam generator, which led to a reduction in the installation’s power to 80%, and then, a little over a year after commissioning, to remove the ship from the fleet altogether. The Seawolf experience forced American sailors to finally opt for pressurized water reactors. But in the USSR, experiments with liquid metal coolant continued much longer. Instead of sodium, an alloy of lead and bismuth was used - much less fire and explosive. In 1963, a Project 645 submarine with such a reactor came into operation (essentially a modification of the first Soviet nuclear submarines of Project 627, which used pressurized water reactors).

And in the 1970s, the fleet was replenished with seven Project 705 submarines with a nuclear power plant on a liquid metal carrier and a titanium hull. These submarines had unique characteristics - they could reach speeds of up to 41 knots and dive to a depth of 700 m. But their operation was extremely expensive, which is why the boats of this project were nicknamed “goldfish”. Subsequently, reactors with liquid metal coolant were not used either in the USSR or in other countries, and pressurized water reactors became universally accepted.

More than 15 years have passed since the last of the Project 705 boats was expelled from the Russian Navy, and disputes continue to this day among naval sailors and shipbuilders. What exactly was Project 705 - a breakthrough into the future, ahead of its time, or an expensive technical adventure?

The external contours of the boat were worked out at TsAGI, tested on numerous models in the pools of the Leningrad Central Research Institute named after. Krylova. And, in addition to technical excellence and numerous innovations important for a warship, the nuclear submarine also turned out to be unusually beautiful.

In 1959, when the first Soviet nuclear submarine Leninsky Komsomol, built according to the design of the Leningrad SKB-143 (now SPMBM Malachite), had already gone to sea, and the construction of a whole series of similar ships was underway in Severodvinsk, a leading specialist of the same SKB A.B. Petrov came up with a proposal to create a “Small high-speed fighter submarine.” The idea was very relevant: such boats were needed to hunt submarines - carriers of ballistic missiles with nuclear charges, which then began to be actively built on the stocks of a potential enemy. On June 23, 1960, the Central Committee and the Council of Ministers approved the project, which was assigned the number 705 (“Lyra”). In NATO countries this boat became known as Alfa. Academicians A.P. Alexandrov, V.A. Trapeznikov, A.G. Iosifyan became the scientific leaders of the project, and the chief designer of the ship was Mikhail Georgievich Rusanov. He was a talented man with a very difficult fate: seven years in the Gulag, and after his release, a ban on entry into Leningrad. An experienced shipbuilding engineer worked in a button-making artel in Malaya Vishera and only in 1956 was able to return to Leningrad, to SKB-143. He started as deputy chief designer of the Project 645 nuclear submarine (this experience turned out to be very useful for Rusanov).

Battle with Titan

The purpose of the new submarine determined the basic requirements - high speed and maneuverability, perfect hydroacoustics, powerful weapons. To meet the first two requirements, the boat had to have extremely small dimensions and weight, the highest hydrodynamic characteristics of the hull and a powerful power plant that fit into the limited dimensions. It was impossible to do this without non-standard solutions. Titanium was chosen as the main material for the ship's hull, as well as many of its mechanisms, pipelines and fittings - the metal is almost twice as light and at the same time stronger than steel, and is also absolutely corrosion-resistant and low-magnetic. However, it is quite capricious: it is welded only in an inert gas environment - argon, it is difficult to cut, and it has a high coefficient of friction. In addition, titanium could not be used in direct contact with parts made of other metals (steel, aluminum, brass, bronze): in sea water it forms an electrochemical couple with them, which causes destructive corrosion of parts made of other metals. It was necessary to develop special grades of high-alloy steel and bronze, and specialists from the Central Research Institute of Metallurgy and Welding (Prometheus) and the Central Research Institute of Shipbuilding Technology managed to overcome these titanium tricks. As a result, a small-sized ship hull with an underwater displacement of 3,000 tons was created (although the customer, the Navy, insisted on a limit of 2,000 tons).

It must be said that Soviet shipbuilding already had experience in creating submarines from titanium. In 1965, a Project 661 nuclear submarine with a titanium hull was built (in a single copy) in Severodvinsk. This boat, known as the “Goldfish” (a hint at its fantastic cost), remains to this day the record holder for speed under water - during sea trials it showed 44.7 knots (about 83 km/h).

All innovations

Another radical innovation was the size of the crew. On other nuclear submarines (both Soviet and American) 80-100 people serve, and in the technical specifications for the 705th project the number 16 was named, and only officers. However, during the design, the number of the future crew grew and eventually reached 30 people, including five midshipman technicians and one sailor, who was assigned the important role of cook, and part-time orderly and cleaner (it was originally assumed that the duties of the cook would be performed by the ship's doctor). In order to combine such a small crew with a huge number of mechanisms, the boat had to be very seriously automated. Later, sailors even nicknamed the boats of the 705 project “automatic machines.”

For the first time in the country (and probably in the world), global automation covered everything: control of the ship’s movement, the use of weapons, the main power plant, all general ship systems (diving, ascent, trim, retractable devices, ventilation, etc.). One of the key and very controversial issues in the development of automation systems (this was dealt with by a number of research institutes and design bureaus, including the Central Research Institute "Aurora", "Granit", "Agat") was the choice of current frequency for the ship's electrical network. Options of 50 and 400 Hz were considered, each having its own advantages and disadvantages. The final decision in favor of 400 Hz was made at a three-day meeting of the heads of several organizations involved in the topic, with the participation of three academicians. The transition to a higher frequency caused many production problems, but it made it possible to significantly reduce the size of electrical equipment and instruments.

For the first time, pneumatic-hydraulic torpedo tubes were installed on the Project 705 nuclear submarine, providing firing over the entire range of immersion depths. Six torpedo tubes and 18 torpedoes, taking into account the speed and maneuverability of the boat, made it a serious opponent for NATO submarines.

Atomic heart

And yet, the main innovation that determined the fate of the entire project was the choice of the ship’s main power plant. It became a compact nuclear fast neutron reactor (BN) with a liquid metal coolant (LMC). This saved about 300 tons of displacement due to higher steam temperatures and therefore better turbine efficiency.

The world's first submarine with a reactor of this type was the American nuclear submarine Seawolf (1957). The design turned out to be not very successful; during sea trials, the primary circuit depressurized with the release of sodium. Therefore, in 1958, the reactors were replaced with water-cooled reactors, and the US military no longer became involved with liquid metal reactors. In the USSR, they preferred to use a lead-bismuth melt, which is much less chemically aggressive than sodium, as a coolant. But the nuclear submarine K-27, built in 1963, was also unlucky: in May 1968, during a voyage, the primary circuit of one of the two reactors ruptured. The crew received huge doses of radiation, nine people died, and the boat was christened "Nagasaki" (the nickname "Hiroshima" had already been taken by K-19 in 1961). The nuclear submarine was so radioactive that it could not be repaired, and as a result, in September 1982, it was sunk off the northeastern coast of Novaya Zemlya. The naval wits added “forever underwater” to its “titles.” But even after the K-27 tragedy, the USSR decided not to give up the tempting idea of ​​using liquid metal reactors on nuclear submarines; engineers and scientists under the leadership of Academician Leipunsky continued to work on their improvement.

Two organizations took on the development of the main power plant for the 705th project. Podolsk OKB "Gidropress" created a block two-section installation BM-40/A with two circulation pumps. Gorky OKBM produced the OK-550 installation, also modular, but with a branched primary circuit and three circulation pumps. Subsequently, both installations found application on the Project 705 nuclear submarine: OK-550 was installed on boats being built in Leningrad (four ships), and BM-40/A was installed on three boats built in Severodvinsk according to a variant of Project 705K. Both installations provided power at the turbine shaft of up to 40??000 hp, which made it possible to develop the speed specified in the technical specifications of 40 knots.

Longest boat

A total of seven Project 705 nuclear submarines were built; they became the world's first production boats equipped with liquid metal reactors. The first boat, K-64, laid down in June 1968 in the same old boathouse where the famous cruiser Aurora was built 70 years earlier, was transferred to the Navy in December 1971. The main problems of trial operation were associated with the reactor, which was fundamentally different from the well-known water-water reactors. The fact is that the lead-bismuth alloy crystallizes at +145°C, and when operating a reactor with such liquid metal material, in no case should the temperature in the primary circuit be allowed to drop to this value. It was as a result of non-compliance with this condition that plugs of frozen melt began to appear in the pipelines of one and then the second loop of the primary circuit, which was no longer possible to return to a liquid state. There was a “contamination” of the steam production plant, accompanied by depressurization of the primary circuit and radioactive contamination of the boat, which at that time was moored at its base. It soon became clear that the reactor was irretrievably destroyed, and the boat could no longer go to sea. As a result, in August 1974, she was withdrawn from the fleet and, after much debate, was cut into two parts, each of which was decided to be used for crew training and development of new technologies. The bow of the boat was towed to Leningrad, and the stern with the reactor compartment remained in Severodvinsk at the Zvezdochka shipyard. The black cross of the cut-off K-64 stern stabilizer with horizontal and vertical rudders remained there as a mournful monument. Among military sailors and shipbuilders, there was a joke-riddle about “the longest boat in the world” for a long time.

Real life

Construction of the series, which was already actively underway in Leningrad and Severodvinsk, was suspended, but resumed a couple of years later, and from 1977 to 1981, six Project 705 nuclear submarines were transferred to the fleet. These ships served quite intensively and successfully as part of the Northern Fleet, causing serious concern among NATO countries. Taking into account the sad experience of K-64, all production nuclear submarines of this project were additionally equipped with an “electric boiler”, the task of which was to maintain the required temperature in the primary circuit of the reactor when it was brought to minimum power while the nuclear submarine was parked at the base. To operate the boiler, it was necessary to supply electricity from the shore. There were interruptions in this, and since the boat crews were desperately afraid of destroying the reactor, it was not maintained at the minimum power level, which accelerated the production of nuclear fuel. In addition, the displeasure of the naval base authorities was caused by the need to organize special laboratories for periodic checks, adjustments and repairs of the automation with which boats of this type were stuffed. So the coastal services of the Navy have added a lot of worries. Increasingly, conversations arose on the topic that the new ships, despite their unique combat qualities, were ahead of their time and unnecessarily difficult to maintain. The seventh serial boat was not completed, but was cut up right on the slipway. By 1990, all (except one) of the Project 705 nuclear submarines were withdrawn from the fleet, having served significantly less than the period for which they were designed.

The last "Alpha"

The K-123, which became an exception, remained in service until 1997 due to excessively delayed repairs after a serious accident in 1982. When the boat was submerged in the Barents Sea, the “Reactor Malfunction” signal suddenly came on at the control panel in the central control room of the nuclear submarine. Lieutenant Loginov went for reconnaissance into the uninhabited reactor compartment, and a minute later he reported that he was observing silvery metal spreading across the deck: it was highly active liquid metallic material escaping from the primary circuit of the reactor. At the same time, the signal “Reactor compartment contamination” turned on. Leave the compartment!”, and, as one of the crew members who survived the accident later recalled, “they thought about Loginov in the past tense.” But Loginov survived. Going out into the airlock through which the reactor compartment communicates with the rest of the boat, he left all his clothes there and went through a thorough wash. The reactor was shut down, the nuclear submarine surfaced, having purged its ballast tanks. As was established later, about 2? t LMC. The boat was so dirty that the cruiser that came to the rescue did not dare to approach it to hand over the tow rope. As a result, the cable was wound up using a deck helicopter from the same cruiser. The repair of the K-123, during which the reactor compartment was completely replaced, ended in 1992, the nuclear submarine returned to service and served safely until 1997. With its decommissioning, Project 705 ended ingloriously.

Reserve parachute

Of the six compartments of the nuclear submarine, only two were habitable, above one of which there was a pop-up rescue chamber created for the first time in the world, designed to rescue the entire crew (30 people) even from the maximum diving depth (400 m).

Ahead of its time

Project 705 nuclear submarines boasted fantastic speed and maneuverability characteristics and many innovations: a titanium hull, a fast neutron reactor with a liquid metal coolant, and fully automated control of all ship systems.

Liquid metal

Nuclear-powered ships are essentially steamships because their propellers are driven by steam turbines. But steam is not produced in ordinary boilers with fireboxes, but in nuclear reactors. The heat of radioactive decay is transferred from the nuclear fuel in the primary cooling loop to a coolant, usually pressurized water (to raise the temperature to 200 °C or more), which also serves as a neutron moderator. And the coolant already transfers heat to the water of the second circuit, evaporating it. But pressurized water has its drawbacks. High pressure means that the walls of the pipes of the cooling system of the reactor's primary circuit must be thick and strong, and when the primary circuit is depressurized, radioactive steam penetrates into the most inaccessible places. One alternative is the use of fast neutron reactors with a coolant made of low-melting metals in their liquid phase - for example, sodium or a lead-bismuth alloy. Their thermal conductivity and heat capacity are significantly higher than that of water, they can be heated to higher temperatures without high pressure in the primary circuit, which makes it possible to create very compact reactors.

Since its inception, nuclear energy in Russia has remained the prerogative of the state, especially in terms of the development of new technologies. In recent years, private investors have repeatedly made attempts to enter this market, and so far only En+ Group, which manages the assets of Oleg Deripaska, has achieved success. The parity joint venture between Rosatom and En+ will adapt nuclear submarine reactors to civilian needs. The general director of the joint venture, Anna Kudryavtseva, spoke about the details of the future project and its prospects in an interview with Interfax.

- You have been working on this project for quite a long time. When was the company registered? What will be the contributions of the parties: investments from Eurosibenergo and Rosatom’s share?

The joint venture was registered on December 10, the contributions of the parties are 50/50. We contribute not only investments, but also intellectual property.
We have the basic technology of a reactor with lead-bismuth coolant SVBR (lead-bismuth fast reactor - IF), which has been developed by industry organizations - Gidropress and the Obninsk Institute of Physics and Power Engineering. SVBR installations, only of lower power, were operated on nuclear submarines. So SVBR is a proven technology, and Russia is the only country in the world that has this workable technology.

- Is anyone abroad working on similar projects of reactors with lead-bismuth coolant?

- Some countries are at the R&D stage, others have only preliminary foundations and concepts.

- Which customers are NPPs with SVBR reactors aimed at?

Such stations are designed for the needs of regional energy, where there is a need for medium and low power generation with an increased level of safety. I mean, first of all, hard-to-reach areas where metallurgical companies or oil and gas companies mine.
In addition, the project has great export potential, primarily in Africa and Asia, where in terms of consumption volumes, thousand-ton reactors (with a capacity of 1000 MW - IF) are not needed, or they are not suitable due to network restrictions. But at the same time they need an increased level of security, such that if something happens, the installation will shut itself down. And in our country, the very principle of the reactor is aimed at ensuring maximum safety even in not very skillful hands.

- Previously, the total cost of the project was estimated at up to $1 billion. Do you confirm this amount?

- In the spring, we estimated the necessary investments at approximately 14 -16 billion rubles (for the period until 2019), but this is in pre-crisis prices. Taking into account the crisis, it is clear that this amount will be adjusted. On the one hand, we see a reduction in the cost of labor, and for some items - equipment, preparatory work. On the other hand, we understand that there is inflation.
I would like to emphasize that within the framework of the joint venture we lay down a clear principle: the use of all the classical canons of project management. That is, there will be strict control over expenses on both sides.

- Rosatom and the private investor have parity shares. How will disputes be resolved?

International arbitration.

Have you already assessed your intellectual property? When will Rosatom include it in the joint venture, and how will it be done?

Preliminary negotiations with the partner on this issue have taken place. However, questions remain regarding the procedure for valuing these assets at their real value. The fact is that now developments under the SVBR project are the property of industry enterprises. And, as a rule, their balance sheet valuation is quite low. In order for us to add this intellectual property to the joint venture at a commercial value, we will need a revaluation. But this raises questions of a legislative nature, because the revaluation will cause tax consequences for enterprises. Simply put, they have an income tax. This is a problem point not only for our project, it is typical for the country as a whole.
In this regard, the Rosatom State Corporation has created an intersectoral working group, which is still in its infancy. We expect all leading technology corporations to be included there. For example, Russian Technologies have already confirmed their participation. We also involve Rusnano, Russian Railways and Gazprom in this activity. Within the framework of the working group, proposals for improving the legislation of the Russian Federation in terms of scientific, technical and innovative activities, and, in particular, regarding the accounting of intellectual property in assets, will be worked out. In 2010, we plan to prepare a package of relevant legislative initiatives.

- And when, in this case, do you expect the laws to be amended?

Most likely, we hope, these proposals can be approved in 2011. But we won't rush.

- Can you estimate what the share of intellectual property will be in the total cost of the project?

- We have a preliminary figure, but this is confidential information.

- What priority tasks has the joint venture identified for itself for the coming years?

The first stage of our work is R&D and preparation of a civil project. We plan for this to take approximately 3.5-4 years. Managing R&D to ensure results is task number one.
The second point of our efforts is determining the location of the pilot plant. We are now choosing from three sites, all of which are industry enterprises where human and technical resources are concentrated. I wouldn’t like to name them yet. At the beginning of 2010, I think, a choice will be made in favor of one of the sites.
We will choose based on a set of criteria, including technical and geological characteristics, human resources, economics of the project, as well as energy shortages in the region. Despite the fact that the capacity of the pilot plant will be small, we consider it not only as a platform for testing technologies, but also as an economic facility.

The basis of nuclear energy now are nuclear power plants with VVER reactors, which carry the base load in the UES of Russia. That is, they cannot maneuver during the day following changes in consumption. Will stations with SVBR reactors also work in the base?

Maneuverability is one of the characteristics that we include in the project. Another advantage of SVBR is modularity. The 100 MW reactor will not be installed on site, but will be assembled at the manufacturing plant and then transported to site. This makes the project cheaper.

- Is it already clear who will be the manufacturing plant?

There are a number of enterprises, industry and non-industry, that we are considering. We are also ready to look at foreign equipment suppliers. In addition, the joint venture itself has the task of developing competencies not only in the field of engineering of nuclear power plants, but also in terms of reactor construction.
I would like to note that now, due to the crisis, machine builders have fewer orders from traditional energy, and there is no active competition for their capacity, so in this sense, we are starting at a good time.

- Will the cost of 1 kW of power at a station with an SVBR reactor be comparable to the price of a VVER reactor?

The economy never works out in a pilot plant. Then the whole question is in the configuration of the serial unit. We are currently studying this issue and assessing the market, including foreign ones. The greater the power of a nuclear power plant, the more economical the station is, and, ultimately, it might be optimal to build stations with SVBR reactors of 1000 MW at once. We can do this too. Another question is that in this power line the nuclear industry has both “fast” sodium reactors (project BN-800 - IF) and VVER. Therefore, we are unlikely to enter this niche, but rather focus on regional energy.
A preliminary assessment shows that the optimal power of a nuclear power plant with SVBR will be in the range of 200-400 MW. But in the end, everything will depend on the market, on how much the market can eat.
The economic parameters of the project will be more clearly visible when the pilot plant is operational. Although, of course, we are already doing all the basic calculations and forecasts.

- How will issues regarding radioactive waste from SVBR be resolved?

We don't have any particular problems with waste. Some risky technical points are clear and obvious, but there are no insoluble criticisms, only purely engineering issues.
In general, the industry is now creating a unified system for managing radioactive waste and spent nuclear fuel, and we will simply fit in there, we will be consumers of the services of national operators in this area. The same will happen with fuel.

- By the way, what kind of fuel does SVBR use?

For now we will use traditional fuel - enriched uranium. Next will most likely be uranium-plutonium fuel (MOX), and at the next stage - dense fuel, when it appears. The geometry of the SVBR core allows the use of any type of fuel.

- If I understand correctly, SVBR can also be a producer of nuclear materials, a so-called “breeder”?

Yes it is. Although we have no goal in itself to produce plutonium. On the contrary, from a nonproliferation point of view, it is better not to make these settings by “breeders.” In addition, there are “fast” sodium reactors that can produce everything the industry needs for the production of MOX fuel, in particular. And then, there must be a certain proportion of reactors - MOX consumers, and plutonium producers for these purposes. And this share is not one to one.

To the best of our knowledge, the possibility of using SVBR for placement at decommissioned nuclear power plant sites was previously discussed. For example, at the Novovoronezh station, where the 1st and 2nd power units have already exhausted their service life. Is this idea still relevant?

This option is being considered as an option, but we have not yet done a detailed study. However, we also understand that the market may be in demand for additional SVBR services, such as superheated steam, heat, and water desalination plants.

- The project is designed for a fairly long period of implementation, and now, during the crisis, many private investors are faced with financial difficulties. Do you accept the possibility that your partner, for some reason, may leave the project or reduce his participation in it?

- Our partner, Eurosibenergo, confirmed its interest, including at the management level, and provided certain guarantees. We have been working for a year and a half, and financing during 2009, in particular, comes from Eurosibenergo.

- How much money has already been invested?

It is impossible to name the exact amount, because it is not clear how to correctly estimate on a cost basis what was invested in the Soviet years, and in particular through the Ministry of Defense, since SVBR reactors were operated on nuclear submarines.
In general, it is impossible to make an assessment on the cost side for projects of this kind. Therefore, if we evaluate it, then only on the income principle.

- You also count on government support. What will it be expressed in?

There are two aspects to this question, like two sides of the same coin. Firstly, there is an industry-specific federal target program for new generation nuclear technologies, where a separate article stipulates the development of “fast” energy, that is, reactors with sodium, lead and lead-bismuth coolants. Financing for the SVBR is provided there, and we consider this as the state’s contribution to the state corporation’s business. And the second side - within the framework of the presidential commission on modernization, our project was approved back in July, with the note “without additional funding.” There is a format there that confirms the priority status of the project.

Nuclear submarines and other nuclear-powered ships use radioactive fuel - mainly uranium - to turn water into steam. The resulting steam rotates turbogenerators, which produce electricity to propel the ship and power various onboard equipment.

Radioactive materials like uranium release thermal energy through the process of nuclear decay, when the unstable nucleus of an atom is split into two parts. This releases a huge amount of energy. On a nuclear submarine, this process is carried out in a thick-walled reactor, which is continuously cooled with running water to avoid overheating or even melting of the walls. Nuclear fuel is particularly popular with the military on submarines and aircraft carriers due to its extraordinary efficiency. On one piece of uranium the size of a golf ball, a submarine could circle the globe seven times. However, nuclear energy poses dangers not only to the crew, who could be harmed if a radioactive release occurs on board. This energy poses a potential threat to all life in the sea, which could be poisoned by radioactive waste.

Schematic diagram of the engine compartment with a nuclear reactor

In a typical nuclear reactor engine (left), cooled water is pressurized into the reactor vessel containing nuclear fuel. The heated water leaves the reactor and is used to turn other water into steam, and then, when cooled, is returned to the reactor. Steam rotates the blades of a turbine engine. The gearbox converts the rapid rotation of the turbine shaft into a slower rotation of the electric motor shaft. The electric motor shaft is connected to the propeller shaft using a clutch mechanism. In addition to transmitting rotation to the propeller shaft, the electric motor generates electricity, which is stored in on-board batteries.

nuclear reaction

In the reactor cavity, the atomic nucleus, consisting of protons and neutrons, is struck by a free neutron (figure below). The impact splits the nucleus, and in this case, in particular, neutrons are released, which bombard other atoms. This is how a chain reaction of nuclear fission occurs. This releases a huge amount of thermal energy, that is, heat.

A nuclear submarine cruises along the coast on the surface. Such ships need to replenish fuel only once every two to three years.

The control group in the conning tower monitors the adjacent water area through a periscope. Radar, sonar, radio communications and cameras with scanning systems also assist in the navigation of this vessel.

In the second half of the 80s of the 20th century, an intensive process of decommissioning and withdrawal of nuclear submarines (NPS) from the Russian Navy began. This was due both to the expiration of service life and to the fulfillment by the Russian Federation of international obligations on arms reduction. The main results of the work on dismantling three generations of nuclear submarines are presented in the table.

At present, the period of active dismantling of nuclear submarines, when more than 10 nuclear submarines per year were dismantled annually to form one- or three-compartment blocks, has ended. 1st generation nuclear submarines are almost completely dismantled (with the exception of damaged nuclear submarines). The second generation has also been largely taken out of service and disposed of according to the accepted scheme. Over the next few years, 2–5 nuclear submarines of the 2nd and 3rd generations will be decommissioned and dismantled per year.

Currently, to solve the problems of storing reactor compartments (RC), handling radioactive waste (RAW) generated during disposal, it is necessary to create additional infrastructure, including the construction of long-term storage facilities for reactor compartments (LSR), regional centers for conditioning and storage of RW, berths walls, reconstruction of railway communications, etc. All this requires the involvement of significant financial and labor resources. The scale of the tasks being solved is illustrated in Fig. 1, which shows one of the long-term storage sites for reactor compartments of dismantled nuclear submarines.

The total cost of constructing an above-ground storage facility for 120 ROs in Sayda Guba exceeds 300 million euros.

Figure 1. Long-term storage site for reactor compartments.

It is assumed that radioactive waste in storage facilities should be stored for 75-100 years, after which the issue of their disposal must be finally resolved. Considering that the masses of nuclear submarine reactors are relatively small (about 1000 tons), and the storage tanks are located far from steelmaking plants, their final disposal (final cutting and remelting of steel) is economically doubtful.
When deciding on final dismantlement, it should also be taken into account that solid radioactive waste generated during the dismantling of nuclear submarines is loaded into the reactor facility.

A significant part of nuclear power plants (NPPs) of decommissioned nuclear submarines of the 2nd and 3rd generations have not reached their intended service life indicators and are generally in good condition.
Currently, Russia is developing a program for the construction of low-power floating nuclear power plants. The power units of floating nuclear power plants are planned to be created on the basis of ship reactor plants of the KLT-40 type (the prototype was the OK-900 reactor), which have proven themselves in operation on nuclear ships. For example, the nuclear power plant of the nuclear icebreaker "Arktika" (OK-900 reactor) was successfully operated from 1975 to October 3, 2008; for 176,384 hours of operation with an average power of 63.1 MW, energy production amounted to 11,132,456 MW*hours. It should be noted that the icebreaker's reactor installation had a design life of 90,000 hours when operating at a rated power of 170 MW, and, therefore, the reactor's energy output could be 15.5 million MW*hours.

Nuclear power plants of nuclear submarines are fundamentally no different from icebreaking installations. Essentially, pressurized water boat reactor technology created the basis for nuclear power plants with pressure vessel reactors.
“We have always strived to create dual-use nuclear power plants, because the creation of military and civilian equipment based on a single technology is very effective for improving both,” says Academician N.S. Khlopkin. It was in the nuclear power plants of nuclear submarines that technical solutions were used that today have become mandatory for large-scale nuclear power: the cores had negative feedback on the temperatures of the fuel and moderator, and the nuclear power plants themselves had a protective fence in the form of a durable RO casing.

Experts from the Russian Research Center “Kurchatov Institute”, when developing the concept for the construction of underground nuclear power plants, back in 1993, noted that “due to their small dimensions and weight, shipborne solutions for power plants can also be used in underground nuclear power plants. Comprehensive automation, hermetically sealed equipment, minimizing liquid and gaseous waste, mature technology and high quality manufacturing due to most of the installation work being carried out at machine-building plants - all these properties fit very well into the concept of an underground nuclear power plant.”

Reactor vessels are equipment with a long production cycle and are the most expensive parts of nuclear power plants. The only enterprise that currently produces such equipment is Izhora Plants. The technological cycle for manufacturing a reactor vessel, depending on the type of reactor, is 2-3 years. Considering the limited production capabilities of the Izhora Plant, according to the authors, it is not advisable to load it with additional orders for floating nuclear power plants.
It should also be taken into account that the cost of manufacturing reactors for a floating nuclear power plant is, according to various estimates, from 40 to 60% of the total cost of the station. Thus, during the construction of floating nuclear power plants, it seems economically feasible to use ready-made radioactive materials of decommissioned nuclear submarines.

Nuclear submarines of the 2nd - 3rd generations that are in operation or are at the stages of decommissioning and temporary storage afloat are fully suitable for these purposes (the total number of such nuclear submarines is approximately 140 units). The use of cut-off ROs already formed during the dismantling of nuclear submarines 1-3 is subject to separate consideration in each specific case.
Nuclear power plants for civil and military purposes have minor design differences. The 2nd generation nuclear submarines expected to be dismantled have 2 reactors with a thermal power of 90 MW, the 3rd generation nuclear submarines have 1-2 reactors with a thermal power of 180 MW.

The report will examine one of the components that has a significant impact on the safety of using nuclear power units of decommissioned nuclear submarines - embrittlement of the reactor hull steel under the influence of a flux of fast neutrons. The material of reactor vessels for civil and military purposes is the same - steel type 15Х2МФАА.

Operating a nuclear power plant at partial loads significantly reduces the lifespan of the reactor vessel, which is determined by a shift in the critical fragility temperature of the vessel material, which is mainly caused by the fluence of fast neutrons. Studies of the base metal and metal of the welded seams of the reactor vessels of the nuclear icebreaker "Lenin", carried out after its decommissioning with a service life of 106,700 hours, confirmed the possibility of extending the design hourly service life of reactor vessels operating at less than nominal power.

To study the possibility of using nuclear power plants for dismantled nuclear submarines, the authors assessed the embrittlement of nuclear submarine reactor vessels using standard methods and operational parameters achieved by the reactors of the icebreaker "Arktika".
The critical brittleness temperature of the reactor vessel material (Tk) is a factor limiting its service life and is determined by the sum

ТК = ТК0 + ΔТТ + ΔТN + ΔТF, (1)

where TK0 is the critical brittleness temperature of the material in the initial state,
ΔТТ – shift of the critical brittleness temperature due to temperature aging;
ΔТN – shift of the critical brittleness temperature due to cyclic damage (for shipboard nuclear power plants ΔТN is not a determining factor and can be taken equal to zero);
ΔТF – shift of the critical brittleness temperature due to neutron irradiation.

Using standard dependencies, we calculate the value of fast neutron fluence Fn on the reactor vessel of the icebreaker "Arktika":

Fn = F0*(ТF/AF)3 = 1018*(110/23)3 = 1.1 1020 cm - 2 , (2)

where AF is the embrittlement coefficient of the bottom weld;
F0 = 1018 cm - 2 – fluence threshold value;
ТF = 110 0С – shift of the critical temperature of the ductile-brittle transition as a result of irradiation.

In this case, the average fast neutron flux density on the reactor vessel during operation τ will be

φb = Fn/τ = 1.1 1020/176384 3600 = 1.73 1011cm – 2c – 1, (3)

and, therefore, the operating time of the reactor at the average power during operation is

τ = Fn/φb 3600 = 1.1 1020/1.73 1011 3600 = 176622 hours. (4)

The result obtained is in good agreement with the recorded operating time of the reactor of the icebreaker "Arktika", which means that the shift in the critical temperature of the ductile-brittle transition was accepted correctly. Based on these data and taking into account that the fast neutron flux densities in the reactors of icebreakers and nuclear submarines are approximately the same, it can be assumed that the reactors of dismantled nuclear submarines are capable of achieving energy output of 11 - 12 million MW*hours or more.

Nuclear power plants of dismantled nuclear submarines, according to experts, are far from developing service life indicators. The specificity of nuclear submarine operation is that the share of nuclear power plant operating modes at loads close to maximum is small. In addition, starting from the 90s of the twentieth century, nuclear submarines did not go to sea so often.
Considering that the rated power of 2nd generation nuclear submarine reactors is 90 MW, the average power during the operation of most of them did not exceed 30%, i.e. 27 MW, and the operating time at power was about 40,000 hours, we get an energy output of about 1.08 million MW*hours.

Considering the neutron flux densities in the reactors of icebreakers and nuclear submarines to be close in value, and also assuming that the values ​​of the neutron flux densities are proportional to the power of the reactors, and, therefore, the fluence of fast neutrons on the reactor vessel is proportional to its energy production, we have a fluence value for energy production of 1.08 million. MW*hours Fn = 1.07∙1019 cm – 2. In this case, the shift in the critical temperature of the ductile-brittle transition for the material of nuclear submarine reactor vessels will be

ТF = Aw*(Fn/F0)1/3 = 23*(1.07∙1019/1018)1/3 ≈ 49.5 0С. (5)

Consequently, the residual life of the nuclear submarine reactor vessel based on the fluence of fast neutrons on the vessel is 10 - 11 million MW*hours, and possibly more.

Calculating the fluence of fast neutrons on the reactor vessel is fraught with certain difficulties:
− at the end of the core campaign, the neutron flux density increases;
− there is no accurate information about the neutron flux density in the reactor (especially fast neutrons);
− during the operation of the reactor, several active zones are “burned” in it, which leads to the accumulation of errors in determining the fluence;
− witness samples are not loaded into ship reactors, allowing one to judge changes in the physical and mechanical properties of hull steel.

More precisely than the fluence of fast neutrons, the energy output of the reactor is determined as a result of operation. Therefore, the dependence of the shift in critical temperature as a result of neutron irradiation on the energy output of the reactor is of considerable interest. Obviously, this dependence will have the same form

ТF = Aw*(W/W0)1/3, (6)

where Aw is the embrittlement coefficient due to energy production,
W – achieved energy production,
W0 – threshold energy production.

This dependence is valid in the range of changes in energy production from 1*106 MW*hour to 3*107 MW*hour. Since the reactors of all shipboard nuclear power plants are manufactured using the same technology from 15Kh2MFAA steel and have approximately the same thickness of the iron-water protection of the hull, during the calculation it was assumed that Aw = 49.5.

The obtained dependence allows us to predict the shift in the critical temperature of fragility as a result of neutron irradiation of the material of ship reactor vessels from energy production (Fig. 2). Analysis of the curve shows that ship reactors are capable of achieving an energy output of 15.5*106 MW*hours, while the shift in the critical brittleness temperature will not exceed 125 0 C.

Figure 2. Prediction of the shift in critical brittleness temperature from neutron irradiation for ship reactors.

Thus, the residual resource of a 2nd generation nuclear power plant can reach a maximum value of 14.4 106 MW*hours (actually about 10*106 MW*hours). It follows that when using nuclear power plants from dismantled nuclear submarines of the 2nd generation as part of the power modules of floating nuclear power plants operating with capacity utilization factor (installed power utilization factor) = 0.7, they will be able to operate for about 25 years before dismantling.

If we assume that for a 3rd generation nuclear submarine the average power level is approximately 30% or 54 MW for a 2nd generation nuclear submarine, and the operating time at this power is about 30,000 hours, then we obtain an energy output of 1.62*106 MW*hours. Then the residual resource of these reactor vessels in terms of energy production will be about 13.9 * 106 MW * hours. When operating on floating nuclear power plants with capacity factor = 0.7, the possible operating time of these reactors will be approximately 110 thousand hours or approximately 12.5 years.

Thus, the main factor that determines the service life of the reactor vessel material—the shift in the critical brittleness temperature as a result of neutron irradiation of nuclear submarine reactors—is not a basis for refusing to use reactor installations of dismantled nuclear submarines as power modules for floating nuclear power plants.
An approximate methodology for solving this issue can be represented by the diagram in Figure 3.

Rice. 3. Methodological scheme for resolving the issue of using nuclear power units of nuclear submarines as a power module at a floating nuclear power plant.

In addition, the high reliability and survivability of nuclear power plants has been confirmed both by many years of operating experience and by the loss of submarines that have occurred. The reactors of all sunken nuclear submarines were reliably shut down, and radiation contamination of the water area was never recorded. The latest example of this is the Kursk nuclear submarine disaster (August 2000).

Upon reaching the maximum energy output, the impact strength characteristics of the reactor vessel metal can be restored by dry low-temperature annealing, the technology of which has been developed and used in our country for many years. From 1987 to 1992, recovery annealing was carried out on 12 VVER-440 reactor vessels in Russia, Germany, Bulgaria and Czechoslovakia. During one of the first annealings on weld material irradiated to a fluence of 1020 cm-2, the dependence of the recovery of the critical temperature (Tc) on the annealing temperature at an annealing time of 150 hours was studied. During the experiments, it was found that in almost all cases the impact strength was restored to values ​​corresponding to the non-irradiated material, and the maximum restoration of the properties of irradiated 15Kh2MFAA case steel at an annealing temperature of 460 - 4700C occurs in a time of 170 hours.

The planned resource of the KLT-40S reactors, which are planned to be installed on floating nuclear power plants, is 40 years, and once every 10 years the plants must be towed to shipbuilding enterprises for repairs. If RO of dismantled nuclear submarines is used at a floating nuclear power plant, then during scheduled repairs the reactor vessels can be annealed, as a result of which the time resource will be doubled and will practically coincide with the service life of newly built KLT-40S reactor vessels.

A separate issue is the possibility of using a steam turbine unit (STU) of a dismantled nuclear submarine. The thermal design of the nuclear submarine steam turbine differs from those designed for a floating nuclear power plant in the absence of a thermal feedwater deaerator (the installation of which is not difficult) and a higher rotation speed of the main turbine. The question of how to use the main turbine can be resolved in two ways. Firstly, reducing the rotation speed of the main turbine to 3000 rpm will slightly reduce its power, but will allow it to work in conjunction with a turbogenerator that produces a current with a frequency of 50 Hertz. In this case, excess steam can be used to transfer thermal energy to shore through an intermediate heat exchanger.

Secondly, the use of the main turbine over the entire range of rotation speeds will require the use of static frequency converters to supply electricity of the required quality to the network. In both options for using the main turbine, it is possible to abandon the use of auxiliary turbogenerators, replacing them with transformers for the own needs of floating nuclear power plants. Auxiliary turbogenerators are replaced by diesel generators, the power of which ensures the cooling of both installations and the commissioning of one of the nuclear power plants. This will allow excess steam to be used to generate thermal energy. In addition, when using a nuclear power plant of a nuclear submarine on a floating power unit, there will be no need to use steam refrigeration machines, as a result of which excess steam is generated, which can be used both in the deaerator and to generate thermal energy and transfer it to the shore. Thus, the STU equipment of dismantled nuclear submarines can also be used as part of the energy module at floating nuclear power plants.

Recycled nuclear submarines of the 2nd and 3rd generations have a wide range of reactor powers from 70 to 190 MW and main turbines from 15 to 37 MW. This makes it possible to select the required capacities of the main power equipment for use at floating nuclear power plants.

The cost of construction of a turnkey floating nuclear power plant is estimated at more than $150 million, while approximately 80% of it is determined by the cost of the nuclear power plant and steam turbine unit. The use of nuclear power plants from dismantled nuclear submarines will significantly reduce this cost.

The mass of reactor waste from two reactor installations of dismantled nuclear submarines of the 2nd generation is about 1200 tons, and that of the 3rd generation is about 1600 tons. This allows the reactor and turbine compartments to be used as a single energy module mounted on a floating nuclear power plant. In this case, we will receive a previously built and paid for nuclear power plant in a protective shell, the function of which is performed by the durable hull of the nuclear submarine. One of the possible options for such a design of a floating nuclear power plant is shown in Fig. 4.

Figure 4. Option for placing the power module (nuclear submarine reactor compartment) on floating nuclear power plants.

The use of the proposed technology will inevitably encounter a number of problems that need to be solved in the near future. Such problems include:
− lack of a procedure for transferring nuclear power plants for military purposes to nuclear power plants for the peaceful use of atomic energy;
− lack of analysis of the compliance of nuclear power units of nuclear submarines of 2-3 generations with the requirements of regulatory documents of Rostechnadzor and the Ministry of Health and Social Development for floating nuclear power plants;
− the need to justify the residual life, as well as the possibility of extending the assigned life indicators of the main equipment of the nuclear power plant for each decommissioned nuclear submarine;
− the need to change the design of floating nuclear power plants under construction or design.

To solve these problems, it is necessary to carry out a significant complex of R&D.
It should also be noted that the use of radioactive waste from decommissioned nuclear submarines is not limited to their use for floating nuclear power plants. Possible applications could be their use in the construction of underground nuclear power plants.

Conclusions:
1. The proposed innovative technology for using nuclear power units from dismantled nuclear submarines will allow:
− significantly reduce the costs of constructing floating nuclear power plants and reduce their construction and payback time;
− reduce the costs of dismantling nuclear submarines;
− significantly reduce the amount of radioactive waste and the costs of handling it;
− make full use of the potential of the nuclear power plant of nuclear submarines:
− during the operation of nuclear power plants of dismantled nuclear submarines as part of a floating nuclear power plant, to finance the future disposal of radioactive waste.
2. To implement this technology, it is necessary to deploy in the near future a R&D complex that will make it possible to scientifically substantiate the technical feasibility of using RO from dismantled nuclear submarines for the designed floating nuclear power plants.

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