Typical nuclear reactors rbmk. Rbmk high power channel reactor. Chaes accident
The reactor is located in a concrete shaft with a square section measuring 21.6×21.6×25.5 m. Figures 1.3 and 1.4 show the metal structures of the RBMK-1000 reactor, which are located in the concrete shaft.
On both sides of the central lock, symmetrically to a vertical plane passing through the center of the reactor and directed towards the spent fuel pool, there are rooms for the main equipment: loops of the MCP, BS, downpipe shafts, rooms for the MCP collectors.
Steam collectors are located above the separators. Under the slab flooring there are communications of PVC pipelines.
NVK pipelines are located in the premises of the RGC and under the "OR" scheme.
The transfer of forces from the weight of the internal components, assemblies and communications of the reactor to concrete, as well as the sealing of the internal cavity of the reactor is carried out using welded MC, which simultaneously play the role of biological protection. Metal structures include the following structural elements: Schemes "C", "OR", "KZh", "L" and "D", "E", "G", slab flooring, "E". All of the above diagrams are shown in the longitudinal section of the reactor (see Fig. 1.4).
Metal structure of scheme "C"
The metal structure of the "C" scheme (see Fig. 1.5) is the main supporting metal structure for the "OP" scheme. Made in the form of a cross from two slabs 5.3 m high, reinforced with vertical stiffeners. Transfers the weight from the lower metal structure of the "OR" scheme, graphite masonry and NVK to the embedded parts of the cruciform foundation slab made of heat-resistant reinforced concrete at the level of +11.21 m.
Two free-standing racks serve as supports for the side biological protection.
Rice. 1.3. RBMK-1000 reactor
Rice. 1.4. Longitudinal section of the RBMK-1000 reactor
Rice. 1.5. Metal structure of scheme "C"
Scheme "C" is assembled with the help of flange bolted connections from beam-racks 5 m high, located along two mutually perpendicular planes in the form of a cross.
The upper part of the "C" pattern has projections and is fitted on the contact surface with the lower plate of the "OP" pattern.
All parts are made of 10KhSND steel, the surfaces are metallized with aluminum (0.15¸0.25 mm.) and painted with an organosilicate coating.
Environment - air with relative humidity up to 80%, and temperatures up to 270°C.
Metal structure of the "OR" scheme
The metal structure of the "OR" scheme (see Fig. 1.6) is made in the form of a drum with a diameter of 14.5 m and a height of 2 m, assembled from tube plates and a shell. Serves as a support for the graphite stack, the "KZh" scheme and communications at the bottom of the reactor, is the lower biological protection of the reactor. The stiffening ribs forming the central cross coincide with the similar ribs of the MC of the "C" scheme.
Rice. 1.6. Metal structure of the "OR" scheme
The metal structure of the "OR" scheme is connected to the body of the side bioprotection by two (upper and lower) bellows compensators, which provide compensation for thermal expansion of the structures and tightness of N 2 -He and N 2 cavities.
In the MC of the "OR" scheme are located:
Lower paths of technological and special channels;
Thermocouple sleeves MK;
Pipes for supplying nitrogen-helium mixture to the internal cavity of the reactor;
PGM removal pipes from the reactor cavity;
Drainage pipes from the top plate;
Pipes for supplying and discharging N 2 from the internal cavity of the MC of the "OR" scheme.
All parts of the MC of the "OR" scheme are made of steel 10KhSND.
MK working conditions:
Lower plate temperature - up to 270 °C;
Upper plate temperature - up to 350 °C with local heating up to 380 °C;
The environment for the lower plate is air with a relative humidity of up to 80%, for the upper plate - N 2 -Not a mixture.
Metal structures of schemes "L" and "D"
Metal structures of schemes "L" and "D" are the lateral bioprotection of the reactor, reduce radiation fluxes to the concrete of the mine; serve as a heat shield; contribute to the cooling of the reactor shell. The metal structure of the “L” scheme (see Fig. 1.7) is also supporting structure for the "E" scheme.
Rice. 1.7. Metal structure of the scheme "L"
The metal structures of schemes "L" and "D" are in the form of hollow annular tanks filled with water and divided by partitions into 16 compartments. The metal structure of the "D" scheme (see Fig. 1.8) is the upper part of the biosecurity and is based on the metal structure of the "L" scheme.
Rice. 1.8. Metal structures of schemes "L" and "D"
The outer diameter of the blocks of schemes "L" and "D" - 19 m.
The inner diameter of the blocks of the "L" scheme is 16.6 m.
The inner diameter of the MK blocks of the "D" scheme is 17.8 m.
The height of the MK blocks of the "L" scheme is 11.05 m.
The height of the MK blocks of the "D" scheme is 3.2 m.
All elements of the MC scheme "L" and "D" are made of steel 10KhSND.
In the metal structures of schemes "L" and "D" there are channels of working and starting ionization chambers (RIK and PIK), as well as drainage pipes and thermocouple sleeves (one for each compartment) for measuring the water temperature in the compartments.
The water volumes of the MC are interconnected, the supply of cooling water is made to the lower part of the MC blocks of the “L” scheme, and the outlet is from the upper part of the MC blocks of the “D” scheme. The space between the inner cylinder of the MC of the "L" scheme and the MC of the "KZh" scheme is filled with nitrogen. The installation space formed by the outer cylinder of the MK of schemes "L" and "D" and the reactor shaft is filled with sand, which serves as additional bioprotection. The lower part of the installation space is filled with crushed stone (200¸400 mm) to prevent sand from entering the holes of the DN 150 drainage pipe.
MK working conditions:
Water temperature in MC schemes - up to 60 °С, but not more than 90 °С;
The environment from the side of the MC of the "KZh" scheme is nitrogen with a relative humidity of not more than 80%;
The environment from the side of the reactor shaft is air with a relative humidity of not more than 80%.
Metal structure of the "KZh" scheme
The metal structure of the "KZh" scheme (see Fig. 1.9), together with the lower plate of the "E" scheme and the upper plate of the "OR" scheme, form a sealed cavity around the reactor masonry - reactor space, in which N 2 is retained - Not a mixture.
Rice. 1.9. Metal structure of the "KZh" scheme
The design of the "KZh" scheme is made in the form of a cylindrical welded casing with a diameter of 14.5 m from sheet metal st. Annular stiffening ribs are welded along the outer surface of the casing. To reduce the voltage in the compensators during reactor operation, the “KZh” circuit is welded to the bottom plate of the “E” circuit and the top plate of the “OR” circuit with a preload.
MK working conditions:
Casing temperature - up to 350 °С;
Environment inside - N 2 -Not a mixture with a pressure of 150 mm of water column, outside - N 2 with a pressure of 200¸250 mm of water column.
Metal structure of the scheme "E"
The metal structure of scheme "E" (see Fig. 1.10) serves as the upper biological protection of the reactor and a support for the TC, special. channels, slab flooring and communications pipelines at the top of the reactor. Scheme "E" is a drum with a diameter of 17 m, a height of 3 m, and is assembled from tube plates united by a cylindrical shell and internal vertical stiffeners, upper and lower plates 40 mm thick. Material MK - steel 10HSND.
Rice. 1.10. Metal structure of the scheme "E"
The following are welded into the metal structure of scheme “E”:
1. the upper parts of the paths of technological and special channels (except for the RIK and PIK channels);
2. tracts of television cameras;
3. thermocouple sleeves MK;
4. PGM outlet pipes from the internal cavity of the reactor;
5. Nitrogen inlet and outlet pipes.
The inner cavity is filled with serpentenite filling (60% by weight) and hali (40%). The MC of the scheme is supported by 16 roller bearings on the lateral bioprotection of the MC cx. "L" and "D", each of which is designed for a load of 750 tons. The MC of scheme "E" also includes the upper and lower horizontal compensators, which provide thermal expansion while maintaining the tightness of N 2 -He and N 2 cavities. The tightness of the internal cavity of the MC of scheme "E" is ensured by welding with checking the seams for tightness.
MK working conditions:
Bottom plate temperature up to 350 °С with local heating up to 370 °С,
Upper plate temperature - up to 290 °C,
Environment above the top plate - air with humidity up to 80%, under the bottom plate - N 2 - Not a mixture.
Metal structure of the scheme "G"
The metal structure of the "G" scheme (see Fig. 1.11) consists of slabs and floor ducts at the level of 35.5 m, which serve as biological protection of the central lock from ionizing radiation from the upper communications of the reactor.
The lower part of the scheme, 70 cm thick, is made in the form of metal boxes made of 10KhSND steel filled with a mixture of serpentinite gall (14% by weight) and steel shot (86%).
The upper part of the scheme is made of carbon steel plates 10 cm thick, lined with corrosion-resistant sheet steel 0Kh18N10T 5 mm thick on the side of the central lock. The beams and boxes of the scheme have breathing bolts M-24 to communicate the backfill with the atmosphere and prevent the formation of explosive gas in the backfill.
Rice. 1.11. Metal structure of the "G" scheme and slab flooring
The openings above the channels of the starting and working ionization chambers have removable plates. In the space between the boxes and plates there are cables coming from the KSUZ, DKE, KD, PIK, RIK servo drives, from thermocouples located in the masonry, support and protective plates and compartments of the MC of the "L" scheme and drainage pipes of the "G" scheme. The outer surfaces of the beams and ducts of the circuit are metallized with an aluminosilicate coating 0.15¸0.25 mm in two layers.
The metal structure of scheme "G" works in an environment with relative humidity up to 80%. The temperature of beams and boxes reaches up to 250 °C, steel plates up to 100 °C, lining up to 50 °C.
1.Introduction…………………………………………………………….4
2.Main characteristics of the RBMK-1000 reactor………………7
2.1 Thermal scheme with RBMK-1000 reactor……………………7
2.2 In-reactor structures………………………………...12
2.3 Shut-off and control valve………………………………....18
2.4 Unloading and loading machine……………………………….21
2.5 Fuel assemblies (FA)…………………………….....25
2.6 Design of protection against ionizing radiation of the reactor..28
3. Types and purpose of pipelines and their components with drawings and diagrams, operating parameters and main forces acting on pipelines…………………………………………………………………….32
4. The main defects that occur in pipelines with an analysis of the causes of their occurrence, methods for detecting defects…………………………….48
5. The procedure for the withdrawal of pipelines for repair with the preparation of the workplace and disconnection from the thermal circuit………………………………………………….53
6.Technology of repair production, intermediate control……….57
7.Testing of pipelines…………………………………………………..60
8.Commissioning……………………………………………………….61
9.Conclusion……………………………………………………………………..63
10.List of abbreviations………………………………………………………….64
11. List of used literature…………………………………….66
INTRODUCTION
The RBMK-1000 reactor is a reactor with non-refueling channels; in contrast to reactors with refueling channels, the fuel assembly and the process channel are separate units. Pipelines are connected to the channels installed in the reactor with the help of permanent connections - individual paths for supplying and removing the coolant. The fuel assemblies loaded into the channels are fixed and compacted in the upper part of the channel riser. Thus, when fuel is refueled, it is not required to open the coolant path, which allows it to be carried out using appropriate refueling devices without shutting down the reactor.
When creating such reactors, the problem of economical use of neutrons in the reactor core was solved. For this purpose, fuel element claddings and channel tubes are made of zirconium alloys that weakly absorb neutrons. During the development of RBMK, the temperature limit of the operation of zirconium alloys was not high enough. This determined the relatively low parameters of the coolant in the RBMK. The pressure in the separators is 7.0 MPa, which corresponds to a saturated steam temperature of 284°C. The layout of the RBMK units is single-loop. After the core, the steam-water mixture enters the separator drums through individual pipes, after which the saturated steam is sent to the turbines, and the separated circulating water, after mixing with the feed water entering the separator drums from the turbine plants, is supplied to the reactor channels with the help of circulation pumps. The development of the RBMK was a significant step in the development of the nuclear power industry in the USSR, since such reactors make it possible to create large nuclear power plants of high power.
Of the two types of thermal neutron reactors - pressurized pressurized water and channel water-graphite, used in nuclear power Soviet Union, the latter turned out to be easier to master and implement. This is explained by the fact that for the manufacture of channel reactors general machine-building plants can be used and such unique equipment is not required, which is necessary for the manufacture of pressurized water reactors.
The efficiency of RBMK type channel reactors largely depends on the power taken from each channel. The power distribution between the channels depends on the neutron flux density in the core and the fuel burnup in the channels. At the same time, there is a power limit that cannot be exceeded in any channel. This power value is determined by the heat removal conditions.
Initially, the RBMK project was developed for an electrical power of 1000 MW, which, with the selected parameters, corresponded to a thermal power of the reactor of 3200 MW. With the number of working channels available in the reactor (1693) and the obtained coefficient of non-uniformity of heat release in the reactor core, the maximum channel power was about 3000 kW. As a result of experimental and computational studies, it was found that with a maximum mass vapor content at the outlet of the channels of about 20% and the specified power, the necessary reserve is provided before the heat removal crisis. The average steam content in the reactor was 14.5%. Power units with RBMK reactors with an electric capacity of 1000 MW (RBMK-1000) are in operation at the Leningrad, Kursk, Chernobyl NPPs, and Smolensk NPP. They have proven themselves as reliable and safe installations with high technical and economic indicators. If they are not specifically blown up.
To increase the efficiency of RBMK reactors, the possibilities of increasing the maximum power of the channels were studied. As a result of design developments and experimental studies, it turned out possible way intensification of heat transfer to increase the maximum allowable power of the channel by 1.5 times to 4500 kW while increasing the allowable vapor content to several tens of percent. The necessary intensification of heat transfer was achieved due to the development of fuel assemblies, the design of which provides for heat transfer intensifiers. With an increase in the allowable power of the channel to 4500 kW, the thermal power of the RBMK reactor was increased to 4800 MW, which corresponds to an electric power of 1500 MW. Such RBMK-1500 reactors operate at the Ignalina NPP. An increase in power by 1.5 times with relatively small design changes while maintaining the dimensions of the reactor is an example of a technical solution that gives a big effect.
MAIN CHARACTERISTICS OF THE RBMK-1000 REACTOR
Thermal scheme with the RBMK-1000 reactor
PART.
Types and purpose of pipelines and their components with drawings and diagrams, operating parameters and the main forces acting on pipelines.
Pipeline classification
Pipelines, depending on the hazard class of the transported substance (explosion and fire hazard and harmfulness), are divided into groups of the environment (A, B, C) and, depending on the design parameters of the environment (pressure and temperature), into five categories (I, II, III, IV , V)
The category of the pipeline should be set according to the parameter that requires it to be assigned to a more responsible category.
The designation of a group of a certain transported medium includes the designation of a group of medium (A, B, C) and a subgroup (a, b, c), reflecting the toxicity and fire and explosion hazard of substances included in this medium.
The designation of the pipeline in general terms corresponds to the designation of the group of the transported medium and its category. The designation "pipeline I group A (b)" means a pipeline through which a medium of group A (b) is transported with parameters of category I.
The environment group of a pipeline transporting media consisting of various components is set according to the component that requires the pipeline to be assigned to a more responsible group. Moreover, if the content of one of the components in the mixture exceeds the average lethal concentration in the air according to GOST 12.1.007, then the group of the mixture should be determined by this substance. If the most dangerous component in terms of physical and chemical properties is included in the mixture in an amount below the lethal dose, the issue of assigning the pipeline to a less responsible group or category of the pipeline is decided by the design organization (project author).
The hazard class of substances should be determined according to GOST 12.1.005 and GOST 12.1.007, the values of the fire and explosion hazard indicators of substances - according to the relevant ND or the methods set forth in GOST 12.1.044.
For vacuum lines, the absolute operating pressure must be taken into account.
Pipelines transporting substances with a working temperature equal to or higher than their auto-ignition temperature, as well as non-combustible, slow-burning and combustible substances that, when interacting with water or atmospheric oxygen, can be fire and explosion hazardous, should be classified as Category I. By decision of the developer, it is allowed, depending on the operating conditions, to take a more responsible (than determined by the design parameters of the environment) category of the pipeline.
Requirements for the design of pipelines
The design of the pipeline should provide for the possibility of performing all types of control. If the design of the pipeline does not allow for external and internal inspections or hydraulic testing, the author of the project must indicate the methodology, frequency and scope of control, the implementation of which will ensure the timely detection and elimination of defects.
Branches (tie-ins)
A branch from the pipeline is performed in one of the ways. Reinforcement of branches with stiffeners is not allowed.
– Branches on technological pipelines
Connection of branches according to method "a" is used in cases where the weakening of the main pipeline is compensated by the available margins of connection strength. It is also allowed to cut into the pipeline at a tangent to the circumference of the cross section of the pipe to prevent the accumulation of products in the lower part of the pipeline.
Tees welded from pipes, stamped-welded bends, tees and bends made of blanks cast using electroslag technology can be used for pressures up to 35 MPa (350 kgf / cm2). In this case, all welds and metal of cast billets are subject to 100% ultrasonic testing.
Welded crosses and cross tie-ins are allowed to be used on pipelines made of carbon steels at an operating temperature not exceeding 250 °C. Crosses and cross tie-ins made of electric-welded pipes may be used at a nominal pressure of not more than PN 16 (1.6 MPa). In this case, the crosses must be made of pipes with a nominal pressure of at least PN 25 (2.5 MPa). Crosses and cross tie-ins from seamless pipes may be used at a nominal pressure of not more than PN 24 (provided that the crosses are made of pipes with a nominal pressure of at least PN 40. Inserting fittings into the welded seams of pipelines should be carried out taking into account clause 11.2.7.
Branches
For pipelines, as a rule, bent bends are used, made of seamless and welded longitudinal pipes by hot stamping or drawing, as well as bent and stamp-welded. With a diameter greater than DN 6.4.2 400, the root of the weld is welded, the welds are subjected to 100% ultrasonic or radiographic control.
Bent bends made from seamless pipes are used in cases where it is required to minimize hydraulic resistance pipeline, for example, on pipelines with a pulsating medium flow (in order to reduce vibration), as well as on pipelines with a nominal diameter up to DN 25. The need for heat treatment is determined by 12.2.11.
Limits of use of bent bends from pipes of the current range must correspond to the limits of use of pipes from which they are made. The length of the straight section from the end of the pipe to the beginning of the bent section must be at least 100 mm.
In pipelines, it is allowed to use welded sector bends with a nominal diameter of DN 500 or less at a nominal pressure of not more than PN 40 (4 MPa) and a nominal diameter of more than DN 500 at a nominal pressure of up to PN 25 (2.5 MPa). In the manufacture of sector bends, the angle between the cross sections of the sector should not exceed 22.5°. The distance between adjacent welds along the inner side of the bend should ensure the availability of inspection of these welds along the entire length of the weld. For the manufacture of sector bends, the use of spirally welded pipes is not allowed, with a diameter of more than 400 mm, root welding is used, welds are subjected to 100% ultrasonic or radiographic control. Welded sector bends should not be used in cases of: - high cyclic loads, for example from pressure, more than 2000 cycles; - lack of self-compensation due to other pipe elements.
Transitions
In pipelines, as a rule, stamped, rolled from a sheet with one weld, stamp-welded from halves with two welds should be used. The limits of use of steel transitions must correspond to the limits of use of connected pipes of similar steel grades and similar operating (calculated) parameters.
It is allowed to use spade adapters for pipelines with a nominal pressure of not more than PN16 (1.6 MPa) and a nominal diameter of DN 500 or less. It is not allowed to install petal transitions on pipelines intended for the transportation of liquefied gases and substances of groups A and B.
The spade transitions should be welded followed by 100% control of the welds by ultrasonic or radiographic methods. After manufacturing, the petal adapters should be subjected to heat treatment.
Stubs
Welded flat and ribbed plugs made of sheet steel are recommended for use in pipelines at nominal pressures up to PN 25 (2.5 MPa).
Plugs installed between flanges should not be used to separate two pipelines with different media, the mixing of which is unacceptable.
Limits of use of plugs and their characteristics in terms of material, pressure, temperature, corrosion, etc. must comply with the application limits of the flanges.
Requirements for pipeline fittings.
When designing and manufacturing pipeline fittings, it is necessary to comply with the requirements of technical regulations, standards and customer requirements in accordance with safety requirements in accordance with GOST R 53672.
The specifications for specific types and types of pipeline fittings should include:
Scroll normative documents, on the basis of which they design, manufacture and operate valves;
Basic technical data and characteristics of fittings;
Reliability indicators and (or) safety indicators (for valves that may have critical failures);
manufacturing requirements;
Safety requirements; - contents of delivery;
Acceptance rules;
Test methods;
List of possible failures and criteria for limit states;
Instructions for use;
The main overall and connecting dimensions, including the outer and inner diameters of the branch pipes, cutting the edges of the branch pipes for welding, etc.
The main indicators of the purpose of reinforcement (of all types and types), established in the design and operational documentation:
Nominal pressure PN (working or design pressure P);
Nominal diameter DN;
Working environment;
Design temperature (maximum temperature of the working environment);
Permissible differential pressure;
Closure tightness (tightness class or leakage rate);
Construction length;
Climatic version (with parameters environment);
Resistance to external influences (seismic, vibration, etc.);
Additional indicators of purpose for specific types of reinforcement:
Resistance coefficient (ζ) for stop and return valves;
The dependence of the resistance coefficient on the velocity pressure - for reverse valves;
Flow coefficient (for liquid and gas), seat area, setting pressure, full opening pressure, closing pressure, back pressure, setting pressure range - for safety valves;
Conditional throughput (Kvy), type of throughput characteristic, cavitation characteristics - for control valves;
Conditional capacity, adjustable pressure value, adjustable pressure range, pressure maintenance accuracy (dead zone and non-uniformity zone), minimum pressure drop at which operability is ensured - for pressure regulators;
Parameters of drives and actuators;
A) for an electric drive - voltage, current frequency, power, operating mode, gear ratio, efficiency, maximum torque, environmental parameters;
B) for hydraulic and pneumatic drives - control medium, pressure of the control medium - for pressure regulators;
Opening (closing) time - at the request of the valve customer.
The fittings must be tested in accordance with GOST R 53402 and TU, while the mandatory scope of tests must include:
On the strength and density of the main parts and welded joints operating under pressure;
For the tightness of the gate, the norms for the tightness of the gate - according to GOST R 54808 (for fittings of working means of groups A, B (a) and B (b), when testing for tightness of the gates, there should be no visible leaks - class A GOST R 54808);
For tightness relative to the external environment;
For functioning (operability). The test results must be reflected in the valve passport.
The use of shut-off valves as a control (throttling) valve is not allowed.
When installing the actuator on a valve, handwheels for manual operation must open the valve in a counterclockwise direction and close in a clockwise direction. The direction of the actuator stem axes must be determined in the project documentation.
Shut-off valves must have indications of the position of the locking element ("open", "closed").
The material of fittings for pipelines should be selected depending on the operating conditions, parameters and physical and chemical properties transported medium and ND requirements. Reinforcement made of non-ferrous metals and their alloys is allowed to be used in cases where steel and cast iron reinforcement cannot be used for justified reasons. Armature made of carbon and alloy steels may be used for environments with a corrosion rate of not more than 0.5 mm/year.
Fittings made of ductile iron of a grade not lower than KCh 30-6 and gray cast iron of a grade not lower than SCh 18-36 should be used for pipelines transporting group media.
For environments of groups A (b), B (a), except for liquefied gases; B(b), except for flammable liquids with a boiling point below 45°C; B(c) - fittings made of ductile iron may be used if the operating temperature limits of the medium are not lower than minus 30 °С and not higher than 150 °С at a medium pressure of not more than 1.6 MPa (160 kgf / cm2). At the same time, for nominal working pressures of the medium up to 1 MPa, valves designed for a pressure of at least PN 16 (1.6 MPa) are used, and for nominal pressures more than PN 10 (1 MPa) - valves designed for a pressure of at least PN 25 (2 .5 MPa). 8.13 It is not allowed to use ductile iron fittings on pipelines transporting media of group A (a), liquefied gases of group B (a);
Flammable liquids with a boiling point below 45 ° C of group B (b). It is not allowed to use fittings made of gray cast iron on pipelines transporting substances of groups A and B, as well as on steam pipelines and pipelines hot water used as satellites.
Fittings made of gray and malleable cast iron are not allowed to be used regardless of the medium, operating pressure and temperature in the following cases: - on pipelines subject to vibration;
On pipelines operating at a sharply variable temperature regime of the medium;
With the possibility of significant cooling of the armature as a result of the throttle effect;
On pipelines transporting substances of groups A and B, containing water or other freezing liquids, at a temperature of the pipeline wall below 0 °C, regardless of pressure;
In the piping of pumping units when installing pumps in open areas;
In the piping of tanks and containers for the storage of explosive and toxic substances.
On pipelines operating at an ambient temperature below 40 ° C, fittings made of appropriate alloyed steels, special alloys or non-ferrous metals should be used, having at the lowest possible case temperature the impact strength of the metal (KCV) is not lower than 20 J/cm2. For liquid and gaseous ammonia, the use of special ductile iron fittings is allowed within the parameters and conditions.
hydraulic valve actuators should use non-flammable and non-freezing fluids that meet the operating conditions.
In order to exclude the possibility of condensation in pneumatic drives in winter time the gas is dried to the dew point at negative design temperature pipeline.
For pipelines with a nominal pressure of more than 35 MPa (350 kgf / cm2), the use of cast fittings is not allowed.
Fittings with flange sealing "protrusion-cavity" in the case of the use of special gaskets can be used at a nominal pressure of up to 35 MPa (350 kgf / cm2)
To ensure safe operation in automatic control systems, when choosing control valves, the following conditions must be met:
The pressure loss (pressure drop) on the control valves at the maximum flow rate of the working medium must be at least 40% of the pressure loss in the entire system;
When the liquid flows, the pressure drop across the control valves in the entire control range should not exceed the value of the cavitation drop.
On the body of the valve, in a visible place, the manufacturer marks the following volume:
Name or trademark of the manufacturer;
Factory number; - Year of manufacture;
Nominal (working) pressure РN (Рр); - nominal diameter DN;
Temperature of the working medium (when marking the working pressure Pp - mandatory);
Arrow indicating the direction of the flow of the medium (with one-sided supply of the medium); - product designation;
Steel grade and heat number (for bodies made of castings); - additional signs markings in accordance with customer requirements, national standards.
The delivery set of pipeline fittings should include operational documentation in the amount of:
Passport (PS);
Operation manual (RE);
Operational documentation for components (drives, actuators, positioners, limit switches, etc.). The form of the passport is given in Appendix H (reference). The operating manual should contain: - a description of the design and principle of operation of the valve;
The order of assembly and disassembly; - repetition and explanation of the information included in the marking of the reinforcement;
List of materials for the main parts of the reinforcement;
Information on the types of hazardous effects, if the valve may pose a danger to human life and health or the environment, and measures to prevent and prevent them;
Reliability indicators and (or) safety indicators;
Scope of input control of fittings before installation;
Methodology for conducting control tests (checks) of valves and its main components, procedure Maintenance, repair and diagnostics.
Before installation, the fittings must be subjected to incoming inspection and tests to the extent specified in the operating manual. Installation of fittings should be carried out taking into account safety requirements in accordance with the operating manual.
Valve safety during operation is ensured by the following requirements:
Valves and drive devices must be used in accordance with their intended use in terms of operating parameters, media, operating conditions;
Valves should be operated in accordance with the operation manual (including design contingencies) and technological regulations;
The shut-off valve must be fully open or closed. It is not allowed to use shut-off valves as control valves;
Fittings must be used in accordance with its functional purpose;
Production control of industrial safety of fittings should provide for a system of measures to eliminate possible limit states and prevent critical failures of fittings.
Not allowed:
Operate valves in the absence of marking and operational documentation;
Carry out work to eliminate defects in body parts and tighten threaded connections under pressure;
Use fittings as a support for the pipeline;
To use levers to control the armature, extending the shoulder of the handle or flywheel, which are not provided for in the instruction manual;
Use extensions for fastener wrenches.
PROCEDURE FOR PIPING PIPING IN REPAIR WITH PREPARATION OF THE WORKPLACE AND DISCONNECTING FROM THE HEATING CIRCUIT.
In case of rupture of pipes of the steam-water path, collectors, live steam pipelines, reheating steam and extractions, pipelines of the main condensate and feed water, their steam-water fittings, tees, welded and flanged joints, the power unit (boiler, turbine) must be turned off and immediately stopped.
If cracks, bulges, fistulas are found in live steam pipelines, reheating steam and extractions, feed water pipelines, in their steam-water fittings, tees, welded and flanged joints, the shop shift supervisor should be immediately notified about this. The shift supervisor is obliged to immediately determine the danger zone, stop all work in it, remove personnel from it, protect this zone, post safety signs "No passage", "Caution! Danger zone" and take urgent measures to disable the emergency section by means of remote drives. If it is not possible to reserve the emergency section during shutdown, then the relevant equipment associated with the emergency section must be stopped. The shutdown time is determined by the chief engineer of the power plant with the notification of the power system engineer on duty.
If destroyed supports and hangers are found, the pipeline must be disconnected, and the fastening restored. The shutdown time is determined by the chief engineer of the power plant in agreement with the power system engineer on duty.
If damage to the pipeline or its fastening is detected, a thorough analysis of the causes of damage and the development of effective measures to improve reliability are necessary. If leaks or vapors are detected in fittings, flange connections or from under the insulating coating of pipelines, this should be immediately reported to the shift supervisor. The shift supervisor is obliged to assess the situation and, if a leak or vapor poses a danger to maintenance personnel or equipment (for example, vapor from under insulation), take action. Leaks or vapors that do not pose a risk to personnel or equipment (for example, vapors from stuffing box seals) should be inspected every shift.
Pipelines must be handed over for repair after the planned overhaul period established on the basis of the current technical operation standards and, in most cases, be repaired simultaneously with the main equipment. Delivery of the pipeline for repair before the expiration of the planned overhaul period is necessary in case of emergency damage or emergency condition, confirmed by an act indicating the causes, nature and extent of damage or wear. Defects in pipelines identified during the overhaul period and not causing an emergency shutdown must be eliminated at any next shutdown.
Steam pipelines operating at a temperature of 450 ° C or more must be inspected before overhaul.
When handing over for repair, the customer must transfer to the contractor the design and repair documentation, which contains information about the condition of the pipeline and its components, about defects and damage. Documentation must be prepared in accordance with GOST 2.602-68*. After repair, this documentation must be returned to the customer.
In accordance with the Rules for the organization, maintenance and repair of equipment during overhaul boiler and station pipelines, the following works should be included in the nomenclature:
Examination technical condition steam pipelines;
Checking the technical condition of flange connections and fasteners, replacing worn-out studs.
Checking the tightening of springs, inspection and repair of suspensions and supports.
Inspection of welds and metal.
Overcooking of defective joints, replacement of defective elements of the pipeline or fastening system.
Inspection and repair of samplers and sample coolers.
Repair of thermal insulation.
When pipelines are inspected, sagging, bulges, fistulas, cracks, corrosion damage and other visible defects should be recorded. In case of fault detection of flange connections, the condition of sealing surfaces and fasteners should be checked. In case of flaw detection of supports and suspensions, cracks in the metal of all elements of supports and suspensions and residual deformation in the springs should be recorded.
The order and scope of control over the metal of pipelines is determined by the NTD. The control is carried out under the technical guidance of the metal laboratory.
The customer has the right to interfere in the performance of the contractor's work, if the latter:
Made defects that may be hidden by subsequent work;
Does not perform technological and regulatory requirements technical documentation.
During repair work related to the installation or dismantling of spring blocks or pipeline parts, the work envisaged by the project or technological map a sequence of operations that ensures the stability of the remaining or newly installed pipeline units and elements and prevents the fall of its dismantled parts.
Before disassembly fixed support or by cutting the pipeline when re-welding welded joints according to the conclusions of flaw detectorists or when replacing any elements of the pipeline, the springs on the nearest two hangers on each side of the repaired section must be fixed with threaded welded ties. At a distance of no more than 1 m on both sides of the place of pipeline unloading (or dismantling of a fixed support), temporary supports (fastening) should be installed. These supports must ensure the displacement of pipelines along the axis, required during welding, and the fixation of the pipeline in the design position. Attaching these ends to adjacent pipelines, supports or hangers is not allowed.
On both sides of the repaired section, punching should be done on the pipes, the distance between the punching points should be recorded in the act. When restoring the pipeline, cold stretching should be performed in such a way that the deviation of the distance between the punching points does not exceed 10 mm.
After dismantling a section or element of the pipeline, the free ends of the remaining pipes must be closed with plugs.
When cutting a pipeline at several points, it is necessary to perform operations in each case.
For any cutting of the pipeline after welding of the closing joint, it is necessary to draw up an act with its entry in the cord book.
After completion of repair work related to cutting the pipeline or replacing parts of its supports, it is necessary to check the slopes of the pipeline.
When replacing a defective spring, the replacement spring must be selected according to the appropriate allowable load, preliminarily calibrated and compressed to the design height for the cold state. After installing in the suspension unit and removing the fixing ties, check the height of the spring and, if necessary, readjust. When welding the couplers, contact of the coils of the springs with an electric arc is unacceptable, and when cutting - with a burner flame, which can cause damage to the springs.
When replacing a spring in a support due to its damage or inconsistency with the design loads, you should:
Lay the plates under the spring block (if the replacement block has a lower height than the replaced one);
Dismantle the base post and reduce its height (if the replacement unit is taller than the one being replaced).
When changing the heights of the springs in the spring support, it is necessary to remove the adjustable block, change its height on the calibration device and install it in the support.
After completing the work on adjusting the heights of the springs, the heights of the springs after adjustment should be recorded in the operational logs (see Appendix 6), and the positions of the pipeline in the cold state should be specified on the displacement indicators.
Any changes in the design of the pipeline, made during the period of its repair and agreed with the design organization, must be reflected in the passport or cord book of this pipeline. When replacing damaged parts of the pipeline or parts that have exhausted their service life, the corresponding characteristics of the new parts must be recorded in the cord book.
After the completion of repair and adjustment work, an appropriate entry must be made in the repair log and an act of commissioning must be drawn up with entry in the cord book.
PIPELINE TESTING
COMMISSIONING
The filling of the pipeline after the repair work is carried out according to the approved plan, which provides for technological measures aimed at removing the vapor-air phase in the pipeline. As a rule, this operation is carried out using elastic separators.
It is advisable to put the pipeline into operation after repair work with condensate degassed under atmospheric conditions.
The pipeline can be filled with stable condensate at any initial pressure inside the pipeline. If the pipeline is filled with unstable condensate or liquefied hydrocarbon gas, then this operation must be carried out after increasing the pressure of the gas, water or stable product in the pipeline above the vapor pressure of the pumped product and after introducing mechanical separators into the pipeline.
If it is necessary to displace water from the pipeline using an unstable product, measures must be taken to protect against hydrate formation (use of separators, hydrate formation inhibitors, etc.)
In the absence of mechanical separators, it is recommended to partially fill the pipeline with stable condensate before filling with the pumped product.
The gas or water used during purging (flushing) and subsequent testing of the product pipeline and displaced by the product using separators is released from the pipeline through the purge nozzles.
At the same time, control over the content of the product in the jet leaving the purge nozzle must be organized to reduce the risk of environmental pollution and reduce product losses.
After the pipeline is filled with degassed condensate, the pressure is raised above the minimum allowable operating pressure, which will be determined by the degassing pressure, the amount of pressure loss due to friction, the composition of the product, the profile of the route and the temperature itself " hot spot" pipeline.
The rise in pressure in the pipeline is carried out by pumping condensate with a closed valve at the end of the pipeline section.
After increasing the pressure at the beginning of the condensate pipeline above the minimum allowable, it is allowed to start pumping unstable condensate.
Maintaining the minimum allowable working pressure in the pipeline during operation is ensured by a pressure regulator "to itself", installed directly in front of the consumer.
Designs of channels of uranium-graphite reactors of nuclear power plants
The heat-releasing part of the RBMK-1000 channel
(Fig. 2.31) consists of two fuel assemblies, a bearing central rod, a shank, a rod, a tip. The fuel assembly is assembled from 18 rod-type fuel rods 13.5x0.9 mm in diameter, a frame and fasteners; TVS are interchangeable. The frame consists of a central tube, on which one end and ten spacer grids are fixed. Spacer gratings are used to provide the required
location of the fuel rods in the cross section of the fuel assemblies and are mounted in the central tube. The fastening of the spacer grids allows them to move along the axis at a distance of 3.5 m with thermal expansion of the fuel rods. The outermost spacer grid is attached to a dowel to increase rigidity against bundle twisting.
The spacer grid is a honeycomb structure and is assembled from a central, intermediate pole, twelve peripheral cells and a rim, interconnected by spot contact welding. The rim has spacer protrusions.
Rice. 2.31. TVS RBMK-1000:
1 - suspension; 2 - adapter; 3 - shank; 4 - fuel rod; 5 - bearing rod; 6 - bushing; 7 - tip; 8 - nut
The central tube of the fuel assembly has a rectangular half-diameter cut at the end for joining the fuel assemblies with each other in the channel. This ensures the necessary coaxiality of the fuel rods of the two fuel assemblies and excludes their rotation relative to each other.
The fuel rods are rigidly fixed in the end grids of the fuel assemblies (at the upper and lower boundaries of the core), and when the reactor is operating, the gap in the center of the core is selected due to thermal expansion. Reducing the distance between the fuel rods in the center of the core reduces the burst of heat release and lowers the temperature of the fuel and structural material in the area of the fuel rod plugs. The use of two fuel assemblies along the height of the core allows each assembly to operate in the zone of both maximum and minimum energy release in height.
All parts of the fuel assemblies, except for the rod and spacer grids, are made of zirconium alloy. The rod, which serves to connect the assembly with the suspension, and the spacer grids are made of Kh18N10T stainless steel.
Analysis of thermal-hydraulic and strength characteristics of the RBMK-YUOO reactor revealed the available reserves for increasing the power of the installation. An increase in the critical power of the technological channel, i.e., the power at which a heat transfer crisis occurs on the surface of the fuel elements, accompanied by an unacceptable increase in the temperature of the zirconium cladding, was achieved by introducing heat transfer intensifiers into the fuel assembly. The use of intensifier grids with axial swirling of the coolant flow made it possible to increase the capacity of the RBMK-1000 process channel by 1.5 times. The design of the RBMK-1500 fuel assemblies differs from the design of the RBMK-1000 fuel assemblies in that spacer intensifier grids are used in the upper fuel assemblies, otherwise the fuel assem- bly design has no fundamental differences. Maintaining the resistance of the circulation circuit is achieved by reducing the flow rate of the coolant.
An increase in the power of fuel assemblies causes a corresponding increase in the linear power of fuel rods up to 550 W/cm. Patriotic and overseas experience shows that this level of linear power is not the limit. At a number of US stations, the maximum linear power is 570-610 W/cm.
For installation and replacement of the technological channel body during operation, as well as for organizing a reliable heat sink for graphite masonry to the channel, there are “solid contact” rings on its middle part (Fig. 2.32). Split rings 20 mm high are placed along the height of the channel close to each other in such a way that each adjacent ring has reliable contact along the cylindrical surface either with the channel pipe or with inner surface graphite masonry block, as well as at the end between them. The minimum allowable gaps channel-ring and ring-block are determined from the condition of inadmissibility of channel jamming in the masonry as a result of radiation shrinkage of graphite and an increase in the channel diameter as a result
creep of the pipe material. A slight increase in gaps will lead to a deterioration in heat removal from the graphite masonry. Several bushings are welded on the upper part of the channel body, designed to improve heat removal from the metal structures of the reactor to ensure radiation safety and create technological bases in the manufacture of the channel body.
Rice. 2.32. Installation of a technological channel in a graphite masonry:
1- pipe (alloy Zr + 2.5% Nb); 2 - outer graphite ring; 3 - inner graphite ring; 4 - graphite masonry
As already noted, zirconium alloys are used mainly for the manufacture of elements of the reactor core, in which their specific properties are fully used: neutron
"transparency", heat resistance, corrosion and radiation resistance, etc. For the manufacture of other parts of the reactor, a cheaper material is used - stainless steel. The combination of these materials is determined by design requirements as well as economic considerations in terms of materials and technology. The difference in physical, mechanical and technological properties of zirconium alloys and steels causes the problem of their connection.
Combinations of steel with zirconium alloys are known in industrial reactors. mechanically, for example, in the Canadian Pickering-2, -3 and -4 reactors, the connection of channel pipes made of zirconium alloy with end fittings made of tempered stainless steel (Fig. 2.33) was carried out using rolling. However, such compounds work satisfactorily at a temperature of 200-250 °C. Abroad, the joints of steel with zirconium were studied by fusion welding (argon-arc) and welding in the solid phase. Argon-arc welding is carried out at higher temperatures than solid phase welding, which leads to the formation of brittle intermetallic interlayers in the joint zone, which adversely affect the mechanical and corrosion properties of the weld. Among the studied methods for joining zirconium alloys with steel in the solid phase are explosion welding, joint forging, stamping, pressure welding, joint pressing, contact-jet brazing, friction welding, etc.
However, all these connections are inapplicable for pipes of the technological channel of the RBMK reactor, since they are all intended
to work with other parameters, and they cannot provide the necessary density and strength.
The middle zirconium part of the RBMK channel, located in the reactor core, is connected to the stainless steel end assemblies using special steel-zirconium adapters. Adapters steel - zirconium are obtained by diffusion welding.
Welding is carried out in a vacuum chamber as a result of strong pressing to each other of parts heated to a high temperature from zirconium alloy and stainless steel. After machining an adapter is obtained, one end of which is zirconium alloy, the other is stainless steel. To reduce the stresses arising in a joint with a large difference in the coefficients of linear expansion of the zirconium alloy (a = 5.6 * 10 -6 1 / ° C) and steel 0Kh18N10T (a = 17.2 * 10 -6 1 / ° C), a bandage of bimetallic hot-pressed pipes is used (steel grade 0X18H10T + steel grade 1X17H2) (a=11*10 -6 1/°C).
The connection of the adapter with a zirconium tube with an outer diameter of 88 and a wall thickness of 4 mm is carried out by electron beam welding. Welds are subject to the same requirements for strength and corrosion properties as for the main pipe. The developed modes of electron-beam welding, methods and modes of mechanical and thermal treatment of welds and near-weld zones made it possible to obtain reliable vacuum-tight steel-zirconium welded joints.
Scientific supervisor of the project: IAE im. I. V. Kurchatova , Academician Alexandrov A. P.
General Designer (LNPP): GSPI-11 (VNIPIET), Gutov A.I.
Chief designer of the turbine plant: KhTGZ, "Turboatom", Yu. F. Kosyak
Metal construction developer: TsNIIPSK, Melnikov N. P.
Leading materials science organization: "Prometheus", Kopyrin G.I.
Designer and manufacturer of CPS electromechanical equipment, CTO: Design Bureau of the Bolshevik plant, Klaas Yu. G.
At the moment, the series of these reactors includes three generations. The head reactor of the series is the 1st and 2nd units of the Leningrad NPP.
Encyclopedic YouTube
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✪ Power nuclear reactors
✪ Dismantling of TC and CPS channels
✪ The very first RBMK: the legend is leaving
✪ Installation of the multiple forced circulation circuit of the RBMK-1000 reactor
✪ NNPP Decommissioning of the 1st power unit
Subtitles
History of creation and operation
The reactor of the world's first nuclear power plant (AM-1 ("Atom Mirny"), Obninsk NPP, 1954) was precisely a uranium-graphite channel reactor with a water coolant. The development of uranium-graphite reactor technologies was carried out at industrial reactors, including “dual” purpose reactors (dual-purpose reactors), which, in addition to “military” isotopes, produced electricity and used heat to heat nearby cities.
Industrial reactors that were built in the USSR: A (1948), AI (PO Mayak in Ozersk), AD reactors (1958), ADE-1 (1961) and ADE-2 (1964) (Mining and chemical plant in Zheleznogorsk), reactors I-1 (1955), EI-2 (1958), ADE-3, ADE-4 (1964) and ADE-5 (1965) ( Siberian chemical plant in Seversk).
The development of the RBMK reactors proper began in the mid-1960s and relied, to a large extent, on extensive and successful experience in the design and construction of industrial uranium-graphite reactors. The main advantages of the reactor plant were seen by the creators in:
- maximum application of the experience of uranium-graphite reactors;
- well-established links between factories, well-established production of basic equipment;
- the state of industry and the construction industry of the USSR;
- promising neutronic characteristics (low fuel enrichment).
In general, the design features of the reactor repeated the experience of previous uranium-graphite reactors. The fuel channel became new, assemblies of fuel elements from new structural materials - zirconium alloys, and with a new form of fuel - metallic uranium was replaced by its dioxide, as well as coolant parameters. The reactor was originally designed as a single-purpose reactor - for the production of electrical and thermal energy.
Work on the project began at the IAE (RRC KI) and NII-8 (NIKIET) in 1964. In 1965, the project was named B-190, and its design was entrusted to the design bureau of the Bolshevik plant. In 1966, by decision of the ministerial NTS, work on the project was entrusted to NII-8 (NIKIET), led by Dollezhal.
During the construction of the first nuclear power plants in the USSR, there was an opinion that a nuclear power plant is a reliable source of energy, and possible failures and accidents are unlikely or even hypothetical events. In addition, the first blocks were built within the system of medium mechanical engineering and were supposed to be operated by organizations of this ministry. Safety regulations at the time of development either did not exist or were imperfect. For this reason, the first power reactors of the RBMK-1000 and VVER-440 series did not have a sufficient number of safety systems, which required further serious modernization of such power units. In particular, in the initial design of the first two RBMK-1000 units of the Leningrad NPP, there were no hydrocylinders of the emergency reactor cooling system (ECCS), the number of emergency pumps was insufficient, there were no check valves (OK) on the distributing-group headers (RGK), etc. In the future , in the course of modernization, all these shortcomings were eliminated.
Further construction of RBMK blocks was supposed to be carried out for the needs of the Ministry of Energy and Electrification of the USSR. Taking into account the less experience of the Ministry of Energy with nuclear power plants, significant changes were made to the project that increase the safety of power units. In addition, changes were made to take into account the experience of the first RBMKs. Among other things, ECCS hydraulic cylinders were used, 5 pumps began to perform the function of emergency ECCS electric pumps, check valves were used in the RGK, and other improvements were made. According to these projects, power units 1, 2 of the Kursk NPP and 1, 2 of the Chernobyl NPP were built. At this stage, the construction of RBMK-1000 power units of the first generation (6 power units) was completed.
Further improvement of NPPs with RBMK began with the development of projects for the second stage of the Leningrad NPP (power units 3, 4). The main reason for finalizing the project was the tightening of security rules. In particular, a system of balloon ECCS, ECCS of long-term cooldown, represented by 4 emergency pumps, was introduced. The accident localization system was represented not by a bubbler tank, as before, but by an accident localization tower capable of accumulating and effectively preventing the release of radioactivity in case of accidents with damage to the reactor pipelines. Other changes have been made. The main feature of the third and fourth power units of the Leningrad NPP was the technical solution for the location of the RGC at an altitude higher than the altitude of the active zone. This made it possible to have a guaranteed filling of the core with water in the event of an emergency water supply to the RGC. Subsequently, this decision was not applied.
After the construction of power units 3, 4 of the Leningrad NPP, which is under the jurisdiction of the Ministry of Medium Machine Building, the design of RBMK-1000 reactors for the needs of the USSR Ministry of Energy began. As noted above, when developing a nuclear power plant for the Ministry of Energy, additional changes were made to the project, designed to increase the reliability and safety of nuclear power plants, as well as increase its economic potential. In particular, when finalizing the second stages of the RBMK, a drum-separator (BS) of a larger diameter was used (the inner diameter was increased to 2.6 m), a three-channel ECCS system was introduced, the first two channels of which were supplied with water from hydraulic cylinders, the third - from feed pumps. The number of pumps for emergency water supply to the reactor was increased to 9 units and other changes were made that significantly increased the safety of the power unit (the level of execution of the SAOR met the documents in force at the time of designing the NPP. The capabilities of the accident localization system, which was designed to counteract an accident caused by a guillotine rupture, were significantly increased pipeline of maximum diameter (pressure collector of the main circulation pumps (MCP) Du 900. Instead of bubble tanks of the first stages of the RBMK and localization towers of Units 3 and 4 of the Leningrad NPP, two-story localization pools were used at the RBMK of the second generation of the Ministry of Energy, which significantly increased the capabilities of the localization system accidents (SLA). the density of the premises in case of rupture of the equipment located in it (up to the pressure manifold of the MCP DN 900 mm). PPB was not covered by BS and steam-water communications. Also, during the construction of the NPP, the reactor compartments were built in a double block, which means that the reactors of the two power units are essentially in the same building (unlike previous NPPs with RBMK, in which each reactor was in a separate building). So the RBMK-1000 reactors of the second generation were made: power units 3 and 4 of the Kursk NPP, 3 and 4 of the Chernobyl NPP, 1 and 2 of the Smolensk NPP (together, together with the 3 and 4 unit of the Leningrad NPP, 8 power units).
A total of 17 power units with RBMK were put into operation. The payback period for serial blocks of the second generation was 4-5 years.
The contribution of NPPs with RBMK reactors to the total electricity generation by all NPPs in Russia is about 50%.
Characteristics of RBMK
| Characteristic | RBMK-1000 | RBMK-1500 | RBMKP-2400 (project) |
MKER-1500 (project) |
|---|---|---|---|---|
| Thermal power of the reactor, MW | 3200 | 4800 | 5400 | 4250 |
| Electric power of the unit, MW | 1000 | 1500 | 2000 | 1500 |
| Unit efficiency, % | 31,3 | 31,3 | 37,0 | 35,2 |
| Steam pressure in front of the turbine, atm | 65 | 65 | 65 | 65? |
| Steam temperature in front of the turbine, °C | 280 | 280 | 450 | |
| Active zone dimensions, m: | ||||
| - height | 7 | 7 | 7,05 | 7 |
| - diameter (width×length) | 11,8 | 11,8 | 7.05×25.38 | 14 |
| Loading uranium, t | 192 | 189 | 220 | |
| Enrichment, % 235 U | ||||
| - evaporation channel | 2,6-3,0 | 2,6-2,8 | 1,8 | 2-3,2 |
| - overheating channel | - | - | 2,2 | - |
| Number of channels: | ||||
| - evaporative | 1693-1661 | 1661 | 1920 | 1824 |
| - overheating | - | - | 960 | - |
| Average burnup, MW day/kg: | ||||
| - in the evaporation channel | 22,5 | 25,4 | 20,2 | 30-45 |
| - in the overheating channel | - | - | 18,9 | - |
| Fuel cladding dimensions (diameter×thickness), mm: | ||||
| - evaporation channel | 13.5×0.9 | 13.5×0.9 | 13.5×0.9 | - |
| - overheating channel | - | - | 10×0.3 | - |
| Fuel cladding material: | ||||
| - evaporation channel | + 2,5 % | + 2,5 % | + 2,5 % | - |
| - overheating channel | - | - | stainless steel steel | - |
Design
One of the goals in the development of the RBMK reactor was to improve the fuel cycle. The solution to this problem is associated with the development of structural materials that weakly absorb neutrons and differ little in their mechanical properties from stainless steel. Reducing the absorption of neutrons in structural materials makes it possible to use cheaper nuclear fuel with low uranium enrichment (according to the original project - 1.8%). Later, the degree of uranium enrichment was increased.
RBMK-1000
Each fuel channel has a cassette made up of two fuel assemblies(TVS) - lower and upper. Each assembly includes 18 fuel rods. The fuel element cladding is filled with uranium dioxide pellets. According to the original design, the uranium-235 enrichment was 1.8%, but, as experience gained in operating the RBMK, it turned out to be advisable to increase the enrichment. The increase in enrichment, combined with the use of a burnable poison in the fuel, made it possible to increase the controllability of the reactor, improve safety and improve its economic performance. At present, a transition has been made to fuel with an enrichment of 2.8%.
The RBMK reactor operates according to a single-loop scheme. The coolant is circulated in a multiple forced circulation loop (MPC). In the core, the water cooling the fuel rods partially evaporates and the resulting steam-water mixture enters the separator drums. Separation of steam takes place in the drum-separators, which enters the turbine unit. The remaining water is mixed with feed water and is fed into the reactor core with the help of the main circulation pumps (MCP). The separated saturated steam (temperature ~284 °C) under a pressure of 70-65 kgf/cm 2 is supplied to two turbogenerators with an electric power of 500 MW each. The exhaust steam is condensed, after which, after passing through regenerative heaters and a deaerator, it is fed to the KMPC using feed pumps (FPUs).
RBMK-1000 reactors are installed at the Leningrad NPP, Kursk NPP, Chernobyl NPP, Smolensk NPP.
Chernobyl accident
RBMK-1500
In RBMK-1500, the power was increased by increasing the specific energy intensity of the core by increasing the power of the FC by 1.5 times while maintaining its design. This is achieved by intensifying the heat removal from the fuel rods by using special heat transfer intensifiers (turbulators) in the TVC in the upper part of both fuel assemblies. All together, this allows you to save the previous dimensions and general design reactor.
During operation, it turned out that due to the high unevenness of energy release, periodically occurring increased (peak) powers in individual channels lead to cracking of the fuel cladding. For this reason, the power was reduced to 1300 MW.
These reactors were installed at the Ignalina NPP (), and were planned for installation according to the original design of the Kostroma NPP.
RBMK-2000, RBMK-3600, RBMKP-2400, RBMKP-4800, (former projects)
By virtue of common feature The design of RBMK reactors, in which the core, like cubes, was recruited from a large number of elements of the same type, the idea of further increasing the power suggested itself.
RBMK-2000, RBMK-3600
In project RBMK-2000 the increase in power was planned due to an increase in the diameter of the fuel channel, the number of fuel rods in the cassette and the pitch of the FC tube sheet. At the same time, the reactor itself remained in the same dimensions.
RBMK-3600 was only a concept project, oh its design features little is known. Probably, the issue of increasing the specific power in it was solved, like the RBMK-1500, by intensifying the heat removal, without changing the design of its RBMK-2000 base - and, therefore, without increasing the core.
RBMKP-2400, RBMKP-4800
They differ from all RBMKs in the core in the form of a rectangular parallelepiped and the presence of stainless steel overheating channels. The steam temperature in RBMKP-2400 and RBMKP-4800 is 450 degrees Celsius [ ] .
MKER (modern projects)
Expected efficiency - 35.2%, service life 50 years, enrichment 2.4%.
Advantages
Operational practice
The accident of 1982, according to the internal analysis of the chief designer (NIKIET), was related to the activities operational staff who grossly violated technological regulations.
| power unit | Reactor type | State | Power (MW) |
generating power (MW) |
|---|---|---|---|---|
| RBMK-1000 | stopped in 1996 | 1000 | ||
| RBMK-1000 | stopped in 1991 | 1000 | ||
| RBMK-1000 | stopped in 2000 | 1000 | ||
| RBMK-1000 | destroyed by an accident in 1986 | 1000 | ||
| RBMK-1000 | construction stopped in 1987 | 1000 | ||
| RBMK-1000 | construction stopped in 1987 | 1000 | ||
| RBMK-1500 | stopped in 2004 | 1300 | ||
Ignalina-2 |
RBMK-1500 | stopped in 2009 | 1300 | |
Ignalina-3 |
RBMK-1500 | construction stopped in 1988 | 1500 | |
Ignalina-4 |
RBMK-1500 | project canceled in 1988 | 1500 | |
| RBMK-1500 | construction stopped in 1990 | 1500 | ||
Kostroma-2 |
RBMK-1500 | construction stopped in 1990 | 1500 | |
| RBMK-1000 | active | 1000 | ||
| RBMK-1000 | active | 1000 | ||
| RBMK-1000 | active | 1000 | ||
| RBMK-1000 | active | 1000 | ||
| RBMK-1000 | construction stopped in 2012 | 1000 | ||
| RBMK-1000 | construction stopped in 1993 | 1000 | ||
| RBMK-1000 | active | 1000 | ||
Leningrad-2 |
RBMK-1000 | active | 1000 | |
Leningrad-3 |
RBMK-1000 | active | 1000 | |
Leningrad-4 |
RBMK-1000 | active | 1000 | |
| RBMK-1000 | active | 1000 | ||
Smolensk-2 |
RBMK-1000 | active | 1000 | |
As a fuel element in the RBMK-1000 reactor, a zirconium tube with a diameter of 13.9 mm, a wall thickness of 0.9 mm and a length of about 3.5 m, closed at both ends, is used, filled with fuel pellets with a diameter of 11.5 mm and a height of 15 mm. To reduce the amount of thermal expansion of the fuel column, the tablets have holes. The initial medium under the shell is filled with helium at a pressure of 5 kgf/cm2. The fuel column is fixed by a spring. The maximum temperature in the center of the fuel pellet can reach 2100ºС. In reality, this temperature is not higher than 1600ºС, the helium pressure is up to 17 kgf/cm 2 , and the temperature of the outer surface of the TVEL cladding is about 300°С.
Fuel elements (fuel rods) are assembled into fuel assemblies (FA) of 18 pieces each; 6 pieces around a circle with a diameter of 32 mm and 12 pieces with a diameter of 62 mm. In the center is a supporting rod (see Fig. 2.14, section B-B). The fuel rods in the assembly are fastened every half meter with special spacer grids.
The main fuel block of the reactor is a fuel (or working) cassette, it consists of two fuel assemblies connected by a common carrier rod, a rod, a tip and a tail. Thus, the part of the cassette located in the active zone has a length of about 7 m.
The cassettes are washed with water, while there is no direct contact of the fuel with the coolant during the normal operation of the reactor.
To obtain an acceptable efficiency of a nuclear power plant, it is necessary to have as many high temperature and the pressure of the steam generated by the reactor. Therefore, a housing must be provided to hold the coolant at these parameters. Such a vessel is the main structural element of VVER-type reactors. For RBMK reactors, the role of the vessel is played by a large number of durable pipelines, inside which the cassettes are placed. Such a pipeline is called a technological channel (TC), within the core it is zirconium and has a diameter of 88 mm with a wall thickness of 4 mm, in RBMK-1000 there are 1661 technological channels.
Rice. 1.14. Fuel assembly of the RBMK reactor
The technological channel (see Fig. 1.13) is designed to accommodate fuel assemblies and organize the coolant flow.
The channel body is a welded structure consisting of middle and end parts. middle part The channel is made of zirconium alloy, end caps are made of stainless steel. They are interconnected by steel-zirconium adapters. The channel body is designed for 23 years of trouble-free operation, however, if necessary, a defective channel body can be removed from the shutdown reactor and a new one installed in its place.
The fuel cassette is installed inside the channel on a hanger, which keeps it in the core and allows using REM to replace the spent cassette without shutting down the reactor. The suspension is equipped with a stopper that seals the channel.
In addition, the reactor has control and protection channels. They contain absorber rods, energy release control sensors. Placement of control channels in columns of graphite masonry is autonomous from technological channels.
The space between the graphite and the channels is filled with a gas that has good thermal conductivity, low heat capacity and does not significantly affect the course of the chain reaction. From this point of view, helium is the best gas. However, due to its high resistance, it is used not in its pure form, but in a mixture with nitrogen (at a nominal power level of 80% helium and 20% nitrogen, at a lower nitrogen power there is more, at 50% nominal it may already be pure nitrogen).
At the same time contact of graphite with oxygen is prevented, i.e. its oxidation. The nitrogen-helium mixture in the graphite stack is blown from the bottom up, this is done to achieve the third goal - to control the integrity of the technological channels. Indeed, when the TC leaks, the humidity of the gas at the outlets from the masonry and its temperature increase.
To improve heat transfer from graphite to the channel, a kind of labyrinth is created during the movement of gas (see Fig. 1.15). Split graphite rings 20 mm high each are alternately put on the channel and holes of the blocks in a section of 5.35 m in the center of the core. Thus, the gas moves according to the scheme: graphite - ring cut - channel wall - ring cut - graphite.
