RU2577783C1 - Process channel combined for industrial nuclear plant - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: nuclear reactor channel contains a pipe, fuel elements and neutron absorbers. The channel has second pipe inside the first pipe. Between the pipes the fuel assemblies are arranged, and in internal pipe the device for neutron absorber installation is located. At that the external pipe and the device for neutron absorber installation have bottom tips, on which respectively fuel assembly and neutron absorber rest being spring loaded, and the device for neutron absorber installation in top part by means of quick-release clamp is connected with rod with sealing assembly with channel external pipe.

EFFECT: possibility of isotope unit reloading without the reactor power decreasing, reduced total number of channels and their reloading time.

3 cl, 2 dwg

Description

The invention relates to nuclear energy and relates to the design of a technological combined channel (CTC) designed for the joint placement of fuel elements (fuel elements) and absorbing elements (pellets) in the reactor core (a.z.), and can be used in the development of new industrial projects reactors for generating electricity and producing isotopes.

There are known channels intended for separate placement in the active zone of a nuclear reactor of fuel assemblies (FA) and absorbing units - BP (see, for example, channels for nuclear reactors such as RBMK, PUGR, TVR - auth. Dollezhal N. A., Emelyanov I .A. Channel nuclear power reactor. M: Atomizdat, 1980, 208 pp.) The channels are each installed in its own cell in the body of the nuclear reactor, passing through the reactor cover, spacer plates and are sealed on top (in the reactor cover) with a gasket. It is possible to overload the loading located in the channels - fuel assemblies (fuel assemblies) or absorbers, separately from the channel or together with it. In this case, the absorber from the channels can be overloaded at power (nominal or reduced, depending on the physical weight of the absorber and the level of energy release in it).

The disadvantages of this design are:

1. Separate placement of fuel and absorbent blocks, leading to an increase in the total number of channels, thereby reducing the strength of the plates of the reactor core (top cover, throttle, etc.).

2. Many of the isotopes produced in the reactor must stand for a long time (several campaigns) and at the same time, to maintain reactivity, change to a lighter absorber (isotopic blocks), i.e. rearranged during the campaign. This also applies to isotopic blocks with a short exposure time (shorter or multiple times the campaign). The rearrangement process has a significant effect on the energy release fields and requires operator intervention in aligning these fields or reducing the reactor power to ensure that the permissible operating parameters are not exceeded.

A device for creating radioisotopes in the tool tubes of existing commercial nuclear reactors is known. Radiation targets can be inserted and removed from the instrument tubes during operation and converted to radioisotopes. Radioisotopes have various medical applications, due to their ability to emit discrete amounts and types of ionizing radiation (see, for example, the description of the invention to Russian patent 2501107 C2, application No. 2009106154/07, claimed 02.20.2009, published: 10.12.2013, Bull. No. 34).

Short-lived radioisotopes (half-life of 75 days or less) are traditionally created by bombarding stable parent isotopes in accelerators or low-power reactors with neutrons at the operating site in medical facilities or near industrial enterprises.

The accumulated short-lived radioisotopes can be relatively quickly and easily collected by removing radiation targets from the instrument tube and the reactor containment, without stopping the reactor or the need for chemical separation processes. Short-lived radioisotopes can then be immediately transported to medical facilities for use.

The disadvantages of this design are:

1. Low productivity in isotopes due to the low power of reactors and the small volume of tool tubes.

2. The main purpose of these isotopes is medicine, ie the facility should be located next to the medical center, since the half-life of these isotopes is short - days, hours.

Another invention is known related to nuclear technology, in particular to the production of radioactive isotopes for the manufacture of radiopharmaceuticals by irradiating targets in a nuclear reactor (see the description of the invention to Russian patent 2476941 C2, application: 2010144805/07, filed 01.11.2010, published: 10.05. 2012, Bull. No. 13).

The target for producing the Mo ⁹⁹ isotope contains fissile material and has the form of an open cylinder. The target is made of a sheet with a thickness of not more than 1 mm. Metallic uranium enriched in the U ²³⁵ isotope of at least 20% was used as fissile target material. Nickel is introduced into the target material, and a composition is formed in which the mass of uranium is 1.0-30.0% by weight of nickel. The invention will simplify the manufacturing processes of the target, its extraction and allocation of accumulated Mo ⁹⁹ .

The execution of the target in the form of an open cylinder reduces the level of thermal stresses in it during irradiation, reducing the likelihood of its deformation and jamming in the block.

The disadvantages of this design are:

1. This target can only be used to generate the Mo ⁹⁹ radioisotope _.

2. Only metal uranium enriched in the U ²³⁵ isotope of at least 20% can be used as fissile target material, and nickel is introduced into the target material as a binder and shape-forming matrix.

Known is the directing channel of the fuel assembly of a nuclear reactor with a burnable absorber located in the cells of the spacer grids (see, for example, the description of the invention to Russian patent No. 2512472 C1, application No. 2012158072/07, filed December 29, 2012, published April 10, 2014, Bull. No. 10). To eliminate the burst of energy release in the fuel rods located next to the guide channel, a layer of a burnable absorber containing the boron-10 isotope in an amount that burns out in no more than one irradiation cycle of the fuel assembly is applied on a part of the surface of the guide channel. The boron-10 isotope can be part of the material from which the guide channel is made.

The absorber on the surface of the guide channel shields thermal neutrons, the excess generation of which in the water cavity and causes an increase in energy release in adjacent fuel rods.

The technical result consists in increasing the power of the reactor installation.

The disadvantages of this design are:

1. The impossibility of producing isotope products.

2. The absorber is a part of channel pipes (on the surface or as a component of pipe material) and cannot be changed during the campaign.

3. The absorber is used only to exclude or significantly reduce the surge of energy in the fuel rods located next to the guide channel.

4. The absorber is also used to maintain reactivity as the fuel and the absorber itself burn out. Their ratio is determined by physical calculation before loading a.z.

The closest in design to the proposed technical solution is the design: FUEL RODS WITH END PARTS AS IRRADIATED TARGETS (see the description of the invention to Russian patent 2479052 C2, application No. 2008149969/07, filed December 17, 2008, published: April 10, 2013).

The claimed solution relates to devices for producing radioactive isotopes in nuclear reactors. The fuel rod has end parts at each end containing irradiated targets. The end parts may contain materials that, when irradiated with a neutron flux arising at the location of the end parts, are converted to the desired isotopes. The end parts may be made of these materials (at least cobalt-59 and iridium-191) or, alternatively, coated with these materials. EFFECT: operation of a fuel rod at the same time both for generating energy and for producing desired radioactive isotopes.

Fuel rods may contain standard components, including nuclear fuel, and be suitable for use in an existing nuclear reactor. The end pieces are made of selected target material or may be hollow and contain target material. Fuel rods can thus produce the various desired isotopes in their end parts with the irradiated target, while simultaneously functioning as conventional fuel rods providing energy for the core of a nuclear reactor.

The disadvantages of this design are:

1. The need to synchronize the time of irradiation of target materials with a fuel campaign, as well as the difficulty of extracting the accumulated target isotopes.

2. End parts with materials (targets) are not located in the optimal area of the AC with a smaller neutron flux and, therefore, the amount of produced material (isotope) is small.

3. The nomenclature of isotopes produced in a reactor is small (mainly cobalt-59 and iridium-191) with low specific activity. Other isotopes require different levels of neutron fluxes (higher and more powerful) and their wider spectrum.

The technical result of the invention consists in the possibility of overloading the isotopic (BI) block without reducing (or, if necessary, some lowering) the reactor power, thereby ensuring continuous operation of the reactor during the campaign and maintaining a high coefficient of power utilization of the reactor installation (KIM RU). In addition, KTS allows you to evenly on a.z. distribute the fuel and the absorber, providing lower coefficients of neutron flux non-uniformity both in radius and in the height of the a.z., reduce the total number of channels and the time for their overload, increase the lattice spacing and, thereby, the strength of the reactor cover, thereby reducing this its thickness and cost, simplifying the technology of its manufacture.

The specified technical result is achieved by the fact that in the channel of a nuclear reactor containing a pipe, fuel elements and neutron absorbing units, the channel is equipped with a second pipe located inside the first, fuel assemblies consisting of at least one fuel element are placed between the pipes, an inner tube has a device for accommodating at least one neutron absorbing unit, while the outer tube and a device for accommodating a neutron absorbing unit are provided with lower onets, on which, respectively, the fuel assembly and the neutron block absorber are supported, preloaded by springs, and the device for placing the neutron block absorber in the upper part is connected via a quick-release grip to the rod, which contains a seal assembly with an outer channel pipe.

There is an option in which separate openings are made in the tip of the outer pipe of the channel for the heat carrier flow, which is used to cool the fuel assembly and to cool the neutron-absorbing block, with passage sections proportional to the energy released in the heat-generating assembly and the absorbent block.

There is also an option in which the device for accommodating the neutron absorbing unit is made in the form of a skewer, on which the neutron absorbing unit in the form of a sleeve is mounted on the outside.

In FIG. 1 shows a general view of the technological channel combined for an industrial nuclear installation (upper part).

In FIG. 2 shows a general view of the technological channel combined for an industrial nuclear installation (lower part).

The technological combined channel (CCC) (Fig. 1, Fig. 2) for an industrial nuclear power plant includes fuel 1 (FA) and isotopic 2 (BI) parts. In this case, the isotopic part 2 is located inside the fuel part 1 and can be reloaded both on the working and on the stopped reactor, the fuel part 1 of the channels - only on the stopped reactor together with the isotopic part of the channel. At the same time, a nuclear power plant can be industrial (produce only isotopic products), and achieve high heat transfer parameters (temperature and pressure) in order to generate electricity and heat.

The channel is attached and sealed in the reactor lid. The design and materials of the channel ensure minimal neutron capture, the possibility of reuse of individual elements, and the maximum degree of unification.

The design of the channel prevents the spontaneous movement of the components of the active zone loaded into it: fuel assembly (FA) 1, isotope block (BI), absorber block (BP) 2, and provides compensation for the temperature expansion of the channel components and loading column, as well as manufacturing tolerances channel details. For this, two springs are used, which pressurize the channel loading (fuel assemblies and BI or BP) - one 3 through the pressure pipe 4 of the fuel assembly 1 column, the second 5 through the push sleeve 6 - BI (BP) column 2. The pressure drop across the fuel assembly is significantly greater than BI (BP), and the force of the spring 3 is also greater, respectively, so the spring for the fuel assembly is made of steel wire (rolled), the spring 5 for the BI (BP) is made of aluminum. To reduce the neutron fluence to the springs and increase their service life, the spring of steel 3 is moved outside the core, of aluminum 5 is placed just above the a.z.

The outer sheath tube 7 is connected by a collet 8 with an extension 9. The collet 8 is fixed against compression by the pressure tube 4. To disengage the outer sheath tube 7 with an extension 9, it is necessary to remove the pressure tube 4 from the channel, which will allow the collet 8 to compress and exit the groove 10 inside the throttle 11 .

In the lower part of the extension cord 9, openings 12 are provided for the coolant to exit from the channel into the drain cavity.

The fuel assemblies 1 are loaded into the jacketed outer pipe 7. Inside the fuel assemblies 1, a skewer 13 is mounted, which is mounted on the rod 14, which is attached and sealed in the upper part of the channel extension 9. The skewer 13 is made of a pipe (or rod) 15, the lower part of which is connected to the tip 16, centered in the tip 17 of the outer sheath pipe 7, and the upper part to the tip 18 for connection with the rod 14. BI (BP) 2 is installed on the skewer 13 The skewer 13 is connected to the rod 14 by a quick-disconnect connection - a collet 19 and a sleeve 20, which, under the action of the spring 5, compresses the collet 19, preventing it from opening. After removing the rod 14 and the skew 13 from the channel, their disengagement is carried out by moving the sleeve 20 down, compressing the spring 5.

The rod 14 consists of a pipe 21, into which a tube 22 is installed to accommodate the temperature control sensor of the coolant 23 - DKTT, which controls the temperature of the coolant at the outlet of the zones with fuel assemblies and BI (PS). With the help of the bar, the skewer with BI (BP) is unloaded / loaded from the KTS.

Coated outer tube 4 contains a throttle 11 in the upper part and a tip 17 in the lower. The throttle 11 enters the hole of the reactor throttle plate (not shown in the drawings), carrying out the throttling of the coolant from the cavity of the inter-channel space (MCP) into the drain cavity. To effectively reduce the pressure of the coolant when it passes through the gap between the plate and the channel on the outer surface of the throttle 11, annular grooves 24 are made, which create additional resistance during the passage of the coolant. The width, depth and number of these grooves are determined by calculation and their hydraulic resistance is checked at the stand. The tip 17 provides the necessary distribution of the flow rate of the coolant entering the fuel 1 and isotopic 2 parts of the channel. The throttle 11 and tip 17 KTS is centered in the plates of the reactor.

An internal pipe 25 is installed between the fuel assemblies and the BI (BP), designed to separate the flow of coolant, which is used for cooling the fuel assemblies and the BI (BP), respectively. The upper part of the CCC is made of stainless steel to ensure reliable fastening of the channel in the reactor cover, the outer shell 7 and inner pipe 25, the throttle 11 and tip 17, the lower part of the rod 14, spring 5 and skew 13 are made of aluminum alloys. The upper part of the CCC can be used repeatedly until physical wear and tear.

The proposed channel works as follows. After removing the skewer 13 from the channel and transferring it to the holding pool (not shown in the drawings) with a special tool (plug), the sleeve 20 moves down to the stop of the sleeve 20 in the upper tip 18 of the skewer 13, compressing the spring 5. The collet 19 petals enter the inner ring area grooves 26 in the sleeve 20 and under the action of the spring 5 and the upper tip 18 of the skewer 13 are bred, freeing the skewer 13 from engaging with the rod 14. This allows you to work with the skewer 13 separately, installing and removing isotopic blocks on it. The connection of the skewer 13 with the rod 14 occurs in the reverse order. The design of the CCC provides the possibility of using the reloading (MP) machine for the remote unloading / loading of the isotope portion (skewer 13 with rod 14) from the channel when the reactor is operating at power, as well as at the shutdown reactor — unloading / loading of the CCC as a whole or separately: rods with skewer and BI (BP) and fuel part 1 with fuel assemblies.

The fuel part 1 of the CCC with the gaskets 27 and the fastening nut 28 is sealed in the reactor cover, and the isotopic part (rod 14) with the help of the gaskets and fastening nuts 29 is in the fuel. The design of the KTS provides a quick drain of the coolant from the internal cavities of the channel (rod) when it is removed from the reactor during overload. The spacing of the core components (fuel assemblies and BI (PSU) and channel pipes (uniform gap between them for coolant passage) is ensured, which eliminates local deterioration of heat exchange conditions. For spacing, pipes with longitudinal ribs (5-8 pcs.) Are used on the outside or the inner surface or special spacer rings between the component parts (blocks) a.z.

The signal cable (not shown in the drawings) of the thermal converter is connected to the CCC using an electrical connector 30, which, when loading / unloading the channel or its isotopic part, allows you to quickly connect / disconnect the cable from the channel.

Structural materials (aluminum alloys) of the reactor channels, in which the core elements are located, provide the minimum parasitic absorption of thermal neutrons, thereby making it possible to use neutrons more efficiently for producing isotopes, reducing the level of induced activity of structural materials.

The materials used for the manufacture of channel elements are radiation-, corrosion- and erosion-resistant in the conditions of their operation in the reactor. The choice of structural materials is justified and confirmed by the results of calculations and tests, the experience of their operation on other reactors.

The isotopic part of the CCC can be reloaded through the top of the reactor operating at full (or reduced) power by extracting skewers from the canal with isotopic products. To protect against radioactive radiation, it is necessary to use a reloading machine (or container).

The amount of production of radionuclides depends on the power of the reactor, the flux density and spectrum of neutrons and the amount of loaded target substance. All this can be achieved using the CCC. The most suitable type of reactor for achieving these goals is a heavy-water industrial reactor using a CTS, in which it is optimally possible to place both fuel and target material, and to produce almost the entire spectrum of isotopes in the required volume.

Claims (3)

1. The technological channel combined for an industrial nuclear installation, containing a pipe, fuel elements and neutron absorbing blocks, characterized in that the channel is equipped with a second pipe located inside the first, fuel assemblies consisting of at least one fuel element are placed between the pipes , a device for accommodating at least one neutron-absorbing block is installed in the inner tube, while the outer pipe and a device for placing the neutron-absorbing block is provided lower lugs, which are supported, respectively, the fuel assembly and a flow neutron absorber, preloaded by springs, and the device for placing the neutron-absorber unit in the upper part via a quick grip is connected to the pole that contains the seal assembly with the outer duct tube. 2. The channel according to claim 1, characterized in that in the tip of the outer pipe of the channel there are separate openings for the heat carrier flow, which is used to cool the heat-generating assembly and to cool the neutron-absorbing block, with passage sections proportional to the energy released in the heat-generating assembly and the absorbing block . 3. The channel according to claim 1, characterized in that the device for accommodating the neutron absorbing unit is made in the form of a skewer, on which the neutron absorbing unit in the form of a sleeve is mounted on the outside.

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