RU2803192C1 - Horizontal pusher plant for sintering uranium-plutonium fuel pellets - Google Patents

Abstract

FIELD: nuclear energy.

SUBSTANCE: process equipment for the production line of uranium-plutonium fuel pellets. Horizontal pusher plant for sintering uranium-plutonium fuel pellets contains jointly located resistive heating furnaces for removing binder and sintering pellets in a horizontal plane, separated by a gas barrier, including modules for loading and unloading transport containers with boats loaded with fuel pellets, through-flow muffles located in the center of the internal space both ovens, and refrigerator. The muffles of the binder removal and sintering furnaces are installed coaxially to each other and articulated into a single whole, and the transport containers of the boats are made in the form of a pallet on rollers that move along the muffles and are installed between the brackets in oval-shaped holes with a guaranteed clearance.

EFFECT: improving the quality of sintered fuel pellets.

2 cl, 6 dwg

Description

The invention relates to the field of nuclear energy, in particular to technological non-standardized equipment for the production line of uranium-plutonium fuel pellets (SNUP and MOX fuel) and can be used as part of an automated and robotic production complex (PEC), which ensures the production of fuel assemblies for the starting load of BN-reactors 1200 and BR-1200.

BACKGROUND OF THE ART

The process of making nuclear fuel pellets involves forming uranium-plutonium oxide or nitride powders into raw pellets, which are then sintered to the required density. Sintered tablets are subject to fairly stringent requirements for density, microstructure, thermal stability and other parameters, which are ensured by appropriate technological processes using special technological equipment, mainly in the form of gas-filled multi-chamber resistive heating furnaces.

A known installation for sintering SNUP fuel tablets includes a pusher sintering furnace and a chain of sealed boxes that house equipment for weighing the product, changing the gas environment, moving boats with pellets, purifying gases and performing other technological operations.

(V. Smirnov, “Our team is capable of solving large and complex problems” https://www.atomic-energy.ru/interviews/2019/12/13/100034)

There is a known method for producing pelletized fuel for fuel elements (RU 2256245 C2, published July 10, 2005, Bulletin 32), implemented using a tunnel pellet sintering furnace equipped with sections for heating, sintering in a reducing hydrogen environment and cooling by advancing boats with pressed " raw" tablets through oven sections by gradually preparing the tablets for subsequent heat treatment. To do this, a heating section for removing binder components (zinc stearate) is formed from three zones isolated by thermal barriers with a temperature of gradual heating of the tablets, a pre-heating section is additionally formed with the final removal of the binder from two zones isolated by thermal barriers with a higher heating temperature of the tablets, and a tablet sintering section are formed from three high-temperature zones isolated by thermal barriers with a temperature that ensures sintering of the tablets, and in the last zone the tablets are cooled by dropping the temperature.

The known technical solution of the sintering furnace according to the invention RU 2256245 C2 can be taken as the closest analogue (prototype) in terms of the largest number of essential features identical to the claimed invention.

The main disadvantage of the known furnace is due to the technology used for manufacturing tablets and is as follows. Despite the gradual heating of the tablets to ensure clear removal of the binder, sintering of the tablets often begins long before the maximum temperature is reached. In this case, first of all, sintering and compaction of the surface layers of the tablet occurs. The compacted sintered surface layer of the tablet makes it difficult for gaseous products, mainly CO ₂ , to escape, including carbon contained in zinc stearate and carbon introduced with the binder into uranium oxide, which leads to cracking or swelling of the tablets.

To avoid this, it is necessary to carry out the heating process very slowly, over 4-5 hours, keep the tablets in a high-temperature zone for up to 6 hours, and increase the duration of complete removal of zinc to residual zinc to 14 hours. Moreover, the entire tablet production cycle from loading into the oven to unloading from the oven will take 30-35 hours, which lengthens the technological process and generally reduces its productivity.

The tablet manufacturing process can be shortened by using another technology. To do this, it is necessary to remove the binder in a separate furnace, and sinter the tablets in another furnace, carrying out the process of removing the binder and the sintering process by moving boats with tablets along the guides of a common muffle located in the center of the furnaces.

DISCLOSURE OF THE INVENTION

The objective of the claimed invention is to create a new horizontal pusher installation for high-temperature thermal processes of heat treatment and sintering of prepared semi-finished uranium-plutonium nuclear fuel, providing a two-stage heat treatment process in temperature zones with different gas environments.

The technical result is to improve the quality of sintered fuel pellets.

The task set can be implemented, and its technical result can be achieved through a specific technical solution of the invention, which consists in the following:

- a horizontal pusher installation for sintering uranium-plutonium fuel pellets, contains resistive heating furnaces for removing the binder and sintering the pellets, located together in a horizontal plane, separated by a gas barrier;

- the furnaces include modules for loading and unloading transport containers with boats loaded with fuel pellets, pass-through muffles located in the center of the internal space of both furnaces and a refrigerator;

- the muffles of the debinding and sintering furnaces are installed coaxially to each other and articulated into a single whole, and the transport containers of the boats are made in the form of a pallet on rollers, moved along the muffles and installed between the brackets in oval-shaped holes with a guaranteed gap;

- the pallet and brackets are connected to each other by fastening elements, for example, screws, with the possibility of forming a guaranteed gap between the bottom and the boat.

A comparative analysis of the essential features of the claimed invention in comparison with its analogues indicates that from the known level of technology on the date of filing the application it is not known and does not clearly follow for the “average specialist” in this field of technology a device for the same purpose as the claimed invention, in which the entire set of essential features given in the independent claim and disclosed in the description would be applied.

At the same time, the proposed set of essential features is not obvious and ensures that the claimed invention acquires new properties that make it possible to implement the task, which means that it meets the “novelty” criterion.

In general, the design of the claimed invention is technologically advanced, so its production does not present any technical difficulties, which indicates that the invention also meets the “industrial applicability” criterion.

BRIEF DESCRIPTION OF THE DRAWINGS

In fig. Figure 1 shows a general view of the sintering installation;

In fig. 2 shows the loading module;

In fig. Figure 3 shows a general view of the deligament removal oven;

In fig. Figure 4 shows a sectional view of the ligament removal oven;

In fig. Figure 5 shows a sectional view of the sintering furnace;

In fig. Figure 6 shows a shipping container with a boat.

IMPLEMENTATION OF THE INVENTION

A preferred embodiment of the proposed invention is described below with reference to the accompanying drawings.

As can be seen from Fig. 1, the proposed invention of a horizontal pusher installation for sintering uranium-plutonium fuel pellets includes a loading module 1, a binder removal furnace 2 (hereinafter the term “binder removal” is equivalent to the term “binder removal”), a gas barrier 3, a pellet sintering furnace 4, a refrigerator 5 , unloading module 6.

In fig. Figure 2 shows a loading module 1. The module includes a loading chamber 9, a feeding chamber 10 into the muffle of the debinding furnace 2, linear drives of displacement 11, a manipulator 12 and an output gateway 13 with a flange and quick-release clamps for connection to the muffle of the debinding furnace. Linear drives 11 and manipulator 12 have flanges that allow, in the final position, to close the space between chambers 9, 10 and the outlet pipe, sealing the internal cavities from each other.

In fig. Figure 3 shows a general view of the binder removal furnace 2. The furnace includes a heating chamber 14, with a cover 15 and a muffle 20. On the cover 15, heaters 17 are installed on flange pipes, fixed with clamps 16. Heaters 17 are connected to the electrical network through current leads 18. Thermoelectric converters 19 are used to measure the temperature in the furnace and control the heaters 17. The muffle 20 is used to transport the container 21 with a boat loaded with tablets.

In fig. Figure 4 shows a cross-section of the furnace for removing the binder 2 from the sintered product. The furnace is equipped with thermal insulation 23 made of high-temperature plates, with a partition 24 forming two thermal zones: preheating and a zone of heating and holding until the debinding temperature. The muffle 20 has a pipe 22 for removing binder products.

In fig. Figure 5 shows a cross-section of the sintering furnace 4. The section includes a housing 32 with thermal insulation 30 and a water cooling system 31, isolated on both sides by covers 26. The covers 26 are attached to the housing with quick-release clamps 33. Inside the housing 32 there is a pass-through muffle 25 with an exhaust pipe 29, through which the gases of the processed product are removed. The sintering furnace 4 contains heaters 27 flanged to the housing 32. Current leads 28 of the heaters 27 are connected to the water cooling system 31.

In fig. 6 shows a transport container 21 with a boat 35. The transport container 21 includes a pallet 36 mounted on brackets 37 and attached to them with screws 41. Rollers 40 are installed between the brackets 37, allowing the transport container 21 to move along the muffles 20 and 25 of the debinding furnaces 2 and sintering 4. The brackets 37 have holes 38 and projections 39. The projections 39 and rollers 40 partially repeat the shape of the muffles 20 and 25 in which they move. The holes 38 in the brackets 37 are made oval with a guaranteed gap in relation to the axes of the rollers 40.

The transport container 21 with the boat 35 from the external transport corridor enters the loading device, in which, with the help of linear drives 11 and the manipulator 12, it enters the muffle 20 of the binder removal furnace 2, and then through the gas barrier 3 into the sintering furnace and through the refrigerator 5 to the outlet unloading module 6.

Claims (2)

1. Horizontal pusher installation for sintering uranium-plutonium fuel pellets, containing resistive heating furnaces for removing the binder and sintering pellets, located together in a horizontal plane, separated by a gas barrier, including modules for loading and unloading transport containers with boats loaded with fuel pellets, pass-through muffles located along center of the internal space of both furnaces, and a refrigerator, characterized in that the muffles of the debinding and sintering furnaces are installed coaxially to each other and articulated into a single whole, and the transport containers of the boats are made in the form of a pallet on rollers, moved along the muffles and installed between the brackets in the holes of the oval forms with guaranteed clearance. 2. Horizontal pusher sintering installation according to claim 1, characterized in that the tray and brackets are connected to each other by fastening elements, for example screws, with the possibility of forming a guaranteed gap between the bottom and the boat.

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