JPS6246838B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glovebox in which nitrose gases are generated when handling radioactive media, such as nitric acid solutions. This nitrose gas is, for example, a nitrogen oxide such as N ₂ O ₅ , nitric oxide NO and nitrogen dioxide NO ₂ . These gases, especially nitrogen dioxide _NO2 , are highly toxic and corrosive and cause damage to the human lungs and blood in corresponding concentrations. It is therefore necessary to convert such gases, whose generation cannot be prevented, into harmless gases, such as nitrogen and carbon dioxide, by catalytic and chemical reactions. It has therefore already been proposed to carry out a conversion with reducing gases such as hydrogen, methane or other hydrocarbons.

Nitrose gas is also produced when handling radioactive media such as nitric acid solutions of heavy metals such as uranium and plutonium. Since such work can never be carried out in an open room without protective measures, this work is usually carried out in a ventilated ventilation room or so-called glove box. A glovebox is a large, airtight box that is visible from the outside through a glass window, in which manual operations are performed via a glove made of non-breathable material that is hermetically connected to the container wall. The inner chamber of such a glove box is connected to a continuously operating air supply system and an exhaust system, the exhaust air always being drawn off via a filter. This filter may have the purpose of retaining radioactive particles.

When attempting to melt uranium- or plutonium-containing pieces such as nuclear fuel pellet waste,
Particularly when working with nitric acid, nitrose gases are produced which cannot be introduced into the normal exhaust system. The conventional nitrose gas decomposition equipment described above is a large-sized facility that poses the risk of radioactive contamination and, in some cases, the risk of explosion, and therefore should not be used in the cases described above. is very problematic.

Therefore, an object of the present invention is to eliminate nitrose gas generated in a glove box.
In this case, the aim is to make the equipment for this purpose spatially small and to eliminate the risk of radioactive contamination or to be able to carry out decontamination without difficulty.

This purpose, according to the invention, is achieved by providing the glove box with a device for chemically converting the nitrose gas into the corresponding components, which components are led via filters, which are known per se, to the installation of a suitable exhaust system. is solved by draining it as condensate. The conversion device then consists of a cartridge with a perforated end plate and filled with activated carbon, which cartridge is adjusted to a temperature of 600° C. by means of an adjustable heating device and can be exchanged from the inner chamber of the glove box. Due to the large surface of the activated carbon, a large reaction surface is available, so that the total volume of the reaction chamber (ie here the activated carbon cartridge) is very small compared to previously known installations. The activated carbon also acts as a filter, so that any radioactive particles that may be entrained are trapped in it, and replacing the filter simultaneously decontaminates the entire converter.

The present invention will be described in detail below based on embodiments shown in the drawings.

The drawing shows a schematic cross-sectional view of the glove box, in which reference numeral 1 represents the wall of the glove box. Inside the glovebox is a reaction vessel 3 into which, through the illustrated connecting tube, the plutonium-containing substance to be dissolved, for example with nitric acid, is introduced. The dissolution process is facilitated by heating the contents of the reaction vessel 3, for example with a heating coil 31. The generated steam is transferred to reaction vessel 3.
A carrier gas, for example nitrogen, is passed into the condenser 4, which is arranged above and has a cooling coil 41, for example water-cooled, in it. In that case, of course, the nitro gas is not condensed, but is sent to a conversion device 2 arranged above the condenser 4, in which it is converted into nitrogen and carbon monoxide gases. As shown, this device 2 is connected in a gas-tight manner by a flange to the container wall 1 of the glove box. The device 2 also consists of a jacket tube 25 surrounded by a heating device, preferably an electric heating device 26. The jacket tube 25 is filled with activated carbon 22 and has permeable or perforated end plates 23, 2.
There is a cartridge 21 with 4. Perforated end plate 2
3 and 24 prevent the activated carbon from being entrained out or going to the reaction vessel 3. Activated carbon bed 22 is heated to approximately 600° C. by electric heater 26 and placed in a condition to reduce nitrose gas. Therefore, pure nitrogen and mainly carbon monoxide gas are produced in this case. These gases are sent via piping 5 to a burner 51 located inside the glove box. This burner 51 oxidizes carbon monoxide gas to carbon dioxide gas using oxygen present in the glove box 1 via a platinum coil 52 heated to about 800°C. Harmless gases such as nitrogen and carbon dioxide are sent via pipe 54 to exhaust filter 6, and from there via pipe 7 to the exhaust system of the entire facility.
A conical hood 53 that collects flame gas from the burner 51 is water-cooled, and has a discharge gutter and a discharge pipe 55.
is provided. The entrained water vapor is condensed by this auxiliary device and sent to the collection tank 56.
are collected in.

To introduce the size of the conversion device 2, the diameter of the cartridge 21 is, for example, 3 cm, and its length is about 50 cm. In that case, the amount of nitrose gas produced, which depends on the size of the device installed in the glove box 1, determines the size of the converter device. The equipment in the glove box is not limited to those described in the embodiments, but other equipment is also conceivable, in which nitrose gas is generated during its operation and this gas must be removed unconditionally for safety reasons.

In that case, the conversion device 2 is of course made of a corrosion-resistant material, for example austenitic steel. The heating device is tube 25
Although it is designed as a cylindrical jacket pressed over the housing, it can also be made from two parts that can be folded together.

Instead of an electric heater, a gas heater may be provided, or the cartridge 21 itself may be provided with a resistance heater. Regardless of the heating method for the activated carbon filter 22, a thermal insulation is provided around this device 2 in a manner known per se. This thermal insulator is not shown in the drawing for simplicity.

The carbon is consumed by the conversion of the nitrose gas in the activated carbon bed and is led in gaseous form to the burner 51, so that the activated carbon is gradually consumed. In this case, this wear and tear determines when to replace the used cartridge with a new cartridge. This cartridge change process is carried out without difficulty from inside the glove box. In some cases, radioactive contaminants contained within the used cartridge remain within it. The used cartridges are then shielded against the spread of contamination by a plastic jacket, as is often done for other radioactive components, and then transported through a glove box gate (not shown). taken out.

If the conversion device 2 is important for the operation of such a glovebox, it is possible to signal its loading readiness, for example by a signal lamp, after the activated carbon bed has reached a set temperature, and to stop the chemical operation in the glovebox. is suitable for the purpose. Conversely, in the event of a failure in this conversion device 2, it is also expedient to activate the emergency system in order to immediately stop the operation in the glovebox and the associated generation of nitrose gas.

[Brief explanation of the drawing]

The drawing is a schematic cross-sectional view of a glove box according to the invention. DESCRIPTION OF SYMBOLS 1... Glove box, 2... Conversion device, 3... Reaction container, 4... Condenser, 5... Piping, 6... Filter,
7... Exhaust pipe, 21... Cartridge, 22... Activated carbon, 23, 24... Perforated end plate, 26... Heating device,
51... Burner, 52... Platinum coil, 53... Exhaust hood, 54... Piping, 55... Condensate discharge pipe.

Claims (1)

[Scope of Claims] 1. In a glove box in which nitrose gas is generated when handling a radioactive medium such as a nitric acid solution, the nitrose gas may be introduced into a suitable exhaust system through a filter which is known per se. The glove box 1 is filled with activated carbon 22 and has perforated end plates 23, in order to chemically convert it into components that can be discharged as condensate.
A conversion device 2 consisting of a cartridge 21 closed at 24 and equipped with an electric heating device 26 for heating to approximately 600° C. is provided, as well as an auxiliary device connected downstream of the conversion device 2 for oxidizing the carbon monoxide. The outlet side of the converter 2 is connected to a pipe 5 that communicates with a gas burner 51 of the auxiliary device located in the glove box 1, and the gas burner 51 is provided with an ignition coil 52, so that the exhaust gas of the burner 51 is Exhaust filter 6 via cooled exhaust hood 53 with condensate discharge pipe 55 and piping 54
Glove boxes characterized by being guided by. 2. The cartridge 21 of the converter 2 is mounted on the wall of the glove box 1 for exchange from the inner chamber of the glove box 1, and this location is connected during operation to a nitrose gas generating location, such as a reaction vessel 3 or a condenser 4. 2. A glove box according to claim 1, characterized in that: