RU2251166C1 - Internal container of packing set for plutonium dioxide storage and transport - Google Patents

Abstract

FIELD: safety facilities for handling radioactive materials.

SUBSTANCE: proposed internal container designed for long-time storage and transport of high-radioactivity materials such as plutonium dioxide has container body closed with sealed cover and specified-volume charging box placed in this body and provided with its respective cover. Container body has cylindrical passage for charging box that mounts additional internal cover provided with gas filtering device and hermetically installed relative to its surface for axial displacement. External cover of container body is provided with shut-off valve accommodating gas filtering device installed therein between inner space of container and valve seat. Such mechanical design of container enables reducing irreparable loss of plutonium during its long-time storage and transport.

EFFECT: enhanced safety and reliability , enlarged functional capabilities of container.

7 cl, 2 dwg

Description

The invention relates to the field of protective equipment when working with radioactive substances, in particular to devices for long-term storage and transportation of highly radioactive materials, including plutonium dioxide. When handling plutonium dioxide, the main thing is to ensure nuclear safety by strictly restricting the compact mass (or, equivalently, volume) of plutonium dioxide.

During storage of plutonium dioxide occurs:

- heat release during radioactive decay,

- emission of gases as a result of radioactive decay,

- isolation of radiolysis products (mainly decomposition products of water adsorbed on the surface of plutonium dioxide powder).

This material is extremely toxic, chemically active and prone to the formation of aerosols, so work with it is carried out in sealed boxes filled with dry inert gas. The introduction and removal of plutonium dioxide into the boxes is carried out using sealed containers through the appropriate gateway devices. Before removal from the box, the container must be decontaminated.

In the technology for this purpose transport and packaging kits are used to ensure the safety of contents, nuclear and radiation safety, as well as protect against the harmful effects of radioactive substances on the environment and maintenance personnel.

A packaging kit is known according to US patent No. 3531644, which contains an external case with a removable screwable lid, an internal container enclosed in an external case, closed by a removable protective cover, a glass for radioactive material, placed in the specified internal container and having a sealed open part.

This packaging is designed for storage and transportation of radioactive pharmacological agents and is not designed to increase internal pressure and temperature during storage, which prevents its use for long-term storage and transportation of plutonium dioxide. In addition, the packaging is not sufficiently reliable in terms of tightness. When the package is opened, a radioactive release of plutonium dioxide powder particles is possible.

Most of the above requirements could be met by modern packaging kits for storing and transporting plutonium dioxide, consisting of an outer container, a protective layer with an intermediate container and an inner container. The inner container must provide the first stage of plutonium dioxide sealing, preventing unauthorized release of radioactive substances into the environment, and also ensure the safety of loading and unloading plutonium dioxide at workplaces while unconditionally ensuring nuclear safety.

For the prototype of the proposed invention, the inner container of the BNFL 1680 packaging set of the THORP plant, Great Britain, described in the book "Precautions for the disposal of plutonium, technical solutions", Nuclear Energy Agency, was selected. Organization for Economic Co-operation and Development, Moscow, 1998, p. 17. The inner container of the THORP plant consists of a 3-liter plutonium dioxide loading cup equipped with a screw cap placed in a tight-fitting intermediate container, the end of which is sealed with a plug by welding. The intermediate container, in turn, is placed in an outer container provided with a lid, sealed by welding.

The main disadvantage of the prototype is the impossibility of preliminary discharge of possible internal pressure before opening the container for the extraction of plutonium dioxide during routine maintenance or during monitoring of processes occurring during long-term storage. A preliminary gradual depressurization is necessary because with a sharp release of pressure, capture and release of radioactive particles is possible, which leads to contamination of the surrounding space and ventilation systems, and can also lead to irretrievable losses of plutonium dioxide. In this device, it is difficult to control the tightness of the container assembly and the process of changing the atmosphere of the container.

Another disadvantage of the prototype is the tight fit of the glass container for the radioactive substance to the intermediate container, which does not reduce the internal pressure in the container due to free internal volumes. In addition, after opening the inner container of the packaging for routine maintenance or control inspections, reuse of its housing is problematic.

The problem to which this invention is directed is to create an inner container of a packaging kit for long-term storage and transportation of plutonium dioxide, which has increased safety and reliability, taking into account the expansion of its functionality and reduction of irreversible losses of plutonium dioxide due to the elimination of the release of radioactive particles.

To solve this problem, the inner container of the packaging set for storage and transportation of plutonium dioxide consists of a container body with a tight external container lid and placed inside it, equipped with a cover of a loading cup of normalized volume, and a cylindrical hole is made in the container body into which it is sealed relative to it surface and with the possibility of axial displacement installed inner lid of the container, equipped with devices for filtering gas, and the outer cover of the container body is equipped with a shut-off valve with a gas filtration device installed inside it between the container inner cavity and the valve seat.

In private options:

- the volume of the inner cavity of the container is selected 1.5-2.5 times the volume of the loading cup;

- in devices for filtering gas, cermet or metal-porous rolled products are used as filter material;

- the outer lid of the container is made with an annular protrusion that abuts against the inner lid of the container and thus provides axial fixation of the relative position of the inner lid and the loading cup with its lid relative to the container body;

- the inner lid of the container is made with an annular tooth and an annular bore on one side and a cylindrical groove equal to the outer diameter of the boot cup lid, on the other, and the bottom of the container body is provided with a cylindrical protrusion, the diameter of the inner groove of which is equal to the outer diameter of the boot cup;

- in case of sealing by welding the outer lid and the inner container body, the flange of the container body is made equal to the thickness of the edge of the container lid, and the diameters of the flange and lid at the weld point are less than the diameter of the container body, and the width of the flange is 6-8 times greater than the total thickness of the flange and the edges of the container lid.

Using the proposed invention will increase the safety and reliability of containers due to:

- gas exit from the loading cup into the volume of the inner container, which will reduce the possible increase in pressure;

- controlled pressure relief before opening the container;

- the almost complete exclusion of irretrievable losses of plutonium dioxide by reducing aerosol emissions.

The proposed design of the inner container expands its technological capabilities in the operations of tightness control, changing the atmosphere and determining the pressure in the container, as well as in the analysis of gas evolution during long-term storage.

The use of an inner lid sealed relative to the container body and its geometry give the inner container a new quality, which consists in increasing its reliability and safety by creating an additional sealing step that reduces pollution of the outer surface of the container body during container loading and unloading operations.

Figure 1 shows a non-separable version of the inner container, in which the sealing of the container body with its lid is carried out by welding.

Figure 2 shows a collapsible version of the inner container.

The inner container of the packaging set of FIG. 1 consists of a container body 1 closed by an external lid 2, equipped with a shut-off valve 3 with a gas filter device with a filter 4 installed therein. An inner lid 5 is provided in the opening of the container body, equipped with two gas filter devices with filters 6, an annular tooth 7, designed to seal the inner cover with the cover of the airlock (not shown in FIGS. 1 and 2), with which the container is docked. The inner lid is equipped with an annular bore 8, which is necessary for gripping the inner lid with a mechanism for its removal and installation. A loading cup 9 of normalized volume with a lid 10 is placed coaxially inside the container body, centering relative to it with the help of a cylindrical protrusion at the bottom of the container body 11 and a cylindrical undercut 12 on the inner lid.

Figure 2 shows how the outer cover of the container 13 is attached to the container body by bolts 14. The sealing of the cover to the container body is provided by a gasket 15.

The proposed inner container can be used as part of a transport and packaging set based on the AT-400 protective container, which is currently used in various packages for the storage and transportation of metallic plutonium and uranium.

Claims (7)

1. The inner container of the packaging kit for storing and transporting plutonium dioxide, consisting of a container body with a tight external container lid and placed inside it, provided with a lid of a loading cup of normalized volume, characterized in that a cylindrical hole is made in the container body for passage of the loading cup in which the inner cover of the con eynera provided with devices for gas filtration, and the outer cover of the container is provided with a closing valve, between the seat and of which the internal cavity of the container taken apparatus for gas filtration. 2. The inner container of the packaging kit for storing and transporting plutonium dioxide according to claim 1, characterized in that the volume of the inner cavity of the container is 1.5-2.5 times the volume of the loading cup. 3. The inner container of the packaging kit for storing and transporting plutonium dioxide according to claim 1, characterized in that in the device for filtering gas metal-ceramic or metal-porous rolled products are used as filter material. 4. The inner container of the packaging kit for storing and transporting plutonium dioxide according to claim 1, characterized in that the outer lid of the container is made with an annular protrusion abutting against the inner lid of the container and providing axial fixation of the relative position of the inner lid and the loading cup with its lid relative to the housing container. 5. The inner container of the packaging kit for storing and transporting plutonium dioxide according to claim 1, characterized in that the inner lid of the container is made with an annular tooth and an annular bore on one side and a cylindrical recess equal to the outer diameter of the lid of the loading cup, on the other, and the bottom of the container body is provided with a cylindrical protrusion, the diameter of the inner recess of which is equal to the outer diameter of the loading cup. 6. The inner container of the packaging set for storage and transportation of plutonium dioxide according to claim 1, characterized in that the container body is made with a flange, the flanging thickness of which is equal to the thickness of the edge of the outer lid of the container, and the diameters of the flanging of the flange and the lid are selected less than the diameter of the container body, the width of the flanges is 6-8 times greater than its thickness. 7. The inner container of the packaging kit for storing and transporting plutonium dioxide according to claim 1, characterized in that the outer lid is bolted to the container body, and a gasket is placed between the cover and the container body.

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