DD247765B5 - TRANSPORT CONTAINERS FOR UNBRANDED NUCLEAR CASSETTES - Google Patents

Description

Explanation of the essence of the invention

The invention has for its object to provide a transport container for unirradiated nuclear fuel cassettes, which consists of an inner and outer container and is filled in the space between them with a substance which has a high neutron absorbing effect under accident conditions with strong mechanical and thermal influences which allows a narrow radial expansion in a tight stowage scheme in the association of several transport containers by a small radial extent. The object is achieved in that the space between the inner and outer container consists of a body made of hardened synthetic resin film and associated grains of borhaltigem glass and / or ceramic in such a way that interconnected pores with a total pore volume of about 25 to 30% with respect to the gap exist.

The solution is that when glass and / or ceramic grains of high boron concentration are used, part of the volume of the interspace is replaced by grains of other substances, and the grains are introduced and sintered without synthetic resin film. Included in the solution is a design in which the cover plates of the space sealed tightly welded only to the outer container and the inner container with radial positive engagement in the cover plates and the cover in the transport state are firmly and tightly screwed to the cover plates.

There are several advantages to the solution. Boron-containing glass and / or ceramic grains have a high compressive strength, which can be easily exploited by the elastic synthetic resin films to take over the mechanical stresses. Furthermore, there is no risk of loss of the absorber material in an intense accident whose severity would be above the IAEA test conditions and which would lead to a leak in the outer container due to the sticking of the grains to each other.

A major advantage of the solution to ensure against the onset of a critical condition is that after a heavy mechanical accident with loss of tightness of the hold and subsequent fall of the transport container into the water, the cargo space and the pore space of the space can be filled with water and after Recovery of the transport container, the water can drain at the connector of cover and inner container from the space.

In addition to the advantages over the mechanical stresses, the high melting temperatures of the boron-containing glass and / or ceramic granules give the resistance to thermal stresses which far exceed the IAEA test conditions.

Furthermore, it is achieved by the porous structure of the body in the space between the inner and outer container effective thermal insulation. As a result, the formation of condensation in the hold of the fuel cassettes is prevented and at the same time favorable conditions for transport in marine climate are created.

embodiment

Fig. 1: shows the partial section of the end of a transport container and a view of the lid Fig. 2: shows the detail wire of Fig. 1 on a larger scale.

An advantageous embodiment of a transport container for unirradiated nuclear fuel cassettes consists of an outer container 1 and inner container 2 and the cover plates 3 connecting them with the resulting space 4. The space 4 is filled with bonded grains 5 of borhaltigem glass. With covers 6, screws 7 and seals 8, the transport containers are closed. The cover 6 have not shown shock absorber elements. The preparation is advantageously carried out in such a way that the outer container 1 and the inner container 2 are initially connected to only one cover 3. The inner container 2 is inserted with radial positive engagement in the cover 3 and the outer container 1 is welded to the cover 3. The resulting gap 4 is then filled with grains of boron-containing glass 5, which are coated with synthetic resin films. Subsequently, a cover 3 is attached to the closure of the intermediate space 4 and welded to the outer container 1. The hardening plastic creates a solid, porous body. After loading the transport container with an unirradiated nuclear fuel cassette, the cover 6 with the screws 7 using the seal 8 firmly and tightly closed. The embodiment described in detail allows a simple production and also allows by post-heat treatment to bond the boron-containing grains 5 made of glass, by sintering. The thereby exiting gases can escape at the connector between the inner container 2 and cover 3.

List of used reference numbers

1 outer container

2 inner containers

3 cover

4 space

5 grains

6 lids

7 screw

8 seal

Claims (2)

1. Transport container for unirradiated nuclear fuel cassettes, consisting of an inner container and a surrounding cylindrical outer container, wherein the gap between the inner container and outer container, which is covered with cover plates, filled with a neutron absorbing material and that the cover plates of the space with the outer container directly welded and in the transport state firmly and tightly bolted to the lid of the transport container, characterized in that the space consists of a body of hardened synthetic resin film coated and associated grains of borhaltigem glass and / or ceramic in such a way that interconnected pores with a pore volume of 25 to 30% with respect to the gap are present and that the inner container (2) with radial positive engagement in the cover plates (3) is inserted. 2. Transport container for unirradiated nuclear fuel cassettes, consisting of an inner container and a surrounding cylindrical outer container, wherein the space between the inner container and outer container, which is covered with cover plates, filled with a neutron absorbing material and that the cover plates of the space with the outer container directly welded and in the transport state firmly and tightly bolted to the lid of the transport container, characterized in that the gap consists of a body of bonded grains of borane glass and / or ceramic in such a way that the grains used are introduced and sintered and that Inner container (2) with radial positive engagement in the cover plates (3) is inserted. For this 1 page drawings Field of application of the invention The invention relates to the design of a transport container for the transport of unirradiated fuel cassettes of nuclear reactors. Characteristic of the known technical solutions Various containers for the transport of radioactive substances are known from the prior art, which consist of several materials and preferably mechanically strong inner and outer containers. The inner container is used to hold the radioactive substances, while the outer container acts as a protective container. For the transport of unirradiated fuel cartridges, the construction of the transport container is particularly influenced by how large the distance between several transport containers from each other. At short distances, fabric combinations with components that can absorb neutrons are necessary. In DE-OS 2 311 162 a transport container is described in which the protective container is formed from an insulating sheath of phenolic resin foam, wood, mineral insulating wool or a combination of said materials and an outer thin-walled cylindrical sheet metal housing. The wall thickness of the insulating cover is at least 5cm. It is also known to shed the space between the inner and outer containers with a plastic material containing neutron absorbing substances evenly distributed; As plastic material a structure of borax and epoxy resin is provided (DE-AS 1 514 957). From DD-PS 223 853 a container for the transport of radioactive materials is known, in which between the double-walled container boundary a variable layer of a mixture of synthetic resin and filler is filled from gravel. The fillers / gravel types used are boron carbide, quartz, metal spheres and their combinations. These materials are bonded or cured with the synthetic resin with appropriate heat treatment. In DE-OS 2,821,780 a transport and storage device for radioactive substances is listed, in which case glass grain is used as a filling of the housing wall. In addition, a double-walled transport container for fresh fuel cassettes is known from another patent DD-PS 131 445, wherein the space between the inner and outer container with an existing inorganic substances Kaltvergußmasse, introduced into the neutron absorbing substances, preferably cadmium chips, evenly distributed are, filled out. To protect against damage or loss of these substances, the spaces between the inner and outer containers are sealed with welded covers. The most essential dimensioning variables of such transport containers are derived from conditions of accidents with mechanical and thermal destruction effects. Taking into account the growing safety requirements, the known transport container to preserve the absorbing effect for neutrons under the extreme accident conditions are disadvantageous and compensation by increased material costs and additional measures as consuming. Object of the invention The aim of the invention is to provide a space-saving transport container for unirradiated nuclear fuel cassettes, which has a high security against the occurrence of a critical condition under accident conditions.