JPS5950393A - Container for storing safely nuclear fissile material solution in critical - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The unexploded ψl relates to a container for the criticality safe storage of fissile material solutions, in particular plutonium solutions.

In order to be able to handle or store fissile material with criticality safety, it must be handled or stored in subcritical quantities or in safe geometric conditions. The storage of fissile material in safe, subcritical quantities has hitherto been highly irrational and uneconomical in known storage vessels; for example, the critical quantity of plutonium nitrate solution is
At a concentration of 200 P Pu,/l (commonly used in reprocessing), even solution 101 contains 7 to 2 Pu2, which is only a very small amount. For the storage of this solution, a large number of small individual containers have to be used, which all have to be placed at a safe distance from each other.

The handling and operation of such container storage is very expensive and cumbersome. In addition, a large number of individual containers requires a relatively large footprint.

For the storage of fissile material in safe geometric conditions, flat tanks with safe layer thicknesses, cylindrical containers with safe diameters, or annular interstitial containers can be used. Storing several meters of such a fissile material solution in a geometrically secure container would result in extremely large overall heights and lengths, and thus the size of buildings, or Again, they must be stored side by side in several geometrically secure containers at a safe distance from each other.

For example, 20
There are the following ways to store 5 m8 of plutonium nitrate solution with a concentration of Q y-Pu/l: When stored in individual containers containing a safe amount of plutonium each time, in this case this fission For the sexual substance solution, 500 containers each with an internal volume of 101 are required. The safe layer thickness for this solution is approximately 7 cm.
Therefore, if the width of the storage container is 4 m, a total height of about 18 m is obtained. If a cylindrical container is selected for storage, this safe diameter is approximately 18 Fahrenheit. From now on, the internal volume is 5
For a storage vessel of ms, a total height of approximately 196 m results. For an annular gap vessel with an external diameter of 60σ, a safe layer thickness of approximately 6 m is required. Under these preconditions, the internal volume is 5m.

The storage container shall have a total height of approximately 49 m.

Accordingly, the storage vessels described above are unacceptably large and uneconomical in terms of their overall length. It is difficult to handle or store fissile material solutions in safe quantities in individual vessels. , it is equally uneconomical due to the large number of individual containers to be used (10). This is only possible if the solution is homogeneously added with, for example, gadolinium as a poisonous substance.However, this is of little importance in the normal case, because 1. neutron poisoning is added before processing into plutonium firing elements. This is because the material has to be separated from the fissile material again in an expensive process. In addition, controlling the uniform distribution of the neutron poison in the fissile material solution is difficult, and the amount of gadolinium consumed is relatively large, and gadolinium is rare and therefore expensive.

Therefore, it is an object of the present invention to provide a container for storing fissile material solutions, in particular plutonium solutions, in critical safety, which has an easy-to-handle size and is not uneconomical due to the corresponding space requirements. It was something to do.

This problem is solved according to the invention by several compartments in geometric criticality safety conditions, the containers of which contain neutron poisonous substances and which are connected to each other by openings by separating walls provided at fixed intervals by spacers. The solution is that it is divided into . The compartments are arranged so that the fissile material solution can pass from one compartment into the next during filling of the container. In this way, the storage container can easily be completely filled with fissile material solution.

In order to ensure a criticality-safe arrangement, the separating walls between the individual chambers may consist, for example, of special steel sheets containing homogeneously alloyed neutron poisonous substances, or advantageously a It consists of two special steel thin plates in which a neutron poisonous substance is embedded.However, the neutron poisonous substance can also be placed over the separation wall soil. The spacing between the compartment walls is chosen such that the entire system remains subcritical with a safety factor, which is made considerably safer by the installation of spacers.

In order to ensure the external safety of the entire container, this container is provided with a supporting outer wall, for example made of concrete.1 To ensure a safe spacing, the separating walls are connected to one another by spacers.

It has been found to be particularly advantageous if the container is of cylindrical design and the separating wall is arranged circularly and concentrically within the container.

For example, the safe layer thickness for such an infinitely multiple annular gap vessel using one and two-thick thick slabs of funium for the separation wall soil as a poisonous substance is actually less than 5 Crn, but this so-called ring slab can be made into infinity. It is also possible to arrange them in a mating manner to form a single container, but this is completely excluded for ring slabs that do not contain toxic substances. This method requires a multi-annular interstitial vessel with two hafnium plates as the poisonous substance, which contains 5 m8 of plutonium nitrate solution and whose outer diameter is 1 m8.
．． For a multi-annular gap vessel which should be 5 m, a total height of only 2.9 m is required, but for a non-toxic annular gap vessel with an external diameter of 1.5 m the total height is still less than 30 m. Of course, in addition to multi-annular interstitial containers, rectangular and square containers with rectangular and square single compartments may also be used.

It has also proven advantageous to arrange a moisture detector between the double walls, thereby reliably indicating damage to the separating wall. It is also advantageous to poison the spacer with a neutron-absorbing substance.

The invention will now be described in more detail with reference to the accompanying drawings. FIG. 1 shows a cylindrical storage container in longitudinal section. Container 1 is circular;
It is divided into several compartments 3 in the form of an annular gap by separating walls 2 which are concentrically spaced apart from each other. The container 1 has a filling port 8 and an exhaust pipe 9 at the top of the stem.

The container 1 is housed in an outer support wall 4 made of concrete, for example. Separation wall 2 is everywhere container 1
does not extend to the bottom of the container, so that an opening 10 remains which allows uniform filling of the container.

However, this area is also maintained criticality safe by the thin plate 11 containing the neutron poisonous substance, which is disposed and mounted on the bottom of the vessel. Spacer 5 (only partially shown in the drawing)
As a result, the separating walls 2 are kept at a distance and a safe layer thickness of the annular gap-shaped compartment 3 is ensured. The container 1 is discharged by means of a discharge valve 6. The container is equipped with a removable lid 'r in order to be able to control the inside of the container and the separation wall 2. The integrity of the separation wall 2 can also be monitored from the outside, for example with a neutron flux meter. However, in particular moisture detectors are used, which detectors have two separating walls.
It can be installed particularly easily in the separating wall 2 if it consists of two layers and a neutron poisonous substance is present between them.

FIG. 2 shows a cross-sectional view of a multi-annular gap vessel, and FIG. 3 shows a separation wall of an advantageous embodiment, in which the neutron poisonous substance, for example in the form of a lamella 12, is placed on both walls of the separation wall. part 1
It is installed between 3' and 14.

The separating wall 2 consists, for example, of special steel sheets, to which the neutron poisonous substances boron, cadmium, /' 7 = ram and/or gadolinium are added and alloyed uniformly. However, the neutron poison substance can also be placed over the separating wall 2 in the form of a sheet or present between the two wall parts 13, 14, preferably in the form of a powder or sheet.

The mutual spacing between the separation walls 2 ensured by the spacers 5 depends on the type and ion concentration of the fissile substance solution, as well as the type and amount of the fissile substance used. However, this is generally between 3 and γC. It is between.

[Brief explanation of the drawing]

The figures show an embodiment of a storage container containing a poisonous substance according to the invention, in which FIG. 1 is a longitudinal sectional view of a cylindrical storage container and FIG. 2 is a cross-sectional view of a multi-annular interstitial container. FIG. 3 is a schematic representation of the separating wall of an advantageous embodiment. ■... Container, 2... Separation wall, 3... Partition, cow... Supporting outer wall, 5... Spacer, 6... Discharge valve,
7... Lid, 8... Filling port, 9... Exhaust pipe, 10.
...Opening, 11...Thin plate at the bottom of the container, 12...Thin plate-shaped neutral eutoxic substance, 13.14...Wall portion

Claims (1)

[Claims] ■ Containers (1) containing neutron poisonous substances are connected to each other by an opening (10) by a separating wall (2) provided at a fixed distance from a spacer (5) K. A container for storing a fissile material solution in a criticality-safe manner, characterized by being divided into several criticality-safe compartments according to geometric conditions. 2. Container according to claim 1, wherein the container (1) is of cylindrical construction and the separating wall (2) is arranged circularly and concentrically in the container (1). 3. The separating wall (2) is constructed as a double wall, and the neutron poisonous substance (12) is present between both wall parts (13, 14) of the double wall. Container according to item 2. 4. Claims 1 to δ, in which a moisture detector is disposed between both wall portions (13, l 4- ) of the double wall.
5. A container 3 according to any one of claims 1 to 4, in which the spacer (5) is also added with a neutron substance;