Industrial technique

(74) Agent: Cabinet J. Bonnet-Thirion, L. Robida and G. Foldes.

(54) Installations for the storage or processing of fluids harmful or harmful to the environment.

(72) Invention of:

(33) (32) (3Î) Conventional priority:

Sale of booklets at IMPRIMERIE NATIONALE, 27, rue de la Conve ntion - PARIS (15^e)

10599

The present invention relates to installations for storing or using fluids which are harmful or harmful to the environment.

It applies in particular to tanks containing chemicals or very low temperature fluids, to nuclear tanks in light water and sodium-cooled installations, as well as to contaminated effluent tanks.

It is important, in such reservoirs, to ensure the speed of monitoring and small repair operations, in order to minimize the intervention times on devices for which this intervention results in unavailability of operation.

This monitoring must often be carried out under extreme conditions of operating temperature (for example in cryogenic fluid tanks or in sodium reactors) which do not allow the arrival of operators.

Automatic rapid examination devices should be provided for prevention.

it is also advisable to organize an automation security when we are in the presence of access difficulties due to the spacings and congestion.

For safety reasons, the commonly used arrangement consists of building two fluid-tight barriers. The first barrier contains the dangerous or expensive fluid, the second is intended to ensure a seal in case of rupture of the first during operation of the installation, accident which can be serious and lead to a prolonged or even permanent shutdown of this installation.

Without even considering a rupture, a sometimes minimal leak can cause the unavailability of the installation, the secondary barrier then playing the simple role of product recovery and protection.

The object of the invention is to facilitate the examination, maintenance and repair of the first barrier in difficult environmental conditions and to authorize in particular the use of examination methods which can be implemented easily and quickly, and means to identify the area whose development should be monitored. It is also advantageous, because of the environment, the dimensions and the costs that can

10599 cause the unavailability of the work, to provide a rapid and automatic tool for examination, location of faults, and minor interventions, even those which should not be given special attention in less hazardous circumstances .

To this end, the invention proposes to systematically promote free access to the primary barrier, to rid the external surface of any heat-insulating or other possible protective layer to transfer them to the secondary barrier, and to swim between the two barriers. sufficient space for inspection and maintenance operations.

Conveniently, locating pieces placed on the surface of the barrier make it possible to locate with precision the zones which one wishes to monitor from time to time.

Advantageously, pins fixed on the surface of the primary barrier serve to achieve the above objectives and further facilitate the installation and operation of automated control or intervention devices.

The foregoing measures are not sufficient in all cases of application of the invention. Indeed, to facilitate the implementation of tools of all kinds, it is necessary to size the space between the primary and secondary barriers. If we left it there, the large space thus formed would be invaded by the fluid in the event of rupture of the primary barrier, and the level of fluid would drop suddenly inside this barrier. This can create extremely dangerous situations, this is the case, for example, of nuclear reactors where, for safety reasons linked to the operation of fission products, it is prohibited to dewater the core of the reactor whatever the ac30 cidents considered. Indeed, heating by gamma effect is sufficient to cause the core to melt if it is not cooled by convection of the refrigerant.

To avoid this catastrophic situation, the invention proposes to fill the space between the two barriers with displaceable bodies, which prevents the excessive drop in level of the liquid in the event of rupture of the primary barrier. In most cases the space to be filled is in the form of a volume of revolution and the bodies or filling blocks are in the form of sectors delimited by meridian planes and arranged one after the other in a circumferential row. They are placed on a track

10599 of circular rolling and an access door to the space thus furnished is provided in the secondary barrier. In the event of an intervention, the door is opened, one of the filling sectors is removed if necessary, to clear a space into which the tooling for examination, monitoring, repair or more generally maintenance is introduced. We circulate the assembly that constitutes the train of filling blocks and tools along the outer circular face of the primary barrier to bring the tools to the right of a determined area and we proceed by implementation of remotely controlled and monitored operations. If necessary, the space freed by removing a sector can also be used to introduce personnel to put it within reach of the primary barrier. Optionally, these filling blocks can play the role of storage tanks which can serve, for example, to facilitate the emptying operations of the tank.

Once the maintenance operations are completed, we proceed in the opposite direction, that is to say that we put the train into circulation to bring the tools to the right of the opening, we remove it, we put back possibly the missing sector in place and the secondary barrier is closed.

The objects, characteristics and advantages of the invention will become apparent, moreover, from the description which will be given below, relating to an embodiment chosen by way of example and shown in the accompanying drawings.

The example chosen, which moreover has no limiting character, relates to a nuclear reactor cooled with sodium. However, the invention applies equally well to reactor vessels cooled with light water and to other tanks for hazardous products.

In these drawings:

FIG. 1 schematically represents a liquid sodium reservoir for a nuclear reactor;

2 shows a section in plan along the line II-II of Figure 1 j Figure 3 shows on a larger scale a carriage for monitoring and maintenance of the installation.

In the drawings, a buried casing 1, made of concrete, is covered on its inner face with a metallic coating 2, itself covered with a layer 3 of insulating material. A stainless steel tank 4, with cylindrical wall 5 bottom 6 in the shape of an inverted dome, is adapted to receive, according to known arrangements

10599 and not shown, a nuclear reactor core cooled with sodium, the tank 4 and the protected casing 1 constituting, for sodium, primary and secondary barriers.

According to the invention, the tank 4, with a bare external surface, is 5 furnished, on the latter, by isolated points, with elements 7 used for locating and which can take, if necessary, the form of attachment pins for inspection, maintenance or repair equipment.

A door 8, arranged in the secondary barrier 2, 3 provides access to the space formed by the two barriers, via a tunnel 9 and an airlock (not shown). This space has the dimensions required to receive a carriage 10 (Figure 3). The carriage 10 is provided with a set of wheels 11, mounted on jacks so as to be adjustable in height, and allowing the carriage to travel along the tunnel to the interior of the space, on a radial track 13, so that a second set of wheels 14, with which the carriage is provided, is plumb with a second circumferential track 15, placed on the flat bottom of the casing 1. A hydraulic unit 16 can then actuate the jacks 12, to retract the wheels 11 upward and allow the carriage to rest on the track 15. Two other jacks 17, controlled by the hydraulic unit 16 and fixed to the frame 18 of the carriage, carry a guide path 19, of profile similar to that of the bottom of the tank 4. This guide path, the distance of which can be adjusted to the surface of the tank by means of the jacks 17, serves as a support and a rolling path for a television camera 20, the displacement of the latter along this path being provided by hydraulic control.

On the other hand, a hydraulic motor 21 acts on, at least, one of the wheels 14 of the carriage, to move it along the circumferential track 15. The assembly thus arranged allows the camera 20 to scan the entire outer surface of the bottom 6 of tank 4.

The space formed by the bottom 6 of the tank with the secondary barrier 2, 3 is occupied, for the most part, by a train of elements 22 arranged in rotation on the circumferential track 15 "each of these elements being delimited by two meridian planes. At least some of these meridian faces are lined with elements 23 which provide a drive connection between the blocks 22, by simple contact and push, and / or by traction.

Safety devices not shown are also provided

10599 to avoid the vertical displacement of the elements or carriages under the effect of Archimedes' push which would result from a rupture of the tank, and thus avoid the derailment of this train of elements.

The train of elements 22 is formed so as to reserve, in line with the radial track 13, a free space intended to receive the carriage 10. It is possible, as a variant, to arrange a special filling block therein, adapted to be removed outside duvelage 1, to be replaced in due time by the carriage 10.

The blocks 22 are made of any suitable material having a certain measure of compatibility with liquid sodium. In the event of a leak in the wall of the vessel 1, they have the effect of considerably reducing the drop in the level of sodium, and of preventing any risk of dewatering '' of the reactor core.

Inspection and maintenance of the tank by means of the carriage 10 is done as explained above, the carriage being capable of exerting sufficient force to move the train of filling blocks

22.

The arrangements according to the invention, which have just been described, ²⁰ are intended only for one of the possible applications of this invention and therefore do not have any limiting character. They can therefore be the subject of various modifications and variants without departing from the scope of the invention, this is how the trolley can be equipped with all the appropriate elements of inspection, analysis, monitoring, 'maintenance and repair, or hooking members to the tank. It may also be used, if necessary, to transport inspection and maintenance personnel. A vertical telescopic guide path, having a function similar to that of path 19, can be used to inspect and repair the cylin30 drique part of the tank.

Thus, also, with such a carriage it is possible to come to place in a predetermined place of the tank of the measurement or monitoring devices or the like which will be carried by tools coming to hang on the pins 7 j then to withdraw these devices by a similar maneuver once the surveillance campaign has ended, or at any other time favorable to the operator.

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