Patent Number: 052788776
Section: summary

BACKGROUND OF THE INVENTION The invention concerns a process for dismantling buried unsheltered equipment at risk of radioactive contamination, particularly the kind that extends in a straight line, such as shut-down effluent pipes. As part of a general radioactive-contamination risk protection policy, waste and equipment that may be contaminated must be eliminated when the equipment is taken off line and the areas it occupied must be made available for other uses. Indeed, even when pipes are buried in the ground, they may eventually deteriorate and spread contamination by infiltration and/or irrigation, which is very difficult to contain. Generally, a state of noncontamination or decontamination means a state in which the radioactivity of a material is below a predetermined threshold, for example, one stipulated by law. SUMMARY OF THE INVENTION The invention proposes a dismantling process that meets the requirements of strictness and confinement essential for work in an area potentially subject to radioactivity. More precisely, the invention proposes a process for dismantling unsheltered, buried equipment which is at risk of contamination and is possibly irradiating, characterized by the fact that sections of the equipment are dismantled in units, under the cover of a movable vessel placed above the section to be dismantled. According to one special method of implementing the process in the invention, after the vessel is put into place, the section to be dismantled is first: surrounded by a protective envelope; then PA1 disengaged on site in its trench; PA1 separated from the rest of the equipment; PA1 put into the vessel in pieces; PA1 placed in a container that is in the vessel; and PA1 evacuated from the vessel in the container. PA1 It allows the vessel to be positioned with great precision on spaces or land with reduced access and/or on land where there has been an accident; PA1 It allows work to be done in the ditch without risk of landslide; and PA1 It allows vessel supports to be set up quickly and inexpensively. PA1 a self-supporting structure built around a deck that has a central opening; this structure supports various mobile lifting or handling tools and an outside envelope equipped with a handling room and/or at least one window with a movable cover; PA1 a flexible protective curtain located around the central opening to surround the work area where the section being dismantled is located and to isolate it from the outside, leaving the area accessible from the vessel; PA1 a forced ventilation system with a filter to filter out contaminated dust from inside the vessel. Moreover, depending on the radioactivity of the debris and the ditch where the dismantled section was located, any soil whose radioactivity exceeds a predetermined threshold is evacuated from the ditch to an appropriate storage area. One option is terracing to disengage ahead of time the sections to be dismantled after the section presently being dismantled, during which any waste whose radioactivity is higher than a predetermined threshold is stored temporarily in said vessel before it is evacuated to the storage area. In one variation of the process in the invention, supports for the movable vessel, such as blocks or a support rail are set up on either side of the equipment as the equipment is being dismantled. The vessel is then moved, for example, by crane. This option of setting up temporary supports such as blocks is very advantageous in several respects: The invention also concerns a vessel for implementing various versions of the process described above; the vessel contains: According to one variation of the vessel that is consistent with the invention, the vessel also includes a movable internal cover over the central opening to isolate the inside of the vessel for a period of time from the work area where the section being dismantled is located. Advantageously, the vessel also includes a moving-head-type vacuum device with a filter to pick up dust in that area. In one special embodiment of this variation, the forced ventilation device and the vacuum ventilation device are made so that once the movable inside cover is put in place, the work area is depressed in relation to the inside of the vessel and the inside of the vessel itself is depressed in relation to the outside air. According to another variation of the vessel that is consistent with the invention, the flexible curtain is composed of a bellows, one end of which is joined to the edges of the central opening and the other end of which bears a rigid framework for housing the bellows when it is retracted. Advantageously, this bellows is maneuvered in extended or retracted position by a lifting device with a winch on the frame. According to yet another variation of the vessel that is consistent with the invention, two sides of the opening form a rolling path for a cart suspended in the opening. Advantageously, the cart carries a hydraulic scoop. According to another embodiment of the vessel that is consistent with the invention, the deck has an area for a container accessible from a window with a movable cover located preferably in the part forming the roof of the vessel and, possibly, a work area for the section being dismantled. Advantageously, the deck also has an area for a container of soil accessible from another window with a movable cover located preferably in the part forming the roof of the vessel. As an option, the vessel may include a hopper equipped with a controlled-opening helmet that passes through the outside envelope and comes out above the area for the soil container. This hopper takes the contaminated terracing soil extracted by a hydraulic scoop with closed buckets located on the outside of the vessel. Such an arrangement makes it possible to confine debris from the equipment being dismantled, on one hand, and soil from the ditch and the embankment that may be contaminated. According to yet another variation of the vessel consistent with the invention, the vessel is constructed around two half-shells assembled so that they can be dismantled on both sides of a vertical median plane, preferably parallel to the largest side of the deck. According to yet another variation of the vessel consistent with the invention which can be used particularly for dismantling equipment with straight extensions, the central opening is rectangular and is adapted so it can be positioned carefully and aligned with the specific section to be dismantled.