Solid material comminution or disintegration – Processes – Miscellaneous
Reexamination Certificate
1999-08-26
2001-12-11
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
Miscellaneous
C241S283000
Reexamination Certificate
active
06328235
ABSTRACT:
The invention is based on a process for the decomposition or breaking down of articles, especially contaminated articles, by means of a decomposition device. The invention also relates to a process for the decomposition of articles by means of a flexible grinding element, such as a grinding wire, rope or cable. Finally, the invention relates to an apparatus for decomposition of an article by means of a flexible grinding element, such as a grinding wire, rope or cable.
To dispose of contaminated articles, such as glove boxes or radioactively contaminated heat exchangers, it is known to remove them from the usually tight areas where they were set up and then to pack them unbroken down, or else ship them to a specially set-up decomposition site and decompose them there. Decomposition to a size suitable for packing is preferred, so as to increase the capacity of the typically standardized ultimate disposal containers used. During the decomposition process, by reason of the process, considerable quantities of sometimes dangerous substances are released. In the case of the decomposition of plutonium-contaminated glove boxes, complicated and expensive devices in a special secure work room (caisson, alpha-cell) are therefore necessary as a rule.
To lessen this effort and expense, International Patent Disclosure WO 97/30457 proposes a process in which dangerous substances present in the interior of the articles to be disposed of are prevented from being released by the provision that the articles are made into a foam with material that hardens. In the case of decomposition, these substances are fixed in the region of the interface. The additional filler material at the same time serves the purpose of fixation of the built-in fixtures for the subsequent mechanical decomposition.
It is also known for articles that are to be decomposed to be frozen into a block of ice, and then to saw the block of ice apart, with the components frozen into it (European Patent Disclosure EP 0 327 841 B1).
According to German Patent Disclosure DE 39 40 691 A1, articles are decomposed with the aid of a grinding wire; a varying cutting line has the result that an essentially point-like engagement to the article to be decomposed is obtained. The varying cutting line is attained by supporting the rollers that guide the grinding wire in a fixed spacing from one another in a rotary element, which must be displaced about a fixed axis in a pivoting motion in order to vary the cutting line.
German Patent Disclosure DE 40 27 156 A1 provides a cutting device in the form of a hacksaw, circular saw, or keyhole saw, which can execute both horizontal and vertical motions.
According to German Patent Disclosure DE 695 01 171 T2, particles released in the decomposition can be fixed by means of a binder, in the form of a gel.
While packing articles without prior decomposition suitable for packing leads to incompletely filled ultimate disposal containers and thus to an uneconomical utilization of the ultimate disposal site volume occupied, the preliminary decomposition that is suitable for ultimate disposal purposes often requires transportation to the decomposition site. Additional provisions may then be necessary to prevent recontamination of areas that have already been cleared. In the case where plutonium-contaminated glove boxes are transported, for instance, extremely complicated and expensive provisions in this respect are required.
Regardless of this, decomposition of articles in a way suitable for packing often encounters limits dictated by practical considerations, since the cutting guidance that results for optimal packing must often be guided through heterogeneous cross sections of articles. In steam generators, for instance, cuts must extend through bundled pipes, some of them with resilient spacers, or in the case of glove boxes they must run through motors, hardened guide rails, chain conveyers, lead glass windows, or the like. Because of this, many special tools may be necessary, to enable reliably separating the existing materials and cross sections. It must be taken into account that such special tools, after being contaminated with plutonium, cannot be reused, or can be reused only under special conditions.
To provide a remedy for these problems, universal tools such as band saws can be used, but these are too large for most applications.
But even if the use or scope of special tools required can be reduced by prior clearing away of the intended cutting area, nevertheless expensive provisions are needed to prevent the release of contaminant ions or to prevent a radiation exposure to the human workers.
Freezing articles, as taught by the prior art, entails a major expenditure of energy for freezing and for defined thawing of the cut parts, and is moreover unsuitable for many applications.
If contaminant ions are to be bound, or built-in fixtures are to be fixed in articles by means of organic hard substances, then when the articles are decomposed, an undesired temperature elevation occurs in an interface that leads through the highly insulating foam, and this increase can lead to pyrolysis or fire and thus to the release of contaminant ions. These disadvantages can be eliminated by providing tool cooling, as well, for instance by evaporating inert gas.
The decomposition could be simplified if hard-metal-equipped saws were used. However, it is then necessary for the built-in fixtures of the articles to be properly fixed. This also requires the most perpendicular possible disposition relative to the cutting plane, which in practice leads to difficulties. It is therefore repeatedly found that in band saws, hard metal teeth break off, requiring that the cutting process be repeated, with a completely new cut if the hard metal teeth that have broken off cannot be removed from the cutting seam. There would also be the possibility, using conventional rope saws, of breaking down built-in fixtures in articles, as long as the possibility were available of grinding diamond-coated grinding bodies on the rope free, for instance by means of concrete bodies additionally placed in the cutting area. However, to reduce the frequency with which the grinding bodies catch on sharp edges, cutting must be done with a high rope speed. This increases the problem of a possible rope breakage, however, as well as of severe thermal stress on the fittings, so that relatively great quantities of then-contaminated coolant are produced. In addition, radioactive aerosols can also be spread by a recoiling rope or saw band, this in turn means that to prevent contaminant propagation, both the free-running tool part and the entire work area must be partitioned off with regard to ventilation. This requires a great amount of space, for instance for deflection rollers necessary for guiding the rope. Alternatively, compromises in guiding the cut must be accepted.
The object of the present invention is to refine a process and an apparatus of the type defined at the outset in such a way that by means of an easily manipulated decomposition device, and without using devices that reach in three directions, in-situ decomposition appropriate for packaging becomes possible in the tightest possible spaces. At the same time, it should be assured that the radiation exposure or contamination load is only slight and easily handled.
According to the invention, this object is attained essentially in terms of the process on the one hand in that the decomposition device executes an oscillating motion, in such a way that automatically, as a function of the progress and/or duration of the decomposition of the article, a varying resultant of the direction of the decomposition force introduced by the decomposition device is established. In particular, it is proposed that the article is decomposed by means of grinding, and the decomposition device generates cutting lines that automatically vary continuously in their direction, as a function of the progress and/or duration of the decomposition. In particular, as the decomposition device, a flexible grinding element, such a
Arnold Hans-Uwe
Christ Bernhard
Ledebrink Friedrich-W.
Dennison, Scheiner Schultz & Wakeman
DETEC Decommissioning Technologies GmbH
Rosenbaum Mark
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