DE1094378B - Device for non-contact measurement of radioactive contamination of liquids and gases - Google Patents

Description

Device for non-contact measurement of radioactive contamination of liquids and gases For the detection and measurement of radioactive contamination Different methods are used for liquids and gases: The simplest is the direct contamination measurement in which the detection organ, for example a counter tube or scintillometer, on all sides or to a large extent from the contaminated Medium is surrounded. This achieves a detection sensitivity z. B. for Sr90, those in the case of liquid measurements in the order of magnitude of 10-6 mC / 1, in the case of gas measurements of 10-9 mC / 1. This sensitivity is sufficient for all cases in which with the subsequent dilution of the concentration can be expected, for example for the control of waste water or exhaust gases.

In general, one works with the direct measurement with thin-walled Large-area counter tubes, because they have a much larger surface with the same effort can give as a scintillation crystal; due to the large surface they a comparatively more sensitive detection of beta rays, which - in contrast to gamma rays - are linked to almost every atomic decay.

With measurements of this kind it is occasionally disturbing that the outer wall the detection organ itself becomes contaminated over time; then larger ones step Indications as to the actual contamination of the water or air. To avoid frequent cleaning of the surface, which is the case with thin-walled counter tubes or thin protective layers over scintillation crystals are questionable, one has therefore the detection organs with replaceable, thin covers, preferably made of contamination-resistant plastics. For liquid measurements It is also known that the liquid in the form of a uniformly thick, continuous to bring flowing cylinder, in the middle of which the detection element is contact-free is arranged, be it by forming a continuously moving freely in space flowing liquid jacket or by tangential injection of the liquid in a stationary cylindrical container with a layer of liquid at the bottom delimiting the drainage opening.

Instead, the invention proposes that the vertical arranged, upwardly open and preferably conical or parabolic longitudinal section having container about its longitudinal axis in such a way displaced in rotational movement is that the liquid over the entire container surface in an approximately more uniform Layer thickness is distributed. A rotating cylinder can also be used, but for certain tasks are less suitable due to the formation of unequal layer thicknesses. Due to the centrifugal Kraft creates a fluid-free space in which the radiation receiver is located.

This solution has compared to the previously known liquid measuring devices the advantage that you fill, for example, a given amount of liquid and at a suitable rotation speed in the form of a thin, standing layer can bring around the detection organ. One can see the layer at a parabolic Container to an equal over the container height, approximately in the case of a conical container bring the same layer thickness.

The less liquid is available, the thinner the im Medium formed layer; the disadvantage that less active substance is available is then partly due to the reduced internal absorption in the layer compensated. Naturally, this only applies if the layer thickness is correct from the outset is not greater than the finite range of the occurring beta rays.

The formation of a layer of approximately uniform thickness over the height the container is facilitated by the fact that in a development of the invention on a ring diaphragm attaches to the upper edge of the container, on which the rising liquid is jammed.

Any contamination of the container wall is effective with this arrangement not directly on the recipient, but only weakened by the layer of fluid; if the liquid layer is larger than the beta radiation range, then it becomes the contamination of the container wall is no longer noticeable at all. Nevertheless the container wall becomes replaceable and made of contamination-resistant material produce.

Instead of measuring a limited volume of liquid, you can always use the described arrangement for continuous flow measurements use newly flowing amounts of liquid; then the liquid is expedient fed in from below, with one in the supply pipe rotating with the container For example, a helix can be built in, which draws the liquid from a reservoir pulls up into the container.

With continuous flow, the container fills up to a liquid layer thickness, which at the top is equal to the width of the dust cover. After exceeding the Dust cover leaves the liquid from the rotating container.

A higher sensitivity than with the direct display can be achieved through Enrichment of radioactive components by, for example, the liquid passes through a filter in which, after adding adsorbent or Precipitants enriches the activity.

It is one of the advantages of the arrangement described that they with minor additives is also suitable for filter enrichment methods. Perforated namely one the wall of the rotating container and puts a filter accordingly Form, the liquid passes through the filter.

This automatically results in a balance in the distribution of more active Particles all over the filter wall because of the amount of liquid passing through follows the law of least resistance. So is a filter section through Attachments with particles have become less permeable than another section, so now a larger amount of liquid flows through the more permeable part in the unit of time, until the same flow resistance has formed everywhere.

The uniformity of distribution can also be improved by uneven distribution of the outflow bores in the rotating container, one Adaptation to the upwardly increasing centrifugal forces is to be aimed for.

With this training of the facility must understandably the above-mentioned dust aperture be wider than for continuous direct measurements; because the all of the supplied liquid should now pass through the filter; you can finally Replace the dust cover with a cover and the measuring element only after it has been completed Introduce enrichment.

In order to replace the rotating container when moving from the The container becomes superfluous right from the start perforated, d. H. designed as a sieve; then you can use a impermeable, exchangeable film and a permeable one for the enrichment measurement Insert filter.

Occasionally, the liquid may be of interest in the enrichment method to run through the system several times; this is due to the suction effect the helix and reached by two changeover cocks.

Finally the device can also be used for enrichment when measuring Air contamination can be used.

In this case the rotating container will be at the bottom one Attached impeller, which creates a negative pressure in the drain space and thereby the draws incoming air through the filter.

The same impeller can also remain for the liquid measurement, in order to get through the created company pressure pulling the liquid through the Speed up filters.

In the figure, the device described is shown schematically: 1 is a rotating conical container which is driven by a motor via the cable 2 is driven. On the inner wall of the container there is a waterproof one Slide 3 for direct measurements or a filter paper for enrichment measurements. in the first case a liquid rises 4, which after screwing in the stopper 5 is filled into the container, up on the side walls and acts when it is radioactively contaminated, on the detection organ 6. The thickness of the liquid layer is limited at the upper end of the container by the retaining ring 7, through its drainage openings the excess liquid enters the drain space 8 and through the valve 9 is forwarded.

If you want to continuously measure the amount of liquid flowing through, so the stopper 5 is removed and the liquid through the tap 10 passed into the reservoir 11, from where it is rotated with the container Helix 12 is pulled up.

In the case of the enrichment measurement, the film becomes impermeable to water 3 replaced by a filter and the congestion ring widened so that the inflowing Liquid only enters the drainage channel 8 through the filter. At restricted Liquid quantities can be achieved by changing the taps 9 and 10 that the liquid flows back to the reservoir in order to pass the filter as often as required.

If the device is to be used for air enrichment measurements, so the dust cover 7 is replaced by a cover that covers the interior of the rotating container completes. The air to be measured can now be passed through the tap 10 and the coil 12 flow into the interior of the container and is due to the effect a negative pressure in the drain space 8, which is generated by the impeller 13 will.

Claims (5)

PATENT CLAIMS: 1. Device for non-contact measurement of radioactive Contamination of liquids in which the liquid is in a container in such a way is set in rotation that a liquid-free central space in the container arises into which a radiation receiver can be inserted, characterized in that the vertically arranged, open at the top and preferably conical or parabolic Container having a longitudinal section about its longitudinal axis in such a rotational movement it can be displaced so that the liquid is approximately more uniformly over the entire surface of the container Layer thickness is distributed. 2. Device according to claim 1, characterized in that the upper At the edge of the container an annular diaphragm is provided for damming up the rising liquid layer is and through a fixed outer wall a drain space between the rotating Container and the outer wall is created in which the liquid after leaving of the container. 3. Device according to claim 1 and 2, characterized in that the container wall is perforated like a sieve and its inside with a filter is occupied. 4. Device according to one of claims 1 to 3, characterized in that that means vorv are seen to contain a limited amount of fluid to be fed to the rotating container in any repetition. 5. Device according to claim 3 for measuring radioactive contamination of liquids and gases, characterized in that space within the drain a top or bottom with the v Impeller connected to the outer wall of the rotating container creates a pressure gradient. Documents considered: German Auslegeschrift No. 1,023,530; Nuclear Science Abstracts, Vol. 11, 1957, No. 6A, p. 377, Ref. No. 3477.