DD201514A1 - ARRANGEMENT FOR MEASURING TEMPORARILY HAZARDOUS HUMIDITY DISTRIBUTIONS - Google Patents

Abstract

The invention relates to an arrangement for the measurement of local moisture distributions in one or two dimensions in the yardstick, the rapid changes in time (in the second to hour range) are subjected. It can therefore be used in a wide variety of fields. The arrangement consists of neutron source and detector and the required electronic equipment and is characterized in that as a neutron source relative to the detector movable source or multiple sources are used at suitable distances from each other in a stationary arrangement, while using as a position-sensitive Neutronenzaehlrohre suitable length or so-called detector shields become. From the amplitude of the Zaehlrohrimpulse the detection site and from the number of pulses per unit time of the moisture content can be determined. Fig. 1

Description

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Inventor; Prof. Dr. so. nat. Dr. Hartraut Baumbach Doz. Adam Kazlmierski OA Tadeusz Lewandowski Wolfgang Riedel

Arrangement for the measurement of temporally rapidly variable local diffusivity distributions

Field of application of the invention

The invention relates to an arrangement for measuring local humidity distributions in one or two dimensions on a scale of meters which are subject to rapid changes (in the second to hour range) with respect to changes in humidity in thick concrete walls, for example real or simulated Disaster conditions, eg in nuclear power plant containment, "in the reconstruction of old buildings (in housing, in industrial buildings, monuments), in the assessment of the permeability of dykes, in dams, in the assessment of moisture distribution in silos and in containers (in the Construction materials production, in construction, in the food industry, etc.).

Characteristic of the known technical solutions

When passing fast neutrons through matter, their moderation takes place. H. AV braking due to scattering of atomic nuclei. The smaller the mass of atomic nuclei, the stronger the neutrons are scattered. The largest braking effect therefore have the atomic nuclei of hydrogen. By far, neutron scattering outweighs all possible ones

λ Q CC I) ^ QO λ o. U K. Ci I! Λ Ο

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Neutron trapping processes, the number of decelerated neutrons is a measure of the hydrogen content of the medium. If the hydrogen is hydrogenated, or at least most of the hydrogen is in the form of water, the moisture content can be measured directly (eg Couchat, T., Mesure Neutronique de l'Humidite des Sols, Dissertation .University of Toulouse, 1974).

The "known neutron moisture analyzers basically contain a source of fast neutrons (usually in a corresponding shielding), a detector for slow neutrons and the necessary electronics for supplying the detector or for processing the measurement signal (IAEA-Technical Report Series Uo. 112," Neutron Moisture Gauges ", Vienna 1970, IAEA-Technical Report Series No. 130," Commercial portable gauges ... ", Vienna 1970) Most come so-called isotope neutron sources, ie mixtures of a radionuclide and beryllium powder (Ra / Be, Airt / Be , Pu / Be) and spontaneously splitting nuclides (Cf-252) are used as slow neutron detectors are filled with boron trifluoride or helium-3 gas meters or correspondingly modified (eg with Lithi to -6) scintillation counter.

Since the detector registers all incident slow neutrons regardless of their direction of incidence, the resolution of the layer is low. To improve this, the detector is alternately surrounded by cadmium disks and aluminum disks. In this arrangement, diagonally incident neutrons do not reach the detector because they are absorbed by the cadmium disks (A. Trost, "Moisture Measurement with Neutrons ¹¹ , issue Euroisotop 12 (1966)).

The known moisture meter with neutron source do not allow statements about the moisture distribution in Zentlraeter- or in the meter range (in the latter case repeated measurements are erforderlioh), and in particular no detection

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of dynamic changes in the local moisture distribution in seconds and minutes.

Object of the invention

It is the object of the invention, the temporal change of local moisture distributions, z. B »in case of moisture migration, moisture transport or condensation formation.

Explanation of the essence of the invention

The invention has for its object to provide an arrangement for measuring moisture by means of neutrons, can be measured and registered with the spatial resolution of several millimeters with the zeitliohe changes in the second to hour range of local moisture distributions in the centimeter to meter range.

The inventive arrangement for measuring temporally rapidly varying local Feuohtigkeitsverteilungen using neutrons consists of neutron source and detector and is characterized in that the neutron source either a relative to the detector movable neutron source or several identical sources at appropriate distances in a stationary arrangement or multiple sources of different neutron flux density in an appropriate geometry can also be used in a stationary arrangement, while the position-sensitive neutron counter tubes of suitable length are used as the detector. However, multiple detectors are also possible. Furthermore, from a suitable geometric arrangement, for. B. of parallel counter tubes, a detector plate for the simultaneous detection of changes in humidity in two dimensions arise.

The arrangement has the necessary electronic equipment. For one-sided operation of psi-sensitive counter tubes, a unit of preamplifier,

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Main amplifier, high voltage part and memory, "used in two - sided operation a unit of preamplifier, main amplifier, high voltage part, totalizer, coincidence stage and memory or preamplifier, main amplifier, high voltage part, totalizer, divider, coincidence stage and memory quantitative assignment to moisture distribution simplified · In the case of multiple detectors, suitable known electronic matrices should be used ·

The simplification of electronic equipment, eg. B. by waiving divisional or divisional and adder, leads to increased effort in the interpretation of the measurement results ·

Measurements with the arrangements described can be carried out both continuously and discontinuously with respect to location and time. In order to map the distribution of thermal neutrons onto the detector, it is possible to work with or without collimators. With the aid of the arrangements described, it is possible, after the transmission, backscattering The advantage of the invention is that temporal changes in the second to hour range of local moisture distributions in the centimeter to meter range can be measured and registered.

embodiment

FIG. 1 shows the measuring scheme with an arrangement according to the invention and FIG. 2 shows the electronic block diagram "

The arrangement consists of five Californium-252 neutron sources 1, a position sensitive counter tube 2 of 1.5 m length and electronic equipment from high voltage power supply 5, two preamplifiers 3, two main amplifiers 4, a summing stage 6, a discriminator 7

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a coincidence stage 8 and an analyzer 9.

With the help of this arrangement, the distribution of Pale in a concrete slab 10, the moisture distribution changes in one-sided heating to be detected. For this purpose, two channels 11 are provided or attached in this concrete slab 10. While in the one channel 11, the five neutron sources 1 are introduced at gleiohen distances from each other, the position sensitive counter tube 2 is placed in the other channel 11 · On the counter tube 2 are on both sides · stromempflndliohe preamplifier 3 and spectrometric main amplifier 4 (total gain about 10) and a high voltage source 5 is connected. From the measuring arrangement, the temporal change of the moisture distribution in the space 12 zwisohen the two channels 11 is detected. The resulting in the counter tube pulses whose amplitude contains the information on the detection site, while the number of pulses per unit time provides the information about the moisture content, naoh the gain also go through summing and dividing into a Vielkanalanalysatorspeicher. The channel position is the location information and the channel content is assigned to the moisture content.

The memory contents may be cyclic or as needed to another, e.g. As magnetic tape or magnetic disk storage, are retrieved and is available for registration of a new measurement of the distribution of pests available. The recall of the memory contents can take place every second or hourly.

Claims (4)

- ⁶ - 233375 3 invention claim 1 .. Arrangement for measuring temporally rapidly changing local moisture distributions by means of neutrons, "consisting of neutron source, detector and electronic equipment, characterized in that as a neutron source (1) either one relative to the detector (2) movable source or multiple sources at appropriate distances from each other are used in a stationary arrangement, while as a detector (2) position-sensitive neutron counter tubes of suitable length or detector shields are used. 2. Arrangement according to item 1, characterized in that as a neutron detector (2) multiple detectors are used, which are arranged in 2 or 3 dimensions. 3. Arrangement according to item 1, characterized in that in addition collimators are used, 4. arrangement naoh point -1, characterized in that the position-sensitive Neutronenzählrohr (2) of suitable length "on both sides preamplifier (3) and main amplifier (4) and to this summer (6), coincidence stage (8) and memory or summer (6 ), Divider, coincidence stage (8) and memory are connected. For this 1 page drawings