JPS58219445A - Method of and apparatus for measuring percentage of moisture content by gamma ray - Google Patents

Abstract

PURPOSE:To expedite measurement by a method wherein gamma and neutron rays being allowed to have the same transmittance are detected through a specimen and converted into electrical signals before being subjected to arithmetic computation. CONSTITUTION:Sources 12, 14 of neutron and gamma rays are buried at preselected intervals in a controller 16 being freely slid in parallel with a specimen 10, whereas neutron and gamma ray detectors 18, 20 are provided at such a position that lines connecting the sources 12, 14 of the rays and the opposite ones cross each other through the specimen 10, the detector being further connected to an arithmetic unit 22. In the unit 22, a preset counter 24 is used to count the signals of the detector 20 and, when it has stopped, a counter 26 counting the signals of the detector 18 is stopped. Then the outputs of the counters 24, 26 are applied to an arithmetic circuit 28 to obtain the percentage of moisture content and density of the specimen 10 by computation. Thus, by equalizing the transmittance from the sources 12, 14 of the rays with the controller 16, the influence of variation in density can be automatically regulated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method and apparatus for measuring water content using radiation, and in particular, a method and apparatus for measuring water content using radiation, in particular, a method and apparatus for measuring water content using radiation, in particular, a method and apparatus for measuring water content using radiation, in which the amount of transmission of neutrons irradiated to a sample and the water content in the sample are 1.
This invention relates to improvements in a method and device for measuring water content using radiation that utilizes the fact that there is a one-to-one relationship.

Conventionally, the fast neutron transmission type utilizes the fact that the scattering cross section of hydrogen for fast neutrons is significantly larger than that of other elements, and uses the relationship that the amount of neutrons that pass through the sample depends on the water content in the sample. moisture meters are known. The measurement principle of such a conventional water content measuring method and device is outlined as follows.

The total cross-sectional area of fast neutrons, including scattering and absorption, is almost the same for elements other than hydrogen. Even if the composition of the sample other than hydrogen changes, the amount of neutron transmission does not change. If there is water in the sample, fast neutrons are scattered by hydrogen, which has a large cross section, and the amount of transmitted neutrons decreases significantly.

Therefore, by measuring the transmitted neutron beam intensity, the water content in the sample can be measured. However, the amount of fast neutron transmission changes even when the sample's density other than water, that is, the dry density, changes. Therefore, in order to accurately measure the sample's water content, other methods must be used to determine the sample's density. It is necessary to find and correct ○
However, in such a method, the correction procedure is complicated, and in conventional methods and devices, the above correction procedure is avoided by making the sample density constant, and as a result, the sample density is There was a drawback that it was not possible to automatically correct for changes in the amount of fast neutron transmission due to changes in density.

The present invention was made in view of such conventional problems,
The purpose of this method is to automatically correct changes in the amount of fast neutron transmission due to changes in sample density, and to measure the water content of a sample accurately and quickly regardless of changes in sample density. and equipment.

In order to achieve the above object, the method of the present invention detects the intensity of the neutron beam transmitted through the sample from the incident neutron beam i to the sample, converts it into a predetermined electric signal, and outputs the electric signal. In the method of measuring the water content of a sample from signal 2, gamma rays are incident on the sample, the transmittance of gamma rays and neutron rays in this sample are set equal, and the intensity of gamma rays passing through this sample is Detecting and converting this into a predetermined electrical signal and outputting it in steps 1 to 1, and calculating the water content of the sample by performing predetermined arithmetic processing on the electrical signal related to the gamma ray and the electrical signal related to the neutron beam. It is characterized by

In the present invention, it is preferable that the transmittance of neutron beams and gamma rays in the sample can be easily adjusted as necessary.

The apparatus of the present invention is equipped with a neutron ray source and a gamma ray source that inject neutron rays and gamma rays into a sample, and detects the intensity of neutron rays and gamma rays that pass through the sample.
, 7 A neutron beam detector and a gamma ray detector are provided to convert the pulse signals into pulse signals and output them, and each of the above-mentioned rays is arranged in a direction in which the transmission path length of at least one of the transmitted neutron beams and the transmitted gamma rays in the sample can be adjusted. at least one of the two detectors is movably formed, and further provided with a first counter and a second counter for counting pulse signals of each of the detectors, and The present invention is characterized in that an arithmetic circuit is provided for calculating the water content of the sample by performing predetermined arithmetic processing on the output of the counter.

Still, in the present invention, it is preferable to use a device that does not require a mechanical adjustment part because it is less likely to fail and can be made smaller.

The apparatus of the present invention is equipped with a neutron ray source and a gamma ray source that inject neutron rays and gamma rays into a sample, detects the neutron ray intensity and gamma ray intensity that pass through the sample, and converts them into pulse signals. A neutron beam detector and a gamma ray detector are provided, and a first counter and a second counter for counting pulse signals are provided at the output stage of each of these detectors.
A discriminator is provided at the input stage of at least one of the first and second counters to discriminate the energy of the detection pulse and adjust the transmittance of neutron beams and gamma rays in the sample. The present invention is characterized in that it further includes an arithmetic circuit that performs predetermined arithmetic processing on the outputs of the first and second counters to calculate the water content of the sample.

Next, preferred embodiments of the present invention will be described based on the drawings.

First, the method of measuring water content using radiation according to the present invention will be explained.

When a fast neutron beam is incident on a sample from a neutron source, the neutron beam intensity N, (ρ) transmitted through the sample and detected by a neutron beam detector is given by the following equation.

Here, N n (/'): Transmitted neutron beam intensity (n7cm2/
imin).

ρ: Water content (g/cm3).

■o: Neutron emission rate (n/rnin).

Xo: Source-detector distance (crn).

dn: Transmission distance in the sample (Cm).

D: Dry sample density (g/cm3).

ΣC: Total cross-sectional area per test stick sample (am2/g).

ΣW: Total cross-sectional area per gram of water (cm2/g).

Both relate to neutron beams of constant energy.

Further, when gamma rays are incident on a sample from a gamma ray source, the gamma ray intensity N, (ρ) transmitted through the sample and detected by a gamma ray detector is given by the following equation.

Here, Nr (ρ): Transmitted Gaffour-r ray intensity (r/cm27m1n
).

■=Gamma ray emission rate (17mln).

7- X-ray source-detector distance (am).

d: Transmission distance in the sample (cm).

μC: Absorption coefficient of sample (0m27g).

Absorption coefficient of µp water (cm2/g).

Both relate to gamma rays of constant energy.

Then, when calculating the ratio N, (ρVNr(ρ)) between the transmitted neutron beam intensity N, (ρ) and the transmitted gamma ray intensity N, (ρ), ・e−(Σw'n−μwdγ)ρ・(3) becomes.

Therefore, by setting the transmittance of neutron beams and gamma rays in the sample to be equal and solving this equation (5), the water content ρ of the sample can be obtained regardless of the density.

Here, the conditional expression Σcan=/jcdγ is set as follows. First, fast neutron beam and 8
- Σ if the energy of the gamma rays is constant.

and μ6 are constant, so the transmission distance d of neutron and gamma rays in the sample. , dr, the condition Σc(in-μ.d) is set.If the transmission distances d, , d, of the neutron beam and gamma ray in the sample are constant, the neutron beam By switching the energy of Σ and gamma rays, the total cross-sectional area Σ6 and the absorption coefficient μ are adjusted, and Σ, d, = I
It is also possible to set a condition such that tod.

The ratio N of the transmitted neutron beam and gamma ray intensities is still expressed by the above equation (5). (ρ)/Nr(ρ) is Σcan-μcd
, can be easily obtained with an electric circuit using a preset counter. Generally, a neutron beam detector and a gamma ray detector output a pulse signal proportional to the intensity of the detected transmitted neutron beam and the transmitted gamma ray intensity. Therefore, when this pulse signal is counted by each counter, the ratio of the counting rate C0(ρ)/Cr(ρ) and the (
The following proportional relationship holds between N, (ρ)/N, and (ρ) shown in equation 5).

Here, co(p) is the counting rate of transmitted neutron beam, C
, (ρ) is the counting rate of transmitted gamma rays. Then, if a preset counter is used as a counter to count the Norculus signal related to the transmitted gamma ray intensity, the measurement time T is as follows: T=Cp/Cy(ρ) (7
). Here, Cp is a preset count value. During the measurement time T of this preset counter, when the noise signal of the neutron beam detector is counted by another counter, the counted value C8 is as follows: C(1=Cn(/') ''T...
...The relationship shown in (8) is established, and if the proportionality coefficient is calculated in advance, N, (ρVNr(p)) can be calculated.

FIG. 1 is a block diagram showing a preferred embodiment of the radiation-based water content measuring device of the present invention. In FIG. Fast neutron beams and gamma rays are incident.

Each of the radiation sources 12 and 14 is embedded at a predetermined interval in an adjustment rod 16 that is slidably supported substantially parallel to the sample 10. Also, the radiation source 12 is connected through the sample 10.
, 14 and respective radiation sources 12, 14 on the opposite side cross each other, a neutron beam detector 18 and a gamma ray detector 20 are arranged at a predetermined interval. 22 is an arithmetic unit, and a preset counter 24 as a first counter provided therein serves as a gamma ray detector 20.
This preset counter 2 counts the pulse signals of
The pulse signal of the neutron beam detector 18 is counted by a counter 26 as a second counter which stops counting at the same time as the number 4 counts up. Then, the outputs of each counter 24 and 26 are input to the arithmetic circuit 28. Based on the inputs from the counters 24 and 26, this calculation circuit 28 calculates the equation (5) above using the water content ρ as an unknown quantity, and calculates the sample 10 from the measurement time T shown in the equation (7). Calculate the density.

11- The embodiment of the present invention has the above configuration, and its operation will be explained below.

In this example, since the energies of the neutron beams and gamma rays incident on the sample 10 from the radiation sources 12, 14 are constant, the cross-sectional area Σ per 1001 g of the sample. and absorption coefficient μ. is almost constant. Therefore, the conditional expression shown in equation (4) is the transmission distance d of the neutron beam in the sample 10. and gamma ray transmission distance d.

can be adjusted by sliding the adjustment rod 16. That is, the values of the gamma ray and neutron ray transmittances μcdr and Σcdn in the sample 10 are determined by sliding the adjustment rod 16, d and d.

By adjusting the value of Σcdn-μCdr.

After making the above adjustments, when neutron beams and gamma rays are incident on the sample 10 from the radiation source 12.14, each detector 1
8.20, the neutron beam intensity N given by equation (1). ((b) and gamma ray intensity N given by equation (2), neutron rays and gamma rays are detected,
Each strength N. ( ) and Nr (→ This is a preset counter set to CP and gamma ray detector 2.
When the count value of the pulse signal output from 0 reaches Cp, the measurement time T is output and a stop signal is input to the other counter 26. The counter 26 stops counting the pulse signals input from the neutron beam detector 18 upon input of the stop signal. Then, the count value C6 of the counter 26 and the measurement time T of the counter 24 are inputted to the arithmetic circuit 28, and the sample 10 is
In addition to calculating the density of
r(ρ) is calculated, and from this value, the water content ρ of sample 10 is calculated based on equation (5). The density and water content ρ thus determined in [2] are displayed by a display mechanism (not shown).

In this embodiment, the reason why the radiation sources 12, 14 or the detectors 16, 18 are arranged at predetermined intervals is to make the overall arrangement compact. However, if it is necessary to effectively shield each radiation source 12, 14, it is also possible to arrange each radiation source 12, 14 together, and it is still possible to provide appropriate radiation from the neutron radiation source 12 in addition to neutron radiation. If energetic gamma rays are being emitted at the same time, there is no need to provide a separate gamma ray source 14, and the neutron source 12 can also function as a gamma ray source. In this case, half-life correction of the radiation source 12 can be automatically performed.

In this embodiment, two detectors are provided to detect neutron rays and gamma rays, but the present invention is not limited to this. It is also possible to electrically distinguish these into neutron beams and gamma rays in a subsequent circuit. In this case, the radiation sources 12 and 14 must be placed apart from each other by a predetermined distance.

In addition, in this embodiment, the pulse signal of the gamma ray detector is counted by a preset counter, and the pulse signal of the neutron beam detector is counted by a counter that reduces the count to medium using the count amplifier of the preset counter. Conversely, the pulse signals of the neutron beam detector may be counted by a preset counter, and the pulse signals of the gamma ray detector may be counted by a normal counter.

FIG. 2 is a block diagram showing another embodiment of the radiation-based moisture content measuring device of the present invention. The feature of this fruitful example is that, unlike the embodiment shown in FIG. and absorption coefficient μ.

The purpose of this is to set the conditional expression shown in equation (4), that is, the measurement condition Σcdn=μcdr by adjusting .Next, the configuration of this embodiment will be described. Incidentally, members corresponding to those in the embodiment shown in FIG. 1 are given the same reference numerals and their explanations will be omitted. Generally, the neutron beam source 12 emits neutron beams with different energies, and similarly the gamma ray source 14 emits gamma rays with two or more different energies.

Therefore, if the energy of the neutron beam and gamma ray detected by the detectors 18 and 20 is discriminated and used for measurement, sample 1
Total cross-sectional area Σ per 001g. and absorption coefficient μ. The value of measurement condition Σ can be adjusted arbitrarily. do-μ. d,
can be set electrically. 30.32 is a discriminator provided at the output stage of the detector 18.20 for this purpose, which discriminates the energy of each pulse signal output from each detector 18.20 and inputs it to each counter 24.26. .

With the above configuration, in this embodiment, prior to measurement, the cut energy level of each discriminator 30 and 32 is appropriately set, and the total cross-sectional area Σ is calculated. and absorption coefficient μ. is set so that it satisfies the second condition (4), that is, Σcdn−μcd. Thereafter, the water content ρ and density of the sample 10 can be measured in the same manner as in the embodiment shown in FIG. 1 above.

In this embodiment, as in the previous embodiment, it is also possible to detect both neutron rays and gamma rays with one detector, and distinguish them into neutron rays and gamma rays in a subsequent circuit. However, unlike the previous embodiment, it is not necessary to install the radiation sources 12, 14 apart.

Further, in this embodiment, the discriminator is provided in front of both the counters 24 and 26, but the discriminator is not limited to this, and may be provided only in the front of at least one of the counters 24 and 26. O As described above, in this example, the transmittances Σcdn and μcd of neutron beams and gamma rays in the sample 10,
Since the structure is such that the radiation sources 12 and 14 can be electrically adjusted, there are fewer failures than in the previous embodiment, and the shape can be made more compact, and each radiation source 12 and 14 can also be fixed in one place. , its shielding becomes easy.

As described above, according to the present invention, when measuring the water content of a sample using neutron beams, gamma rays are used to automatically correct changes in the amount of neutron beam transmission due to changes in the density of the sample,
The water content of a sample can be measured accurately and quickly. As a result, the present invention can easily measure the moisture content of samples with rapid density changes, such as powder and granules being transported on a belt conveyor. It can also be widely used for controlling the moisture content of raw materials such as ore and coke in steel plants.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the radiation-based water content measuring device of the present invention, and FIG. 2 is a block diagram showing another embodiment. The same members in each figure are given the same reference numerals, 10 is the sample, 12
is a neutron source, 14 is a gamma ray source, 16 is an adjustment rod, 18
is a neutron beam detector, 20 is a gamma ray detector, and 24 is a first
26 is a second counter, 28 is an arithmetic circuit,
30.32 is a discriminator. Applicant Aloka Co., Ltd. 19- Figure 1 Figure 2

Claims (4)

[Claims] (1) A method of injecting a neutron beam into a sample, detecting the intensity of the neutron beam passing through the sample, converting it into a predetermined electrical signal and outputting it, and measuring the water content of the sample from this electrical signal. In this method, gamma rays are incident on the sample, the transmittance of gamma rays and neutron rays in this sample is set to be equal, and the intensity of gamma rays passing through this sample is detected, which is converted into a predetermined electrical signal and output. A method for measuring water content using radiation, characterized in that the water content of the sample is calculated by performing predetermined arithmetic processing on the electric signal related to the gamma ray and the electric signal related to the neutron beam. (2) A neutron ray source and a gamma ray source that inject neutron rays and gamma rays into the sample are provided, and the neutron ray intensity and gamma ray intensity transmitted through the sample are detected and converted into pulse signals and output. A radiation detector and a gamma ray detector are provided, and at least one of the radiation sources or the detectors is arranged in a direction in which the transmission path length of at least one of the transmitted neutron rays and the transmitted gamma rays in the sample can be adjusted. A first counter and a second counter are provided to be movable and count the pulse signals of each of the detectors, and the outputs of the first and second counters are subjected to predetermined arithmetic processing to calculate the value of the sample. A radiation-based water content measuring device 0 characterized by being provided with an arithmetic circuit for calculating water content. (3) In the apparatus described in claim (2), the neutron source and the gamma ray source are installed at a predetermined interval on an adjustment rod, and the adjustment rod is formed to be slidable in a direction parallel to the sample. A radiation-based water content measurement device characterized by: (4) Provide a neutron ray source and a gamma ray source that inject neutron rays and gamma rays into the sample, detect the neutron ray intensity and gamma ray intensity that pass through the sample, and convert this into a pulse signal and output it. A neutron beam detector and a gamma ray detector are provided, and the output stage of each of these detectors is provided with a first counter and a second counter for counting pulse signals, and at least one of the first and second counters is provided. A discriminator is provided for discriminating the energy of the detection pulse and adjusting the transmittance of neutron beams or gamma rays in the sample at the input stage of the input stage, and further, predetermined arithmetic processing is performed on the outputs of the first and second counters. 1. An apparatus for measuring moisture content using radiation, characterized in that it is provided with an arithmetic circuit for calculating the moisture content of the sample by applying radiation to the sample.