JPH0784088A - Radiation measuring system - Google Patents

Abstract

PURPOSE:To reduce stray capacitance between cables without affecting the detection signal and improve the resistance to noise in wide frequency range. CONSTITUTION:In a radiation measuring system for measuring radiation dose by sending the detection signal with a radiation detector detecting radiation through a cable to a preamplifier, provided are an annular magnetic core 25 wound with plural turns number of cables so as to eliminate noise mixing in the cable 5 and arranged between the preamplifier and the radiation detector and cable arrangement parts 27, 28 to arrange the cable 5 apart from each other so as to reduce the stray capacitance between the adjacent cables 5 wound around the annular magnetic core 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation measuring system for measuring radiation by a weak detection signal sent from a radiation detector in, for example, a nuclear power plant. Radiation measurement system that can improve the reliability of

[0002]

2. Description of the Related Art For example, in a nuclear power plant requiring radiation measurement in a pressure vessel for protection of a nuclear reactor, a detection signal from a radiation detector arranged in the reactor pressure vessel is amplified by a preamplifier. However, radiation measurement systems that measure radiation based on this amplified signal are widely used.

FIG. 9 is a schematic diagram showing the structure of this type of radiation measuring system. In this radiation measuring system, a radiation detector 2 installed in a reactor pressure vessel 1 detects radiation and generates a current pulse, and the current pulse is used as a detection signal to attach a penetration portion to a reactor containment vessel 3. It is delivered through a coaxial cable 5 passing through 4.

Further, this detection signal is sent to a preamplifier 9 in a preamplifier board 8 via a common mode choke coil 7 formed by winding a coaxial cable 5 around a toroidal magnetic core 6. The toroidal magnetic core 6 is
Here, Mn-based ferrite having a large initial magnetic permeability up to several 100 kHz is used.

The preamplifier 9 voltage-converts and amplifies this detection signal, and sends the amplified signal to the signal processing unit 12 in the central control room 11 through the coaxial cable 5 housed in the metal conduit 10.

The signal processing unit 12 obtains the radiation dose in the reactor pressure vessel 1 by performing pulse counting and effective voltage measurement of this amplified signal. Since such a radiation measuring system has a small detection signal, various measures are taken against external noise.

For example, in signal transmission between the radiation detector 2 and the signal processing unit 12, every several coaxial cables 5 are housed in a metal conduit tube 10 to protect them from flying objects and external noise. Further, the grounding is one-point grounding in the signal processing unit 12 in the central control room 11.

Further, among the external noises, the one whose frequency band matches the frequency band measured by the radiation detector 2 cannot be eliminated by the filtering process, so that the common mode choke coil 7 prevents the mixing. ing.

[0009]

However, in the radiation measuring system as described above, the coaxial cables 5 wound around the toroidal magnetic core 6 by the common mode choke coil 7 are close to each other and float between the coaxial cables 5. There is a problem that capacitance is generated and the impedance against high frequency noise is lowered.

Since the stray capacitance is proportional to the square of the number of windings, there is a problem that if the number of windings is reduced so as to reduce the stray capacitance, the self-inductance also decreases.

On the other hand, if the winding radius of the coaxial cable 5 is reduced in order to reduce the stray capacitance, the leakage magnetic flux is reduced and the impedance for high frequencies can be improved. However, if the winding radius of the coaxial cable 5 is made extremely small, the characteristic inductance of the coaxial cable 5 and the mutual inductance between the core wire and the shield become unbalanced, and there is a problem that the detection signal is adversely affected.

The toroidal magnetic core 6 of the common mode choke coil 7 has a frequency characteristic corresponding to the magnetic material thereof. For example, here, the magnetic permeability of the magnetic core is several hundred KH.
The one that attenuates at a high frequency of z or more is used. That is, there is a problem that it is difficult to form the common mode choke coil 7 that removes noise over a wide frequency range in a narrow space of the reactor containment vessel 3.

The present invention has been made in consideration of the above circumstances, and radiation measurement which can reduce the stray capacitance generated between cables and improve the resistance to noise in a wide frequency range without affecting the detection signal. The purpose is to provide a system.

[0014]

According to a first aspect of the invention, a radiation detector for detecting radiation sends the detection signal to a preamplifier via a cable to measure the dose of the radiation. In the radiation measurement system,
Disposed between the preamplifier and the radiation detector,
The cables are separated from each other so as to reduce stray capacitance generated between the annular magnetic core around which the cable is wound a plurality of times so as to eliminate noise mixed in the cable and adjacent cables wound around the annular magnetic core. It is a radiation measuring system provided with the cable arrangement member which is made to arrange.

The invention according to claim 2 is a radiation measuring system for measuring a dose of the radiation by a radiation detector for detecting the radiation sending the detection signal to a preamplifier through a cable. A first annular magnetic core disposed between the preamplifier and the radiation detector and wound around the cable a plurality of times so as to eliminate noise mixed in the cable; and the first annular magnetic core. Is a magnetic material having different frequency characteristics, is arranged in series with the first annular magnetic core between the preamplifier and the radiation detector, and has a second annular magnetic core around which the cable is wound a plurality of times. , The cables are arranged apart from each other so as to reduce the stray capacitance generated between the cables wound around the first and second annular magnetic cores and close to each other. A radiation measuring system comprising a number of cable locating member.

[0016]

Therefore, in the invention corresponding to claim 1, by taking the above-mentioned means, the noise mixed in the cable is eliminated in the annular magnetic core arranged between the preamplifier and the radiation detector. As described above, the cable is wound a plurality of times, and the cable arranging member is wound around the annular magnetic core so as to reduce the stray capacitance generated between the adjacent cables. The stray capacitance generated between the cables can be reduced and the resistance to noise can be improved without affecting.

Further, in the invention according to claim 2, in the first annular magnetic core arranged between the preamplifier and the radiation detector, the cable is wound a plurality of times so as to eliminate noise mixed in the cable. On the other hand, a second annular magnetic core made of a magnetic material having a frequency characteristic different from that of the first annular magnetic core and arranged in series with the first annular magnetic core between the preamplifier and the radiation detector. In the core, the cable is wound a plurality of times, and the plurality of cable arranging members include the first and second cables.
Since the cables are arranged so as to be spaced from each other so as to reduce the stray capacitance generated between the cables which are respectively wound around the annular magnetic core of (1), resistance to noise in a wider frequency range can be obtained in addition to the function of claim 1. Can be improved.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a schematic diagram showing a configuration of a common mode choke coil applied to a radiation measuring system according to a first embodiment of the present invention, and FIG. 2 is a schematic diagram showing a peripheral configuration of the common mode choke coil. 9, the same parts as those in FIG. 9 are designated by the same reference numerals, and detailed description thereof will be omitted. Only different parts will be described here.

That is, the system of this embodiment reduces stray capacitance generated in the common mode choke coil and improves resistance to external noise. Specifically, the coaxial cable 5 of the common mode choke coil is used.
The structure is provided with a spacer that separates the coaxial cables 5 so as to reduce the stray capacitance generated between them.

In the common mode choke coil 21, a magnetic core storage box 22 arranged before the preamplifier 9 and connected to the preamplifier board 8 via a metal conduit 10 is a reactor containment vessel (not shown). 3 is attached to the side wall.

A plate-like spacer 23 is attached to the bottom of the magnetic core storage box 22. The cylindrical spacer 24 arranged on the plate spacer 23 is a toroidal magnetic core (annular magnetic core).
25 is provided on the inner side, and the outer side is fixed on the plate-like spacer 23 by a U-shaped spacer 26.

The toroidal magnetic core 25 is inserted with rod-shaped spacers 27 having a plurality of holes 27a formed in the longitudinal direction at substantially equal intervals. Further, as the magnetic material of the toroidal magnetic core, Mn-based ferrite that maintains a large initial magnetic permeability up to several 100 kHz is used.

Here, the coaxial cable 5 connected to the radiation detector 2 passes through each hole 27a of the rod-shaped spacer 27 and the outside of the U-shaped spacer 26, and the toroidal magnetic core 2 is passed.
5 is wound several times and is connected to the preamplifier 9 in the preamplifier board 8 through the metal conduit 10. The winding diameter of the coaxial cable 5 is 20 cm so as not to affect the detection signal sent from the radiation detector 2.
That is all.

Further, on the outside of the U-shaped spacer 26, there are arranged parabolic spacers 28 having ring portions 28a through which the coaxial cable 5 can pass at substantially equal intervals, and the parabolic spacer 28 connects each coaxial cable to each ring. The parts 28a are individually passed through and arranged in a fan shape. In addition, this parabolic spacer 2
8 is made to have a small cross-sectional area.

The rod-shaped spacer 27 and the parabolic spacer 28 constitute a cable arranging member. Next, the operation of the radiation measurement system configured as above will be described.

First, as described above, the radiation detector 2 sends the detection signal to the preamplifier 9 via the common mode choke coil 21. The preamplifier 9 amplifies the detection signal and sends the amplified signal to the signal processing unit 12, and the signal processing unit 12 calculates the radiation dose in the reactor pressure vessel 1 based on the amplified signal.

In this state, it is assumed that external noise enters the coaxial cable 5 between the radiation detector 2 and the common mode choke coil 21. However, as mentioned above,
In the common mode choke coil 21, since each coaxial cable 5 is separated by the rod-shaped spacer 27 and the parabolic spacer 28, only a small stray capacitance is generated between the coaxial cables 5, and a high impedance against high frequency noise can be maintained. ing.

Therefore, the mixed external noise is guided to the coaxial cable 5, reaches the common mode choke coil 21, and is erased by the high impedance of the common mode choke coil 21. The common mode choke coil 21 can eliminate high frequency noise up to several 100 kHz corresponding to the magnetic material of the toroidal magnetic core 25.

As described above, according to the first embodiment, in the toroidal magnetic core 25 arranged between the preamplifier 9 and the radiation detector 2, the noise mixed in the coaxial cable 5 is eliminated. The coaxial cable 5 is wound plural times, and the rod-shaped spacer 27 and the parabolic spacer 28 are used.
However, since the coaxial cables 5 are arranged so as to be separated from each other so as to reduce the stray capacitance generated between the coaxial cables 5 that are wound around the toroidal magnetic core 25 and are adjacent to each other, the cable is not affected by the detection signal. It is possible to reduce the stray capacitance generated between them and improve the resistance to noise, and thus improve the reliability of radiation measurement.

According to the first embodiment, the toroidal magnetic core 25 and the coaxial cable 5 around the magnetic core 25 are fixed by the U-shaped spacer 26 and the parabolic spacer 28. Even in a relatively narrow space in 3, the toroidal magnetic core 25 can be firmly provided.

Next, a radiation measuring system according to the second embodiment of the present invention will be described. FIG. 3 is a schematic diagram showing a common mode choke coil applied to this radiation measuring system and its peripheral configuration. The same parts as those in FIGS. 1 and 2 are designated by the same reference numerals and detailed description thereof will be omitted. Now, only different parts will be described.

That is, the system of this embodiment facilitates the routing of the coaxial cable 5 after it is wound around the toroidal magnetic core 25. Specifically, the magnetic core storage box 22 and the preamplifier board are used. 8 and 8 are integrated.

Here, the magnetic core storage box 22 and the preamplifier board 8
Since the distance between them is minimized, the coaxial cable 5 wound around the toroidal magnetic core 25 can be easily routed.

As described above, according to the second embodiment, since the magnetic core housing box 22 and the preamplifier board 8 are integrated, the coaxial cable 5 after being wound around the toroidal magnetic core 25 can be easily manufactured. Can be routed to.

Next explained is a radiation measuring system according to the third embodiment of the invention. FIG. 4 is a schematic view showing a common mode choke coil applied to this radiation measuring system and its peripheral configuration. The same parts as those in FIGS. 1 and 2 are designated by the same reference numerals and detailed description thereof will be omitted. Now, only different parts will be described.

That is, the system of the present embodiment has a plurality of systems of common mode choke coils corresponding to a plurality of systems of radiation detectors 2. Specifically, the system is coaxial within the magnetic core storage box 22. Two toroidal magnetic cores 25 around which the cable 5 is wound are arranged side by side, and both toroidal magnetic cores 2 are arranged.
A magnetic shield plate 29 for shielding the magnetism is provided between the five.

Here, since the magnetic shield plate 29 shields the magnetism between the toroidal magnetic cores 25, magnetic coupling between the coaxial cables 5 of different systems is blocked and the propagation of noise to other systems is prevented. be able to.

As described above, according to the third embodiment, even when a plurality of detection systems are provided, the toroidal magnetic cores 25 corresponding to the respective systems are arranged in parallel and the magnetic cores 2 are provided.
Since the magnetic shield plate 29 is arranged between the five, the first
In addition to the effect of the embodiment, it is possible to prevent magnetic coupling between cables of different systems and prevent propagation of noise to other systems.

Next explained is a radiation measuring system according to the fourth embodiment of the invention. FIG. 5 is a schematic view showing a common mode choke coil applied to this radiation measurement system and its peripheral configuration. The same parts as those in FIG. 3 are designated by the same reference numerals and detailed description thereof will be omitted. Will be described only.

That is, the system of this embodiment does not require a mounting space for the common mode choke coil. Specifically, in contrast to the system shown in FIG. The toroidal magnetic core 25 around which the cable 5 is wound is arranged in the preamplifier board 8.

Since the toroidal magnetic core 25 is arranged in the preamplifier board 8, the magnetic core storage box 22 is mounted when the toroidal magnetic core 25 is arranged in the magnetic core storage box 22. Space is not required and a more compact structure can be realized.

As described above, according to the fourth embodiment, the toroidal magnetic core 25 is arranged in the preamplifier board 8 and the mounting space for the common mode choke coil 21 is not required. In addition to the effects of the example, a more compact structure can be realized.

Next explained is a radiation measuring system according to the fifth embodiment of the invention. FIG. 6 is a schematic diagram showing a common mode choke coil applied to this radiation measuring system and its peripheral configuration.
The same parts as the above are given the same reference numerals and detailed explanations thereof will be omitted, and only different parts will be described here, that is,
The system of the present embodiment facilitates the routing of the coaxial cable 5 from the radiation detector 2 to the toroidal magnetic core 25. Specifically, the magnetic core storage box 22 is replaced by the nuclear reactor containment vessel 3. It is configured to be connected to the penetrating portion 4 through a thick dustproof cylinder 30.

Here, since the magnetic core housing box 22 for housing the toroidal magnetic core 25 is arranged in the vicinity of the penetrating portion 4, the cable between the radiation detector 2 and the toroidal magnetic core 25 can be easily routed. be able to. In addition, the magnetic core storage box 22
Since the thick tube 30 between the and the through portion 4 can be thickened, the extra length of the coaxial cable 5 can be easily processed.

As described above, according to the fifth embodiment, since the magnetic core housing box 22 is arranged close to the penetrating portion 4 of the reactor containment vessel 3, the radiation detector 2 and the toroidal magnetic core 25 are arranged.
The coaxial cable 5 between and can be easily routed,
Therefore, the extra length of the coaxial cable 5 can be easily processed.

Next explained is a radiation measuring system according to the sixth embodiment of the invention. FIG. 7 is a schematic diagram showing a peripheral configuration of a common mode choke coil applied to this radiation measuring system. The same parts as those in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted. Only mention.

That is, the system of this embodiment is 1 MHz.
It is possible to reduce external noise having a frequency exceeding 0. Specifically, in addition to winding the coaxial cable 5 around the toroidal magnetic core 25, the coaxial cable 5 is wound in a loop with an air core. It is composed.

Here, since the common mode choke has a small self-inductance because it is an air core, when the external noise is high frequency noise exceeding 1 MHz, the noise can be reduced.

Further, in the case of noise having a frequency much higher than 1 MHz, the effect of the toroidal magnetic core 25 can hardly be expected, so that the common mode choke by the air core also reduces the noise almost in the same way as with the magnetic core. be able to.

As described above, according to the sixth embodiment, in addition to winding the coaxial cable 5 around the toroidal magnetic core 25, the coaxial cable is wound around the air core in a loop. In addition to the effects of the embodiment, 1 MHz
It is possible to reduce the noise having a frequency exceeding 0 without a toroidal magnetic core.

Next explained is a radiation measuring system according to the seventh embodiment of the invention. FIG. 8 is a schematic diagram showing a common mode choke coil applied to this radiation measuring system and its peripheral configuration. The same parts as those in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted. Will be described only.

That is, the system of this embodiment eliminates or reduces noise over a wide frequency range. Specifically, the toroidal magnetic core 25 shown in FIG.
On the other hand, this toroidal magnetic core 25 (first annular magnetic core)
Made of a magnetic material having a frequency characteristic different from that of the toroidal magnetic core 31 around which the coaxial cable 5 is wound plural times.
(Second annular magnetic core) is added in series. The common mode choke coil 32 having the added toroidal magnetic core 31 has a plurality of spacers (a plurality of cable arranging members) similarly to the common mode choke coil 21 shown in FIG. .

Here, the added toroidal magnetic core 31
Is, for example, Ni that maintains a small initial permeability up to several MHz.
Uses ferrite series. Therefore, as mentioned above,
Noise up to several hundred kHz can be erased by the common mode choke coil 21 using the Mn-based ferrite as the magnetic core 25, and noise up to several MHz can be reduced by the common mode choke coil using the Ni-based ferrite as the magnetic core 31. .

As described above, according to the seventh embodiment, since the common mode choke coils having the toroidal magnetic cores 25 and 31 having different frequency characteristics are combined in series, noise is eliminated or reduced over a wide frequency range. can do.

In the above first to seventh embodiments, the case where the toroidal magnetic cores 25 and 31 are used as the annular magnetic core has been described, but the present invention is not limited to this. Even with a structure using an annular magnetic core such as a racetrack type, the same effects can be obtained by implementing the present invention in the same manner.

In the fifth embodiment, the case where the magnetic core storage box 22 and the penetrating portion 4 are connected via the dustproof thick cylinder 30 has been described, but the present invention is not limited to this. Two
Even if the 2 and the penetrating portion 4 are directly connected or are connected via an electromagnetic shield such as a zipper tube, the same effects can be obtained by implementing the present invention in the same manner.

Further, in the seventh embodiment, the case where the Mn-based ferrite and the Ni-based ferrite are combined has been described, but the present invention is not limited to this, and the magnetic material A having a large initial permeability and poor high frequency characteristics, If it is combined with the magnetic material B having a small initial magnetic permeability and good high frequency characteristics, the present invention can be carried out in the same manner and the same effect can be obtained.

As the magnetic material A, it is possible to use metallic materials such as supermalloy, permalloy, and silicon steel which maintain a large initial magnetic permeability from several 10 kHz to several 100 kHz. Also, for example, Mn-Z
A magnetic material, such as n-type ferrite, that suppresses the generation of eddy currents due to its high electric resistance and can maintain the initial magnetic permeability of about 90% of the metal-based material up to several 100 kHz can be used.

On the other hand, as the magnetic material B, for example, Ni-
A magnetic material such as Zn-based ferrite or carbonyl iron dust, which has a higher resistance than Mn-Zn-based ferrite, further suppresses eddy currents and can maintain a small initial magnetic permeability up to a frequency band of several MHz can be used. is there.

Further, in the seventh embodiment, two toroidal magnetic cores 25 and 31 having different frequency characteristics are used.
However, the present invention is not limited to this, and three or more toroidal magnetic cores having different frequency characteristics are combined to realize a common mode choke coil having a desired frequency characteristic. However, the present invention can be similarly implemented to reduce noise in a wider frequency range. Further, it is possible to reduce the magnetic saturation that is generated by the common mode noise current and prevents the action as the common mode choke. In addition, the present invention can be modified in various ways without departing from the scope of the invention.

[0061]

As described above, according to the invention according to claim 1, in the annular magnetic core arranged between the preamplifier and the radiation detector, a plurality of cables are provided so as to eliminate noise mixed in the cables. Since the cable is wound around and the cable arranging member is wound around the annular magnetic core so as to reduce the stray capacitance generated between the adjacent cables, the cables are arranged so as to be separated from each other. It is possible to provide a radiation measurement system that can reduce stray capacitance generated between cables and improve noise immunity without supplying the cables.

According to the second aspect of the invention, in the first annular magnetic core arranged between the preamplifier and the radiation detector, the cable is wound a plurality of times so as to eliminate noise mixed in the cable. On the other hand, a second annular magnetic core made of a magnetic material having a frequency characteristic different from that of the first annular magnetic core and arranged in series with the first annular magnetic core between the preamplifier and the radiation detector. In the core, the cable is wound a plurality of times, and the plurality of cable arranging members include the first and second cables.
Since the cables are arranged so as to be spaced from each other so as to reduce the stray capacitance generated between the cables that are respectively wound around the annular magnetic cores, the noise of a wider frequency range can be obtained. It is possible to provide a radiation measurement system capable of improving resistance to radiation.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a common mode choke coil applied to a radiation measuring system according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a peripheral configuration of a common mode choke coil in the example.

FIG. 3 is a schematic diagram showing a common mode choke coil applied to a radiation measurement system according to a second embodiment of the present invention and a peripheral configuration thereof.

FIG. 4 is a schematic diagram showing a common mode choke coil applied to a radiation measurement system according to a third embodiment of the present invention and a peripheral configuration thereof.

FIG. 5 is a schematic diagram showing a common mode choke coil applied to a radiation measurement system according to a fourth embodiment of the present invention and a peripheral configuration thereof.

FIG. 6 is a schematic diagram showing a common mode choke coil applied to a radiation measurement system according to a fifth embodiment of the present invention and a peripheral configuration thereof.

FIG. 7 is a schematic diagram showing a peripheral configuration of a common mode choke coil applied to a radiation measuring system according to a sixth embodiment of the present invention.

FIG. 8 is a schematic diagram showing a common mode choke coil applied to a radiation measurement system according to a seventh embodiment of the present invention and a peripheral configuration thereof.

FIG. 9 is a schematic diagram showing the configuration of a conventional radiation measurement system.

[Explanation of symbols]

1 ... Reactor pressure vessel, 2 ... Radiation detector, 3 ... Reactor containment vessel, 4 ... Penetration part, 5 ... Coaxial cable, 8 ... Preamplifier board, 9 ... Preamplifier, 10 ... Metal conduit tube, 11 ... Central control room, 12 ... Signal processing unit 21, 32 ... Common mode choke coil, 22 ... Magnetic core storage box, 23 ... Plate spacer, 24 ... Cylindrical spacer, 25, 31 ... Toroidal magnetic core, 26 ... U-shaped spacer, 27 ... Rod-shaped spacer, 28 ... Parabolic spacer, 29 ... Magnetic shielding plate, 3
0 ... Thick tube.

Claims (2)

[Claims] 1. A radiation measuring system for measuring a dose of the radiation by a radiation detector for detecting the radiation sending the detection signal to a preamplifier through a cable, wherein the preamplifier and the radiation detection are provided. Placed between the vessels,
An annular magnetic core around which the cable is wound a plurality of times so as to eliminate noise mixed in the cable, and the cables are separated from each other so as to reduce the stray capacitance between adjacent cables wound around the annular magnetic core. A radiation measuring system comprising: a cable arranging member arranged to be arranged. 2. A radiation measuring system for measuring a dose of the radiation by a radiation detector for detecting the radiation sending the detection signal to a preamplifier via a cable, wherein the preamplifier and the radiation detection are provided. Placed between the vessels,
A first annular magnetic core around which the cable is wound a plurality of times so as to eliminate noise mixed in the cable; and a magnetic material having a frequency characteristic different from that of the first annular magnetic core. A second annular magnetic core, which is arranged in series with the first annular magnetic core between the radiation detectors, and in which the cable is wound a plurality of times; and a second annular magnetic core wound around the first and second annular magnetic cores, respectively. To reduce the stray capacitance that occurs between adjacent cables,
A radiation measuring system comprising: a plurality of cable arranging members for arranging the cables so as to be spaced apart from each other.