JP2013238439A - Radiation monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a radiation monitor capable of accurately measuring radiation while removing noises caused by vibrations.SOLUTION: A radiation monitor comprises a first semiconductor sensor 11, a second semiconductor sensor 12, an electromagnetic shield case 16 in which the first semiconductor case 11 and the second semiconductor case 12 are accommodated in such a manner that electrode surfaces 11s, 12s of electrodes 11, 12 of the same polarity are turned in the same direction, and which is grounded, and an asynchronous counter circuit 4 which counts signals which are outputted asynchronously. A gap 11 between the electrode surface 11s of the first semiconductor sensor 11 and the electromagnetic shield case 16 and a gap G12 between the electrode surface 12s of the second semiconductor sensor 12 and the electromagnetic shield case 16 are made equal, and even under a vibrating state, the gaps G11, G12 are changed similarly.

Description

  The present invention relates to a radiation monitor that detects radiation using a semiconductor sensor.

  There are various types of radiation monitors. Among them, radiation monitors using semiconductor sensors have high sensitivity and are small, and are used in many facilities such as nuclear power plants and spent fuel reprocessing facilities. On the other hand, because semiconductor sensors are highly sensitive to vibration, noise measurement accuracy is reduced due to noise when it is installed in a mixed drive device with vibration or when there is a vibration source such as a large rotating device nearby. There is a concern to do.

  Therefore, a vibrometer is mounted on the radiation detector, and a radiation monitor that stops the output of the radiation detector when a constant intensity of vibration is applied (see, for example, Patent Document 1), a plurality of semiconductor sensors, When the output from the sensor is detected at the same time, a radiation position detection device or radiation monitor (see, for example, Patent Documents 2 and 3) that performs signal processing by treating it as noise, or in order to suppress fluctuations in ground-floating capacitance, There has been proposed a radiation detector (see, for example, Patent Document 4) that fixes a conductive layer and a shield case, which are opposed to an electrode through an insulator, to the same potential.

Japanese Patent Laid-Open No. 7-333349 (paragraphs 0007 to 0010, FIGS. 1 to 7) JP-A-4-303787 (paragraphs 0006 to 0012, FIGS. 1 to 4) JP 2003-57354 A (paragraphs 0011 to 0014, FIGS. 1 and 2) JP 2008-209294 A (paragraphs 0015 to 0017, FIG. 1)

  However, when measures are taken with a vibrometer, there is a problem that the configuration becomes complicated and the timing adjustment of the output of the radiation detector and the output of the vibration detector is complicated, and adjustment takes time. In addition, when judging noise by comparing outputs from multiple sensors, it is effective against power supply noise and electromagnetic noise propagating in space, but the difference in stray capacitance in each sensor cannot be ignored. In addition, since the change in stray capacitance due to the vibration direction is not uniform, it is a problem to surely eliminate noise at the wave height level near the wave height discrimination level. Moreover, it is difficult to completely suppress the fluctuation of stray capacitance due to vibration, and there is a concern that the influence of vibration remains.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a radiation monitor capable of removing noise caused by vibration and capable of performing accurate radiation measurement.

  The radiation monitor of the present invention has a plate-like shape, a first semiconductor sensor that outputs a signal corresponding to incident radiation, a second semiconductor sensor of the same type as the first semiconductor sensor, and the first semiconductor An electromagnetic shield case in which the sensor and the second semiconductor sensor are disposed and housed so that the electrode surfaces of the electrodes of the same polarity are in the same direction and grounded, and an output signal of the first semiconductor sensor And a non-simultaneous counting unit that counts signals output non-simultaneously among the output signals of the second semiconductor sensor, and the electromagnetic shield that faces the electrode surface of the first semiconductor sensor and the electrode surface The distance between the surface of the case and the distance between the electrode surface of the second semiconductor sensor and the surface of the electromagnetic shielding case facing the electrode surface are equal and in a vibrating state. Also as each interval is changed in the same manner, wherein the first semiconductor sensor and the second semiconductor sensor is located.

  According to the radiation monitor of the present invention, the stray capacitances of the two semiconductor sensors are equal in both a stationary state and a vibration state, so that it is possible to obtain a radiation monitor capable of accurate radiation measurement by eliminating noise caused by vibration. .

The external view when the lid | cover of the electromagnetic shielding case closed at the time of use for explaining the structure of the radiation detector which is the main components of the radiation monitor concerning Embodiment 1 of this invention is opened, and a cross section at the time of use FIG. It is a block diagram which shows the structure of the radiation monitor concerning Embodiment 1 of this invention. It is a wave form diagram of the signal output from two semiconductor sensors for explaining operation of the radiation monitor concerning Embodiment 1 of the present invention, and signal output after signal processing. It is a block diagram which shows the structure of the radiation monitor concerning Embodiment 2 of this invention. It is a wave form diagram of the signal output from two semiconductor sensors for explaining operation of the radiation monitor concerning Embodiment 2 of the present invention, and the signal output which carried out signal processing.

Embodiment 1 FIG.
1 to 3 are diagrams for explaining a radiation monitor according to a first embodiment of the present invention. FIGS. 1A and 1B are mechanical views of a radiation detector which is a main component of the radiation monitor. FIG. 1A is a perspective view of an external appearance when a lid of an electromagnetic shield case that is closed during use is opened, and FIG. 1B is a view of B in FIG. It is a cut part by the -B line, and is a sectional view at the time of use (when a lid is closed). FIG. 2 is a block diagram showing the configuration of the radiation monitor. FIG. 3 is a waveform diagram in which signal outputs from two semiconductor sensors and signal outputs counted as radiation from these signal outputs are displayed in synchronization with each other for explaining the operation of the radiation monitor. The detection system pulse signal output, the B detection system pulse signal output, and the signal output counted as radiation.

  The radiation monitor according to the first embodiment is characterized in that the stray capacitances of the two semiconductor sensors for performing non-coincidence counting are the same both when stationary and when they vibrate, that is, the electromagnetic shield of the semiconductor sensor fluctuates similarly. The arrangement in the case is devised. First, the configuration of the entire radiation monitor will be described.

As shown in FIG. 2, the radiation monitor 10 includes, as main components, a first semiconductor sensor 11 and a second semiconductor sensor 12 that detect radiation and output an analog current pulse, and a first semiconductor sensor 11. converting the output analog current pulses amplified into an analog voltage pulses, an analog current pulse outputted from the first preamplifier 13 and the second semiconductor sensor 12 for outputting an analog voltage pulse signal S _a to the analog voltage pulses and it amplifies a second preamplifier 14 which outputs an analog voltage pulse signal S _B, has a radiation detector 1 arranged in the electromagnetic shield case 16 which is grounded.

The comparison of the pulse signal output from the radiation detector 1, the analog voltage pulse signal S _A outputted from the first preamplifier 13, analog voltage pulse signals S _A and set value (wave height discrimination level) and, when the analog voltage pulse signal S _a is greater than or equal height discrimination level, the first pulse height discriminator 2 for outputting a digital pulse, the analog voltage pulse signal S _B outputted from the second preamplifier 14, analog voltage pulse signal S _B and the set value (pulse height discrimination level) and comparing, when the analog voltage pulse signal S _a is greater than or equal height discrimination level, and a second wave height discriminator 3 for outputting a digital pulse, the first Of the digital pulses output from the wave height discriminator 2 and the second wave height discriminator 3, the digital pulses output non-simultaneously are counted, and the digital data output simultaneously The non-coincidence circuit 4 for outputting a counted value by ignoring the pulse, and a.

  Further, the memory 6 for storing the arithmetic program and data, the display 7, the non-simultaneous counting circuit 4, the memory 6 and the display 7 are controlled, and the count value of the non-simultaneous counting circuit 4 is read at a constant cycle to read the memory 6 The calculation unit 5 calculates the count rate based on the calculation program and data stored in the memory 6, calculates the engineering value based on the count rate, stores the calculation result in the memory 6, and displays it on the display unit 7. And.

  Then, the wave height discrimination levels of the first wave height discriminator 2 and the second wave height discriminator 3 are set to the same voltage (threshold Th), and further adjusted so that the operating points are equivalent. In the non-simultaneous counting circuit 4, the timing of the coincidence counting is adjusted in advance so that erroneous counting and counting omission are not caused in the logic operation.

Next, the configuration of the radiation detector 1 will be described.
In the radiation detector 1, as shown in FIG. 1, the first semiconductor sensor 11, the second semiconductor sensor 12, the first preamplifier 13, and the second preamplifier 14 are mounted on the board surface 15 s of the printed board 15. Has been. At this time, the first semiconductor sensor 11 and the second semiconductor sensor 12 are arranged on the substrate surface 15s so that the electrodes having the same polarity are in the same direction. A bias power supply pattern (not shown) for operating them is laminated and constitutes a sensor circuit. The sensor circuit is housed in an electromagnetic shield case 16 composed of a bottom plate 161 and a lid 162. The electromagnetic shield case 16 has a flat box shape, and at least the inner surface is covered with metal, thereby electrically shielding the internal sensor circuit against electromagnetic noise and being grounded.

  The first semiconductor sensor 11, the first preamplifier 13, and the first wave height discriminator 2 are used as the A detection system, and the second semiconductor sensor 12, the second preamplifier 14, and the second wave height discriminator 3 are used. Is a B detection system. Of the A detection system and the B detection system, members housed in the electromagnetic shield case 16 as the radiation detector 1 are arranged symmetrically on the printed circuit board 15. More specifically, the first semiconductor sensor 11 is configured in a plate shape by a semiconductor element 112 and electrode plates 111 and 113 sandwiching the semiconductor element 112 from both sides, and the second semiconductor sensor 12 is similarly formed with the semiconductor element 122. A plate-like structure is formed by electrode plates 121 and 123 sandwiching the semiconductor element 122 from both sides. In the semiconductor sensors 11 and 12, the electrode surfaces 11s and 12s are arranged in one plane parallel to the substrate surface 15s of the substrate 15 (and the main surface 16s of the electromagnetic shield case 16), and are perpendicular to the plane. The semiconductor sensors 11 and 12 are arranged so as to be symmetric with respect to a plane (symmetric plane Ps) that is equidistant from the semiconductor sensors 11 and 12. Further, the bias power source (not shown) is also formed symmetrically so as to spread on both sides around the symmetry plane Ps. The printed circuit board 15 and the electromagnetic shield case 16 are also formed so as to be symmetric with respect to the symmetry plane Ps.

  With this configuration, the electrode plates 113 and 123 side of both semiconductor sensors 11 and 12 are fixed to the bottom plate 161 of the electromagnetic shield case 16 via the printed circuit board 15, respectively. The distance from the bottom plate 161 is fixed by the thickness of the printed circuit board 15. On the other hand, there are gaps G11 and G12 between the semiconductor plates 11 and 12 on the side of the electrode plates 111 and 121 and the surface 16f of the electromagnetic shield case 16 facing each other (the inner surface of the lid 162). However, the profile (distribution) of the gaps G11 and G12 is symmetric with respect to the symmetry plane Ps, and the electrode surfaces 11s and 12s of the electrodes 11 and 12 having the same polarity face the same direction. Even if the vibration in the direction is transmitted, the profiles of the gaps G11 and G12 are deformed while maintaining symmetry. In other words, both when stationary and when vibrating. Equivalence between the distance G11 between the first semiconductor sensor 11 and the electromagnetic shield case 16 and the distance G12 between the second semiconductor sensor 12 and the electromagnetic shield case 16 can be maintained.

  As a result, the stray capacitances of the A detection system having the first semiconductor sensor 11 and the B detection system having the second semiconductor sensor are equal in both the stationary state and the vibration state. Further, not only the semiconductor sensors 11 and 12 but also the preamplifiers 13 and 14 and the bias power supply pattern are arranged symmetrically with respect to the symmetry plane Ps, and the members of the A detection system and the B detection system in the radiation detector 1 are arranged. The members are arranged so as to be symmetric with respect to the symmetry plane Ps. For this reason, the stray capacitance including the wiring members of the circuit is equal in both the stationary state and the vibration state.

Next, the operation will be described.
When the radiation monitor 10 is operated and, for example, radiation is incident on the first semiconductor sensor 11 of the A detection system, the first semiconductor sensor 11 outputs an analog current pulse signal having an intensity corresponding to the amount of incident radiation, the first preamplifier 13, the output analog current pulse signal is amplified into an analog voltage pulse signals and outputs a signal S _a. The first wave height discriminator 2 compares the output signal S _A and the wave height discrimination level (threshold value Th), and outputs a digital pulse when S _A ≧ Th. Similarly, when the radiation is incident on the second semiconductor sensor 12 of the B detector system, the B amplifier preamplifier 14 and the wave height discriminator 3 operate.

Here, it is assumed that the output signal S _A from the first preamplifier 13 of the A detection system is analog signal pulses P _a1 , P _a3 , P _a5 , P _a6 , and P _a7 as shown in the upper part of FIG. In this case, the first wave height discriminator 2 removes the analog signal pulses P _a3 and P _a6 that are lower than the threshold value Th, and performs non-simultaneous counting of only the digital pulses corresponding to the analog signal pulses P _a1 , P _a5 , and P _a7. Output to circuit 4.

Then, the output signal _{S B} from the second preamplifier 14 B detection system as shown in the middle 3, and was analog signal pulses _{P b2, P b4, P b5} , P b6, P b8. In this case, the second wave height discriminator 3 removes the analog signal pulses P _b2 and P _b6 lower than the threshold value Th, and performs non-simultaneous counting of only the digital pulses corresponding to the analog signal pulses P _b4 , P _b5 , and P _a8. Output to circuit 4.

Of the digital pulses corresponding to the analog signal pulses P _a1 , P _a5 , P _a7 , P _b4 , P _b5 , P _a8 , the non coincidence counting circuit 4 outputs the digital pulses corresponding to P _a5 and P _{b5 at} the same timing. It is determined that the signal has been processed, and is removed. Then, as shown in the lower part of FIG. 3, the count signals C _e1 , C _e4 , C _e7 and C _e8 corresponding to P _a1 , P _b4 , P _a7 and P _a8 are output.

  The computing unit 5 reads the count value (count signal) of the non-simultaneous counting circuit 4 at a fixed period, stores it in the memory 6, obtains the count rate based on the computation program and data stored in the memory 6, and sets the count rate. The engineering value is calculated based on the result, and the calculation result is stored in the memory 6 and displayed on the display unit 7.

That is, the pulse height discriminators 2 and 3 count only the pulses whose peak values are equal to or higher than the discrimination level (Th) among the analog signal pulses output from the radiation detector 1. Thereby, minute pulses P _a3 and P _b2 such as noise peculiar to the semiconductor sensor element and minute pulses P _a6 and P _b6 such as external noise or power supply noise can be removed. Of the digital pulses output to the non-simultaneous counting circuit 4, only non-simultaneous pulses are counted. As a result, the simultaneously output signals can be regarded as occurring due to the change in the capacitance of the sensor due to vibration, and P _a5 and P _b5 can be removed. Even if there is no wave height discriminator and digital pulses corresponding to the analog signal pulses P _a6 and P _b6 are output to the non-simultaneous counting circuit 4, they are regarded as vibration noise and can be removed.

  As described above, in the radiation monitor 10 according to the first embodiment, instead of suppressing the fluctuation of the stray capacitance due to vibration, the stray capacitances of the two sensors 11 and 12 change in the same manner, thereby the A detection system. And the B detection system were made to have the same stray capacitance. As a result, the mechanical rigidity does not need to be increased unnecessarily, so radiation that can eliminate the effects of vibration noise using the electromagnetic shield case 16 and sensor circuit manufactured using general materials (materials and thickness). The monitor 10 can be obtained. As a specific method for equalizing the stray capacitances of the A detection system and the B detection system, in the radiation monitor 10 according to the first embodiment, the semiconductor sensors 11 and 12 of the A detection system and the B detection system The electrode surfaces 11s and 12s are provided in the same plane, and are arranged so as to be symmetric with respect to the symmetry plane Ps. However, for example, if a configuration in which the distances G11 and G12 with the electromagnetic shield case 16 change in the same manner during vibration is known by simulation or the like, the arrangement is not limited to symmetry, and other arrangement configurations may be used. As long as the above conditions are satisfied, the number of semiconductor sensors of the A detection system and the B detector may be the same as a plurality.

  As described above, according to the radiation monitor 10 according to the first exemplary embodiment of the present invention, the first semiconductor sensor 11 that has a plate shape and outputs a signal corresponding to the incident radiation, and the first semiconductor sensor 11. The second semiconductor sensor 12 of the same type, the first semiconductor sensor 11 and the second semiconductor sensor 12 are arranged and accommodated so that the electrode surfaces 11s and 12s are parallel to each other and are grounded. The output signal from the shield case 16 and the first semiconductor sensor 11 (strictly via the preamplifier 13 and the wave height discriminator 2) and the output signal from the second semiconductor sensor 12 (strictly, the preamplifier 14 and the wave height discriminator 3). And a non-simultaneous counting circuit 4 that functions as a non-simultaneous counting unit that counts signals output non-simultaneously among the output signals of the first semiconductor sensor 11. The gap G11 between the electrode surface 11s and the surface 16f of the electromagnetic shield case 16 facing the electrode surface 11s, and the electrode surface 12s of the second semiconductor sensor 12 and the surface 16f of the electromagnetic shield case 16 facing the electrode surface 12s The first semiconductor sensor 11 and the second semiconductor sensor 12 are arranged so that the gaps G12 are equal and the gaps G11 and G12 change in the same manner even in a vibration state.

  For this reason, the stray capacitances of the A detection system having the first semiconductor sensor 11 and the B detection system having the second semiconductor sensor are equal in both the stationary state and the vibration state. Thereby, when vibration is transmitted to the radiation detector 1, signals resulting from the vibration are output from both semiconductor sensors 11 and 12 at the same timing at the same timing. Therefore, by removing the signals output at the same timing from the signals from both the semiconductor sensors 11 and 12 by the non-coincidence circuit 4, it is possible to reliably remove the signal caused by the vibration. That is, it is possible to obtain a radiation monitor capable of removing noise due to vibration and performing accurate radiation measurement.

  In particular, the electromagnetic shield case 16 is formed in a flat shape, is symmetrical with a plane perpendicular to the main surface 16s as a symmetry plane Ps, and the first semiconductor sensor 11 and the second semiconductor sensor 12 are Since it arrange | positions so that it may become mutually symmetrical with respect to the symmetry plane Ps, even if the space | intervals G11 and G12 are fluctuate | varied by vibration, since it will fluctuate similarly, an equivalence can be maintained reliably. Therefore, the stray capacitances of the first semiconductor sensor 11 and the second semiconductor sensor 12 can be made equal in both the stationary state and the vibration state. That is, the influence on the count rate due to vibration noise can be reliably prevented with a simple configuration.

Furthermore, not only the semiconductor sensors 11 and 12 but also the preamplifiers 13 and 14 and a bias power supply pattern (not shown) are arranged symmetrically with respect to the symmetry plane Ps on one substrate 15,
The A detection system member and the B detection system member in the radiation detector 1 (electromagnetic shield case 16) are arranged so as to be symmetrical with respect to the symmetry plane Ps. For this reason, the stray capacitance including the wiring members of the circuit is equal in both the stationary state and the vibration state. In addition, the same effect can be obtained with respect to power supply noise, airborne noise, and ground wire intrusion noise, and a highly reliable radiation monitor with enhanced noise resistance can be provided.

  In particular, between the first semiconductor sensor 11 and the non-simultaneous counting circuit 4, and between the second semiconductor sensor 12 and the non-simultaneous counting circuit 4, respectively, among the inputted signals, the set value Th or more. Is provided with wave height discriminators 2 and 3 that function as output discriminators that discriminate and output only the signals of the above, so that minute pulses such as noise peculiar to semiconductor sensor elements, external noise or power supply noise are removed, and more Accurate radiation monitoring is possible.

Embodiment 2. FIG.
The radiation monitor according to the second embodiment is different from the first embodiment in that a third wave height discriminator and a fourth wave height discriminator are provided in the signal processing circuit portion between the radiation detector and the non-coincidence circuit. , OR logic circuit, and AND logic circuit are added and changed. The radiation detector part and the circuit part downstream from the non coincidence counting circuit are the same as those in the first embodiment. 4 and 5 are diagrams for explaining the radiation monitor according to the second embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of the radiation monitor. FIG. 5 is a diagram for explaining the operation of the radiation monitor. It is a waveform diagram from the top, pulse signal output S _{A of the A} detection system, pulse signal output S _B of the B detection system, digital pulse output signal S _{H of} the first wave height discriminator, digital of the third wave height discriminator Pulse output signal S _J , second pulse height discriminator digital pulse output signal S _K , fourth pulse height discriminator digital pulse output signal S _L , OR logic circuit count signal output S _N , AND logic circuit count signal The output S _{P is} a signal output S _E counted as radiation. In the figure, parts that are the same as those in the first embodiment are given the same reference numerals, and hereinafter, parts that are different from those in the first embodiment will be mainly described.

As a signal processing circuit section between the radiation detector 1 and the non-coincidence circuit 4, the for A detection system, the analog voltage pulse signal S _A which is input from the first preamplifier 13, analog voltage pulse signal S comparing the _a and pulse height discrimination level (threshold value), when the analog voltage pulse signal S _a is less than the threshold value, in addition to the first pulse height discriminator 2 for outputting a digital pulse, the analog voltage pulse signal S _a and the wave height discriminator _A third pulse height discriminator 8 is further provided that compares the level (threshold value) and outputs a digital pulse when the analog voltage pulse signal SA is equal to or greater than the threshold value.

Also for detecting B, similarly to the A detection, compared to the analog voltage pulse signal S _B input from the second preamplifier 14 and an analog voltage pulse signal S _B and the pulse height discrimination level (threshold value), analog In addition to the second pulse height discriminator 3 that outputs a digital pulse when the voltage pulse signal S _B is greater than or equal to the threshold value, the analog voltage pulse signal S _B is compared with the pulse height discrimination level (threshold value). _A fourth wave height discriminator 9 that outputs a digital pulse when _B is equal to or greater than a threshold is further provided.

  The wave height discrimination levels of the first wave height discriminator 2 and the second wave height discriminator 3 are set to the same voltage (threshold Th1 = Th) as in the first embodiment. The wave height discrimination levels (threshold value Th2) of the third wave height discriminator 8 and the fourth wave height discriminator 9 are set to the same voltage lower than the threshold value Th1. And these are adjusted so that an operating point may become equivalent.

  The threshold Th1 (hereinafter referred to as the first discrimination level) is the lower limit of the measurement energy range to be detected as radiation, and the threshold Th2 (hereinafter referred to as the second discrimination level) is the first discrimination level. It is set to a value lower than Th1 and higher than the noise level specific to the semiconductor sensor element.

  The digital pulses from the first wave height discriminator 2 and the second wave height discriminator 3 are output to the OR logic circuit 41. The OR logic circuit 41 outputs the first wave height discriminator 2 and the second wave height discriminator. When any output signal of the digital pulse output from the device 3 is present, the digital pulse corresponding to the output signal is output. On the other hand, the digital pulses from the third wave height discriminator 8 and the fourth wave height discriminator 9 are output to the AND logic circuit 42, and the AND logic circuit 42 outputs the third wave height discriminator 8 and the fourth wave height discriminator. When digital pulses from both of the devices 9 are output, a digital pulse corresponding to the output signal is output.

  When the digital pulse is output from the OR logic circuit 41 and the AND logic circuit 42, the non-simultaneous counting circuit 4 counts the signals output non-simultaneously and outputs a count value at a fixed period, and the digital pulses are output simultaneously. Ignore the signal. That is, the OR logic circuit 41 and the AND logic circuit 42 function as a non-simultaneous counting unit in conjunction with the non-simultaneous counting circuit 4, as will be described later. The computing unit 5 reads the count value (count signal) of the non-simultaneous counting circuit 4 at a fixed period, stores it in the memory 6, obtains the count rate based on the computation program and data stored in the memory 6, and sets the count rate. The engineering value is calculated based on the result, and the calculation result is stored in the memory 6 and displayed on the display unit 7.

Next, a specific operation will be described.
The radiation monitor 10 is operated. For example, as shown in the first stage of FIG. 5, the output signal S _A from the first preamplifier 13 of the A detection system is analog signal pulses P _a1 , P _a2 , P _a3 , P _a4. Suppose that. In this case, the first wave height discriminator 2 removes the analog signal pulse P _a4 lower than the first discrimination level Th1, and, as shown in the third stage of FIG. 5, the analog signal pulses P _a1 , P _a2 , the digital pulse _{D H1, D H2,} the signal _{S H} including only _{D H3} corresponding to P _a3, and outputs the OR logic circuit 41.

On the other hand, the analog signal pulses P _a1 , P _a2 , P _a3 , and P _a4 output to the third wave height discriminator 8 do not have analog signal pulses to be removed lower than the second discrimination level Th2. Therefore, as shown in the fourth stage of FIG. 5, the third wave height discriminator 8 has digital pulses D _J1 , D _J2 , D D corresponding to all analog signal pulses P _a1 , P _a2 , P _a3 , P _a4. A signal S _J including _{J 3} and D _{J 4} is output to the AND logic circuit 42.

Then, the output signal _{S B} from the second preamplifier 14 B detection system as shown in the second stage of FIG. 5, and was analog signal pulses _{P b2, P b3, P b4} , P b5. In this case, the second wave height discriminator 3 removes the analog signal pulse P _b2 lower than the first discrimination level Th1, and as shown in the fifth stage of FIG. 5, the analog signal pulses P _b3 , P _b4 , and it outputs a signal _{S K} including digital pulse _{D K3, D K4, D K5} corresponding to P _b5 to the OR logic circuit 41.

On the other hand, the analog signal pulses P _b2 , P _b3 , P _b4 , and P _b5 output to the fourth wave height discriminator 9 have no analog signal pulse to be removed lower than the second discrimination level Th2. Therefore, as shown in the sixth stage of FIG. 5, the fourth wave height discriminator 9 includes digital pulses D _L2 , D _L3 , D _b corresponding to all analog signal pulses P _b2 , P _b3 , P _b4 , P _{b5. The} signal S _L including _{L 4} and D _{L 5} is output to the AND logic circuit 42.

As shown in the seventh stage of FIG. 5, the OR logic circuit 41 generates digital pulse signals L _N1 and L _N2 based on the output from either the first wave height discriminator 2 or the second wave height discriminator 3. , and it outputs a signal _{S N} containing _{L N3, L N4, L N5} to the non-coincidence circuit 4. As shown in the eighth stage of FIG. 5, the AND logic circuit 42 generates digital pulses L _P2 and L _P3 corresponding to the digital pulses output from both the third wave height discriminator 8 and the fourth wave height discriminator 9. , and it outputs a signal _{S P} containing only _{L P4} in the non-coincidence circuit 4.

Since the non-simultaneous counting circuit 4 outputs L _N2 and L _P2 , L _N3 and L _P3 , and L _N4 and L _P4 among the digital pulses input to the OR logic circuit 41 and the AND logic circuit 42, Remove. Then, as shown at the bottom of FIG. 5, the count signals C _e1 and C _e5 corresponding to L _N1 and L _N5 are output.

As a result, the non-simultaneous counting circuit 4 counts only the signals corresponding to P _a1 and P _b5 among the analog pulse signals output from both the A and B detection systems, and the other signals are vibration and noise. Is removed as a signal generated by.

  Note that FIG. 5 does not describe the case where a level analog pulse signal lower than the second discrimination level Th2 is generated, but simultaneously includes signals of such level from both the A detection system and the B detection system. Table 1 shows the level of the output signal and the signal processing result in the radiation monitor 10. In the table, “simultaneous removal” means that the signals are simultaneously input by vibration and are removed, and “cut” means that the signals are less than the level to be detected as radiation.

  As shown in Table 1, among the signals simultaneously output from the A detection system semiconductor sensor 11 and the B detection system semiconductor sensor 12, at least a signal of the first discrimination level Th1 or higher is incident on the semiconductor sensor. Alternatively, it is determined that the signal is output from the semiconductor sensor due to vibration transmitted. Then, only when both signals are equal to or higher than the second discrimination level Th2 among those signals, it is determined that they are generated simultaneously by vibration and are removed from the count. That is, only when one of the signals from both detection systems is equal to or higher than the first discrimination level Th1 and the other is lower than the second discrimination level, the radiation is counted as incident.

  As a result, for example, a signal of the first discrimination level Th1 or more is generated from one detection system due to variations in the semiconductor elements constituting the semiconductor sensors 11 and 12 and ideally a deviation in threshold value that should be the same. However, when the signal from the other detection system is less than the first discrimination level Th1, in the first embodiment, vibration noise may be counted as radiation as if it were not generated simultaneously. However, in the present embodiment, Th1> Th2, and a second discrimination level Th2, which is a voltage level that may be generated by vibration, is provided, and a signal equal to or higher than Th2 is picked up as a determination target of whether or not it occurs non-simultaneously. As a result, vibration noise can be reliably detected simultaneously, and vibration noise can be reliably eliminated. Note that as long as the logic operates as described above, it is not necessarily limited to the combination of the circuit configurations illustrated in FIG. 4, and other configurations may be used.

  As described above, according to the radiation monitor 10 according to the second exemplary embodiment, between the first semiconductor sensor 11 and the non-simultaneous counting circuit 4, the OR logic circuit 41, and the AND logic circuit 42 functioning as an asynchronous counting unit. , And the second semiconductor sensor 12 and the non-simultaneous counting circuit 4, which functions as an asynchronous counting unit, the OR logic circuit 41, and the AND logic circuit 42, respectively, among the output signals, the first set value A first wave height discriminator 2 and a second wave height discriminator 3 which are output discriminating units for discriminating and outputting only signals having a first discrimination level Th1 or higher, and a second smaller than the first set value. A third wave height discriminator 8 and a fourth wave height discriminator 9 are provided as output discriminating units for discriminating and outputting only signals having a set value of the second discrimination level Th2 or higher. 1 semiconductor sensor Among the signals output simultaneously from the first and second semiconductor sensors 12, a signal in which one is not less than the first set value and the other is less than the second set value is counted as a signal output non-simultaneously. Since it is configured, it is possible to remove fine signals (less than Th1) that should not be counted as radiation, and to detect signals that should be judged whether or not they are vibration noise (Th2 or more) without losing vibration noise. it can.

10: Radiation monitor,
1: radiation detector,
11: A detection system semiconductor sensor (first semiconductor sensor),
11s: electrode surface,
12: B sensor semiconductor sensor (second semiconductor sensor),
12s: electrode surface,
13: A detection system preamplifier circuit (first preamplifier circuit),
14: B detection system preamplifier circuit (second preamplifier circuit),
15: Printed circuit board (board)
16: Electromagnetic shield case,
16f: the surface where the electrodes of the semiconductor sensor face each other, 16s: the main surface,
2: A detection system wave height discriminator (first wave height discriminator),
3: B height discriminator of the B detection system (second wave height discriminator),
4: Non-simultaneous counting circuit (non-simultaneous counting unit),
5: arithmetic unit,
6: Memory,
7: Display,
8: A detection system wave height discriminator (third wave height discriminator),
9: B detection system wave height discriminator (fourth wave height discriminator),
41: OR logic circuit (non-simultaneous counting unit),
42: AND logic circuit (non-simultaneous counting unit).

Claims (5)

A first semiconductor sensor that has a plate shape and outputs a signal corresponding to incident radiation;
A second semiconductor sensor of the same type as the first semiconductor sensor;
An electromagnetic shielding case in which the first semiconductor sensor and the second semiconductor sensor are arranged and housed so that the electrode surfaces of the electrodes of the same polarity are in the same direction and are grounded;
A non-simultaneous counting unit that counts signals output non-simultaneously among the output signals from the first semiconductor sensor and the output signals from the second semiconductor sensor;
The distance between the electrode surface of the first semiconductor sensor and the surface of the electromagnetic shield case facing the electrode surface, and the surface of the electromagnetic shield case facing the electrode surface of the second semiconductor sensor and the electrode surface The radiation monitor is characterized in that the first semiconductor sensor and the second semiconductor sensor are arranged so that the distance between the first semiconductor sensor and the second semiconductor sensor changes in the same manner even in a vibration state.   The electromagnetic shield case is formed in a flat shape, has a symmetrical shape with a plane perpendicular to the main surface as a symmetry plane, and the first semiconductor sensor and the second semiconductor sensor have the symmetry plane. The radiation monitor according to claim 1, wherein the radiation monitor is arranged symmetrically with respect to each other.   Of the circuit members that process signals output from the first semiconductor sensor, the circuit members that are housed in the electromagnetic shield case, and of the circuit members that process signals output from the second semiconductor sensor. The radiation monitor according to claim 2, wherein the circuit member housed in the electromagnetic shielding case is disposed so as to be symmetrical with respect to the symmetry plane.   Between the first semiconductor sensor and the asynchronous counter, and between the second semiconductor sensor and the asynchronous counter, only signals that are equal to or higher than a set value are output. The radiation monitor according to any one of claims 1 to 3, further comprising an output discriminating section for outputting separately. Between the first semiconductor sensor and the asynchronous counter, and between the second semiconductor sensor and the asynchronous counter, a signal that is equal to or higher than a first set value among the output signals. An output discriminating unit for discriminating and outputting only an output discriminating unit, and an output discriminating unit for discriminating and outputting only a signal of a second set value or less smaller than the first set value,
The non-simultaneous counting unit is configured such that one of the signals simultaneously output from the first semiconductor sensor and the second semiconductor sensor is not less than the first set value and the other is less than the second set value. 4. The radiation monitor according to claim 1, wherein the signal is counted as the non-simultaneously output signal. 5.

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