JP4454840B2 - Radiation instrumentation system, health diagnosis method thereof, and radiation measurement method - Google Patents

Radiation instrumentation system, health diagnosis method thereof, and radiation measurement method Download PDF

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JP4454840B2
JP4454840B2 JP2000391902A JP2000391902A JP4454840B2 JP 4454840 B2 JP4454840 B2 JP 4454840B2 JP 2000391902 A JP2000391902 A JP 2000391902A JP 2000391902 A JP2000391902 A JP 2000391902A JP 4454840 B2 JP4454840 B2 JP 4454840B2
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photomultiplier tube
radiation
multiplication factor
instrumentation system
temperature history
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JP2002196080A (en
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直敬 小田
滋 小田中
好夫 北
豊 福武
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Toshiba Corp
Toshiba Plant Systems and Services Corp
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Toshiba Corp
Toshiba Plant Systems and Services Corp
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Description

【０００１】
【発明の属する技術分野】
本発明は、シンチレーション型放射線検出器と光電子増倍管（PMT）を用いた放射線計装システムに関し、特に高温下で使用するのに適した放射線計装システムと、そのシステムの健全性診断方法、ならびに放射線計測方法に関する。
【０００２】
【従来の技術】
従来のシンチレーション型放射線検出器と光電子増倍管を用いた放射線計装システムの例を図８に示す。すなわち、放射線をシンチレーション型放射線検出器１で検出し、この検出器１の光出力信号を光電子増倍管２で増倍し、この光電子増倍管２の出力をキャパシタ３を通して、増幅器４で増幅する。増幅器４の出力を、波高弁別回路７、カウンタ回路８、CPU（中央処理装置）９の順に送って処理する。図中の符号５は、光電子増倍管２に印加電圧ＨＶを加えるための電源である。
【０００３】
【発明が解決しようとする課題】
図９は、一般な光電子増倍管の温度特性である。この図からわかるように、光電子増倍管の増倍率は、時間とともに徐々に低下する。また、点線９１で示す高温の場合の方が、実線９２で示す低温の場合よりも増倍率の低下が速い。
【０００４】
図１０は、一般なシンチレーション型検出器の信号を増倍した光電子増倍管の出力波高の分布を示す。図中の光電ピークの波高値は、放射線のエネルギに比例した値となる。一般に、光電子増倍管の増倍率に変化がなければ、特定のエネルギの放射線の波高値は常に同一となる。また、波高が低い領域には、増幅器等の回路系のホワイトノイズがある。一般的に、ホワイトノイズと光電ピークを弁別して光電ピークを求めるために、弁別レベルを設定し、その弁別レベル以上の範囲の信号のみを測定するようにしている。
【０００５】
従来の方式では、光電子増倍管の増倍率が波高弁別レベルよりも低下した場合に、はじめて測定に影響があることがわかるものであった。このため、特に増倍率の低下が著しい高温下での使用の場合等に、その放射線計装システムの信頼性向上が望まれていた。
【０００６】
本発明は、前記課題を解決するものであって、高温化でも信頼性の高い放射線計装システムおよびその健全性診断方法ならびに放射線計測方法を提供することを目的としている。
【００１１】
【課題を解決するための手段】
本発明は上記目的を達成するものであって、請求項１の発明は、シンチレーション型放射線検出器と、この放射線検出器からの光信号を増倍する光電子増倍管と、この光電子増倍管の出力を増幅する増幅器と、を有する放射線計装システムにおいて、前記光電子増倍管の付近の温度を測定してその温度の履歴を記憶する手段と、予め設定した前記光電子増倍管の温度履歴とその光電子増倍管の増倍率との関係に基いて、前記記憶された温度履歴により前記光電子増倍管の増倍率の経時的な低下を補償する補償手段と、を有することを特徴とする放射線計装システムである。
この請求項１の発明によれば、線源の有無にかかわりなく、光電子増倍管の増倍率の低下が著しい高温下でも信頼性の高い放射線計装システムを提供できる。
【００１６】
次に請求項１０の発明は、前記補償工程は、前記線源波高分布測定工程で得られた波高分布に基いて、当該波高分布が所定のレベルになるように前記光電子増倍管の印加電圧を調整する工程を含むこと、を特徴とする請求項７、８または９に記載の放射線測定方法である。
この請求項１０の発明によれば、請求項７、８または９の発明による作用効果が得られるとともに、光電子増倍管の印加電圧の調整によって、信頼性の高い放射線計測を行うことができる。
【００２０】
次に請求項５の発明は、シンチレーション型放射線検出器と、この放射線検出器からの光信号を増倍する光電子増倍管と、この光電子増倍管の出力を増幅する増幅器と、を有する放射線計装システムの健全性を診断する方法において、予め設定した前記光電子増倍管の温度履歴とその光電子増倍管の増倍率の関係と、実測した前記光電子増倍管の温度履歴とからその光電子増倍管の増倍率を計算する工程と、前記計算された光電子増倍管の増倍率と実測されたその光電子増倍管の増倍率とを比較する工程と、を有することを特徴とする放射線計装システムの健全性診断方法である。
この請求項５の発明によれば、高温下での光電子増倍管の増倍率の低下を考慮して放射線計装システムの健全性を診断することができる。
【００２１】
【発明の実施の形態】
以下に、図面を参照しながら本発明の実施の形態を説明する。ただし、従来技術と共通の部分には共通の符号を付して、適宜説明を省略する。
図１は本発明の一実施の形態の放射線計装システムを示す。図１のシステムは、図８のシステムに比べて、既知の単色エネルギ放射線を発生する線源６が追加設置されている。この線源６からの放射線をシンチレーション型放射線検出器１で検出し、光電子増倍管２、キャパシタ３、増幅器４、波高弁別回路７、カウンタ回路８、CPU９の順に送って処理することにより、光電子増倍管２の増倍率低下を確認することができる。このようにして確認された光電子増倍管２の増倍率低下は種々の方法で補償することができる。
【００２２】
線源６は、例えば60Coであって、検出すべき放射線レベルに影響を与えない程度に小さいものであることが望ましい。線源６が十分に小さければ、これを常時設置しておいて、光電子増倍管２の増倍率低下を常時監視することができる。
【００２３】
図２は、図１のシステムで、電源５を調整して、光電子増倍管２の印加電圧HVを変化させた場合の波高分布の変化を示している。すなわち図２で、点線２１の分布は実線２２よりも印加電圧HVが高い場合を示している。図２に示すように、印下電圧HVを上げると、光電子増倍管２の増倍率が増加し、光電子増倍管２の信号（光電ピーク波高）レベルが高くなる。したがって、印下電圧HVを上げることによって、光電子増倍管２の増倍率の低下を補償し、もとの増倍率に戻すことができる。
【００２４】
図３は、図１のシステムで、増幅器４のゲインを変化させた場合の波高分布の変化を示している。すなわち図３で、点線３１の分布は実線３２よりも増幅器のゲインが大きい場合を示している。図３に示すように、増幅器４のゲインを上げれば、波高レベルが一様に増加する。したがって、高温下で、光電子増倍管２の増倍率が低下した場合、増幅器４のゲインを上げれば、もとの増倍率に戻すことができる。
【００２５】
図４の点線４１は、図１のシステムで、光電子増倍管２の増倍率が下がり、光電ピークがホワイトノイズと重なった状態の波高分布を示す。図４の実線４２は増倍率低下前の波高分布を示している。点線４１の分布状況の場合、ホワイトノイズと光電ピークの弁別が困難となる。
【００２６】
このような状態となることを避けるために、予めホワイトノイズのレベルを確認し、光電子増倍管増倍率がホワイトノイズを弁別できるレベルであることを判定することができる。
【００２７】
また、線源６によるピークサーチで確認し、両者を弁別できるレベルを自動設定することができる。この弁別レベルは、たとえば、放射線の波高分布とホワイトノイズの波高分布の両ピークの中央値とすればよい。
【００２８】
図５は、図１のシステムで、光電子増倍管２の検出効率が低下した場合の状態の波高分布を示す。すなわち図５で、点線５１は、実線５２に比べて、光電子増倍管２の検出効率が低下した場合を示しており、検出効率が低下するとカウント値が一様に低下することがわかる。このグラフからわかるように、光電ピークのカウント値を確認することで、検出効率を確認できる。したがって、図１のシステムで、校正工程の都度、線源６を一時的に配置する（常時設置ではない）測定方法の場合には、線源６と検出器１の相対的設置位置を常に同一とすることが好ましいことがわかる。
【００２９】
次に、図１のシステムで、光電ピークの波高とエネルギは、比例関係にある。このため、測定対象核種が明確である場合、線源６からの放射線の波高をもとに、測定対象核種からの波高レベルを求め、測定すべき波高の上限と下限を設定できる。この方法を、図６を用いて以下に説明する。
【００３０】
図６は、測定核種が137Csであり、線源６として60Coを使う場合に、測定対象とする波高の上限と下限を設定した状態を示す。すなわち、図６で、線源60Coのピーク波高が１２５０ｋｅＶであり、測定対象核種137Csのピーク波高が６６２ｋｅＶであることが既知であるから、これらのピーク波高の比に基いて、測定対象核種137Csのピーク波高の位置を予測し、このピーク波高の位置を挟むようにして、測定対象核種137Csの測定のための波高の上限と下限を設定し、それらの間（ウィンドウ）で測定を行えばよい。
【００３１】
図７は、本発明の第２の実施の形態の放射線計装システムである。図１と共通の部分には共通の符号を付して、説明を適宜省略する。図７では、図１のキャパシタ３、増幅器４、電源５、波高弁別回路７、カウンタ回路８、CPU９をまとめて測定系１０として表している。この実施の形態では、光電子増倍管２に温度計１１が取り付けられ、その出力が温度測定装置１２に送られる。また温度測定装置１２の出力が、測定系１０に与えられる。この測定系１０は、温度の履歴を記憶するメモリ機能も有している。
【００３２】
図７のシステムによって、光電子増倍管２の温度履歴に応じた増倍率の低下を予測することができる。したがって、この予測に応じて、増倍率の低下を補償することが可能である。
【００３３】
すなわち、図７のシステムで、あらかじめ、光電子増倍管２の増倍率の低下と光電子増倍管２の温度の履歴の関係を一般的に求めておいて、これを測定系１０に記憶させておく。さらに、実際の光電子増倍管２の温度の履歴を測定系１０に記憶し、これらを評価することによって、光電子増倍管２の増倍率の低下を予測することができる。
【００３４】
図７のシステムで、線源６により、温度履歴による光電子増倍管２の増倍率低下を随時確認することができる。ただし、線源６の設置を省略することもできる。
また、図７のシステムで、光電子増倍管２の温度の履歴と増幅器４（図１）に起因するホワイトノイズのレベルから寿命を予測することができる。さらに、実測した光電子増倍管２の増倍率が上記予測から大幅にずれている場合は、このシステム全体のどこかに異常があることがわかり、それによってシステムの診断を行うことができる。
【００３５】
【発明の効果】
以上説明したように、本発明によれば、放射線計装システムにおける光電子増倍管の増倍率の低下を考慮することによって、高温化でも信頼性の高い放射線計装システムおよびその健全性診断方法ならびに放射線計測方法を提供できる。
【図面の簡単な説明】
【図１】本発明に係る放射線計装システムの一実施の形態の概略構成図。
【図２】本発明に係るシンチレーション型放射線検出器・光電子増倍管の波高分布の、光電子増倍管の印加電圧による変化を示すグラフ。
【図３】本発明に係るシンチレーション型放射線検出器・光電子増倍管の波高分布の、増幅器ゲインによる変化を示すグラフ。
【図４】本発明に係るシンチレーション型放射線検出器・光電子増倍管の波高分布の、増倍率低下による変化を示すグラフ。
【図５】本発明に係るシンチレーション型放射線検出器・光電子増倍管の波高分布の、検出効率変化による変化を示すグラフ。
【図６】本発明に係るシンチレーション型放射線検出器・光電子増倍管の波高分布を示すグラフであって、測定核種が137Csで、60Coの線源を使う場合に、測定波高の上限と下限を設定する方法の例を示す。
【図７】本発明に係る放射線計装システムの他の実施の形態の概略構成図。
【図８】従来の放射線計装システムの概略構成図。
【図９】従来の放射線計装システムにおける光電子増倍管の増倍率の時間変化を示すグラフ。
【図１０】従来の放射線計装システムにおける一般的波高分布を示すグラフ。
【符号の説明】
１…シンチレーション型放射線検出器、２…光電子増倍管、３…キャパシタ、４…増幅器、５…電源、６…線源、７…波高弁別回路、８…カウンタ回路、９…CPU、１０…測定系、１１…温度計、１２…温度測定装置。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation instrumentation system using a scintillation type radiation detector and a photomultiplier tube (PMT), and particularly to a radiation instrumentation system suitable for use at high temperatures, and a health diagnostic method for the system, And a radiation measurement method.
[0002]
[Prior art]
An example of a radiation instrumentation system using a conventional scintillation type radiation detector and a photomultiplier is shown in FIG. That is, the radiation is detected by the scintillation type radiation detector 1, the optical output signal of the detector 1 is multiplied by the photomultiplier tube 2, and the output of the photomultiplier tube 2 is amplified by the amplifier 4 through the capacitor 3. To do. The output of the amplifier 4 is sent and processed in the order of the wave height discriminating circuit 7, the counter circuit 8, and the CPU (central processing unit) 9. Reference numeral 5 in the figure is a power source for applying an applied voltage HV to the photomultiplier tube 2.
[0003]
[Problems to be solved by the invention]
FIG. 9 shows temperature characteristics of a general photomultiplier tube. As can be seen from this figure, the multiplication factor of the photomultiplier tube gradually decreases with time. In addition, the lowering of the multiplication factor is faster at the high temperature indicated by the dotted line 91 than at the low temperature indicated by the solid line 92.
[0004]
FIG. 10 shows a distribution of output wave heights of a photomultiplier tube obtained by multiplying a signal of a general scintillation type detector. The peak value of the photoelectric peak in the figure is a value proportional to the energy of the radiation. In general, if there is no change in the multiplication factor of the photomultiplier tube, the peak value of the radiation of a specific energy is always the same. Further, in the region where the wave height is low, there is white noise of a circuit system such as an amplifier. Generally, in order to discriminate between white noise and a photoelectric peak and obtain a photoelectric peak, a discrimination level is set, and only a signal in a range equal to or higher than the discrimination level is measured.
[0005]
In the conventional method, it was found that the measurement is affected only when the multiplication factor of the photomultiplier tube is lower than the wave height discrimination level. For this reason, improvement in the reliability of the radiation instrumentation system has been desired particularly in the case of use at high temperatures where the reduction in multiplication factor is remarkable.
[0006]
The present invention solves the above-described problems, and an object of the present invention is to provide a radiation instrumentation system that is highly reliable even at high temperatures, a soundness diagnostic method thereof, and a radiation measurement method.
[0011]
[Means for Solving the Problems]
The present invention achieves the above object, and the invention of claim 1 is directed to a scintillation type radiation detector, a photomultiplier tube for multiplying an optical signal from the radiation detector, and the photomultiplier tube. And a means for measuring a temperature near the photomultiplier tube and storing a history of the temperature, and a preset temperature history of the photomultiplier tube And a compensation means for compensating for a decrease over time in the multiplication factor of the photomultiplier tube based on the stored temperature history based on the relationship between the photomultiplier tube and the multiplication factor of the photomultiplier tube. Radiation instrumentation system.
According to the first aspect of the present invention, it is possible to provide a highly reliable radiation instrumentation system even at a high temperature where the reduction of the multiplication factor of the photomultiplier tube is remarkable regardless of the presence or absence of the radiation source.
[0016]
Next, in the invention according to claim 10, in the compensation step, based on the wave height distribution obtained in the source wave height distribution measuring step, the applied voltage of the photomultiplier tube is set so that the wave height distribution becomes a predetermined level. The radiation measuring method according to claim 7, 8 or 9, further comprising a step of adjusting
According to the tenth aspect of the invention, the operational effect of the seventh, eighth or ninth aspect of the invention can be obtained, and highly reliable radiation measurement can be performed by adjusting the voltage applied to the photomultiplier tube.
[0020]
Next, the invention of claim 5 is a radiation having a scintillation type radiation detector, a photomultiplier tube for multiplying an optical signal from the radiation detector, and an amplifier for amplifying the output of the photomultiplier tube. In the method for diagnosing the soundness of an instrumentation system, the photoelectron is calculated from the relationship between the preset temperature history of the photomultiplier tube and the multiplication factor of the photomultiplier tube, and the measured temperature history of the photomultiplier tube. Radiation comprising: a step of calculating a multiplication factor of a multiplier tube; and a step of comparing the calculated multiplication factor of the photomultiplier tube with the measured multiplication factor of the photomultiplier tube. This is an instrumentation system health diagnostic method.
According to the invention of claim 5 , the soundness of the radiation instrumentation system can be diagnosed in consideration of a decrease in the multiplication factor of the photomultiplier tube at high temperature.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. However, parts common to the prior art are denoted by common reference numerals, and description thereof will be omitted as appropriate.
FIG. 1 shows a radiation instrumentation system according to an embodiment of the present invention. The system of FIG. 1 is additionally provided with a radiation source 6 that generates known monochromatic energy radiation as compared to the system of FIG. The radiation from the radiation source 6 is detected by the scintillation type radiation detector 1 and sent to the photomultiplier tube 2, capacitor 3, amplifier 4, wave height discriminating circuit 7, counter circuit 8, and CPU 9 in this order for processing. A reduction in multiplication factor of the multiplier tube 2 can be confirmed. Such multiplication factor reduction in photomultiplier tubes 2 which are confirmed by the Ru can be compensated in various ways.
[0022]
The radiation source 6 is preferably 60 Co, for example, and is small enough not to affect the radiation level to be detected. If the source 6 is sufficiently small, keep installed this constantly, Ru can monitor multiplication factor reduction of the photomultiplier tube 2 at all times.
[0023]
FIG. 2 shows a change in the wave height distribution when the power supply 5 is adjusted and the applied voltage HV of the photomultiplier tube 2 is changed in the system of FIG. That is, in FIG. 2, the distribution of the dotted line 21 indicates a case where the applied voltage HV is higher than that of the solid line 22. As shown in FIG. 2, when the stamp voltage HV is increased, the multiplication factor of the photomultiplier tube 2 is increased and the signal (photoelectric peak wave height) level of the photomultiplier tube 2 is increased. Thus, by raising the indicia under voltage HV, and compensate for the reduction of the multiplication factor of the photomultiplier 2, Ru can be returned to the original multiplication factor.
[0024]
FIG. 3 shows changes in the pulse height distribution when the gain of the amplifier 4 is changed in the system of FIG. That is, in FIG. 3, the distribution of the dotted line 31 indicates a case where the gain of the amplifier is larger than that of the solid line 32. As shown in FIG. 3, when the gain of the amplifier 4 is increased, the wave height level increases uniformly. Therefore, under high temperature, if the multiplication factor of the photomultiplier tube 2 is reduced, by raising the gain of the amplifier 4, Ru can be returned to the original multiplication factor.
[0025]
A dotted line 41 in FIG. 4 shows a wave height distribution in a state where the multiplication factor of the photomultiplier tube 2 is lowered and the photoelectric peak overlaps with white noise in the system of FIG. A solid line 42 in FIG. 4 indicates the wave height distribution before the multiplication factor is lowered. In the case of the distribution state of the dotted line 41, it is difficult to distinguish white noise from photoelectric peaks.
[0026]
To avoid becoming such a state, advance check the level of the white noise, the photomultiplier multiplication factor Ru can be determined to be a level capable of discriminating the white noise.
[0027]
Also, check the I Lupi Kusachi to source 6, Ru can be automatically set the level that can be distinguished both. The discrimination level may be, for example, the median value of both peaks of the radiation wave height distribution and the white noise wave height distribution.
[0028]
FIG. 5 shows the wave height distribution in the state where the detection efficiency of the photomultiplier tube 2 is lowered in the system of FIG. That is, in FIG. 5, the dotted line 51 shows a case where the detection efficiency of the photomultiplier tube 2 is lower than that of the solid line 52, and it can be seen that the count value decreases uniformly as the detection efficiency decreases. As can be seen from this graph, the detection efficiency can be confirmed by checking the count value of the photoelectric peak. Therefore, in the system of FIG. 1, in the case of a measurement method in which the radiation source 6 is temporarily arranged (not always installed) at every calibration process, the relative installation positions of the radiation source 6 and the detector 1 are always the same. it is preferable that it is that young to be.
[0029]
Next, in the system of FIG. 1, the wave height and energy of the photoelectric peak are in a proportional relationship. For this reason, when the measurement target nuclide is clear, the wave height level from the measurement target nuclide can be obtained based on the wave height of the radiation from the radiation source 6, and the upper and lower limits of the wave height to be measured can be set. This method will be described below with reference to FIG.
[0030]
FIG. 6 shows a state in which the upper and lower limits of the wave height to be measured are set when the measurement nuclide is 137 Cs and 60 Co is used as the radiation source 6. That is, in FIG. 6, since it is known that the peak wave height of the radiation source 60 Co is 1250 keV and the peak wave height of the measurement target nuclide 137 Cs is 662 keV, the measurement target nuclide is based on the ratio of these peak wave heights. predicts the location of the peak height of the 137 Cs, so as to sandwich the position of the peak wave height, to set the upper and lower height for measurement of the measurement target nuclide 137 Cs, by performing measurements between them (window) not good.
[0031]
FIG. 7 shows a radiation instrumentation system according to the second embodiment of the present invention. Portions common to those in FIG. 1 are denoted by common reference numerals, and description thereof is omitted as appropriate. In FIG. 7, the capacitor 3, the amplifier 4, the power supply 5, the wave height discrimination circuit 7, the counter circuit 8, and the CPU 9 of FIG. 1 are collectively represented as a measurement system 10. In this embodiment, a thermometer 11 is attached to the photomultiplier tube 2, and its output is sent to the temperature measuring device 12. The output of the temperature measuring device 12 is given to the measuring system 10. The measurement system 10 also has a memory function for storing a temperature history.
[0032]
With the system of FIG. 7, it is possible to predict a decrease in multiplication factor according to the temperature history of the photomultiplier tube 2. Therefore, according to this prediction, Ru can der to compensate for the reduction of the multiplication factor.
[0033]
That is, in the system of FIG. 7, the relationship between the decrease in the multiplication factor of the photomultiplier tube 2 and the temperature history of the photomultiplier tube 2 is generally obtained in advance, and this is stored in the measurement system 10. deep. Furthermore, the actual temperature history of the photomultiplier tube 2 is stored in the measurement system 10, and by evaluating these, a decrease in the multiplication factor of the photomultiplier tube 2 can be predicted.
[0034]
In the system of FIG. 7, it is possible to confirm at any time the reduction in multiplication factor of the photomultiplier tube 2 due to the temperature history by the radiation source 6. However, the installation of the radiation source 6 can be omitted.
Further, in the system of FIG. 7, the temperature history and the amplifier of a photomultiplier tube 2 4 Ru can predict the service life from the level of the white noise caused by the (Figure 1). Further, if the actually measured multiplication factor of the photomultiplier tube 2 is largely deviated from the above prediction, we see that there is an abnormality in somewhere in the entire system, thereby Ru can diagnose the system.
[0035]
【The invention's effect】
As described above, according to the present invention, a radiation instrumentation system that is highly reliable even at high temperatures, a soundness diagnosis method thereof, and A radiation measurement method can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an embodiment of a radiation instrumentation system according to the present invention.
FIG. 2 is a graph showing changes in the wave height distribution of the scintillation type radiation detector / photomultiplier according to the present invention depending on the applied voltage of the photomultiplier;
FIG. 3 is a graph showing a change in the wave height distribution of the scintillation type radiation detector / photomultiplier according to the present invention due to the amplifier gain.
FIG. 4 is a graph showing a change in the wave height distribution of a scintillation type radiation detector / photomultiplier according to the present invention due to a decrease in multiplication factor.
FIG. 5 is a graph showing a change in the wave height distribution of a scintillation type radiation detector / photomultiplier according to the present invention due to a change in detection efficiency.
FIG. 6 is a graph showing the wave height distribution of a scintillation type radiation detector / photomultiplier tube according to the present invention, where the measurement nuclide is 137 Cs and a 60 Co radiation source is used, An example of how to set the lower limit is shown.
FIG. 7 is a schematic configuration diagram of another embodiment of a radiation instrumentation system according to the present invention.
FIG. 8 is a schematic configuration diagram of a conventional radiation instrumentation system.
FIG. 9 is a graph showing a change with time of a multiplication factor of a photomultiplier tube in a conventional radiation instrumentation system.
FIG. 10 is a graph showing a general wave height distribution in a conventional radiation instrumentation system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Scintillation type radiation detector, 2 ... Photomultiplier tube, 3 ... Capacitor, 4 ... Amplifier, 5 ... Power source, 6 ... Radiation source, 7 ... Wave height discrimination circuit, 8 ... Counter circuit, 9 ... CPU, 10 ... Measurement System, 11 ... thermometer, 12 ... temperature measuring device.

Claims (5)

シンチレーション型放射線検出器と、この放射線検出器からの光信号を増倍する光電子増倍管と、この光電子増倍管の出力を増幅する増幅器と、を有する放射線計装システムにおいて、
前記光電子増倍管の付近の温度を測定してその温度の履歴を記憶する手段と、予め設定した前記光電子増倍管の温度履歴とその光電子増倍管の増倍率との関係に基いて、前記記憶された温度履歴により前記光電子増倍管の増倍率の経時的な低下を補償する補償手段と、を有することを特徴とする放射線計装システム。In a radiation instrumentation system comprising a scintillation type radiation detector, a photomultiplier tube for multiplying an optical signal from the radiation detector, and an amplifier for amplifying the output of the photomultiplier tube,
Based on the relationship between the preset temperature history of the photomultiplier tube and the multiplication factor of the photomultiplier tube, the means for measuring the temperature near the photomultiplier tube and storing the history of the temperature, Compensating means for compensating for a time-dependent decrease in the multiplication factor of the photomultiplier tube based on the stored temperature history, a radiation instrumentation system comprising: 前記温度履歴による光電子増倍管の増倍率低下を随時確認するために、既知の単色エネルギ放射線を発生する線源をさらに有することを特徴とする請求項１に記載の放射線計装システム。The radiation instrumentation system according to claim 1, further comprising a radiation source that generates known monochromatic energy radiation in order to confirm a reduction in multiplication factor of the photomultiplier tube due to the temperature history. 前記予め設定した前記光電子増倍管の温度履歴とその光電子増倍管の増倍率との関係と、前記記憶された温度履歴と、前記増幅器のホワイトノイズのレベルとから寿命を予測する手段をさらに有すること、を特徴とする請求項１又は２に記載の放射線計装システム。Means for predicting the lifetime from the preset temperature history of the photomultiplier tube and the multiplication factor of the photomultiplier tube, the stored temperature history, and the level of white noise of the amplifier; radiation instrumentation system according to claim 1 or 2 that is characterized in having. 請求項１乃至３いずれか１項に記載の放射線計装システムを用いた放射線計測方法。A radiation measurement method using the radiation instrumentation system according to claim 1. シンチレーション型放射線検出器と、この放射線検出器からの光信号を増倍する光電子増倍管と、この光電子増倍管の出力を増幅する増幅器と、を有する放射線計装システムの健全性を診断する方法において、
予め設定した前記光電子増倍管の温度履歴とその光電子増倍管の増倍率の関係と、実測した前記光電子増倍管の温度履歴とからその光電子増倍管の増倍率を計算する工程と、前記計算された光電子増倍管の増倍率と実測されたその光電子増倍管の増倍率とを比較する工程と、を有することを特徴とする放射線計装システムの健全性診断方法。Diagnosing the health of a radiation instrumentation system having a scintillation type radiation detector, a photomultiplier tube for multiplying an optical signal from the radiation detector, and an amplifier for amplifying the output of the photomultiplier tube In the method
Calculating the multiplication factor of the photomultiplier tube from the relationship between the preset temperature history of the photomultiplier tube and the multiplication factor of the photomultiplier tube, and the measured temperature history of the photomultiplier tube; A method for diagnosing the health of a radiation instrumentation system, comprising the step of comparing the calculated multiplication factor of the photomultiplier tube with the actually measured multiplication factor of the photomultiplier tube.
JP2000391902A 2000-12-25 2000-12-25 Radiation instrumentation system, health diagnosis method thereof, and radiation measurement method Expired - Fee Related JP4454840B2 (en)

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