JP4371535B2

JP4371535B2 - Radiation instrumentation system calibration method

Info

Publication number: JP4371535B2
Application number: JP2000135976A
Authority: JP
Inventors: 直敬小田; 司菊池; 求高橋; 豊福武
Original assignee: Toshiba Corp; Toshiba Plant Systems and Services Corp
Current assignee: Toshiba Corp; Toshiba Plant Systems and Services Corp
Priority date: 2000-05-09
Filing date: 2000-05-09
Publication date: 2009-11-25
Anticipated expiration: 2020-05-09
Also published as: JP2001318160A

Description

【０００１】
【発明の属する技術分野】
本発明は、容器に放射性溶液を入れてその容器の外側に設置した放射線検出器（以下、検出器という）によってその放射性溶液中の放射能の量を測定する放射線計装システムで、そのシステムを校正する方法に関する。
【０００２】
【従来の技術】
従来の放射線計装システム校正方法は、例えば特開平５−297184号公報に開示されている。従来の放射線計装システム校正方法を図６を参照して以下に説明する。容器１は、通常測定時に放射性溶液を収容するための直方体形状の容器であって、例えばステンレス鋼製である。この容器１の側面に垂直な水平方向にｘ軸およびｙ軸を取り、鉛直方向にｚ軸を取る。この容器１の下方にはこれに接して例えばポリエチレン製のブロック２があって、このブロック２には側面からｘ軸方向に穴３が開けられている。穴３には棒状の検出器４が挿入され、検出器４がｘ軸方向に向けて配置されている。検出器のケーブル５は、穴３から外に取り出される。この放射線計装システムの校正にあたっては、容器１内に放射性溶液を入れない状態で、校正用の放射線源（以下、単に線源という）６を容器１内に配置し、この線源６をｘ軸、ｙ軸、ｚ軸の各方向に移動して、このときの検出器４の出力により、検出効率すなわち指示値／放射線量率の値を求める。
【０００３】
【発明が解決しようとする課題】
上記の従来の方式では、検出効率を求める場合、線源を多数の測定点数に移動して測定を行なう必要があり、煩雑であった。本発明は、精度を確保した上で、測定点数を削減する方法を提供することを目的とする。
【０００４】
【課題を解決するための手段】
上記目的を達成するために、請求項１の発明の放射線計装システム校正方法では、放射線検出器を、測定状態の位置であるほぼ直方体形状の測定対象容器の外側下部位置に設置し、放射線源を前記測定対象容器内の一水平面内の複数の位置に移動させてその一水平面内の感度分布を前記放射線検出器の指示値から求め、前記放射線検出器とは別の放射線検出器によって鉛直方向感度分布を相対値として求め、前記測定対象容器内水平面内の感度分布が各高さ位置で相似であると仮定して、前記一水平面内の感度分布と鉛直方向感度分布とに基づいて、線源の位置と線源強度により三次元的検出効率を求める。
【０００５】
又、請求項２の発明の放射線計装システム校正方法では、放射線検出器を測定状態の位置であるほぼ直方体形状の測定対象容器の外側下部位置に設置し、放射線源を前記測定対象容器内の複数の水平面内のそれぞれ複数の位置に移動させて前記複数の水平面内の感度分布を前記放射線検出器の指示値から求め、前記放射線検出器とは別の放射線検出器によって鉛直方向感度分布を相対値として求め、前記複数の水平面内感度分布と鉛直方向感度分布から内外挿することにより、線源の位置と線源強度により三次元的検出効率を求める。
【０００６】
さらに、請求項３の発明の放射線計装システム校正方法では、放射線検出器を、測定状態の位置であるほぼ直方体状の測定対象容器の外側下部位置に、放射線検出器の長手方向の軸（以下、ｘ軸という）が水平になるように設置し、線源を前記測定対象容器内のｘ軸に垂直な一鉛直平面（以下、ｘ平面という）内の複数の位置に移動させてそのｘ平面内の感度分布を前記放射線検出器の指示値から求め、前記測定対象容器外の校正装置によってｘ軸方向感度分布を相対値として求め、前記ｘ平面内の感度分布が各ｘ軸方向位置で相似であると仮定して、前記ｘ平面内の感度分布とｘ軸方向感度分布とに基づいて、線源の位置と線源強度により三次元的検出効率を求める。
【０００７】
さらに、請求項４の発明の放射線計装システム校正方法では、放射線検出器を、測定状態の位置であるほぼ直方体状の測定対象容器の外側下部位置に、放射線検出器の長手方向の軸（以下、ｘ軸という）が水平になるように設置し、線源を前記測定対象容器内のｘ軸に垂直な複数の鉛直平面（以下、ｘ平面という）内のそれぞれ複数の位置に移動させて前記複数のｘ平面内の感度分布を前記放射線検出器の指示値から求め、前記測定対象容器外の校正装置によってｘ軸方向感度分布を相対値として求め、前記ｘ平面内の感度分布が前記ｘ軸方向感度分布に従って滑らかに変化すると仮定して、前記複数のｘ平面内感度分布とｘ軸方向感度分布から内外挿することにより、線源の位置と線源強度により三次元的検出効率を求めることを特徴とする。
【０００８】
さらに、請求項５の発明の放射線計装システム校正方法では、放射線検出器を、測定状態の位置であるほぼ直方体状の測定対象容器の外側下部位置に、放射線検出器の長手方向の軸（以下、ｘ軸という）が水平になるように設置し、線源を前記測定対象容器内のｘ軸を含む一鉛直平面（以下、ｙ平面という）内の複数の位置に移動させてそのｙ平面内の感度分布を前記放射線検出器の指示値から求め、前記放射線検出器とは別の放射線検出器によって、ｘ軸方向と垂直でかつ水平な方向（以下、ｙ軸方向という）の感度分布を相対値として求め、前記ｙ平面内の感度分布が各ｙ軸方向位置で相似であると仮定して、前記ｙ平面内の感度分布とｙ軸方向感度分布とに基づいて、線源の位置と線源強度により三次元的検出効率を求めることを特徴とする。
【０００９】
さらに、請求項６の発明の放射線計装システム校正方法では、放射線検出器を、測定状態の位置であるほぼ直方体状の測定対象容器の外側下部位置に、放射線検出器の長手方向の軸（以下、ｘ軸という）が水平になるように設置し、線源を前記測定対象容器内のｘ軸を含む鉛直平面およびこの鉛直平面に平行な少なくとも一つの鉛直平面（これらの鉛直平面を以下、ｙ平面という）内のそれぞれ複数の位置に移動させて前記複数のｙ平面内の感度分布を前記放射線検出器の指示値から求め、前記複数のｙ平面内感度分布とｙ軸方向の感度分布から内外挿することにより、線源の位置と線源強度により三次元的検出効率を求める。
【００１０】
さらに、請求項７の発明の放射線計装システム校正方法では、請求項１または２と、請求項３または４と、請求項５または６を組合せる。
【００１１】
さらに、請求項８の発明は、前記測定対象容器の下部でかつ前記放射線検出器の上方に水平に遮へい板を設け、この遮へい板の前記放射線検出器の上方位置にｘ軸方向に延びるウィンドウを設け、前記測定対象容器外の校正装置にも同様の遮へい板およびウィンドウを設け、前記放射線検出器軸上１点のみでy軸方向の分布を測定し、これをもとに全x軸の補正を行うことを特徴とする、請求項３、４または７の放射線計装システム校正方法である。
【００１２】
さらに、請求項９の発明は、前記測定対象容器が軸を鉛直とするほぼ円筒状で、放射線検出器を前記測定対象容器の上面から挿入して設置する放射線計装システム校正方法であって、前記円筒の軸方向をｘ軸方向、円筒の中心から外側方向をｚ軸方向、円筒の同心円周方向をｙ軸方向と見做して適用することを特徴とする、請求項１ないし８のいずれかの放射線計装システム校正方法である。
本発明によれば、線源の移動点数が削減できるので、校正を簡略化した放射線計装システム校正方法を得ることができる。
【００１３】
【発明の実施の形態】
以下の説明で、従来と同じ部分については共通の符号を用いることによって、説明を省略する。
【００１４】
［第１の実施の形態］［請求項１、２対応］
図１は本発明の第１の実施の形態の放射線計装システムを示す。
図１（ａ）に示すように、放射線検出器（以下、検出器という）４を測定状態の位置（測定対象容器１の外側下部）のブロック２の穴３内に設置する。線源６を測定対象容器１（直方体状）内の多数の決められた位置に移動させ３次元の感度分布を検出器４の指示値から求め、その分布・線源の位置・線源強度より検出効率（指示値／放射線量率）を求める際に、図１（ｂ）に示す鉛直方向（以下、z軸方向とも称す）の感度分布は、図示しない別の検出器で求めたものを用いる。別の検出器で求めた分布を相対値として使用し、一水平面の値で補正する。この場合、測定対象容器４内の水平面内の感度分布が各高さ位置で相似であると仮定する。すなわちこの実施の形態では線源６は、ｚ軸方向位置を固定して、一水平面内で移動する。
【００１５】
鉛直方向の感度部分布については、別の検出器で相対値として求め、これを使用する。検出器ごとに感度が異なるので、図１（ｂ）の曲線は相対的なものである。
【００１６】
この実施の形態の変形例として、図１（ｃ）に示すように、z軸方向の感度分布を２点以上測定し、これらの点で絶対感度補正を行うとともに、残りの点は別の検出器で求めた相対分布を内外挿することもできる。この場合、測定対象容器１内の水平面内の感度分布が、鉛直方向感度分布に従って滑らかに変化すると仮定して、複数の水平面内感度分布と鉛直方向感度分布から内外挿する。この変形例では、測定点数が若干多くなるが、精度が高くなる。
【００１７】
［第２の実施の形態］［請求項３、４対応］
図２は本発明の第２の実施の形態の放射線計装システムを示す。
図２（ａ）および（ｂ）に示すように、x軸方向の感度分布は、この放射線計装システムとは別の図示しない校正装置（相対感度校正用）で求めた分布を相対値として使用し、ｘ軸に垂直な一鉛直面（以下、ｘ平面という）の値で補正する。この実施の形態では、ｘ平面内の感度分布がｘ軸方向各位置で相似であると仮定している。
【００１８】
この実施の形態の変形例として、図２（ｃ）に示すように、x軸方向の感度分布を２点以上測定し、この点で絶対感度補正を行うとともに、残りの点は校正装置で求めた相対分布を内外挿することもできる。この内外挿においては、ｘ平面内の感度分布がｘ軸方向感度分布に従って滑らかに変化すると仮定している。この変形例では、測定点数が若干多くなるが、精度が高くなる。
【００１９】
［第３の実施の形態］［請求項５、６対応］
図３は本発明の第３の実施の形態の放射線計装システムを示す。
図３（ａ）および（ｂ）に示すように、y軸方向の感度分布は、別の検出器で求めた分布を相対値として使用し、x軸の値で絶対補正する。検出器ごとに感度が異なるので、図２（ｂ）の曲線は相対的なものである。
【００２０】
この実施の形態の変形例として、図３（ｃ）に示すように、y軸方向の感度分布を２点以上測定し、この点で絶対感度補正を行うとともに、残りの点は校正装置で求めた相対分布を内外挿することもできる。この場合、測定対象容器１内のｙ軸方向に垂直な平面（以下、ｙ平面という）内の感度分布が、ｙ軸方向感度分布に従って滑らかに変化すると仮定して、複数のｙ平面内感度分布と鉛直方向感度分布から内外挿する。この変形例では、測定点数が若干多くなるが、精度が高くなる。
【００２１】
［他の実施の形態］［請求項９対応］
ここで、以上示した第１〜第３の実施の形態を組み合せることが可能であることはいうまでもない。
【００２２】
［第４の実施の形態］［請求項８対応］
図４は本発明の第４の実施の形態の放射線計装システムを示す。
図４（ａ）に示すように、容器１の底部で検出器４の上方に水平に遮へい板10が挿入されている。この遮へい板10は放射線を遮へいするものであって、例えば中性子測定用にはカドミウムからできている。この遮へい板10の、検出器４の真上の部分には、ｘ軸方向に延びる細長い窓（ウィンドウ）11が設けられている。この場合は、図４（ｂ）に示すように、検出器４に入る放射線の入射角がｙ軸方向に広がらない。この実施の形態の場合、ｘ軸方向感度分布を相対値として求めるための容器１外の校正装置（図示せず）にも同様のウィンドウを設け、ｘ軸上の１点のみでｙ軸の分布を測定し、これを基に全x軸の補正を行う。
【００２３】
［第５の実施の形態］［請求項９対応］
図５は本発明の第５の実施の形態の放射線計装システムを示す。
測定対象容器51は円筒状で、ケーブル55の接続された棒状の検出器54を、円筒上面の穴53から挿入して設置する。この場合、円筒の鉛直軸（円筒z軸）をx軸、円筒の中心から外側方向の軸（r軸）をz軸、円筒の同心円周方向軸（θ軸）をy軸とみなすことにより、上記第１〜第４の実施の形態と同様の説明が成り立つ。
【００２４】
【発明の効果】
本発明によれば、線源の移動点数が削減できるので、校正を簡略化した放射線計装システム校正方法を得ることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態の放射線計装システムの校正方法を示す説明図であって、（ａ）は同システムの模式的斜視図、（ｂ）は１点で補正する場合のｚ軸の指示値分布曲線、（ｃ）は２点以上で補正する場合のｚ軸の指示値分布曲線。
【図２】本発明の第２の実施の形態の放射線計装システムの校正方法を示す説明図であって、（ａ）は同システムの模式的斜視図、（ｂ）は１点で補正する場合のｘ軸の指示値分布曲線、（ｃ）は２点以上で補正する場合のｘ軸の指示値分布曲線。
【図３】本発明の第３の実施の形態の放射線計装システムの校正方法を示す説明図であって、（ａ）は同システムの模式的斜視図、（ｂ）は１点で補正する場合のｙ軸の指示値分布曲線、（ｃ）は２点以上で補正する場合のｙ軸の指示値分布曲線。
【図４】本発明の第４の実施の形態の放射線計装システムの校正方法を示す説明図であって、（ａ）は同システムの模式的斜視図、（ｂ）は１点で補正する場合のｙ軸の指示値分布曲線。
【図５】本発明の第５の実施の形態の放射線計装システムを示す模式的斜視図。
【図６】従来の放射線計装システムを示す模式的斜視図。
【符号の説明】
１，51…容器、２…ブロック、３，53…穴、４，54…検出器、５，55…ケーブル、６…線源、10…遮へい板、11…ウィンドウ。[0001]
BACKGROUND OF THE INVENTION
The present invention is a radiation instrumentation system for measuring the amount of radioactivity in a radioactive solution by a radiation detector (hereinafter referred to as a detector) placed in the container and placing the radioactive solution in the container. It relates to a method of proofreading.
[0002]
[Prior art]
A conventional radiation instrumentation system calibration method is disclosed, for example, in JP-A-5-297184. A conventional radiation instrumentation system calibration method will be described below with reference to FIG. The container 1 is a rectangular parallelepiped container for storing a radioactive solution during normal measurement, and is made of, for example, stainless steel. The x axis and y axis are taken in the horizontal direction perpendicular to the side surface of the container 1, and the z axis is taken in the vertical direction. Below this container 1, there is a block 2 made of, for example, polyethylene in contact with this, and this block 2 has a hole 3 in the x-axis direction from the side. A rod-shaped detector 4 is inserted into the hole 3, and the detector 4 is arranged in the x-axis direction. The detector cable 5 is taken out of the hole 3. In calibrating the radiation instrumentation system, a radiation source for calibration (hereinafter simply referred to as a radiation source) 6 is placed in the container 1 without putting a radioactive solution in the container 1, and the radiation source 6 is set to x It moves in each of the axis, y-axis, and z-axis directions, and the detection efficiency, that is, the value of the indicated value / radiation dose rate is obtained from the output of the detector 4 at this time.
[0003]
[Problems to be solved by the invention]
In the conventional method described above, when obtaining the detection efficiency, it is necessary to move the radiation source to a large number of measurement points and perform measurement, which is complicated. An object of the present invention is to provide a method for reducing the number of measurement points while ensuring accuracy.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, in the radiation instrumentation system calibration method according to the first aspect of the present invention, the radiation detector is installed at the lower position outside the measurement object container having a substantially rectangular parallelepiped shape, which is the position of the measurement state, and the radiation source. Is moved to a plurality of positions in one horizontal plane in the measurement object container, and the sensitivity distribution in the horizontal plane is obtained from the indicated value of the radiation detector, and the vertical direction is determined by a radiation detector different from the radiation detector. A sensitivity distribution is obtained as a relative value, and it is assumed that the sensitivity distribution in the horizontal plane in the measurement target container is similar at each height position, and based on the sensitivity distribution in the horizontal plane and the vertical direction sensitivity distribution, the position and the source intensity of the source obtaining the three-dimensional detection efficiency.
[0005]
In the radiation instrumentation system calibration method according to the second aspect of the present invention, the radiation detector is installed at the lower position outside the measurement target container having a substantially rectangular parallelepiped shape, which is the position of the measurement state, and the radiation source is placed in the measurement target container. The sensitivity distribution in the plurality of horizontal planes is obtained from the indicated value of the radiation detector by moving to a plurality of positions in the plurality of horizontal planes, and the vertical direction sensitivity distribution is relative by a radiation detector different from the radiation detector. calculated as a value, by the inner and outer interpolating from the plurality of horizontal plane sensitivity distribution and vertical sensitivity distribution, the position and the source intensity of the source obtaining the three-dimensional detection efficiency.
[0006]
Furthermore, in the radiation instrumentation system calibration method according to the third aspect of the present invention, the radiation detector is placed in the longitudinal direction of the radiation detector (hereinafter referred to as the position of the measurement object in a substantially rectangular parallelepiped measurement target container). , The x-axis) is set to be horizontal, and the radiation source is moved to a plurality of positions in one vertical plane (hereinafter referred to as x-plane) perpendicular to the x-axis in the measurement object container. The sensitivity distribution in the x plane is obtained from the indicated value of the radiation detector, the sensitivity distribution in the x axis direction is obtained as a relative value by the calibration device outside the measurement target container, and the sensitivity distribution in the x plane is similar at each x axis direction position. assuming it is, on the basis of the sensitivity distribution and the x-axis direction sensitivity distribution of the x plane, the position and the source intensity of the source obtaining the three-dimensional detection efficiency.
[0007]
Furthermore, in the radiation instrumentation system calibration method according to the fourth aspect of the invention, the radiation detector is placed on the outer lower position of the substantially rectangular parallelepiped measuring object container, which is the position of the measurement state, in the longitudinal axis of the radiation detector (hereinafter, referred to as the radiation detector). And the x-axis) are set to be horizontal, and the radiation source is moved to a plurality of positions in a plurality of vertical planes (hereinafter referred to as x-plane) perpendicular to the x-axis in the measurement object container. Sensitivity distributions in a plurality of x planes are obtained from the indicated values of the radiation detector, the sensitivity distribution in the x-axis direction is obtained as a relative value by a calibration device outside the measurement target container, and the sensitivity distribution in the x plane is the x-axis assuming smoothly changes according to the direction sensitivity distribution, by the inner and outer interpolating from the plurality of x-plane sensitivity distribution and the x-axis direction sensitivity distribution, obtaining the three-dimensional detection efficiency by the position and the source intensity of the source It is characterized by .
[0008]
Furthermore, in the radiation instrumentation system calibration method according to the fifth aspect of the invention, the radiation detector is placed at the outer lower position of the substantially rectangular parallelepiped measurement target container, which is the position of the measurement state, in the longitudinal axis of the radiation detector (hereinafter, referred to as the radiation detector). And the x-axis) are set to be horizontal, and the radiation source is moved to a plurality of positions in one vertical plane (hereinafter referred to as the y-plane) including the x-axis in the measurement object container. The sensitivity distribution in the horizontal direction (hereinafter referred to as the y-axis direction) that is perpendicular to the x-axis direction and relative to the relative direction is obtained by a radiation detector different from the radiation detector. Assuming that the sensitivity distribution in the y plane is similar at each y-axis direction position, the position and line of the radiation source are determined based on the sensitivity distribution in the y plane and the y-axis direction sensitivity distribution. wherein determining the three-dimensional detection efficiency by the source intensity To.
[0009]
Furthermore, in the radiation instrumentation system calibration method according to the sixth aspect of the invention, the radiation detector is placed at the outer lower position of the substantially rectangular parallelepiped measurement target container, which is the position of the measurement state, in the longitudinal axis of the radiation detector (hereinafter, referred to as the radiation detector). And the x-axis) are set to be horizontal, and the radiation source is a vertical plane including the x-axis in the measurement object container and at least one vertical plane parallel to the vertical plane (these vertical planes are hereinafter referred to as y The sensitivity distribution in the plurality of y planes is obtained from the indication values of the radiation detectors, and the inside and outside of the plurality of y plane sensitivity distributions and the y axis direction sensitivity distribution are obtained. by interpolation, the position and the source intensity of the source obtaining the three-dimensional detection efficiency.
[0010]
Furthermore, in the radiation instrumentation system calibration method of the invention of claim 7, claim 1 or 2, claim 3 or 4, and claim 5 or 6 are combined.
[0011]
Further, according to the invention of claim 8, a shielding plate is provided horizontally below the measurement object container and above the radiation detector, and a window extending in the x-axis direction is provided above the radiation detector on the shielding plate. A similar shielding plate and window are also provided on the calibration device outside the measurement target container, and the distribution in the y-axis direction is measured at only one point on the radiation detector axis, and all x-axis corrections are made based on this. The radiation instrumentation system calibration method according to claim 3, 4, or 7, wherein:
[0012]
Furthermore, the invention of claim 9 is a radiation instrumentation system calibration method in which the measurement target container is substantially cylindrical with the axis vertical, and a radiation detector is inserted and installed from the upper surface of the measurement target container. the axial x-axis direction of the cylindrical, z-axis direction outwardly from the center of the cylinder, characterized in that the concentric peripheral direction of the cylinder that apply to regarded as the y-axis direction, of the claims 1 to 8 Any radiation instrumentation system calibration method.
According to the present invention, since the number of moving points of the radiation source can be reduced, a radiation instrumentation system calibration method that simplifies calibration can be obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the following description, the same reference numerals are used for the same parts as in the prior art, and the description is omitted.
[0014]
[First Embodiment] [Claims 1 and 2]
FIG. 1 shows a radiation instrumentation system according to a first embodiment of the present invention.
As shown in FIG. 1A, a radiation detector (hereinafter referred to as a detector) 4 is installed in a hole 3 of a block 2 at a position in a measurement state (outer lower portion of the measurement target container 1). The radiation source 6 is moved to a number of predetermined positions in the measurement target container 1 (cuboid), a three-dimensional sensitivity distribution is obtained from the indicated value of the detector 4, and from the distribution, the position of the radiation source, and the radiation source intensity. When obtaining the detection efficiency (indicated value / radiation dose rate), the sensitivity distribution in the vertical direction (hereinafter also referred to as the z-axis direction) shown in FIG. . The distribution obtained by another detector is used as a relative value, and corrected with the value of one horizontal plane. In this case, it is assumed that the sensitivity distribution in the horizontal plane in the measurement target container 4 is similar at each height position. That is, in this embodiment, the radiation source 6 moves within one horizontal plane with the z-axis direction position fixed.
[0015]
The sensitivity distribution in the vertical direction is obtained as a relative value by another detector and used. Since the sensitivity is different for each detector, the curve in FIG. 1B is relative.
[0016]
As a modification of this embodiment, as shown in FIG. 1C, two or more sensitivity distributions in the z-axis direction are measured, absolute sensitivity correction is performed at these points, and the remaining points are detected separately. The relative distribution obtained by the instrument can also be interpolated. In this case, assuming that the sensitivity distribution in the horizontal plane in the measurement target container 1 changes smoothly according to the vertical direction sensitivity distribution, interpolation is performed from a plurality of horizontal plane sensitivity distributions and vertical direction sensitivity distributions. In this modification, the number of measurement points is slightly increased, but the accuracy is increased.
[0017]
[Second Embodiment] [Claims 3 and 4]
FIG. 2 shows a radiation instrumentation system according to the second embodiment of the present invention.
As shown in FIGS. 2 (a) and 2 (b), the sensitivity distribution in the x-axis direction uses a distribution obtained by a calibration device (for relative sensitivity calibration) (not shown) separate from this radiation instrumentation system as a relative value. Then, it is corrected with the value of one vertical plane (hereinafter referred to as x plane) perpendicular to the x axis. In this embodiment, it is assumed that the sensitivity distribution in the x plane is similar at each position in the x-axis direction.
[0018]
As a modification of this embodiment, as shown in FIG. 2 (c), two or more sensitivity distributions in the x-axis direction are measured, absolute sensitivity correction is performed at this point, and the remaining points are obtained by a calibration device. The relative distribution can also be interpolated. In this extrapolation, it is assumed that the sensitivity distribution in the x plane changes smoothly according to the sensitivity distribution in the x-axis direction. In this modification, the number of measurement points is slightly increased, but the accuracy is increased.
[0019]
[Third Embodiment] [Corresponding to Claims 5 and 6]
FIG. 3 shows a radiation instrumentation system according to a third embodiment of the present invention.
As shown in FIGS. 3A and 3B, the sensitivity distribution in the y-axis direction is absolute corrected with the x-axis value using a distribution obtained by another detector as a relative value. Since the sensitivity differs for each detector, the curve in FIG. 2 (b) is relative.
[0020]
As a modification of this embodiment, as shown in FIG. 3C, two or more sensitivity distributions in the y-axis direction are measured, absolute sensitivity correction is performed at this point, and the remaining points are obtained by a calibration device. The relative distribution can also be interpolated. In this case, assuming that the sensitivity distribution in the plane perpendicular to the y-axis direction in the measurement target container 1 (hereinafter referred to as the y plane) changes smoothly according to the y-axis direction sensitivity distribution, a plurality of y-plane sensitivity distributions are assumed. And extrapolation from the vertical sensitivity distribution. In this modification, the number of measurement points is slightly increased, but the accuracy is increased.
[0021]
[Other Embodiments] [Corresponding to Claim 9]
Here, it is needless to say that the first to third embodiments described above can be combined.
[0022]
[Fourth Embodiment] [Corresponding to Claim 8]
FIG. 4 shows a radiation instrumentation system according to a fourth embodiment of the present invention.
As shown in FIG. 4A, a shielding plate 10 is inserted horizontally above the detector 4 at the bottom of the container 1. The shielding plate 10 shields radiation and is made of cadmium for neutron measurement, for example. An elongated window (window) 11 extending in the x-axis direction is provided in a portion of the shielding plate 10 immediately above the detector 4. In this case, as shown in FIG. 4B, the incident angle of the radiation entering the detector 4 does not spread in the y-axis direction. In the case of this embodiment, a similar window is also provided in a calibration device (not shown) outside the container 1 for obtaining the sensitivity distribution in the x-axis direction as a relative value, and the y-axis distribution is obtained only at one point on the x-axis. Is measured, and based on this, all the x-axis are corrected.
[0023]
[Fifth Embodiment] [Corresponding to Claim 9]
FIG. 5 shows a radiation instrumentation system according to a fifth embodiment of the present invention.
The container 51 to be measured is cylindrical, and a rod-shaped detector 54 connected with a cable 55 is inserted and installed through a hole 53 on the upper surface of the cylinder. In this case, by regarding the vertical axis of the cylinder (cylinder z-axis) as the x-axis, the axis outward from the center of the cylinder (r-axis) as the z-axis, and the concentric circumferential axis (θ-axis) of the cylinder as the y-axis, The same explanation as in the first to fourth embodiments is established.
[0024]
【The invention's effect】
According to the present invention, since the number of moving points of the radiation source can be reduced, a radiation instrumentation system calibration method that simplifies calibration can be obtained.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram showing a calibration method for a radiation instrumentation system according to a first embodiment of the present invention, wherein (a) is a schematic perspective view of the system, and (b) is corrected at one point. The z-axis indicated value distribution curve in the case, and (c) is the z-axis indicated value distribution curve in the case of correcting at two or more points.
FIGS. 2A and 2B are explanatory diagrams showing a calibration method for a radiation instrumentation system according to a second embodiment of the present invention, wherein FIG. 2A is a schematic perspective view of the system, and FIG. 2B is corrected by one point; X-axis indicated value distribution curve, and (c) is an x-axis indicated value distribution curve when correcting at two or more points.
FIGS. 3A and 3B are explanatory views showing a calibration method for a radiation instrumentation system according to a third embodiment of the present invention, wherein FIG. 3A is a schematic perspective view of the system, and FIG. 3B is corrected by one point; The y-axis indicated value distribution curve in the case of correction, and (c) is the y-axis indicated value distribution curve in the case of correction at two or more points.
FIGS. 4A and 4B are explanatory views showing a calibration method for a radiation instrumentation system according to a fourth embodiment of the present invention, wherein FIG. 4A is a schematic perspective view of the system, and FIG. 4B is corrected by one point; The y-axis indicated value distribution curve.
FIG. 5 is a schematic perspective view showing a radiation instrumentation system according to a fifth embodiment of the present invention.
FIG. 6 is a schematic perspective view showing a conventional radiation instrumentation system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,51 ... Container, 2 ... Block, 3,53 ... Hole, 4,54 ... Detector, 5,55 ... Cable, 6 ... Radiation source, 10 ... Shielding board, 11 ... Window.

Claims

Install the radiation detector at the lower position on the outside of the measurement target container that is in the shape of a rectangular parallelepiped.
The radiation source is moved to a plurality of positions in one horizontal plane in the measurement target container, and the sensitivity distribution in the horizontal plane is obtained from the indicated value of the radiation detector,
Obtain the vertical direction sensitivity distribution as a relative value by a radiation detector different from the radiation detector,
Assuming that the sensitivity distribution in the horizontal plane in the measurement target container is similar at each height position, based on the sensitivity distribution in the horizontal plane and the vertical sensitivity distribution, and obtaining the three-dimensional detection efficiency, radiation instrumentation systems calibration method.

Install the radiation detector at the lower position on the outside of the measurement target container in the shape of a substantially rectangular parallelepiped,
A radiation source is moved to each of a plurality of positions in a plurality of horizontal planes in the measurement target container, and a sensitivity distribution in the plurality of horizontal planes is obtained from an indication value of the radiation detector,
Obtain the vertical direction sensitivity distribution as a relative value by a radiation detector different from the radiation detector,
By interpolating from the plurality of horizontal plane sensitivity distributions and vertical direction sensitivity distributions,
And obtaining the three-dimensional detection efficiency by the position and the source intensity of the source, the radiation instrumentation systems calibration method.

The radiation detector is installed at the position of the measurement state in a substantially rectangular parallelepiped measuring object container so that the longitudinal axis of the radiation detector (hereinafter referred to as x-axis) is horizontal,
The radiation source is moved to a plurality of positions in one vertical plane (hereinafter referred to as x plane) perpendicular to the x axis in the measurement object container, and the sensitivity distribution in the x plane is obtained from the indicated value of the radiation detector. ,
Obtain the sensitivity distribution in the x-axis direction as a relative value by a calibration device outside the measurement target container,
Assuming that the sensitivity distribution in the x-plane is similar at each position in the x-axis direction, the third order is determined by the position of the source and the source intensity based on the sensitivity distribution in the x-plane and the sensitivity distribution in the x-axis direction. and obtaining the original detection efficiency, radiation instrumentation systems calibration method.

The radiation detector is installed at the position of the measurement state in a substantially rectangular parallelepiped measuring object container so that the longitudinal axis of the radiation detector (hereinafter referred to as x-axis) is horizontal,
The radiation source is moved to a plurality of positions in a plurality of vertical planes (hereinafter referred to as x planes) perpendicular to the x axis in the measurement object container, and sensitivity distributions in the plurality of x planes are moved to the radiation detector. Obtain from the indicated value,
Obtain the sensitivity distribution in the x-axis direction as a relative value by a calibration device outside the measurement target container,
Assuming that the sensitivity distribution in the x-plane changes smoothly according to the sensitivity distribution in the x-axis direction, by interpolating from the plurality of sensitivity distributions in the x-plane and the sensitivity distribution in the x-axis direction, the position of the source and the line source and obtains the three-dimensional detection efficiency by the intensity, radiation instrumentation systems calibration method.

The radiation detector is installed at the position of the measurement state in a substantially rectangular parallelepiped measuring object container so that the longitudinal axis of the radiation detector (hereinafter referred to as x-axis) is horizontal,
The radiation source is moved to a plurality of positions in one vertical plane (hereinafter referred to as y plane) including the x axis in the measurement object container, and the sensitivity distribution in the y plane is obtained from the indicated value of the radiation detector,
Using a radiation detector different from the radiation detector, a sensitivity distribution in a direction perpendicular to the x-axis direction and horizontal (hereinafter referred to as y-axis direction) is obtained as a relative value.
Assuming that the sensitivity distribution in the y plane is similar in each y-axis direction position, the third order is determined by the source position and the source intensity based on the sensitivity distribution in the y plane and the y-axis direction sensitivity distribution. and obtaining the original detection efficiency, radiation instrumentation systems calibration method.

The radiation detector is installed at the lower position outside the measurement target container, which is the position of the measurement state, so that the longitudinal axis of the radiation detector (hereinafter referred to as the x-axis) is horizontal, and the radiation source Are moved to a plurality of positions in a vertical plane including the x axis in the measurement object container and at least one vertical plane parallel to the vertical plane (these vertical planes are hereinafter referred to as y planes). a sensitivity distribution in the y plane is obtained from the indicated value of the radiation detector;
A sensitivity distribution in a direction perpendicular to the y plane (hereinafter referred to as y-axis direction) is obtained as a relative value by a calibration device outside the measurement target container,
By out interpolating from the sensitivity distribution of the plurality of y plane sensitivity distribution and the y-axis direction, and obtains a three-dimensional detection efficiency by the position and the source intensity of the source, the radiation instrumentation system calibration Method.

A radiation instrumentation system calibration method characterized by combining claim 1 or 2, claim 3 or 4, and claim 5 or 6.

A shielding plate is provided horizontally below the measurement target container and above the radiation detector, and a window extending in the x-axis direction is provided at a position above the radiation detector on the shielding plate, and calibration outside the measurement target container is performed. The apparatus is also provided with a similar shielding plate and window, and the distribution in the y-axis direction is measured only at one point on the radiation detector axis, and all x-axis corrections are performed based on this measurement. Item 8. The radiation instrumentation system calibration method according to item 3, 4 or 7.

The measurement object container is a substantially cylindrical shape whose axis is vertical, and is a radiation instrumentation system calibration method in which a radiation detector is inserted and installed from the upper surface of the measurement object container, the axial direction of the cylinder being the x-axis direction , z-axis direction outwardly from the center of the cylinder, characterized in that the concentric peripheral direction of the cylinder that apply to regarded as the y-axis direction, one of the radiation instrumentation system calibration method of claims 1 to 8 .