JP5542767B2

JP5542767B2 - Radiation monitor

Info

Publication number: JP5542767B2
Application number: JP2011210292A
Authority: JP
Inventors: 健一茂木; 勝田室
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2011-09-27
Filing date: 2011-09-27
Publication date: 2014-07-09
Anticipated expiration: 2031-09-27
Also published as: JP2013072675A

Description

この発明は、原子炉施設、使用済燃料再処理施設等の放出管理又は放射線管理に用いられる放射線モニタに関するものである。 The present invention relates to a radiation monitor used for emission management or radiation management of a nuclear reactor facility, a spent fuel reprocessing facility, or the like.

原子炉施設、使用済燃料再処理施設等で使用される放射線モニタは、放射線を検出した結果としての信号パルスの繰り返し周波数が１０ｃｐｍ（count per minute）程度から１０^７ｃｐｍ程度までの広いレンジをカバーし、レンジ切換なしで要求の精度を確保して測定することが求められている。また、放射線検出器の出力パルスの繰り返し周波数が、バックグラウンドレベルから高警報点を含む高計数率領域へ変化した場合に、計数率の速い応答が求められている。このため、計数率に反比例して時定数が変化すると共に標準偏差が一定になるように制御された計数率演算方式が広く導入されている。 Radiation monitors used in nuclear reactor facilities, spent fuel reprocessing facilities, etc. cover a wide range of signal pulse repetition frequencies from about 10 cpm (count per minute) to about 10 ⁷ cpm as a result of detecting radiation. However, it is required to ensure and measure the required accuracy without switching the range. Further, when the repetition frequency of the output pulse of the radiation detector changes from the background level to a high count rate region including a high alarm point, a response with a fast count rate is required. For this reason, a count rate calculation method in which the time constant changes in inverse proportion to the count rate and the standard deviation is controlled to be constant has been widely introduced.

この方式をベースに、従来の放射線モニタは、測定レンジを低計数率領域と高計数率領域の２つに分け、低計数率領域は標準偏差を小さく設定して測定精度を優先した測定を行い、高計数率領域は標準偏差を大きく設定して応答性を優先した測定を行い、両方の標準偏差によりそれぞれ独立して計数率演算処理が実施され、境界点で出力する計数率が自動的に切り換わるようになっている（特許文献１参照）。また、特許文献２では、低い計数率では、積算時間一定の特性を持ち、高い計数率では、積算カウント値一定の特性を持つ放射線モニタが開示されている。 Based on this method, the conventional radiation monitor divides the measurement range into two, the low count rate region and the high count rate region, and the low count rate region sets the standard deviation to be small and performs measurement with priority on measurement accuracy. In the high count rate area, the standard deviation is set to a large value and priority is given to responsiveness. The count rate calculation process is performed independently for both standard deviations, and the count rate output at the boundary point is automatically set. Switching is made (see Patent Document 1). Patent Document 2 discloses a radiation monitor having a characteristic of constant integration time at a low count rate and a characteristic of constant integration count value at a high count rate.

特開昭６１−１２８１８４号公報JP-A-61-128184 特開平１１−３２６５２３号公報JP-A-11-326523

従来の放射線モニタは、以上のように構成されているので、標準偏差が異なる計数率において、データベースが異なることに起因した段差が発生するという問題があり、指示トレンドの段差は、指示変化に注目して監視する際に連続して変化するはずのトレンドの一部に急変として発現するため、機器故障等の誤った判断を行うリスクがあった。
この発明は前記のような課題を解決するためになされたものであり、標準偏差又は測定時間切換時の指示の不連続な変化を防止でき、応答と視認性を両立させた高信頼な放射線モニタを得ることを目的とする。 Since the conventional radiation monitor is configured as described above, there is a problem that a level difference caused by a different database occurs at a counting rate with a different standard deviation. Therefore, since there is a sudden change in a part of the trend that should change continuously when monitoring, there is a risk of erroneous determination such as equipment failure.
The present invention has been made to solve the above-described problems, and can prevent a discontinuous change in the standard deviation or the indication at the time of switching the measurement time, and can provide a highly reliable radiation monitor that achieves both response and visibility. The purpose is to obtain.

また、この発明に係わる放射線モニタは、放射線を検出してアナログ信号パルスを出力する放射線検出器と、前記アナログ信号パルスが入力されその波高レベルが許容範囲内にある場合にデジタルパルスを出力し、許容範囲を逸脱する場合にノイズとして除去する波高弁別器と、前記デジタルパルスが入力され定周期で計数して計数値を出力する計数手段と、前記計数値を先入れ先出し方式で所定のデータ数について格納すると共に、計数率演算過程の最新データを格納する記憶手段と、前記計数値に基づき定周期で計数率を演算し、演算した計数率又はその計数率を変換した工学値について警報判定を行って計数率又は工学値及び警報判定結果を出力する演算手段と、前記計数率又は工学値及び警報判定結果を表示する表示手段を備え、前記演算手段は、設定された計数率領域毎に計数率を演算し、その設定された計数率領域境界で、測定時間に基づく計数率から標準偏差に基づく計数率に切り換える際に、その演算周期における切換前の計数率を引き継いで切換を行い、標準偏差に基づく計数率から測定時間に基づく計数率に切り換える際に、その計数率の差が許容範囲内の場合に切換を行うようにしたものである。 In addition, the radiation monitor according to the present invention is a radiation detector that detects radiation and outputs an analog signal pulse, and outputs a digital pulse when the analog signal pulse is input and the wave height level is within an allowable range, A wave height discriminator that removes noise as a noise when it deviates from the allowable range, a counting unit that receives the digital pulse, counts at a constant cycle and outputs a count value, and stores the count value for a predetermined number of data in a first-in first-out method In addition, the storage means for storing the latest data of the count rate calculation process, the count rate is calculated at regular intervals based on the count value , and the alarm determination is performed on the calculated count rate or the engineering value obtained by converting the count rate comprising calculating means for outputting the count rate or engineering values and alarm determination result, the display means for displaying the count rate or the engineering value and alarm determination result, before Calculating means calculates the count rate in the count rate for each area set in the set count rate region boundary, when switching from the counting rate based on the measured time count rate based on the standard deviation, in that calculation period When switching from the count rate based on the standard deviation to the count rate based on the measurement time, switching is performed when the difference between the count rates is within the allowable range. is there.

この発明の放射線モニタによれば、切換点で計数率の段差を発生させることなく切換を行うことができ、応答と視認性を両立させた高信頼な放射線モニタを得ることができる。 According to the radiation monitor of the present invention, switching can be performed without causing a difference in counting rate at the switching point, and a highly reliable radiation monitor that achieves both response and visibility can be obtained.

この発明の実施の形態１における放射線モニタを示すブロック図である。It is a block diagram which shows the radiation monitor in Embodiment 1 of this invention. 実施の形態１の放射線モニタの演算器における演算処理を示すフロー図である。FIG. 3 is a flowchart showing a calculation process in a calculator of the radiation monitor according to the first embodiment. 実施の形態１における計数率と応答時間特性を示す図である。It is a figure which shows the count rate in Embodiment 1, and a response time characteristic. 実施の形態１におけるステップ入力に対する指示応答を示す図である。6 is a diagram showing an instruction response to a step input in the first embodiment. FIG. 実施の形態２における放射線モニタを示すブロック図である。6 is a block diagram showing a radiation monitor in the second embodiment. FIG. 実施の形態２の放射線モニタの演算器における演算処理を示すフロー図である。FIG. 10 is a flowchart showing a calculation process in a calculator of the radiation monitor according to the second embodiment. 実施の形態３の放射線モニタの演算器における演算処理を示すフロー図である。FIG. 10 is a flowchart showing calculation processing in the calculator of the radiation monitor according to the third embodiment. 実施の形態３における計数率と応答時間特性を示す図である。It is a figure which shows the count rate in Embodiment 3, and a response time characteristic. 実施の形態３におけるステップ入力に対する指示応答を示す図である。FIG. 10 is a diagram showing an instruction response to a step input in the third embodiment. 実施の形態３における標準偏差の一定計数率における度数と計数率の例を示す図である。It is a figure which shows the example in the frequency | count in the fixed count rate of the standard deviation in Embodiment 3, and a count rate. 実施の形態３における測定時間ΣΔＴの一定計数率における度数と計数率の例を示す図である。It is a figure which shows the example in the count in the fixed count rate of measurement time (SIGMA) (DELTA) T in Embodiment 3, and a count rate.

実施の形態１．
この発明の実施の形態１を図に基づいて説明する。図１において、放射線検出器１は、放射線を検出してアナログ信号パルスを出力する。波高弁別器２には、放射線検出器１から出力されたアナログ信号パルスが入力され、その電圧レベル（つまり、波高レベル）が、設定されたレベルの範囲内（つまり許容範囲内）である場合には、入力されたアナログ信号パルスは信号パルスと見なしデジタルパルスを出力するが、設定された許容範囲を逸脱する場合には、ノイズとみなし、デジタルパルスを出力しない。 Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings. In FIG. 1, a radiation detector 1 detects radiation and outputs an analog signal pulse. When the analog signal pulse output from the radiation detector 1 is input to the wave height discriminator 2 and the voltage level (that is, the wave height level) is within a set level range (that is, within an allowable range). The input analog signal pulse is regarded as a signal pulse and a digital pulse is output. However, if it deviates from the set allowable range, it is regarded as noise and the digital pulse is not output.

カウンタ３（計数手段）には、波高弁別器２から出力されたデジタルパルスが入力され、定周期で計数して計数値ΔＮを出力する。演算器４には、カウンタ３から出力された今回演算周期の計数値ΔＮ(今回)が入力され、メモリー５（記憶手段）に格納する。演算器４（演算手段）は、メモリー５に格納されている計数値に基づき定周期で計数率を演算し、計数率を工学値に変換する共にその工学値の警報判定を行って、工学値及び警報判定結果を出力する。表示器６（表示手段）は、その計数率（工学値）及び警報判定結果を表示すると共に、画面から設定値入力及び操作を行うことができる。工学値は用途により計数率そのものである場合もあり、工学値を放射線量に変換する定数を乗じたものである場合もある。以下の説明では、工学値＝計数率の場合で説明する。 The digital pulse output from the wave height discriminator 2 is input to the counter 3 (counting means), and the counter 3 (counting means) counts at a constant period and outputs a count value ΔN. The computing unit 4 receives the count value ΔN (current) output from the counter 3 and stores it in the memory 5 (storage means). The arithmetic unit 4 (calculation means) calculates a count rate at a constant cycle based on the count value stored in the memory 5, converts the count rate into an engineering value, performs an alarm judgment on the engineering value, and calculates an engineering value. And the alarm judgment result is output. The display 6 (display means) can display the count rate (engineering value) and the alarm determination result, and can perform setting value input and operation from the screen. The engineering value may be the count rate itself depending on the application, or it may be multiplied by a constant that converts the engineering value into a radiation dose. In the following description, the case of engineering value = count rate will be described.

次に、演算器４における標準偏差一定の計数率ｍを求める演算について説明する。前回演算周期の計数率をｍ(前回)、前回演算周期の加減差積算値をＭ(前回)、演算周期毎のカウンタの計数時間をΔＴ、今回演算周期の加減差積算値をＭ(今回)、今回演算周期の計数率をｍ(今回)とすると、Ｍ(今回)及びｍ(今回)はそれぞれ（１）式、（２）式により求めることができる。
Ｍ(今回)＝Ｍ(前回)＋２^α×{ΔＮ(今回)−ｍ(前回)×ΔＴ}・・・（１）
ｍ(今回)＝exp{γＭ(今回)}・・・（２） Next, the calculation for obtaining the count rate m with a constant standard deviation in the calculator 4 will be described. The count rate of the previous calculation cycle is m (previous), the addition / subtraction integrated value of the previous calculation cycle is M (previous), the counter counting time for each calculation cycle is ΔT, and the addition / subtraction integration value of the current calculation cycle is M (current) Assuming that the count rate of the current calculation cycle is m (current), M (current) and m (current) can be obtained by equations (1) and (2), respectively.
M (current) = M (previous) +2 ^α × {ΔN (current) −m (previous) × ΔT} (1)
m (this time) = exp {γM (this time)} (2)

（２）式で求められた計数率ｍは、次式（３）に示すように標準偏差σ＝一定で制御される。
σ＝１／（２ｍτ)^1/2＝一定・・・（３）
また、時定数τは、次式（４）のように計数率ｍに反比例し、標準偏差の２乗に反比例し、γに反比例する。γは、次式（５）のように標準偏差の２乗に比例し、例えば、計数の重み付けに係わる定数αを用いて２^αで重み付けして計数することにより、（２）式から求められる計数率ｍは、波高弁別器２の出力パルスの繰り返し周波数の変化に時定数τの一次遅れで追従して応答する。
τ＝１／（２ｍσ²)＝１／（ｍγ) ・・・（４）
γ＝２σ²＝２^α×２⁻¹¹×ln２＝定数・・・（５） The count rate m obtained by the equation (2) is controlled with the standard deviation σ = constant as shown in the following equation (3).
σ = 1 / (2mτ) ^1/2 = constant (3)
Further, the time constant τ is inversely proportional to the count rate m, inversely proportional to the square of the standard deviation, and inversely proportional to γ as in the following equation (4). γ is proportional to the square of the standard deviation as shown in the following equation (5), and is obtained from the equation (2) by, for example, counting by weighting with 2 ^α using a constant α relating to counting weighting. The count rate m responds by following the change in the repetition frequency of the output pulse of the wave height discriminator 2 with a first-order lag of the time constant τ.
τ = 1 / (2mσ ² ) = 1 / (mγ) (4)
γ = 2σ ² = 2 ^α × 2 ⁻¹¹ × ln2 = constant (5)

（５）式において、２^αで計数の重み付けをすることにより、α＝０の重み付け２^０＝１を基準とすると、計数α＝２の重み付け２^２＝４でτは１／４、α＝４の重み付け２^４＝１６でτは１／１６、α＝６の重み付け２^６＝６４でτは１／６４と、計数の重み付けを大きくすることにより応答は順次速くなる。 (5) In the equation, by the weighting count in 2 ^alpha, when the reference weighted ² 0 = 1 alpha = 0, the counting alpha = 2 weighting ² 2 = 4 in the tau 1/4, alpha = 4 weighting 2 ⁴ = 16, τ is 1/16, α = 6 weighting 2 ⁶ = 64, and τ is 1/64. By increasing the weighting of the count, the response becomes faster.

次に、図２のフロー図で演算器４における演算処理手順について説明する。Ｓ１において、ｍ_Ｂは把握されている平均的なバックグラウンド計数率であり、ｋ_１は標準偏差切換点(σ₁→σ₂)に対応する計数率とｍ_Ｂの比であり、ｋ_２は標準偏差切換点(σ₂→σ₁) に
対応する計数率とｍ_Ｂの比であり、α₁及びα₂は計数の重み付けに係わる定数である。また、Ｓ１２に示すようにｋ_１＜ｋ_２の関係にあり、Ｓ６に示すようにα₁＜α₂の関係にある。ｋ_１ｍ_Ｂ、ｋ_２ｍ_Ｂ、α₁、α₂、はそれぞれ設定値としてメモリーに格納している。Ｓ１でΔＮ(今回)、ｍ(前回)、Ｍ(前回)、ｋ_１ｍ_Ｂ、ｋ_２ｍ_Ｂを入力し、Ｓ２で（１）式によりＭ(今回)を求め、Ｓ３で（２）式によりｍ(今回)を求める。 Next, the calculation processing procedure in the calculator 4 will be described with reference to the flowchart of FIG. In S1, m _B is a known average background count rate, k ₁ is the ratio of the count rate corresponding to the standard deviation switching point (σ ₁ → σ ₂ ) and m _B , and k ₂ is The ratio between the count rate corresponding to the standard deviation switching point (σ ₂ → σ ₁ ) and m _B , and α ₁ and α ₂ are constants related to the weighting of the count. Further, the relationship is k ₁ <k ₂ as shown in S12, and the relationship is α ₁ <α ₂ as shown in S6. k ₁ m _B , k ₂ m _B , α ₁ , and α ₂ are respectively stored in the memory as set values. At S1, ΔN (current), m (previous), M (previous), k ₁ m _B , k ₂ m _B are input, M (current) is obtained by S1 in S2, and (2) in S3 To find m (this time).

Ｓ４でｍ(今回)≦ｋ_１ｍ_Ｂのフラグ有りかの判定を行い、ＮＯならばＳ５でｍ(今回)≦ｋ_１ｍ_Ｂかの判定を行い、ＹＥＳならばＳ６でｍ(今回)≦ｋ_１ｍ_Ｂのフラグを立て、α₁
をα₂に切り換える。Ｓ７でｍ(今回)≦低警報設定点かの判定を行い、ＹＥＳならＳ８で
低警報を出力し、Ｓ９でｍ(今回)≧高警報設定点かの判定を行い、ＹＥＳならＳ１０で高警報を出力し、Ｓ１１でｍ(今回)を出力し、今回演算周期を終了してＳ１に戻る。Ｓ７でＮＯならばＳ９に進み、Ｓ９でＮＯならばＳ１１に進む。Ｓ４でＹＥＳならばＳ１２でｍ(今回)≧ｋ_２ｍ_Ｂかの判定を行い、ＹＥＳならＳ１３でｍ(今回)≦ｋ_１ｍ_Ｂのフラグをリセットし、α₂をα₁に切り換えてＳ７に進む。Ｓ１２でＮＯならばＳ７に進む。 In S4, it is determined whether there is a flag of m (current) ≦ k ₁ m _B. If NO, it is determined in S5 whether m (current) ≦ k ₁ m _B , and if YES, m (current) ≦ Raise the k ₁ m _B flag and α ₁
The switch to the α _2. In S7, m (current) ≤ low alarm set point is determined. If YES, a low alarm is output in S8. In S9, m (current) ≥ high alarm set point is determined. If YES, high alarm is determined in S10. , M (current) is output in S11, the current calculation cycle is terminated, and the process returns to S1. If NO in S7, the process proceeds to S9, and if NO in S9, the process proceeds to S11. S4 performed m (time) ≧ _k 2 _{m B} Kano determination is YES if The S12, m (this time) in S13 if YES ≦ _k 1 resets the flag of _{m B,} switching the alpha ₂ to alpha ₁ S7 Proceed to If NO in S12, the process proceeds to S7.

バックグラウンド計数率を含みそのゆらぎの下限以上から測定レンジ上限までは、測定
精度からの要求で決まる標準偏差σ₁になるように計数率が演算され、機器故障で計数率
がバックグラウンド計数率から低下し、そのゆらぎの下限を逸脱して低下した場合に、できるだけ早く低警報を発信させて欠測を最短にする。 From the lower limit of the fluctuation including the background count rate to the upper limit of the measurement range, the count rate is calculated so that the standard deviation σ ₁ determined by the request from the measurement accuracy is reached. If it falls and deviates from the lower limit of the fluctuation, a low alarm is issued as soon as possible to minimize missing data.

図３おいて、低警報設定値Ｌに対してｃの標準偏差切換点(σ₁→σ₂)を、例えば１／２×（ｍ_Ｂ＋Ｌ)なる計数率に設定すると、σ₁の今回計数率ｍ(今回)がその切換点計数率以下になると、標準偏差がσ₁からσ₁＜σ₂なるσ₂に切り換えられ、（５）式の計数の重
み付けに係わる定数αがσ₁に対応するα₁からσ₂に対応するα₂に切り換えられ、（４）式により時定数τが短くなって結果として図４のようにｇからｈに応答が速くなり、低警報発信が速まる。このとき、図３においてゆらぎの下限をｅの平均的なバックグラウンド計数率ｍ_Ｂから、例えば標準偏差σ₁の４倍の幅を想定したｍ_Ｂ(1−4σ₁)とし、誤切換の確率に配慮してｃの切換点を設定する。切換後の次の演算周期では、（１）式でＭ(今回)を求める際に、切換前のｍ(前回)に対応するＭ(前回)を引き継ぎ、切り換えられた計数の重み付けに係わる定数α₂で（２）式によりｍ(今回)を求める。 In FIG. 3, if the standard deviation switching point (σ ₁ → σ ₂ ) of c with respect to the low alarm set value L is set to a count rate of, for example, 1/2 × (m _B + L), the current count of σ ₁ When the rate m (current) falls below the switching point counting rate is switched from the standard deviation sigma ₁ to sigma ₁ <sigma ₂ becomes sigma _2, (5) corresponds to ₁ constant α is sigma relating to weighting of the counting of formula The α ₁ corresponding to σ ₂ is switched to α ₂ corresponding to σ _2, and the time constant τ is shortened by the equation (4). As a result, the response from g to h is accelerated as shown in FIG. In this case, in FIG. 3, the lower limit of fluctuation is set to m _B (1−4σ ₁ ) assuming a width four times the standard deviation σ ₁ from the average background count rate m _B of e, and the probability of erroneous switching. In consideration of the above, the switching point of c is set. In the next calculation cycle after switching, when calculating M (current) in equation (1), M (previous) corresponding to m (previous) before switching is taken over, and a constant α relating to the weighting of the switched count. _{In step 2} , m (current) is obtained from equation (2).

バックグラウンド計数率ｍ_Ｂが復帰する場合は、ｃの標準偏差切換点(σ₁→σ₂)とｍ_Ｂの間の、例えば１／４×(３ｍ_Ｂ＋Ｌ)なる計数率をｄの標準偏差切換点(σ₂→σ₁)とし
てヒステリシスを設ける。 When the background count rate m _B returns, a count rate of, for example, 1/4 × (3 m _B + L) between the standard deviation switching point (σ ₁ → σ ₂ ) of c and m _B is set to the standard of d. A hysteresis is provided as a deviation switching point (σ ₂ → σ ₁ ).

以上のように、切換点において計数率を引き継いで標準偏差の切換を行うようにしたので、切換点で計数率の段差を発生させることなく切換を行うことができ、入力の変化に対する所望の出力応答が容易に得られ、応答と視認性を両立させた高信頼な放射線モニタを得ることができる。また、標準偏差切換点(σ₁→σ₂)と標準偏差切換点(σ₂→σ₁) とに
ヒステリシスを設けたので、標準偏差切換点におけるハンチングを防止して安定な切換を行うことができる。 As described above, since the standard deviation is switched by taking over the count rate at the switching point, the switching can be performed without causing a difference in the counting rate at the switching point, and a desired output with respect to a change in input can be achieved. A response can be easily obtained, and a highly reliable radiation monitor having both response and visibility can be obtained. Since hysteresis is provided at the standard deviation switching point (σ ₁ → σ ₂ ) and the standard deviation switching point (σ ₂ → σ ₁ ), hunting at the standard deviation switching point can be prevented and stable switching can be performed. it can.

実施の形態２．
実施の形態１では、波高弁別器２から出力されたデジタルパルスをカウンタ３が定周期で計数して計数値ΔＮを出力し、演算器４は、カウンタ３から出力された今回演算周期の計数値ΔＮ(今回)を入力してメモリー５に格納し、その計数値に基づき定周期で計数率を演算したが、実施の形態２は、図５においてカウンタ３の代わりにアップダウンカウンタ７と、積算制御回路８と、パルス発生器９（周波数合成回路）を備え、アップダウンカウンタ７は波高弁別器２から出力されたデジタルパルスが加算入力端子７１に入力され、パルス発生器９から出力されたデジタルパルスが減算入力端子７２に入力され、その結果の加減差積算値を出力する。実施の形態２では、この加減差積算値を、実施の形態１のＭ(
今回)の代わりとして用いる。 Embodiment 2. FIG.
In the first embodiment, the counter 3 counts the digital pulses output from the pulse height discriminator 2 at a constant cycle and outputs a count value ΔN, and the calculator 4 outputs the count value of the current calculation cycle output from the counter 3. ΔN (current) is input and stored in the memory 5, and the count rate is calculated at a constant cycle based on the count value. In the second embodiment, the up / down counter 7 is replaced with the counter 3 in FIG. The up / down counter 7 includes a control circuit 8 and a pulse generator 9 (frequency synthesizer circuit). The up / down counter 7 receives the digital pulse output from the pulse height discriminator 2 as input to the addition input terminal 71 and outputs the digital pulse output from the pulse generator 9. A pulse is input to the subtraction input terminal 72, and the resultant addition / subtraction integrated value is output. In the second embodiment, this addition / subtraction integrated value is set to M (1) in the first embodiment.
Use as an alternative to this time.

積算制御回路８は、アップダウンカウンタ７の加算入力及び減算入力を標準偏差に基づき前記（５）式の２^αで重み付けして計数するようにアップダウンカウンタ７を制御する。パルス発生器９はアップダウンカウンタ７から出力された加減差積算値が入力され、加算入力の繰り返し周波数に対して時定数の一時遅れで応答する繰り返し周波数に変換してアップダウンカウンタ７の減算入力端子７２に減算入力する。演算器４は、アップダウンカウンタ７から出力された加減差積算値が入力され、加減差積算値及び計数率演算過程の最新データをメモリー５に格納し、その加減差積算値に基づき前記（２）式により計数率を求める。演算器４は、加減差積算値に基づき計数率を求める標準偏差一定計数率演算を実行する。 Integration control circuit 8 controls the up-down counter 7 to count the addition input and subtraction input of the up-down counter 7 by weighting with the basis of the standard deviation (5) of 2 ^alpha. The pulse generator 9 receives the accumulated difference value output from the up / down counter 7 and converts it into a repetition frequency that responds with a temporary delay of a time constant with respect to the repetition frequency of the addition input, and the subtraction input of the up / down counter 7 Subtract input to terminal 72. The arithmetic unit 4 receives the addition / subtraction integration value output from the up / down counter 7, stores the addition / subtraction integration value and the latest data of the count rate calculation process in the memory 5, and based on the addition / subtraction integration value (2 ) Calculate the counting rate using the formula. The computing unit 4 performs a standard deviation constant count rate calculation for obtaining a count rate based on the accumulated difference value.

次に、図６のフロー図で演算器４における演算処理手順について説明する。なお、ｍ_Ｂ、ｋ_１、ｋ_２、α₁、α₂は図２と同じなので説明を省略する。Ｓ２１でＭ(今回)（アップダウンカウンタ７の出力）、ｋ_１ｍ_Ｂ、ｋ_２ｍ_Ｂを入力し、Ｓ２２で（２）式によりｍ(
今回)を求め、Ｓ２３でｍ(今回)≦ｋ_１ｍ_Ｂのフラグ有りかの判定を行い、ＮＯならばＳ
２４でｍ(今回)≦ｋ_１ｍ_Ｂかの判定を行い、ＹＥＳならばＳ２５でｍ(今回)≦ｋ_１ｍ_Ｂのフラグを立て、α₁をα₂に切り換える。Ｓ２６でｍ(今回)≦低警報設定点かの判定を行い、ＹＥＳならＳ２７で低警報を出力し、Ｓ２８でｍ(今回)≧高警報設定点かの判定を行い、ＹＥＳならＳ２９で高警報を出力し、Ｓ３０でｍ(今回)を出力して今回演算周期を終了してＳ２１に戻る。Ｓ２６でＮＯならばＳ２８に進み、Ｓ２８でＮＯならばＳ３０に進む。Ｓ２３でＹＥＳならばＳ３１でｍ(今回)≧ｋ_２ｍ_Ｂかの判定を行い、ＹＥＳならＳ３２でｍ(今回)≦ｋ_１ｍ_Ｂのフラグをリセットし、α₂をα₁に切り換えてＳ２６に進む。Ｓ３１でＮＯならばＳ２６に進む。 Next, the calculation processing procedure in the calculator 4 will be described with reference to the flowchart of FIG. Note that m _B , k ₁ , k ₂ , α ₁ , and α ₂ are the same as those in FIG. In S21, M (current) (output of up / down counter 7), k ₁ m _B , and k ₂ m _B are input, and in S22, m (
This time) is obtained, and it is determined in S23 whether m (current) ≦ k ₁ m _B flag is present.
24, it is determined whether m (current) ≦ k ₁ m _B. If YES, a flag m (current) ≦ k ₁ m _B is set in S25, and α ₁ is switched to α ₂ . In S26, it is determined whether m (current) ≤ low alarm set point. If YES, a low alarm is output in S27. In S28, m (current) ≥ high alarm set point is determined. If YES, high alarm is determined in S29. , M (current) is output in S30, the current calculation cycle is terminated, and the process returns to S21. If NO in S26, the process proceeds to S28, and if NO in S28, the process proceeds to S30. S23 performs m (time) ≧ _k 2 _{m B} Kano determination is YES if S31 in, m (this time) in S32 if YES resets the flag of ≦ _k 1 _{m B,} switching the alpha ₂ to alpha ₁ S26 Proceed to If NO in S31, the process proceeds to S26.

以上のように、切換点において計数率を引き継いで積算制御回路８によりアップダウンカウンタ７の計数の重み付け制御を変えて標準偏差の切換を行うことにより、実施の形態１と同様に、切換点で計数率の段差を発生させることなく切換を行うことができ、入力の変化に対する所望の出力応答が容易に得られ、応答と視認性を両立させた高信頼な放射線モニタを得ることができると共に、ハードウェアで加減差積算値が得られるようにしたので演算時間を短縮して高計数率まで良好な直線性が得られる。 As described above, by taking over the count rate at the switching point and changing the weighting control of the count of the up / down counter 7 by the integration control circuit 8 and switching the standard deviation, the switching point is changed as in the first embodiment. Switching can be performed without causing a difference in counting rate, a desired output response to an input change can be easily obtained, and a highly reliable radiation monitor that balances response and visibility can be obtained. Since the addition / subtraction integrated value can be obtained by hardware, the calculation time can be shortened and good linearity can be obtained up to a high count rate.

実施の形態３．
実施の形態１では、演算器４が、カウンタ３から出力された今回演算周期の計数値ΔＮ(今回)を入力してメモリー５に格納し、定周期でΔＮ(今回)に基づき標準偏差一定で計数率ｍ(今回)を演算する標準偏差一定計数率演算フローを備え、標準偏差を切り換えて所望の計数率応答を得るようにした。 Embodiment 3 FIG.
In the first embodiment, the arithmetic unit 4 inputs the count value ΔN (current) of the current calculation cycle output from the counter 3 and stores it in the memory 5, and the standard deviation is constant based on ΔN (current) at regular intervals. A standard deviation constant count rate calculation flow for calculating the count rate m (current) is provided, and a desired count rate response is obtained by switching the standard deviation.

これに代えて、実施の形態３において演算器４は、カウンタ３から出力された計数値ΔＮ(今回)を入力してメモリー５に先入れ先出し方式で格納し、定周期でΔＮ(今回)に基づき標準偏差一定で計数率ｍ(今回)を演算する標準偏差一定計数率演算フローと、今回演算周期から設定された演算周期数まで過去に遡って計数値を積算して積算計数値ΣΔＮを求め、対応する各演算周期の計数時間ΔＴの積算時間ΣΔＴで割り算して時間一定で計数率ｎ(今回)を求める測定時間一定演算フローの両方を備え、測定レンジを、例えば、測定レンジ下限と低警報及びバックグラウンドレベルを含む低計数率領域と、高警報及び測定レンジ上限を含む高計数率領域の２つに分け、低計数率領域を時間一定計数率演算でカバーし、高計数率領域を標準偏差一定計数率演算でカバーし、低計数率領域では次式（６）により今回計数率ｎ(今回)を求め、高計数率領域では前記（２）式により今回計数率ｍ(今
回)を求める。 Instead, in the third embodiment, the arithmetic unit 4 inputs the count value ΔN (current) output from the counter 3 and stores it in the memory 5 in a first-in first-out manner, and based on ΔN (current) at regular intervals. Standard deviation constant count rate calculation flow that calculates count rate m (current) with constant deviation, and count value is integrated retroactively from the current calculation cycle to the set number of calculation cycles to obtain integrated count value ΣΔN It is equipped with both a constant measurement time calculation flow to obtain a count rate n (current) by dividing by the integration time ΣΔT of the counting time ΔT of each calculation cycle, and the measurement range, for example, the measurement range lower limit and the low alarm, It is divided into a low count rate area including the background level and a high count rate area including the high alarm and the upper limit of the measurement range. The low count rate area is covered by a constant time count rate calculation, and the high count rate area is standard deviation. Constant counting rate Covered by calculation, the current count rate n (current) is obtained by the following equation (6) in the low count rate region, and the current count rate m (current) is obtained by the equation (2) in the high count rate region.

ｎ(今回)＝ΣΔＮ(今回) ／ΣΔＴ・・・（６） n (current) = ΣΔN (current) / ΣΔT (6)

計数率がバックグラウンドレベルから上昇して第１の切換点以上になったら、ｎ(今回)を引き継いでｍ(今回)が出力され、次の演算周期に備えて、次式（７）によりＭ(今回)が求められ、演算が切換移行される。
Ｍ(今回)＝ln{ m(今回)}／γ・・・（７）
計数率が、高計数率領域から下降して第２の切換点未満になったら、その演算周期における切換前の計数率に対して切換後の計数率が許容範囲内の場合に出力の切換を行う。 When the count rate rises from the background level and exceeds the first switching point, n (current) is taken over and m (current) is output. In preparation for the next calculation cycle, M is calculated according to the following equation (7). (This time) is obtained, and the calculation is switched.
M (this time) = ln {m (this time)} / γ (7)
When the count rate falls from the high count rate region and falls below the second switching point, the output is switched when the count rate after switching is within the allowable range with respect to the count rate before switching in the calculation cycle. Do.

次に、図７のフロー図で演算器４における演算処理手順について説明する。ｎ_Ｂは把握されている平均的なバックグラウンド計数率であり、ｋ_３は時間・標準偏差切換点(ΣΔ
Ｔ→σ)に対応する計数率とｎ_Ｂの比であり、ｋ_４は時間・標準偏差切換点(σ→ΣΔＴ)
に対応する計数率とｎ_Ｂの比であり、σは標準偏差であり、ｋ_５は標準偏差の係数である。また、Ｓ５３に示すようにｋ_３とｋ_４はｋ_３＞ｋ_４の関係にある。ｋ_３ｎ_Ｂ、ｋ_４ｎ_Ｂ、ｋ_５σはそれぞれ設定値としてメモリーに格納されている。 Next, the calculation processing procedure in the calculator 4 will be described with reference to the flowchart of FIG. n _B is the average background count rate that is known, and k ₃ is the time / standard deviation switching point (ΣΔ
The ratio of the count rate corresponding to T → σ) and n _B , and k ₄ is the time / standard deviation switching point (σ → ΣΔT)
Is the ratio of the count rate corresponding to and n _B , σ is the standard deviation, and k ₅ is the coefficient of the standard deviation. Also, _{k 3} and _{k 4} as shown in and S53 are in a relationship of _{_k} 3> _k _4. k ₃ n _B , k ₄ n _B , and k ₅ σ are respectively stored in the memory as set values.

Ｓ４１で時系列的に配列されたΔＮ、ｋ_３ｎ_Ｂを入力し、Ｓ４２で（６）式によりｎ(
今回)を求め、Ｓ４３でｎ(今回)≧ｋ_３ｎ_Ｂかの判定を行い、ＮＯならばＳ４４でｎ(今回)≦低警報設定点かの判定を行い、ＹＥＳならばＳ４５で低警報を出力し、Ｓ４６でｎ(今回)≧高警報設定点かの判定を行い、ＹＥＳならばＳ４７で高警報を出力してＳ４８に進
み、Ｓ４４でＮＯの場合はＳ４６に進み、Ｓ４６でＮＯの場合はＳ４８に進み、Ｓ４８でｎ(今回)を出力して当該演算周期を終了してＳ４１に戻る。 In step S41, ΔN and k ₃ n _B arranged in time series are input, and in step S42, n (
This time) is determined. In step S43, it is determined whether n (current) ≧ k ₃ n _B. If NO, it is determined in step S44 whether n (current) ≦ low alarm set point. If YES, a low alarm is determined in S45. In S46, it is determined whether n (current) ≧ high alarm set point. If YES, a high alarm is output in S47 and the process proceeds to S48. If NO in S44, the process proceeds to S46, and if S46 is NO. Advances to S48, outputs n (current) in S48, ends the calculation cycle, and returns to S41.

Ｓ４３でＹＥＳの場合はＳ４９でｎ＝ｍとし、（７）式でＭ(今回)を求めてＳ５７に進み、Ｓ５７でｍ(今回)≧高警報設定点かの判定を行い、ＹＥＳならばＳ５８で高警報を出力し、Ｓ５７でＮＯの場合はＳ５９に進み、Ｓ５９でｍ(今回)を出力して当該演算周期を終了し、次の演算周期はＳ５０から開始する。Ｓ５０でΔＮ、ｍ(前回)、Ｍ(前回)、ｋ_４ｎ_Ｂ、ｋ_５σを入力し、Ｓ５１で（１）式によりＭ(今回)を求め、Ｓ５２で（２）式によりｍ(今回)を求め、Ｓ５３でｍ(今回)≦ｋ_４ｎ_Ｂの判定を行い、ＹＥＳの場合はＳ５４で時系列的に配列されたΔＮを入力し、Ｓ５５で（６）式によりｎ(今回)を求め、Ｓ５６でｍ(今回)−ｋ_５σ≦ｎ(今回)≦ｍ(今回)＋ｋ_５σの判定を行い、ＹＥＳの場合はＳ４４に進み、ＮＯの場合はＳ５７に進む。 If YES in S43, n = m is set in S49, M (current) is obtained by equation (7), and the process proceeds to S57. In S57, it is determined whether m (current) ≧ high alarm set point. If NO in S57, the process proceeds to S59. In S59, m (current) is output to end the calculation cycle, and the next calculation cycle starts from S50. At S50, ΔN, m (previous), M (previous), k ₄ n _B , and k ₅ σ are input, M (current) is obtained by equation (1) in S51, and m (current) is calculated by equation (2) in S52. ), M (current) ≦ k ₄ n _B is determined in S53, and if YES, ΔN arranged in time series in S54 is input, and in S55, n (current) is calculated using equation (6). calculated, m (this time) in S56 -k _{5 σ} ≦ n (current) ≦ m (current) makes a determination of + _{k 5} sigma, in the case of YES, the process advances to S44, and if NO, it proceeds to a S57.

図８は、計数率と応答時間特性を示すもので、測定レンジ下限〜バックグラウンドの通常のゆらぎ上限付近の低計数率領域ではｉのΣΔＴ＝一定で計数率が求められ、低計数率領域以上〜測定レンジ上限の高警報設定点を含む高計数率領域ではｊのσ＝一定で計数率が求められ、２つの領域の境界のｋ_３ｎ_Ｂにｐの時間・標準偏差切換点(ΣΔＴ→σ)が設定され、計数率が上昇してｋ_３ｎ_Ｂ以上になると、計数率を求める演算がｉのΣΔＴ＝一定からｊのσ＝一定に切り換わる。上昇した計数率がバックグラウンドに向かって復帰する際に、ｋ_４ｎ_Ｂ以下になると、ｋ_３＞ｋ_４なるｋ_４ｎ_Ｂに、ｓの時間・標準偏差切換点(σ→ΣΔＴ)が設定され、ｓにおいて、ｊのσ＝一定からｉのΣΔＴ＝一定に切り換わり、上昇と下降の切換点にヒステリシスを設けている。 FIG. 8 shows the count rate and response time characteristics. In the low count rate region near the upper limit of the measurement range to the normal fluctuation upper limit, the count rate is obtained with ΣΔT = constant of i. the high count rate region including the high alarm set point - measuring range limit counting rate is obtained by j of sigma = constant, two times p to k ₃ n _B of the boundary of the area, standard deviation switching point (ΣΔT → sigma) is set, the count rate becomes more than k ₃ n _B rises, calculation for obtaining the count rate is switched from i of ShigumaderutaT = constant j of sigma = constant. When the increased count rate returns to the background, if k ₄ n _B or less, the time / standard deviation switching point (σ → ΣΔT) of s is set to k ₄ n _B where k ₃ > k ₄ In s, j is switched from σ = constant to ΣΔT = constant, and hysteresis is provided at the switching point between ascending and descending.

図９はステップ入力に対する計数率の応答を示すものので、ｕ及びｙのΣΔＴ＝一定では直線的に応答し、ｖ及びｗのσ＝一定では指数関数で応答する。 FIG. 9 shows the response of the count rate to the step input. When u and y are ΣΔT = constant, the response is linear, and when v and w are constant, the response is an exponential function.

なお、図１０は、標準偏差の一定計数率における度数と計数率の例を示す図である。図１１は測定時間ΣΔＴの一定計数率における度数と計数率の例を示す図である。これらにより、図１１はガウス分布であり、図１０はガウス分布が高計数率側に歪むことがわかる。 In addition, FIG. 10 is a figure which shows the example of the frequency and count rate in the fixed count rate of a standard deviation. FIG. 11 is a diagram illustrating an example of the frequency and the count rate at a constant count rate of the measurement time ΣΔT. From these, FIG. 11 shows a Gaussian distribution, and FIG. 10 shows that the Gaussian distribution is distorted to the high count rate side.

以上のように、測定レンジを低計数率領域と高計数率領域の２つに分け、例えば、低計数率領域を時間一定計数率演算でカバーし、高計数率領域を標準偏差一定計数率演算でカバーし、上昇時は計数率を引き継ぐようにして演算の切換を行い、降下時は両方の演算の計数率が許容範囲内の場合に切換を行うようにしたので、切換点で計数率の段差を発生させることなく切換を行うことができ、入力の変化に対する所望の出力応答が容易に得られ、応答と視認性を両立させた高信頼な放射線モニタを得ることができる。 As described above, the measurement range is divided into two areas, the low count rate area and the high count rate area. For example, the low count rate area is covered by the constant count rate calculation, and the high count rate area is calculated by the standard deviation constant count rate calculation. In the case of ascent, the calculation rate is switched to take over, and in the case of descent, the calculation rate is switched when the count rate of both operations is within the allowable range. Switching can be performed without generating a step, a desired output response to an input change can be easily obtained, and a highly reliable radiation monitor in which both response and visibility can be obtained.

また、上昇時の切換点に対して下降時の切換点を低く設定することで、ハンチングを防止して安定な切換を行うことができる。また、標準偏差一定計数率は、時定数が計数率に反比例するので応答は速い反面、計数率分布はガウス分布からプラス側に歪んだ形になるため精度が低下することが特長であるのに対して、時間一定計数率は、応答は一定であるが、ガウス分布となるために精度の高い測定ができることが特長で、切換によりバックグラウンドレベルでは精度の高い測定を行うことができ、指示上昇に対しては応答を優先して短時間で高警報を発信できる効果を奏する。 Moreover, by setting the switching point at the time of lowering to the switching point at the time of rising, hunting can be prevented and stable switching can be performed. In addition, the standard deviation constant count rate has a quick response because the time constant is inversely proportional to the count rate, but the count rate distribution is distorted from the Gaussian distribution to the plus side, so the accuracy is reduced. On the other hand, the constant time count rate has a constant response, but it is characterized by high accuracy due to the Gaussian distribution. By switching, high accuracy measurement can be performed at the background level, and the indication rises. In response to this, it is possible to send a high warning in a short time by giving priority to the response.

１放射線検出器２波高弁別器
３カウンタ４演算器
５メモリー６表示器
７アップダウンカウンタ７１加算入力端子
７２減算入力端子８積算制御回路
９パルス発生器 DESCRIPTION OF SYMBOLS 1 Radiation detector 2 Wave height discriminator 3 Counter 4 Calculator 5 Memory 6 Display 7 Up / down counter 71 Addition input terminal 72 Subtraction input terminal 8 Integration control circuit 9 Pulse generator

Claims

A radiation detector that detects radiation and outputs an analog signal pulse, and outputs a digital pulse when the analog signal pulse is input and its crest level is within the allowable range, and is removed as noise when the allowable range is exceeded. A pulse height discriminator for counting, a counting means for inputting the digital pulse and counting in a fixed period and outputting a count value; storing the count value for a predetermined number of data in a first-in first-out method; and the latest data of the count rate calculation process And a storage means for calculating the count rate at regular intervals based on the count value, performing alarm determination on the calculated count rate or the engineering value converted from the count rate, and calculating the count rate or engineering value and the alarm determination result. A calculation means for outputting, and a display means for displaying the count rate or engineering value and the alarm determination result, the calculation means for each set count rate area When calculating the number rate, and switching from the count rate based on the measurement time to the count rate based on the standard deviation at the set count rate region boundary, the count rate before switching in the calculation cycle is taken over and switched, A radiation monitor characterized in that, when switching from a count rate based on a standard deviation to a count rate based on a measurement time, switching is performed when the difference between the count rates is within an allowable range.

The calculation means reads data from the storage means, subtracts the product of the previous count rate of the previous calculation cycle and the constant cycle count time from the current count value to obtain the current addition / subtraction, and multiplies the current addition / subtraction by a weighting factor. The current addition / subtraction integration value of the previous calculation cycle is added to obtain the current addition / subtraction integration value, and the standard deviation constant count rate calculation means for calculating the current count rate based on the current addition / subtraction integration value, and the past including the current count value And a measurement time constant count rate calculating means for integrating the count values for the calculation cycle set retroactively and dividing the integrated value by the corresponding integration time to obtain the current count rate. The radiation monitor according to claim 1 .

The calculation means sets the switching point when the counting rate is lowered to a lower switching point when the counting rate is higher than the switching point when the counting rate is increased at the switching point for obtaining the counting rate by switching between different standard deviations or standard deviation and measurement time. The radiation monitor according to claim 1 , wherein hysteresis is provided.