JP4330904B2

JP4330904B2 - Radiation detection method and apparatus

Info

Publication number: JP4330904B2
Application number: JP2003070260A
Authority: JP
Inventors: 宏隆酒井; 彰柚木
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2003-03-14
Filing date: 2003-03-14
Publication date: 2009-09-16
Anticipated expiration: 2023-03-14
Also published as: JP2004279184A

Description

【０００１】
【発明の属する技術分野】
本発明は、核燃料処理プラント、原子力発電所等の放射性物質取扱施設の大気中の放射性ダストを測定するために濾紙等に集塵されたダスト中の放射能強度を求めるのに適した放射線検出方法および装置に関する。
【０００２】
【従来の技術】
従来、α線放出核種検知用のダストモニタ向け放射線検出装置としてはシリコン半導体検出器が用いられ、β線放出核種検知用のダストモニタ向け放射線検出装置としてはプラスチックシンチレーション検出器が用いられている。そして通常、α線ダストモニタ向け放射線検出装置では、Rn（ラドン）およびTn（トロン）の影響を除去するために波高分析器などにより得られるエネルギー情報を利用して弁別を行っている。
【０００３】
近年、β線ダストモニタ向け放射線検出装置として、ZnS+プラスチックシンチレーション検出器により、β線だけでなくα線も同時に測定し、Rn-Tn放出核種によるβ線測定時の影響を排除する装置が提案されている。しかし、この装置ではα線のエネルギー情報はほとんど取得できないので、Rn-Tnと、Rn-Tn以外のα線放出核種のダスト放射線濃度を弁別して測定することはできない。そのため、１台のダストモニタ向け放射線検出装置でRn-Tnの影響を除去しつつ人工のα線放出核種、β線放出核種のダスト濃度を同時に測定することはできない（下記特許文献１，２，３，４参照）。
【０００４】
【特許文献１】
特開平８−１３６６５８号公報
【特許文献２】
特開平９−１５３３６号公報
【特許文献３】
特開平１１−６４５２９号公報
【特許文献４】
特開２００１−２４２２５１号公報
【０００５】
【発明が解決しようとする課題】
本発明は、１台の検出部でRn-Tnによる影響を排除しつつα線放出核種およびβ線放出核種の濃度を測定することのできる放射線検出方法および装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
上記課題を解決するために、請求項１の発明は、α線およびβ線を検出したときα線検出信号およびβ線検出信号を出力するα／β検出部と、前記α／β検出部から前記α線検出信号および前記β線検出信号を受けてα線の信号およびβ線の信号を出力するとともに、前記α線検出信号の検出時間と前記β線検出信号の検出時間との間の時間差情報から所定の相関のある事象を抽出して相関事象信号を出力する相関事象抽出部と、前記相関事象抽出部から前記α線の信号、前記β線の信号および前記相関事象信号を受けて、前記α線の信号の数および前記β線の信号の数から前記相関事象信号の数にラドンおよびトロンの壊変に係る補正を施した値を引き算するデータ処理部とを備えた構成とする。
【０００７】
請求項２の発明は、α線およびβ線を検出したときα線検出信号およびβ線検出信号を出力するα／β検出部と、前記α／β検出部から前記α線検出信号および前記β線検出信号を受けて前記α線検出信号の検出時間と前記β線検出信号の検出時間との間の時間差情報から所定の相関のある事象を抽出して相関事象信号を出力する相関事象抽出部と、前記α／β検出部から出力される前記α線検出信号および前記β線検出信号と前記相関事象抽出部から出力される前記相関事象信号を受けて、α線の信号の数およびβ線の信号の数から前記相関事象信号の数にラドンおよびトロンの壊変に係る補正を施した値を引き算するデータ処理部とを備えた構成とする。
【０００８】
請求項３の発明は、α線およびβ線の入射により信号を発生するα／β検出部から信号を受けて信号の波形処理を行う波形処理部と、前記波形処理部から信号を受けて計数処理を行うデータ処理部とを備え、前記波形処理部は、α線の入射による信号とβ線の入射による信号を波形弁別にて分離検出する波形弁別ブロックと、前記α線検出信号の検出時間と前記β線検出信号の検出時間との間の時間差情報から両者の相関関係を求める相関事象抽出ブロックとを備え、前記データ処理部は、α線の信号の数およびβ線の信号の数から相関事象抽出数にラドンおよびトロンの壊変に係る補正を施した値を引き算する減算機能を備えた構成とする。
【０００９】
請求項４の発明は、前記波形弁別ブロックはダブルパルスを分離する機能を備えた構成とする。
【００１０】
請求項５の発明は、α線検出信号の検出時間とβ線検出信号の検出時間との間の時間差情報から所定の相関のある事象を抽出して相関事象信号を生成し、α線の信号の数およびβ線の信号の数から前記相関事象信号の数にラドンおよびトロンの壊変に係る補正を施した値を引き算してα線の強度およびβ線の強度を求める構成とする。
【００１１】
【発明の実施の形態】
本発明の第１の実施の形態を図１，図２を参照して説明する。この実施の形態は本発明をダストモニタ向け放射線検出装置として適用した場合の例である。本実施の形態の放射線検出装置は図１に示すように、α線とβ線を検出するα／β検出部１と、相関事象抽出部２と、データ処理部３からなり、これらは信号線１０によって接続されている。
【００１２】
α／β検出部１は、ZnS（Ag）とプラスチックシンチレータからなる放射線検出素子４と、光電子増倍管５と、α／β弁別回路６からなり、α出力端子７ａとβ出力端子８ａを備えている。相関事象抽出部２にはα出力端子７ｂとβ出力端子８ｂと相関事象出力端子９が設けられている。なお、ZnS（Ag）は硫化亜鉛に銀が添加されα線によってZnSより感度良く発光するシンチレータ物質である。
【００１３】
表面側に薄いZnS(Ag)層を有し、光電子増倍管５側に比較的厚いプラスチックシンチレータ層を有する放射線検出素子４に放射線が入射した際、透過力の弱いα線はそのエネルギーのほとんど全てをZnS(Ag)層で失い、透過力がα線より強いβ線はそのエネルギーの大半をプラスチックシンチレータ層で失う。
【００１４】
ZnS(Ag)に放射線によりエネルギーが付与された際の発光時間は長く、プラスチックシンチレータに放射線によりエネルギーが付与された際の発光時間は短い。そのため、光電子増倍管５によって、これらの発光を電気信号に変換し、この電気信号をα／β弁別回路６によって波形弁別することにより、α線入射による発光と、β線入射による発光を弁別することができる。こうした弁別結果にしたがい、α／β検出部１は、それぞれα出力端子７ａ、β出力端子８ａに論理パルスを出力する。
【００１５】
さて、通常のα線、β線は時間的にランダムに入射しており、その間に相関はない。通常、測定対象とする作業環境のモニタリング、あるいはプロセスモニタリングの対象となる人工放射能はこうした時間関係がランダムである。一方、作業環境モニタリング、あるいはプロセスモニタリングの際に測定対象とならない物質として、Rn、Tn及び、それらの娘核種がある。これら天然放射能はバックグラウンド成分として差し引く必要がある。
【００１６】
まず、Rnの娘核種で
Bi-214→(β線放出)→Po-214(半減期 164μsec)→(α線放出)→Pb-210
という連続壊変が存在する。ここで放出されるβ線、α線については、164μ秒以内に50%の確率で連続的に放出されるという時間的な相関がある。そこで、相関事象抽出部２において、図２のようなタイミングにおいて適切な時間設定、例えばＢを100μsec、Tを300μsecにすることによって、この事象を選択して取り出すことができる。相関事象抽出部２はこうした働きをし、その出力（ｄ）はデータ処理部３に伝えられ、データ処理部３においてBi-214由来のβ線とα線の計数率が求められる。
【００１７】
事前にBi-214から始まる連続壊変のα／β検出部１での検出確率を求めておくことによって、相関事象出力の計数率よりRnの娘核種であるBi-214の濃度D_Bi-214(Bq/cm³)を求めることができる。環境条件が大きく変化しない限り、RnやTnの娘核種の存在割合は一定であり、さらに、Rn対Tn比も一定である場合には、Bi-214のRn娘核種全体に対する割合をr_Bi-214、Tn娘核種全体のRnに対する存在比をr_Tnとすると、Rn及びTn娘核種全体の全濃度D_Rn-Tn(Bq/cm³)は、
【数１】

という形で求めることができる。
【００１８】
また、α線の検出効率とβ線の検出効率を事前に求めておくことによって、α線の計数率からRn-Tnの影響も含めたα線放出核種の濃度D_αを求めることができ、β線の計数率からRn-Tnの影響も含めたβ線放出核種の濃度D_βを求めることができる。さらに、事前にデータ処理部３にRn-Tn娘核種でのα線放出核種の割合r_αと、β線放出核種の割合r_βを備えておくことにより、Rn-Tnの影響を除いたα線放出核種の濃度D_T _αおよびβ線放出核種の濃度D_T _βはそれぞれ、
D_T _α = D_α−r_α×D_Rn-Tn
D_T _β = D_β−r_β×D_Rn-Tn
という関係により求めることができる。
【００１９】
つぎに本発明の第２の実施の形態を説明する。
本実施の形態の放射線検出装置は図３に示すように、α線とβ線を検出するα／β検出部１と、相関事象抽出部２と、データ処理部３からなり、これらは信号線１０によって接続されている。α／β検出部１は、ZnS（Ag）とプラスチックシンチレータからなる放射線検出素子４と、光電子増倍管５と、α／β弁別回路６からなり、α出力端子７ａとβ出力端子８ａを備えている。相関事象抽出部２には相関事象出力端子９が設けられている。
【００２０】
この実施の形態の放射線検出装置は、相関事象抽出部２の出力を相関事象に関するもののみとし、α出力、β出力については、α／β検出部１の出力を分岐してデータ処理部３に直接入力する構成としたものである。この実施の形態によれば、相関事象抽出部２の構成を簡素化し出力点数を削減することができる。
【００２１】
つぎに本発明の第３の実施の形態を説明する。
本実施の形態の放射線検出装置は図４に示すように、α線とβ線を検出するα／β検出部１と、このα／β検出部１の出力側に一体的に構成された波形処理部１１と、この波形処理部１１の出力側に信号線１０によって接続されたデータ処理部３からなる。α／β検出部１は、ZnS（Ag）とプラスチックシンチレータからなる放射線検出素子４と、光センサ１５とからなる。波形処理部１１は、前置増幅器１２と波形弁別ブロック１３と相関事象抽出ブロック１４とからなり、α出力端子７とβ出力端子８と相関事象出力端子９が設けられている。
【００２２】
この実施の形態においては、各ブロックの機能を論理回路で構成し、波形処理の初期段階において波形情報をディジタル化することができる。したがって本実施の形態によれば、小型でノイズに強い放射線検出装置を提供することができる。
【００２３】
前記第１、第２の実施の形態は、Rn系列のBi-214から始まる半減期164μsecの時間間隔の連続壊変のみを利用している。一方、Tn系列では、
Bi-212→(β線放出)→Po-212(半減期 0.305μsec)→(α線放出)→Pb-208
という短い時間間隔で連続壊変する核種が存在する。この核種の場合、壊変の時間間隔が短いため図５に示すようにダブルパルスとなりやすく、分離することが難しい。しかしながら、波形処理部１１において波形を解析し、通常とは異なる形状であるダブルパルスを識別し、それを分離することでこの短い壊変による計数を除外することができるようになる。したがって本実施の形態の放射線検出装置は、Rn、Tnの濃度を個別に同定することができ、Rn-Tn比が一定であるという環境に当てはまらない、Rn-Tn比が変動するような環境での測定に適用することができる。
【００２４】
なお、前記第１〜第３の実施の形態で着目しているRnあるいはTn娘核種の連続壊変は、測定対象となる核種がダストモニタの吸着面に固定されているため、そのβ線およびα線を放出する場所は同じである。そこで、検出面とダスト吸着面との距離が短い場合、放射線検出面を２次元の位置検出型とし、着目するβ／α連続壊変を判定する基準として、β線、α線の検出位置の距離というパラメータを加えることで、より高精度にRnあるいは、Tn娘核種の濃度を推定することができる。
【００２５】
【発明の効果】
本発明によれば、１台の検出部でRn-Tnによる影響を排除しつつα線放出核種およびβ線放出核種の濃度を測定することのできる放射線検出方法および装置を提供することができる。
【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検出装置を示すブロック図。
【図２】本発明の第１の実施の形態の放射線検出装置の動作を説明する波形図。
【図３】本発明の第２の実施の形態の放射線検出装置を示すブロック図。
【図４】本発明の第３の実施の形態の放射線検出装置を示すブロック図。
【図５】本発明の第３の実施の形態の放射線検出装置の動作を説明する波形図。
【符号の説明】
１…α／β検出部、２…相関事象抽出部、３…データ処理部、４…放射線検出素子、５…光電子増倍管、６…α／β弁別回路、７，７ａ，７ｂ…α出力端子、８，８ａ，８ｂ…β出力端子、９…相関事象出力端子、１０…信号線、１１…波形処理部、１２…前置増幅器、１３…波形弁別ブロック、１４…相関事象抽出ブロック、１５…光センサ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation detection method suitable for obtaining radioactivity intensity in dust collected on filter paper or the like in order to measure radioactive dust in the atmosphere of radioactive material handling facilities such as nuclear fuel processing plants and nuclear power plants. And device.
[0002]
[Prior art]
Conventionally, a silicon semiconductor detector is used as a radiation detection device for dust monitor for detecting α-ray emission nuclide, and a plastic scintillation detector is used as a radiation detection device for dust monitor for detecting β-ray emission nuclide. Usually, in a radiation detection apparatus for an α-ray dust monitor, discrimination is performed using energy information obtained by a pulse height analyzer or the like in order to remove the influence of Rn (Radon) and Tn (Tron).
[0003]
In recent years, as a radiation detector for β-ray dust monitors, a ZnS + plastic scintillation detector has been proposed to simultaneously measure not only β rays but also α rays, eliminating the effects of Rn-Tn emitting nuclides when measuring β rays. ing. However, since this device can hardly acquire α-ray energy information, it cannot discriminate and measure the dust radiation concentration of Rn-Tn and α-ray emitting nuclides other than Rn-Tn. For this reason, it is not possible to simultaneously measure the dust concentration of artificial α-ray emission nuclides and β-ray emission nuclides while removing the influence of Rn-Tn with a single radiation monitor for dust monitor (Patent Documents 1 and 2 below) 3 and 4).
[0004]
[Patent Document 1]
JP-A-8-136658 [Patent Document 2]
JP-A-9-15336 [Patent Document 3]
Japanese Patent Laid-Open No. 11-64529 [Patent Document 4]
Japanese Patent Laid-Open No. 2001-242251
[Problems to be solved by the invention]
An object of the present invention is to provide a radiation detection method and apparatus capable of measuring the concentrations of α-ray emitting nuclides and β-ray emitting nuclides while eliminating the influence of Rn-Tn with a single detector.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention of claim 1 includes an α / β detector that outputs an α-ray detection signal and a β-ray detection signal when detecting α-rays and β-rays, and the α / β detector The α ray detection signal and the β ray detection signal are received and an α ray signal and a β ray signal are output, and a time difference between the detection time of the α ray detection signal and the detection time of the β ray detection signal A correlation event extraction unit that extracts a predetermined correlated event from information and outputs a correlation event signal; and receives the α ray signal, the β ray signal, and the correlation event signal from the correlation event extraction unit, And a data processing unit that subtracts a value obtained by correcting the number of the correlation event signals from the number of the α-ray signals and the number of the β-ray signals and correcting the radon and thoron decay.
[0007]
The invention of claim 2 includes an α / β detector that outputs an α-ray detection signal and a β-ray detection signal when detecting an α-ray and a β-ray, and the α-ray detection signal and the β that are output from the α / β detector. A correlation event extraction unit that receives a line detection signal , extracts an event having a predetermined correlation from time difference information between the detection time of the α-ray detection signal and the detection time of the β-ray detection signal , and outputs a correlation event signal And receiving the α-ray detection signal and the β-ray detection signal output from the α / β detection unit and the correlation event signal output from the correlation event extraction unit, and the number of α-ray signals and β-rays And a data processing unit that subtracts a value obtained by correcting the number of correlation event signals from the number of the above-mentioned correlation event signals.
[0008]
According to a third aspect of the present invention, there is provided a waveform processing unit that receives a signal from an α / β detection unit that generates a signal by incidence of α rays and β rays and performs signal waveform processing, and receives the signal from the waveform processing unit and performs counting. A data processing unit that performs processing, wherein the waveform processing unit separates and detects a signal due to incidence of α rays and a signal due to incidence of β rays by waveform discrimination, and a detection time of the α ray detection signal And a correlation event extraction block for obtaining a correlation between the two from the time difference information between the β-ray detection signal and the detection time of the β-ray detection signal, and the data processing unit is based on the number of α-ray signals and the number of β-ray signals. The number of correlation event extractions is configured to have a subtraction function that subtracts a value obtained by correcting radon and thoron destruction.
[0009]
According to a fourth aspect of the present invention, the waveform discrimination block has a function of separating double pulses.
[0010]
The invention according to claim 5 extracts an event having a predetermined correlation from the time difference information between the detection time of the α-ray detection signal and the detection time of the β-ray detection signal, generates a correlation event signal, and generates an α-ray signal. And the number of correlation event signals are subtracted from the number of correlation signals and the number of β-ray signals to obtain the intensity of α-rays and the intensity of β-rays.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. This embodiment is an example when the present invention is applied as a radiation detection apparatus for a dust monitor. As shown in FIG. 1, the radiation detection apparatus according to the present embodiment includes an α / β detection unit 1 that detects α rays and β rays, a correlation event extraction unit 2, and a data processing unit 3, which are signal lines. 10 are connected.
[0012]
The α / β detector 1 includes a radiation detection element 4 made of ZnS (Ag) and a plastic scintillator, a photomultiplier tube 5, and an α / β discrimination circuit 6, and includes an α output terminal 7a and a β output terminal 8a. ing. The correlation event extraction unit 2 is provided with an α output terminal 7b, a β output terminal 8b, and a correlation event output terminal 9. ZnS (Ag) is a scintillator substance that emits light with higher sensitivity than ZnS by adding silver to zinc sulfide.
[0013]
When radiation is incident on the radiation detecting element 4 having a thin ZnS (Ag) layer on the surface side and a relatively thick plastic scintillator layer on the photomultiplier tube 5 side, the α-ray having a low transmission power is almost all of its energy. All is lost in the ZnS (Ag) layer, and β-rays, whose transmission power is stronger than α-rays, lose most of their energy in the plastic scintillator layer.
[0014]
The emission time when energy is applied to ZnS (Ag) by radiation is long, and the emission time when energy is applied to the plastic scintillator by radiation is short. Therefore, the photomultiplier tube 5 converts these luminescences into electrical signals, and the electrical signals are subjected to waveform discrimination by the α / β discriminating circuit 6, thereby discriminating between the luminescence caused by the α ray incidence and the luminescence caused by the β ray incidence. can do. According to such discrimination results, the α / β detector 1 outputs a logic pulse to the α output terminal 7a and the β output terminal 8a, respectively.
[0015]
Now, normal α rays and β rays are incident at random in time, and there is no correlation between them. Usually, the time relationship is random for the artificial radioactivity that is the subject of monitoring the work environment or process monitoring. On the other hand, there are Rn, Tn, and their daughter nuclides as substances that are not measured during work environment monitoring or process monitoring. These natural radioactivity needs to be subtracted as a background component.
[0016]
First, the daughter nuclide of Rn
Bi-214 → (β-ray emission) → Po-214 (half-life 164 μsec) → (α-ray emission) → Pb-210
There is a continuous destruction. The β ray and α ray emitted here have a temporal correlation that they are emitted continuously with a probability of 50% within 164 μs. Therefore, the correlation event extraction unit 2 can select and extract this event by setting an appropriate time at the timing as shown in FIG. 2, for example, by setting B to 100 μsec and T to 300 μsec. The correlation event extraction unit 2 performs such a function, and its output (d) is transmitted to the data processing unit 3, and the data processing unit 3 obtains the counting rates of β-rays and α-rays derived from Bi-214.
[0017]
By obtaining the detection probability in the α / β detector 1 of the continuous decay starting from Bi-214 in advance, the concentration D _Bi-214 of Bi-214, the daughter nuclide of Rn, is determined from the count rate of the correlation event output. Bq / cm ³ ) can be obtained. Unless the environmental conditions change significantly, the ratio of Rn and Tn daughter nuclides is constant, and if the ratio of Rn to Tn is also constant, the ratio of Bi-214 to the total Rn daughter nuclides is expressed as r _{Bi- 214} , if the ratio of Rn to the total Tn daughter nuclide is R _Tn , the total concentration D _Rn-Tn (Bq / cm ³ ) of the total Rn and Tn daughter nuclide is
[Expression 1]

It can be obtained in the form of
[0018]
In addition, by obtaining α ray detection efficiency and β ray detection efficiency in advance, the α ray emission nuclide concentration D _α including the influence of Rn-Tn can be obtained from the α ray count rate, it is possible to determine the concentration D _beta of beta-emitting nuclides, including the effects of Rn-Tn from the counting rate of beta rays. Furthermore, by providing the data processing unit 3 with a ratio r _α of α-emitting nuclides in Rn-Tn daughter nuclides and a ratio r _β of _β- emitting nuclides in advance, α that excludes the influence of Rn-Tn The concentration of radiation emitting nuclides D _T _α and the concentration of β emitting nuclides D _T _β
D _T _α = D _α −r _α × D _Rn-Tn
D _T _β = D _β −r _β × D _Rn-Tn
It can be obtained from the relationship.
[0019]
Next, a second embodiment of the present invention will be described.
As shown in FIG. 3, the radiation detection apparatus according to the present embodiment includes an α / β detector 1 that detects α rays and β rays, a correlation event extractor 2, and a data processor 3, which are signal lines. 10 are connected. The α / β detector 1 includes a radiation detection element 4 made of ZnS (Ag) and a plastic scintillator, a photomultiplier tube 5, and an α / β discrimination circuit 6, and includes an α output terminal 7a and a β output terminal 8a. ing. The correlation event extraction unit 2 is provided with a correlation event output terminal 9.
[0020]
In the radiation detection apparatus of this embodiment, the output of the correlation event extraction unit 2 is only related to the correlation event, and the output of the α / β detection unit 1 is branched to the data processing unit 3 for the α output and β output. It is configured to input directly. According to this embodiment, the configuration of the correlation event extracting unit 2 can be simplified and the number of output points can be reduced.
[0021]
Next, a third embodiment of the present invention will be described.
As shown in FIG. 4, the radiation detection apparatus of the present embodiment has an α / β detector 1 that detects α rays and β rays, and a waveform that is integrally formed on the output side of the α / β detector 1. The processing unit 11 includes a data processing unit 3 connected to the output side of the waveform processing unit 11 by a signal line 10. The α / β detection unit 1 includes a radiation detection element 4 made of ZnS (Ag) and a plastic scintillator, and an optical sensor 15. The waveform processing unit 11 includes a preamplifier 12, a waveform discrimination block 13, and a correlation event extraction block 14, and is provided with an α output terminal 7, a β output terminal 8, and a correlation event output terminal 9.
[0022]
In this embodiment, the function of each block is configured by a logic circuit, and the waveform information can be digitized at the initial stage of waveform processing. Therefore, according to the present embodiment, it is possible to provide a radiation detection device that is small and resistant to noise.
[0023]
The first and second embodiments utilize only continuous decay of a time interval of 164 μsec half-life starting from Rn series Bi-214. On the other hand, in the Tn series,
Bi-212 → (β-ray emission) → Po-212 (half-life 0.305 μsec) → (α-ray emission) → Pb-208
There are nuclides that decay continuously at short time intervals. In the case of this nuclide, since the time interval of decay is short, it tends to be a double pulse as shown in FIG. 5 and is difficult to separate. However, the waveform processing unit 11 analyzes the waveform, identifies a double pulse having a shape different from the normal one, and separates it, so that the count due to this short decay can be excluded. Therefore, the radiation detection apparatus according to the present embodiment can individually identify the concentrations of Rn and Tn, and does not apply to an environment where the Rn-Tn ratio is constant, in an environment where the Rn-Tn ratio varies. It can be applied to the measurement of
[0024]
Note that the continuous decay of Rn or Tn daughter nuclides focused on in the first to third embodiments is because the nuclides to be measured are fixed on the adsorption surface of the dust monitor. The location for emitting the line is the same. Therefore, when the distance between the detection surface and the dust adsorption surface is short, the radiation detection surface is a two-dimensional position detection type, and the distance between the detection positions of β rays and α rays is used as a reference for determining the β / α continuous decay of interest. By adding the parameter, it is possible to estimate the concentration of Rn or Tn daughter nuclide with higher accuracy.
[0025]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the radiation detection method and apparatus which can measure the density | concentration of an alpha ray emission nuclide and a beta ray emission nuclide, eliminating the influence by Rn-Tn with one detection part can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a radiation detection apparatus according to a first embodiment of the present invention.
FIG. 2 is a waveform diagram for explaining the operation of the radiation detection apparatus according to the first embodiment of the present invention.
FIG. 3 is a block diagram showing a radiation detection apparatus according to a second embodiment of the present invention.
FIG. 4 is a block diagram showing a radiation detection apparatus according to a third embodiment of the present invention.
FIG. 5 is a waveform diagram for explaining the operation of the radiation detection apparatus according to the third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... alpha / beta detection part, 2 ... Correlation event extraction part, 3 ... Data processing part, 4 ... Radiation detection element, 5 ... Photomultiplier tube, 6 ... alpha / beta discrimination circuit, 7, 7a, 7b ...

alpha output Terminal

8, 8 a, 8 b .beta. Output terminal 9 .correlation event output terminal 10... Signal line 11 .waveform processing unit 12 preamplifier 13 wave shape discrimination block 14 correlation event extraction block 15 ... light sensor.

Claims

an α / β detector that outputs an α-ray detection signal and a β-ray detection signal when detecting an α-ray and a β-ray; and an α / β detector that receives the α-ray detection signal and the β-ray detection signal from the α / β detector Output a line signal and a β-line signal, and extract a correlation event signal by extracting a predetermined correlated event from time difference information between the detection time of the α-ray detection signal and the detection time of the β-ray detection signal A correlation event extraction unit that outputs the α ray signal, the β ray signal, and the correlation event signal from the correlation event extraction unit, and the number of α ray signals and the number of β ray signals. And a data processing unit for subtracting a value obtained by correcting the number of correlation event signals related to radon and thoron decay.

an α / β detector that outputs an α-ray detection signal and a β-ray detection signal when detecting an α-ray and a β-ray, and the α-β detection signal and the β-ray detection signal received from the α / β detector a correlation event extraction unit for extracting a predetermined correlated event from time difference information between the detection time of the α-ray detection signal and the detection time of the β-ray detection signal and outputting a correlation event signal; and the α / β detection In response to the α-ray detection signal and β-ray detection signal output from the unit and the correlation event signal output from the correlation event extraction unit, the correlation is calculated from the number of α-ray signals and the number of β-ray signals. A radiation detection apparatus, comprising: a data processing unit that subtracts a value obtained by correcting the number of event signals according to radon and thoron breakdown.

a waveform processing unit that receives a signal from an α / β detection unit that generates a signal by the incidence of α rays and β rays, and a signal processing unit that receives the signal from the waveform processing unit and performs a counting process; The waveform processing unit includes: a waveform discrimination block for separating and detecting a signal due to incidence of α rays and a signal due to incidence of β rays by waveform discrimination; a detection time of the α ray detection signal; and a β ray detection signal A correlation event extraction block for obtaining a correlation between the two based on time difference information between the detection time and the data processing unit. A radiation detection apparatus comprising a subtraction function for subtracting a value subjected to correction related to TRON destruction.

The radiation detection apparatus according to claim 3, wherein the waveform discrimination block has a function of separating a double pulse.

A correlation event signal is generated by extracting a predetermined correlated event from the time difference information between the detection time of the α ray detection signal and the detection time of the β ray detection signal , and the number of α ray signals and the β ray signals are generated. A radiation detection method, comprising: subtracting a value obtained by correcting radon and thoron decay correction from the number of correlation event signals to obtain the intensity of α rays and the intensity of β rays.