JP2930513B2 - Ventilation type ionization chamber - Google Patents
Ventilation type ionization chamberInfo
- Publication number
- JP2930513B2 JP2930513B2 JP30254693A JP30254693A JP2930513B2 JP 2930513 B2 JP2930513 B2 JP 2930513B2 JP 30254693 A JP30254693 A JP 30254693A JP 30254693 A JP30254693 A JP 30254693A JP 2930513 B2 JP2930513 B2 JP 2930513B2
- Authority
- JP
- Japan
- Prior art keywords
- ionization chamber
- ionization
- chamber
- gas
- housing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Description
【０００１】[0001]
【産業上の利用分野】本発明は、原子力、放射性物質取
り扱い施設における放射線計測、放射線管理等に適用可
能な通気型電離箱に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vented ionization chamber applicable to radiation measurement, radiation management, etc. in facilities for handling nuclear power and radioactive materials.
【０００２】[0002]
【従来の技術】従来、放射性ガスからの放射線を検出す
る装置として通気型電離箱やガスモニタが提案されてい
る。通気型電離箱は空気とともに放射性ガスを電離箱内
に導入し、放射線により生ずる電離電流を検出するもの
である。また、ガスモニタはＮａＩ等の放射線検出器を
設けた容器内に放射性ガスを導入し、放射線を検出する
ものである。2. Description of the Related Art Heretofore, ventilated ionization chambers and gas monitors have been proposed as devices for detecting radiation from radioactive gas. The ventilation ionization chamber is for introducing a radioactive gas into the ionization chamber together with air and detecting an ionization current generated by radiation. The gas monitor detects a radiation by introducing a radioactive gas into a container provided with a radiation detector such as NaI.
【０００３】[0003]
【発明が解決しようとする課題】従来の通気型電離箱
は、エネルギの異なる放射性ガス（核種）の弁別が不可
能であり、複数の核種が混在するときには電離電流値か
ら濃度換算することが困難であった。また、ＮａＩ（Ｔ
ｌ）等のγ線検出器を用いたガスモニタでは核種弁別は
可能であるものの、トリチウム（ 3Ｈ）炭素14（14Ｃ）
等のβ線のみを放出するガスに対しては測定できなかっ
た。In the conventional vented ionization chamber, it is impossible to discriminate radioactive gases (nuclides) having different energies, and when a plurality of nuclides are mixed, it is difficult to convert the concentration from the ionization current value. Met. In addition, NaI (T
l), etc., a gas monitor using a gamma ray detector can discriminate nuclides, but tritium ( 3 H) carbon 14 ( 14 C)
It was not possible to measure a gas that emits only β rays.
【０００４】本発明は上記課題を解決するためのもの
で、β線核種を含むエネルギの異なる核種の弁別が可能
な通過型電離箱を提供することを目的とする。An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a pass-type ionization chamber capable of discriminating nuclides having different energies including β-ray nuclides.
【０００５】[0005]
【課題を解決するための手段】本発明の通気型電離箱
は、中央に設けられた集電極と導電性物質からなる筐体
により構成された同軸円筒型の内側電離箱と、内側電離
箱の筐体を集電極とし、内側電離箱を囲む導電性物質か
らなる筐体により構成された外側電離箱との電極間距離
を異ならせ、内側電離箱、外側電離箱を通してガスを流
すとともに、内側電離箱の集電極と筐体、及び外側電離
箱の筐体にそれぞれ電圧を印加して各電離箱の電離電流
を測定するようにしたことを特徴とする。SUMMARY OF THE INVENTION A vented ionization chamber according to the present invention comprises a coaxial cylindrical inner ionization chamber constituted by a collector provided in the center and a housing made of a conductive material; The housing is used as a collector electrode, and the distance between the electrodes is made different from that of the outer ionization chamber, which is composed of a housing made of a conductive material surrounding the inner ionization chamber. A voltage is applied to each of the collector electrode and the housing of the box and the housing of the outer ionization chamber, and the ionization current of each ionization chamber is measured.
【０００６】[0006]
【作用】本発明は、中心に集電極を有する内側電離箱を
包囲して外側電離箱を形成し、内側電離箱の電極間距離
と、外側電離箱の電極間距離（外側電離箱の筐体と内側
電離箱の筐体間距離）を異ならせることにより両電離箱
の感度比を異ならせ、２つの電離箱の電離電流の比を読
み取ることによりエネルギの異なる核種の弁別が可能と
なり、また核種別濃度の測定が可能となる。According to the present invention, an outer ionization chamber is formed by surrounding an inner ionization chamber having a collector electrode at the center, and a distance between the electrodes of the inner ionization chamber and a distance between the electrodes of the outer ionization chamber (the housing of the outer ionization chamber). The distance between the ionization chambers and the inner ionization chamber is made different, the sensitivity ratio of both ionization chambers is made different, and by reading the ionization current ratio of the two ionization chambers, it becomes possible to discriminate nuclides having different energies. It is possible to measure the type concentration.
【０００７】[0007]
【実施例】図１は本発明の通気型電離箱の概念図、図２
は２つの電離箱の感度比を示す図である。図中、１は外
側電離箱、２は内側電離箱、３は内側電離箱集電極、
４，５は電池、６は内側電離箱電流計、７は外側電離箱
電流計、８は電位差計、９はガス入口、１０はガス出口
である。1 is a conceptual diagram of a vented ionization chamber according to the present invention, and FIG.
FIG. 3 is a diagram showing a sensitivity ratio of two ionization chambers. In the figure, 1 is an outer ionization chamber, 2 is an inner ionization chamber, 3 is an inner ionization chamber collector,
Reference numerals 4 and 5 denote batteries, 6 denotes an inner ionization chamber ammeter, 7 denotes an outer ionization chamber ammeter, 8 denotes a potentiometer, 9 denotes a gas inlet, and 10 denotes a gas outlet.
【０００８】本発明の通気型電離箱はステンレス鋼、ア
ルミニウム等の導電性物質で作られた同軸円筒型の電離
箱からなっており、図１に示すように、外側電離箱１内
に内側電離箱２が設けられた２重構造の電離箱からなっ
ている。外側電離箱１は内側電離箱２の筐体を集電極と
し、内側電離箱２はその中心部に内側電離箱集電極３が
設けられており、両電離箱の電極間距離は異ならせてあ
り、また容積も異なっている。内側電離箱２と内側電離
箱集電極３との間には電池４により、また外側電離箱１
と内側電離箱２との間には電池５により、それぞれ電圧
が印加され、各電離箱の電離電流は電流計６，７で読み
取られ、また電流計６，７で読み取られる値の比率が電
位差計８で求められるようになっている。測定すべき放
射性ガスはガス入口９を通して内側電離箱２内に導入さ
れ、外側電離箱１内を経由してガス出口１０より排気さ
れる。The vented ionization chamber of the present invention comprises a coaxial cylindrical ionization chamber made of a conductive material such as stainless steel, aluminum or the like. As shown in FIG. It consists of an ionization chamber of a double structure provided with a box 2. The outer ionization chamber 1 uses the housing of the inner ionization chamber 2 as a collector, and the inner ionization chamber 2 has an inner ionization chamber collector 3 at the center thereof, and the distance between the electrodes of the two ionization chambers is different. , And also have different volumes. A battery 4 is provided between the inner ionization chamber 2 and the inner ionization chamber collector electrode 3 and the outer ionization chamber 1
A battery 5 applies a voltage between the ionization chamber 2 and the inner ionization chamber 2, the ionization current of each ionization chamber is read by the ammeters 6, 7, and the ratio of the values read by the ammeters 6, 7 is the potential difference. A total of eight are required. The radioactive gas to be measured is introduced into the inner ionization chamber 2 through the gas inlet 9 and exhausted from the gas outlet 10 through the outer ionization chamber 1.
【０００９】次に放射性ガスに含まれる各種の弁別につ
いて説明すると、内側電離箱２の筐体（対電極）と集電
極３間の距離を、例えば２ｃｍ以下と短くし、外側電離
箱の筐体（対電極）とその集電極（内側電離箱２の筐
体）との距離を１０ｃｍ程度と長くしておく。Next, various discriminations contained in the radioactive gas will be described. The distance between the casing (counter electrode) of the inner ionization chamber 2 and the collecting electrode 3 is reduced to, for example, 2 cm or less, and the casing of the outer ionization chamber is reduced. The distance between the (counter electrode) and the collector (the housing of the inner ionization chamber 2) is set to be as long as about 10 cm.
【００１０】エネルギの高い放射線の場合、内側電離箱
内では放射線は直接内側電離箱２の壁部に当たって吸収
され、ほとんど電離に寄与しないが、外側電離箱内にお
いては、強い放射線であっても電極間距離が長いために
電離に寄与する。従って、エネルギの高い放射線は、電
流計６では検出効率が低く、電流計７で検出効率は高く
なる。In the case of high-energy radiation, in the inner ionization chamber, the radiation directly hits the wall of the inner ionization chamber 2 and is absorbed and hardly contributes to ionization. The long distance contributes to ionization. Therefore, radiation having high energy has low detection efficiency with the ammeter 6 and high detection efficiency with the ammeter 7.
【００１１】一方、エネルギの低い放射線の場合には、
電離箱の筐体に到達することなく、ほとんどが電離に寄
与し、内側電離箱、外側電離箱ともに電離が行われるこ
とになり、電流計６、電流計７で検出される。On the other hand, in the case of low energy radiation,
Most of the ions do not reach the housing of the ionization chamber and contribute to ionization, and ionization is performed in both the inner ionization chamber and the outer ionization chamber. The ionization is detected by the ammeter 6 and the ammeter 7.
【００１２】そこで、電流計６の検出値をＩ1 、電流計
７による検出値をＩ2 とし、Ｉ1 ／（Ｉ1 ＋Ｉ2 ）を感
度比として求める。エネルギの低い核種の場合、Ｉ1 、
Ｉ2とも検出されるので感度比は大きくなり、エネルギ
の高い核種がある場合、Ｉ1はほとんど検出されないた
め感度比は小さくなる。この感度比は内側電離箱、外側
電離箱それぞれの電極間距離によって変化し、また
Ｉ1 、Ｉ2 の大きさは電離箱の容積によって変化する。Therefore, the detection value of the ammeter 6 is I 1 , the detection value of the ammeter 7 is I 2, and I 1 / (I 1 + I 2 ) is obtained as the sensitivity ratio. For low energy nuclides, I 1 ,
Since I 2 is also detected, the sensitivity ratio increases, and when there is a nuclide with high energy, the sensitivity ratio decreases because I 1 is hardly detected. This sensitivity ratio changes depending on the distance between the electrodes of the inner ionization chamber and the outer ionization chamber, and the magnitudes of I 1 and I 2 change depending on the volume of the ionization chamber.
【００１３】図２は１例として内側電離箱を５ｃｍφ×
１４ｃｍ、外側電離箱を２５ｃｍφ×２４ｃｍとしたと
きの電離電流の比（計算値）をプロットしたものであ
る。図２において、横軸は核種のエネルギ、縦軸は感度
比である。このような特性を核種毎に予め求めてプロッ
トしておけば、未知の放射性ガスを導入したときに得ら
れた感度比よりそこに含まれる核種を特定し、かつその
濃度を求めることが可能となる。すなわち、両電離箱の
感度比から放射性ガスの平均エネルギが求められ、
3Ｈ、14Ｃ等の２核種混合ガスの場合にはその混合比
が、またそれぞれの電離電流計で測定した電流値から濃
度が求められることになる。この場合、β線エネルギが
１０ｋｅＶ〜１００ｋｅＶまでの範囲において、感度比
が大きく変化するためその比から 3Ｈ、14Ｃの核種は有
意に弁別することが可能である。FIG. 2 shows an example in which the inner ionization chamber is 5 cmφ ×
It is a plot of the ratio (calculated value) of ionization current when the outer ionization chamber is 14 cm and the outer ionization chamber is 25 cm × 24 cm. In FIG. 2, the horizontal axis is the energy of the nuclide, and the vertical axis is the sensitivity ratio. If such characteristics are obtained and plotted in advance for each nuclide, it is possible to identify the nuclide contained therein from the sensitivity ratio obtained when introducing an unknown radioactive gas, and to obtain its concentration. Become. That is, the average energy of the radioactive gas is obtained from the sensitivity ratio of both ionization chambers,
In the case of a mixed gas of two nuclides such as 3 H and 14 C, the mixture ratio is obtained, and the concentration is obtained from the current value measured by each ionization ammeter. In this case, when the β-ray energy is in the range of 10 keV to 100 keV, the sensitivity ratio greatly changes, so that 3 H and 14 C nuclides can be significantly discriminated from the ratio.
【００１４】なお、上記実施例においては内側電離箱の
電極間距離を外側電離箱の電極間距離よりも小さくした
が、もちろんその逆であってもよく、また電離箱は２つ
に限らず、さらに外側電離箱の外側にこれを包囲する電
離箱を形成するようにすることも可能である。In the above embodiment, the distance between the electrodes of the inner ionization chamber is made smaller than the distance between the electrodes of the outer ionization chamber. However, the reverse is also possible, and the number of ionization chambers is not limited to two. Further, an ionization chamber surrounding the outer ionization chamber may be formed outside the outer ionization chamber.
【００１５】[0015]
【発明の効果】以上のように本発明によれば、電極間距
離の異なる２つ以上の電離箱の感度比を利用することに
より、β線核種を含むエネルギの異なる放射性ガスの弁
別測定が可能となり、各電離箱の感度比からその混合ガ
スの混合比が、またそれぞれの電離電流値からガスの濃
度を求めることが可能となる。As described above, according to the present invention, discrimination measurement of radioactive gases having different energies including β-ray nuclides can be performed by using the sensitivity ratio of two or more ionization chambers having different electrode-to-electrode distances. It is possible to obtain the mixture ratio of the mixed gas from the sensitivity ratio of each ionization chamber and the gas concentration from each ionization current value.
【図１】 本発明の通気型電離箱の概念図である。FIG. 1 is a conceptual diagram of a ventilation type ionization chamber of the present invention.
【図２】 ２つの電離箱の感度比を示す図である。FIG. 2 is a diagram showing a sensitivity ratio of two ionization chambers.
１…外側電離箱、２…内側電離箱、３…内側電離箱集電
極、４，５…電池、６…内側電離箱電流計、７…外側電
離箱電流計、８…電位差計、９…ガス入口、１０…ガス
出口。DESCRIPTION OF SYMBOLS 1 ... Outer ionization chamber, 2 ... Inner ionization chamber, 3 ... Inner ionization chamber collector electrode, 4, 5 ... Battery, 6 ... Inner ionization chamber ammeter, 7 ... Outer ionization chamber ammeter, 8 ... Potentiometer, 9 ... Gas Inlet, 10 ... gas outlet.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭54−49186（ＪＰ，Ａ) 特開 昭56−72378（ＪＰ，Ａ) 特開 昭54−49187（ＪＰ，Ａ) 特開 昭55−117984（ＪＰ，Ａ) 実開 昭51−100574（ＪＰ，Ｕ) 特公 昭36−23550（ＪＰ，Ｂ１) (58)調査した分野(Int.Cl.6，ＤＢ名) H01J 47/00 - 47/26 G01T 1/185 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-49186 (JP, A) JP-A-56-72378 (JP, A) JP-A-54-49187 (JP, A) JP-A 55-49187 117984 (JP, A) Japanese Utility Model Showa 51-100574 (JP, U) JP-B 36-23550 (JP, B1) (58) Fields investigated (Int. Cl. 6 , DB name) H01J 47/00-47 / 26 G01T 1/185
Claims (1)
らなる筐体により構成された同軸円筒型の内側電離箱
と、内側電離箱の筐体を集電極とし、内側電離箱を囲む
導電性物質からなる筐体により構成された外側電離箱と
の電極間距離を異ならせ、内側電離箱、外側電離箱を通
してガスを流すとともに、内側電離箱の集電極と筐体、
及び外側電離箱の筐体にそれぞれ電圧を印加して各電離
箱の電離電流を測定するようにしたことを特徴とする通
気型電離箱。1. A coaxial cylindrical inner ionization chamber constituted by a collector electrode provided in the center and a housing made of a conductive material, a conductive member surrounding the inner ionization chamber, wherein the inner ionization box housing serves as a collector electrode. The distance between the electrode and the outer ionization chamber constituted by a housing made of a conductive material is varied, and the inner ionization chamber and the gas are flowed through the outer ionization chamber, and the collector electrode and the housing of the inner ionization chamber,
A ventilation type ionization chamber characterized in that a voltage is applied to each of the housings of the outer ionization chamber and the ionization current of each ionization chamber is measured.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30254693A JP2930513B2 (en) | 1993-12-02 | 1993-12-02 | Ventilation type ionization chamber |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30254693A JP2930513B2 (en) | 1993-12-02 | 1993-12-02 | Ventilation type ionization chamber |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07153418A JPH07153418A (en) | 1995-06-16 |
| JP2930513B2 true JP2930513B2 (en) | 1999-08-03 |
Family
ID=17910274
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP30254693A Expired - Fee Related JP2930513B2 (en) | 1993-12-02 | 1993-12-02 | Ventilation type ionization chamber |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2930513B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100912279B1 (en) * | 2009-04-07 | 2009-08-17 | 일진방사선 엔지니어링 (주) | Ionization chamber calibration supporter |
| JP2013543592A (en) * | 2010-10-07 | 2013-12-05 | エイチ．リー モフィット キャンサー センター アンド リサーチ インスティテュート | Method and apparatus for detecting radioisotopes |
| CN105629286B (en) * | 2016-01-28 | 2018-11-09 | 中国计量科学研究院 | A kind of ionisation chamber measuring Neutron Ambient Dose Equivalent |
-
1993
- 1993-12-02 JP JP30254693A patent/JP2930513B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07153418A (en) | 1995-06-16 |
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