JPH052115B2 - - Google Patents
Info
- Publication number
- JPH052115B2 JPH052115B2 JP11411985A JP11411985A JPH052115B2 JP H052115 B2 JPH052115 B2 JP H052115B2 JP 11411985 A JP11411985 A JP 11411985A JP 11411985 A JP11411985 A JP 11411985A JP H052115 B2 JPH052115 B2 JP H052115B2
- Authority
- JP
- Japan
- Prior art keywords
- rays
- tank
- radiation
- radioactive gas
- lining
- 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 - Lifetime
Links
- 230000005855 radiation Effects 0.000 claims description 19
- 230000002285 radioactive effect Effects 0.000 claims description 17
- 239000000463 material Substances 0.000 claims description 14
- 239000007789 gas Substances 0.000 description 16
- 230000005461 Bremsstrahlung Effects 0.000 description 10
- 230000005251 gamma ray Effects 0.000 description 9
- 238000005259 measurement Methods 0.000 description 9
- 230000005250 beta ray Effects 0.000 description 5
- 229910001220 stainless steel Inorganic materials 0.000 description 4
- 239000010935 stainless steel Substances 0.000 description 4
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000004809 Teflon Substances 0.000 description 2
- 229920006362 Teflon® Polymers 0.000 description 2
- 229910052790 beryllium Inorganic materials 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000000941 radioactive substance Substances 0.000 description 1
Landscapes
- Measurement Of Radiation (AREA)
Description
〔発明の利用分野〕
本発明は、原子力発電所等の放射性ガス分析に
係り、特に、γ線放出率の極単に小さい放射性該
種を正確に定量するのに好適な放射性ガス測定用
タンク（通称ガスサンプラ）に関する。
〔発明の背景〕
従来の放射性ガス測定用タンク（γ線の測定を
対象したタンク）を第２図に示す。このタンク１
は全体がステンレスでできており、下部の試料入
口２から放射性ガスを流入させ、上部側面の試料
出口３から流出させる構造になつている。タンク
の中央にウエル構造４を作り、その中に放射線検
出器５を設ける。タンク１内の放射性ガスから放
出する放射線はステンレス製のタンク１を透過
し、NaI（Tl）等による放射線検出器５に到達す
る。タンク１に入射する放射線がγ線で、かつ、
その該種のγ線放出率が大きい場合は、正確にそ
の放射線量を測定できる。しかし、γ線放出率が
小さい場合（１％以下）は、γ線と同時に放出す
るβ線とタンク１材料との相互作用で生じるＸ線
の影響が相対的に大きくなり、正確な放射線の測
定ができない。代表的な放射性ガスの該データを
表１に示す。多くのγ線放出核種はβ線の放出を
伴つている。表１にはγ線エネルギーγ(E)、その
放出率Ｂ（γ）と同時に放出するβ線のエネルギ
Ｂ(E)、その放出率Ｂ（β）を示す。第１表からも
わかるように、85Krのγ線放出率は0.43％と非
常に小さい。
[Field of Application of the Invention] The present invention relates to the analysis of radioactive gases in nuclear power plants, etc., and in particular to a radioactive gas measurement tank (commonly known as gas sampler). [Background of the Invention] FIG. 2 shows a conventional tank for measuring radioactive gas (a tank for measuring gamma rays). This tank 1
is made entirely of stainless steel, and has a structure in which radioactive gas flows in from a sample inlet 2 at the bottom and flows out from a sample outlet 3 at the upper side. A well structure 4 is created in the center of the tank, and a radiation detector 5 is provided therein. Radiation emitted from the radioactive gas in the tank 1 passes through the stainless steel tank 1 and reaches a radiation detector 5 based on NaI (Tl) or the like. The radiation incident on tank 1 is gamma rays, and
If the γ-ray emission rate of the species is high, the radiation dose can be measured accurately. However, when the gamma ray emission rate is small (1% or less), the influence of X-rays generated by the interaction between the beta rays emitted at the same time as the gamma rays and the tank 1 material becomes relatively large, making it difficult to measure radiation accurately. I can't. The data for representative radioactive gases are shown in Table 1. Many gamma-ray-emitting nuclides are accompanied by the emission of beta-rays. Table 1 shows the energy of γ-rays γ(E), its emission rate B(γ), the energy of β-rays emitted simultaneously B(E), and its emission rate B(β). As can be seen from Table 1, the gamma ray emission rate of 85Kr is extremely small at 0.43%.
本発明の目的は、γ線放出率の小さい放射性ガ
ス測定の測定精度を大幅に向上した放射性ガス測
定用タンクを提供することにある。
〔発明の概要〕
本発明は、γ線と同時に放出するβ線と、タン
ク材料の相互作用を検討し、β線とタンク材料の
相互作用で生ずるＸ線の主要な発生要因が、β線
の制動放射であることを見い出したことによる。
〔発明の実施例〕
以下、本発明の一実施例を第１図により説明す
る。放射性ガス測定用タンク１の下部から放射性
ガスを流入させ、上部側面から流出させる。タン
ク１の中央にウエル構造４を作り、その中に放射
線検出器５を設ける。タンク１の内面にはベリリ
ウム金属、あるいは、ポリテトラフルオロエチレ
ン（テフロン）等の原子番号の低い材料で内張り
６をする。内張りの厚さは、85Krのβ線最大飛程
と同じか、それ以上の寸法とする。β線の最大飛
程Ｒは、次式で決定する。
Ｒ（mg／cm2）＝407・E1.38
Ｅ：β線の最大エネルギー（MeV）
β線の最大エネルギーは、687KeV
（0.687MeV）であり、最大飛程は242mg／cm2とな
る。このβ線の最大飛程に内張りに用いる材料の
密度ρを乗ずることによつて、内張りの厚さを決
定できる。ベリリウムでは、約4.5mm、テフロン
では、約5.5mmとなる。制動放射線の放出割合は、
β線が入射する材料の原子番号に依存する。すな
わち、低原子番号の材料になるほど制動放射線の
発生は少ない。この制動放射線の発生量は材料、
入射β線のエネルギーで異なるが、85Krのβ線と
ステンレスとの間で発生する制動放射線の量は、
γ線放出数と同程度となる。
以上のことから、放射性ガス測定用タンクに、
低原子番号材料（ベリリウムの原子番号(Z)＝４、
テフロン(Z)≒８）を85Krのβ線を阻止できる厚
さ（飛程）に内張りすることによつて、制動放射
線の発生を抑えることができるようになる。この
内張りの厚さがβ線の飛程以下の場合には、タン
ク１の材料であるステンレス（主成分の鉄の原子
番号(Z)＝26）にβ線が到達し、制動放射線を発生
することになる。また、内張りの厚さは、制動放
射線の発生防止と云う面で厚い方が望ましい。し
かし、極端に厚すぎる場合は、逆に測定対象のγ
線自体の減衰が著しくなり、測定精度の低下を起
こすことになる。この点から、内張り材料の厚さ
は、β線の飛程と同程度が良いといえる。
第４図には、本発明の放射性ガス測定用タンク
を用いたときのγ線エネルギーと放射能濃度換算
係数（γμci／cm3・cpm）の関係を示す。第３図と
同様に、実線が計算値で、×印は実測値である。
第３図の従来法に比べ、信頼性の高い結果が得ら
れる。
本発明の変形例としてウエル構造の囲りだけに
低原子番号の材料で内張りする場合、あるいは、
ウエル構造以外のタンクや配管などを同材料で内
張りする場合などに考えられる。また、本発明
は、85Krだけを対象にした実施例で説明している
が他のγ線放出率が小さく、制動放射線が問題と
なる放射性物質についても、同様に適用できるも
のである。
〔発明の効果〕
本発明によれば、85Krなどのγ線放出率の小さ
い放射性ガスの測定に対し、制動放射線の影響が
無視でき、従来の測定用タンクに比べ50％以上の
精度向上を図ることができる。
An object of the present invention is to provide a tank for measuring radioactive gases that greatly improves the measurement accuracy of radioactive gases having a low gamma ray emission rate. [Summary of the Invention] The present invention investigates the interaction between β rays, which are emitted at the same time as γ rays, and tank materials, and determines that the main factor in the generation of X-rays caused by the interaction between β rays and tank material is β rays. This is due to the discovery that it is bremsstrahlung radiation. [Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIG. Radioactive gas is caused to flow in from the lower part of the radioactive gas measurement tank 1 and flowed out from the upper side surface. A well structure 4 is created in the center of the tank 1, and a radiation detector 5 is provided therein. The inner surface of the tank 1 is lined with a lining 6 of a material with a low atomic number such as beryllium metal or polytetrafluoroethylene (Teflon). The thickness of the lining shall be equal to or greater than the maximum beta range of 85 Kr. The maximum range R of β-rays is determined by the following formula. R (mg/cm 2 ) = 407・E 1.38 E: Maximum energy of β-ray (MeV) The maximum energy of β-ray is 687KeV
(0.687MeV), and the maximum range is 242mg/cm 2 . The thickness of the lining can be determined by multiplying the maximum range of this β ray by the density ρ of the material used for the lining. For beryllium, it is approximately 4.5 mm, and for Teflon, it is approximately 5.5 mm. The emission rate of bremsstrahlung radiation is
It depends on the atomic number of the material into which the β-rays are incident. In other words, the lower the atomic number of the material, the less bremsstrahlung radiation is generated. The amount of this bremsstrahlung radiation generated is
Although it differs depending on the energy of the incident β-ray, the amount of bremsstrahlung radiation generated between 85 Kr β-ray and stainless steel is:
The number is about the same as the number of gamma rays emitted. From the above, in the radioactive gas measurement tank,
Low atomic number materials (atomic number (Z) of beryllium = 4,
By lining it with Teflon (Z)≒8) to a thickness (range) that can block 85 Kr β-rays, it becomes possible to suppress the generation of bremsstrahlung radiation. If the thickness of this lining is below the range of the beta rays, the beta rays will reach the stainless steel (atomic number (Z) of the main component iron = 26), which is the material of tank 1, and generate bremsstrahlung radiation. It turns out. Further, it is desirable that the inner lining be thicker in order to prevent the generation of bremsstrahlung radiation. However, if it is extremely thick, the γ
Attenuation of the line itself becomes significant, resulting in a decrease in measurement accuracy. From this point of view, it can be said that the thickness of the lining material should be approximately the same as the range of β-rays. FIG. 4 shows the relationship between γ-ray energy and radioactivity concentration conversion coefficient (γμci/cm 3 ·cpm) when using the radioactive gas measurement tank of the present invention. As in FIG. 3, the solid lines are calculated values, and the x marks are actually measured values.
A more reliable result can be obtained compared to the conventional method shown in FIG. As a modification of the present invention, only the surround of the well structure is lined with a low atomic number material, or
This can be considered when lining tanks, piping, etc. other than well structures with the same material. Further, although the present invention has been described with reference to an embodiment that deals only with 85 Kr, it can be similarly applied to other radioactive substances with low gamma ray emission rates and where bremsstrahlung radiation is a problem. [Effects of the Invention] According to the present invention, the influence of bremsstrahlung radiation can be ignored when measuring radioactive gases such as 85 Kr with a low gamma ray emission rate, and the accuracy can be improved by more than 50% compared to conventional measurement tanks. can be achieved.
第１図は本発明の一実施例を示す図、第２図は
従来の放射性ガス測定用タンクを示す図、第３図
は従来の放射性ガス測定用タンクによるγ線エネ
ルギーと放射能濃度換算係数の関係を示す図、第
４図は本発明のタンクによるγ線エネルギーと放
射能濃度換算係数の関係を示す図である。
１…タンク、２…試料入口、３…試料出口、４
…ウエル構造、５…放射線検出器、６…低原子番
号材料の内張り。
Fig. 1 shows an embodiment of the present invention, Fig. 2 shows a conventional radioactive gas measurement tank, and Fig. 3 shows the gamma ray energy and radioactivity concentration conversion coefficient of a conventional radioactive gas measurement tank. FIG. 4 is a diagram showing the relationship between the γ-ray energy and the radioactivity concentration conversion coefficient by the tank of the present invention. 1...Tank, 2...Sample inlet, 3...Sample outlet, 4
...Well structure, 5. Radiation detector, 6. Lining of low atomic number material.
Claims (1)
いはウエル構造の内部に放射線検出器を設けて、
γ線を測定する容器において、容器内部に低原子
番号の材料を測定対象のγ線と同時放出するβ線
の最大飛程以上の厚さに内張りすることを特徴と
した放射性ガス測定容器。1. A radiation detector is installed outside the container or inside the well structure where radioactive gas is vented and stored,
A radioactive gas measuring container for measuring gamma rays, characterized in that the inside of the container is lined with a material with a low atomic number to a thickness greater than the maximum range of beta rays that are emitted simultaneously with gamma rays to be measured.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11411985A JPS61272679A (en) | 1985-05-29 | 1985-05-29 | Measuring container for radioactive gas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11411985A JPS61272679A (en) | 1985-05-29 | 1985-05-29 | Measuring container for radioactive gas |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61272679A JPS61272679A (en) | 1986-12-02 |
| JPH052115B2 true JPH052115B2 (en) | 1993-01-11 |
Family
ID=14629610
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11411985A Granted JPS61272679A (en) | 1985-05-29 | 1985-05-29 | Measuring container for radioactive gas |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61272679A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004286548A (en) * | 2003-03-20 | 2004-10-14 | Matsushita Electric Ind Co Ltd | Radiation measurement device |
| JP2017116349A (en) * | 2015-12-22 | 2017-06-29 | 株式会社東芝 | β RAY GAS MONITOR AND MONITORING METHOD FOR GAS CONTAINING NUCLEAR SPECIES EMITTING β RAY |
-
1985
- 1985-05-29 JP JP11411985A patent/JPS61272679A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61272679A (en) | 1986-12-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |