JP2931750B2 - Continuous measurement method of radioactive iodine in off-gas - Google Patents
Continuous measurement method of radioactive iodine in off-gasInfo
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- JP2931750B2 JP2931750B2 JP30868793A JP30868793A JP2931750B2 JP 2931750 B2 JP2931750 B2 JP 2931750B2 JP 30868793 A JP30868793 A JP 30868793A JP 30868793 A JP30868793 A JP 30868793A JP 2931750 B2 JP2931750 B2 JP 2931750B2
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- radioactive
- radioactive iodine
- energy
- gas
- iodine
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、核燃料関連施設オフガ
ス中の放射性ヨウ素を連続測定する方法に関し、更に詳
しく述べると、オフガス中に同時に混在する放射性希ガ
スによる妨害を除去して放射性ヨウ素の量のみを連続測
定する方法に関するものである。この方法は、核燃料再
処理施設、原子炉施設、放射性廃棄物施設、放射性ヨウ
素使用施設からのオフガス中の放射性ヨウ素の量の測
定、監視に利用できる。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously measuring radioactive iodine in an off-gas of a nuclear fuel-related facility, and more particularly to a method for removing radioactive iodine by removing interference caused by a radioactive noble gas mixed in the off-gas. It relates to a method for continuously measuring only This method can be used to measure and monitor the amount of radioactive iodine in off-gas from nuclear fuel reprocessing facilities, nuclear reactor facilities, radioactive waste facilities, and radioactive iodine use facilities.
【０００２】[0002]
【従来の技術】核燃料関連施設から生じる気体廃棄物中
には様々な放射性核種が含まれる可能性があり、そのう
ち環境への放出が問題になるものの一つとして放射性ヨ
ウ素がある。従来、放射性ヨウ素の測定及び監視は、オ
フガスの一部を活性炭などの吸着材に連続的に導いて放
射性ヨウ素を吸着させ、吸着した放射性ヨウ素の放射線
をＮａＩシンチレーション検出器で連続測定すると共
に、任意期間吸着させた吸着材を回収して半導体検出器
等で精密測定することにより監視している。2. Description of the Related Art Various radionuclides may be contained in gaseous wastes generated from nuclear fuel-related facilities, and radioactive iodine is one of the substances whose release to the environment is a problem. Conventionally, the measurement and monitoring of radioactive iodine is performed by continuously guiding a part of the off-gas to an adsorbent such as activated carbon to adsorb radioactive iodine, continuously measuring the radiation of the adsorbed radioactive iodine with a NaI scintillation detector, and optionally. The adsorbent that has been adsorbed during the period is collected and monitored by precision measurement with a semiconductor detector or the like.
【０００３】ここで連続測定の方法は、ＮａＩシンチレ
ーション検出器のエネルギー信号のうち、放射性ヨウ素
の放射線のエネルギー範囲を選別して、放射性ヨウ素の
みを測定するという方法である。ＮａＩシンチレーショ
ン検出器によって核燃料再処理施設のオフガス中の放射
性ヨウ素のエネルギー（例えばヨウ素-129）を測定する
と、図２のような結果が得られる。連続モニタでは、こ
の分布状況に合わせて放射性ヨウ素のエネルギー分布の
範囲を決定し、その中に入った放射線を放射性ヨウ素と
して測定する。Here, the continuous measurement method is a method in which the energy range of radioactive iodine radiation is selected from the energy signals of the NaI scintillation detector, and only radioactive iodine is measured. When the energy of radioactive iodine (for example, iodine-129) in the off-gas of the nuclear fuel reprocessing facility is measured by the NaI scintillation detector, the result as shown in FIG. 2 is obtained. In the continuous monitor, the range of the energy distribution of radioactive iodine is determined in accordance with the distribution state, and the radiation that enters therein is measured as radioactive iodine.
【０００４】しかし選別したエネルギー範囲には、核燃
料再処理施設の運転中（使用済燃料の剪断・溶解等）に
生じるオフガス中に多量に混在する放射性希ガス（主に
クリプトン-85 ）の広範囲にわたる放射線のエネルギー
（図２の斜線部分）も含まれるため、放射性希ガスも同
時に測定されてしまい、放射性ヨウ素のみの測定ができ
ない。そこで放射性ヨウ素の分布の上下両方又は上下ど
ちらか一方に放射性希ガスのみを測定する範囲を設定
し、放射性ヨウ素の範囲の放射性希ガスの影響を除去す
る方法（比較測定法）が採用されている。[0004] However, the selected energy range covers a wide range of radioactive rare gas (mainly krypton-85) mixed in large amounts in off-gas generated during operation of a nuclear fuel reprocessing facility (such as shearing and melting of spent fuel). Since the energy of the radiation (the hatched portion in FIG. 2) is also included, the radioactive rare gas is also measured at the same time, and it is impossible to measure only radioactive iodine. Therefore, a method (comparative measurement method) in which a range for measuring only the radioactive rare gas is set on both upper and lower sides or one of upper and lower sides of the distribution of radioactive iodine and the influence of the radioactive rare gas in the range of radioactive iodine is adopted. .
【０００５】[0005]
【発明が解決しようとする課題】ところが、核燃料再処
理施設からのオフガスでは、放射性希ガスの量が放射性
ヨウ素に比べて非常に多いため、放射性ヨウ素と放射性
希ガスが同時に測定された測定値と、放射性希ガスのみ
の測定値の比較測定を実施しても、放射性ヨウ素の量を
正確には求められない。また比較測定法では測定時間が
約１時間以上必要となるため、連続測定が不可能であ
る。However, in the offgas from the nuclear fuel reprocessing facility, the amount of radioactive rare gas is much larger than that of radioactive iodine. However, even if the comparative measurement of the measured value of only the radioactive rare gas is performed, the amount of radioactive iodine cannot be accurately obtained. Further, the comparative measurement method requires a measurement time of about 1 hour or more, so that continuous measurement is impossible.
【０００６】そこで、これまで、オフガス中に放射性希
ガスが混在している間の放射性ヨウ素の測定は、一時的
に吸着材へのオフガスの通気を停止し、放射性希ガスを
追い出した後に測定する方法や、連続測定系統を２系統
設置し、前記の方法を交互に繰り返す等の煩雑な方法が
試みられている。しかし、これらの方法では、測定でき
る頻度が少ないばかりでなく、測定の評価法も複雑であ
り、放射性ヨウ素の放射能を連続的に監視しているとは
言えない。また連続測定系統を２系統設置すると、装置
が大型化し、保守も煩雑となる。Therefore, the measurement of radioactive iodine while the radioactive rare gas is mixed in the offgas is performed after the offgas is temporarily stopped flowing through the adsorbent and the radioactive rare gas is expelled. A complicated method such as a method or two continuous measurement systems is set up and the above method is alternately repeated. However, in these methods, not only can the measurement be performed infrequently, but also the method of evaluating the measurement is complicated, and it cannot be said that the radioactivity of radioactive iodine is continuously monitored. In addition, when two continuous measurement systems are installed, the size of the apparatus becomes large and maintenance becomes complicated.
【０００７】本発明の目的は、放射性希ガスの放射線に
よる妨害を排除し、オフガス中に放射性希ガスが混在す
る場合でも吸着材へのオフガスの通気を停止することな
く、また連続測定系統を複数設置する必要もなく、オフ
ガス中の放射性ヨウ素の放射能を自動的に迅速に且つ精
度良く連続測定できる方法を提供することである。SUMMARY OF THE INVENTION An object of the present invention is to eliminate the interference of radioactive rare gas by radiation, to prevent the flow of offgas to the adsorbent even when radioactive rare gas is mixed in the offgas, and to provide a plurality of continuous measurement systems. An object of the present invention is to provide a method capable of automatically, rapidly and accurately measuring the radioactivity of radioactive iodine in off-gas without the need for installation.
【０００８】[0008]
【課題を解決するための手段】本発明は、核燃料関連施
設オフガスの一部を吸着材に連続的に通気させ、該吸着
材に吸着した放射性ヨウ素のエネルギーを、混在する放
射性希ガスのエネルギーと同時に半導体放射線検出器で
測定し、多重波高分析器により放射性ヨウ素のＫαＸ線
又はγ線のエネルギーを弁別し、平滑化処理を施して放
射性希ガスの妨害を除去することにより放射性ヨウ素の
量を連続測定する方法である。半導体放射線検出器とし
ては、Ｇｅ、ＣｄＴｅ、ＨｇＩ2 、ＧａＡｓ等が使用で
きる。According to the present invention, a part of off-gas of a nuclear fuel related facility is continuously passed through an adsorbent, and the energy of radioactive iodine adsorbed on the adsorbent is reduced by the energy of radioactive rare gas mixed therewith. At the same time, it is measured by a semiconductor radiation detector, the energy of radioactive iodine Kα X-rays or γ-rays is discriminated by a multiwave height analyzer, and the amount of radioactive iodine is continuously reduced by performing a smoothing process to remove the interference of radioactive rare gas. It is a method of measuring. Ge, CdTe, HgI 2 , GaAs or the like can be used as the semiconductor radiation detector.
【０００９】[0009]
【作用】半導体放射線検出器は、エネルギー分解能が非
常に優れており、化学分析を必要とせずに多核種の同時
定量ができるため、通常は環境試料中の放射能の定性定
量分析用として使用されている。この半導体放射線検出
器は、特に微弱な放射能の定量、又は未知の放射能の定
性等に効果があるため、これまで核燃料施設のオフガス
中の放射性ヨウ素のような、核種が明確で、しかも放射
能が強い核種の連続モニタに使用された例はない。[Function] Semiconductor radiation detectors have very good energy resolution and can simultaneously quantify multi-nuclides without the need for chemical analysis. Therefore, they are usually used for qualitative and quantitative analysis of radioactivity in environmental samples. ing. Since this semiconductor radiation detector is particularly effective for quantification of weak radioactivity or qualification of unknown radioactivity, nuclides such as radioactive iodine in off-gas of nuclear fuel facilities have been clearly defined and radioactive There is no example used for continuous monitoring of powerful nuclides.
【００１０】しかし、半導体放射線検出器によって核燃
料再処理施設のオフガス中の放射性ヨウ素のエネルギー
を測定すると、エネルギー分解能が極めて良好であると
いう特性のために、得られる放射線の分布が狭くなる。
そこで、放射性ヨウ素について最も放出率の高い放射線
を選んで、放射性ヨウ素のエネルギーと放射性希ガスの
エネルギーを同時に測定し、十分な平滑化処理を加える
スペクトル解析を行うと、短時間（５分間程度）の測定
で放射性希ガスの妨害を除去した結果が得られる。従っ
て、サンプリングを停止することなく、連続した測定・
監視が可能となる。However, when the energy of radioactive iodine in the off-gas of a nuclear fuel reprocessing facility is measured by a semiconductor radiation detector, the obtained radiation distribution becomes narrow due to the characteristic that the energy resolution is extremely good.
Therefore, if the radiation with the highest emission rate is selected for radioactive iodine, the energy of the radioactive iodine and the energy of the radioactive rare gas are measured at the same time, and a sufficient smoothing process is performed to perform a spectrum analysis, it takes a short time (about 5 minutes). The result of removing the interference of the radioactive noble gas is obtained by the measurement. Therefore, without stopping sampling,
Monitoring becomes possible.
【００１１】[0011]
【実施例】図１は、本発明方法を適用したオフガス中放
射性ヨウ素の連続測定装置の一実施例を示す概略説明図
である。この装置は、核燃料関連施設からのオフガス配
管１０に対して、入口管１２と出口管１４とによって並
列的に設置される。オフガスの一部が該入口管１２から
入り、ヨウ素吸着材１６を通って出口管１４から出て、
オフガス配管１０で合流する構成である。ヨウ素吸着材
１６は活性炭等からなり、それに対向するようにＧｅ等
の半導体放射線検出器１８を設置する。半導体放射線検
出器１８としては、Ｇｅ以外にもＣｄＴｅ、ＨｇＩ2 、
ＧａＡｓ等が使用可能である。該半導体放射線検出器１
８の上部には、それを冷却するための冷却機２０を設け
る。ヨウ素吸着材１６と半導体放射線検出器１８の外側
はケーシング２２で覆う。半導体放射線検出器１８から
の電気的出力は、増幅器３０で増幅し、多重波高分析器
３２及びパーソナルコンピュータ３４でデータの処理を
行う。FIG. 1 is a schematic explanatory view showing one embodiment of a continuous measuring apparatus for radioactive iodine in off-gas to which the method of the present invention is applied. This device is installed in parallel with an off-gas pipe 10 from a nuclear fuel-related facility by an inlet pipe 12 and an outlet pipe 14. A portion of the off-gas enters through the inlet tube 12, exits the outlet tube 14 through the iodine adsorbent 16,
The configuration is such that the merging occurs at the off-gas pipe 10. The iodine adsorbent 16 is made of activated carbon or the like, and a semiconductor radiation detector 18 of Ge or the like is provided so as to face the activated carbon. As the semiconductor radiation detector 18, in addition to Ge, CdTe, HgI 2 ,
GaAs or the like can be used. The semiconductor radiation detector 1
At the upper part of 8, a cooler 20 for cooling it is provided. The outside of the iodine adsorbent 16 and the semiconductor radiation detector 18 is covered with a casing 22. The electrical output from the semiconductor radiation detector 18 is amplified by the amplifier 30 and processed by the multiplex height analyzer 32 and the personal computer 34.
【００１２】オフガス配管１０を通る核燃料関連施設か
らのオフガスの一部が、入口管１２から導入され、ヨウ
素吸着材１６に連続的に通気することで、放射性ヨウ素
をヨウ素吸着材１６に吸着させ、半導体放射線検出器１
８でヨウ素吸着材１６の放射性ヨウ素の放射線のエネル
ギーを測定する。この時、オフガス中に存在する放射性
希ガスのエネルギーも同時に測定される。半導体放射線
検出器１８で測定された信号は、信号ライン２８を通じ
て増幅器３０に送られて増幅される。増幅した信号は、
多重波高分析器３２により放射性ヨウ素のＫαＸ線又は
γ線（いずれか放出率の高い方）のエネルギーを弁別
し、パーソナルコンピュータ３４で平滑化処理を施す。
これによって放射性希ガスの妨害が除去され、放射性ヨ
ウ素のみのデータが取り出される。取り出した信号を放
射能に換算し、表示部に放射能の変化をグラフとして表
示するとともに、放射能をプリンタに出力する。A part of the off-gas from the nuclear fuel-related facility passing through the off-gas pipe 10 is introduced from the inlet pipe 12 and is continuously ventilated through the iodine adsorbent 16 so that radioactive iodine is adsorbed on the iodine adsorbent 16. Semiconductor radiation detector 1
At 8, the radiation energy of the radioactive iodine of the iodine adsorbent 16 is measured. At this time, the energy of the radioactive rare gas present in the off gas is also measured at the same time. The signal measured by the semiconductor radiation detector 18 is sent to an amplifier 30 via a signal line 28 and amplified. The amplified signal
The multi-wave height analyzer 32 discriminates the energy of radioactive iodine from Kα X-rays or γ-rays (whichever has a higher emission rate), and a personal computer 34 performs a smoothing process.
As a result, the interference of the radioactive rare gas is removed, and data of radioactive iodine alone is obtained. The extracted signal is converted into radioactivity, the change in radioactivity is displayed as a graph on a display unit, and the radioactivity is output to a printer.
【００１３】半導体放射線検出器（Ｇｅ）を使用して放
射性ヨウ素（ヨウ素-129）を測定した場合には、図３に
示すような結果が得られる。ＮａＩシンチレーション検
出器による測定結果の図２と比較すると、半導体放射線
検出器は格段にエネルギー分解能が良いことが分かる。
このため放射性希ガスの影響が少なく（放射線の分布が
狭い）、また放出率の高い放射線を選択することで、測
定時間を短縮できることになる。When radioactive iodine (iodine-129) is measured using a semiconductor radiation detector (Ge), the results shown in FIG. 3 are obtained. Comparing FIG. 2 of the measurement results with the NaI scintillation detector, it can be seen that the semiconductor radiation detector has much better energy resolution.
For this reason, the measurement time can be shortened by selecting the radiation which has little influence of the radioactive rare gas (the distribution of radiation is narrow) and has a high emission rate.
【００１４】本発明における平滑化処理の一例を図４に
より説明する。ここでは多重波高分析器によってエネル
ギー弁別した各チャンネルのエネルギーについて、近接
するエネルギーを用いて荷重平均する方法を採用してい
る。基礎的試験によれば、前後それぞれ５チャンネルに
ついてガウス関数の係数で重み付けし、それを２回繰り
返す処理が最適であった。つまり図４において、Ｃ0 チ
ャンネルの場合は、前５チャンネル（Ｃ-5〜Ｃ-1）と後
５チャンネル（Ｃ1 〜Ｃ5 ）を用いて荷重平均するので
ある。なお実際には、半導体放射線検出器の種類等によ
り、荷重平均の荷重度や回数などは適宜最適となるよう
に設定する。An example of the smoothing process according to the present invention will be described with reference to FIG. Here, a method is employed in which the energy of each channel, which has been subjected to energy discrimination by the multi-wave height analyzer, is weighted using nearby energy. According to the basic test, it was optimal to perform weighting for each of the five channels before and after with the coefficient of the Gaussian function and repeat the process twice. That is, in FIG. 4, in the case of C 0 channel is to average load using 5 channels after the previous five channels (C -5 ~C -1) (C 1 ~C 5). Actually, depending on the type of the semiconductor radiation detector, the load level and the number of times of the load average are appropriately set to be optimal.
【００１５】ところで、放射性ヨウ素のうちヨウ素-129
については上記のようにＫαＸ線が最も放出率が高い
が、ヨウ素-131についてはγ線が最も放出率が高い。よ
って測定する核種に応じて放出率の高い放射線を選ぶの
が好ましい。By the way, of radioactive iodine, iodine-129
As described above, Kα X-ray has the highest emission rate as described above, whereas, for iodine-131, γ-ray has the highest emission rate. Therefore, it is preferable to select radiation having a high emission rate according to the nuclide to be measured.
【００１６】[0016]
【発明の効果】本発明は上記のように、半導体放射線検
出器を使用して放射性ヨウ素のエネルギーを、混在する
放射性希ガスのエネルギーと同時に測定し、十分な平滑
化処理を加えてスペクトル解析する方法であるので、オ
フガス中の放射性ヨウ素を、混在する放射性希ガスの妨
害を排除して測定できる。従って本発明方法では、サン
プリングを停止することが無く、また短時間で（５分間
程度）且つ一つのサンプリング系列で連続測定が可能で
ある。更に評価を自動化できるため、監視労力を省力化
できる。As described above, according to the present invention, the energy of radioactive iodine is measured simultaneously with the energy of mixed radioactive rare gas using a semiconductor radiation detector, and the spectrum is analyzed by applying a sufficient smoothing process. Since it is a method, radioactive iodine in off-gas can be measured without interference of radioactive rare gas mixed therein. Therefore, according to the method of the present invention, continuous measurement can be performed in a short time (about 5 minutes) and with one sampling sequence without stopping sampling. Further, since the evaluation can be automated, the labor for monitoring can be saved.
【００１７】この連続監視方法により、オフガス中の放
射性ヨウ素の量の監視の精度・確実性が向上し、施設の
安全性が向上する。そして施設の安全性の向上により、
公衆の被曝の可能性をより一層低減できる。According to this continuous monitoring method, the accuracy and reliability of monitoring the amount of radioactive iodine in the off-gas is improved, and the safety of the facility is improved. And by improving facility safety,
The possibility of public exposure can be further reduced.
【図１】本発明による放射性ヨウ素の連続測定装置の一
実施例を示す概略構成図。FIG. 1 is a schematic configuration diagram showing an embodiment of a continuous measurement apparatus for radioactive iodine according to the present invention.
【図２】ＮａＩ放射線検出器で測定した放射性ヨウ素の
エネルギーの説明図。FIG. 2 is an explanatory diagram of energy of radioactive iodine measured by a NaI radiation detector.
【図３】半導体放射線検出器で測定した放射性ヨウ素の
エネルギーの説明図。FIG. 3 is an explanatory diagram of the energy of radioactive iodine measured by a semiconductor radiation detector.
【図４】本発明における平滑化処理の説明図。FIG. 4 is an explanatory diagram of a smoothing process according to the present invention.
１０ オフガス配管 １２ 入口管 １４ 出口管 １６ ヨウ素吸着材 １８ 半導体放射線検出器 ２０ 冷却機 DESCRIPTION OF SYMBOLS 10 Off gas pipe 12 Inlet pipe 14 Outlet pipe 16 Iodine adsorbent 18 Semiconductor radiation detector 20 Cooler
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭62−287177（ＪＰ，Ａ) 特開 昭58−176568（ＪＰ，Ａ) 特開 平２−163688（ＪＰ，Ａ) 特開 平５−180942（ＪＰ，Ａ) 特開 昭63−173986（ＪＰ，Ａ) 特開 平４−174565（ＪＰ，Ａ) (58)調査した分野(Int.Cl.6，ＤＢ名) G01T 1/167 G01T 1/36 G21F 9/02 511 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-287177 (JP, A) JP-A-58-176568 (JP, A) JP-A-2-163688 (JP, A) JP-A-5-176688 180942 (JP, A) JP-A-63-173986 (JP, A) JP-A-4-174565 (JP, A) (58) Fields investigated (Int. Cl. 6 , DB name) G01T 1/167 G01T 1 / 36 G21F 9/02 511
Claims (1)
吸着材に連続的に通気させ、該吸着材に吸着した放射性
ヨウ素のエネルギーを、混在する放射性希ガスのエネル
ギーと同時に半導体放射線検出器で測定し、多重波高分
析器により放射性ヨウ素のＫαＸ線又はγ線のエネルギ
ーを弁別し、平滑化処理を施して放射性希ガスの妨害を
除去することにより放射性ヨウ素の量を測定するオフガ
ス中放射性ヨウ素の連続測定方法。1. A part of off-gas from a nuclear fuel-related facility is continuously passed through an adsorbent, and the energy of radioactive iodine adsorbed on the adsorbent is converted by a semiconductor radiation detector simultaneously with the energy of mixed radioactive rare gas. Measure and determine the energy of radioactive iodine in the offgas by measuring the energy of radioactive iodine by discriminating the energy of Kα X-rays or γ-rays of radioactive iodine by a multi-wave height analyzer and performing a smoothing treatment to remove the interference of the radioactive rare gas. Continuous measurement method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30868793A JP2931750B2 (en) | 1993-11-15 | 1993-11-15 | Continuous measurement method of radioactive iodine in off-gas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30868793A JP2931750B2 (en) | 1993-11-15 | 1993-11-15 | Continuous measurement method of radioactive iodine in off-gas |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07140251A JPH07140251A (en) | 1995-06-02 |
| JP2931750B2 true JP2931750B2 (en) | 1999-08-09 |
Family
ID=17984081
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP30868793A Expired - Fee Related JP2931750B2 (en) | 1993-11-15 | 1993-11-15 | Continuous measurement method of radioactive iodine in off-gas |
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| Country | Link |
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| JP (1) | JP2931750B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2314619B (en) * | 1996-06-29 | 2000-10-18 | Martin John Oliver | Radioactive iodine monitor |
| JP5999473B2 (en) * | 2012-03-14 | 2016-09-28 | 国立大学法人名古屋大学 | Collection unit, detector for radioactive gas monitor, and radioactive gas monitor |
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1993
- 1993-11-15 JP JP30868793A patent/JP2931750B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07140251A (en) | 1995-06-02 |
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