JP2602301B2 - Correction method of photoneutron in boric acid concentration measuring instrument - Google Patents
Correction method of photoneutron in boric acid concentration measuring instrumentInfo
- Publication number
- JP2602301B2 JP2602301B2 JP63249935A JP24993588A JP2602301B2 JP 2602301 B2 JP2602301 B2 JP 2602301B2 JP 63249935 A JP63249935 A JP 63249935A JP 24993588 A JP24993588 A JP 24993588A JP 2602301 B2 JP2602301 B2 JP 2602301B2
- Authority
- JP
- Japan
- Prior art keywords
- boric acid
- heavy water
- photoneutron
- acid concentration
- concentration measuring
- 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
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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- Monitoring And Testing Of Nuclear Reactors (AREA)
- Measurement Of Radiation (AREA)
Description
【発明の詳細な説明】 （産業上の利用分野） 重水炉において減速材として使用される重水には中性
子吸収のため、ほう酸（10B）が含まれている。そして
重水中のほう酸濃度を変えることによって、重水炉にお
ける反応度が制御される。従って、重水中のほう酸の濃
度測定は極めて重要である。The heavy water is used as moderator in BACKGROUND OF THE INVENTION (FIELD OF THE INVENTION) heavy-water reactors for neutron absorption contains boric acid (10 B) is. The reactivity in the heavy water reactor is controlled by changing the concentration of boric acid in the heavy water. Therefore, measuring the concentration of boric acid in heavy water is extremely important.
本発明はこのような重水中のほう酸濃度測定器におけ
る光中性子補正方法に関するものである。The present invention relates to a photoneutron correction method for such a boric acid concentration measuring instrument in heavy water.
（従来技術） 第２図を参照してほう酸濃度測定器について概略説明
する。第２図に於て１は測定容器、２は測定容器１の外
部を囲む反射兼遮蔽体である。３は重水入口、４は中性
子計測器、５は中性子線源である。この線源５からの中
性子は前記反射兼遮蔽体によって反射される。反射体兼
遮蔽体は中性子を容器内に封じ込めて外部漏洩を防止す
ると同時に中性子を外部に逃さないで効率的に利用する
ようになっている。(Prior Art) A boric acid concentration measuring device will be schematically described with reference to FIG. In FIG. 2, reference numeral 1 denotes a measuring container, and 2 denotes a reflection / shielding body surrounding the outside of the measuring container 1. 3 is a heavy water inlet, 4 is a neutron detector, and 5 is a neutron source. Neutrons from the source 5 are reflected by the reflector / shield. The reflector / shielder is designed to confine neutrons in a container to prevent external leakage and at the same time to efficiently utilize neutrons without escaping to the outside.
そして、重水入口３からほう酸を含んだ重水を測定容
器１内に送り込み、容器頂部から中性子を照射する。中
性子は重水によって減速され、10Bに吸収されない中性
子を中性子計測器４で検出するようになっている。Then, heavy water containing boric acid is fed into the measurement container 1 from the heavy water inlet 3, and neutrons are irradiated from the top of the container. Neutrons are decelerated by heavy water, and neutrons that are not absorbed by 10 B are detected by the neutron measuring device 4.
光中性子の影響を除く方法としては、Cdフイルタ付き
の計数管を用いる方法がある。Cdフイルタ付きの計算管
を用いると10B濃度に依存せず、元来の中性子線源（252
Cf等）と光中性子源との割合を求めることが出来る。As a method for eliminating the influence of photoneutrons, there is a method using a counter tube with a Cd filter. Using computation tube with Cd filter if not dependent on the 10 B concentration, original neutron source (252
Cf) and the ratio of the photoneutron source.
但し、この割合を求めるためには、１）光中性子の無
い状態での検出器出力を求めておく必要がある、２）ま
た、Cdフイルタ付きの計数管の検出器出力を通常の（Cd
フイルタ無し）計数管の検出器出力に換算する必要があ
る。However, in order to obtain this ratio, 1) it is necessary to obtain the detector output in the absence of photoneutrons. 2) Also, the detector output of a counter tube with a Cd filter is converted to a normal (Cd
It is necessary to convert to the detector output of the counter tube.
（発明が解決しようとする課題） 重水中の10B濃度のオンライン測定のため、中性子源
から出た中性子が重水で減速され、減速された中性子が
10Bに吸収されることを利用した測定器を開発するに当
り、重水中には放射性不純物があるが、この内24Na,56M
nからのγ線の一部は重水と反応して光中性子を生成す
る。この光中性子は10B濃度測定に於て誤差要因となる
ので、この光中性子の影響を補正する方法を提供しよう
とするものである。(Problems to be solved by the invention) For online measurement of 10 B concentration in heavy water, neutrons emitted from a neutron source are slowed down by heavy water, and the slowed-down neutrons
In developing a measuring device that utilizes absorption by 10 B, heavy water contains radioactive impurities, of which 24 Na, 56 M
Some of the gamma rays from n react with heavy water to produce photoneutrons. Since this photoneutron causes an error in the measurement of the 10 B concentration, an attempt is made to provide a method for correcting the influence of the photoneutron.
（発明による課題の解決手段） ほう酸濃度測定器は通液するほう酸を含んだ重水を静
止させる機能を有し、重水の流れが静止した後、ある時
間経過後の検出器出力を時刻を変えて複数回計測し、該
計測したデータを用いてバルブを閉じた直後の時刻toの
中性子線源とγ核種との寄与分を計算により求め、こゝ
で求めた値によって光中性子分を補正することを特徴と
する。(Means for Solving the Problems According to the Invention) A boric acid concentration measuring device has a function of stopping heavy water containing boric acid to pass through, and after the flow of heavy water has stopped, changing the time of the detector output after a certain time has elapsed. Measuring a plurality of times, calculating the contribution between the neutron source and the γ nuclide at time to immediately after closing the valve using the measured data, and correcting the photoneutron component by the value obtained here. It is characterized by.
又通常計測時において、Cdフイルタ付きの計数管によ
る方法を併用して重水の流れを静止させずに連続計測可
能とした。At the time of normal measurement, continuous measurement was possible without stopping the flow of heavy water by using a method using a counter tube with a Cd filter.
（実施例） 第２図を参照してほう酸濃度測定器における測定容器
１内における中性子の態様について説明する。(Example) With reference to FIG. 2, the mode of the neutron in the measuring container 1 in the boric acid concentration measuring device will be described.
中性子線源５の252Cfから中性子が放射される。これ
ら中性子は、測定容器１内の重水Ｄによって減速された
中性子と減速されない中性子とが混在している。又重水
Ｄで減速された中性子のうちには、さらに重水中のほう
酸10Bに吸収される中性子nBがある。従って、中性子線
源５から放射される中性子の総量のうち、計測器４にて
計測される量は重水Ｄであまり減速されないで計測器４
に達する中性子ｎと重水Ｄで減速されて計測器４に達す
る中性子nDの和（ｎ＋nD）となる。Neutrons are emitted from 252 Cf of the neutron source 5. These neutrons include neutrons slowed down by the heavy water D in the measurement container 1 and neutrons not slowed down. Also while the neutrons is reduced at heavy water D may neutrons n B which is further absorbed in the heavy water of boric acid 10 B. Therefore, of the total amount of neutrons emitted from the neutron source 5, the amount measured by the measuring device 4 is not decelerated by the heavy water D so much that the measuring device 4
It is reduced at the neutron n and heavy water D reaching to reach the measuring instrument 4 the sum of neutrons n D (n + n D).
一方、重水中には不純物である24Na,56Mnが存在する
が、これら24Naや56Mnから発生する高エネルギーγ線の
一部は重水Ｄと反応して光中性子nPを発生する。On the other hand, the heavy water is present 24 Na, 56 Mn is an impurity, part of a high-energy γ-rays generated from these 24 Na and 56 Mn generates light neutrons n P reacts with heavy water D.
したがって、計測器４では重水Ｄに減速された中性子
のうち10Bに吸収されなかった中性子nDと、あまり減速
されない中性子ｎ及び光中性子nPの３種の中性子ｎ＋nD
＋nPが計測されることになる。Therefore, the neutron n D which was not absorbed by 10 B among the neutrons decelerated by the heavy water D and the neutron n + n D which was not decelerated by the neutron n and the photoneutron n P were measured by the measuring device 4.
+ N P will be measured.
計測器４で計測される光中性子nPは252Cfからの中性
子でなく、発生源を異にしているので、計測器４での測
定値の誤差となる中性子である。The optical neutron n P measured by the measuring device 4 is not a neutron from 252 Cf but a neutron that causes an error in the measured value of the measuring device 4 because the source is different.
本発明方法は、第２図に示すほう酸濃度測定容器１内
の核種毎の半減期の差により核種による計数率を識別
し、これを補正に用いものである。In the method of the present invention, the counting rate of each nuclide is identified based on the difference in half-life of each nuclide in the boric acid concentration measuring vessel 1 shown in FIG. 2, and this is used for correction.
第１図で、ほう酸を含んだ重水（これ以外にも光中性
子源となるγ核種が含まれたものであるが）通常通水さ
れているラインに、バルブ6aと6bを設けておき、ある時
刻toで通水を止める。この時刻toを開始時点として、あ
る時間間隔△ｔごとに計数管出力Ｃ（ti）を測定してい
く。こゝで ti＝to＋△ｔ×ｉ（ｉ＝1,2,…,n）とする。In FIG. 1, valves 6a and 6b are provided in a line through which heavy water containing boric acid (which also contains a gamma nuclide serving as a photoneutron source) is normally passed. Stop water flow at time to. With the time to as a start time, the counter tube output C (ti) is measured at certain time intervals Δt. Here, ti = to + △ t × i (i = 1, 2,..., N).
tiに対応したＣ（ti）をプロットすれば、第３図の様
になる。このＣ（ti）は、元来の中性子線源（252Cf
等）と光中性子源とのそれぞれの寄与分の和で示される
ため、通水を止めた後に光中性子源の減衰割合分だけ減
少を示すことになる。この時、元来の中性子線源も時間
と共に減衰するが、例えば252Cfの場合、半減期2,645年
と長く、γ核種の半減期16N;7.35秒,24Na;15時間,56Mn;
2.6時間等と比較して差異があるので、減衰の割合の相
違を利用して核種による計数率を識別することが可能で
ある。If C (ti) corresponding to ti is plotted, the result is as shown in FIG. This C (ti) is equivalent to the original neutron source ( 252 Cf
Etc.) and the contribution of each of the photoneutron sources, so that after the water flow is stopped, the decrease is shown by the attenuation rate of the photoneutron sources. At this time, the original neutron source also attenuates with time, but, for example, in the case of 252 Cf, the half-life is as long as 2,645 years, and the half-life of the γ-nuclide is 16 N; 7.35 seconds, 24 Na; 15 hours, 56 Mn;
Since there is a difference as compared with 2.6 hours, etc., it is possible to identify the counting rate by nuclide using the difference in the rate of attenuation.
たとえばほう酸濃度測定器が炉心から４分間後の地点
に設置されているとすれば、16Nは1.4×10-10倍に減衰
してしまう。この場合には、24Naと56Mnとを対象とすれ
ばよいことが分かる。For example, if a boric acid concentration measuring device is installed at a point four minutes after the core, 16 N will attenuate 1.4 × 10 -10 times. In this case, it can be seen that 24 Na and 56 Mn may be targeted.
各々の核種に対応させた時刻tiでの全計数率Iiは、 で表わされる。ここで、 Io（Cf）：バルブ閉直後（時刻to）での252Cfによる計
数率 Io（Mn）：バルブ閉直後（時刻to）での56Mnによる計数
率 Io（Na）：バルブ閉直後（時刻to）での24Naによる計数
率 τcf:252Cfの半減期 τMn:56Mnの半減期 τNa:24Naの半減期 上式を変形すると、 となる。The total count rate Ii at time ti corresponding to each nuclide is Is represented by Here, Io (Cf): count rate by 252 Cf immediately after valve closing (time to) Io (Mn): count rate by 56 Mn immediately after valve closing (time to) Io (Na): immediately after valve closing ( Counting by 24 Na at time to) τ cf : half-life of 252 Cf τ Mn : half-life of 56 Mn τ Na : half-life of 24 Na Becomes
ここで、 λcf:252Cfの崩壊定数4.986×10-7（min-1） λMn:56Mnの崩壊定数4.448×10-3（min-1） λNa:24Naの崩壊定数7.691×10-4（min-1） これから、Io（Cf）,Io（Mn）,Io（Na）を求めるために
は、各tiに対するIiを測定しておいて、一般的には重回
帰分析として知られる方法を適用すればよい。Here, λ cf : decay constant of 252 Cf 4.986 × 10 -7 (min -1 ) λ Mn : decay constant of 56 Mn 4.448 × 10 -3 (min -1 ) λ Na : decay constant of 24 Na 7.691 × 10 -4 (min -1 ) From now on, to find Io (Cf), Io (Mn), Io (Na), measure Ii for each ti, and it is generally known as multiple regression analysis Apply the method.
このようにして、各々の核種に対する計数率の寄与の
割合を求めることが出来たので、これをもとにして、Io
（Cf）の値を補正することが出来る。すなわち、１）別
のところで光中性子の無い状態での検出器出力（Io（C
f）に相当する）を求めておかなくても、この方法によ
り求めることができ、補正を行なうことができる。２）
Cdフィルタ付きの計数管の値を用いた換算が正しいかど
うかを、上記に述べた本方法により確認することができ
る。In this way, the ratio of the contribution of the counting rate to each nuclide was determined, and based on this, Io
The value of (Cf) can be corrected. That is, 1) Detector output (Io (C
Even if f) is not determined, it can be determined by this method and correction can be performed. 2)
Whether the conversion using the value of the counter tube with the Cd filter is correct can be confirmed by the above-described method.
（作用） 本発明は、以上のような構成であり、通常計測時に
は、ほう酸濃度測定器の中のサンプル液（ほう酸を含む
重水）は絶えず循環通水されている。そして光中性子の
補正を行なおうとする時においてのみサンプル液の通水
を停止し、サンプル液を静止させて、時刻と共に検出器
出力（計数率）を測定する。この両者から元来の中性子
線源とγ核種による光中性子寄与分を識別分離するのは
前項に示した通りである。(Operation) The present invention is configured as described above, and at the time of normal measurement, the sample liquid (heavy water containing boric acid) in the boric acid concentration measuring device is constantly circulated and passed. Then, only when the correction of the photoneutrons is to be performed, the flow of the sample liquid is stopped, the sample liquid is stopped, and the detector output (count rate) is measured with time. As described in the previous section, the original neutron source and the photoneutron contribution by the γ nuclide are discriminated and separated from both.
本発明による方法においては、光中性子の補正を行な
おうとする場合には、必がサンプル液を一度静止させる
必要がある。これは連続測定が不可能になることを意味
することであるが、通常計測時においては例えばCdフイ
ルタ付きの計数管を用いる方法を併用してサンプル液は
連続通水しておき、厳密な補正を要する時（または測定
器の較正時）においてのみ本方法に示す様にサンプル液
の静止をすれば、連続測定も可能となる。In the method according to the present invention, in order to correct photoneutrons, it is necessary to stop the sample liquid once. This means that continuous measurement becomes impossible, but at the time of normal measurement, for example, the sample solution is continuously passed through using a method using a counter tube with a Cd filter, and strict correction is performed. When the sample solution is stopped as shown in the present method only when the measurement is required (or when the measuring device is calibrated), continuous measurement is also possible.
（効果） １）本発明によれば、元来の中性子線源と光中性子源と
の合計の計数率の時間変化を測定するだけでよく、光中
性子の無い状態での検出器出力を求めておく必要はなく
なった。(Effects) 1) According to the present invention, it is only necessary to measure the time change of the total counting rate of the original neutron source and the photoneutron source, and to obtain the detector output in the absence of photoneutrons. No need to keep it.
２）元来の中性子線源と光中性子源との割合変化の激し
い場合においては、Cdフイルタ付きの計数管と併用する
ことで連続計測は可能である。また、この場合の換算が
正しいかどうかの較正を本発明により行なうことが出来
る。2) In cases where the ratio between the original neutron source and the photoneutron source changes drastically, continuous measurement is possible by using the counter with a Cd filter. In addition, the present invention can calibrate whether the conversion in this case is correct.
３）元来の中性子線源と光中性子源との割合変化が少な
い場合には、Cdフイルタ付きの計数管を設けることな
く、本発明の方法だけで光中性子の影響を補正すること
ができる。3) When the ratio change between the original neutron source and the photoneutron source is small, the effect of the photoneutron can be corrected only by the method of the present invention without providing a counter tube with a Cd filter.
第１図は本発明方法の説明図。 第２図はほう酸濃度測定器を示す。 第３図は検出器出力の時間変化を示すグラフ。 図において； １……測定容器、２……反射兼遮蔽体 ３……重水入口、４……中性子計測器 ５……中性子線源 6a,6b……（重水の通液を静止させる）バルブ FIG. 1 is an explanatory view of the method of the present invention. FIG. 2 shows a boric acid concentration measuring instrument. FIG. 3 is a graph showing a time change of a detector output. In the figure: 1 ... measurement vessel, 2 ... reflection / shielding body 3 ... heavy water inlet, 4 ... neutron measuring instrument 5 ... neutron radiation sources 6a, 6b ...
Claims (2)
だ重水を静止させる機能を有し、重水の流れが静止した
後、ある時間経過後の検出器出力を時刻を変えて複数回
計測し、該計測したデータを用いてバルブを閉じた直後
の時刻toの中性子線源とγ核種との寄与分を計算により
求め、こゝで求めた値によって光中性子分を補正するこ
とを特徴とするほう酸濃度測定器に於ける光中性子の補
正方法。1. A boric acid concentration measuring device has a function of stopping heavy water containing boric acid passing therethrough. After the flow of heavy water has stopped, a detector output after a certain period of time is measured a plurality of times at different times. Then, the contribution of the neutron source and the γ-nuclide at time to immediately after closing the valve using the measured data is obtained by calculation, and the photoneutron component is corrected by the value obtained here. Correction method for photoneutrons in a boric acid concentration measuring instrument.
数管による方法を併用して重水の流れを静止させずに連
続計測可能としたことを特徴とする請求項１）記載のほ
う酸濃度測定器に於ける光中性子の補正方法。2. The boric acid concentration measuring device according to claim 1, wherein during normal measurement, continuous measurement can be performed without stopping the flow of heavy water by using a method using a counter tube with a Cd filter. Correction method for photoneutrons in the field.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63249935A JP2602301B2 (en) | 1988-10-05 | 1988-10-05 | Correction method of photoneutron in boric acid concentration measuring instrument |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63249935A JP2602301B2 (en) | 1988-10-05 | 1988-10-05 | Correction method of photoneutron in boric acid concentration measuring instrument |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0298693A JPH0298693A (en) | 1990-04-11 |
| JP2602301B2 true JP2602301B2 (en) | 1997-04-23 |
Family
ID=17200362
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63249935A Expired - Lifetime JP2602301B2 (en) | 1988-10-05 | 1988-10-05 | Correction method of photoneutron in boric acid concentration measuring instrument |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2602301B2 (en) |
-
1988
- 1988-10-05 JP JP63249935A patent/JP2602301B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0298693A (en) | 1990-04-11 |
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