JP3626519B2 - Substoichiometric or stoichiometric nitrate solution preparation method - Google Patents
Substoichiometric or stoichiometric nitrate solution preparation method Download PDFInfo
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- JP3626519B2 JP3626519B2 JP29014894A JP29014894A JP3626519B2 JP 3626519 B2 JP3626519 B2 JP 3626519B2 JP 29014894 A JP29014894 A JP 29014894A JP 29014894 A JP29014894 A JP 29014894A JP 3626519 B2 JP3626519 B2 JP 3626519B2
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- stoichiometric
- nitric acid
- substoichiometric
- metal
- nitrate solution
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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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Description
【０００１】
【産業上の利用分野】
本発明は原子炉用セラミックス燃料粒子等の微小球状セラミックス粒子を調製する場合の出発物質として使用される核燃料物質等の亜化学量論的または化学量論的硝酸塩溶液の調製方法に関するものである。
【０００２】
【従来の技術】
原子炉用セラミックス燃料粒子の分野において利用されているゾルゲル法による燃料ゲル粒子の製造工程では、出発物質溶液であるウラン等の燃料金属を含む亜化学量論的硝酸塩溶液を調製する場合、金属酸化物粉末を硝酸または化学量論的金属硝酸塩溶液に溶解するか、あるいは化学量論的硝酸塩溶液に有機物還元剤を加えて硝酸を分解・除去する方法を採っている。
【０００３】
【発明が解決しようとする課題】
本発明の目的は、従来技術では不可欠の、作業員被曝の増大をもたらす放射性物質である燃料酸化物微粉末の取扱工程、あるいは有機物還元剤を酸化剤である硝酸塩溶液に添加する危険を伴う工程を経ずに、目的の出発物質溶液を調製する方法を提供することにある。
【０００４】
【課題を解決するための手段とその作用】
本願発明者が鋭意研究の結果、目的とする課題解決のために採用した手段は次のとおりである。
【０００５】
第１は、水蒸気を含む雰囲気中での加熱により、脱硝酸効率を高めたほか、放出ガスの主成分を窒素酸化物よりも硝酸の形にでき、目的の脱硝酸反応の終点を次のようにして正確に自動制御できるようにしたことである。すなわち、図１に例を示すような装置を用いて、担体ガス１をヒータ２で加熱した水３の中に導き水蒸気を含ませ、保温炉４を通して、ヒータ５で加熱した硝酸塩容器６内に導く。これにより放出した硝酸を担体ガスと共に冷却水を流していない冷却器７、続いて冷却水を流している冷却器８を通して硝酸捕集用アルカリ溶液９の中に導く。この溶液中の当初のアルカリ量は放出させるべき硝酸と当量としておく。このアルカリ溶液のｐＨをｐＨメータ１０につないだ記録調節計１１で連続モニターしつつ、放出硝酸とアルカリ溶液との中和反応の終点での急激なｐＨ変化の信号により、ヒータ５による加熱を停止させると同時に、発生硝酸の系外放出を停止させるために冷却器７にも冷却水１２を流すための電磁切換弁１３の操作を行う。
【０００６】
第２は、反応終了後の容器６中の溶融塩状の被加熱物を室温まで冷却し固化させると、その固体の吸湿による体積膨張により容器破損が生ずるので、それを防ぐために水の沸点である１００℃以下の高温に維持した状態で手動弁１４を開き、水溜１５の中水を加えて固体を水溶液に変えた後で冷却することである。
【０００７】
【実施例】
実施例について本発明を具体的に説明する。ただし、本発明は実施例によって限定されるものではない。
【０００８】
【実施例１】
図１の装置の試料（硝酸ウラニル溶液）の加熱ヒータとして油浴を用い、水蒸気発生器の９５℃の水の中にアルゴンを５０ｍ１／分の速度でバブルさせた（水蒸気＋アルゴン）混合ガスを試料に供給、放出硝酸捕集用炭酸ナトリウム溶液を時々交換しながら放出硝酸量を調べる方法で、試料中のＮＯ３ −／Ｕモル比の経時変化を調べた。反応前の試料は、Ｕ濃度が２．００ｍｏ１／１でＮＯ３ −／Ｕモル比が２．１０である遊離硝酸含有硝酸ウラニル溶液６０ｍ１である。
【０００９】
設定温度１６０℃の油浴の加熱開始後約８０分で試料温度が約１１０℃になり硝酸の放出が始まり４３０分までの加熱の結果、ＮＯ３ −／Ｕモル比は１．８６に達した。（捕集硝酸からの計算値は１．８３で誤差の範囲で一致していた）。試料温度は２９０分以降１４７℃であった。この間の試料温度と捕集硝酸から計算した試料のＮＯ３ −／Ｕモル比とを、加熱開始後の時間に対して図２に示している。（図２には、アルゴンガスのみを供給した場合の結果も比較して示している。）
【００１０】
【実施例２】
実施例１と同様の手法で、油浴設定温度のみを１９５℃に変えて、ＮＯ３ −／Ｕモル比の経時変化を調べた。加熱開始後２０６分後に、ＮＯ３ −／Ｕモル比は１．６３に達した。（捕集硝酸からの計算値は１．６５で誤差の範囲で一致していた）。試料温度は１３０分以降１８０℃であった。この間の試料温度と捕集硝酸から計算した試料のＮＯ３ −／Ｕモル比とを、加熱開始後の時間に対して図３に示している。（図３には、アルゴンガスのみを供給した場合の結果も比較して示している。）
【００１１】
【実施例３】
図１に示す装置を用いて、実施例２と同様の加熱前試料、加熱条件を適用し、ＮＯ３ −／Ｕモル比の目標値を１．５５として実験した。具体的には、放出硝酸捕集用アルカリ溶液には試料のＮＯ３ −／Ｕモル比の最終値が１．５５に達するまでの放出硝酸と当量の炭酸ナトリウムを含ませておき、その溶液のｐＨが４に達した時に、試料加熱ヒータ５の電源断と冷却器７へ冷却水を供給する電磁切換弁１３作動の信号を出すように設定しておいた。
【００１２】
試料温度は１６０分以降１８４℃であった。２５２分後にｐＨが設定値以下となり、前記信号を発した。加熱終了後に試料温度が８０℃になった時に手動弁１４を開いて所定の水を水溜１５から試料容器内に供給した。内部の固体をすべて溶解するために最終的には９５℃に加熱した。この試料溶液のＮＯ３ −／Ｕモル比は、目標値と誤差の範囲で一致する１．５７であった。
【００１３】
【発明の効果】
従来の技術では、作業員被曝程度の増大を招く放射性微粉末を取り扱う工程、あるいは危険度の高い還元反応工程が必要であった。しかし、本発明の結果、これらの工程を不要としたほか、脱硝酸量が目標どおり制御可能で、かつ、自動化の可能な亜化学量論的または化学量論的硝酸塩溶液の調製方法を実現させた。また、脱硝酸反応を水蒸気中で行うことにより、図２及び３に比較して示すように熱分解によるものより高い効率で進める方法を実現させた。
【図面の簡単な説明】
【図１】本発明の方法を実施するための装置の一例を示した図である。
【図２】試料加熱ヒータとして１６０℃油浴を用いた実施例１の場合の試料温度と試料中のＮＯ３ −／Ｕモル比の経時変化を、アルゴンガスのみを供給した場合と比較して示したグラフである。
【図３】試料加熱ヒータとして１９５℃油浴を用いた実施例２の場合の試料温度と試料中のＮＯ３ −／Ｕモル比の経時変化を、アルゴンガスのみを供給した場合と比較して示したグラフである。
【符号の説明】
１：担体ガス ２：ヒータ ３：水蒸気発生器
４：保温炉 ５：ヒータ ６：硝酸塩容器
７：冷却器 ８：冷却器 ９：アルカリ溶液
１０：ｐＨメータ １１：記録調節計 １２：冷却水
１３：電磁切換弁 １４：手動弁 １５：水溜[0001]
[Industrial application fields]
The present invention relates to a method for preparing a substoichiometric or stoichiometric nitrate solution such as a nuclear fuel material used as a starting material when preparing microspherical ceramic particles such as ceramic fuel particles for nuclear reactors.
[0002]
[Prior art]
In the process of producing fuel gel particles by the sol-gel method used in the field of ceramic fuel particles for nuclear reactors, when a substoichiometric nitrate solution containing a fuel metal such as uranium as a starting material solution is prepared, metal oxidation is performed. A method is used in which product powder is dissolved in nitric acid or a stoichiometric metal nitrate solution, or an organic reducing agent is added to the stoichiometric nitrate solution to decompose and remove nitric acid.
[0003]
[Problems to be solved by the invention]
An object of the present invention is a process for handling fine fuel oxide powder, which is a radioactive substance that causes an increase in worker exposure, which is indispensable in the prior art, or a process involving the risk of adding an organic reducing agent to a nitrate solution as an oxidizing agent. The object of the present invention is to provide a method for preparing a desired starting material solution without going through the steps.
[0004]
[Means for solving the problems and their functions]
As a result of diligent research by the inventors of the present application, the means adopted for solving the target problem are as follows.
[0005]
First, in addition to increasing the denitration efficiency by heating in an atmosphere containing water vapor, the main component of the released gas can be in the form of nitric acid rather than nitrogen oxide, and the end point of the desired denitration reaction is as follows: In this way, automatic control can be performed accurately. That is, using an apparatus as shown in FIG. 1, the carrier gas 1 is introduced into the water 3 heated by the heater 2 to contain water vapor, and the water vapor is passed through the heat retaining furnace 4 into the nitrate container 6 heated by the heater 5. Lead. The nitric acid thus released is introduced into the nitric acid collecting alkaline solution 9 through the cooler 7 in which the cooling water is not flowing together with the carrier gas, and then in the cooler 8 in which the cooling water is flowing. The initial amount of alkali in this solution is set equal to the nitric acid to be released. While the pH of the alkaline solution is continuously monitored by the recording controller 11 connected to the
[0006]
Second, when the molten salt-like object to be heated in the container 6 after the reaction is cooled to room temperature and solidified, the container is damaged due to volume expansion due to moisture absorption of the solid. The manual valve 14 is opened in a state maintained at a high temperature of 100 ° C. or lower, and the solid water is added to the water reservoir 15 to change the solid into an aqueous solution, followed by cooling.
[0007]
【Example】
The present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples.
[0008]
[Example 1]
An oil bath is used as a heater for the sample (uranyl nitrate solution) of the apparatus shown in FIG. 1, and a mixed gas obtained by bubbling argon into water at 95 ° C. in a water vapor generator at a rate of 50 ml / min (water vapor + argon) is used. The change over time in the NO 3 − / U molar ratio in the sample was examined by examining the amount of released nitric acid while changing the sodium carbonate solution for collecting and releasing the released nitric acid from time to time. The sample before the reaction is a free nitric acid-containing uranyl nitrate solution 60 ml having a U concentration of 2.00 mo1 / 1 and a NO 3 − / U molar ratio of 2.10.
[0009]
About 80 minutes after the start of heating the oil bath at the set temperature of 160 ° C., the sample temperature became about 110 ° C., the release of nitric acid started, and as a result of heating up to 430 minutes, the NO 3 − / U molar ratio reached 1.86. . (The calculated value from the collected nitric acid was 1.83, which was consistent within the error range). The sample temperature was 147 ° C. after 290 minutes. The sample temperature during this period and the NO 3 − / U molar ratio of the sample calculated from the collected nitric acid are shown in FIG. 2 with respect to the time after the start of heating. (FIG. 2 also shows the results when only argon gas is supplied.)
[0010]
[Example 2]
In the same manner as in Example 1, only the oil bath set temperature was changed to 195 ° C., and the change over time in the NO 3 − / U molar ratio was examined. 206 minutes after the start of heating, the NO 3 − / U molar ratio reached 1.63. (The calculated value from the collected nitric acid was 1.65, which was consistent within the error range). The sample temperature was 180 ° C. after 130 minutes. The sample temperature during this period and the NO 3 − / U molar ratio of the sample calculated from the collected nitric acid are shown in FIG. 3 with respect to the time after the start of heating. (In FIG. 3, the results when only argon gas is supplied are also shown in comparison.)
[0011]
[Example 3]
Using the apparatus shown in FIG. 1, the same pre-heating sample and heating conditions as those of Example 2 were applied, and the NO 3 − / U molar ratio target value was set to 1.55. Specifically, the alkaline solution for collecting released nitric acid contains sodium carbonate equivalent to the released nitric acid until the final value of NO 3 − / U molar ratio of the sample reached 1.55. When the pH reached 4, it was set so that a signal for operating the
[0012]
The sample temperature was 184 ° C. after 160 minutes. After 252 minutes the pH was below the set value and the signal was emitted. When the sample temperature reached 80 ° C. after the heating, the manual valve 14 was opened and predetermined water was supplied from the water reservoir 15 into the sample container. Eventually it was heated to 95 ° C. to dissolve all internal solids. The NO 3 − / U molar ratio of this sample solution was 1.57 which coincided with the target value within the range of error.
[0013]
【The invention's effect】
In the prior art, a process for handling radioactive fine powder that causes an increase in the degree of worker exposure or a highly dangerous reduction reaction process is required. However, as a result of the present invention, in addition to making these steps unnecessary, a method for preparing a substoichiometric or stoichiometric nitrate solution that can control the amount of denitration as desired and can be automated is realized. It was. In addition, by performing the denitration reaction in water vapor, as shown in comparison with FIGS. 2 and 3, a method of proceeding with higher efficiency than that by thermal decomposition was realized.
[Brief description of the drawings]
FIG. 1 shows an example of an apparatus for carrying out the method of the present invention.
FIG. 2 shows the changes over time in the sample temperature and NO 3 − / U molar ratio in the sample in Example 1 using a 160 ° C. oil bath as the sample heater, compared with the case where only argon gas was supplied. It is the shown graph.
FIG. 3 shows the change over time in the sample temperature and NO 3 − / U molar ratio in the sample in Example 2 using a 195 ° C. oil bath as the sample heater, compared with the case where only argon gas was supplied. It is the shown graph.
[Explanation of symbols]
1: Carrier gas 2: Heater 3: Steam generator 4: Incubator 5: Heater 6: Nitrate container 7: Cooler 8: Cooler 9: Alkaline solution 10: pH meter 11: Recording controller 12: Cooling water 13: Electromagnetic switching valve 14: Manual valve 15: Water reservoir
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29014894A JP3626519B2 (en) | 1994-11-24 | 1994-11-24 | Substoichiometric or stoichiometric nitrate solution preparation method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29014894A JP3626519B2 (en) | 1994-11-24 | 1994-11-24 | Substoichiometric or stoichiometric nitrate solution preparation method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08151204A JPH08151204A (en) | 1996-06-11 |
| JP3626519B2 true JP3626519B2 (en) | 2005-03-09 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP29014894A Expired - Fee Related JP3626519B2 (en) | 1994-11-24 | 1994-11-24 | Substoichiometric or stoichiometric nitrate solution preparation method |
Country Status (1)
| Country | Link |
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| JP (1) | JP3626519B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4334316B2 (en) | 2003-10-16 | 2009-09-30 | 原子燃料工業株式会社 | Ammonium uranate particle production equipment |
| WO2005061387A1 (en) * | 2003-12-24 | 2005-07-07 | Nuclear Fuel Industries, Ltd. | Liquid stock for dropping, method for preparing liquid stock for dropping, method for preparing uranyl nitrate solution, and method for preparing polyvinyl alcohol solution |
-
1994
- 1994-11-24 JP JP29014894A patent/JP3626519B2/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| JPH08151204A (en) | 1996-06-11 |
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