JPH0726949B2 - Degradation method of extraction solvent - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for measuring the deterioration degree of an extraction solvent used in the Purex-process. More specifically, the present invention relates to a method for measuring the degree of deterioration of an extraction solvent used in the Purex method, which has a rapid, accurate and excellent measurement reproducibility.

<Prior Art> The Purex method is a process for recovering laune and plutonium that can be reused as nuclear fuel from a nitric acid aqueous solution of spent nuclear fuel by a solvent extraction method. The extraction solvent is tributyl phosphate (hereinafter referred to as extractant). TBP) is diluted to 10 to 30 V / V% with a hydrocarbon compound that is a diluent, and a typical example is TBP / dodecane system (Nuclear Handbook, pp, 589 (1976) and Nuclear Chemistry). Engineering, pp.1
37, pp.148 (1976)).

It is clear that the Purex method is a strong radiation field, but as mentioned above, it is a system in which water and nitric acid coexist, and the extraction solvent decomposes chemically and / or radioactively, resulting in various decomposition products. Product (hereinafter referred to as a deteriorated product).

Extraction solvent with a high content of deterioration products, that is, extraction solvent with a high degree of deterioration, should be almost completely removed from the raw products of the Purex method, such as pun and plutonium, and the separation performance of fission products ( Hereinafter, it is known that the decontamination performance of FP) decreases (Nuclear Chemical Engineering, pp.156-159 (1976)).

Therefore, it is necessary to establish a technique to quantitatively grasp the deterioration degree of the extraction solvent, and TPGarrett, Jr. (USAEC report
The Z-number established by DP-237, Aug., 1957) and / or the H-number established by Field and Jenkins (AERE-R 3507, Dec., 1960) have been used as solvent degradation indicators until now. Has been done.

These two indicators were determined by quantifying the amount of zirconium or hafnium retained in the deteriorated extraction solvent, which could not be removed by washing with nitric acid, and calculated as "10 ⁹ gram atom of metal present in solvent". It shows the deterioration degree of the solvent quantitatively by displaying it as a unit of "number". Naturally, the larger the number, the more the deterioration of the solvent is progressing, and the decontamination performance of the above-mentioned FP deteriorates. The greatest feature is that it is a direct expression of.

The method for measuring Z-number or H-number is, conceptually, pretreatment of a solvent sample, extraction equilibration with a nitric acid acidic standard solution containing a certain amount of zirconium or hafnium, post-treatment by washing with a nitric acid aqueous solution, zirconium or hafnium Although it consists of measuring the content, the specific procedure is extremely complicated as shown below. That is, the pretreatment of the solvent sample a) The solvent sample is washed twice with an equal volume of dilute aqueous alkaline solution.

B) Next, the solvent phase is washed with an equal volume of dilute nitric acid aqueous solution to be almost neutralized.

C) Further, the solvent phase is brought into contact with an equal volume of 3N nitric acid aqueous solution to equilibrate with nitric acid.

Extraction equilibrium with a nitric acid acidic standard solution containing a certain amount of zirconium or hafnium I) -Containing the solvent phase after the treatment of (a) and an equal volume of zirconium or hafnium at a concentration of 10 ^-3 mol / Achieve extraction equilibrium of zirconium or hafnium by sufficiently contacting with 3N nitric acid aqueous solution.

Post-treatment by washing with nitric acid aqueous solution The solvent phase after the treatment of a) -b) is washed 6 times with an equal volume of 3N nitric acid aqueous solution.

 Measurement of zirconium or hafnium content Quantitate by an analytical method that can quantify the minimum concentration of about 10 ppb.

In this procedure, the metal content is measured by selecting a suitable method, and the measurement time per sample is about a dozen minutes to 30 minutes, but the organic solvent-water-based solution described in Repeating the liquid extraction operation requires several hours even when the two layers are smoothly separated, and requires manual labor for the operation, and automation or in-line measurement is almost impossible. It is not an exaggeration.

Therefore, it must be said that it is an index unsuitable for dynamic operation management of the Purex method, and there is a desperate need for a solvent deterioration index for the management of the Purex method that is quick, accurate, and has high measurement reproducibility. It was

On the other hand, in the field of chemical technology, the progress of separation analysis technology, the progress of electronics technology, and the progress of information processing technology using a computer have been combined, and automation of analytical instruments has advanced to the ultimate, from sampling to data processing. Can be implemented without any human intervention.

Attempts to apply instrumental analysis techniques to solve the problems of nuclear fuel reprocessing processes, including their rudimentary ones, date back to the early 1960s (see, for example, AERE, supra).
-R 3507, Dec., 1960 and Nuclear Science and En
gineering, Vol.17, pp.620 ~ 625, pp.626 ~ 637, pp.638 ~ 6
50 (1963)).

Then, in order to address the problem of deterioration of the extraction solvent, a trial period of introducing instrumental analysis methods such as infrared spectroscopy and gas chromatography continues for about 10 years (for example, Proc.Intern.Solvent Extraction Conf. Hague, Sess
ion 1C-paper pp.131 (1971), Radiochem.Radioanal.L
etters, Vol.12, No.2-3, pp.79-88 (1972), Radiochem.
Radioanal.Letters, Vol.20, No.1, pp.47-58 (1974)).

In the early 1970s, the KfK research group used gas chromatographic method as the separation analysis technology and mass spectrograph as the detector of the eluted components, so-called gas chromatography mass spectrometry (GC
-MS method) was applied to the elucidation of degradation products in degrading solvents, many components were identified, and a part of the mechanism of solvent degradation was elucidated. (KfK-1373, Nov.1973, K
fK-2304, Juli 1977 and KfK-3639, Dez. 1983). This trend continues to this day, and a recent oral presentation of the Japan Atomic Energy Society reported that a wide variety of degradation products were identified, and the mechanism of solvent degradation is shown (Atomic Energy Society of Japan). "Showa 60th Annual Meeting" Abstracts, No. 1
II Volume, pp. 9 (1985)).

However, these advanced instrumental analysis techniques or
Contrary to expectations, very few attempts have been made to apply the analytical results obtained therefrom as a solvent deterioration measuring method or a solvent deterioration index for quantitatively expressing the deterioration of a solvent. Slightly
Not only did the KfK research group report results, they consciously ruled out that one component and / or several components of a specific degradation product were used as indicators. is doing.

The reason is that they say that analysis of specific components of degraded products can only be achieved using highly sophisticated measuring instruments, and that sophisticated analytical instruments are difficult to employ for process control. (Abstr.of Karlsruhe I
tern.Couf.on Anal.Chem.in Nucl.Technol., pp.169, Jun
e 1985).

<Problems to be Solved by the Invention> Generally speaking, preferable requirements for the analysis / measurement method of various characteristic values are that the analysis / measured values are accurate, and that the measurement reproducibility is excellent. Short time Small amount of required sample Pretreatment of sample should be as easy as possible Instrument used for analysis and measurement should be robust Maintenance of equipment used for analysis and measurement should be easy It is possible to add inline.

However, the Z-number or H-number, which is still a method of measuring the degree of deterioration of solvents, is only sufficient to satisfy the above conditions, and there are many problems to be solved.

The present inventors have conducted intensive studies in view of the present situation, and as a result, have established a method for measuring the degree of deterioration of an extraction solvent that can sufficiently satisfy the above items, and completed the present invention.

<Means for Solving the Problems> The present invention relates to the content of one component and / or several components of dibutyl phosphate = monosubstituted butyl, which is a deterioration product in the extraction solvent used in the Purex method, in a gas chromatograph. The present invention relates to a method for measuring the degree of deterioration of an extraction solvent, which is characterized in that it is measured by the Tograph method. The present invention will be specifically described below.

The Purex method according to the present invention comprises dissolving spent nuclear fuel in nitric acid, and then separating the raw and plutonium useful as nuclear fuel from fission products, separating uranium and plutonium, and purifying uranium and plutonium. This is a wet fuel nuclear fuel reprocessing process in which solvent concentration and back extraction into nitric acid are combined after adjusting the nitric acid concentration suitable for the process.

The extraction solvent used in the Purex method is a system in which TBP used as an extractant is diluted with a hydrocarbon-based diluent.

As an extractant, TBP is used exclusively because of its excellent performance as an extractant, its excellent radiation resistance, and its high flash point (Nuclear Handbook, pp.589).
(1976), Nuclear Chemical Engineering, pp.148 (1976) and Nuclear Chemical Engineering, Volume IV, Chemical Engineering for Fuel Reprocessing and Radioactive Waste Management, pp.10 (1983)).

As the diluent, a hydrocarbon compound, which has excellent radiation resistance and is a good solvent for TBP, is used. A typical example is kerosene or dodecane. Recently, dodecane is widely used (Nuclear Chemical Engineering, pp.148 (1976)).

The mixing ratio of the extractant and the diluent is in the range of 10 to 40% in volume percentage, and 30% is typical among them.

The mechanism of dissolution of uranium and plutonium in the TBP / dodecane extraction solvent is mainly the reaction of uranium and plutonium to form a complex compound with TBP that acts as an extractant, and uranium and plutonium form a complex compound with TBP. Under the conditions suitable for the reaction, a remarkable feature is that the complex compound forming reaction with the fission product (hereinafter referred to as EP) does not substantially proceed. Therefore, the decontamination coefficient of EP in the solvent extraction process of the Purex method is extremely high.

However, when the extraction solvent is used for the extraction operation in the presence of water, nitric acid, oxygen and radiation and chemically and / or radiation decomposes to form a degraded product, the decontamination coefficient of FP is significantly reduced. It has been known.

When the decontamination coefficient of FP is reduced, strong γ is found in the recovered uranium and recovered plutonium, which are the products of the Purex method.
As a result, it contains a large amount of FP, which is a radioactive material, and causes a serious problem of gamma-ray shielding in the nuclear fuel manufacturing process using recovered uranium and recovered plutonium.

However, since the deterioration of the extraction solvent is unavoidable,
Due to the control of the Purex method, the degree of deterioration of the extraction solvent is quantitatively grasped, and the amount of uranium and recovered plutonium contained in the recovered uranium is recovered.
The need to control the FP content below a certain level was recognized.

Such recognition already existed in the early stage of nuclear fuel reprocessing, but on the other hand, it was also the initial stage of the progress of the separation and analysis means for organic compounds, so that it is not possible to use the components of an extremely wide variety of degradation products as control indicators. It was impossible. For this reason,
A management index of solvent deterioration was devised by applying the phenomenon of reduction in decontamination coefficient of FP.

This solvent deterioration index is still used as H
It is an index called -number or Z-number.

Both of these two solvent deterioration indexes quantitatively express the deterioration degree of the solvent by quantifying the amount of zirconium or hafnium that cannot be removed from the deteriorated extraction solvent even by washing with nitric acid. The greatest feature is that it is a direct expression of the decrease in the decontamination coefficient of.

However, the procedure for measuring Z-number and H-number is as follows: pretreatment of solvent sample; extraction equilibration with acidic nitric acid standard solution containing a certain amount of zirconium or hafnium; posttreatment by washing with nitric acid aqueous solution; measurement of zirconium or hafnium content. In this procedure, the metal content is measured by selecting a suitable method, and the measurement time per sample is about ten minutes to 30 minutes, but the organic solvent described in -Repeating the water-liquid extraction operation requires several hours even when the two layers are smoothly separated, and manpower is required for the operation, and automation or inline measurement is almost impossible. It is no exaggeration to say that.

In contrast to this fact, the content of one component and / or several components of the specific component of the degradation product in the extraction solvent was measured by gas chromatography using a sample without any pretreatment. The possible features of the present invention become extremely clear.

Degradation products of the extraction solvent, since one in which radiation is generated is irradiated in a system which exists TBP- dodecane -H ₂ O-HNO _3, TBP present in the system, dodecane, H ₂ O, and HNO ₃
Is a reaction product by an ionic mechanism and / or a radical mechanism involving all of the four components. Therefore, it can be said that the number of deterioration products is infinite, but they can be divided into some typical groups due to their structural characteristics.

That is, lower hydrocarbons which are decomposition products of TBP and / or dodecane Dodecanol, which is a degradation product of an acidic substance dodecane, which is an acidic substance composed of fatty acid, dialkylphosphoric acid and monoalkylphosphoric acid which is a decomposition product of TBP and / or dodecane Substituted derivatives of dodecane such as dodecane, dodecane dimer, which is a degradation product of dodecane, and 3
Hydrocarbons higher than dodecane, which also includes a dimer Dibutyl phosphate = Degradation product of TBP Neutral phosphate ester containing monosubstituted butyl Dimer of TBP, a trimer, which is a degradation product of TBP And higher esters of phosphoric acid including tetramers.

In the present invention, analytical means applicable to the separation analysis of the deterioration products of these extraction solvents, which can be said to be innumerable in number,
It is a gas chromatographic method.

The separation column used in the gas chromatographic method in the present invention is an inner diameter of 2 to 3 m / m, a glass column having a length of 1 to 3 m, and is filled with a column packing material impregnated with a stationary liquid phase selected by a component to be analyzed, A so-called fused column in which a fixed liquid phase selected depending on the component to be analyzed is chemically bonded to the inner wall of a so-called packed column and / or a fused silica capillary having an inner diameter of 0.2 to 0.5 m / m and a length of 10 to 60 m. It is a silica capillary column (hereinafter referred to as FS-capillary column). Above all, the number of theoretical plates per unit length is excellent,
The FS-capillary column, which is overwhelmingly superior in the length of the loaded column, is particularly preferable.

The stationary phase used as the column packing material and FS-capillary column can be roughly divided into three types, low polarity, medium polarity and high polarity, depending on the components to be analyzed so that they can be used properly for the purpose of revealing a better separation situation. It is prepared. The stationary liquid phase that can be preferably used in the present invention has a low polarity.

The detector of the elution component equipped in the gas chromatograph is a thermal conductivity detector (TCD), a hydrogen flame ionization detector (hereinafter FID).
, A flame photometric detector (hereinafter referred to as FPD), a nitrogen phosphorus detector (NPD), and a mass selective detector (hereinafter referred to as MSD). Among them, FID which is highly sensitive to all organic compounds, FPD which can selectively detect phosphorus compounds, and MSD which can identify and quantify the peak components detected by collecting the mass spectrum of organic compounds are particularly useful.

The carrier gas used for gas chromatography can be suitably used as long as it is an inert and highly pure substance available in the column temperature range of room temperature to about 350 ° C. which is a general gas chromatography condition. . Generally, nitrogen, hydrogen, helium, or argon is used.

The case of the FS-capillary column adopted here is no exception, but in the case of the capillary column, hydrogen and helium are highly prized because the degree of change in the separation characteristics of the capillary column with respect to the change in the carrier gas flow rate is significantly smaller than that of nitrogen. Used.

The temperature setting of the separation column in gas chromatography is a very important condition from the viewpoint of component separation.

First, it is necessary to decide whether to select a constant temperature analysis in which the separation column is kept at a constant temperature, or to select a temperature increase analysis in which the separation is performed while increasing the column temperature according to a constant temperature increase program.

In general, isothermal analysis is selected when the number of components to be separated is small and the boiling range of the components is not so wide. Temperature rising analysis is selected when the number of components to be separated is large and the boiling point range is wide, or when the number of components is not so large and the boiling point range is wide.

Regardless of which analysis is selected, the temperature conditions must be set each time depending on the separation column used and the sample to be analyzed, but as a rough guideline, the temperature upper limit should be slightly lower than the maximum operating temperature of the stationary liquid phase used for the separation column. Low temperature For the analysis of components close to pure products, the temperature is 20 to 50 ° C lower than the boiling point.If the boiling point range of the analytical component is 100 ° C or less, the temperature close to the boiling point of the lowest boiling component can be mentioned (in gas chromatography, pp .36
(1978)).

In the analysis for the deteriorated solvent of the present invention, the temperature rising analysis was selected because of the large number of components to be separated and the wide boiling range.

Is a preferable condition.

The deterioration product whose content should be measured as an index of the degree of deterioration of the extraction solvent is a deterioration product whose content increases in proportion to the radiation dose applied to the extraction solvent or the radiation dose absorbed by the extraction solvent. Need to be Since the 6 categories of degradation products already mentioned are produced by irradiation of the extraction solvent with radiation, it can be said that some of the requirements that can be used as an index are satisfied.

On the other hand, if a study is added from the viewpoint of convenience for measuring the content by the detector of the eluted component used in gas chromatography, it is necessary to meet certain requirements for the suitable detector already listed.

Since FID is sensitive to all organic compounds having carbon and hydrogen atoms as basic building blocks, the degradation product used as an indicator has a preferable retention time that is clearly distinguished from other degradation products, and It is indispensable to show more prominent increasing behavior in the holding time.

Since FPD is specifically sensitive to phosphorus compounds, it is extremely advantageous if there are degradation products that elute during the retention time period that is clearly distinguishable from TBP, which is the main component of the extraction solvent, which is a phosphorus compound. One of the degradation products that satisfy this condition is a neutral phosphate derivative.

MSD is a Selec that detects only specific fragment ions.
By using an ion detection method called ted Ion Monitoring (hereinafter referred to as SIM), there is an advantage that a desired degradation product can be detected from among a myriad of degradation products.

In the case of MSD as well as FPD, it is extremely convenient for selective detection if a neutral phosphate ester derivative that produces a specific fragment ion is present in the degradation product.

As a result of searching the deterioration products which satisfy these requirements from the myriad of deterioration products, dibutyl phosphate = monosubstituted butyl used as an index in the present invention was selected.

This component is a degradation product of TBP, which is the main component of the extraction solvent, and is a compound in which one substituent is introduced into one of the three n-butyl groups of tributyl phosphate. x-oxobutyl and the general formula Is a compound represented by.

Where x is 2 and 3, x is C ₁ -C ₁₂ alkyl, —OH, —ONO ₂ , —ONO, especially —OH, —ONO.
₂ , is preferred. To give a specific example, dibutyl phosphate = 2
-Oxobutyl, dibutyl phosphate = 3-hydroxybutyl, dibutyl phosphate = 2- (nitrooxy) butyl and dibutyl phosphate = 3-nitrooxybutyl.

The compound group shown here appears in the chromatograph as a peak having a remarkable increasing behavior that is clearly distinguished from other deterioration product groups in the retention time period slightly longer than TBP.

The presence of these compounds can be clearly judged by FID, and they are sensitive to FPD, and the existence of components can be confirmed very clearly in SIM of m / e = 99 of MSD. Quantification is easy with any of these detectors.

It should be noted that due to the elution of these degradation products, no pretreatment to be added to the degraded solvent sample is required.

As shown in the general formula, since the degradation product used as an index in the present invention is a neutral phosphate ester, it is easily vaporized under the above-mentioned gas chromatography conditions which are the conditions of general gas chromatography, and the separated product is separated into a separation column. It is injected and the components are eluted. However, since the deteriorated solvent contains nitric acid even though it is a trace amount, washing the deteriorated solvent is a preferable method from the viewpoint of reducing the maintenance frequency of the gas chromatograph. Very advantageously, it has been confirmed that dibutyl phosphate = mono-substituted butyl described above shows almost no decrease in content due to dilute alkaline washing-water washing treatment. Therefore, it is also possible to add a simple cleaning treatment as a pretreatment before the gas chromatography of the deteriorated solvent.

The embodiments of the patent of the present application will be specifically described below as examples, but it goes without saying that the patent of the present application is not limited to these examples.

Example 1 Preparation of simulated deteriorated solvent A simulated deteriorated solvent was prepared by selecting conditions simulating one step of the Purex method.

(1) Preparation of solvent TBP (special reagent grade) 150 ml and dodecane (reagent special grade) 350 ml were mixed well to prepare a solvent sample.

(2) Pretreatment of γ-ray irradiation The solvent sample prepared in (1) was stirred at 500 rpm for 10 minutes in an equal volume of 3N nitric acid and a glass bottle to equilibrate with nitric acid.

(3) γ-irradiation Put the solvent phase pretreated in (2) into a glass reagent bottle with an internal volume of 500 ml and gently stir it in an air atmosphere with a total irradiation dose of 10 × 10 ⁶ roentgen (10 mega X-rays, hereinafter referred to as 10 MR) were irradiated.

Irradiation of γ-rays was outsourced to the Association for the Promotion of Radiation Irradiation and Takasaki Plant.

The source was ⁶⁰ Co.

(4) Post-treatment of γ-ray irradiation solvent After collecting 15 ml of a sample for measurement from the solvent after γ-ray irradiation, the following post-treatment was performed.

Wash twice with an equal volume of 1N aqueous sodium hydroxide.
Washing is performed by stirring in a glass bottle at 500 rpm for 10 minutes.

The solvent phase after alkali washing is neutralized with an equal volume of 0.2N nitric acid. Neutralization is carried out in glass screw by stirring at 500 rpm for 10 minutes.

The solvent phase after neutralization is equilibrated with nitric acid by the method described in (2).

(5) Repeat operations (2) to (4) until the total irradiation dose of γ-rays is 10MR, 20MR, 30MR, 40MR, 50MR, 60MR, 70MR,
Ten simulated degradation solvents of 80MR, 90MR, and 100MR were created.

Example 2 Gas Chromatography of Simulated Degraded Solvent A gas chromatograph equipped with a FID was equipped with an FS-capillary column having a low polarity stationary liquid phase, a length of 12.5 m, an inner diameter of 0.33 mm, and a film thickness of 0.50 μm, and a column thermostat was used. Temperature, 100
℃ (hold for 8 minutes) -Up to 260 ℃ at -3 ℃ / min, the temperature is raised by program control of ‐260 ℃ hold, sample is injected by split method using helium as carrier gas, and gas chromatography of simulated deterioration solvent Was done. The analysis time for one sample was 90 minutes from the injection of the sample to the temperature decrease in the column constant temperature bath after completion of the component elution and the creation of analysis data by the data processor.

It was found that the four numbered peaks on the gas chromatogram shown in Fig. 1 were eluted with a clear increase in the retention time, which is slightly longer than that of TBP, which is the main component of the solvent. It was

FIG. 2 shows the results of measuring the contents of the components corresponding to the four peaks, using tridecane as the internal standard substance. It was confirmed that all four components show the behavior of increasing the content corresponding to the increase of the total irradiation dose of γ rays.

Example 3 H-number measurement of simulated deteriorated solvent The H-number of the simulated deteriorated solvent was measured by the procedure described below.

 Wash an equal volume of 1N sodium hydroxide solution.

Washing is performed by shaking with a shaker for 300 reciprocations / minute for 5 minutes.

 Oil-water separation by centrifugation at 3000 rpm for 1 hour.

 Repeated.

Neutralization with an equal volume of 0.2N nitric acid. Neutralization is 300 round trips /
Minutes, shaking by a shaker for 5 minutes.

Equilibration of nitric acid with an equal volume of 3N nitric acid. Nitric acid equilibration is 30
Shake with a shaker for 0 round trips / min for 5 minutes.

Extraction equilibration of hafnium with an equal volume of 10 ^-3 M hafnium / 3N nitric acid standard solution. Extraction equilibration is 300 round trips / min, 1
Shake for 5 minutes on a shaker.

Nitric acid cleaning with an equal volume of 3N nitric acid. 300 round trips for cleaning
Minutes, shaking by a shaker for 5 minutes.

The washing is repeated 6 times.

The amount of hafnium in the solvent phase is quantified by argon inductively coupled plasma emission spectroscopy.

The H-number is calculated from the hafnium quantification result obtained in step.

FIG. 3 shows the increase behavior of the H-number with respect to the increase of the total irradiation dose of γ rays.

The behavior of increasing the content of the four components shown in FIG. 2 and the behavior of increasing the H-number shown in FIG. 3 correspond well, and one of the four components and / or the other three components are solvent-degraded. It was confirmed that it is useful as a solvent deterioration index, like the H-number, which is an index.

Further, the time required to measure the H-number required about 8 hours until the calculation of the H-number, and how was the analysis time for the four components by gas chromatography described in Example 2 90 minutes? It is clear if it is a long time.

Example 4 Comparison of accuracy of degradation product analysis in simulated deteriorated solvent by gas chromatography and accuracy of H-number measurement of simulated deteriorated solvent.

(1) Preparation of simulated deteriorated solvent The solvent sample subjected to the treatments of Examples 1- (1) and-(2) was dispensed into three glass reagent bottles, and the total irradiation dose was 25M.
Irradiation with γ-rays of R, 50 MR, and 100 MR produced three kinds of simulated deteriorated solvents.

Irradiation with γ rays was performed as described in Example 1- (3).

(2) Analysis of Degraded Products by Gas Chromatography The gas chromatography conditions described in Example 2 were applied as they were, and the analysis of the four components in the simulated degraded solvent was repeated 5 times for each simulated degraded solvent. The values were statistically processed. The results are shown in Table 1.

(3) H-number measurement (3) Measurement of H-number The procedure described in Example 3 was applied as it was, and 5 samples were taken for each of the simulated deteriorated solvents to measure the H-number.

The results are shown in Table 2. Here, the analysis value of hafnium which is the basic data for calculating the H-number is shown.
The analytical values were statistically processed.

Comparing the analysis results shown in Table 1 and Table 2,
-While the number is measured as a solvent deterioration index,
It can be seen that the method of measuring one component and / or several components of the specific component of the degradation product by gas chromatography has higher accuracy.

Example 5 Gas Chromatography Mass Spectrometry (hereinafter GC
-MS method)) Identification of four components of deterioration products The gas chromatography of the simulated deterioration solvent described in Example 2 was carried out using a mass spectrograph as a detector. This was carried out by the so-called GC-MS method, which was carried out in place of MSD, and a mass spectrum of four components of the deteriorated product was obtained.

As a result of deciphering the mass spectrum, the four components were identified as follows. This result was confirmed by agreement with the mass spectrum of the separately synthesized standard product.

(1) Peak component: dibutyl phosphate = 2-oxobutyl (2) Peak component: dibutyl phosphate = 3-hydroxybutyl (3) Peak component: dibutyl phosphate = 2- (nitrooxy) butyl (4) Peak Ingredients: Dibutyl phosphate = 3- (nitrooxy) butyl mass The results of the spectrum analysis are shown in Table 3- (1) and Table 3-
It is shown in (2).

<Advantages of the Invention> According to the present invention, a method for measuring the degree of deterioration of an extraction solvent, which is fast, accurate, and has excellent measurement reproducibility, is proposed. Be served. The analytical instrument used in the measurement method of the present invention is a gas chromatograph, and since in-line analysis is possible, it is useful for dynamic deterioration degree management of the extraction solvent used in the reprocessing process of spent nuclear fuel. It can be said that it provides a measurement method.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a gas chromatogram of a simulated deteriorated solvent. FIG. 2 is a diagram showing the relationship between the content of the components corresponding to the four peaks and the γ-ray irradiation dose. FIG. 3 is a relationship diagram between the H-number of the simulated deteriorated solvent and the irradiation dose of γ rays.

Front Page Continuation (72) Inventor Kenichiro Shigeoka 5-1 Anezaki Kaigan, Ichihara, Chiba Prefecture Sumitomo Chemical Co., Ltd. (72) Inventor Takao Akiyama 4-3 Muramatsu, Tokai-mura, Naka-gun, Ibaraki 33 Power reactor and nuclear fuel Development Corp.Tokai Plant (72) Inventor Yukio Wada 4-3 Muramatsu, Tokai-mura, Naka-gun, Ibaraki Prefecture 33 Power Reactor / Nuclear Fuel Development Corp.Tokai Plant (72) Inventor Yasuo Suzuki, Tokai-mura, Naka-gun, Ibaraki Prefecture No. 4 33 Reactor / Nuclear Fuel Development Corporation Tokai Works

Claims (1)

[Claims] 1. Dibutyl phosphate = mono-substituted butyl dibutyl phosphate = 2-oxobutyl, dibutyl phosphate = 3-hydroxybutyl, dibutyl phosphate as a degradation product in the extraction solvent used in the Purex method. = 2-
(Nitrooxy) butyl and dibutyl phosphate = 3-
A method for measuring the degree of deterioration of an extraction solvent, which comprises measuring the content of one or four components selected from (nitrooxy) butyl by gas chromatography without any pretreatment.