JP7829863B2 - Method for analyzing chlorine with mass number 36 - Google Patents

Description

This invention relates to an analytical method for chlorine with a mass number of 36. In particular, this invention relates to an analytical method that can accurately quantify chlorine with a mass number of 36 in a shorter time compared to conventional methods.

Chlorine with mass number 36 (also called chlorine-36 or Cl-36) is a long-lived radionuclide that undergoes beta decay with a half-life of 3.01 × ^10⁵ years, emitting beta rays with a maximum energy of 709 keV at a emission rate of 98.1%. Quantitative analysis methods for Cl-36 include measuring beta rays, and analytical methods for Cl-36 in liquid samples have been established.

In the method for measuring beta rays, the chloride ion concentration in the sample is first quantified and confirmed using ion chromatography or other methods, and then the chloride ion carrier necessary for the analysis is added. Chlorine in the sample is purified by an oxidative gasification recovery operation, which involves sequentially adding nitric acid and potassium permanganate and heating. After confirming that elements interfering with the measurement of beta rays emitted by Cl-36 have been removed through these separation and purification operations, the Cl-36 concentration (Bq/g) in the sample is determined by measuring the beta rays emitted by Cl-36.

This beta-ray-based analytical method requires a chemical separation procedure to separate interfering elements present in the solution and isolate Cl-36. Therefore, it involves a complex processing procedure, which is time-consuming and problematic.

Similar to Cl-36, strontium with mass number 90 (Sr-90) is another radionuclide that is difficult to quantify. A method using a quadrupole mass filter is known for analyzing Sr-90 quickly and with high accuracy (see, for example, Patent Document 1).

Japanese Patent Publication No. 2015-87363

Following the 2012 amendment to the Nuclear Reactor Regulation Law, an increase in the decommissioning of aging nuclear power plants is expected. The Tokai Nuclear Power Plant, already scheduled for decommissioning, employs a graphite-moderated, carbon dioxide-cooled reactor. This type of reactor generates a higher amount of Cl-36 radioactivity compared to other light water reactors. Therefore, rapid measurement of Cl-36 is required during decommissioning. Graphite-moderated, carbon dioxide-cooled reactors are common in nuclear power plants in the UK and France, and with the expected increase in decommissioning in the future, the demand for rapid Cl-36 measurement is growing internationally. Consequently, conventional methods for measuring beta radiation, which require approximately five days, will not be sufficient to meet the increasing demand for measurements.

While rapid analysis methods for Sr-90 have been established, as shown in Patent Document 1, Cl-36 differs from Sr-90 in that, due to its mass number, it has been difficult to achieve sufficient sensitivity using mass spectrometry.

In response to the above problem, an analytical method is needed to rapidly and accurately measure chlorine with a mass number of 36.

According to one embodiment, the present invention is a method for analyzing chlorine with a mass number of 36,
The process involves introducing the sample solution into a plasma ion source and ionizing it,
The process involves contacting the group of ions obtained in the ionization process with oxygen gas to produce ClO oxide ions with a mass number of 52,
In a quadrupole mass filter, the process involves removing ions with mass numbers other than 52,
The present invention relates to a method comprising the step of detecting the signal of an ion with a mass number of 52 that has passed through the quadrupole mass filter.

In the above method, it is preferable to include a step of removing interfering elements from the sample solution by ion chromatography before the ionization step.

In the above method, it is preferable that the step of detecting the signal of the ion with mass number 52 is a step of detecting chlorine with mass number 36 based on the peak waveform of the ion count with mass number 52.

In the above method, it is preferable that the step of detecting chlorine with mass number 36 based on the peak waveform of the ion count is a step of quantifying chlorine with mass number 36 based on the integrated value of the peak area of the ion count with mass number 52.

In the above method, it is preferable that the step of detecting chlorine with mass number 36 based on the peak waveform of the ion count is a step of quantifying chlorine with mass number 36 based on the maximum peak height of the ion count with mass number 52.

In the above method, it is preferable to include a step of applying the sample solution to a concentration column capable of specifically extracting chlorine, and concentrating the chlorine, before the ionization step or the step of introducing the solution into the ion chromatography apparatus to remove interfering elements.

According to the present invention's method for analyzing chlorine with a mass number of 36, it is possible to quantify Cl-36 with high accuracy in a time fraction of that required by conventional methods.

Figure 1 is a graph showing the oxygen gas concentration (mL/min) and the count of mass number 35 ions that passed through the quadrupole mass filter. Figure 2 is a graph showing the oxygen gas concentration (mL/min) and the count of mass number 36 ions that passed through the quadrupole mass filter. The sample solution used for measurement does not contain Cl-36. Figure 3 is a graph showing the oxygen gas concentration (mL/min) and the count of mass number 37 ions that passed through the quadrupole mass filter. Figure 4 is a graph showing the oxygen gas concentration (mL/min) and the ion count of ClO-51 that has passed through a quadrupole mass filter when Cl-35 and O-16 are reacted and detected as ClO with a mass number of 51 (ClO-51). Figure 5 is a graph showing the oxygen gas concentration (mL/min) and the ion count of ClO-52 that passed through a quadrupole mass filter when chlorine without Cl-36 is reacted with O-16 and detected as ClO with a mass number of 52 (ClO-52). Figure 6 is a graph showing the oxygen gas concentration (mL/min) and the ion count of ClO-53 that has passed through a quadrupole mass filter when Cl-37 and O-16 are reacted and detected as ClO with a mass number of 53 (ClO-53). Figure 7 shows the calibration curve when detecting Cl-35 as ClO-51. Figure 8 shows the calibration curve when detecting Cl-36 as ClO-52. Figure 9 shows the calibration curve when detecting Cl-37 as ClO-53. Figure 10 is a graph showing the ion counts of ClO-51 and ClO-52 over time, measured by ICP-MS, when a sample containing Cl-35 at a concentration of 0.11 ppm is injected at a volume of 50 μL. Figure 11 is a graph showing the ion counts of ClO-51 and ClO-52 over time, measured by ICP-MS, when a sample containing Cl-35 at a concentration of 0.11 ppm is injected at a volume of 500 μL. Figure 12 is a graph showing the ion counts of ClO-51, ClO-52, and ClO-53 over time, obtained by IC-ICP-MS, when a sample containing Cl-36 at a concentration of 0.16 ppm (190 Bq/mL) is injected using a Cl-36 standard source. Figure 13 is a magnified view of the area around the peak rise point in Figure 12, and is a graph showing that the Cl-36 peak was detected. Figure 14 shows a calibration curve calculated based on the maximum peak height when detecting Cl-36 as ClO-52. Figure 15 shows a calibration curve calculated based on the integrated peak area when detecting Cl-36 as ClO-52.

The embodiments of the present invention are described below. However, the present invention is not limited to the embodiments described below.

According to one embodiment, the present invention relates to a method for analyzing chlorine with a mass number of 36. The method for analyzing chlorine with a mass number of 36 according to this embodiment includes the following steps.
(1) A step of introducing the sample solution into a plasma ion source and ionizing it. (2) A step of contacting the group of ions obtained in the ionization step with oxygen gas to generate ClO oxide ions with a mass number of 52. (3) A step of removing ions with mass numbers other than 52 using a quadrupole mass filter. (4) A step of detecting the signal of ions with a mass number of 52 that have passed through the quadrupole mass filter.

The method for analyzing chlorine with mass number 36 according to this embodiment is an analytical method for identifying chlorine with mass number 36, distinguishing it from its isotopes such as chlorine with mass numbers 35 and 37, and preferably a method for quantifying chlorine with mass number 36. In this specification, chlorine with mass number 36 may be referred to as Cl-36. Similarly, isotopes of an element may be expressed using the format "element symbol - mass number".

The sample solution to be measured is a solution that may contain Cl-36. The solution may be an aqueous solution or a solution containing a solvent other than water. In the ionization step described later, the solution should contain Cl-36 in a state where it can be ionized by a plasma ion source. Note that solutions containing Cl-36 below the detection limit may also contain Cl-36, and any solution for which measurement is required is included in the sample solution. As long as steps (1) to (4) are performed, this can be considered a chlorine analysis method for mass number 36 according to this embodiment.

Specific sample solutions may include, but are not limited to, wastewater from nuclear power plants, environmental water surrounding nuclear power plants, liquids that have come into contact with components of nuclear power plants such as reactors, and environmental water near radioactive waste disposal facilities (e.g., groundwater). When analyzing solid Cl-36 adhering to reactor components or Cl-36 in soil, the components or soil can be washed with an etching solution consisting of acids such as nitric acid or sulfuric acid, and the resulting solution from which the Cl-36 has been eluted can be used as the sample solution.

The sample solution can be subjected to steps (1) to (4) after pretreatment, or steps (1) to (4) can be carried out without pretreatment. Pretreatment options include, but are not limited to, the concentration of Cl-36 and the removal of interfering elements. Concentration and removal of interfering elements will be described later.

Steps (1) to (4) can be carried out using a method and apparatus based on inductively coupled plasma mass spectrometry (ICP-MS). In particular, they can be carried out using an ICP-MS apparatus equipped with a collision reaction cell (CRC) and at least one quadrupole mass filter (MS). Therefore, it may be a single quadrupole type apparatus with one MS positioned after the CRC, a triple quadrupole type apparatus with two MSs flanking the CRC and connected in series, or any other type of apparatus. Such ICP-MS apparatuses are commercially available, and any commercially available product can be used.

In one embodiment, the ICP-MS apparatus may comprise a sample introduction unit equipped with a nebulizer and spray chamber for atomizing the sample solution and carrier gas (Ar gas), and an introduction device for auxiliary gas (Ar gas) and plasma gas (Ar gas); an ionization unit equipped with a torch for generating plasma; and a mass spectrometry unit. The mass spectrometry unit may comprise an interface, an ion lens, a CRC, a quadrupole mass filter, and a detector in that order. As the ICP-MS apparatus, for example, an ICP mass spectrometer manufactured by PerkinElmer Japan Ltd. can be used, but the apparatus is not limited to a specific instrument. By using such an instrument, steps (1) to (4) can be performed fully automatically without human intervention.

(1) Ionization step In step (1), the sample solution is atomized and introduced into a plasma ion source for ionization. The amount of sample solution introduced in this step varies depending on the ICP-MS instrument used and can be appropriately determined by a person skilled in the art according to the instruction manual of the ICP-MS instrument. For example, it can be 10 to 5000 μL per measurement, and preferably 400 to 3000 μL.

In this process, argon plasma is generated in the ionization section of the ICP-MS instrument to ionize the elements in the sample solution. This generates an ion group consisting of multiple types of ions, including the target substance, Cl-36 ions.

(2) Step to generate ClO oxide ions with mass number 52 In step (2), the ion group obtained in step (1) is brought into contact with oxygen gas. In this step, the CRC of the ICP-MS instrument is set to reaction mode, and oxygen gas is supplied to the CRC under conditions that allow the ions contained in the ion group, especially Cl-36 ions, to react with oxygen gas. Conditions under which Cl-36 ions can react with oxygen gas can be achieved by using high-purity oxygen as the oxygen gas and introducing the oxygen gas into the CRC at a flow rate of 0.2 to 1.6 mL/min.

This process generates ClO-52 oxide ions with a mass number of 52 in the CRC if Cl-36 is present in the sample solution. If Cl-35 or Cl-37 is present in the sample solution, ClO-51 oxide ions and ClO-53 oxide ions are also generated.

(3) Step to remove ions with mass numbers other than 52 In step (3), the group of ions that may include the ClO-52 oxide ions obtained in step (2) is introduced into a quadrupole mass filter. The quadrupole mass filter can remove ions with mass numbers other than 52.

This process removes ClO-51 oxide ions and ClO-53 oxide ions that may be generated from chlorine isotopes with different mass numbers.

(4) Step to detect the signal of ions with mass number 52 In step (4), the signal of ions with mass number 52 that passed through the quadrupole mass filter without being removed in step (3) is counted. This allows Cl-36 to be detected as ClO-52 oxide ions if it is present in the sample. Detection can be performed, for example, based on the peak waveform of ions with mass number 52 in a plot with measurement time on the x-axis and ion count per unit time on the y-axis, or more precisely, based on the peak pulse height.

Therefore, the presence or absence of a peak can be used to confirm the presence or absence of ClO-52 oxide ions and detect the presence or absence of Cl-36. Furthermore, Cl-36 can be quantified based on the peak waveform. According to one embodiment, Cl-36 can be quantified based on the maximum peak height. According to another embodiment, Cl-36 can be quantified based on the integrated peak area. From the viewpoint of accuracy of quantification, the quantification method based on the integrated peak area is more preferable. In either embodiment, for multiple samples with known concentrations, such as a standard source of Cl-36, the maximum peak height or integrated peak area can be obtained using the method of this embodiment, and a calibration curve can be created based on these values to quantify Cl-36.

According to one embodiment of the present invention, by performing steps (1) to (4) described above, Cl-36 can be detected separately from isotopes and isobars. In particular, it becomes possible to quantify Cl-36 more simply and quickly compared to conventional methods for measuring beta rays.

According to another embodiment of the present invention, a step of removing interfering elements from the sample solution by ion chromatography (IC) may be included before steps (1) to (4) described above. In this specification, this step is also referred to as the IC pretreatment step.

The IC pretreatment process can be carried out using an ion chromatography apparatus (IC apparatus) equipped with a column capable of selectively extracting chloride ions. Such IC apparatuses and columns capable of selectively extracting chloride ions are commercially available, and any commercially available product can be used. In one embodiment, the IC apparatus may mainly consist of a liquid delivery unit equipped with a pump for sending the eluent to the apparatus, an introduction unit for introducing the sample solution into the apparatus, a separation unit equipped with a guard column and a separation column, and a suppressor unit for separating the mobile phase. In this embodiment, it is preferable to further include a liquid delivery means for sending the sample solution, from which interfering elements have been removed, to the sample introduction unit of the ICP-MS apparatus carrying out steps (1) to (4).

The IC pretreatment process can be performed by introducing the sample solution into the IC apparatus. When the sample solution is introduced into the IC apparatus column, chloride ions are initially held in the separation column, but are then carried along by the eluent and move within the column. Because the rate of movement within the column differs depending on the ion's valency, ionic radius, and hydrophobicity, chloride ions are separated and concentrated from other ions as they pass through the column. The rate of liquid delivery can be appropriately determined according to the apparatus's instruction manual. Note that the term "chloride ions" here includes all Cl-35, Cl-36, and Cl-37 ions. Since the IC apparatus cannot distinguish between chlorine isotopes such as Cl-35, Cl-36, and Cl-37, the sample solution after the IC pretreatment process mainly contains Cl-35, Cl-36, and Cl-37 ions.

Next, the sample solution that has undergone the IC pretreatment process is sent to the sample introduction section of the ICP-MS instrument, and steps (1) to (4) are performed as described above. The IC pretreatment process removes interfering elements, and the oxide ions generated in step (3) are substantially limited to ClO-51 oxide ions, ClO-52 oxide ions, and ClO-53 oxide ions. Since the ClO-51 and ClO-53 oxide ions can be removed in the subsequent step (3), it becomes possible to detect the ClO-52 oxide ion with high accuracy in step (4).

According to yet another embodiment of the present invention, a step of concentrating Cl-36 by applying the sample solution to a concentration column can be performed before the IC pretreatment step, after the IC pretreatment step, or before step (1) if the IC pretreatment step is not performed. Hereinafter, this step will be referred to as the concentration step.

The concentration column used in the concentration step may be a resin column capable of extracting Cl-36. For example, TRISKEM INTERNATIONAL's CL resin for extraction chromatography can be used, but the method is not limited to a specific concentration column. The procedure when using TRISKEM INTERNATIONAL's CL resin can be carried out in more detail by referring, for example, to the method described in the Journal of Radioanalytical and Nuclear Chemistry, volume 286, pages 539-546 (2010).

In the concentration process, chlorine is extracted from the sample solution, allowing it to be concentrated approximately 300 times. Cl-35, Cl-36, Cl-37, and other elements that may be present in the sample solution are adsorbed onto the concentration column.

By performing a concentration process, chlorine can be selectively extracted from the sample solution, and the sample solution with reduced sulfur isobars can be introduced into an IC or ICP-MS instrument. This allows for more accurate separation of interfering elements in the IC instrument. Furthermore, in the ICP-MS instrument, it becomes possible to selectively generate and count only ClO oxide ions as ions with a mass number of 52.

The present invention will be described in more detail below using examples. However, the following examples are not limiting to the present invention. In the following examples, the operations were carried out using a PerkinElmer NexION 2000 as the ICP-MS apparatus and a Thermo Fisher (formerly Dionex) DX-800 as the IC apparatus.

1. Examination of Isotopes and Isobatteries The target isotope, Cl-36, has isobatteries S-36 and Ar-36. Since ICP-MS uses Ar plasma to ionize atoms, interference from Ar-36 is possible. Furthermore, the isobattery ^35ClH , produced from the chlorine isotope Cl-35, may interfere with the detection of Cl-36. We investigated methods for removing these isotopes.

2. Investigation of Collision Gases and Reaction Gases We investigated whether the effects of isobars could be mitigated by using collision gases (He) and reaction gases ( _O₂ , _NH₃ , _CH₄ ). Collision gases can be used in CRC to eliminate interference by utilizing the difference in ionization potential and causing collisions with ions to be removed to convert them into nonions. Reaction gases can be used in CRC to react with ions to be detected and detect them as oxide ions.

Using stable isotopes of chlorine Cl-35 and Cl-37, stable isotope of sulfur S-36, and ultrapure water, the changes in counts for mass numbers 35, 36, and 37, and for mass numbers 51, 52, and 53 were measured using collision gas (He) and reaction gas ( _O₂ , _NH₃ , _CH₄ ). The detection feasibility of Cl-36 with mass number 36 or ClO-52 oxide ions with mass number 52 was investigated. Specifically, the experiment was conducted under the following conditions: stable isotope chlorine at 100 ppm, stable isotope sulfur at 100 ppm, collision gas (He) supply rate of 0–5.0 mL/min, and reaction gas ( _O₂ , _NH₃ , _CH₄ ) supply rate of 0–1.6 mL/min. The results are shown in Tables 1 and 2. In the table, for mass numbers 35, 37, 51, and 53, a count of approximately two orders of magnitude larger than the count of stable isotope chlorine compared to the count of stable isotope sulfur and ultrapure water was marked with ○, a count difference of less than one order of magnitude was marked with △, and no count difference was marked with ×. For mass numbers 36 and 52, a count of ○ was marked if the count of stable isotope chlorine, stable isotope sulfur, and ultrapure water was low, there was no count difference, and the count could be reduced by adjusting the gas flow rate, a count could be reduced by adjusting the gas flow rate was marked with △, and a × was marked if the count was high and could not be detected.

Based on the results in Tables 1 and 2, it was determined that by using oxygen gas as a reaction gas, the difference in reactivity between elements is utilized to react with the target element, Cl, to form oxide ions (ClO, mass number 52), thereby enabling highly sensitive measurement of Cl-36.

For a sample solution with a stable chlorine isotope concentration of 100 ppm, the relationship between the oxygen gas flow rate and the ion counts of mass numbers 35, 36, and 37 was investigated when oxygen gas was used as the reaction gas.

The measurement results are shown in Figures 1-3, respectively. For mass numbers 35 and 37, the count decreased as oxygen gas was mixed and the flow rate increased. For mass number 35, there was a difference between ultrapure water and Cl at a low oxygen gas flow rate of 0.2 mL/min, but above that, the difference between Cl and ultrapure water disappeared, indicating that highly sensitive detection of Cl-36 is unlikely. Chlorine for mass number 36 showed no difference with a 100 ppm sulfur solution, indicating it was unaffected. Due to the background increase caused by Ar-36, it was determined that highly sensitive analysis of Cl-36 is difficult.

For a sample solution with a stable chlorine isotope concentration of 100 ppm, the relationship between oxygen gas flow rate and the ion counts of mass number 51, mass number 52, and mass number 53 was investigated when oxygen gas was used as the reaction gas.

The measurement results are shown in Figures 4-6, respectively. For mass numbers 51 and 53, an increase in count was observed in a 100 ppm Cl solution compared to a 100 ppm sulfur solution or ultrapure water solution. This reaction with oxygen gas generates ClO ions. For mass number 52, increasing the amount of oxygen gas decreased the count, reducing the background count. For mass numbers 51 and 53, a larger difference in count between 100 ppm Cl and ultrapure water is better, and a lower count for ultrapure water is also better. For mass number 52, a lower count is better (reducing the influence of Ar-36), and it is better if there is no difference in count between ultrapure water and 100 ppm sulfur (not affected by S-36). Also, a smaller difference in count between 100 ppm Cl and ultrapure water is better.

3. Examination of Calibration Curve Next, the source dilution of Cl-36 as shown in Table 3 below, along with Cl-35 and Cl-37, which are stable isotopes of known concentration, were introduced into the ICP-MS instrument as sample solutions. High-purity oxygen gas was injected as the reaction gas at a rate of 1.0 mL/min, and ion counts with mass numbers 51, 52, and 53 were obtained, respectively.

Calibration curves created based on measurement results from an ICP-MS instrument are shown in Figures 7 to 9. The ion count measurement value cps (counts per second) shown on the vertical axis of each figure is a value based on the maximum peak height. The calibration curve for Cl-36 detected with mass number 52 had a large variability, with ^R² = 0.8342.

4. Investigation of IC-ICP-MS Method Since many ions are present in the sample solution, we investigated the pretreatment of Cl-36 by ion chromatography (IC) to remove coexisting ions. An IC device was installed before the ICP-MS instrument, and the amount of sample solution introduced into the ICP-MS instrument was investigated. In this experiment, a sample solution containing 0.11 ppm of Cl-35, after interfering elements had been removed by the IC device, was introduced into the ICP-MS instrument. _O2 gas was supplied to the CRC at an injection rate of 1.0 mL/min as the reaction gas, and ions with mass numbers 51 and 52 that passed through the quadrupole mass filter were counted. The ion counts for mass numbers 51 and 52 were plotted against the measurement time. The results are shown in Figures 10 and 11.

Figure 10 shows the plot results for a sample injection volume of 50 μL, and Figure 11 shows the plot results for a sample injection volume of 500 μL. For an injection volume of 50 μL, a peak for ion count with mass number 51 was observed at 3.74 min (the peak enclosed by the dashed line in Figure 10), and for an injection volume of 500 μL, it was observed at 3.80 min (the peak enclosed by the short dashed line in Figure 11). Comparing Figures 10 and 11, it was found that sensitivity increased with increasing injection volume, and that changing the injection volume did not affect other aspects of the ion count. Referring to Figure 11, a baseline change was observed around 1 min (the area enclosed by the long dashed line) for ion count with mass number 52. Similar results were observed with the IC detector (not shown). With the IC detector, a Cl peak was obtained at 3.6 min. The peak of 0.11 ppm Cl-35 (mass 51) detected by ICP-MS was detected by the IC detector approximately 10 seconds later.

Next, 500 μL of a sample solution containing 190 Bq/mL of Cl-36 was introduced into an IC instrument, and the sample solution from which interfering elements had been removed in the IC instrument was introduced into an ICP-MS instrument. _O2 gas was supplied to the CRC as a reaction gas at an injection rate of 1.0 mL/min, and ions with mass numbers 51, 52, and 53 that passed through the quadrupole mass filter were counted. Figure 12 shows the results of plotting the ion counts for mass numbers 51, 52, and 53 against the measurement time, and Figure 13 is a magnified view of the peaks in Figure 12 from 2 to 4 minutes. Under the same conditions as in the previous experiment, a peak indicating the detection of Cl-36 was detected at mass number 52.

A calibration curve was created by measuring Cl-36 solutions of known concentration using IC-ICP-MS. _O2 gas was supplied to the CRC at an injection rate of 1.0 mL/min as the reaction gas, and the count of ions with mass number 52 that passed through the quadrupole mass filter was plotted against the measurement time. From the plot results, peak height (maximum value) and peak area (integrated value) were obtained, and calibration curves were created based on each. Figure 14 shows the calibration curve based on peak height, and Figure 15 shows the calibration curve based on peak area. The calibration curve based on peak area showed low variability with ^R² = 0.9999. The calibration curve based on peak area was particularly advantageous in that it could detect Cl-36 even at low concentrations.

4. Comparison of Accuracy with Conventional Methods A simulated sample was prepared using a Cl-36 standard source, and the measurement results of the ICP-MS method according to the present invention were compared with those of the conventional method (a conventional method using beta rays) using a liquid scintillation counter (LSC). The calibration curve used was based on the peak area obtained in Figure 15. The results are shown in Table 4. The ICP-MS method was performed twice, and the results for each are shown. When a simulated sample of 163 Bq/mL was measured, the conventional method and the ICP-MS method according to the present invention yielded almost equivalent results.

5. Comparison of required time with conventional methods The time required for analysis using the IC-ICP-MS method according to the present invention was compared with that of the conventional method when 50 g of a material suspected to have Cl-36 attached was washed with 100 mL of etching solution (sulfuric acid) and the resulting liquid was used as the sample solution.

In conventional methods, distillation of the sample solution and preparation of the absorption solution take approximately one day, gamma ray checking, drying, and dissolution take approximately one day, heating, aging, filtration, drying, and recovery rate measurement take approximately one day, and measurement using a liquid scintillation counter takes approximately two days. Therefore, obtaining analytical results for a 100 mL sample requires three days for pretreatment and two days for measurement, totaling approximately five days (120 hours). All of these operations must be performed within a radiation-controlled area.

On the other hand, in the IC-ICP-MS method of the present invention, column concentration using the IC apparatus takes approximately 2.5 hours. More specifically, assuming that the sample is passed through with water (100 mL), washed with washing solution (10 mL), and Cl-36 is eluted (5 mL) at a rate of 0.8 mL/min, this takes approximately 2.5 hours. Then, measuring the obtained sample solution by ICP-MS requires 13 minutes per sample, for a total of approximately 3 hours. Therefore, according to the present invention, it is possible to quantify Cl-36 with the same accuracy as the conventional method, in approximately 1/40th of the time required.

Therefore, by using the ICP-MS method or IC-ICP-MS method according to the present invention, it is possible to quantify Cl-36 more rapidly compared to conventional methods.

Claims (9)

The process involves introducing the sample solution into a plasma ion source and ionizing it,
The process involves contacting the group of ions obtained in the ionization process with oxygen gas to produce ClO oxide ions with a mass number of 52,
In a quadrupole mass filter, the process involves removing ions with mass numbers other than 52,
A method for analyzing chlorine with a mass number of 36, comprising the step of detecting the signal of an ion with a mass number of 52 that has passed through the quadrupole mass filter. The method according to claim 1, further comprising the step of removing interfering elements from the sample solution using an ion chromatography apparatus before the ionization step. The method according to claim 1, wherein the step of detecting the signal of the ion with mass number 52 is a step of detecting chlorine with mass number 36 based on the peak waveform of the ion count with mass number 52. The method according to claim 2, wherein the step of detecting the signal of the ion with mass number 52 is a step of detecting chlorine with mass number 36 based on the peak waveform of the ion count with mass number 52. The method according to claim 3, wherein the step of detecting chlorine with mass number 36 based on the peak waveform of the ion count is a step of quantifying chlorine with mass number 36 based on the integrated value of the peak area of the ion count with mass number 52. The method according to claim 4, wherein the step of detecting chlorine with mass number 36 based on the peak waveform of the ion count is a step of quantifying chlorine with mass number 36 based on the integrated value of the peak area of the ion count with mass number 52. The method according to claim 3, wherein the step of detecting chlorine with mass number 36 based on the peak waveform of the ion count is a step of quantifying chlorine with mass number 36 based on the maximum peak height of the ion count with mass number 52. The method according to claim 4, wherein the step of detecting chlorine with mass number 36 based on the peak waveform of the ion count is a step of quantifying chlorine with mass number 36 based on the maximum peak height of the ion count with mass number 52. The method according to any one of claims 2, 4, 6, or 8, further comprising the step of applying the sample solution to a concentration column capable of specifically extracting chlorine, and concentrating the chlorine, before the ionization step or the step of introducing it into an ion chromatography apparatus to remove interfering elements .