JPH0451800B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for fractionating strontium, and particularly to a method suitable for separating yttrium-90 produced from strontium and strontium-90.

[Background of the invention]

Strontium-89 and strontium-90 are β-ray emitters, so when measuring these nuclides, strontium is isolated from a sample as a certain salt and its radioactivity is measured. To distinguish between strontium-89 and strontium-90, strontium is isolated and the total radioactivity of strontium-89 and strontium-90 is measured, and then yttrium-90, which is produced by the decay of strontium-90, is separated and emitted. The concentration of strontium-90 is determined from this radioactivity concentration, and this is calculated as strontium-89 and strontium-90.
Strontium-89 is calculated by subtracting it from the total radioactivity.

Strontium can be isolated using methods used in general chemical analysis, such as ion exchange, solvent extraction, and precipitation separation, but the ion exchange method is suitable for automating preparative separation.

To separate strontium from a mixed solution of strontium and other cations using the ion exchange method, these mixed solutions are passed through a cation exchange resin column, and then an appropriate eluent is passed through the column to separate each ion from the resin. Since they are separated and eluted in descending order of affinity, it is only necessary to separate the fractions when strontium is eluted. Next, when this solution is left to reach radioactive equilibrium (Sr-90 → Y-90 for two weeks), yttrium, which corresponds to strontium-90,
Since strontium-90 is generated, the concentrations of strontium-89 and strontium-90 can be determined from the radioactivity concentration of each by separating strontium and yttrium. However, in order to separate strontium and yttrium from a solution separated using an eluent using an ion exchange method after radiative equilibrium, it is necessary to increase the capacity of the column in accordance with the amount of sample. That is, the amount of the strontium and yttrium fraction is considerably larger than the sample amount due to the contamination with the eluent, which has the disadvantage that the analysis time becomes longer and the concentrations of strontium and yttrium become lower.

Therefore, if the separation of strontium and its coexisting components and the separation of yttrium-90 produced from strontium-90 can be performed in a continuous operation, it will be possible to speed up and automate the preparative separation.

[Purpose of the invention]

An object of the present invention is to provide a method for preparatively separating strontium in which the separation of strontium from a mixed component and the separation of yttrium produced by the decay of strontium-90 can be performed in a continuous operation. .

[Summary of the invention]

A feature of the present invention is that an eluent is continuously passed through one of two separation columns installed in parallel, and then strontium and other heavy metal ions are mixed in the eluent flow path on the upstream side of the separation column. A certain amount of the solution is added, and just before strontium elutes in one of the separation columns, the eluent is flowed to the other separation column, and the eluent is allowed to stand still in this state, so that strontium-90 and yttrium-90 reach radiation equilibrium. After that, the pressure in the piping system was brought to a steady state again, and the yttrium carrier solution was added to the eluent flow path upstream of the separation column, and at the same time, eluent flow paths were provided on one side of the separation column and downstream of this separation column. The purpose is to flow the yttrium and strontium into a separation column and separate the yttrium and strontium eluted from the separation column provided downstream.

[Embodiments of the invention]

The reaction in which yttrium-90 is produced by the decay of strontium-90 proceeds in all cases regardless of the state of strontium present, so this reaction is carried out in an ion exchange resin column to separate strontium from coexisting components. It is possible to separate yttrium-90 produced from strontium-90 and strontium-90 using the same column. That is, after adding a certain amount of a mixed solution of strontium and metal ions to an ion-exchange resin column, the eluent was flowed to collect cobalt, manganese, zinc, yttrium,
Each ion such as calcium and magnesium forms a complex with the complexing agent in the eluent so that each ion is eluted earlier than strontium, and the flow of the eluent is stopped just before strontium is eluted from the resin to remove strontium. After allowing 90 to reach radioactive equilibrium, when the eluent is run again, yttrium, which was initially generated from strontium-90, is
Since 90 is eluted, and then strontium is eluted, by separating each of these, it becomes possible to separate strontium and yttrium in a continuous operation. In reality, if we keep strontium at the bottom of the separation column and then run the eluent through it again two weeks later, the pressure inside the column will fluctuate and the detector signal will show an abnormal value, so two columns are connected in parallel. However, if the eluent is passed through one column and the strontium is kept in the other column, and after radiation equilibrium, the eluent is passed through the column where the strontium is kept, a stable signal can be obtained from the detector.

An embodiment of the present invention will be described below with reference to FIG.

The eluent is continuously sent by an eluent storage tank 1 and a pump 2 to sample injection valves 3A and 3B, one of separation columns 4A and 4B, separation column selection valves 5A and 5B, a detector 6, and a fraction collector 7. It will be done. When a fixed amount of a mixed solution of strontium and other heavy metal ions is added from the sample injection valve 3A, the sample is pushed by the eluent and passes through one of the separation columns 4A and 4B filled with cation exchange resin. However, within the separation column 4A, each ion is eluted in descending order of affinity with the resin, passes through the separation column selection valves 5A and 5B and the detector 6, and is sent to the fraction collector 7. The time taken for each ion to reach the detector 6 after the sample is added is called a retention time, and exhibits a constant value under the same conditions. Since heavy metal ions, calcium, and magnesium elute earlier than strontium, the eluent is caused to flow toward the separation column 4B by the separation column selection valve 5A just before strontium elutes.
Leave this condition for two weeks, and after strontium-90 and yttrium-90 reach radiation equilibrium (stop pump 2 while it is left), start pump 2 again to bring the pressure in the piping system to a steady state. Make it. Next, the yttrium carrier solution is added from the sample injection valve 3B, and at the same time the separation column selection valve 5A is
and 5B to direct the eluent flow path to separation column 4.
When flowing toward A and 4C, first yttrium-90 generated from strontium-90 elutes from separation column 4C together with the added yttrium, and then strontium elutes, so these components are eluted. This is monitored by a detector 6, and yttrium and strontium are fractionated by a fraction collector 7. A precipitate of yttrium or strontium is formed from each floction, and β-rays are measured from each precipitate to determine strontium-89 and strontium-90. According to this example, by connecting two separation columns in parallel, the internal pressures of the two separation columns become the same, so the pressure change when switching the eluent flow path to the separation columns is reduced. Therefore, generation of false peaks on the detector 6 can be prevented. Therefore, since the eluted components can be monitored and the collection amount can be accurately determined, it is possible to perform the fractionation of yttrium and strontium in a continuous series of operations.

FIG. 2 is a diagram showing a measurement example in the embodiment of FIG. 1. Iron (), cobalt (), copper (), manganese (), magnesium (), calcium () and strontium () respectively
This is a chromatogram when 0.5 ml of a 50 ppm mixed solution was added. It can be seen that strontium and other components can be separated and that strontium can be fractionated. The experimental conditions were that the separation column was 6φ x 80
mm, the eluent was a mixed solution of 1 mol/lactic acid and 0.5 mol/ammonium chloride (PH5), the flow rate of the eluent was 1 ml/min, and the detector was a coulometry monitor.

FIG. 3 is a chromatogram obtained using a conventional apparatus (method), that is, when there is only one separation column. The solid line shows a solution containing 250 and 750 ppm of yttrium and strontium, respectively, added from the center of the separation column, left for two weeks, and then an eluent was run to elute yttrium and strontium. The yttrium peak and baseline are distorted, making it difficult to determine the preparative time for yttrium and strontium. Note that the experimental conditions were the same as in FIG. 2.

FIG. 4 is a chromatogram showing the effect of the embodiment of the present invention shown in FIG. It can be seen that the yttrium and strontium peaks and the baseline are clearly distinguished. The experimental conditions are the third
This is the same as the case shown in the figure.

〔Effect of the invention〕

According to the present invention, the separation of strontium from the mixed components and the separation of yttrium produced by the decay of strontium-90 can be performed in a continuous series of operations, thus significantly saving labor in measurement. This has the effect of making it possible to achieve the following.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing one embodiment of the present invention, Figure 2 is a system diagram showing an embodiment of the present invention.
The figure is a chromatogram of a mixed solution, FIG. 3 is a chromatogram using a conventional device, and FIG. 4 is a chromatogram showing the effects of the present invention. 1... Eluent storage tank, 2... Pump, 3A, 3B
...Sample injection valve (sample injection means), 4A, 4
B, 4C... Separation column, 5A, 5B... Separation column selection valve, 6... Detector, 7... Fraction collector.

Claims (1)

[Claims] 1. The eluent is continuously passed through one of two separation columns installed in parallel, and then a fixed amount of a mixed solution of strontium and other heavy metal ions is added into the eluent flow path on the upstream side of the separation column. Immediately before strontium elutes in one of the separation columns, the eluent is flowed to the other separation column, left to stand still in this state, and after strontium-90 and yttrium-90 reach radiation equilibrium, the piping system is re-entered. the pressure in the chamber is kept at a steady state, and a yttrium carrier solution is added into the eluent flow path upstream of the separation column, and at the same time the eluent flow path is caused to flow through one of the separation columns and a separation column provided downstream of this separation column, A method for separating strontium, which comprises separating yttrium and strontium eluted from a separation column provided downstream.