JPS6041737B2 - Boron isotope ratio measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the boron isotope ratio of an inorganic boron compound, in particular to a method for measuring the boron isotope ratio of an inorganic boron compound, particularly for use as a moderator in nuclear reactors.

This invention relates to a method for measuring the isotope ratio of IOB and IIB contained in C. Traditionally, the method for measuring boron isotope ratios is (
There are two methods: 1) using a surface ionization mass spectrometer; and (2) introducing a sample as BF3 gas into a mass spectrometer, ionizing the BF3 gas by an electron impact method, and measuring the generated BF2* ions.

Method (1) Samples were prepared using sodium tetraborate (No.

After chemical treatment to the form of B, O,), the number 1
A small amount of Na2B was applied on the filament, and then the filament was passed through an electric current and dried to dryness.
, O, is ionized using a surface ionization mass spectrometer. mark. This is a method of measuring ions.
This method has almost no memory effect and has high measurement accuracy, but the equipment is large and expensive, and it requires uranium octoxide (UO) as sample pretreatment.
There are several drawbacks, such as the difficulty in absorbing boric acid into a NaOH solution in a 1:1 ratio of Na, B, O, and aqueous solutions onto the filament. In method (2), the sample is BF.

After preparing the gas, put it into the mass spectrometer and BF. BF produced by ionizing gas by electron impact method. This is a method of measuring ions. This method has the drawback of using a relatively large amount of BF3, which is a corrosive gas, which causes a memory effect, which reduces measurement accuracy.

In order to improve this problem, methods have been developed to clean the sample introduction system and ion source by flowing BCI'3 gas before and after measurement, and to improve the sample introduction/introduction device. Moreover, sufficient effects were not obtained. The present invention
The aim is to solve these shortcomings by providing a simple method for measuring boron isotope ratios in a short time and with relatively high accuracy using gas chromatography direct-coupled mass spectrometers, which have become rapidly popular in recent years. It is something to do.

In measuring the isotope ratio of boron in an inorganic boron compound using a mass spectrometer, the present invention processes the inorganic boron compound to form boric acid or boron oxide, and then combines these with cobalt, antimony, mercury, and silver. Put at least one fluoride selected from
0-3w! Reduce the pressure to NHy and increase the temperature to 90-200℃
BF3 gas is continuously introduced into a mass spectrometer while generating it, ionized, and the ions are measured by an ion detector.

The present invention will be further explained in detail below.

The inorganic boron compound that can be measured in the present invention is not particularly limited, but specific examples include sintered pellets of B4Cl ferroboron and alumina boron carbide.

These are melted in an alkali and used as a sample as boric acid or boron oxide, but among these, boric acid is preferred from the viewpoint of ease of operation. In addition, as inorganic fluoride, COF3,S
Examples include bF5, SbF3, Hf2, HoshiF2, AgF'2, and these can be used alone or in combination of two or more. Generally, BF3 gas is prepared by heating a boron compound and fluoride at 115 to 190'C under atmospheric pressure.
Although it is known to collect F3 gas (U.S. Pat. No. 2,622,014), the present invention is capable of collecting F3 gas in a sealed container.
Heat while drawing a vacuum to ~10-3TWLHy,
The feature is that while BF3 gas is generated, it is simultaneously introduced into a mass spectrometer, ionized, and measured. In the present invention, BF3 gas is gradually generated while heating, so it is difficult to quantify it, but it is possible to measure using an extremely small amount of BF3 gas.

Boron ions (108F2+, 11
Two BFs are multi-type ion detectors (MultipIeIOn).
DetectOr) to record on the oscillograph or pen recorder. Record. In the present invention, a multi-species ion detector that is excellent in detecting boron ions is used. Since the multi-species ion detector has excellent discrimination ability for other species ions, the noise level is suppressed and the S/N ratio is large. High・
Sensitive detection becomes possible. The obtained value is substituted into the formula described later to determine the isotope ratio. The present invention will be explained in more detail below.

Although an example using boric acid and cobalt trifluoride as samples will be explained, the present invention is not limited to this. The gas chromatography direct-coupled mass spectrometer used in the present invention is manufactured by, for example, Co., Ltd.
Shimadzu's RLKB9O hammer type is mentioned. This is a single focusing type with a radius of curvature of 20 cm and a 60-shape deflection, and the ion source is an electron impact type using a rhenium filament.
To prepare a mass sample, approximately 0.05 to 0.1y of B4C is placed in a platinum crucible, and alkali melting is performed with 10 times the amount of Na2cO3.

After several hours, B4C becomes sodium tetraborate (Na2B4
O7).

This aqueous solution is passed through a column packed with a cation exchange resin and finally recovered as an aqueous solution of boric acid, and a portion of this aqueous solution is concentrated to obtain a white powder of boric acid (H3BO3). The obtained H3BO3 number Mg and cobalt trifluoride (
COF3) and several Mg of COF3) are placed in a container, mixed well, and then the container is connected to the separator inlet. Figure 1 shows an example of a sample container (U.S. Corning Glass Co., Ltd. registered trademark: 1P.y
r′ExJ), put the sample and COF 3 into a container 1 with an internal volume of about 20 cc and stoppered with a silicone rubber stopper 2, and
As shown in the figure, it is connected to the separator part 4 with a stainless steel cap nut 5 to seal it.

Next, while keeping the valve between the separator and the ion source closed, use the rotary pump and oil diffusion pump to 10-1 to 10-3? While drawing the vacuum of Hy, 95~
Heat and degas the sample container at a temperature of 100'C for 7-8 minutes.

After that, open the valve and heat to 150° C. at a temperature increase rate of 3 to 5° C/Min.

The generation of BF3 gas increases with increasing temperature, and reaches approximately 120'
The peak is indicated by C. This reaction formula can be considered as follows. state.

BO3+2C0F3 2BF3↑+CO2O3+31
(The degree of vacuum inside the ion source is approximately 1 under operating conditions of 20 or more.
It is 0-1T0rr or less. In order to minimize factors such as memory effects caused by the corrosivity of BF3 gas, which are negative factors in measurement accuracy, it is necessary that the amount of BF3 introduced into the ion source be as small as possible.

In actual measurement, even under this condition, there is a margin of 103 to 104 in the measurement range of the detection section of the multi-species ion detector. However, in order to quickly and reproducibly weigh solid samples, several M
Considering that g is the limit, the present invention uses several M for one measurement.
A sample of g was used.

A pen recorder with high linearity accuracy was used as the recorder.

The obtained measurement chart is shown in FIG. Figure 3 shows 10
It consists of curve 1 for BF2 ion, curve 1 for BF2 ion, and base line 2, and shows the relationship between each ion intensity and time or temperature.

Further, A indicates the height from the base line ■ to the peak P1 of the curve 1, and B indicates the height from the base line ■ to the peak P2 of the curve ■. FIG. 4 is a measurement chart of only COF3.

It consists of curve 1 with mass number 48, curve 2 with mass number 49, and base line 3, where x is the height from base line 3 to peak Px of curve 1, and Y is the height from base line 3 to peak Py of curve 2. Show that. To manually calculate the boron isotope ratio, use calipers to find each peak, and substitute the obtained values into the following formula.

A: Peak height of 10BF2 ion B: Peak height of 11BF2 ion You can guess the average value.

NatiOTlaIBure used as standard sample
auOfSt2indards (7) Standard
Beference Material 95l and 952
The 10B concentration of is 19.827±0.013at0mic
% and 94.949±0.005at0mic%.

As a result of selecting 10B concentration B4C as a sample and performing mass spectrometry or consistent measurement, a measurement accuracy of 0.14% is obtained at n=10.

An ordinary pen recorder was used as the recorder, and the height of the peak was determined using a caliper, so the effective figures of the analytical values were three digits. To calculate the boron isotope ratio using a microcomputer, the output of the multi-species ion detector is A
/D conversion, input it into a microcomputer digital interface at arbitrary intervals, perform the calculation shown in equation (1), and output it to a printer.

The most important thing during the measurement is the matching of each ion (the degree of matching of the accelerating voltage to the ion), but this operation must be performed before and after the peak, and when the mass numbers are 48 and 4.
The blank test value of No. 9 was obtained by measuring COF3 several times.

As explained above, the present invention chemically treats an inorganic boron compound such as B4C to convert it into H3BO3 or B2O3, and reacts it with a fluoride reagent such as COF3, SbF5, HgF2, AgF'2, etc. It is a method that immediately ionizes a very small amount of BF3 and measures the boron isotope ratio, and there are no particular restrictions on the type of analyzer.
Any device may be used as long as it has an appropriate opening that can heat the sample container.

Using an easy-to-operate gas chromatography direct-coupled mass spectrometer, boron isotope ratios can be measured quickly and accurately. The present invention will be described in more detail below with reference to Examples.

Example 1 Sample preparation was carried out using B4CO. ly into a platinum crucible, and add Na2CO3l. 2y was added to perform alkali melting. After cooling, it was dissolved in water, passed through a cation exchange resin, and the resulting liquid was concentrated to obtain platinum powder of boric acid. Next, put 5 m9 of this boric acid and 38 m COF into a sample container.
9 was added and the mixture was plugged with silicone rubber, mixed thoroughly, and attached to the separator inlet of a mass spectrometer using a stainless steel cap nut.

After degassing 5 to 1 particles at 95°C, the temperature was raised to 150°C at 5°C/min to generate BF3 gas, and immediately MIZ481O
The BF2+ ion and the MlZ49llBF2+ ion were captured and the boron isotope ratio was determined using a microcomputer.

Note that NBS (7) SRM-1 was used as a standard sample.
The measurement result was 10B19.8at0m% (average value).

Example 2 Concentrated B4C was measured in the same manner as in Example 1, and the boron isotope ratio was determined by hand calculation.

The results are shown in the table. As a result, it was found from the results of the third and fourth tests that the influence of memory effects can be almost ignored. Note that SRM-2 was used as the standard sample at this time.
Example 3 For ferroboron, sample 0.3g, Na2C0
Take 3y of 3/K2CO3=1ha in a platinum crucible,
It was treated in the same manner as in Example 1.

The measurement result is 10B19. &1t0m% (average value)
It was hot. Example 4 For the B4C-Ae2O3 sintered body, samples 1.3y and 7y of N2/K2CO3=1 were placed in a platinum crucible, thoroughly mixed, and placed in an electric furnace for 50'CXl.
After fully melting the sample at 700°C for 1 hour and at 1000°C for 4 hours, it was treated in the same manner as in Example 1. Ta.

: This measurement result is 10B19.6at0m% (average value)
It was so hot.

Example 5 The same procedure as in Example 1 was carried out using SbF5, HgF'2, and AgF'2 in place of C0F3, and the same results as in Example 1 were obtained.

[Brief explanation of the drawing]

Fig. 1 is a side view of a sample container used in an example of the present invention, Fig. 2 is a side view showing the connection of the sample container, and Figs. 3 and 4 are lines showing the relationship between ionic strength and time or temperature. It is a diagram. 1...sample container, 2...silicone rubber stopper, 3...
Sample and reagent, 4... Separator part, 5... Cap nut.

Claims (1)

[Claims] 1. When measuring the isotopic ratio of boron in an inorganic boron compound using a mass spectrometer, the inorganic boron compound is processed to form boric acid or boron oxide, and then these are combined with cobalt, antimony, mercury, and silver. After putting at least one type of fluoride in a sealed container and attaching the container to a mass spectrometer, the pressure of the container is set to 10^-^1 to 10^.
- It is characterized by reducing the pressure to 3 mmHg and heating it to a temperature of 90 to 200 degrees Celsius, continuously introducing it into a mass spectrometer while generating BF_3 gas, ionizing it, and measuring the ions with an ion detector. A method for measuring boron isotope ratios.