CN103257147A - 232Method for measuring U - Google Patents

Abstract

The invention belongs to the technical field of analytical chemistry and discloses a method for preparing a high-purity gold-silver-copper alloy²³²Method for measuring U. The method comprises the following steps: (1) dissolving a uranium sample by using nitric acid, and electroplating to prepare an alpha source of the uranium sample; (2) measuring alpha energy spectrum of alpha source of uranium sample by using alpha spectrometer to obtain²³⁴U、²³⁵U、²³⁶U and²³⁸total count of U N_ZAnd deduction²²⁸After Th contribution²³²Alpha count of U; (3) putting the dissolved uranium sample into a mass spectrometer for analysis²³⁴U、²³⁵U、²³⁶U and²³⁸u accounts for the atomic percent of uranium; (4) calculating the content of uranium in the uranium sample according to the formula (7)²³²The content of U. The method is simple to operate and accurate in determination.

Description

232The assay method of U

Technical field

The invention belongs to technical field of analytical chemistry, be specifically related to ²³²The assay method of U.

Background technology

The isotope of uranium is generally in the uranium sample after the reactor irradiation ²³²U, ²³³U, ²³⁴U, ²³⁵U, ²³⁶U, ²³⁸U.Group's part uranium isotope wherein ²³²U, ²³³U, ²³⁴U, ²³⁶The existence of U and daughter thereof brings irradiation and pollution problem for nuclear fuel cycle and nuclear fuel element manufacturing, has increased the protection difficulty, especially ²³²U, its half life period, energy of height, thermal neutron absorption cross section short, that decay daughter produces were big, were the uranium isotopes of strict restriction during element is made.In the uranium sample after the reactor irradiation of U.S. ASTM standard regulation ²³²The maximum limit value of U is 0.005 μ g/gU.In order accurately to measure in the uranium sample ²³²U, it is the standard test method of ASTM C761-96 that U.S.'s test can have been set up label with materialogy, China also adopting by equivalent ASTM C761-88 has set up nuclear industry standard EJ 727-1992, these two kinds of standards all are to adopt the quality of uranium in the colorimetric method for determining electro-deposition source, use the alpha energy spectrum method to measure the electro-deposition source ²³²The U quality.But the method is comparatively loaded down with trivial details, when determining the quality of uranium in the electro-deposition source, and the curve of need working, and must carry out colorimetric estimation when determining each sedimentary origin quality.

Summary of the invention

The present invention is directed to the problem that above technology exists, proposed a kind of ²³²The assay method of U, this method is simple to operate, measurement is accurate.

The present invention adopts alpha energy spectrum and mass spectrometry to measure after the reactor irradiation in the uranium sample ²³²The content of U.

Measure and to record by alpha energy spectrum ²³⁴U, ²³⁵U, ²³⁶U, ²³⁸Total α counting of U.Because ²³²U discharges two kinds of α particles, and energy is respectively 5.28MeV and 5.32MeV, with ²²⁸The energy of Th is the alpha ray overlaid of 5.34MeV, but can pass through ²²⁸Another energy of Th is the alpha ray deduction of 5.42MeV ²²⁸Th is right ²³²The contribution of U obtains ²³²The counting of U. ²³²After the quality of U can be used and deduct ²³²The α counting of U calculates with its intrinsic specific activity, and its computing formula is as follows:

m ₂₃₂＝A ₂₃₂/α ₂₃₂＝(N _5.3-0.3767·N _5.42)/(t·α ₂₃₂·Ef) (1)

In the formula (1):

m ₂₃₂, A ₂₃₂, α ₂₃₂Be respectively in the sample ²³²The quality of U, ²³²U activity, ²³²The intrinsic specific activity of U;

T, Ef are respectively Measuring Time and the detector efficiency of alpha energy spectrum instrument;

N _5.3For ²³²The 5.26MeV of U, 5.32MeV reach ²²⁸Total α counting at the 5.34MeV α peak of Th;

N _5.42For ²²⁸The clean counting at the 5.42MeV α peak of Th.

Measure in the uranium sample by many receiving inductances coupled plasma mass spectrometer ²³²U, ²³³U, ²³⁴U, ²³⁵U, ²³⁶U and ²³⁸U accounts for the U elements atomic percentage, because ²³²U, ²³³The shared atomic percent of U is too little, can ignore.With ²³⁴U is example, and its specific activity and Mass Calculation formula are as follows:

A ₂₃₄＝m ₂₃₄·α ₂₃₄ (2)

A ₂₃₄＝N ₂₃₄·/(t·Ef) (3)

$m_{234}=m_U\·n_{234\%}\·M_{234}/\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%},(i=\mathrm{234,235,236,238})---\left(4\right)$

In the formula (4):

N ₂₃₄For ²³⁴The α counting of U;

n _234%For ²³⁴U account for the U element atomic percent;

M ₂₃₄For ²³⁴The atomic weight of U;

m _UQuality for U in the sample.

With (3), (4) two formulas are brought (2) formula into, get formula (5):

$N_{234}=\frac{m_u\·n_{234\%}\·M_{234}\·{\mathrm{\α}}_{234}\·t\·\mathrm{Ef}}{\underset{i}{\mathrm{\Σ}}{M}_i\·n_i\%},(i=\mathrm{234,235,236,238})---\left(5\right)$

In alpha energy spectrum figure, can obtain ²³⁴U, ²³⁵U, ²³⁶U and ²³⁸The tale N of U _z=N ₂₃₄+ N ₂₃₅+ N ₂₃₆+ N ₂₃₈So, can be right ²³⁵U, ²³⁶U and ²³⁸U derives the formula same with formula (5), and the two ends addition of several formula can be derived:

$m_u=\frac{N_z\·\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%}}{t\·\mathrm{Ef}\·\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%}\·{\mathrm{\α}}_i},(i=\mathrm{234,235,236,238})---\left(6\right)$

Can draw computing formula (7) by (1) formula and (6) formula:

$\frac{m_{232}}{m_U}=\frac{(N_{5.3}-0.3767\·N_{5.42})\·\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%}\·{\mathrm{\α}}_i}{{\mathrm{\α}}_{232}\·N_z\·\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%}},(i=\mathrm{234,235,236,238})---\left(7\right)$

Only can find out from formula (7) needs sample is carried out alpha energy spectrum and mass-spectrometer measurement can calculate the sample ²³²The content of U.

The present invention is achieved by the following technical solutions:

(1) with the uranium sample nitric acid dissolve, and electroplates the uranium sample α source of making;

(2) use alpha spectrometer to measure the alpha energy spectrum in uranium sample α source, obtain ²³⁴U, ²³⁵U, ²³⁶U and ²³⁸Total α counting N of U _ZAnd deduction ²²⁸After the Th contribution ²³²The α counting of U;

(3) uranium sample after will dissolving is put into mass spectrometer analysis ²³⁴U, ²³⁵U, ²³⁶U and ²³⁸U account for element U atomic percent;

(4) according to formula

$\frac{m_{232}}{m_U}=\frac{(N_{5.3}-0.3767\·N_{5.42})\·\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%}\·{\mathrm{\α}}_i}{{\mathrm{\α}}_{232}\·N_z\·\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%}},(i=\mathrm{234,235,236,238})$

Calculate in the uranium sample ²³²The content of U.

Adopt in the measurement uranium sample provided by the invention ²³²The method of U, the beneficial effect that has is: (1) is simple to operate.This method only needs carrying out power spectrum and mass spectrophotometry behind the sample source processed, need not to carry out complicated colorimetric estimation, and need not the curve of working; (2) measure accurately.Because this method has been introduced mass spectrometer sample has been analyzed, and has improved accuracy, has reduced the uncertainty of analysis result.

Description of drawings

The alpha energy spectrum figure of accompanying drawing 1 uranium sample.

Embodiment

Below in conjunction with embodiment and Figure of description the technical program is further elaborated.

Embodiment 1

At first with the uranium sample dissolving, adding 5ml concentration in galvanic deposition cell is the (NH of 0.025mol/L ₄) ₂C ₂O ₄With 5ml concentration be the HNO of 0.15mol/L ₃As electrodeposit liquid, add 30 microgram uranium simultaneously, and to regulate electrodeposit liquid pH value with ammoniacal liquor be 1.0, electro-deposition is 4 hours in ice-water bath, and it is 30 μ g/cm that surface density is made in plating ²The α source.

Use the semiconductor alpha spectrometer to measure then ²³⁴U, ²³⁵U, ²³⁶U, ²³⁸Total α counting N of U _ZAnd deduction ²²⁸After the Th contribution ²³²The α counting of U, Measuring Time is 24 hours.

The dilution of uranium sample after will dissolving at last, and with many receiving inductances coupled plasma mass spectroscopy uranium isotope atomic percent.Optimize instrument with natural uranium solution, select for use the standard that approaches with the sample abundance to proofread and correct actual sample, finally obtain in the sample ²³⁴U, ²³⁵U, ²³⁶U and ²³⁸U accounts for the atomic percent of element U, calculates and can calculate in the uranium sample according to following formula ²³²The content of U.

$\frac{m_{232}}{m_U}=\frac{(N_{5.3}-0.3767\·N_{5.42})\·\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%}\·{\mathrm{\α}}_i}{{\mathrm{\α}}_{232}\·N_z\·\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%}},(i=\mathrm{234,235,236,238})$

Measure ²³²The content of U is 1.118 * 10 ^-9g ²³²The known sample of U/gU, final measurement are (1.118 * 10 ^-9± 9.0 * 10 ^-11) g ²³²U/gU (k=2), and mass spectrum is contributed less than 1% its overall uncertainty.The result shows, adopts mass spectrum in the uranium sample ²³²It is higher that U analyzes the accuracy that obtains.

Embodiment 2

Identical with embodiment 1 method therefor, step, different is the pH value of electrodeposit liquid, measures ²³²The content of U is 1.118 * 10 ^-9g ²³²The known sample of U/gU, the result of gained is:

Under the different condition of table 1 electrodeposit liquid pH value ²³²The assay value (k=2) of U

The pH value of electrodeposit liquid	232U content (g/g)
		1.5	1.118×10 -9±9.2×10 -11
2.0	1.118×10 -9±10×10 -11

Embodiment 2

Identical with embodiment 1 method therefor, step, different is the time in plating source processed, and the result of gained is:

Under the different condition of table 2 electroplating time ²³²The assay value (k=2) of U

Electroplating time (hour)	232U content (g/g)
		3	1.118×10 -9±8.8×10 -11
5	1.118×10 -9±9.4×10 -11

Embodiment 2

Identical with embodiment 1 method therefor, step, different is the Measuring Time of alpha spectrometer, and the result of gained is:

Under the different condition of table 3 alpha spectrometer Measuring Time ²³²The assay value (k=2) of U

The alpha spectrometer Measuring Time (hour)	232U content (g/g)
		22	1.118×10 -9±9.3×10 -11
26	1.118×10 -9±9.4×10 -11

Adopt the result of technical scheme gained provided by the invention accurate, measure simply.

Claims (6)

1. ²³²The assay method of U is characterized in that, this method may further comprise the steps:

(1) uranium sample is made the α source;

(2) use alpha spectrometer to measure the alpha energy spectrum in uranium sample α source, obtain ²³⁴U, ²³⁵U, ²³⁶U and ²³⁸The tale N of U _ZAnd ²³²The α counting of U;

(3) will put into mass spectrometer analysis after the uranium sample dissolving ²³⁴U, ²³⁵U, ²³⁶U and ²³⁸U accounts for the atomic percent of uranium element;

(4) according to formula

$\frac{m_{232}}{m_U}=\frac{(N_{5.3}-0.3767\·N_{5.42})\·\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%}\·{\mathrm{\α}}_i}{{\mathrm{\α}}_{232}\·N_z\·\underset{i}{\mathrm{\Σ}}{M}_i\·n_{i\%}},(i=\mathrm{234,235,236,238})$

Calculate in the uranium sample ²³²The content of U.

2. according to claim 1 ²³²The assay method of U is characterized in that, the uranium sample in the described step (1) is earlier with being prepared into the α source behind the nitric acid dissolve again.

3. according to claim 1 ²³²The assay method of U is characterized in that, the method that prepare the α source in the described step (1) is for electroplating, and the pH value of used electrodeposit liquid is 1.0～2.0 during plating.

4. the assay method of 232U according to claim 1 is characterized in that, the electroplating time in plating source processed is 3～5 hours in the described step (1).

5. according to claim 1 ²³²The assay method of U is characterized in that, the Measuring Time of alpha spectrometer is 22～26 hours in the described step (2).

6. according to claim 1 ²³²The assay method of U is characterized in that, mass spectrometer used in the described step (3) for accepting icp ms more.

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