Method for directly measuring 226Ra matrix by gamma energy spectrum method

Abstract

The invention relates to the technical field of geology and environmental analysis and testing, particularly relates to a method for directly measuring a 226Ra matrix by adopting a gamma energy spectrum method, and particularly relates to a method for brand-new elaboration of a 226Ra rapid measurement principle. The method comprises the following steps: 1, preparing a sample; step 2, background measurement; 3, measuring a national standard source; 4, measuring a sample; and 5, calculating the activity of the sample 226Ra. The method disclosed by the invention has the remarkable effects that on the basis of not considering whether the 226Ra-222Rn reaches radioactive equilibrium, the activity of the 226Ra in the sample is directly measured by using 186.2 keV characteristic gamma rays emitted by the 226Ra by using a high-purity germanium gamma spectrometer. By deducting the interference of 185.7 keV characteristic gamma rays emitted by 235U on 186.2 keV characteristic gamma rays emitted by 226Ra, the activity of 226Ra in a sample can be directly measured by directly utilizing the 186.2 keV characteristic gamma rays of 226Ra without waiting for the radioactive equilibrium time of 226Ra-222Rn. The time for waiting for 226Ra-222Rn balance in a very sealed manner can be saved by 3-4 weeks, and the efficiency of reporting sample data is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of geological and environmental analysis and testing technology. 226 The Ra fast measurement principle is completely explained. It is a direct measurement method using γ spectroscopy. 226 Ra matrix method. Background Art

[0002] Natural radionuclides 226 The γ spectrum analysis test of Ra activity is generally measured 3-4 weeks after sealing. 226 Ra- 222 Rn decay equilibrium daughter 214 Pb or 214 The characteristic γ-rays emitted by Bi are selected from the 295.2keV, 352.0keV or 609.3keV γ-rays with the largest branching ratio, and then the parent body is calculated and measured. 226 The activity of Ra. This method is very mature, but its disadvantages are that the detection cycle is very long and the detection efficiency is low. Summary of the invention

[0003] A high-purity germanium gamma spectroscopy method for direct measurement of 226 Ra method, which can measure the sample immediately after packaging, greatly improves the work efficiency. 226 A new method for direct measurement of Ra.

[0004] The technical solution of the present invention is:

[0005] A direct measurement using gamma spectroscopy 226 Ra precursor method, wherein the method comprises the following steps:

[0006] Step 1: Sample preparation;

[0007] Step 2: Background measurement;

[0008] Step 3: National standard source measurement;

[0009] Step 4: Sample measurement;

[0010] Step 5: Sample 226 Ra activity calculation.

[0011] As described above, a method of directly measuring the 226 Ra matrix method, wherein the step 1 comprises the following contents,

[0012] The samples were crushed to pass through a 160-mesh sieve and packaged in a 75*15mm epoxy resin sample box.

[0013] As described above, a method of directly measuring the 226 Ra matrix method, wherein the step 2 includes the following contents,

[0014] The high-purity germanium gamma spectrometer background was measured for 24 hours, and the instrument background counts at 63.3keV, 143.8keV, 163.3keV, and 186.2keV were read out respectively.

[0015] As described above, a method of directly measuring the 226 Ra matrix method, wherein the step three includes the following content,

[0016] The certified national standard material radioactive source was used to measure for 24 hours on a high-purity germanium gamma spectrometer, and the counts at 63.3keV, 143.8keV, 163.3keV, and 186.2keV were read out respectively.

[0017] As described above, a method of directly measuring the 226 Ra matrix method, wherein the step 4 includes the following content,

[0018] The uranium geological samples were measured on a high-purity germanium gamma spectrometer for 8 hours, and the counts at 63.3keV, 143.8keV, 163.3keV, and 186.2keV were read out respectively.

[0019] As described above, a method of directly measuring the 226 Ra matrix method, wherein the step five comprises the following contents,

[0020] The following formula is used to calculate the 226 Activity of Ra:

[0021]

[0022] Where: Q( 226 Ra) represents an unknown sample 226 The radioactivity of Ra, in Bq;

[0023] Q0( 226 Ra) is represented as the standard source 226 The radioactivity of Ra, in Bq;

[0024] Q( 235 U) represents an unknown sample 235 The radioactivity of U, in Bq;

[0025] Q0( 235 U) represents the standard source 235 The radioactivity of U, in Bq;

[0026] P( 226 Ra 186.2 ) is expressed as 226 The emission probability of the 186.2keV characteristic peak of Ra;

[0027] P( 235 U 185.7 ) is expressed as 235 The emission probability of the 185.7keV characteristic peak of U;

[0028] T represents the effective time of sample measurement;

[0029] T0 represents the effective time for standard sample measurement;

[0030] N represents the 186.2KeV characteristic peak count reading in the sample spectrum;

[0031] N0 is represented by the 186.2KeV characteristic peak count reading in the standard source spectrum.

[0032] The significant effect of the present invention is: without considering 226 Ra- 222 Based on whether Rn has reached radioactive equilibrium, a high-purity germanium gamma spectrometer is used. 226 The 186.2keV characteristic gamma ray emitted by Ra directly measures the 226 Ra activity. Deducted by 235 The 185.7keV characteristic gamma ray pair emitted by U 226 The interference caused by the 186.2keV characteristic gamma ray emitted by Ra can be directly used 226 The 186.2keV characteristic γ-ray of Ra directly measures the 226 Ra activity without waiting 226 Ra- 222 The time for Rn radioactive balance can save 3-4 weeks or even sealed waiting time. 226 Ra- 222 The Rn equilibrium time greatly improves the efficiency of reporting sample data.

[0033] Specifically, the high-purity germanium gamma spectroscopy method of the present invention directly measures the 226 Compared with the daughter measurement method currently used at home and abroad, the Ra method can directly measure at any time after the sample is packaged, and can achieve measurement without sealing the sample and waiting for the radium-radon equilibrium. 226 Ra, can save 3 to 4 weeks of waiting time from sealing to radium-radon equilibrium, the measurement results can be reported on the same day, solving the problem 226 The Ra measurement cycle is long. The present invention provides a rapid measurement method for geological samples. 226 Ra's new approach. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a simplified flow chart of the traditional sub-volume measurement method.

[0035] Figure 2 This is a simplified flow chart of the direct maternal measurement method. DETAILED DESCRIPTION

[0036] A direct measurement using gamma spectroscopy 226 The method of Ra precursor comprises the following steps:

[0037] Step 1: Measurement and calculation

[0038] Measure and calculate using the matrix direct measurement method: Use a high-purity germanium gamma spectrometer to measure 226 The 186.2keV characteristic gamma ray emitted by Ra itself is read and the counts are deducted from 235 The counting contribution of the 185.7keV characteristic gamma rays emitted by U. 238 U and 235 U is a constant activity ratio Q( 235 U)=Q( 238 U) / 21.692, calculated 235 The activity of U, and then according to 235 The activity of U is calculated 235 The counting contribution brought by the 185.7keV characteristic γ-ray emitted by U can be obtained 226 The count of 186.2keV characteristic gamma rays emitted by Ra itself is used to calculate 226 The activity of Ra.

[0039] The specific steps include:

[0040] Step 1.1: Basic calculation formula

[0041] Activity calculation formula:

[0042] Where Q is the radioactivity, N is the net count, ε is the characteristic peak detection efficiency, P is the emission probability, and T is the effective time.

[0043] Step 1.2: 226 Ra 186.2 The calculation formula

[0044] From the activity calculation formula: N( 226 Ra 186.2 )=Q( 226 Ra)ε( 226 Ra 186.2 )P( 226Ra 186.2 )T

[0045] Where: N( 226 Ra 186.2 ) is expressed as net counts at 186.2keV;

[0046] Q( 226 Ra) is expressed as 226 The radioactivity of Ra, in Bq;

[0047] ε(186.2) represents the detection efficiency of the detection system for the 186.2keV characteristic peak;

[0048] P(186.2) is expressed as 226 The emission probability of the 186.2keV characteristic peak of Ra;

[0049] T represents the effective time of sample measurement, in seconds;

[0050] The specific values ​​of the above parameters are input externally.

[0051] Step 1.3: 235 U 185.7 The calculation formula

[0052] From the activity calculation formula: N( 235 U 185.7 )=Q( 235 U)ε( 235 U 185.7 )P( 235 U 185.7 )T

[0053] Where: N( 235 U 185.7 ) is expressed as net counts at 185.7 keV;

[0054] Q( 235 U) is expressed as 226 The radioactivity of Ra, in Bq;

[0055] ε( 235 U 185.7 ) represents the detection efficiency of the detection system for the 186.2keV characteristic peak;

[0056] P( 235 U 185.7 ) is expressed as 226 The emission probability of the 186.2keV characteristic peak of Ra;

[0057] T represents the effective time of sample measurement, in seconds;

[0058] The specific values ​​of the above parameters are input externally.

[0059] Step 1.4: Calculation of superimposed peaks

[0060] The formula for superposition peak counting is as follows: In the γ spectrum, we can find that the two peaks of 185.7keV and 186.2keV overlap to form a peak. Therefore, the count of the energy peak here is actually the sum of the two γ-ray counts mentioned above.

[0061] N=N( 235 U 185.7 )+N( 226 Ra 186.2 )

[0062] Because the two characteristic peaks of 185.7keV and 186.2keV are so close, we can roughly assume that ε(186.2)=ε(185.7)=ε in the analysis process.

[0063] From this we can deduce:

[0064] N=[Q( 226 Ra)P( 226 Ra 186.2 )+Q( 235 U)P( 235 U 185.7 )]Tε

[0065] Step 1.5: Calculation

[0066] Calculation is performed based on the principle of relative comparison method: During the entire process of measuring the sample, the geometric constant of the detection system is kept unchanged. According to the principle of relative comparison method (ignoring the influence of self-absorption for the time being), at the above energy peak, the ratio of the net count of the sample to be measured (represented by N) to the net count of the standard source (represented by N0) can be expressed as:

[0067]

[0068] Step 1.6: Expression transformation

[0069] The transformed expression is:

[0070]

[0071] Where: Q( 226 Ra) represents an unknown sample 226 The radioactivity of Ra, in Bq;

[0072] Q0( 226 Ra) is represented as the standard source 226 The radioactivity of Ra, in Bq;

[0073] Q( 235U) represents an unknown sample 235 The radioactivity of U, in Bq;

[0074] Q0( 235 U) represents the standard source 235 The radioactivity of U, in Bq;

[0075] P( 226 Ra 186.2 ) is expressed as 226 The emission probability of the 186.2keV characteristic peak of Ra;

[0076] P( 235 U 185.7 ) is expressed as 235 The emission probability of the 185.7keV characteristic peak of U;

[0077] T represents the effective time of sample measurement;

[0078] T0 represents the effective time for standard sample measurement;

[0079] N represents the net count reading of the 186.2KeV characteristic peak in the sample spectrum;

[0080] N0 is represented by the net count reading of the 186.2KeV characteristic peak in the standard source spectrum.

[0081] The parameters in the above formulas are all input externally or calculated.

[0082] Step 1.7: Q( 235 U) Calculation of activity

[0083] First, according to the activity calculation formula Calculate Q( 238 U), then according to Q( 235 U)=Q( 238 U) / 21.692, calculate Q( 235 U), and then substitute it into the final calculation formula in step 1.6 to calculate Q( 226 Ra).

[0084] The parameters in the above formulas are all input externally.

[0085] Step 2: Sample preparation

[0086] In this method, the samples were crushed to pass through a 160-mesh sieve and packaged in a 75*15mm epoxy resin sample box.

[0087] Step 3: Background Measurement

[0088] The high-purity germanium gamma spectrometer background was measured for 24 hours, and the instrument background counts at 63.3keV, 143.8keV, 163.3keV, and 186.2keV were read out respectively.

[0089] Step 4: National Standard Source Measurement

[0090] The certified national standard material radioactive source was used to measure for 24 hours on a high-purity germanium gamma spectrometer, and the counts at 63.3keV, 143.8keV, 163.3keV, and 186.2keV were read out respectively.

[0091] Step 5: Sample measurement

[0092] The uranium geological samples were measured on a high-purity germanium gamma spectrometer for 8 hours, and the counts at 63.3keV, 143.8keV, 163.3keV, and 186.2keV were read out respectively.

[0093] Step 6: Sample activity calculation

[0094] The following formula is used to calculate the 226 Activity of Ra:

[0095]

[0096] Where: Q( 226 Ra) represents an unknown sample 226 The radioactivity of Ra, in Bq;

[0097] Q0( 226 Ra) is represented as the standard source 226 The radioactivity of Ra, in Bq;

[0098] Q( 235 U) represents an unknown sample 235 The radioactivity of U, in Bq;

[0099] Q0( 235 U) represents the standard source 235 The radioactivity of U, in Bq;

[0100] P( 226 Ra 186.2 ) is expressed as 226 The emission probability of the 186.2keV characteristic peak of Ra;

[0101] P( 235 U 185.7 ) is expressed as 235 The emission probability of the 185.7keV characteristic peak of U;

[0102] T represents the effective time of sample measurement;

[0103] T0 represents the effective time for standard sample measurement;

[0104] N represents the 186.2KeV characteristic peak count reading in the sample spectrum;

[0105] N0 is represented by the 186.2KeV characteristic peak count reading in the standard source spectrum.

[0106] Practice and verification of the present invention:

[0107] 1) 226 Ra- 222 Rn unbalanced ore sample verification test

[0108] The geological uranium ore samples were taken from Xinjiang. After being air-dried, they were crushed and passed through a 160-mesh sieve. Then they were put into a sample box and sealed. After being sealed, they were immediately measured on a high-purity germanium gamma spectrometer. The measurement time was set to 7200s. The measurement was conducted every 24 hours until 226 Ra- 222 Until Rn reaches equilibrium, the statistics of the counts at the 352.0keV characteristic peak are stable. 226 Ra- 222 The sign of Rn balance. In the spectra measured by the above two different samples, the counts at the 186.2keV characteristic peak and the 352.0keV characteristic peak were counted respectively, and the observation was stopped when the counts at the 352.0keV characteristic peak remained basically unchanged. The measurement results are shown in Table 1.

[0109] Table 1 226 Ra- 222 Rn unbalanced ore sample validation test data

[0110]

[0111] According to the data in Table 1, the count readings at the 352.0keV characteristic peak gradually increased within 1-6 days, and the count readings on the 7th to 9th days remained basically unchanged, which means that the geological ore samples No. 211152 and 211153 reached 226 Ra- 222 The count readings at the 186.2keV characteristic peak remained basically consistent from 1 to 9 days, which shows that the count readings at the 186.2keV characteristic peak are not affected by 226 Ra- 222 The influence of Rn balance and 226 Ra- 222 Rn balance is irrelevant. Explanation: Based on the count readings at the 186.2keV characteristic peak 226 Rapid measurement of Ra is possible.

[0112] 2) 226 Ra -222 Rn Balance Ore Sample Verification

[0113] To verify 226 The accuracy of the Ra rapid activity measurement method is that we choose to completely achieve it after 30 days of sealing. 226 Ra- 222 The Rn balanced sample was tested. The measurement was carried out on a high purity germanium γ spectrometer with a measurement time of 7200s. The test results are shown in Table 2.

[0114] Table 2 226 Ra- 222 Rn Balance Ore Sample Verification Test Calculation Table

[0115]

[0116]

[0117] As shown in Table 3, the 14 groups of samples were 226 The activity is calculated based on the Ra fast measurement principle. 226 Ra- 222 The activity of the daughter measurement method after Rn equilibrium is basically matched, and the relative deviation of the measurement results of the two methods is within 12.5%. It can be considered that the use of the method described in this paper 226 Ra matrix direct measurement principle can accurately measure 226 Ra activity.

[0118] Table 3 226 Ra- 222 Rn Balance Ore Sample Verification Test Results Statistics Table

[0119]

[0120] From the previous experiment, 14 groups of samples were used as described in this paper. 226 The activity calculated by the Ra matrix measurement principle is 226 Ra- 222 The activity of the daughter measurement method after Rn equilibrium is basically matched, and the relative deviation of the measurement results of the two methods is within 12.5%, which is a good match. It can be proved that the use of the method described in this paper 226 Ra matrix direct measurement principle can accurately measure 226 Ra activity.

[0121] After the present invention has made a breakthrough in the understanding of the principle of the traditional measurement method, it measures on a high-purity germanium gamma spectrometer, reads the count at 186.2keV, deducts the background, deducts 235 U 185.7 The keV peak count contribution is obtained226 Net counts of Ra at 186.2keV, establishing fast measurement after sealing 226 Ra activity method.

Claims

1. A direct measurement using gamma spectroscopy 226 Ra matrix method, characterized in that The steps include: Step 1: Sample preparation; Step 2: Background measurement; Step 3: National standard source measurement; Step 4: Sample measurement; Step 5: Sample 226 Ra activity calculation.

2. A method of directly measuring using gamma spectroscopy as claimed in claim 1 226 Ra precursor method, characterized in that: The step 1 includes the following contents: The samples sealed for 21 days were crushed to pass through a 160-mesh sieve and packaged in a 75*15mm epoxy resin sample box.

3. A method of directly measuring using gamma spectroscopy as claimed in claim 2 226 Ra precursor method, characterized in that: The step 2 includes the following contents: The high-purity germanium gamma spectrometer background was measured for 24 hours, and the instrument background counts at 63.3keV, 143.8keV, 163.3keV, and 186.2keV were read out respectively.

4. A method of directly measuring using gamma spectroscopy as claimed in claim 3 226 Ra precursor method, characterized in that: The step three includes the following contents: The certified national standard material radioactive source was used to measure for 24 hours on a high-purity germanium gamma spectrometer, and the counts at 63.3keV, 143.8keV, 163.3keV, and 186.2keV were read out respectively.

5. A method of directly measuring using gamma spectroscopy as claimed in claim 4 226 Ra precursor method, characterized in that: The step 4 includes the following contents: The uranium geological samples were measured on a high-purity germanium gamma spectrometer for 8 hours, and the counts at 63.3keV, 143.8keV, 163.3keV, and 186.2keV were read out respectively.

6. A method of directly measuring using gamma spectroscopy as claimed in claim 5 226 Ra precursor method, characterized in that: The step five includes the following contents: The following formula is used to calculate the 226 Activity of Ra: Where: Q( 226 Ra) represents an unknown sample 226 The radioactivity of Ra, in Bq; Q0( 226 Ra) is represented as the standard source 226 The radioactivity of Ra, in Bq; Q( 235 U) represents an unknown sample 235 The radioactivity of U, in Bq; Q0( 235 U) represents the standard source 235 The radioactivity of U, in Bq; P( 226 Ra 186.2 ) is expressed as 226 The emission probability of the 186.2keV characteristic peak of Ra; P( 235 U 185.7 ) is expressed as 235 The emission probability of the 185.7keV characteristic peak of U; T represents the effective time of sample measurement; T0 represents the effective time for standard sample measurement; N represents the 186.2KeV characteristic peak count reading in the sample spectrum; N0 is represented by the 186.2KeV characteristic peak count reading in the standard source spectrum.

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