Method for correcting detection efficiency of I-129 in radioactive iodine sampling carbon box
By preparing a series of standard activated carbon powders and plotting PQ and Q-ε curves, the problem of inaccurate calibration caused by differences in iodine distribution in carbon box samples was solved, enabling rapid and accurate correction of detection efficiency for carbon box samples and supporting accurate measurement of I-129 radioactivity concentration in iodine-sampled carbon boxes.
Patent Information
- Application Number
- CN202511731638.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-24
- Publication Date
- 2026-04-07
AI Technical Summary
In existing technologies, the distribution of iodine in each carbon box sample is different, which makes it difficult to guarantee the accuracy of the calibration efficiency. Moreover, the correction process is complex and time-consuming, making it difficult to achieve personalized correction for each sample.
By preparing a series of standard activated carbon powders with different radioactivity, measuring the count rate ratio of the front and back sides of the sample to be tested, plotting PQ and Q-ε curves, and finding the detection efficiency based on the curves, rapid correction of carbon box samples can be achieved.
It enables rapid and accurate detection efficiency correction for carbon box samples, simplifies the correction process, ensures the accuracy of I-129 radioactivity concentration measurement, and supports safety assessment.
Smart Images
Figure CN121806097A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of radiation monitoring, and particularly relates to a method for correcting I-129 detection efficiency in a radioactive iodine sampling carbon box. BACKGROUND
[0002] The operation of a nuclear facility produces radioactive iodine isotope I-129. In order to ensure the safety of the public and the environment, according to relevant monitoring requirements, the gaseous effluent and the atmospheric environment of the nuclear facility need to be sampled and analyzed for I-129. In the gas, the chemical forms of iodine mainly include molecular iodine, methyl iodine and hypoiodous acid. When sampling, a commercial carbon box filled with specially treated activated carbon powder is usually used to capture these radioactive iodines, and then a high-purity germanium gamma spectrometer is used to measure the activity by direct measurement. The carbon box sample is a volume source, and the standard source with the same volume source needs to be calibrated when obtaining the instrument efficiency. The accuracy of the calibration efficiency is a key factor for the accuracy of the monitoring results in radiation monitoring activities.
[0003] A large number of domestic and foreign literatures show that in the carbon box filled with activated carbon powder, the iodine after sampling presents an exponential decay distribution rule, the adsorption amount of iodine is higher near the side where the gas enters, and the adsorption amount is lower at the side where the gas flows out, that is, the distribution of iodine in the carbon box is a function of the internal depth (gas flow direction). The distribution parameters of iodine in the exponential decay in the carbon box are related to the humidity, temperature, gas flow rate and sampling time during sampling. Since each carbon box sample has different sampling conditions, the internal iodine distribution of each carbon box sample is also different. The internal radioactive iodine distribution of the standard carbon box source used for calibrating the instrument efficiency is usually fixed, which can only represent the iodine distribution of one type of carbon box sample, and provide accurate efficiency values. However, the carbon box samples with different distribution conditions should be corrected.
[0004] Since the iodine distribution in each actual carbon box sample is not exactly the same, a large number of experiments, a long time and necessary materials are needed to correct each sample after exploring the distribution parameters of each sample. Considering the complex and variable monitoring conditions of the actual sample, this work is almost impossible to achieve. SUMMARY
[0005] The application aims to provide a method for correcting I-129 detection efficiency in a radioactive iodine sampling carbon box to solve the problems in the prior art.
[0006] The technical solution for achieving the application is as follows:
[0007] The application provides a method for correcting I-129 detection efficiency in a radioactive iodine sampling carbon box, which includes the following steps:
[0008] S1, using initial standard substances and blank activated carbon powder as raw materials, prepare a series of standard activated carbon powders with different radioactive activities;
[0009] S2, Take any one standard activated carbon powder from the standard activated carbon powder series one;
[0010] S3, Take a portion of activated carbon powder from the standard activated carbon powder as the sample to be tested, with an activity of A and a mass of m;
[0011] S4, the mass of activated carbon powder that can fill the carbon box is M, and m / M is defined as Q;
[0012] S5, obtain the front-side count rate Z and back-side count rate F of the sample to be tested;
[0013] Calculate the ratio of the front and back count rates, Z / F, and define this ratio as P;
[0014] Calculate the detection efficiency ε for I-129 = Z / (A·η), where η is the branching ratio of the characteristic γ-rays of I-129;
[0015] S6, change the mass m of the sample to be tested, prepare a series of activated carbon powder samples with different radioactivity distributions in the depth direction, repeat steps S3 to S5 multiple times, and obtain multiple sets of Q, P and ε values.
[0016] S7. Based on the obtained multiple sets of Q, P, and ε, plot the PQ curve and the Q-ε curve;
[0017] S8. For any activated carbon powder sample to be tested, measure its P value, find the Q value according to the PQ curve, and then determine the detection efficiency ε according to the Q-ε curve.
[0018] Optionally, in step S1, the method for preparing a series of standard activated carbon powders with different radioactivity is as follows:
[0019] Standard activated carbon powder series one includes standard activated carbon powder a and standard activated carbon powder b;
[0020] Take the initial standard substance and mix it with blank activated carbon powder. After uniform mixing, standard activated carbon powder a is obtained.
[0021] Take standard activated carbon powder a and mix it with blank activated carbon powder. After uniform mixing, standard activated carbon powder b is obtained.
[0022] If the standard activated carbon powder series includes two or more standard activated carbon powders, then the standard activated carbon powder b is mixed with the blank activated carbon powder and mixed evenly to obtain standard activated carbon powder c.
[0023] This process continues until the required quantity of standard activated carbon powder is produced.
[0024] Optionally, the sample masses in the standard activated carbon powder series I are all greater than M.
[0025] Optionally, the initial standard substance can also be in liquid form;
[0026] When the initial standard substance is in liquid state, add blank activated carbon powder with a dropper and stir quickly. The activated carbon molecules of the initial standard substance will be adsorbed onto the blank activated carbon powder.
[0027] Optionally, after the standard activated carbon powder series I is prepared, a radioactivity uniformity test should be performed. The test method is as follows:
[0028] Take a random mass M of activated carbon powder from standard activated carbon powder a and put it into a carbon box to obtain its front-side count rate and back-side count rate.
[0029] Pour the carbon powder in the carbon box back into the standard activated carbon powder a, mix it evenly again, and then take a random mass M of carbon powder and repeat the above operation.
[0030] Repeat the acquisition of four sets of heads and tails count rates;
[0031] If the count rates of the four front faces and the four back faces are the same, then the uniformity test is passed.
[0032] Optionally, the front count rate is the ratio of the count on the carbon box intake surface to the count time;
[0033] The reverse side counting rate is the ratio of the counting rate on the carbon box outlet surface to the counting time.
[0034] Optionally, in step S6, the method for preparing the second series of activated carbon powder test samples with different radioactivity distributions in the depth direction is as follows:
[0035] Take an activated carbon powder of mass m1 from any one of the standard activated carbon powders in the standard activated carbon powder series 1 as the sample to be tested.
[0036] Place the activated carbon powder sample with a mass of m1 into the lower layer of the carbon box, make its surface flat, and fill the surface with blank activated carbon powder of M-m1.
[0037] Then, take out an amount of activated carbon powder with a mass of m2 from the standard activated carbon powder as the sample to be tested;
[0038] Place the activated carbon powder sample with a mass of m2 into the lower layer of another carbon box, make its surface flat, and fill the surface with blank activated carbon powder of M-m1.
[0039] Repeat the above steps until more than 8 samples have been prepared.
[0040] Optionally, the value of η is 7.5%.
[0041] Optionally, the Q value of the sample to be tested is inversely proportional to the P value.
[0042] Optionally, the detection efficiency ε is inversely correlated with Q.
[0043] The beneficial technical effects of this application are as follows: This application provides a method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon box. By measuring the count rate of the activated carbon powder sample to be tested, the specific distribution depth of its radioactive material can be obtained. Then, the detection efficiency value at that depth can be obtained through a functional relationship, which is used to calculate the I-129 radioactivity concentration. This achieves rapid acquisition of the corrected detection efficiency for each carbon box sample. The technical solution of this application can avoid complex calculations of distribution parameters. Through the constructed correction curve and function, the correction value can be quickly obtained from the curve for the actual sample, realizing accurate measurement of the I-129 radioactivity concentration in the iodine sampling carbon box. This provides an effective basis for controlling emission indicators and assessing atmospheric environmental safety. Moreover, this method still retains the non-destructive analysis of the carbon box sample, is simple to operate, and has strong timeliness. Attached Figure Description
[0044] Figure 1 The process of obtaining the sample to be tested in a method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge provided in this application embodiment;
[0045] Figure 2 The PQ curve obtained by a method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon box provided in this application embodiment.
[0046] Figure 3 The Q-ε curve is obtained by a method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon box provided in this application embodiment. Detailed Implementation
[0047] To enable those skilled in the art to better understand this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only a part of the embodiments of this application, and not all of them. Based on the embodiments described in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0048] Based on the above, in order to clearly and in detail illustrate the advantages of this application, the specific embodiments of this application will be described below in conjunction with the accompanying drawings.
[0049] The specific distribution of radioactive material inside an iodine box is often difficult to determine, making its self-absorption and geometric effects unknown. For I-129, the characteristic gamma ray energy is only 39.5 keV, which is relatively low. At deeper locations inside the iodine box, the ray needs to penetrate a thicker medium to reach the detector, increasing the self-absorption effect. Furthermore, the combined effect of the geometric effects caused by the further reduction in solid angle is difficult to define. To address the accurate measurement of I-129 radioactivity concentration in an iodine sampling carbon box, this application provides a method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon box, comprising the following steps:
[0050] A method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge, characterized by comprising the following steps:
[0051] S1, using initial standard substances and blank activated carbon powder as raw materials, prepare a series of standard activated carbon powders with different radioactive activities;
[0052] S2, Take any one standard activated carbon powder from the standard activated carbon powder series one;
[0053] S3, Take a portion of activated carbon powder from the standard activated carbon powder as the sample to be tested, with an activity of A and a mass of m;
[0054] S4, the mass of activated carbon powder that can fill the carbon box is M, and m / M is defined as Q;
[0055] S5, obtain the front-side count rate Z and back-side count rate F of the sample to be tested;
[0056] Calculate the ratio of the front and back count rates, Z / F, and define this ratio as P;
[0057] Calculate the detection efficiency ε for I-129 = Z / (A·η), where η is the branching ratio of the characteristic γ-rays of I-129;
[0058] S6, change the mass m of the sample to be tested, prepare a series of activated carbon powder samples with different radioactivity distributions in the depth direction, repeat steps S3 to S5 multiple times, and obtain multiple sets of Q, P and ε values.
[0059] S7. Based on the obtained multiple sets of Q, P, and ε, plot the PQ curve and the Q-ε curve;
[0060] S8. For any activated carbon powder sample to be tested, measure its P value, find the Q value according to the PQ curve, and then determine the detection efficiency ε according to the Q-ε curve.
[0061] In some possible implementations of the embodiments of this application, see [link to relevant documentation]. Figure 1 In step S1, the method for preparing activated carbon powder samples with different radioactivity is as follows:
[0062] Standard activated carbon powder series one includes standard activated carbon powder a and standard activated carbon powder b;
[0063] Take the initial standard substance and mix it with blank activated carbon powder. After uniform mixing, standard activated carbon powder a is obtained.
[0064] Take standard activated carbon powder a and mix it with blank activated carbon powder. After uniform mixing, standard activated carbon powder b is obtained.
[0065] If the standard activated carbon powder series includes two or more standard activated carbon powders, then the standard activated carbon powder b is mixed with the blank activated carbon powder and mixed evenly to obtain standard activated carbon powder c.
[0066] This process continues until the required quantity of standard activated carbon powder is produced.
[0067] In one example, the sample masses in activated carbon powder sample series one were all greater than M.
[0068] In another example, the initial standard substance can also be in a liquid state;
[0069] When the initial standard substance is in liquid state, add blank activated carbon powder with a dropper and stir quickly. The activated carbon molecules of the initial standard substance will be adsorbed onto the blank activated carbon powder.
[0070] In some possible implementations of the embodiments of this application, after the standard activated carbon powder series one is prepared, a radioactivity uniformity test is performed, and the test method is as follows:
[0071] Take a mass M of activated carbon powder from the standard activated carbon powder and put it into the carbon box to obtain its front count rate and back count rate.
[0072] Pour the carbon powder in the carbon box back into the standard activated carbon powder, mix it evenly again, and then take a random mass M of carbon powder and repeat the above operation.
[0073] Repeat the acquisition of four sets of heads and tails count rates;
[0074] If the count rates of the four front faces and the four back faces are the same, then the uniformity test is passed.
[0075] In some possible implementations of the embodiments of this application, the front count rate is the ratio of the count on the carbon cartridge air inlet surface to the count time;
[0076] The reverse counting rate is the ratio of the counting on the carbon box outlet surface to the counting time.
[0077] like Figure 1 As shown, in some possible implementations of this application embodiment, the method for preparing the second series of activated carbon powder test samples with different radioactivity distributions in the depth direction in step S6 is as follows:
[0078] Take an activated carbon powder of mass m1 from any one of the standard activated carbon powders in the standard activated carbon powder series 1 as the sample to be tested.
[0079] Place the activated carbon powder sample with a mass of m1 into the lower layer of the carbon box, make its surface flat, and fill the surface with blank activated carbon powder of M-m1.
[0080] Then, take out an amount of activated carbon powder with a mass of m2 from the standard activated carbon powder as the sample to be tested;
[0081] Place the activated carbon powder sample with a mass of m2 into the lower layer of another carbon box, make its surface flat, and fill the surface with blank activated carbon powder of M-m1.
[0082] Repeat the above steps until more than 8 samples have been prepared.
[0083] In some possible implementations of the embodiments of this application, the value of η is 7.5%.
[0084] In some possible implementations of the embodiments of this application, the Q value of the sample to be tested is inversely proportional to the P value.
[0085] In some possible implementations of the embodiments of this application, the detection efficiency ε is inversely correlated with Q.
[0086] The following detailed explanation, using a specific example, illustrates a method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge provided in this application.
[0087] (1) Using initial standard substances and blank activated carbon powder as raw materials, a series of standard activated carbon powders with different radioactivity were prepared: standard activated carbon powder a, standard activated carbon powder b and standard activated carbon powder c.
[0088] The preparation method is as follows: take the initial standard substance and mix it with the blank activated carbon powder. After uniform mixing, the activated carbon powder a is obtained; take activated carbon powder a and mix it with the blank activated carbon powder. After uniform mixing, the activated carbon powder b is obtained; take activated carbon powder b and mix it with the blank activated carbon powder. After uniform mixing, the activated carbon powder c is obtained.
[0089] The mass of standard activated carbon powders a, b, and c is greater than the mass of activated carbon powder that can fill the carbon box by M.
[0090] Radioactivity uniformity was tested on standard activated carbon powders a, b, and c.
[0091] Take a random mass M of activated carbon powder from standard activated carbon powder a and put it into a carbon box to obtain its front-side count rate and back-side count rate.
[0092] Pour the carbon powder in the carbon box back into activated carbon powder a, mix it evenly again, and then take a random mass M of carbon powder and repeat the above operation.
[0093] Four sets of head count rate and tail count rate were repeatedly obtained.
[0094] If the count rates of the four front faces and the four back faces are the same, then the uniformity test is passed.
[0095] Perform the same radioactivity uniformity test on activated carbon powders b, c, and d.
[0096] (2) Take a portion of activated carbon powder from standard activated carbon powder a as the sample to be tested. Its activity is A1 and its mass is m1. Then Q1 is defined as m1 / M.
[0097] Place the activated carbon powder sample with a mass of m1 into the lower layer of the carbon box, make its surface flat, and fill the surface with blank activated carbon powder of M-m1.
[0098] Obtain the front count rate Z1 and back count rate F1 of the activated carbon powder sample in the carbon box, and define P1 as Z1 / F1;
[0099] Calculate the detection efficiency ε1=Z1 / (A1·η);
[0100] Take out activated carbon powder with a mass of m2 from the remaining standard activated carbon powder a as the sample to be tested;
[0101] The same method is used to obtain Q2, P2, and ε2.
[0102] Repeat the above operation until the following values are obtained: Q3, P3, ε3; Q4, P4, ε4; Q5, P5, ε5; Q6, P6, ε6; Q7, P7, ε7; Q8, P8, ε8.
[0103] (3) Based on the obtained 8 sets of Q, P, and ε, plot the PQ curve and Q-ε curve, perform fitting, and obtain the correction function after fitting as follows: Figure 2 and Figure 3 As shown, the goodness of fit were 99.5% and 98.77%, respectively.
[0104] It should be noted that if other standard activated carbon powders are selected, such as standard activated carbon powder b or standard activated carbon powder c, and a portion of the activated carbon powder is taken out as the test sample, the same fitting results will be obtained, that is, the PQ function and Q-ε function are independent of radioactivity.
[0105] The present application has been described in detail above with reference to the accompanying drawings and embodiments. However, the present application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present application. All content not described in detail in this application can be derived from existing technology.
Claims
1. A method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge, characterized in that, Includes the following steps: S1, using initial standard substances and blank activated carbon powder as raw materials, prepare a series of standard activated carbon powders with different radioactive activities; S2, Take any one standard activated carbon powder from the standard activated carbon powder series one; S3, Take a portion of activated carbon powder from the standard activated carbon powder as the sample to be tested, with an activity of A and a mass of m; S4, the mass of activated carbon powder that can fill the carbon box is M, and m / M is defined as Q; S5, obtain the front-side count rate Z and back-side count rate F of the sample to be tested; Calculate the ratio of the front and back count rates, Z / F, and define this ratio as P; Calculate the detection efficiency ε for I-129 = Z / (A·η), where η is the branching ratio of the characteristic γ-rays of I-129; S6, change the mass m of the sample to be tested, prepare a series of activated carbon powder samples with different radioactivity distributions in the depth direction, repeat steps S3 to S5 multiple times, and obtain multiple sets of Q, P and ε values. S7. Based on the obtained multiple sets of Q, P, and ε, plot the PQ curve and the Q-ε curve; S8. For any activated carbon powder sample to be tested, measure its P value, find the Q value according to the PQ curve, and then determine the detection efficiency ε according to the Q-ε curve.
2. The method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge according to claim 1, characterized in that, In step S1, the method for preparing the first series of standard activated carbon powders with different radioactivity is as follows: Standard activated carbon powder series one includes standard activated carbon powder a and standard activated carbon powder b; Take the initial standard substance and mix it with blank activated carbon powder. After uniform mixing, standard activated carbon powder a is obtained. Take standard activated carbon powder a and mix it with blank activated carbon powder. After uniform mixing, standard activated carbon powder b is obtained. If the standard activated carbon powder series includes two or more standard activated carbon powders, then take the standard activated carbon powder b and mix it with the blank activated carbon powder. After uniform mixing, standard activated carbon powder c is obtained. This process continues until the required quantity of standard activated carbon powder is produced.
3. A method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge according to claim 1 or 2, characterized in that, The sample masses in the first series of standard activated carbon powders are all greater than M.
4. A method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge according to claim 1 or 2, characterized in that, The initial standard substance can also be in liquid form; When the initial standard substance is in liquid state, add blank activated carbon powder with a dropper and stir quickly. The activated carbon molecules of the initial standard substance will be adsorbed onto the blank activated carbon powder.
5. A method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge according to any one of claims 1 to 4, characterized in that, After the standard activated carbon powder series I is prepared, a radioactivity uniformity test must be performed. The test method is as follows: Take a mass M of activated carbon powder from the standard activated carbon powder and put it into the carbon box to obtain its front count rate and back count rate. Pour the carbon powder in the carbon box back into the standard activated carbon powder, mix it evenly again, and then take a random mass M of carbon powder and repeat the above operation. Repeat the acquisition of four sets of heads and tails count rates; If the count rates of the four front faces and the four back faces are the same, then the uniformity test is passed.
6. The method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge according to claim 1, characterized in that, The front counting rate is the ratio of the count on the carbon box intake surface to the counting time; The reverse side counting rate is the ratio of the counting rate on the carbon box outlet surface to the counting time.
7. The method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge according to claim 1, characterized in that, In step S6, the method for preparing the second series of activated carbon powder test samples with different radioactivity distributions in the depth direction is as follows: Take an activated carbon powder of mass m1 from any one of the standard activated carbon powders in the standard activated carbon powder series 1 as the sample to be tested. Place the activated carbon powder sample with a mass of m1 into the lower layer of the carbon box, make its surface flat, and fill the surface with blank activated carbon powder of M-m1. Then, take out an amount of activated carbon powder with a mass of m2 from the standard activated carbon powder as the sample to be tested; Place the activated carbon powder sample with a mass of m2 into the lower layer of another carbon box, make its surface flat, and fill the surface with blank activated carbon powder of M-m1. Repeat the above steps until more than 8 samples have been prepared.
8. The method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge according to claim 1, characterized in that, The value of η is 7.5%.
9. The method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge according to claim 1, characterized in that, The Q value of the sample to be tested is inversely proportional to the P value.
10. The method for correcting the detection efficiency of I-129 in a radioactive iodine sampling carbon cartridge according to claim 1, characterized in that, The detection efficiency ε is inversely correlated with Q.