A β-γ ray dose equivalence test method for irradiation qualification of nuclear power cables

Abstract

This invention discloses a β-γ-ray dose equivalence test method for the irradiation qualification of nuclear power cables. Using the polyolefin sheath material of nuclear power cables as the test object, standardized Type II dumbbell test pieces with multiple thickness gradients are prepared. Gradient dose irradiation is carried out using β-ray and γ-ray devices matched to the design reference accident parameters. Through closed-loop environmental control, precise detection of elongation at break, least squares linear fitting, quantitative thickness correction, and equivalence verification, the β-γ-ray dose equivalence conversion relationship is accurately obtained. This invention solves the technical problems of existing technologies, such as the difficulty in implementing β-ray irradiation tests, the lack of a standard β-γ equivalence relationship, the significant influence of environmental / thickness interference on test data, and the lack of verification steps. It adds technical features such as closed-loop environmental control, thickness correction models, equivalence verification, and intelligent data processing, resulting in accurate and reliable equivalence ratios. It is applicable to the irradiation qualification of third-generation nuclear power cables, significantly improving test accuracy and licensing prospects.

Description

Technical Field

[0001] This invention relates to the field of nuclear power cable testing technology, and in particular to a βγ ray dose equivalence test method for irradiation identification of nuclear power cables. Background Technology

[0002] Third-generation nuclear power requires cable sheaths to withstand high doses of beta-ray radiation, but there is a lack of beta-ray test sources with suitable parameters both domestically and internationally. The industry generally uses mature gamma-ray alternative tests. Current technology only knows that beta rays have weaker penetrating power than gamma rays, but there is no clear beta-gamma dose equivalence relationship. Furthermore, existing tests suffer from deficiencies such as lack of standardized environmental control, unquantified thickness effects, lack of equivalence verification, and crude data processing, resulting in large equivalence ratio errors and unreliable test results, which cannot meet the safety qualification requirements of nuclear power cables.

[0003] Therefore, there is an urgent need for a standardized, high-precision β-γ ray dose equivalence test method with verification steps to solve the core technical challenges in the industry. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing technology only knows that the penetrability of β rays is weaker than that of γ rays, but there is no clear βγ dose equivalence relationship; and the existing experiments have problems such as lack of standardized environmental control, lack of quantification of thickness effect, lack of equivalence verification, and crude data processing.

[0005] The technical solution adopted by this invention to solve its technical problem is: a βγ ray dose equivalence test method for irradiation identification of nuclear power cables, comprising the following steps: S1. Sample preparation: The nuclear power cable sheath material was processed into test pieces, and three thickness gradient groups of 1.8mm, 2.5mm and 3.1mm were set up. Each group of test pieces was divided into an initial control group, a β-ray irradiation group and a γ-ray irradiation group, and parallel test pieces were set up in each group. S2. Environmental and Equipment Calibration: The temperature and humidity of the test environment were stabilized at 23±2℃ and 50±5%RH through the environmental control unit, and the dose rate parameters of the β-ray irradiation device and the γ-ray irradiation device were calibrated. S3. Gradient irradiation: The β-ray irradiation group was irradiated with a reference dose of 300 Mrad, and the γ-ray irradiation group was irradiated with gradient doses of 50, 66, 100, and 150 Mrad. S4. Performance testing: The elongation at break of all specimens was tested using a breaking elongation testing device at a tensile speed of 50 mm / min. S5. Data Fitting: The data processing unit fits the irradiation data through the linear fitting module to obtain the fitting straight lines of β-ray and γ-ray irradiation and obtain the equivalent dose intersection points. S6. Thickness Correction: Based on the relationship between thickness and equivalent dose, a thickness correction model is established to calculate the universal equivalent dose; S7. Equivalence Verification: Verify the accuracy of the equivalence ratio through the equivalence verification module and determine the validity of the test results.

[0006] In step S1, the specimen is pre-cut before irradiation. Five parallel specimens are set for each thickness of the thickness gradient group. Specimens with appearance defects are removed before the test.

[0007] In step S2, the β-ray irradiation device is an electron accelerator with an energy ≤1.2MeV and a dose rate stable at 1.08~1.92Mrad / h; the γ-ray irradiation device is a Co60 source with a dose rate stable at 1.01Mrad / h and a dose rate fluctuation ≤±0.05Mrad / h.

[0008] In step S3, the sample is laid horizontally in the irradiation cavity with a sample spacing of ≥2cm and a vertical distance of 30±5cm between the sample and the irradiation source to ensure irradiation uniformity.

[0009] In step S4, the test piece is placed in an environment of 23±2℃ and 50±5%RH for ≥24h to eliminate internal stress before testing. The average value is taken after removing outliers from the test data.

[0010] In step S5, the linear fitting module uses the least squares method for fitting, and the correlation coefficient of the fitted line is R²≥0.95. The fitting curve is plotted with dose as the abscissa and elongation at break as the ordinate.

[0011] In step S6, the thickness correction model is y=6x+148.2, where x is the thickness of the test piece and y is the equivalent γ dose. A conservative value is taken to obtain a general equivalent ratio of β:γ=1:0.57.

[0012] In step S7, the criterion for the equivalent verification module is: the deviation between the fracture elongation of the verification specimen and the 300Mradβ-ray irradiated specimen is ≤±5%.

[0013] It also includes step S8, data archiving: entering the sample parameters, irradiation data, test results, and equivalent ratio into the database to achieve full-process traceability of test data.

[0014] When the sheath material formula is changed, repeat steps S1 and S7 to recalibrate the equivalent ratio and adapt it to the irradiation identification of nuclear power cables of different materials.

[0015] The beneficial effects of this invention are: (1) The present invention adds environmental closed-loop control, eliminates temperature and humidity interference, and improves the accuracy of detection data by more than 30%; (2) This invention solves the influence of thickness on β-ray damage by establishing a quantitative thickness correction model, which is more versatile; (3) This invention uses the least squares method for fitting (R²) 2(≥0.95), significantly improving data processing accuracy; (4) The present invention adds an equivalent verification step to ensure the reliability of the equivalent ratio and meet the requirements of nuclear power safety assessment; (5) Through standardized sample preparation and pretreatment, the repeatability and stability of the experiment are significantly improved; (6) Data archiving and traceability are adopted to adapt to different material formula updates, making it more widely applicable. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Figure 1 This is a schematic diagram of the experimental method of the present invention.

[0018] Figure 2 This is a schematic diagram of the irradiation device in this invention.

[0019] Figure 3 This is a schematic diagram of the breaking elongation detection device in this invention.

[0020] Figure 4 This is a schematic diagram of the test piece structure in this invention.

[0021] Figure 5 This is a schematic diagram of data fitting and equivalence verification in this invention.

[0022] In the figure: 1. Sample preparation unit, 2. β-ray irradiation device, 3. γ-ray irradiation device, 4. Elongation at break detection device, 5. Data processing unit, 6. Environmental control unit, 7. Specimen, 8. Thickness gradient group, 9. Linear fitting module, 10. Equivalent verification module. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5The embodiment shown uses EVA low-smoke halogen-free sheath material, with test piece thicknesses of 1.8mm, 2.5mm, and 3.1mm.

[0026] Sample preparation: The sheath material is processed into test pieces 7 through the sample preparation unit 1. After pre-cutting, it is divided into three thickness gradient groups 8. Each group has 5 parallel samples, which are divided into an initial control group, a β-ray irradiation group, and a γ-ray irradiation group. Defective samples are discarded.

[0027] Environmental and equipment calibration: The environmental control unit 6 stabilized the test environment at 23±2℃ and 50±5%RH; calibrated the energy of the β-ray irradiation device 2 to ≤1.2MeV and the dose rate to 1.08~1.92Mrad / h; and the dose rate of the γ-ray irradiation device 3 to 1.01Mrad / h with fluctuations ≤±0.05Mrad / h.

[0028] Gradient irradiation: The test piece 7 is laid horizontally in the irradiation cavity with a spacing of ≥2cm and a vertical distance of 30±5cm from the irradiation source; the β-ray irradiation group is given a reference dose of 300Mrad, and the γ-ray irradiation group is given gradient doses of 50, 66, 100, and 150Mrad in sequence.

[0029] Performance testing: The specimen 7 was placed in the environmental control unit 6 for 24 hours to eliminate internal stress. The elongation at break was tested by the elongation at break test device 4 at a speed of 50 mm / min. After removing abnormal data, the average value was taken.

[0030] Data fitting: The linear fitting module 9 of the data processing unit 5 uses the least squares method to fit the data, with R²≥0.95; the equivalent γ dose is 159Mrad for 1.8mm thickness, 163Mrad for 2.5mm thickness, and 171Mrad for 3.1mm thickness.

[0031] Thickness correction: Using the thickness correction model y=6x+148.2, a conservative value is taken to obtain a general equivalent ratio of β:γ=1:0.57.

[0032] Equivalent verification: The equivalent verification module 10 detects and verifies the test piece. If the deviation of the elongation at break is ≤±5%, the equivalent ratio is determined to be valid.

[0033] Data archiving: All test data are entered into the database to achieve full-process traceability and recalibrate the equivalent ratio when the material formula is changed.

[0034] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A βγ-ray dose equivalent test method for nuclear power cable irradiation qualification, characterized in that, Comprise the following steps: S1, sample preparation: the nuclear power cable sheath material is processed into test pieces (7), set 1.8mm, 2.5mm, 3.1mm three thickness gradient groups (8), each group of test pieces is divided into initial control group, beta ray irradiation group, gamma ray irradiation group, each group is provided with parallel test samples; S2, environment and equipment calibration: through the environmental control unit (6), the test environment temperature and humidity is stabilized at 23±2℃, 50±5%RH, the dose rate parameters of beta ray irradiation device (2) and gamma ray irradiation device (3) are calibrated; S3, gradient irradiation: the beta ray irradiation group is irradiated with 300Mrad reference dose, and the gamma ray irradiation group is irradiated with 50, 66, 100, 150Mrad gradient dose; S4, performance detection: through the elongation at break detection device (4), the elongation at break of all test pieces (7) is tested at a tensile speed of 50mm / min; S5, data fitting: the data processing unit (5) fits the irradiation data through the linear fitting module (9), obtains the fitting straight line of beta ray and gamma ray irradiation, and acquires the equivalent dose intersection; S6, thickness correction: based on the correlation between thickness and equivalent dose, a thickness correction model is established to calculate the general equivalent dose; S7, equivalent verification: the equivalent verification module (10) is used to verify the accuracy of the equivalent proportion, and the effectiveness of the test results is determined.

2. The test method of claim 1, wherein, In step S1, the test pieces (7) are pre-cut processed before irradiation, each thickness of the thickness gradient group (8) is provided with 5 parallel test samples, and the samples with appearance defects are removed before the test.

3. The test method of claim 1, wherein, In step S2, the beta ray irradiation device (2) is an electron accelerator with an energy of ≤1.2MeV, and the dose rate is stabilized at 1.08~1.92Mrad / h; the gamma ray irradiation device (3) is a Co60 source, and the dose rate is stabilized at 1.01Mrad / h, and the dose rate fluctuation is ≤±0.05Mrad / h.

4. The test method of claim 1, wherein, In step S3, the test pieces (7) are horizontally laid in the irradiation chamber, the distance between the test samples is ≥2cm, the perpendicular distance between the test pieces (7) and the irradiation source is 30±5cm, and the uniformity of irradiation is ensured.

5. The test method of claim 1, wherein In step S4, the test pieces (7) are placed in the environment of 23±2℃, 50±5%RH for ≥24h to eliminate internal stress before detection, and the average value is taken after removing the abnormal value of the detection data.

6. The test method of claim 1, wherein, In step S5, the least square method is used for fitting in the linear fitting module (9), the correlation coefficient R² of the fitting straight line is ≥0.95, and the fitting curve is drawn with the dose as the abscissa and the elongation at break as the ordinate.

7. The test method of claim 1, wherein In step S6, the thickness correction model is y=6x+148.2, x is the thickness of the test piece, y is the equivalent gamma dose, and the general equivalent proportion of beta:gamma=1:0.57 is obtained by taking the conservative value.

8. The test method of claim 1, wherein, In step S7, the determination standard of the equivalent verification module (10) is that the elongation at break of the verification test piece and the elongation at break of the test piece irradiated by 300Mrad beta ray is ≤±5%.

9. The test method of claim 1, wherein, It also comprises step S8, data archiving: the sample parameters, irradiation data, detection results and equivalent proportion are input into the database to realize the whole process traceability of the test data.

10. The test method of claim 9, wherein, When the sheath material formula is changed, steps S1.S7 are repeated to recalibrate the equivalent proportion and adapt to the irradiation identification of nuclear power cables with different materials.

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