Radioactive substance detection is an important technical activity widely used in various fields such as environmental protection, medical diagnosis, nuclear industry, and food safety. The following is a detailed introduction to the detection of radioactive substances:
1、 Testing method
1. Physical methods
Mass spectrometry: By measuring the relative atomic mass of isotopes and calculating their abundance in nature. The biggest advantage of this method is its high accuracy. In a mass spectrometer, the elements in the sample being measured generate positively charged ions through the action of cathode rays, and the positive ions are deflected by electric and magnetic fields. Regardless of the velocity of the positive ions, as long as the charge to mass ratio (e/m) is the same, the ions will converge in one place and leave traces on the photographic film; Positive ions with different e/m will converge at different positions, forming corresponding lines. The relative mass of these ions or elements can be obtained by comparing the positions of these spectral lines with those on standard atomic mass spectrometry and corresponding mass scales. By using a current detector to measure the ion current intensity, the relative abundance of these elements can be calculated, and then the relative atomic mass of the elements can be calculated.
2. Chemical methods
Radiochemical analysis: a method for detecting radioactive substances based on chemical reactions. This method involves the chemical reaction of radioactive substances with specific reagents or carriers to form radioactive labeled substances, which are then measured using specific analytical techniques. Common radiochemical analysis methods include precipitation method, extraction method, and solution exchange method. These methods are of great significance in nuclear energy applications and environmental monitoring, as they can be used for quantitative and qualitative analysis of radioactive materials.
Liquid scintillation method: a radioactive substance detection method based on organic liquid scintillators. Compared to solid scintillators, liquid scintillators have higher sensitivity and detection efficiency. This method first mixes the liquid sample with a scintillation agent to form a liquid scintillator. When radioactive particles enter the liquid scintillator, the energy generated will be absorbed by the molecules in the liquid scintillator and a light signal will be released. The concentration of radioactive substances can be obtained by converting them into electrical signals through photomultiplier tubes or photosensitive elements.
3. Other methods
Thermoluminescence method: using the characteristic of certain substances that can absorb and store energy after being irradiated with ionizing radiation, and release it in the form of light after heating, to detect radioactive substances.
Radioisotope tracing method: By adding a tracer of known radioactive isotopes to the sample, the distribution and changes of the tracer in the sample are tracked to detect the presence and content of radioactive substances.
2、 Testing instruments
There are various types of instruments used for detecting radioactive substances, including but not limited to:
·Geiger counter: a commonly used radioactive detector suitable for measuring alpha, beta, and gamma rays. It has the advantages of simple structure, easy operation, and low price.
·α. Beta measuring instrument: specifically used to measure the radiation intensity of alpha and beta particles, and then calculate the radioactive nuclide content in the sample.
·Gamma spectrometer: capable of distinguishing different radioactive nuclides and measuring their intensity and dose. It has wide applications in fields such as environmental monitoring, nuclear industry, medicine, and biology.
·Liquid scintillation counter: Based on the principle of liquid scintillation method, it is used to measure radioactive substances in liquid samples.
3、 Testing steps
Taking the analysis of radioactive isotopes in environmental and biological samples (such as seawater, seafood, etc.) as an example, the detection steps usually include:
1. Sample collection: Select appropriate sampling points and determine the sampling amount. The larger the sampling amount, the more accurate and reliable the analysis results.
2. Sample pretreatment: Screening, cleaning, crushing (such as sea products), and corresponding pretreatment of the collected samples.
3. Sample concentration: Seawater samples can be concentrated by evaporation, while biological samples require compression treatment (such as crushing and compression after freezing or drying, compression after carbonization and ashing, and compression after shredding).
4. Sample measurement and data processing: Use appropriate radioactive measuring instruments to measure the sample, record the measurement data, and perform data processing and analysis.
4、 Testing standards
The detection of radioactive substances involves multiple standards to ensure the accuracy and reliability of the test results. For example:
·GB6566-2020: specifies the methods for detecting radioactive isotopes in building materials and decoration materials, as well as the limits for internal and external exposure indices.
·GB/T 5750.13-2023: Standard Test Methods for Drinking Water Part 13, specifies the detection methods for radioactive indicators.
·DZ/T 0064.76-2021: Methods for Analysis of Groundwater Quality Part 76, specifies the determination of total alpha and total beta radioactivity using radiochemical methods.
5、 Application Fields
Radioactive substance detection is widely used in the following fields:
·Environmental protection: Monitor the content of radioactive substances in the environment and evaluate the impact of nuclear facility emissions on the environment.
·Medical diagnosis: By detecting radioactive substances, it assists doctors in disease diagnosis and treatment.
·Nuclear industry: Ensure the safe operation of nuclear facilities and prevent the leakage of radioactive materials.
·Food safety: Detecting the content of radioactive substances in food to ensure food safety.
6、 Safety precautions
When conducting radioactive substance testing, it is necessary to strictly follow safety operating procedures and take necessary protective measures to protect the safety of personnel and the environment. For example:
·Wear personal protective equipment, including lab coats, gloves, goggles, masks, etc.
·Use radiation protection devices such as lead walls, lead glass windows, etc. to reduce the harm of radiation to the human body.
·Proper disposal of waste: Safely handle and dispose of radioactive waste generated during the testing process to prevent environmental pollution.
In summary, radioactive material detection is an important technical activity that requires the use of scientific methods, advanced instruments, and strict standards for operation. Through effective detection methods, the problem of radioactive contamination can be detected and dealt with in a timely manner, ensuring the safety of people's lives and physical health.
Guangdong Zhonghan Testing Technology Co., Ltd