How Do I Get a Radiologic Technologist Certification?

Radioactivity detection ^[1] refers to the safety inspection of radioactive machines or construction sites that can produce ionizing radiation or electromagnetic radiation. Due to the huge radioactive hazards, and in general can only be sensed with the help of specialized instruments, radioactive detection is widely used in production and life. The word details the classification of radioactive detectors, common radioactive detection instruments, radioactive detection agencies, and radiation safety related content.

Electromagnetic radiation is the radiation of electromagnetic waves generated by alternating electric and magnetic fields to the surrounding space. Due to the low energy of such radiation, it is not possible to cause ionization of surrounding matter. Strictly speaking, all electrical appliances (including household appliances) generate electromagnetic radiation, but what really causes environmental pollution and affects human health are some high-power communication equipment, such as radar, television and radio transmitting devices, industrial microwave heaters (household microwave There may also be leakage of electromagnetic radiation), RF induction and medium heating equipment, high-voltage power transmission and transformation equipment, electromagnetic medical and diagnostic equipment, etc. Because the nature of radiation is different, its mechanism of action on the human body is also different from ionizing radiation. Electromagnetic radiation is divided into near-field and far-field fields, which are divided by the distance of a wavelength. The electromagnetic field strength of the near field is much greater than that of the far field, so it is the focus of monitoring and protection.

Nuclear instruments are instruments used to monitor ionizing radiation (for electromagnetic radiation, instruments such as field strength meters and spectrum analyzers) are used. Nuclear instruments can be roughly classified as follows:

1, according to the nature of the measurement object

Alpha meter: charged particle meter

Beta meter: charged particle meter

Gamma measuring instrument

n measuring instrument

Since different particles interact with different substances, different sensors are used for different particles. They can be divided into gas, flicker, semiconductor sensors and so on.

2. According to the purpose of monitoring:

Particle intensity meter (total , total , total , neutron) is only related to the number of particles, and has nothing to do with energy.

Dosimeter: It mainly refers to penetrating radiation, , x, and neutrons. It is not only related to the number of particles, but also to energy, but it is impossible to distinguish which kind of nuclide is.

Spectrometer: (, , , x, neutron), distinguishing different radionuclides, and can be combined with the built-in database and the correct calibration method to determine the intensity and dose of various nuclides.

3, according to monitoring purposes:

Entrance detectors: (pedestrians, vehicles, trains, luggage packages, cargo, containers, etc.) are used for entry-exit inspection and quarantine and homeland security.

Site (fixed point) dosimeter: used to find abnormal emissions in the monitoring area, to monitor and alarm the dose at the source site.

Inspection dosimeter: used in nuclear environment, nuclear safety, looking for radioactive sources, and finding special nuclear materials. Personal dose alarm: used for personal dose monitoring and alarm for nuclear safety and nuclear counter-terrorism personnel. Nuclide identification device: used to identify radioactivity Types of isotopes and special nuclear materials and their strengths can be divided into laboratory and portable.

Nuclear waste monitor: used in nuclear facilities, nuclear power plants, etc. Surface pollution monitors for monitoring and classifying nuclear waste: monitors the road surface (vehicle), the whole body and the surface of work clothes (fixed), desktop or any surface of the work area (portable) ).

Gas and aerosol measuring instruments: measuring effluent monitoring systems such as radon gas, radon gas, Xe and other inert gases: used in large nuclear facilities such as nuclear power plants

Nuclear imaging system: large-scale nuclear instrument, which uses a combination of radiation source and sensor to scan and image the monitoring target

Other auxiliary facilities: such as automatic weather stations, aerosol sampling equipment, radio positioning systems, on-board equipment, etc.

Radioactive detection gas detector

Principle ^[1]

A gas detector uses a gas as a working medium, and a detector that outputs an signal due to an ionization effect generated by an incident particle therein.

Features

The outstanding advantages of gas detectors are: sensitive detector, almost unlimited size and shape, no nuclear radiation damage or easy recovery, and economical and reliable operation.

Include types

Gas detectors usually include 3 types of detectors in different working states: ionization chamber, proportional chamber and G-M tube. Their common feature is to obtain information about nuclear radiation by collecting electron-positive ion pairs generated when rays pass through a working gas. G-M counting tube is a counting tube invented by Geiger and Muller, which is widely used. Its outstanding features are simple manufacturing, cheap price, and easy use; its disadvantages are long dead time, only Can be used for counting. The current neutron detector uses a proportional counter. The material used was BF3, but now it is generally 3He.

Radioactive detection scintillation detector

principle

Scintillation detectors are detectors that use the flash of radiation in certain substances to detect ionizing radiation ^[3] .

composition

Typical composition of scintillation detector: scintillator, light guide, photomultiplier tube, tube holder and voltage divider, preamplifier, magnetic shield and cassette.

work process

(1) Radiation is injected into the scintillator to ionize or excite the scintillator atoms and molecules, and the excited atoms are de-excited to emit fluorescence in the wavelength of visible light;

(2) Fluorescent photons are collected to the photocathode of a photomultiplier tube (PMT), and photoelectrons are emitted through the photoelectric effect;

(3) The electron multiplies and outputs a signal in the anode output circuit.

kind

(1) Inorganic scintillator: inorganic crystal (doped) NaI (Tl), Cs (Tl), ZnS (Ag), etc.

(2) Organic scintillator: organic crystal;

Organic liquid scintillators and plastic scintillators, etc.

(3) Gas scintillator: A r, Xe, etc.

Radioactive detection semiconductor detector

Semiconductor detectors have brought significant development to the development of radiation detectors, especially to charged particle spectroscopy and chirped ray spectroscopy ^[4] .

Principle

The charged particles generate electron-hole pairs in the sensitive volume of the semiconductor detector. The electron-hole pairs migrate under the action of an external electric field to output a signal. Its detection principle is similar to that of a gas ionization chamber, sometimes called a solid ionization chamber.

Features

The linear response is good and the energy resolution is the best. The detection efficiency of chirped rays is high, which can be compared with that of scintillation detectors. Semiconductor detectors are widely used in various types of ray detection instruments, especially in the field of radon energy spectrum measurement, which have an irreplaceable role.

Common detector

Personal radiation detector

The instrument is small and compact ^[1] , and is used on the human torso to determine the personal dose equivalent and personal dose equivalent rate of external exposure to X and thallium radiation to the wearer. The main purpose is to personally protect radioactive workers. It can detect the dose equivalent rate at the time of wearing, and can also detect the dose equivalent within a set period of time, and can set alarm values to sound, light or vibration for alarm. The measurement energy range is 50keV to 1.5 MeV.

Portable X and Radon Dose Rate Meter

This instrument is battery-powered, lightweight, and portable, and is the most commonly used X and Radon measurement instrument at ports. The instrument includes one or several X and Krypton radiation detectors with a measurement energy range of 50keV to 3M eV and a response time of no more than 8s; usually has an alarm function and can be used as a monitor; sensitivity and accuracy for measuring radiation dose rates Both are much higher than PRD, and the measured dose rate value can be used as the original result to judge the radioactivity level of the test object. Some instruments can be used to measure radon, surface contamination, or neutron radiation by changing the probe ^[1] .

Portable Energy Spectrometer

The appearance of this instrument is basically the same as that of GSD. The difference is that the energy spectrum measurement function is added to the GSD. Generally, NaI (Tl) scintillator is used as the probe material. The detection efficiency of NaI (Tl) material is high, it can be used for energy response and measurable energy spectrum, but the energy resolution is low, so RID can be used for approximate nuclide characterization in the field.

Channel X and Radiation Monitor

Channel-type X and thorium radiometers are mainly used to detect the radioactivity of vehicles, people, baggage and mail, and are sometimes referred to as door or fixed radioactivity monitoring systems. Compared with the portable type, the fixed X and tritium radiation meter generally uses plastic scintillator as the detection part, which can be made larger, so the detection sensitivity is higher. The detection energy range should be between 50keV and 7MeV, and at least 80keV ~ 1.5M eV, usually the alarm pre-set value can be set to cooperate with the automatic monitoring work. Some are equipped with neutron detectors, which can monitor neutrons ^[1] .

Neutron detector

Neutron detectors ^[5] are portable or wearable instruments that measure on-site neutron counts or doses. Since neutrons are not charged, they cannot be measured directly. Generally, neutrons are detected by nuclear reactions or elastic collisions with substances. The commonly used detector is a gas proportional counter tube filled with 3H e and BF3. Due to the rare occurrence of neutron radiation, neutron detectors are generally not purchased separately but are configured as additional functions of other instruments.

High-purity germanium ytterbium energy spectrometer

The radon energy spectrometer measures the radionuclide and content of the measured substance by measuring and analyzing the radon energy spectrum. Generally speaking, the radon spectrometer refers to a large-scale spectrometer in a laboratory. The probe material is a semiconductor material. Now high-purity germanium materials are used. The energy resolution is excellent. Liquid nitrogen or electric refrigeration is required for measurement. It is generally placed in a lead room when measuring, and can accurately identify and quantify the very low content of radionuclides in the sample ^[1] .

Other instruments

There are other instruments and equipment that may be used in actual work. For example, the vehicle-mounted radiation detector has the same detection method as the channel type, but its detector is installed on the vehicle and can be moved. A radon camera that superimposes optical imaging and radon dose rate distribution gradient images can display the location of the radioactive source (hot spot) in the observation area very clearly and intuitively in the form of photos. There is also a device for installing the detector on a grapple or a gantry crane, which can directly measure the radioactivity of the cargo when it is grasped and hoisted ^[1] .

testing facility

Jinan Zhongwei Environmental Testing Co., Ltd. ^[6]

Jinan Zhongwei Environmental Testing Co., Ltd. is a third-party professional testing service agency with China National Metrology Certification Qualification Certificate CMA. The test report issued by it has legal effect.

The company has advanced equipment and a professional technical team. At present, it mainly conducts the following testing services to the society:

1. Ionizing radiation detection (radiation source detection, X-ray machine detection, ray device detection, real estate background detection, dosimeter detection)

2. Electromagnetic radiation detection (industrial, RF electromagnetic field detection, radio interference field strength)

3. Noise detection

4. Surface contamination detection

5. Radon detection

As a third-party environmental professional testing service agency, we have strong technical force and a high-quality testing professional team. This unit fully utilizes its strong talent network and is equipped with a considerable number of modern instruments and equipment to serve the rapid development of China's industry Environmental protection work. Vigorously promote and develop domestic environmental protection undertakings. Thanks to the support and help of leaders at all levels of society and people from all walks of life, the unit has achieved rapid, stable, healthy and coordinated development, and has won the trust and praise of people in the industry.

Radiation knowledge

Radiation is divided into ionizing radiation and electromagnetic radiation

Ionizing radiation and electromagnetic radiation are collectively called radiation (radiation is actually a broader concept, including light radiation, thermal radiation, acoustic radiation, seismic wave radiation, etc.). Its essence is to emit and propagate energy to surrounding space matter in the form of waves or particles.

Easy to absorb radiation in frequent flights

Wenhui reported that the people who fly often are more likely to get cancer due to prolonged exposure to radiation. Experts said that the amount of radiation exposed by regular passengers of the plane is equivalent to 170 times a year for an ordinary person to illuminate the lungs. The amount of radiation absorbed by the crew each year is higher than that of workers exposed to nuclear materials. The radiation that affects aircraft comes from the sun. At high altitudes, because the atmosphere is thinner, the ability to block radiation is lower, so passengers are more vulnerable to solar radiation. FAA experts said that general passengers do not need to be alarmed, because of their number of flights and altitude, they will not increase the risk of cancer, but often make transoceanic flights, and the frequency is more frequent, the risk is greater.

How to prevent the harm caused by electromagnetic radiation

1. Prevent the effects of electromagnetic radiation on the human body:

(1) Shielding room: It is composed of metal (sheet, net), and is mostly used to shield the active field of large mechanical groups or control rooms;

(2) Shielding Helmet, Shielding Helmet and Shielding Glasses: These are personal protective gear, which can effectively reduce the intensity of magnetic radiation to protect the health of workers who are exposed to electromagnetic radiation;

(3) Shield: This is the main method for shielding the active field of small instruments. The materials used for shielding are generally required to be conductive materials with low resistivity, such as copper and aluminum;

(4) For the electromagnetic radiation generated by the mobile phone, you can wear headphones to reduce the electromagnetic radiation. Experiments in the Tel Lab of the Telecommunications Transmission Research Institute of the Ministry of Information Industry have proven that the amount of radiation received by the head when talking with a headset is directly radiated with a mobile phone The amount is between 1/100 and 1/200.

2. The main methods to prevent electromagnetic radiation from leaking your computer secrets are:

(1) Passive mode: electromagnetic shielding to prevent electromagnetic waves from leaking outward. The disadvantage of using this mode alone is that if the shielding is not complete, high-sensitivity electromagnetic receiving equipment can still obtain information;

(2) Active mode: transmitting electromagnetic waves, so that the electromagnetic receiving equipment used for stealing receives the interfered signal. The disadvantage of using this mode alone is that if you use well-designed software to analyze the received interfered signal, it is still possible and useful information to be restored.

Therefore, the best approach is to mix both modes.

Therefore, to adopt a passive mode to prevent electromagnetic waves from leaking outward, we must start from these aspects. It is not enough to shield the display alone. When using the computer in a confidential situation, all unnecessary cables and peripheral equipment should be removed.

Battery-powered laptops can eliminate this connection. However, if it is necessary to use a public power supply, a passive mode filter device or an active mode interference signal is injected into the power line, which can be considered as a measure.

Radiation protection

In view of the electromagnetic radiation generated by electrical products in contact with daily life, which may endanger health, the Chinese Consumers Association issued a warning: electromagnetic radiation must be prevented in daily life. Relevant experts remind consumers ^[7] :

Do not place household appliances too centrally or use them together to avoid exposing yourself to the danger of overdose radiation. Especially TVs, computers and refrigerators should not be placed in the bedroom.

All household appliances, office equipment, mobile phones, etc. should be avoided as long as possible. When you need to use electrical appliances such as televisions and computers for a long time, you should pay attention to leaving once an hour, and look at the distance or close your eyes to reduce the fatigue of the eyes and the effects of radiation.

When the electrical appliances are suspended, it is better not to leave them in standby state, because a weak electromagnetic field can be generated at this time, and radiation accumulation will also occur for a long time.

Keep a certain safety distance for the use of various electrical appliances. For example, the distance between the eyes and the TV screen is generally about 5 times the width of the screen. When the microwave oven is turned on, leave it one meter away. Pregnant women and children should stay away from the microwave oven. When using the mobile phone, the distance between the head and the mobile phone antenna should be as far as possible. For some, it is best to use a separate headset and microphone to answer the call.

People who live and work near high-voltage lines, radar stations, television stations, electromagnetic wave transmission towers, patients with cardiac pacemakers, and people living in modern electrical automation environments, especially pregnant women, children, and the elderly with weak resistance If possible, a shield protective clothing that blocks electromagnetic radiation should be provided.

Electric equipment with display screens such as televisions and computers can be installed with electromagnetic radiation protection screens, and users can also wear radiation protection glasses. The radiation generated by the display may cause dry skin, accelerate skin aging and even cause skin cancer, so you should wash your face in time after use.

The mobile phone emits the most electromagnetic radiation when it is turned on. For this reason, it is best to answer the phone when the mobile phone rings for one or two seconds or the phone rings twice.

Eat more carrots, tomatoes, kelp, lean meat, animal liver and other foods rich in vitamin A, C and protein to strengthen the body's ability to resist electromagnetic radiation.