Author：unknown Source：Hebei Environmental Protection Bureau Website Clicks：254 Update Time：2005-10-26
In the periodic table of elements, one element occupies one position. Later, scientists have further discovered that the atoms of the same element are not exactly the same, some atoms are heavier, some are lighter; some atoms are very stable and will not change, and some atoms are radioactive and will change, and decay into the atoms of another element. We call these atoms, which are in the same element but have different properties, isotopes. Some of the isotopes emit rays, so they are called radioactive isotopes. Radioactive isotopes have the following three properties:
First, they emit different kinds of rays. Some emit alpha rays, some emit beta rays, some emit gamma rays or both of them. There are also neutron rays. Of these, alpha rays are a stream of alpha particles with a positive charge, and beta rays are a stream of electrons with a negative charge.
Second, the rays emitted are determined by the different atomic nuclei themselves. For example, each time the cobalt-60 nucleus decays, it radiates three particles: a beta particle and two photons, and cobalt-60 eventually becomes stable nickel-60.
Third, it has a certain lifetime. People call the time it takes for the number of nuclei of a radioactive isotope that begins to exist to be reduced to half the number of nuclei, the half-life. For example, the half-life of cobalt-60 is about five years.
Radioisotopes come from three main sources - the products of charged particles in gas pedals, the products of neutron bombardment in reactors, and separated fission products. The main advantage of using radioisotopes is that their presence can be detected by measuring the particles they emit and characterizing their characteristic half-life and radiation properties. Radioisotopes have a wide range of applications in energy, industry, agriculture, medicine, the environment, archaeology, and many other areas.
Tracer technology
The tracer method is to introduce a small amount of radioactive isotopes, and at any time to observe their whereabouts of the method. For example, the best way to fertilize plants with phosphorus can be found by mixing a small amount of radioactive phosphorus-32 (which has a half-life of 14.28 days and emits beta particles of 1.7 mega-electron volts) into fertilizer. Accurate information on the rate of phosphorus uptake and accumulation can be obtained by measuring the change in radiation over time and its location in the plant with probe or photographic film. Similarly, tracer experiments on human blood circulation can be carried out by injecting the body with a harmless solution of radioactive sodium-24 (half-life 15.03 hours). For medical diagnostic purposes, it is desirable to introduce enough radioactive material to provide the required data, but the radioactive material must not be at a level that is harmful to the human body.
Furthermore, monitoring the movement of fluids doped with radioactive isotopes can determine the flow rate of many substances, such as blood in the human body, oil in pipelines, or sewage discharged into rivers. Tracer technology can also be used to analyze the form of pesticides in living organisms, and study the changes that occur after pesticide application and its movement in the ecosystem.
Knowledge about the basic products of photosynthesis also became known after the use of carbon dioxide-14 (14CO2) as a tracer. Carbon-14 in CO2-14 is a radioactive isotope of carbon. In addition, some plants have a very ingenious function - at night, they constantly absorb carbon dioxide, and by day, they photosynthesize in their leaves. This phenomenon was also discovered as a result of research using CO2-14.
Detailed information about plant respiration can also be studied using the tracer CO2-14. For example, how does plant respiration differ due to the difference between day and night? How does respiration affect photosynthesis? What are the differences in respiration between different plants, and so on.
In addition, how do various substances such as starch, proteins, and fats produced by photosynthesis move and transfer within the plant? And how to accumulate and stored in a variety of different "warehouse"? These "warehouses" include fruits (like rice, wheat), stems (like potatoes), roots (like sweet potatoes) and so on. All of these ingenious arrangements and behaviors of nature can only be explained after research using the tracer carbon-14. At present, in addition to carbon dioxide-14, other radioactive isotopes, such as phosphorus-32 and hydrogen-3, can be used as tracers, thus enabling some research work to be done in a more detailed and thorough manner.
And some work, such as the study of herbicides, livestock or chicken feed in the transmission of nutrients in the study as well as a variety of ecological aspects of the study of insects, etc., are inseparable from the use of tracer methods. It is because of the tracer technology, it is for a variety of sophisticated research to open up a new road, promote the development of various aspects of research.
Neutron activation analysis
Activation analysis is an analytical method that reveals the presence and amount of trace impurities. Irradiation with neutrons (such as reactor neutrons) may contain a certain trace elements of material samples, different atomic nuclei eat slow neutrons produced by radioactive isotopes will undergo completely different nuclear decay, by measuring the unique energy and intensity of its emitted β or γ rays, you can get the content of the impurity in question. Even materials the size of dust, which are invisible to the naked eye, can be quantitatively determined to contain many kinds of trace elements if they are put into the reactor and irradiated.
This measurement method has a wide range of uses. For example, to investigate the dispersion effect of pesticide spraying by helicopter. After the pesticides are dispersed in the paddy field, rice seedlings are collected from different parts of the field and put into the reactor for irradiation, and the radioactivity of the trace pesticides can be measured after activation analysis. The amount of pesticide adhering to each rice seedling can then be known. Based on these measurements, the distribution of pesticide dispersion can be mapped.
The use of activation analysis is also often necessary for the investigation of public hazards caused by soot or wastewater discharged from factories. For example, a trace of dust samples in the atmosphere, activation analysis, you can get a lot of information about the atmosphere. Such as what elements are contained in the dust? What is the content of each element. It can also find out the relationship between different sources of pollution such as municipal waste incinerators, various boilers, smelting furnaces in iron and steel mills, etc. and environmental pollution. In addition, activation analysis can also study how soot or wastewater is diffused?
Activation analysis technology applied to the detection of chemical, is also very productive. Usually, the criminal who has just shot a pistol is always attached to some traces of nitrous smoke in the cuffs of his clothes and the front chest and other parts of his body. From the suspect's clothes cut off a small piece, put into the reactor to receive irradiation, activation analysis. As a result, various trace elements in the nitrous oxide, such as antimony, barium, etc., can be clearly shown. Then, by comparing these data with the data measured on the victim, it is possible to find out if they are the same. Thus, it is possible to come up with hard evidence that the criminals did not expect.
In addition, the criminal left at the scene of the crime hair, but also often through the activation of analysis to carry out research. For example, a car behind the trunk found in the hair is not the victim's, it can be through the activation analysis to determine. There is no need to cite the example of Napoleon's hair, because the principle is the same, the collected hairs into the reactor irradiation, activation analysis, measured the trace elements, according to these measurements will be able to determine whether A, B or other people with the case.
In detective chemistry, activation analysis can also be used to search for stimulants and narcotic drugs. Through the activation analysis of stimulants, trace drugs that characterize various synthesis methods are measured, and then the manufacturing methods of stimulants can be identified based on the mixing of these trace drugs. Another example is that drugs such as marijuana or opium from all over the world contain cerium, lanthanum, neodymium and other trace rare earth elements, and by measuring the content of these elements through activation analysis, the origin of these drugs can be understood. This will enable us to find out whether the drugs are the same, and what connections they have with smuggling organizations.
In addition, if equipped with a neutron generator, put to the bottom of the deep sea, can be used to explore the seabed material; can also be used to determine the ancient currency or bronze mirrors, such as ancient cultural relics and archaeological historical materials. It is said that in order to identify whether a painting of a cat is a masterpiece of the famous Japanese painter Fujita Tsuji, the method of activation analysis was utilized. The painting was placed in a reactor and irradiated, and the mask was quickly removed. Because the analysis showed a high silver content, it proved to be a clever forgery, copied from a photograph.
Triggering Species Mutations
The application of thermal neutrons from atomic reactors or fast neutrons from gas pedals, as well as rays emitted by radioactive isotopes, can alter the structure of the genetic material inside biological cells, thus causing mutations in a wide variety of biological traits. Radioactive isotopes of this nature can be for us:
1. Radiation breeding
With the development of science and technology, people are no longer simply use the plant itself naturally occurring variation, but can apply the achievements of modern science to artificially create a new type of variation, this method is called "artificial priming". Generally speaking, the favorable mutation induced by artificial mutation can have a chance of one in a thousand, while the natural mutation only has a chance of one in a million, and artificial mutation can increase the mutation rate by a thousand times. But so far, one cannot control the direction of mutation. We must carefully select among the progeny of various mutations in order to produce the good breed that meets our expectations. This method of selecting good seeds by radiation-induced mutation is called "radiation breeding". It is following the "systematic selection", "cross-breeding" after the rise of a new breeding method.
2. Radiation pest control
Large amounts of irradiation can also make some pests mutate. For example, the larvae of the spiral fly will lose their fertility after a certain amount of radiation. These sterilized screwflies are then allowed to mate with screwflies from infested areas, which can cause the mated females to never lay eggs and reproduce again. In this way, after about a year and a half, the fly can be made extinct. This method of eradicating pests is called the "radiation sterilization method" or "male sterility method.
Use of radiation to kill
1. Food preservation
It is the use of radioactive isotopes or low-energy gas pedal radiation released on the food radiation treatment, to achieve the purpose of long-term preservation of food. Radiation has some special instincts. It has high energy and strong ability to penetrate the material. A certain dose of irradiation can kill microorganisms and pests parasitized on the surface and inside of food. A proper dose of irradiation can inhibit the life activities of agricultural and livestock products. This fundamentally eliminates the root cause of food mold and deterioration.
Irradiation preservation is a fast-developing new food preservation technology. Research results show that irradiation of food on the human body does not have any adverse effects, can be used for human consumption, safe and reliable.
2. Irradiation sterilization
The use of radioisotopes emitted by the ray sterilization, is the ray killing power of a most direct use. In particular, people often use rays to sterilize medical equipment. For example: sutures used to close wounds during surgery, intestinal wall sutures; disposable syringes; insertion of bronchial tubes with a probe catheter, surgical rubber gloves, blood collection plate for blood collection, into the uterus of the contraceptive ring, artificial kidney fluoroscopy, and so on, but also the use of ray sterilization technology.
The application of radiographic sterilization is also varied from country to country. For example, in India, penicillin, tetracycline and other pharmaceuticals are sterilized by ray sterilization. In Russia, even plastic medical supplies, vaccines, serums, etc., only the use of ray sterilization disinfection method is the only reliable, applicable disinfection method.
In addition, radiation sterilization can also be used in sewage treatment. Usually, sewage is treated by the "activated sludge method". The resulting sediment, sludge slurry is also very nasty and requires further treatment. The sludge slurry itself contains many elements such as phosphorus and nitrogen, so it can be used as a high-quality fertilizer. However, on the other hand, there is a concern that a variety of bacteria are hidden in the sludge. Therefore, the sludge is first sterilized by irradiation with gamma rays of cobalt-60.
Treating cancer
Cancer used to be regarded as an incurable disease, but the situation has changed, as early diagnosis can be made, supplemented by early treatment, thus greatly increasing the hope that cancer can be cured. According to the Medical Dictionary, one of the most effective means of treating cancer is radiation therapy. For cancers of internal organs, surgical removal is the mainstay, supplemented by irradiation. However, there are some cancers that seem to be small in scope on the surface, but may harbor cancer cells that have already metastasized; once there are cancer cells left behind, even if it is a very small amount, it may cause the cancer to recur. Therefore, the area of surgery should be larger, and then irradiated with rays after the surgery to kill the remaining cancer cells and eradicate the cancer.
With the continuous development of radiation therapy, there are many cancer cases that are better treated with radiation therapy than with surgery. Moreover, some cancers are too late to be treated with surgery, so for these patients, they can look to radiation therapy. In the past, the inability to have surgery would have meant despair; clearly, the situation is very different today.
In recent years, the use of gas pedals has gained a great deal of momentum. Because the gas pedal produces rays with a fairly high energy, there is a certain ability to penetrate. For example, X-rays, γ-rays, electron beams, proton beams, neutron beams, meson beams, etc., can pass through the human skin and tissues and reach the tumor. By and large, neutrons have the strongest killing power on cancer cells when irradiated.
Why can radiation therapy be used to treat cancer? That's because the more active the cell division is in the tissue, the less tolerant it is to radiation. Therefore, cellular tissue that is constantly multiplying rapidly and uncontrollably, like cancer cells, is particularly lethal to the rays when they are irradiated. That is exactly the goal of radiotherapy, and it is what is desired. Of course, normal cells can be damaged if irradiated with large doses of radiation. However, by targeting the nests of cancer cells and irradiating them properly with moderate doses of radiation, it is possible to do so in a way that kills only the cancer cells and causes no or little damage to the normal tissues around them.
Archaeological applications
Cosmic space has been continuously emitting a variety of rays to our Earth, which are called cosmic rays. One of these rays is called neutron rays. These neutrons collide with the nuclei of nitrogen atoms in the atmosphere and hit protons. At the same time, a new nuclide is produced, carbon-l4, which is a radioactive isotope of the carbon atom. As a result, the amount of carbon-l4 in the Earth's atmosphere is constantly increasing.
But, as mentioned earlier, the radioactive isotope has a certain life span and it is constantly undergoing radioactive decay. The half-life of carbon-l4 is 5568 years. That is, every 5568 years, the amount of carbon-l4 is destined to decrease by half. In this way, carbon-l4 is constantly being produced and dying at the same time, resulting in a certain equilibrium value for the concentration of radioactive carbon-l4 in the atmosphere.
As we all know, plants on Earth have to ingest carbon in the form of carbon dioxide in order to keep assimilating, growing, and reproducing. In turn, the animals on earth survive by eating plants. Therefore, there is no doubt that the concentration of radiocarbon L4 in the carbon contained in the bodies of plants and animals growing on earth must have reached a certain equilibrium value. The concentration of carbon l4 in living organisms on earth is measured to be 16 ppm, which means that there are 16 grams of carbon 14 in every ton of ordinary carbon.
However, when plants and animals die, the concentration of carbon l4 in the body changes. In other words, the timer of the "history clock" has been set. In this way, various kinds of measurements can be made by measuring the concentration of carbon-14. For example, it is possible to determine the age of wood and human bones from ancient times, and to determine the age of plant and animal fossils and coal. In addition, when did huge geological changes such as volcanic eruptions, earthquakes, flash floods, and other natural phenomena occur in ancient times? By finding the remains of buried trees, etc., at that time and making similar measurements, it is possible to obtain an accurate conclusion. Since the half-life of carbon l4 is 5,568 years, the above method is suitable for measuring the period from 500 years ago to within 30,000 years. For example, China's Loulan female corpse, the age of the identification of the Lop Nor paper is the use of carbon - l4. can be seen, carbon - l4 for the determination of the age of human history, is no better clock.
Security Guard
1. Ion Smoke Alarm
The small flame, due to the lack of early detection, causing a fire, the result of burning houses and property, resulting in casualties. For many years, people have been exploring ways to fire alarm, in order to seek disaster in the bud when it was found. People use a variety of characteristics of the flame burning, has been invented a variety of fire alarm devices. For example, the use of flames containing sunlight does not have a certain wavelength of ultraviolet light made of light-sensitive alarm instruments; the use of flame combustion can make the ambient temperature rise made of temperature-sensitive alarms; the use of visible smoke particles can be made of the characteristics of the light made of the photoelectric smoke alarms and so on.
But how to detect invisible smoke particles to achieve the purpose of early alarm? This will have to resort to radioactive isotopes.
Radioisotope nuclei in the absence of external action can spontaneously decay into another nucleus, while releasing alpha rays, beta rays or gamma rays. The first two kinds of rays are charged, and has a high energy, so when they are shot from the nucleus of the radioactive isotope, through the air, can ionize the air into positive and negative ions and gradually consume their own energy.
As smoke enters the ionized space, it adsorbs certain ions, slowing down ion migration significantly. Accordingly, it can be made into an ionized smoke sensor probe. Ion smoke sensor probe with the control of electrical devices, constituting an automatic fire alarm instrument. Because of the sensitive and reliable, the cost is not high, at home and abroad has been a large number of production of various types of ionic smoke alarm, widely used in hotels, warehouses, libraries, communication centers, television stations, ships and even families, and become the most commonly used fire alarm instruments. Especially with the development of high-rise buildings, the fire design has put forward higher requirements. At present, ionic smoke detectors and other principles made of various fire detectors have been able to connect with the calculator system, not only automatic alarms, but also automatic fire extinguishing, automatic cut-off of air-conditioning systems and control the elevator landing and so on.
Since the ionic smoke detector sensing object is very small particles of smoke, then, not only can it be used as a fire alarm, but also alarm a variety of disasters that may produce smoke, for example, can be made into a detection of certain poisonous gases such as alarm devices.
2. Radioisotope lightning rod
Lightning is a discharge phenomenon in the sky, its instantaneous energy is very large. Being struck by lightning, the place will make the trees touched by the premises explode and catch fire, like hitting a bomb in general. How to avoid lightning strikes?
Shortcuts everyone loves to take, and so does electricity, to take the path of least resistance. Lightning rod is erected in the highest part of the building with a metal rod connected to the ground. The upper end of the rod is pointed, the tip is easy to discharge, forming a small resistance pathway. The charge in the cloud can enter the ground through the lightning rod, the building can be protected from lightning strikes.
Radioisotope lightning rod lightning principle and the principle of ordinary lightning rod is the same. The difference is that the former rely on radioactive isotopes emitted by the ray so that the air near the lightning rod a large number of ionization, and actively open a charge with the cloud connected to the electrical path; and ordinary lightning rod tip can only produce a small number of ions.
The ionization current generated by a radioisotope lightning rod is more than 10,000 times higher than that of an ordinary lightning rod, plus the role of accelerating devices can also be much higher. It can be discharged early, so that no lightning generated in the protected area. It can also reduce the potential outside the protected area. The scope of protection is also much larger. Used as a lightning rod
Most of the radioactive sources on isotope lightning rods are americium-241 sources, which radiate alpha rays and are highly ionizing. Needle on the radioactive material is strictly sealed up, the emission of rays from the action of a very short distance, the building below the people do not have the slightest harm, is absolutely safe.
In summary, nuclear technology to the social life of multi-level all-round penetration, has an extremely rich connotation and extension. It is no exaggeration to say that modern nuclear technology, like electronic technology and material technology, will become an inseparable part of human life with the rapid development of modern construction.
(Excerpted from the website of Hebei Provincial Environmental Protection Bureau: "Introduction to Radioisotopes and Radiation Technology Application Fields")