📚 Applications of Radioactivity | 放射性的应用
Radioactive materials emit radiation in the form of alpha particles, beta particles, or gamma rays. While radiation can be dangerous if not handled properly, it has a wide range of important applications in medicine, industry, agriculture, and scientific research. Understanding these applications requires knowledge of the properties of each type of radiation and how they interact with matter.
放射性物质以α粒子、β粒子或γ射线的形式发射辐射。虽然辐射若处理不当可能造成危险，但它在医学、工业、农业和科学研究等领域有着广泛而重要的应用。理解这些应用需要了解各类辐射的性质及其与物质的相互作用方式。
1. Properties of Radiation Types | 辐射类型的性质
To understand how radioactivity is applied, we must first recall the key properties of the three main types of radiation. Alpha particles are helium nuclei, consisting of two protons and two neutrons. They are highly ionising but have very low penetrating power — a few centimetres of air or a sheet of paper can stop them. Beta particles are fast-moving electrons, which are moderately ionising and can penetrate several millimetres of aluminium. Gamma rays are electromagnetic waves with very high frequency, which are weakly ionising but highly penetrating, requiring thick lead or concrete to absorb them.
要理解放射性的应用，我们必须首先回顾三种主要辐射类型的关键性质。α粒子是氦原子核，由两个质子和两个中子组成。它们电离能力极强，但穿透能力很弱——几厘米的空气或一张纸就能阻挡它们。β粒子是高速运动的电子，电离能力中等，能穿透几毫米厚的铝。γ射线是频率极高的电磁波，电离能力弱但穿透力极强，需要厚铅板或混凝土才能吸收。
The choice of a particular radioactive isotope for a given application depends on its half-life, the type of radiation it emits, and its energy. A suitable isotope must emit the right type of radiation and remain active for an appropriate length of time.
为特定应用选择合适的放射性同位素，取决于其半衰期、发射的辐射类型及其能量。合适的同位素必须发射正确的辐射类型，并在恰当的时间长度内保持活性。
2. Medical Tracers | 医用示踪剂
One of the most common medical applications of radioactivity is the use of radioactive tracers. A tracer is a small amount of a radioactive substance introduced into the body, allowing doctors to track the movement of particular chemicals or fluids through the body. For example, iodine-131 is absorbed by the thyroid gland, allowing doctors to image the thyroid and detect abnormalities such as tumours or overactive tissue.
放射性在医学中最常见的应用之一是使用放射性示踪剂。示踪剂是将少量放射性物质引入体内，使医生能够追踪特定化学物质或液体在体内的运动。例如，碘-131会被甲状腺吸收，使医生能够对甲状腺成像，检测肿瘤或组织功能亢进等异常。
For imaging, technetium-99m is widely used because it emits gamma rays, which can pass through the body and be detected by an external camera. Importantly, technetium-99m has a short half-life of about six hours, meaning the patient receives a low dose of radiation and the radioactivity quickly decays away after the scan is complete.
在成像方面，锝-99m被广泛使用，因为它发射γ射线，能够穿透人体并被外部摄像机检测到。重要的是，锝-99m的半衰期约为6小时，这意味着患者接受的辐射剂量较低，扫描完成后放射性会迅速衰减。
Alpha particles are never used as medical tracers because their short range and high ionising power make them hazardous inside the body. Beta particles are sometimes used but must be chosen with care. Gamma tracers are ideal for external detection, as gamma radiation can pass through tissue to reach the detector.
α粒子从不被用作医用示踪剂，因为它们射程短、电离能力强，在体内非常危险。β粒子有时会被使用，但须谨慎选择。γ示踪剂最适合外部检测，因为γ辐射可以穿过组织到达探测器。
3. Radiotherapy for Cancer Treatment | 癌症放射治疗
Radiotherapy uses the ionising ability of radiation to destroy cancerous cells. High-energy gamma rays are directed at a tumour from outside the body, a technique known as external beam radiotherapy. The radiation damages the DNA of the cancer cells, causing them to die or stop dividing. Healthy cells are partially protected by carefully directing the beams and rotating the source around the patient so that the tumour receives the highest dose.
放射治疗利用辐射的电离能力来摧毁癌细胞。高能γ射线从体外对准肿瘤照射，这种技术称为外照射放射治疗。辐射会损伤癌细胞的DNA，使其死亡或停止分裂。通过精心调整射束方向并围绕患者旋转放射源，使肿瘤受到最高剂量，从而部分保护健康细胞。
For internal radiotherapy, a technique called brachytherapy places a small radioactive source, often iodine-125 or iridium-192, directly inside or near the tumour. This delivers a high dose to the tumour while sparing surrounding healthy tissue. Beta-emitting isotopes can also be used for treating superficial conditions such as skin cancer, because beta particles penetrate only a short distance.
对于体内放射治疗，一种称为近距离治疗的技术将小型放射源（常用碘-125或铱-192）直接放置在肿瘤内部或附近。这样既能向肿瘤输送高剂量，又能保护周围健康组织。β放射同位素也可用于治疗皮肤癌等表浅疾病，因为β粒子穿透距离短。
Cobalt-60 is another important source used in radiotherapy. It emits high-energy gamma rays and has a half-life of approximately 5.3 years, making it possible to store and use the source for a relatively long period before replacement is needed.
钴-60是放射治疗中另一种重要的放射源。它发射高能γ射线，半衰期约为5.3年，使得放射源可以储存和使用较长时间后才需要更换。
4. Sterilisation of Medical Equipment | 医疗器械灭菌
Gamma radiation is used to sterilise medical equipment such as syringes, surgical gloves, and catheters. These items are packaged and then exposed to intense gamma radiation, which kills all microorganisms, including bacteria, viruses, and fungi. The advantage of radiation sterilisation is that it can be done after packaging, so the equipment remains sterile until opened.
γ辐射用于对注射器、手术手套和导管等医疗器械进行灭菌。这些物品被包装后暴露于强γ辐射下，以杀死所有微生物，包括细菌、病毒和真菌。辐射灭菌的优点是可以在包装完成后进行，因此设备在打开使用前始终保持无菌状态。
Unlike heat sterilisation, which can damage heat-sensitive plastics and materials, gamma sterilisation does not significantly raise the temperature, so it is suitable for a wide range of modern medical materials. This process is safe because the equipment itself does not become radioactive; it is merely exposed to radiation, much like food is heated in a microwave without becoming a source of microwaves.
与会损坏热敏塑料和材料的热力灭菌不同，γ灭菌不会显著升高温度，因此适用于各种现代医用材料。这一过程是安全的，因为设备本身并不会变得具有放射性；它只是被辐射照射，就像食物在微波炉中被加热但不会成为微波源一样。
5. Carbon Dating | 碳定年法
Carbon dating is a technique used to determine the age of archaeological and geological samples. It is based on the fact that carbon-14, a radioactive isotope of carbon with a half-life of 5730 years, is constantly formed in the atmosphere by cosmic ray bombardment. Living organisms absorb carbon-14 along with ordinary carbon-12 from the environment, and the ratio of carbon-14 to carbon-12 in a living organism remains constant.
碳定年法是一种用于确定考古和地质样本年龄的技术。其原理基于碳-14这一碳的放射性同位素（半衰期为5730年）在大气中通过宇宙射线轰击不断产生。生物体从环境中吸收碳-14和普通碳-12，活生物体内碳-14与碳-12的比例保持恒定。
When an organism dies, it stops absorbing carbon, and the carbon-14 it contains gradually decays back to nitrogen-14 through beta emission. By measuring the remaining proportion of carbon-14 in a sample and comparing it to the known initial ratio, scientists can calculate how long ago the organism died.
当生物体死亡后，它停止吸收碳，其体内的碳-14通过β发射逐渐衰变回氮-14。通过测量样本中剩余的碳-14比例，并与已知的初始比例进行比较，科学家可以计算出该生物体死亡的时间。
The age of a sample can be found using the decay equation:
样本年龄可通过衰变方程求得：
N = N₀ × (½)ⁿ
where N is the remaining count rate, N₀ is the initial count rate, and n is the number of half-lives that have elapsed. Carbon dating is reliable for samples up to about 50,000 years old, as beyond that the amount of remaining carbon-14 is too small to measure accurately.
其中N为剩余计数率，N₀为初始计数率，n为已过去的半衰期数。碳定年法对距今约5万年以内的样本可靠，因为超过这个范围后，剩余的碳-14量太少而无法精确测量。
6. Smoke Detectors | 烟雾探测器
Ionisation smoke detectors are found in many homes and public buildings. They contain a small amount of americium-241, which is an alpha emitter with a half-life of 432 years. The alpha particles ionise the air inside the detector, creating a small electric current between two electrodes. When smoke particles enter the detector, they attach to the ions and reduce the current. The drop in current triggers the alarm.
离子型烟雾探测器广泛用于家庭和公共建筑中。它们含有少量镅-241，这是一种α放射源，半衰期为432年。α粒子使探测器内的空气电离，在两级之间产生微小电流。当烟雾颗粒进入探测器时，它们附着在离子上并使电流减小，电流下降便会触发警报。
Alpha radiation is chosen for this application because its short range means the particles are stopped by the air within the detector and do not pose a significant hazard outside. The long half-life ensures that the source remains functional for many years, and the very small amount used poses minimal risk to household members.
选择α辐射是因为其射程短，粒子会被探测器内的空气阻挡，不会对外界构成显著危害。长半衰期确保放射源能够多年正常运作，且使用的量非常小，对家庭成员构成的健康风险极低。
7. Thickness Gauges in Industry | 工业厚度测量仪
In manufacturing, radioactive sources are used to monitor and control the thickness of materials such as paper, plastic sheeting, and aluminium foil. A beta-emitting source is placed on one side of the material, and a detector is placed on the other side. As the material passes between them, the amount of radiation reaching the detector depends on the thickness of the material.
在制造业中，放射源被用于监测和控制纸张、塑料薄膜和铝箔等材料的厚度。β放射源放置在材料一侧，探测器放置在另一侧。当材料从两者之间通过时，到达探测器的辐射量取决于材料厚度。
If the material becomes too thick, more radiation is absorbed and the detector reading drops. The control system then adjusts the rollers to reduce the thickness. Conversely, if the material is too thin, the detector reading rises and the rollers are adjusted to increase the thickness. This automated feedback system ensures consistent product quality with no physical contact with the material.
如果材料变得过厚，吸收的辐射增多，探测器读数下降，控制系统便调整辊轮以减小厚度。反之，如果材料过薄，探测器读数升高，辊轮就会被调整以增加厚度。这种自动化反馈系统无需接触材料即可确保产品品质的一致。
Beta particles are preferred for paper and thin foils because their penetrating power matches the range of thicknesses involved. For thicker materials such as steel plates, gamma sources are used instead, as gamma rays can penetrate much greater thicknesses.
β粒子适合测量纸张和薄箔，因为其穿透能力与所涉及的厚度范围相匹配。对于钢板等较厚材料，则改用γ放射源，因为γ射线能穿透更大的厚度。
8. Controlling Electricity in Industry | 工业静电消除
Ionisation can also be used to eliminate static electric charges, which is important in industries such as electronics manufacturing and printing. Polonium-210, a pure alpha emitter, is often used in anti-static devices. The alpha particles ionise the surrounding air, and the ions neutralise the static charges on materials such as films, fabrics, and paper. This prevents problems such as dust attraction, paper jams, and damage to sensitive electronic components.
电离作用也可用于消除静电，这在电子制造和印刷等行业中非常重要。钋-210是一种纯α放射源，常用于静电消除装置。α粒子电离周围空气，产生的离子中和薄膜、织物和纸张等材料上的静电荷，从而防止灰尘吸附、纸张卡堵以及对敏感电子元件的损坏。
The use of alpha radiation for this purpose is appropriate because the ionising power of alpha particles is high, creating many ions in a short distance, while their short range confines the effect to a local area near the source. This makes the device effective yet safe to operate.
选择α辐射是因为α粒子的电离能力强，能在短距离内产生大量离子，同时其射程短使效果局限于放射源附近的局部区域，这使装置既有效又安全。
9. Food Irradiation | 食品辐照
Food irradiation is a process in which food is exposed to gamma radiation to kill bacteria, mould, and insects, thereby extending its shelf life and improving food safety. It is used for products such as spices, fruits, meat, and poultry. The radiation disrupts the DNA of microorganisms, preventing them from reproducing and spoiling the food.
食品辐照是将食物暴露于γ辐射以杀灭细菌、霉菌和昆虫，从而延长保质期并提高食品安全的过程。它被用于香料、水果、肉类和禽肉等产品。辐射破坏微生物的DNA，防止它们繁殖和使食物变质。
Irradiated food does not become radioactive, just as a chest X-ray does not make a person radioactive. The World Health Organization has confirmed that irradiated food is safe for consumption, and this technique helps reduce food waste worldwide.
经过辐照的食物不会变得具有放射性，就像胸部X光检查不会使人具有放射性一样。世界卫生组织已确认辐照食品可安全食用，这项技术有助于减少全球食物浪费。
10. Radioactive Waste Disposal | 放射性废料处理
While radioactivity has many beneficial applications, the disposal of radioactive waste remains a serious challenge. Low-level waste, such as contaminated clothing and laboratory equipment, can be compacted and stored in sealed containers. Intermediate-level waste, such as resins and chemical sludges, is often solidified in cement within steel drums. High-level waste, mainly spent nuclear fuel, must be carefully managed because it remains highly radioactive and emits heat for thousands of years.
尽管放射性有许多有益的应用，放射性废料的处理仍然是一个严峻的挑战。低放射性废物，如受污染的衣服和实验设备，可被压缩并密封储存。中放射性废物，如树脂和化学污泥，通常在钢桶中用水泥固化。高放射性废物主要是乏核燃料，必须谨慎管理，因为在数千年内它仍具有强放射性并释放热量。
High-level waste is currently stored in specially designed facilities with water-cooled pools or dry cask storage systems. The long half-lives of isotopes such as caesium-137 (30 years) and strontium-90 (29 years) mean that waste must remain safely contained for many generations. Research into deep geological disposal aims to store high-level waste in stable underground formations where it will remain isolated from the environment for thousands of years.
高放射性废物目前储存在专门设计的设施中，采用水冷池或干式桶储存系统。铯-137（30年）和锶-90（29年）等同位素的半衰期很长，意味着废物必须在许多代人的时间内保持安全封闭。深地质处置研究旨在将高放射性废物储存在稳定的地下岩层中，使其在数千年内与环境隔绝。
11. Choosing the Right Isotope | 选择正确的同位素
Selecting a radioactive isotope for a specific application requires careful consideration of several factors. The type of radiation emitted must suit the purpose: alpha for short-range ionisation, beta for medium penetration, and gamma for deep penetration or external detection. The half-life must be long enough for the application to be practical but short enough that the source does not remain dangerous indefinitely.
为特定应用选择放射性同位素需要仔细考虑多个因素。发射的辐射类型必须符合用途：α用于短程电离，β用于中等穿透，γ用于深穿透或外部检测。半衰期必须足够长以保证应用的实用性，但又要足够短，使放射源不会无限期地保持危险性。
For example, a tracer used in medical imaging must have a short half-life so the patient’s radiation dose is minimal and the body quickly clears the radioactivity. In contrast, a smoke detector source needs a very long half-life so that it does not need frequent replacement. The energy and chemical properties of the isotope also determine whether it can be attached to a particular compound or whether it can penetrate the required thickness of material.
例如，用于医学成像的示踪剂必须具有短半衰期，以最大限度地减少患者的辐射剂量，使身体迅速清除放射性。相比之下，烟雾探测器中的放射源需要非常长的半衰期，以免频繁更换。同位素的能量和化学性质也决定了它能否附着于特定化合物，或能否穿透所需厚度的材料。
12. Safety and Risk Management | 安全与风险管理
Because radiation can damage living cells and cause mutations or cancer, strict safety measures govern all uses of radioactive materials. Three fundamental principles guide radiation protection: minimising time of exposure, maximising distance from the source, and using shielding. Radioactive sources are handled with remote tools, stored in lead-lined containers, and clearly labelled with the international trefoil symbol for ionising radiation.
由于辐射会损伤活细胞并可能引起突变或癌症，所有放射性材料的使用都须遵守严格的安全措施。辐射防护的三项基本原则是：尽量减少照射时间、尽量增大与放射源的距离、使用屏蔽材料。放射源使用远程工具操作，存放在铅衬容器中，并明确标有国际电离辐射三叶形标志。
Workers who handle radioactive materials wear film badges or electronic dosimeters to monitor their accumulated exposure. Regular training, strict regulatory oversight, and careful waste management all contribute to ensuring that the benefits of radioactivity can be enjoyed while keeping risks acceptably low. In the IGCSE syllabus, you should be able to evaluate these risks and benefits for each application you study.
处理放射性材料的工人佩戴胶片剂量计或电子剂量计以监测累计照射量。定期培训、严格的监管监督和谨慎的废料管理都有助于确保我们既能享受放射性的益处，又能将风险控制在可接受的范围内。在IGCSE课程中，你应当能够针对所学的每项应用评估其风险与收益。
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