📚 Uses of Radioactive Isotopes | 放射性同位素的应用
Radioactive isotopes are atoms with an unstable nucleus that emit radiation to become more stable. In IGCSE Edexcel Science, we explore how these isotopes, despite their hazards, have vital applications in medicine, industry, agriculture, and archaeology. This article covers the key concepts, uses, and safety measures required for the exam, providing a balanced view of risks and benefits.
放射性同位素是原子核不稳定、通过放出辐射来变得稳定的原子。在IGCSE Edexcel科学课程中，我们探讨这些同位素尽管有危害，却在医学、工业、农业和考古学中有着重要应用。本文涵盖考试所需的关键概念、用途和安全措施，提供对风险与收益的平衡看法。
1. What Are Radioactive Isotopes? | 什么是放射性同位素？
An isotope is an atom of the same element with a different number of neutrons. Radioactive isotopes (radioisotopes) have unstable nuclei that spontaneously decay, emitting ionising radiation. The decay continues until a stable nucleus is formed. Examples include carbon-14 (¹⁴C), iodine-131 (¹³¹I), and cobalt-60 (⁶⁰Co).
同位素是同一种元素中子数不同的原子。放射性同位素（放射性同位素）具有不稳定的原子核，会自发衰变，放出电离辐射。衰变持续进行，直到形成稳定的原子核。例子包括碳-14（¹⁴C）、碘-131（¹³¹I）和钴-60（⁶⁰Co）。
2. Types of Radiation | 放射类型
Radioisotopes emit alpha (α), beta (β), or gamma (γ) radiation. Alpha particles (⁴He) are heavy and highly ionising but can be stopped by paper or a few cm of air. Beta particles (⁻⁰e) are lighter, moderately ionising, and stopped by thin aluminium. Gamma rays (γ) are electromagnetic waves, weakly ionising, very penetrating, and require thick lead or concrete to absorb. The type of radiation determines the isotope's application and required shielding.
放射性同位素释放α粒子、β粒子或γ射线。α粒子（⁴He）质量大、电离能力强，但能被纸或几厘米空气阻挡。β粒子（⁻⁰e）较轻，电离能力中等，可被薄铝片阻挡。γ射线（γ）是电磁波，电离能力弱，穿透力极强，需要厚铅板或混凝土来吸收。辐射类型决定了同位素的用途和所需的防护。
3. Half-Life and Its Importance | 半衰期及其重要性
table for radiotherapy or industrial gauges. Carbon-14 has a long half-life (5730 years), ideal for dating ancient organic material.
半衰期（t₁/₂）是指放射性样品中一半的原子核发生衰变，或计数率减半所需的时间。半衰期极短的同位素用作医学示踪剂，因为它们衰变快，可减少患者受到的辐射剂量。半衰期长的同位素（如⁶⁰Co，半衰期5.27年）适合放射治疗或工业仪表。碳-14的半衰期很长（5730年），非常适合对古代有机物质定年。
4. Medical Uses: Tracers | 医疗应用：示踪剂
diation can be detected outside the body, and its short half-life minimises dose. Tracers can be used to investigate kidney function, monitor blood flow, or locate tumours. The patient drinks or is injected with a radioactive solution, and a gamma camera detects the radiation to form an image.
放射性示踪剂是将放射性同位素引入体内，以追踪物质运动或检测异常。发射γ射线的同位素，如锝-99m（⁹⁹ᵐTc，半衰期约6小时）是理想选择，因为γ射线可在体外检测，且半衰期短可将剂量降至最低。示踪剂可用于检查肾功能、监测血流或定位肿瘤。患者饮用或注射放射性溶液，伽玛相机检测辐射形成图像。
5. Medical Uses: Radiotherapy | 医疗应用：放射治疗
Radiotherapy uses high doses of ionising radiation to destroy cancer cells. Cobalt-60 (⁶⁰Co) is a common gamma source used in external beam radiotherapy. The gamma rays are directed at the tumour from different angles to minimise damage to surrounding healthy tissue. Beta-emitting sources, such as strontium-90 (⁹⁰Sr), may be used in brachytherapy, where a sealed source is placed close to or inside the tumour. The goal is to damage the DNA of cancer cells so they cannot divide, leading to tumour shrinkage.
放射治疗使用高剂量的电离辐射来破坏癌细胞。钴-60（⁶⁰Co）是常见的外部射线放射治疗中使用的伽玛源。伽玛射线从不同角度对准肿瘤，以尽量减少对周围健康组织的伤害。β放射源如锶-90（⁹⁰Sr）可用于近距离治疗，即将密封的放射源置于肿瘤附近或内部。目的是破坏癌细胞的DNA，使其无法分裂，导致肿瘤缩小。
6. Industrial Uses: Thickness Control | 工业应用：厚度控制
In manufacturing, radioisotopes are used to control the thickness of materials such as paper, plastic, and metal foil. A beta source (e.g., ⁸⁵Kr) is placed on one side of the material, and a detector on the other. If the material becomes too thick, fewer beta particles reach the detector, and the system automatically adjusts the rollers to reduce thickness. This non-contact method allows continuous monitoring without stopping production.
在制造业中，放射性同位素用于控制纸张、塑料和金属箔等材料的厚度。β源（如⁸⁵Kr）放置在材料一侧，另一侧是探测器。如果材料过厚，到达探测器的β粒子减少，系统会自动调整轧辊以减小厚度。这种非接触方法可以在不停产的情况下连续监控。
7. Industrial Uses: Leak Detection | 工业应用：泄漏检测
Gamma-emitting isotopes are added to fluids in pipelines to detect leaks. A small amount of radioactive material is injected, and detectors placed along the pipe track its movement. If a leak occurs, a build-up of radioactivity will be detected outside the pipe. This method is very sensitive and can locate underground leaks without extensive digging.
在管道中，加入发射γ射线的同位素来检测泄漏。注入少量放射性物质，沿管道放置探测器追踪其运动。如果发生泄漏，会在管道外检测到放射性积聚。这种方法非常灵敏，可无需大量挖掘就定位地下泄漏。
8. Agricultural and Food Uses | 农业与食品用途
Radioisotopes help in plant nutrition studies by using phosphorus-32 (³²P) as a tracer to understand how fertilisers are absorbed. They are also used in food irradiation, where gamma rays from ⁶⁰Co or ¹³⁷Cs kill bacteria, parasites, and insects, extending shelf life and preventing sprouting in potatoes and onions. Irradiated food does not become radioactive and is considered safe by health authorities.
放射性同位素通过使用磷-32（³²P）作为示踪剂，帮助进行植物营养研究，以了解肥料的吸收方式。它们也用于食品辐照，来自⁶⁰Co或¹³⁷Cs的伽玛射线可杀灭细菌、寄生虫和昆虫，延长保质期，并防止马铃薯和洋葱发芽。辐照食品不会变为放射性，卫生当局认为其安全。
9. Carbon Dating | 碳年代测定
Carbon-14 dating is used to estimate the age of once-living materials such as wood, bone, or cloth. Living organisms absorb ¹⁴C from the atmosphere; when they die, the ¹⁴C begins to decay with a half-life of 5730 years without replacement. By measuring the remaining ¹⁴C activity and comparing it to the initial amount, archaeologists can calculate the age of samples up to about 50 000 years old.
碳-14定年法用于估算曾活生物体如木材、骨骼或布料的年龄。活的生物体从大气中吸收¹⁴C；死后，¹⁴C开始衰变，半衰期为5730年，且不再补充。通过测量剩余的¹⁴C活度并与初始量比较，考古学家可以计算样品的年代，最多约5万年。
10. Safety Precautions | 安全注意事项
Handling radioactive sources requires strict safety measures to minimise exposure. Workers follow the ALARA principle (As Low As Reasonably Achievable), using distance, shielding, and minimising time of exposure. Sources are stored in lead-lined containers and are transferred with tongs or remote-handling tools. Personal protective equipment and radiation badges monitor cumulative dose. For medical patients, the benefits must outweigh the risks of radiation.
处理放射源需要严格的安全措施以尽量减少暴露。工作人员遵循ALARA原则（合理可行尽量低），采用距离、屏蔽和缩短暴露时间。放射源存放在铅衬容器中，用钳子或遥控工具转移。个人防护设备和辐射徽章监测累计剂量。对医学患者，必须确保辐射的益处大于风险。
11. Contamination vs. Irradiation | 污染与辐照
These two terms are often confused. Irradiation is the process of being exposed to radiation without direct contact with the source; the object does not become radioactive. Contamination means radioactive material is present on or inside an object, making it radioactive. For example, a patient undergoing an X-ray is irradiated but not contaminated. If a radioactive powder is spilled on a bench, the bench becomes contaminated.
这两个术语常被混淆。辐照是受到辐射照射而不直接接触放射源的过程；物体不会变得具有放射性。污染意味着放射性物质存在于物体表面或内部，使其成为放射性。例如，接受X射线照射的病人是受辐照，而非被污染。如果放射性粉末洒在实验台上，则实验台被污染。
12. Summary | 总结
Radioactive isotopes are invaluable tools across many fields. Understanding the properties of alpha, beta, and gamma radiation, and the concept of half-life, enables us to select the right isotope for each task. From detecting cancer to preserving food and dating historical artefacts, their benefits are immense when used responsibly and with appropriate safety measures.
放射性同位素是许多领域的重要工具。了解α、β和γ辐射的性质以及半衰期的概念，使我们能够为每项任务选择合适的同位素。从检测癌症到保存食品以及确定文物的年代，如果负责任地使用并采取适当的安全措施，它们带来的益处是巨大的。
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