📚 Hazards, Uses and Background Radiation | 辐射的危害、用途与背景辐射
Understanding the nature of ionising radiation is not just about nuclear equations and half‑life – it is also about how we live alongside radiation every day. This topic explores the real‑world dangers of alpha, beta and gamma radiation, the measures we take to stay safe, and the many ways radiation is used in medicine, industry and energy production. It also introduces the concept of background radiation, helping you appreciate that radioactivity is a natural part of our environment.
理解电离辐射的本质，不仅关乎核方程和半衰期，也涉及我们如何每天与辐射共处。本主题将探讨 α、β 和 γ 辐射在现实世界中的危险、我们采取的安全防护措施，以及辐射在医疗、工业和能源生产中的多种用途。同时引入背景辐射的概念，帮助你认识到，放射性是自然环境的一部分。
1. Ionising Radiation and Living Tissue | 电离辐射与生物组织
All three types of nuclear radiation – alpha, beta and gamma – are ionising, meaning they can knock electrons out of atoms. Inside the human body, ionisation can break chemical bonds in DNA molecules, leading to cell death, mutations or uncontrolled cell division that may develop into cancer. Alpha particles are the most strongly ionising but have a short range and cannot penetrate the outer layer of dead skin. However, if an alpha source is inhaled or swallowed, it can cause intense local damage to internal organs.
三种核辐射（α、β 和 γ）都具有电离能力，意味着它们能从原子中击出电子。在人体内，电离作用会打断DNA分子的化学键，导致细胞死亡、突变或细胞不受控制地分裂，进而可能发展成癌症。α 粒子的电离能力最强，但射程很短，无法穿透皮肤表面的死皮。然而，一旦 α 源被吸入或吞入，就会对内脏器官造成强烈的局部损害。
Beta particles are moderately ionising and can penetrate the skin to reach living cells beneath. They pose a greater external hazard than alpha radiation. Gamma rays are the least ionising per collision but are highly penetrating, able to pass right through the body. They cause damage along their entire path and require thick shielding to reduce exposure.
β 粒子的电离能力中等，能穿透皮肤抵达下面的活细胞，所以外部危害比 α 辐射更大。γ 射线每次碰撞的电离能力最弱，但穿透力极强，能直接穿过人体，在整个路径上造成损伤，需要厚实的屏蔽才能减少照射。
2. Safety Precautions with Radioactive Sources | 使用放射源的安全防护措施
When handling radioactive materials, the fundamental principle is to minimise exposure. This is achieved through three key measures: reducing time of exposure, increasing distance from the source, and using appropriate shielding. In a school laboratory, sources are stored in lead‑lined containers and handled with long‑handled tongs to keep them as far from the body as possible. The source should never be pointed towards anyone and should be returned to its container immediately after use.
处理放射性物质时，基本原则是尽量减少照射。这通过三项关键措施实现：缩短照射时间、增大与源的距离、以及使用合适的屏蔽。在学校实验室中，放射源保存在铅衬容器里，并用长柄钳子操作，使其尽可能远离身体。放射源绝不可指向任何人，使用后应立即放回容器中。
Workers in nuclear industries wear film badges that record cumulative radiation dose. Areas with high radiation levels are clearly marked and access is restricted. In hospitals, staff administering radiotherapy or diagnostic isotopes wear protective aprons and stay behind lead screens. For gamma sources, thick lead or concrete shielding is essential, while plastic or aluminium is sufficient to stop beta particles.
核工业工作人员佩戴记录累积辐射剂量的胶片徽章。高辐射区域有明确标识并限制进入。在医院里，执行放射治疗或诊断性同位素操作的工作人员穿戴防护围裙，并躲在铅屏后方。对 γ 源而言，厚实的铅或混凝土屏蔽必不可少，而塑料或铝就足以阻挡 β 粒子。
3. Background Radiation – A Constant Companion | 背景辐射——形影不离的伙伴
Background radiation is the low‑level ionising radiation that is always present in our environment. It comes from both natural and artificial sources, and its level can vary depending on geographical location and lifestyle. The average effective dose a person in the UK receives is about 2.7 millisieverts (mSv) per year. This might seem alarming, but our cells have repair mechanisms that can correct much of the low‑level damage caused by background radiation.
背景辐射是环境中始终存在的低强度电离辐射。它有天然和人工两种来源，水平因地而异，也受生活方式影响。在英国，每人每年平均接受约2.7毫希沃特的有效剂量。这听起来可能令人担忧，但我们的细胞具有修复机制，能纠正背景辐射造成的大部分低水平损伤。
4. Natural Sources of Background Radiation | 背景辐射的天然来源
A significant portion of background radiation originates from natural sources. Radon gas, produced by the decay of uranium in rocks, seeps from the ground and can accumulate in buildings, especially in areas with granite bedrock. It is the largest single contributor to background dose in many regions. Cosmic rays from outer space constantly bombard the Earth; their intensity increases with altitude, giving airline crews and mountain dwellers a higher annual dose.
背景辐射的很大一部分来自天然源。由岩石中铀衰变产生的氡气从地面渗出，会在建筑物内积聚，特别是在花岗岩基岩地区。在许多地区，氡气是背景剂量的最大单一贡献者。来自外太空的宇宙射线持续轰击地球；其强度随海拔增高而增加，使机组人员和山区居民的年剂量更高。
Additionally, radioactive isotopes such as carbon‑14 and potassium‑40 are present in our food and water, and even within our own bodies. Gamma radiation from rocks and soil also contributes to external terrestrial exposure. These natural sources account for roughly 85 % of the average background dose in the UK.
此外，食物、饮水，甚至我们体内都存在碳‑14、钾‑40等放射性同位素。来自岩石和土壤的γ辐射也构成外部陆地照射。这些天然源约占英国平均背景剂量的85 %。
5. Artificial Sources of Background Radiation | 背景辐射的人工来源
Artificial background radiation is dominated by medical procedures, particularly X‑ray imaging, CT scans and the use of radioactive tracers. A single CT scan can give a dose equivalent to several years of natural background exposure. Industrial activities such as nuclear power generation, weapons testing fallout and the disposal of radioactive waste also add small amounts, though strict regulations keep these contributions low.
人工背景辐射以医学程序为主，尤其是X射线成像、CT扫描以及放射性示踪剂的使用。一次CT扫描的剂量可能相当于数年的天然背景照射。核能发电、武器试验沉降物和放射性废物处置等工业活动也会增加少量辐射，但严格的法规使这些贡献保持在较低水平。
Other artificial sources include building materials that contain naturally occurring radioactive substances and consumer products like smoke detectors that use americium‑241. In total, artificial sources typically contribute around 15 % of the average annual background dose.
其他人工源包括含有天然放射性物质的建筑材料，以及使用镅‑241的烟雾探测器等消费品。总体而言，人工来源通常约占年平均背景剂量的15 %。
6. Medical Uses – Diagnosis with Radioactive Tracers | 医疗用途——放射性示踪剂诊断
Radioisotopes are invaluable in modern medicine for both diagnosis and treatment. In diagnostic imaging, a small amount of a gamma‑emitting tracer, such as technetium‑99m, is injected into the patient. The tracer is chosen because it is taken up by specific organs, and its distribution is detected by a gamma camera to produce a detailed image. Technetium‑99m is ideal because it emits gamma rays easily detected outside the body, has a short half‑life of 6 hours, and decays to a relatively stable isotope, minimising the patient’s dose.
放射性同位素在现代医学中对于诊断和治疗都极为宝贵。在诊断成像中，少量发射γ射线的示踪剂（如锝‑99m）被注入患者体内。选择这种示踪剂，是因为它会被特定器官吸收，然后通过γ相机检测其分布，生成详细图像。锝‑99m是理想的选择，因为它发射的γ射线容易被体外探测器捕捉，半衰期仅6小时，且衰变产物较为稳定，从而将患者剂量降至最低。
Positron emission tomography (PET) scanners use isotopes such as fluorine‑18, which emits positrons. These annihilate with electrons in the body to produce gamma rays that are detected and used to map metabolic activity, extremely useful in cancer diagnosis.
正电子发射断层扫描（PET）使用氟‑18等同位素，它们发射正电子。正电子与体内电子湮灭产生γ射线，被探测后用于绘制代谢活动图谱，在癌症诊断中极为有用。
7. Medical Uses – Radiotherapy | 医疗用途——放射治疗
Radiotherapy exploits the fact that rapidly dividing cancer cells are more sensitive to ionising radiation than normal cells. By carefully targeting tumours with beams of gamma rays from cobalt‑60 or high‑energy X‑rays from a linear accelerator, doctors can destroy cancerous tissue while limiting damage to surrounding healthy cells. In some cases, small sealed sources (brachytherapy) are implanted directly into or near the tumour to deliver a high localised dose.
放射治疗利用的是快速分裂的癌细胞比正常细胞对电离辐射更敏感这一特点。通过用钴‑60的γ射线束或直线加速器产生的高能X射线精确对准肿瘤，医生可以消灭癌变组织，同时限制对周围健康细胞的损伤。某些情况下，还可以将小型密封源（近距治疗）直接植入肿瘤内部或附近，以释放高局部剂量。
One challenge is that normal tissues in the beam path also receive some dose, so treatment is often divided into small fractions given over several weeks. This allows healthy tissue time to repair between sessions while progressively destroying the tumour.
一个难点在于，射线路径上的正常组织也会受到一定剂量，因此治疗通常分成若干小分次，在数周内进行。这使得健康组织在两次治疗之间有修复时间，同时逐步摧毁肿瘤。
8. Industrial Uses – Tracers and Thickness Gauges | 工业用途——示踪剂与厚度计
In industry, radioactive tracers can detect leaks in underground pipes without the need for excavation. A small amount of gamma‑emitting isotope is added to the fluid in the pipe, and a detector moved along the surface finds where radiation levels increase, pinpointing the leak. The short half‑life of the tracer ensures no long‑term contamination risk.
在工业中，放射性示踪剂能检测地下管道的泄漏，无需挖开地面。将少量发射γ射线的同位素加入管道流体中，探测器沿地表移动时发现辐射水平升高的位置，从而精确定位泄漏点。示踪剂的短半衰期可确保无长期污染风险。
Thickness gauges use the penetrating power of beta or gamma radiation to monitor the thickness of materials such as paper, plastic film or sheet metal during production. A source is placed on one side and a detector on the other; the amount of radiation reaching the detector depends on the material’s thickness. If the thickness varies, the signal changes and automatic adjustments can be made. Beta sources are used for thin materials, gamma for thicker ones.
厚度计利用β或γ辐射的穿透力，在生产过程中监控纸张、塑料薄膜或金属板的厚度。一侧放置放射源，另一侧放置探测器；到达探测器的辐射量取决于材料的厚度。如果厚度变化，信号随之改变，系统可自动调整。β源用于薄材料，γ源用于较厚的材料。
9. Sterilisation of Equipment and Food | 设备与食品的辐照灭菌
Gamma radiation from cobalt‑60 is widely used to sterilise single‑use medical equipment such as syringes, surgical gloves and dressings. The high‑energy gamma rays penetrate sealed packaging and destroy bacteria, viruses and fungi without heating the items, a process known as cold sterilisation. This is vital for ensuring sterile supplies reach hospitals safely.
钴‑60的γ辐射被广泛用于对一次性医疗器材（如注射器、手术手套和敷料）进行灭菌。高能γ射线穿透密封包装，在无需加热的情况下杀灭细菌、病毒和真菌，这一过程称为冷灭菌。这对于确保无菌用品安全送达医院至关重要。
Similarly, food irradiation uses ionising radiation to kill pathogens and slow down ripening or sprouting. It extends shelf life and improves food safety without making the food radioactive. The process is carefully regulated, and irradiated food must be labelled in many countries.
类似地，食品辐照利用电离辐射杀灭病原体，延缓成熟或发芽。它延长了保质期，提高了食品安全性，又不会使食物本身具有放射性。该过程受到严格监管，许多国家要求辐照食品必须标注。
10. Nuclear Power – Energy with a Hazard | 核能——有危害的能源
Nuclear power stations use the energy released by nuclear fission of uranium‑235 or plutonium‑239 to generate electricity. The fission process releases a large amount of heat, which turns water into steam that drives turbines. A key advantage is that no carbon dioxide is emitted during operation, making nuclear energy a low‑carbon alternative to fossil fuels.
核电站利用铀‑235或钚‑239核裂变释放的能量来发电。裂变过程释放大量热量，将水转化为蒸汽驱动汽轮机。一个关键优势是运行时不排放二氧化碳，使核能成为替代化石燃料的低碳选择。
However, the hazards are significant. The reactor core becomes intensely radioactive, producing a range of isotopes with long half‑lives. Shielding workers and the public requires thick concrete and steel containment structures. A core meltdown, though very rare, could release radioactive material into the environment, as happened at Chernobyl and Fukushima. Spent fuel rods must be stored safely for thousands of years, and the decommissioning of old reactors is expensive and technically challenging.
然而，危害也十分显著。反应堆堆芯具有极强的放射性，产生一系列半衰期较长的同位素。保护工作人员和公众需要厚实的混凝土和钢制安全壳结构。堆芯熔毁虽然极为罕见，但可能向环境释放放射性物质，切尔诺贝利和福岛事故就是例证。乏燃料棒必须安全存放数千年，旧反应堆的退役既昂贵又具有技术挑战。
11. Contamination versus Irradiation – A Crucial Distinction | 污染与照射——关键区别
It is vital to understand the difference between contamination and irradiation, as they require very different safety responses. Irradiation occurs when an object or person is exposed to radiation from an external source. The person does not become radioactive. As soon as you move away from the source or shield it, the exposure stops. Irradiation can cause damage while it happens, but it does not leave lingering radioactivity in the exposed body.
理解污染与照射的区别至关重要，因为两者所需的安全应对措施截然不同。照射是指物体或人暴露于外部源的辐射中。被照射的人不会变得具有放射性。只要远离放射源或加设屏蔽，照射就会停止。照射发生时可能造成伤害，但不会在被照射体内留下残留放射性。
Contamination occurs when radioactive material is deposited on or inside an object or body. The contaminating atoms continue to emit radiation until they decay, potentially causing prolonged harm. A contaminated person must be decontaminated by removing clothing and washing thoroughly, and the contaminated area must be sealed off to prevent spread. Contamination is particularly dangerous with alpha emitters, which are highly damaging if ingested or inhaled.
污染是指放射性物质附着在物体表面或进入体内。这些污染性原子会持续发射辐射直至衰变完毕，可能造成长期伤害。被污染的人员必须通过脱去衣物和彻底清洗来去污，污染区域必须封锁以防止扩散。α发射体的污染尤其危险，一旦摄入或吸入就会造成高度损害。
12. Evaluating Risks and Benefits | 权衡风险与收益
Every application of ionising radiation involves balancing risk against benefit. In medicine, the small risk of developing cancer from an X‑ray or CT scan is justified if it leads to an accurate diagnosis and effective treatment. In nuclear power, the catastrophic potential of an accident must be weighed against the large‑scale, continuous low‑carbon energy supply. Understanding the science empowers us to make informed decisions and to place necessary safety measures correctly. The key is to use radiation wisely, with minimised dose and maximised control.
每种电离辐射的应用都涉及风险与收益的平衡。在医学领域，如果一次X光或CT扫描能带来准确诊断和有效治疗，那么因辐射而罹患癌症的微小风险就是值得承担的。在核能方面，事故的灾难性可能性必须与大规模、持续的低碳能源供应相权衡。理解科学能让我们做出明智的决策，并合理制定必要的安全措施。关键在于明智地使用辐射，做到剂量最小化、控制最大化。
Published by TutorHao | IGCSE Edexcel Science (Physics) Revision Series | aleveler.com
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