Radiation poisoning is a rather general term that covers a lot of different kinds of harmful effects of human exposure to radioactive particles. There are hundreds of different radioactive atomic nuclei, which work in a variety of ways to cause illness or death.
Origin of Radiation
The nucleus of an atom is like an unruly crew on a ship that's been at sea too long. A mutiny can occur at any time. An unstable nucleus can spontaneously eject some of its residents, as the crew might throw the captain of the ship overboard.
Some nuclei are more ship-shape than others. Each atom has a known time frame within which breakdowns occur. This time frame is characterized by the half-life, the time it takes for half of a given number of atoms to spontaneously jettison some cargo.
The cause of the problem is that the nucleus contains a number of protons (called the atomic number), which are positively charged, and thus repel each other. At the same time there is a force, called the 'strong' force, that keeps the nucleus together. The nucleus also includes neutrons---neutral particles whose number is generally somewhat greater than the number of protons. The number of protons plus neutrons in the nucleus is called the mass number. An element is identified by its atomic number, but each element can have many 'isotopes,' forms of the element with different mass numbers (and thus different numbers of neutrons).
As long as an atom is small, meaning it has relatively few protons and neutrons, it is compact. The strong force is truly strong at very short distances, and easily overcomes the repulsive force of the protons. But at some point the gathered neutrons and protons get farther and farther from the center of the atom, and the strong force begins to weaken at these distances. When you get to atomic number 92, the forces are almost equal. Atomic number 92 is uranium.
Splitting the Atom
Th barely-stable uranium atom can, under the right conditions, be split into 2 roughly equal pieces. When this happens, a large amount of energy is released. If the products of fissioning uranium were stable, we could produce nuclear power with no risk. But they are not. The uranium atom splits in various ways, producing hundreds of different radioactive isotopes.
Types of Radiation
Radiation is a form of mass or energy. A radioactive atom can emit a particle, normally an electron, a proton, a neutron, or an alpha particle (2 protons and 2 neutrons). Or it can emit an electromagnetic wave, frequently a very energetic gamma ray. Any of these forms of mass-energy can collide with a molecule in the human body and cause harm.
The various radiation products can interact with cells in the human body by breaking chemical bonds or ripping off electrons. If the radiation is delivered in a large dose, as after an atomic bomb explosion, the energy of the radiation simply overwhelms the body and the victim dies from massive failure of many organs. If the dose is less than lethal, the body can recover through normal repair mechanisms.
For low doses of radiation such as those caused by emissions from nuclear power plants, the danger is in the long-lasting effects of the radioactive element. Long-lasting effects have 2 causes: the body tends to accumulate the radioactive particles in a sensitive part of the body; or the particles are themselves long-lasting and can be picked up from the environment at a later time.
The 3 Most Harmful Products of Power Plants
At the top of the list of harmful radioactive substances produced in nuclear power plants is Strontium-90 (sr-90). This element has much in common with calcium, and tends to accumulate in bones, where it can cause bone cancer. Since the half-life of strontium-90 is 29 years, it can linger in the environment long after its emission from a source. And once it gets into bone, it will remain with the same half-life as in natural surroundings.
Next on the list is Cesium-137 (cs-137). This element mimics potassium and is easily taken up by the body, preferentially in muscle. Cs-137 has a half-life of 30 years, so it can remain in the environment for a long time, but is said to have a biological half-life of only a few months. This is because it tends to be excreted by normal bodily processes. Thus if exposure is stopped, the body will be virtually free of the pathogen in a year or so.
Iodine-131 is a radioactive product of power plants that one hears a lot about. It is considered less dangerous than cs-137 and sr-90 for a number of reasons: first, it accumulates in the thyroid, and cancer of the thyroid, though not pleasant, is not as serious as, for example, bone cancer. Second, there is a preventive technique---iodine pills. Filling the thyroid with stable iodine protects it from the radioactive isotope.
Nuclear power has the capacity to provide inexpensive energy for large numbers of people with virtually no limit to its availability. This benefit to humanity has to be balanced against the lethal qualities of its waste products, which, in the event of an accident, may be released into the environment.
Further reading:
- Risks of Nuclear Power, Bernard L. Cohen, ScD
- The History of Nuclear Energy, Department of Energy
Jon Plotkin - The author was a math major at Cornell and has a master's degree in meteorology from MIT.
