Fukushima Update: Why We Should (Still) Be Worried
What Radiation Is
A great help to nuclear proponents is the fact that nuclear physics is complicated, and most people don’t understand even its most basic concepts. The blanket term “radiation” is used to describe all manner of radioactive contamination—as if it’s just one thing—when, in fact, there are different kinds, some much more damaging than others. It also matters exactly what is being exposed to radiation—i.e., exposure outside the body or inside it—and how long the exposure goes on.
In a nutshell, radioactive elements, also known as radioisotopes or radionuclides, are unstable atoms. They seek stability by giving off particles and energy—ionizing radiation—until the radioisotope becomes stable. This process occurs within the nucleus of the radioisotope, and the shedding of these particles and energy is commonly referred to as ‘‘nuclear disintegration.’’ Nuclear radiation expert Rosalie Bertell describes the release of energy in each disintegration as ‘‘ an explosion on the microscopic level .”
This process is known as the “decay chain,” and during their decay, most radioactive elements morph into yet other radioactive elements on their journey to becoming lighter, stable atoms at the end of the chain. Some of the morphed-into elements are much more dangerous than the original radioisotope, and the decay chain can take a very long time. This is the reason that radioactive contamination can last so long.
To further complicate the issue, different radioisotopes give off different kinds of radiation—alpha, beta, gamma, X ray, or neutron emissions—all of which behave differently. Alpha emitters, such as plutonium and radon, are intensely ionizing but don’t penetrate very far and generally can’t get through the dead layers of cells covering skin. But when they are inhaled from the air or ingested from radiation-contaminated food or water, they emit high-energy particles that can do serious damage to the cells of sensitive internal soft tissues and organs. The lighter, faster-moving beta particles can penetrate far more deeply than alpha particles, though sheets of metal and heavy clothing can block them. Beta particles are also very dangerous when inhaled or ingested. Strontium-90 and tritium, a radioactive form of hydrogen, are both beta emitters. Gamma radiation is a form of electromagnetic energy like X rays, and it passes through clothing and skin straight into the body. A one-inch shield of either lead or iron, or eight inches of concrete are needed to stop gamma rays, examples of which include cobalt-60 and cesium-137—one of the radionuclides of most concern in the Fukushima fallout. Aside from use in medical diagnostics, X rays are also produced in nuclear fission, and their effects are similar to gamma radiation. Neutron emissions are the most penetrating of all types of radiation and require a shield of several feet of water or concrete to contain them.
The behavior of radioisotopes out in the environment also varies depending on what they encounter. They can combine with one another or with stable chemicals to form molecules that may or may not dissolve in water. They can combine with solids, liquids, or gases at ordinary temperature and pressure. They may be able to enter into biochemical reactions, or they may be biologically inert.
In her book No Immediate Danger: Prognosis for a Radioactive Earth,Bertell notes that if they enter the body either through air, food, water, or an open wound, “They may remain near the place of entry into the body or travel in the bloodstream or lymph fluid. They can be incorporated into the tissue or bone. They may remain in the body for minutes or hours or a lifetime.” To illustrate how different radioisotopes behave, she points out that: “Plutonium is biologically and chemically attracted to bone as is the naturally occurring radioactive chemical radium. However, plutonium clumps on the surface of bone, delivering a concentrated dose of alpha radiation to surrounding cells, whereas radium diffuses homogeneously in bone and thus has a lesser localized cell damage effect. This makes plutonium, because of the concentration, much more biologically toxic than a comparable amount of radium.”