[OPINION] What you should know about radioactivity

The following is the 22nd in a series of excerpts from Kelvin Rodolfo’s ongoing book project “Tilting at the Monster of Morong: Forays Against the Bataan Nuclear Power Plant and Global Nuclear Energy.“

Here, we look at radioactivity and its forms, because if the Bataan Nuclear Power Plant is activated, they will become serious realities in our environment. Thankfully, we have to deal with only three forms of radiation: alpha, beta, and gamma. The arithmetic of decay is even simpler, because it involves only alpha and beta radiation.

Alpha radiation

Let’s illustrate alpha and beta radiation by looking at the first two things that happen when Uranium 238 decays, because it is abundant in uranium-mining and reactor wastes.

Our last foray taught that atomic nuclei, which have only positive charges from their protons, are kept from flying apart by the presence of neutrons. A “Strong Nuclear Force,” 137 times stronger than electromagnetic force but operating only at very close range, bonds the protons and neutrons together.

Some atoms with big nuclei like Uranium 238 are unstable because they have too many protons and too few neutrons to hold them together. They decay by emitting what were named alpha particles when newly discovered but not yet understood. Alpha particles turned out to be whole chunks thrown off the nucleus, each composed of two protons and two neutrons.

An alpha particle is identical to the nucleus of Element #2, Helium. Shortly after an alpha particle emerges from a decaying atom it picks up two electrons from its surroundings and becomes an ordinary atom of helium, a chemically inert and harmless gas.

Hitting you from outside, alpha radiation is harmless, easily stopped by the outer layers of your skin. However, breathing or swallowing radioactive substances that emit alphas inside you can be dangerous, especially if the altered atom is still radioactive.

Beta radiation

After emitting an alpha particle, the “daughter” atom left by its decayed “parent” nucleus now has two fewer protons. Therefore, its atomic number drops by two, and it has become a different element. A decayed U238 atom (Element 92) has become a Thorium atom (Element 90). Having also lost two neutrons, its weight was reduced by four, and so the daughter is the isotope Th234.

But Thorium 234 is also radioactive! Just because a nucleus decays doesn’t mean that the daughter nucleus is stable and won’t decay as well.

Our new Th234 nucleus is also unstable because it now has the opposite problem that U238 had: too few protons and too many neutrons. It decays when one of its neutrons emits a beta particle, now recognized as a high-speed electron, leaving behind a proton, as shown in the picture. The daughter nucleus, now having one more proton, rises in atomic number to 91, Element Protactinium. The lost beta particle didn’t weigh anything, and so the atomic weight remains 234.

Tritium

We already met beta radiation briefly, as we ended our last foray by learning about Tritium, the radioactive isotope of Hydrogen. Tritium is three times heavier than common hydrogen because its nucleus has two neutrons in addition to its one proton. The neutrons outnumber the protons so strongly, it is no wonder that tritium is intensely beta-radioactive.

After Chernobyl and Fukushima, people worry about radiation from a reactor accident. But even while operating normally, nuclear power plants abundantly generate and pollute their surroundings with tritium.

Even though tritium is three times heavier than normal hydrogen, it behaves chemically the same way, and so it can substitute for hydrogen in water and food. If tritium becomes part of your living cells, and then emits beta particles, you can get cancer.

A later foray will closely examine the health hazards posed by normal nuclear-power plant operation. The incidence of bladder cancer in adults living near French NPPs is significantly enhanced. Similarly, Korean research blamed NPPs for higher incidences of thyroid and breast cancers in adults.

Most importantly, many medical studies in the United States, Europe, and Asia have revealed that children are especially vulnerable to be stricken with solid cancers, and especially leukemia. To someone like me who lost a young child to cancer, this is one of the most important reasons for not activating BNPP.

Carbon 14

Another important example of beta decay is that of Carbon 14, so useful for dating rocks and archeologic relics. Carbon 12, the overwhelmingly most abundant isotope of carbon, is very stable and never decays because its six protons are comfortably matched by six neutrons. Carbon 14 atoms, much rarer, have two more neutrons and decay by beta emission, becoming atoms of Nitrogen, Element 7. The older a rock or wooden artifact is, the less C14 remains in it, and so its reduced abundance relative to that of C12 measures its age.

Gamma radiation

After a decay, the “daughter” nucleus can be left excited with some extra energy that it has to relieve. It does so by emitting a gamma ray, a high-energy light particle. It has neither mass nor electric charge, so neither the atomic number nor atomic weight of the nucleus changes.

Gamma- and X-rays made by modern machines are identical forms of high-frequency radiation. They are very energetic and dislodge electrons from atoms and molecules, ionizing them. Those new ions are unstable and quickly undergo chemical changes. In a fraction of a second, a gamma ray passing through a living body can change the DNA of cells. Prolonged exposure to gamma radiation can lead to cancer.

Marie and Pierre Curie won the Nobel prize in 1898 by discovering Element #88 that Marie named Radium. She also coined the term “radiation.” Very soon after it was discovered, radium was put to good use for medical purposes. Marie did most of the labor in isolating the radium, and prolonged exposure to gamma radiation eventually destroyed her blood and killed her.

When Radium 226 decays it produces another toxic substance, radioactive Radon 222 gas, a major environmental and health concern. If you inhale radon that decays before you exhale, its solid daughter Polonium 218 will remain lodged in your lungs. Only after rapidly undergoing two more alpha and two more beta emissions does the decaying atom finally become a stable metallic atom of Lead. These emissions and accompanying gamma rays damage cells and cause lung cancer. Radon can also come from radium entering the body with food and drink.

In the continental United States, which is deeply underlain by very ancient rocks containing uranium, radon leaking up into homes is a lung carcinogen, second only to cigarette smoking. Perhaps it is just as well the Philippines are much younger islands without ancient, uranium-rich bedrock, huh?

U238 and Thorium 230 are the most abundant radioactive elements that uranium mining leaves in its waste heaps and ponds. Our next foray will look at how they decay, and the environmental and health hazards they pose in those real-world settings.

We will look in more detail at the complicated series of decays that transforms Uranium 238, by far that element’s most abundant isotope, into common Lead 206 metal. Using Thorium 230 as our example, we will familiarize ourselves with the strange but exceedingly important idea of a radioactive element’s half-life.

Later, we will also examine the environmental threat of the radioactive waste that BNPP would accumulate, with no way to store permanently out of harm’s way. – Rappler.com

Born in Manila and educated at UP Diliman and the University of Southern California, Dr. Kelvin Rodolfo taught geology and environmental science at the University of Illinois at Chicago since 1966. He specialized in Philippine natural hazards since the 1980s.

Keep posted on Rappler for the next installment of Rodolfo’s series.

[OPINION] What you should know about radioactivity

Alpha radiation

Beta radiation

Tritium

Carbon 14

Gamma radiation

Previous pieces from Tilting at the Monster of Morong:

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