Cobalt-60

People make a special metal in big machines.

This metal sends out strong rays. These rays can kill germs on tools. They help doctors treat sick people too.

This metal is very strong. It can pass through many things. It can even go through thick steel. Because it is so strong, it can be dangerous.

We must keep it in safe boxes. If it gets into metal scraps, it can be bad. People must be very careful with it. It is a very useful tool.

Cobalt-60 is a man-made metal.

It is not found in nature in large amounts. People make it in nuclear reactors. They do this by hitting regular cobalt with neutrons. A neutron is a tiny part of an atom. This process turns the metal into a radioactive version.

This metal is very useful. It sends out gamma rays. These rays are strong beams of power. They can pass through many things. They can even go through thick steel.

Because these rays are so strong, they can kill germs. This helps clean medical tools. Doctors also use these rays to treat sick people.

But we must be careful. Cobalt-60 can be very dangerous to humans. It can cause sickness or even death. If it gets into scrap metal, it can hurt many people. This has happened in the past. Sometimes, people found it in steel used for buildings. It has even been found in pet bowls. We must keep this metal in safe, thick boxes to stay safe.

Cobalt-60 is a special kind of metal. It is a man-made version of cobalt. This version is radioactive, which means it sends out energy. Scientists call this a synthetic isotope. It is very useful because it sends out strong gamma rays. These rays can pass through many different things.

This makes it a very important tool in many jobs. It helps us do things that regular metal cannot do.

Making cobalt-60 is a step-by-step way of working. It starts with regular cobalt. Scientists put this cobalt inside a nuclear reactor. Inside the reactor, they hit the cobalt with neutrons. A neutron is a tiny part of an atom. This process is called neutron activation. It changes the cobalt into cobalt-60.

After it is made, the cobalt undergoes beta decay. This means it turns into nickel-60. During this change, it releases two gamma rays. These rays carry a lot of energy.

People have studied this metal for a long time. In 1957, a scientist named Chien-Shiung Wu did a famous test. She used cobalt-60 to study how atoms behave. Her team cooled the cobalt to very low temperatures. They used a magnetic field to line up the atoms. She discovered that the rays came out in a specific way. This discovery showed that nature has a sense of handedness. This was a huge moment for science.

There are many facts about how cobalt-60 works. It has a half-life of about 5.27 years. This is how long it takes for half of it to decay. One gram of this metal has a lot of activity. It can produce 26 watts of energy per gram.

This energy is much higher than some other metals. Because the rays are so strong, they can go through thick steel. It takes about 2.1 centimeters of steel to stop the rays. It takes about 4.0 centimeters of lead to stop them.

We see the effects of cobalt-60 in many places. Doctors use it in machines to treat sick people. It is also used to clean medical tools by killing germs. Some factories use it to check if metal is thick enough. It can even be used to clean food. However, we must be very careful with it. Sometimes, it has accidentally ended up in scrap metal. This happened in Taiwan with apartment buildings. It even happened with pet food bowls in the United States.

We must always keep it in safe, thick boxes.

Cobalt-60 is a synthetic radioactive isotope of cobalt. It is not found naturally on Earth in significant amounts. Instead, it is created by humans through a process called neutron activation. This means scientists bombard a target of natural cobalt with neutrons inside a nuclear reactor. This process changes the stable cobalt atoms into the radioactive cobalt-60 isotope.

This material is highly valued because it is a high-intensity gamma-ray emitter. It also has a relatively long half-life of 5.2714 years. This duration allows it to be a steady and reliable source of energy for many different tasks.

The way cobalt-60 decays is a specific, two-step process. First, the cobalt-60 undergoes beta decay. During this stage, it transforms into an excited state of the stable isotope nickel-60. This transition releases a beta particle, which is an electron.

Second, this excited nickel-60 quickly settles into a stable state. As it does this, it emits two distinct gamma rays. These gamma rays have specific energies of 1.17 MeV and 1.33 MeV. Because these gamma rays are highly penetrating, they can pass through many materials that would stop other types of radiation.

Because of these properties, cobalt-60 is used in many specialized ways. In medicine, it is used for radiotherapy to treat patients through cobalt therapy machines. It is also used to sterilize medical equipment by killing germs with radiation. Over 40% of all single-use medical devices are sterilized using cobalt-60. In industry, it serves as a source for industrial radiography and thickness gauges. It can even be used for pest insect sterilization and food irradiation.

Its ability to penetrate materials makes it a perfect tool for checking the thickness of goods or inspecting metal.

History shows us how much we have learned from this isotope. In 1957, a scientist named Chien-Shiung Wu conducted a landmark experiment. Her team cooled cobalt-60 to very low temperatures and used a magnetic field to align the nuclei. She observed that the beta rays were emitted more in one direction than the other. This discovery proved that beta decay violates parity. This meant that the laws of nature, specifically the weak force, recognize a sense of "handedness" in the universe.

The energy released by cobalt-60 is quite significant. One gram of the material has a decay energy of about 26 watts. This is approximately 40 times larger by mass than the decay energy of plutonium. The radiation is also very strong. For example, 60 micrograms of cobalt-60 can generate a dose of 1 mSv at a distance of one meter within just one hour.

Because the rays are so powerful, they require heavy shielding. It takes about 2.1 centimeters of steel or 4.0 centimeters of lead to block the radiation.

While useful, cobalt-60 can be very dangerous if not handled correctly. If it enters a living mammal, the body takes it up into tissues like the liver, kidneys, and bones. This can lead to cancer over time. There have been several accidents involving contaminated steel. In Taiwan, 1,700 apartments were built with steel contaminated by cobalt-60, affecting about 10,000 people. In 2012, Petco had to recall steel pet food bowls because they contained low levels of radiation.

These incidents usually happen when cobalt is accidentally mixed into scrap metal during recycling.

Today, the production of cobalt-60 is a global industry. Argentina, Canada, India, and Russia are the largest suppliers. Heavy-water reactors, such as the CANDU reactors used in Canada and India, are especially good for making it. These reactors allow for "online refueling," meaning targets can be added or removed without shutting the reactor down. This makes the production process efficient and continuous. As more reactors are built, the capacity to produce this important isotope continues to grow.