Immersed in a Sea of Radiation

You don’t have to look far to find radiation in the world around us. In fact, the vast majority of radiation that we are exposed to throughout our lives comes from natural sources. Naturally Occurring Radioactive Materials (NORM) are very common in the environment and can be found in many products in our homes and cars. These materials generally pose very little, if any threat to our health, and it may surprise you how many everyday items have radioactive properties.

This rock from southern Utah contains Thorium-232.

The most common NORM contain radioactive isotopes of uranium, thorium, and potassium, as well as the isotopes these decay into (such as radium and radon). Although  much of the earth’s surface contains very low concentrations of radioactive materials, NORM is concentrated in many raw industrial products and activities such as the following:

Coal: although other rocks in the earth’s crust have approximately the same concentration of NORM, the large quantities of coal needed to fuel much of the world’s energy demands are responsible for a sizable amount of radiation and a wide variety of isotopes including potassium, lead, and radium. An interesting fact about NORM in coal is that the naturally occurring uranium contained in coal could be a fuel source more powerful than the coal itself if used in a certain type of nuclear reactor¹. 

Phosphate Rock: mainly used for fertilizers, phosphates can have much more concentrated amounts of NORM than other mining products. The radioactive content of phosphates has attracted media attention after European fertilizer manufacturing had been found responsible for radioactive material in the Atlantic.

Granite: this type of stone has traces of uranium in it, which means that many federal buildings such as the United States Capitol are faintly radioactive. We’ve found that the MiniRad-D (a small radiation detector) reads a constant radiation level of 2 around the perimeter of the Utah State Capitol, which has a granite facing on its exterior. Radiation measurements on granite surfaces can even show comparable levels to those from low-grade uranium mine tailings.

Oil and gas production: most of the radioactive material brought out of the ground in oil and gas production is deposited in pipes and other equipment. The concentration of NORM has made the resale of used equipment more difficult in recent years.

Although industrial activities are responsible for large amounts of NORM, many common household items also have significant amounts of radiation. Here are a few examples:

Smoke detectors: one of the most radioactive items in a home is the smoke detector, which uses an isotope of americium to sense the presence of airborne particles carried by smoke.

A small Americium-241 pellet from a smoke detector is contained in the plastic holder on top of the MiniRad-D device.

Ceramics: some of the most famous antique radioactive items are Fiesta Ware ceramics, which were produced from 1936-1943². The red glaze on these dishes contains Potassium-40, as do  the glazes of other ceramics with red, yellow, green, and black colors. The clay itself used in some ceramics can also contain NORM. Ceramic products such as bathroom tiles and porcelain can also show up on a radiation detector.

Cat litter: the main ingredient of cat litter is clay, which like that used in ceramics, often contains low levels of NORM.

Colored glass: uranium was commonly used as a coloring agent in yellow and green glass produced in the first half of the 20^th century. You can find antique dinnerware, home décor, and even children’s marbles that emit a measurable amount of radiation.

These antique marbles contain trace amounts of uranium.

Glossy paper: Kaolin, a substance known as “white gold” for its versatility and value, was commonly used to create glossy paper on magazines in the early 1900s. Kaolin contains clay with low concentrations of uranium and thorium.

Instrument dials: due to its ability to fluoresce, radium was used in paint for marking instruments and watch dials. This paint exhibits a bright green color when fluorescing.

Spark plugs: dating back to 1940, some old spark plugs contain an isotope of polonium that was used to make a more brittle alloy that readily creates sparks.

Lantern Mantles: old Coleman lantern mantles contain low levels of Thorium-232, an isotope with a 14 billion year half-life. Special care should be used when dealing with used mantles to ensure the radioactive dust isn’t breathed in.

A Coleman lantern mantle with a MiniRad-D detector.

Food: many foods contain trace amounts of radiation, including potatoes, bananas, kidney beans, and Brazil nuts. Salt substitute, which contains potassium chloride instead of sodium chloride, may also have a low level of radiation due to the presence of Potassium-40.

1) http://www.world-nuclear.org/info/inf30.html

2) http://www.orau.org/ptp/collection/consumer%20products/consumer.htm

D-tect Systems is supplier of advanced radiation and chemical detection equipment sold around the world. www.dtectsystems.com.

Isotope Identification: How Does it Work?

Although we can’t feel, see, or hear it, we live in a sea of radiation. Cosmic rays from outer space continually bombard our planet, natural radioactive materials produce a steady stream of radiation, and many man-made materials constantly emit radiation in our homes and vehicles. Although much of this radiation is weak and harmless, there are some sources, as well as elevated radiation levels, that are best avoided. This is the reason that isotope identification is so important.

The term isotope is often misunderstood: not all isotopes emit radiation. Rather,  the term isotope has to do with the number of neutrons in the nucleus of an atom. Each element is defined by a set number of protons (or atomic number), by which it is listed on the Periodic Table. Iodine, for example, has 53 protons. But there are different versions or isotopes of iodine with varying numbers of neutrons, which are denoted in the isotope name. I-127 is the most common isotope of Iodine and is stable, meaning that its atoms don’t give off radiation or change to other isotopes.  But I-129 and I-131, which are produced in nuclear processes, are unstable and give off radiation that can be dangerous.

Isotope identification consists of finding out which radioactive isotopes are responsible for radiation. It is possible to figure this out by closely measuring the energy levels of radiation. Each radioactive particle or photon has a certain energy level, and each radioactive isotope emits a different set of energy levels. For example, here is a radiation measurement taken by a Rad-ID device:

Isotope Identification from the Rad-ID

As you can see, there are two energy peaks (at 25 keV and 88 keV) shown on the graph.  These two peaks appear because the isotope gives off a higher percentage of 25 keV and 88 keV radiation than radiation at other levels. By matching these measured energy peaks to pre-programmed energy peaks for known radioactive isotopes, isotope identifiers can narrow down and found out which isotopes are emitting the radiation.

There are a few difficulties that occur in the isotope identification process. First, no matter how well a radiation reading matches the pre-programmed energy levels, there is always at least a slight chance of an incorrect identification. This probability grows dramatically if the measured radiation levels can’t be matched very well. This is why it’s important to understand how good the match is and if there are lots of isotopes involved. Confidence bars can help out with this. Another problem is shielding. These two pictures show measurements an unshielded source on the left and a shielded source on the right:  

If you look closely at the two pictures you'll notice that a large energy peak on the left side of the first  (unshielded) reading is missing in the second. This  happens because shielding tends to block high-energy photons much better than the low-energy ones, which penetrate better. This can drastically change the shape of radiation measurements, and with enough shielding, completely block the radiation.

Measuring energy levels precisely enough to make an identification takes a very specialized instrument, different than a normal radiation detector. Identifiers usually have a LaBr3 or CZT detector, as does the Rad-ID.  These detectors are much more accurate than other types of radiation detectors. The Rad-ID also uses a large scintillation detector (NaI(Tl)), a Geiger-Mueller detector and an optional He3 tube to find a wide range of gamma and neutron radiation. In fact, the Rad-ID can identify 107 different radioactive isotopes, even if a measure sample is reading radiation from several isotopes.

With a good isotope identifier, you can be sure that you know what isotopes are in the environment and if you need to worry about them.

D-tect Systems is supplier of advanced radiation and chemical detection equipment sold around the world. www.dtectsystems.com.

Radiation Challenges Continue in Fukushima

Even though media coverage of the Japanese nuclear crisis has decline rapidly following the first few weeks of the disaster, there is still a steady stream of cleanup updates and survivor stories hitting international media outlets. Many of these have to do with the residents of the Fukushima Prefecture, whose proximity to the stricken nuclear complex has made life extremely difficult. Changing government regulations, delayed cleanup efforts, and a lack of scientific understanding of the whole situation has added to the chaos of the situation.

A common theme in many of these recent stories is the risk of radiation exposure to children living in or near the prefecture. Although the 20 kilometer evacuation zone set by the Japanese government has helped limit the radiation exposure to many people, there is no guarantee of safety even outside this radius. The problem is that radiation given off by the nuclear plant is extremely hard to track: wind- and water-borne radioactive particles have settled in unpredictable hotpots across the prefecture. This is a major concern for the more than 300,000 residents living in Fukushima city, parts of which lie inside the evacuation zone.

A local Japanese man checking the exterior of a church with the MiniRad-D.

A recent article by the International Herald Tribune reports that more than 70 elementary and secondary schools are located within the city where radiation levels have been measured above the safe dose level for nuclear plant workers – which is much higher than what is safe for children. Many of these schools have no way to monitor changing radiation levels and have received no help from the government to decontaminate school grounds. This has many parents worried and angry at the Japanese government, and a few have already taken the problem into their own hands. One day care center measured a drop in radiation levels from 30 times to two times the background level after volunteers scraped off the top layer of dirt on the playground. Efforts are underway at other schools to remove contaminated soil and plants from school property.

A MiniRad-D showing the radiation reading in a Japanese courtyard.

We are also committed to help out these children. In two separate trips to Japan since the crisis began, we’ve been able to see for ourselves what the situation is like. Members of our team have been working with charitable organizations to scan schools and churches for radiation and we’ve donated ten MiniRad-D units (pager-sized radiation detectors) to help school district officials determine safe and unsafe levels of radiation so parents feel comfortable about sending kids to school. These units are also used to help churches determine radiation levels at their buildings. Check out this post for details of the first trip.

Although the media coverage has mostly moved on to newer stories, the Japanese nuclear crisis is far from over. A tremendous amount of work remains before the Japanese confidence, economy, and environment completely stabilizes. 

 

D-tect Systems is supplier of advanced radiation and chemical detection equipment sold around the world. www.dtectsystems.com.