The Basic Information
Uranium is a natural and primordial element which has existed before the birth of our planet! Uranium 238 is the most common form of uranium, having 92 protons and 146 neutrons. Uranium 238 in nature is always found in equilibrium with it’s counterparts uranium 235 and uranium 234. Uranium is a type of element known as an actinide as well as being electrically conductive. Uranium is a metal which readily oxidizes providing many useful properties to humans, such as its long time use as a colorant. The earliest known use of uranium oxides as colorants date from the early first century.
Color: Silver (other colors when oxidized)
Special properties: Radioactive, florescent, super dense, and pyrophoric.
Note: Unless otherwise stated, all facts concern uranium 238, the most stable isotope of uranium.
Atomic Number: 92
Atomic Weight: 238.02891
Density: 19.05 grams per cubic centimeter (Compared to lead: 11.34 grams per cubic centimeter)
Mohs Hardness: 6
Specific Radioactivity: 12.44 kBq/g
Uranium and Humans
Natural uranium has existed long before humans walked the earth. Humans have ingested and inhaled uranium and uranium progeny for their entire existence. It may very well be possible that some of the very mutations which helped give rise to our very species may have started as a simple uranium decay induced DNA mutation. Though this may be a little far fetched, it is a true fact that the average human ingests about 474.5 µg (1 µg = 1 micro gram = 0.000001 grams) of natural uranium per year (Depleted Uranium, IAEA). Thought uranium is present in our bodies in tiny amounts and is extremely common in our foods and soil, the dangers of uranium cannot be taken lightly. Uranium is radioactive in all forms and very dangerous if inhaled or ingested, other than the extremely microscopy amounts humans naturally intake. Uranium is a heavy metal and builds up in the kidneys, taking years to leave the body in such cases. The use of depleted uranium, uranium mining, and nuclear accidents have increased the amounts uranium exposure to some groups of people. In these “contaminated areas” rates of cancer and genetic mutations have been observed.
Uranium has long been sought for the special atomic characteristics of one of its isotopes, uranium 235. Uranium 235 is capable of accepting a single slow or “thermal” neutron and becoming uranium 236. Almost instantly, the ultra-unstable uranium 236 begins to gyrate and oscillate, quickly breaking into two smaller atoms. Normally this break is asymmetric, which means that one atom is larger than the other. The two most common mass numbers for these new child atoms, called fission fragments, are centered around 90-100 and 130-140. For this reason, strontium 90, technetium 99, molybdenum 99 and cesium 134, 133, and 137 are some of the most common fissile fragments. These fission fragments are release as well as thermal energy, which can be used to generate electrical power. Additionally, more neutrons are created which may go one to induce additional atomic fissions. The occurrence of uranium 235 in nature is very small by comparison to uranium 238. To illustrate this, imagine a box with 1,000 marbles. If each marble represented a single uranium atom found in natural uranium, about 992 of them would be uranium 238, while a mere 7 marbles would represent uranium 235. The other natural isotope of uranium, uranium 234, would amount to less than a single marble.
Scientists change the ratio of uranium 235 to 238 using various methods known as enrichment. Uranium with a amount of uranium 235 than occurs naturally is said to be “enriched” whilst uranium with a lower than normal amount of uranium 235 than occurs naturally is said to be “depleted”. Typical nuclear reactor fuel-grade uranium has an enrichment of between 3-5% (meaning 3 to 5 percent of the uranium is isotope 235, while the rest is mostly uranium 238). Weapons grade uranium, that which may be used to create a nuclear weapon, is typically enriched to 80% or greater (often greater than 90%).
Uranium has been used for millinea as a colorant, but it was not until the early twentieth century that its use as a large scale commercial material came into age. Uranium was a very popular colorant in brightly colored products, such as the famous “Radioactive Red” Fiesta® Ware dishware of the 1930’s though 1970’s. The bright red-orange color was made using uranium oxide as a colorant. Sometimes natural uranium was used, but often depleted uranium was due to the need of major governments to obtain uranium’s fissile isotope, uranium 235, leaving the depleted uranium.
Glassware was also a typical favorite of uranium colorant. Of this glassware, perhaps none was more promanant and arguably beautiful as that of the American Economic Depression Era glassware, known as “Depression Glass”. To this day, large amounts of this uranium colored glassware are available at American antique shops. This author has estimated that the average antique shop contains as much as 180 grams (6.3 Oz) of uranium locked away in the beautiful glassware they sell. But this is a mere estimation based on a limited survey for a dozen or so antique shops.
“I have read that glazes for (this is a touch anecdotal) ceramics, like Fiesta® Ware contained about 10-12% uranium by mass, while depression glassware contains about 2%. If I suppose that a normal antique shop has about five pieces of Fiesta® Ware at 50g’s of glaze each and 50 pieces of depression glassware at about 150grams each… we would get:
5pieces (50g)0.12 + 50 pieces(150g)0.02 = 180g of uranium =) That’s 6.3 ounces… “
Uranium and it’s progeny are also found in many other consumer products, from kitty litter to toilet seats. Below is a list of consumer products known to either contain now, or in the past, uranium or uranium progeny:
- Bath Tubes
- Bathroom Tiles
- Dishes and Plates
- False Teeth
- Granite Counter Tops
- Kitty Litter
- Rock Collections
- Toilet Seats
- Vacuum Tubes
Radium 226(An element which comes from uranium)
- Old Glowing Paint
- Water Jugs
- Brazil Nuts
- Gauges & Dials
Uranium – The Naturally Occurring Radioactive Material
Many Natural Occurring Radioactive Materials, often referred to as NORM, exist in our environment. These naturally radioactive materials are either primordial (they have existed since before the Earth) or are created from natural sources. The two major natural sources for the creation of natural radioactive material are as a result of decay from primordial elements, or as a result of high energy cosmic rays, from space, interacting with our atmosphere. Uranium 238 and Thorium 232 are primordial elements, meaning that they were created before the Earth. Each of these elements creates a long decay series with many members. Much of the Earth is covered with trace amounts of these long-lived isotopes and their progeny. Radon, a nasty gas which may exist in basements and low lying ground, actually comes from the decay of uranium 238 and is responsible for the radioactivity detected in freshly fallen rain, though this radioactivity quickly becomes undetectable. Below is the uranium 238 decay series. Some decays can actually have more than one possible resulting isotope, but only the most common have been listed below.
Natural Uranium – The Uranium 238 Decay Series
Element Half-life Decay Mode Relevant Gamma Energies (*)
|Isotope||Half-life||Decay||Common Gamma energies (I%)|
|Uranium 238||4.5 Billion Years||Alpha||13 keV (0.08)|
|Thorium 234||24 Days||Beta||63.29 keV (0.048), 92.8 keV (0.028)|
|Protactinium 234m||1.2 Minutes||Beta||1,001.03 keV (0.00837)|
|Uranium 234||240,000 Years||Alpha||13 keV (0.109)|
|Thorium 230||77,000 Years||Alpha||12.3 keV (0.085)|
|Radium 226||1,600 Years||Alpha||186.1 keV (0.035)|
|Radon 222||1.8 Days||Alpha||510 keV (0.000760)|
|Polonium 218||3.1 Minutes||Alpha||None|
|Lead 214||27 Minutes||Beta||351.92 keV (0.358), 295.21 keV (0.185)|
|Bismuth 214||20 Minutes||Beta||609 keV (0.448), 1764.49 keV (0.1536)|
|Polonium 214||160 Micro Seconds||Alpha||799.7 keV (0.000104)|
|Lead 210||22 Years||Beta||10.8 keV (0.25)|
|Bismuth 210||5 Days||Beta||None|
|Polonium 210||140 Days||Alpha||None|
Some rare possible decays omitted and some simplification provided for ease of understanding and brevity.
* Gamma energies provided for only the most abundant gamma energies. Many more may exist, but are not included for brevity. Energies are provided in thousands of electron volts (keV) and are accompanied by their percentage of emission. E.g, 100 keV (0.80) means that a 100 thousand electron volt gamma is emitted for approximately 80% of the decays of this isotope.
Radiation and Uranium are amazing and powerful.
Like many of natures most powerful creations, Uranium is dangerous and must be treated with respect. Never expose children, pets, or your bare hands to Uranium. If you should ever touch a Uranium sample, always wash your hands carefully. Remember, distance, time, and shielding, and hand washing are your friends
Depleted Uranium, IAEA. Accessed online June 1, 2012 at http://www.iaea.org/newscenter/features/du/du_qaa.shtml