Strontium isotope half-life

Strontium can also exist as several radioactive isotopes, the most common is °Sr. Strontium-90 is formed in nuclear reactors or during the explosion of nuclear weapons. Radioactive strontium generates beta particles as they decay. One of the radioactive properties of strontium is half-life, or the time it takes for half of the isotope to give off its radiation. 

Because normal radioisotopic decay lowers the thermal output by about 2.5%/yr in these units, they are purposefully overdesigned for beginning of life conditions. Several of these generators have successfully operated for as long as 28 years. This is approximately equal to the half-life of the strontium-90 isotope used in the heat sources. The original SNAP-7 series immobilized the strontium-90 as the titanate, but the more recent ones have used it in the form of the fluoride, which is also very stable. A number of tiny nuclear-powered cardiac pacemaker batteries were developed, which have electrical power outputs of 33—600 p.W and have been proven in use (17). 

The half-lives of some radioisotopes are measured in billions of years for others, the half-life is measured in fractions of seconds. Following are some examples of the half-lives of a few isotopes uranium-238 = 4.6 billion years carbon-14 = 5730 years strontium-90 = 38 years phosphorus-32 = 14.3 days radon-222 = 3.8 days uranium-239 = 23.5 minutes. 

In the rubidium-strontium age dating method, radioactive 87Rb isotope with a natural isotope abundance of 27.85 % and a half-life of 4.8 x 1010 a is fundamental to the 3 decay to the isobar 87 Sr. The equation for the Rb-Sr method can be derived from Equation (8.9) ... 

The isotope strontium-90 is produced during the testing of nuclear weapons. If 100.0 mg of strontium-90 was released in the atmosphere in 1960, how much of the radioisotope remains 85 years later The half life of strontium-90 is 29 years. 

Problem A 2.5 gram sample of an isotope of strontium-90 was formed in a 1960 explosion of an atomic bomb at Johnson Island in the Pacific Test Site. The half-life of strontium-90 is 28 years. In what year will only 0.625 grams of this strontium-90 remain ... 

The two fission-produced radio-strontium isotopes of interest in environmental samples are 90Sr and 89Sr. Sr-90 has a fission yield of 5.8 %, a half-life is 28.78 a, and the radioactive daughter 90Y with a half life of 2.67 d, to which it decays by beta-particle emission. Sr-89 has a fission yield of 4.7%, a half life of 50.52 d, and decays to the stable daughter89 Y. The decay schemes given in Figure 13.1 show that these two radio-strontium isotopes for practical purposes can only be measured by beta-particle counting. 

Strontium-90 is a radioactive isotope that was created by atomic weapons testing during World War II. The half-life of strontium-90 is 28.8 years. The first atomic weapons test took place in New Mexico on July 16,... 

Major concern about rapidly increasing levels of radioactive fallout in the environment and in foods developed as a result of the extensive testing of nuclear weapons by the United States and the Soviet Union in the 1950s. Nuclear fission generates more than 200 radioisotopes of some 60 different elements. Many of these radioisotopes are harmful to humans because they may be incorporated into body tissues. Several of these radioactive isotopes are absorbed efficiently by the organism because they are related chemically to important nutrients for example, strontium-90 is related to calcium and cesium-137 to potassium. These radioactive elements are produced by the following nuclear reactions, in which the half-life is given in parentheses ... 

The isotopic composition of strontium varies with time due to the radioactive j8-decay of Rb to Sr with the very long half-life Tyf) of 48.8 Gyr. The relationship can be expressed as... 

Strontium is a naturally occurring element found in rocks, soil, dust, coal, and oil. Naturally occurring strontium is not radioactive and is referred to as stable strontium. Stable strontium in the environment exists in four stable isotopes, " Sr (read as strontium 84), Sr, Sr, and Sr. Twelve other unstable isotopes are known to exist. Its radioactive isotopes are Sr and °Sr. Strontium is chemically similar to calcium. It was discovered in 1790. The isotope Sr is a highly radioactive poison, and was present in fallout from atmospheric nuclear explosions and is created in nuclear reactors. Atmospheric tests of nuclear weapons in the 1950s resulted in deposits and contaminations. °Sr has a half-life of 28 years and is a high-energy beta emitter. Its common cationic salts are water soluble it forms chelates with compounds such as ethylenediaminetetraacetic acid strontium coordination compounds are not common. Powdered metallic strontium may constitute an explosion hazard when exposed to flame. 

The isotope strontium-90 was introduced into the atmosphere by the atmospheric testing of nuclear weapons. Because of the chemical similarity of strontium to calcium, it now occurs with Ca in measurable quantities in milk, bones, and teeth as a result of its presence in food and water supplies. It is a radionuclide that undergoes beta emission with a half-life of 28 years. It may cause leukemia, bone cancer, and other related disorders. If we begin with a 16-/tg sample of fgSr, 8 /tg will remain after one half-life of 28 years. After 56 years, 4 /tg will remain after 84 years, 2 /ag and so on (Figure 26-6). 

Under natural conditions, neither element has any biological importance. In some cases, however, strontium can be of concern in regards to human health. Strontium is perhaps best known for its radioactive isotope Sr-90, which possesses a half-life of 26 years. Strontium 90 is... 

Strontium isotopes can be used to determine the ages of rocks. Radioactive rubidium 87 decays into strontium 87, with a half-life of 4.9 billion years. Geologists can use the ratio of Sr-87 to naturally occurring... 

Another strontium isotope, Sr-90, is highly radioactive, with a half-life of 29 years. Strontium 90 has been used as a power source in weather stations and buoys. 

Strontium-90 is one of the products of the fission of uranium-235. This strontium isotope is radioactive, with a half-life of 28.1 yr. Calculate how long (in yr) it will take for 1.00 g of the isotope to be reduced to 0.200 g by decay. 

The trace alkali and alkaline earth cations are present in the following amounts lithium, 10-300 mg kg-1 rubidium, 20-500 mg kg-1 beryllium, 0.5-10 mg kg-1 strontium, 600-1000 mg kg-1 barium, 100-3000 mg kg-1 and radium, perhaps 10-7 mg kg-1. Some varieties of fmit trees are sensitive to as little as l mg L-1 Li+ in irrigation water, but Li+ toxicity is rare. Rubidium, cesium, strontium, and barium have all been studied in the laboratory, but have received little attention in the field. Strontium has been studied because its radioactive isotope 90Sr (half-life = 28 years) is produced by nuclear fission and could cause long-term soil contamination after nuclear explosions or accidents. In soils the toxic Be2+ ion behaves more like AI3 1 than like the other alkaline earth cations. 

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