Strontium-90, half-life

Special chemical treatment can isolate the nuchdes of intermediate half-life, ie, cesium-137 and strontium-90 [10098-97-2] Sr, 39 yr (15). These... 

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). 

Half-lives span a very wide range (Table 17.5). Consider strontium-90, for which the half-life is 28 a. This nuclide is present in nuclear fallout, the fine dust that settles from clouds of airborne particles after the explosion of a nuclear bomb, and may also be present in the accidental release of radioactive materials into the air. Because it is chemically very similar to calcium, strontium may accompany that element through the environment and become incorporated into bones once there, it continues to emit radiation for many years. About 10 half-lives (for strontium-90, 280 a) must pass before the activity of a sample has fallen to 1/1000 of its initial value. Iodine-131, which was released in the accidental fire at the Chernobyl nuclear power plant, has a half-life of only 8.05 d, but it accumulates in the thyroid gland. Several cases of thyroid cancer have been linked to iodine-131 exposure from the accident. Plutonium-239 has a half-life of 24 ka (24000 years). Consequently, very long term storage facilities are required for plutonium waste, and land contaminated with plutonium cannot be inhabited again for thousands of years without expensive remediation efforts. 

Sr, as the strontium ion (Sr2+), is used for pain palliation in patients with metastatic bone disease. The strontium ion is a calcium ion mimic, being taken up in metabolically active bone such as cancer. 89Sr is a therapeutic radionuclide with a half-life of 50.53 days, emitting a 1.49 MeV [3 particle on decay. Several recent reviews discuss the use of radionuclides and their complexes as pain palliation agents in metastatic bone disease.18,212-215... 

Original -jj—= 0.700 ( Since the half-life for strontium-86 is very long, we can Sr... 

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. 

Humans are exposed to radiation from the testing and explosion of nuclear weapons and the wastes of nuclear reactors and power plants. Strontium-90 is a fission product from nuclear reactors. It is of particular concern because it has a long half-life of 38 years and becomes concentrated in the food chain, particularly plants-to-milk. The ban on atmospheric testing of nuclear weapons has reduced this hazard. Strontium-90 does have some industrial uses. Most people in developed countries receive minor exposure to radiation through medical procedures such as X-ray and various treatments for some diseases. 

Yttrium 90, which has a half-life of 64.2 h, is produced from the fission product strontium 90, which has a half-life of 27.5 years. How much Y-90 will be present after 1 week from a sample of pure Sr-90 in a closed container ... 

Radioactive sources of commercial interest are y- and /3-ray emitters. The choice of sources has narrowed down to roughly three elements— cobalt-60, strontium-90, and cesium-137—as a result of their useful characteristics, reasonably long half-life, availability, and cost. 

The Sr-82 used in these studies was produced by spallation of a molybdenum target with 800 MeV protons at the Los Alamos Meson Physics Facility (LAMPF) and radiochemically separated by the Nuclear Chemistry Group at Los Alamos Scientific Laboratory (LASL) (22). The major radionuclidic contaminant in the Sr-82 is Sr-85 which is present in at least 1 1 ratio relative to Sr-82. The actual ratio depends upon the length of time after the production of radioactive strontium. Because of the 65 day half life of Sr-85 and the 25 day half life of Sr-82, the Sr-85 Sr-82 ratio increases with time. Other radionuclides found by the Hammersmith group in the processed Sr-82/85 shipment were Sr-89 ( 1%), Sr-90 ( 0.01%), Co-58 ( 1%) and Rb-84 ( 1%) from (17). 

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) ... 

Tritium, Carbon-14, and Strontium-90. The other extreme of detectability might be thought to be low energy betas from hydrogen-3. Hydrogen-3 (tritium) emits an 18.6 k.e.v. 0-ray with a half-life of 12.26 years (no 7-rays). The sample sizes here must be small to permit detection of the 0-rays by the apparatus. Nevertheless, the detection sensitivities for these radioactivities are of the order of 10-3 pCi per gram. 

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. 

Example If we start with 1.000 g of Strontium-90, how much will remain after 5.00 years if the half-life of Sr-90 is 28.8 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 ... 

Evidence gathered in 1997 at the Hanford facility for nuclear waste storage shows some leaking into the surrounding soil. On the other hand, the most potent nuclear waste products (plutonium, cesium, and strontium) do not move far (they become adsorbed on soil), although technetium (with a half-life of 250,000 years) has reached the water table. 

Figure 14.3 Decay of 10.0 grams of strontium (Sr), which has half-life of 28.8 years.

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,... 

The correct answer is (C). 87.5 percent decomposed is the same thing as saying that strontium 90 has undergone three half-lives (50 percent decomposes in the first half of that, or 25 percent in the second, and half of that again, 12.5 percent decomposes in the third). Once that has been determined, the problem can be solved by multiplying the half-life by the number of half-lives ... 

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 decay of a 10.0-g sample of strontium-90 over time. Note that the half-life is a constant 28.8 years. 

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