Strontium radioactive decay

Strontium ion, Sr 2, can replace calcium ion in bone. If a product of radioactive fallout, strontium-90, 90sr+2, js placed in bone, however, its radioactive decay will destroy both bone and surrounding tissue. 

The rubidium-strontium geochronometer used in the Rb-Sr geochronological method is based on the radioactive 3 -decay of Rb to Sr. The growth of radiogenic Sr in a Rb rich mineral can be described by the following Equation (9.6). In the rubidium-strontium age dating method, the radioactive Rb isotope with a natural isotope abundance of 27.85 % and a half-hfe of 4.88 X 10 ° years is fundamental to the 3 decay to the isobar Sr. The equation for the Rb-Sr method can be derived from the general equation of radioactive decay (Equation 8.8 in Section 8.8) ... 

Figure 5. (top Strontium concentration vs. age for terrestrial mammal hone samples from the Marmes Rockshelter, Each point represents a single sample. The error bars represent the standard deviation based on the statistics of radioactive decay. 

Radioactive decay rates are measured in half-lives. A half-life is the time required for one-half of a radioisotope s nuclei to decay into its products. For example, the half-life of the radioisotope strontium-90 is 29 years. If you had 10.0 g of strontium-90 today, 29 years from now you would have 5.0 g left. Table 25-4 shows how this decay continues through four half-lives of strontium-90. Figure 25-13 presents the data from the table in terms of the percent of strontium-90 remaining after each half-life. 

All naturally occurring rubidium cores contain Sr, resulting from the beta decay of Rb. In naturally occurring rubidium, 278 of every 1 000 rubidium atoms are Rb. A mineral containing 0.85% rubidium was analyzed and found to contain 0.008 9% strontium. Assuming that all of the strontium originated by radioactive decay of Rb, estimate the age of the mineral. Rb has a half-life of 4.9 x lO years. 

Radioactive Strontium. 90Sr is not a naturally occurring substance its presence in the environment is a result of human activities, such as the prior testing of nuclear bombs in the air and leaks from radioactive storage and waste sites. Radioactive decay is the only way for decreasing the concentration of 90Sr. Eventually, all 90Sr will be converted to stable zirconium. 

Strontium is widely distributed in the earth s crust and oceans. Strontium is released into the atmosphere primarily as a result of natural sources, such as entrainment of dust particles and resuspension of soil. Radioactive strontium is released into the environment as a direct result of anthropogenic activities. Stable strontium can be neither created nor destroyed. However, strontium compounds may transform into other chemical compounds. Radioactive strontium is formed by nuclear reactions. Radioactive decay is the only mechanism for decreasing the concentration of radiostrontium. The half-life of 90Sr is 29 years. 

Because strontium is an element, its atoms do not degrade by environmental processes such as hydrolysis or biodegradation. However, radioactive strontium will be subject to radioactive decay and transformation to other elements. Eventually, all of the radioactive strontium will be transformed into stable zirconium by the process of radioactive decay (see Section 4.2) ... 

Radioactive decay is first order in the decaying isotope. For example, strontium-90 contained in fallout from nuclear explosions decays to yttrium-90 and a beta particle. Write the rate law for the decay of strontium-90. 

Two or more radioisotopes of the same element that cannot be measured by spectral analysis require integration of effective separation of impurities and radiation detection of the selected distinguishing decay characteristics. To determine the amounts of Sr and °Sr in a sample, for example, interfering radionuclides such as Ra and must be removed only then can the two strontium radioisotopes be distinguished in terms of the radioactive decay of Sr, ingrowth of the daughter, and detector response to beta-particle energies, as discussed in Section 6.4.1. 

Strontium-90 is used as a radioactive tracer in medical and agricultural studies. The heat generated by strontium-90 s radioactive decay can be converted to electricity for long-lived, lightweight power supplies. These are often used in remote locations, such as in navigational beacons, weather stations, and space vehicles. Strontium-90 is also used in electron tubes, as a radiation source in industrial thickness gauges, and for the treatment of eye diseases. Controlled amounts of strontium-90 have been used as a treatment for bone cancer. 

One of the most important properties of a radioactive nuclide is its lifetime. At present it is not possible to predict theoretically when any particular nucleus in a sample will decay. However, the number of nuclides in a sizeable sample that will decompose in a given time can be measured, and it is found that this rate of decay is characteristic of a given isotope. In fact, the rate of decay of an isotope is constant and unvarying. That is, if a fraction of a radioactive nuclide decays in a certain time interval f, then the same fraction of the remainder will decay in another increment of time f, irrespective of external conditions. Nuclear reactions are not affected by outside influences such as temperature and pressure and it is not possible to significantly alter the constant rate of radioactive decay. For example, radioactive strontium-90, an important... 

Radioactive decay is a first-order kinetic process. Recall that a first-order process has a characteristic half-life, which is the time required for half of any given quantity of a substance to react. (Section 14.4) Nuclear decay rates are commonly expressed in terms of half-lives. Each isotope has its own characteristic half-life. For example, the half-life of strontium-90 is 28.8 yr ( FIGURE 21.6). If we start with lO.O g of strontium-90, only 5.0 g of that isotope remains alter 28.8 yr, 2.5 g remains after another 28.8 yr, and so on. Strontium-90 decays to yttrium-90 ... 

It has been suggested that strontium-90 (generated by nuclear testing) deposited in the hot desert will undergo radioactive decay more rapidly because it will be exposed to much higher... 

Streptococcus—Any of various rounded disease-causing bacteria that occur in pairs or chains. Strontium (sr)—A silvery soft metal that rapidly turns yellow in air. Sr-90 is one of the radioactive fission materials created within a nuclear reactor during its operation. Stronium-90 emits beta particles during radioactive decay. 

Strontium-90, 3gSr, is a radioactive decay product of nuclear fallout from nuclear weapons testing. Because of its chemical similarity to calcium, it is incorporated into the bones if present in food. The half-life of strontium-90 is 28.1 y. What is the decay constant of this isotope What is the activity of a sample containing 5.2 ng (5.2 X 10 g) of strontium-90 ... 

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