Nuclear properties decay half-lives

In a description of nuclear properties, the half-life,, is quoted rather than the decay constant. This quantity is the time it takes for one-half of the original nuclei to decay. That is,... 

For the synthetic transuranium elements, nuclear properties and methods of production have an overwhelming impact upon the velopment of knowledge concerning their chemical properties. In the case of einsteinium, only the isotopes Es and Es can be produced in quantities sufficient for chemical investigations and even the more abundant of the two isotopes, Es, is limited to amounts of 2 mg or less. iJi addition, the 20 day alpha decay half-life of Es... 

Approximately 25—30% of a reactor s fuel is removed and replaced during plaimed refueling outages, which normally occur every 12 to 18 months. Spent fuel is highly radioactive because it contains by-products from nuclear fission created during reactor operation. A characteristic of these radioactive materials is that they gradually decay, losing their radioactive properties at a set rate. Each radioactive component has a different rate of decay known as its half-life, which is the time it takes for a material to lose half of its radioactivity. The radioactive components in spent nuclear fuel include cobalt-60 (5-yr half-Hfe), cesium-137 (30-yr half-Hfe), and plutonium-239 (24,400-yr half-Hfe). 

Table 1 summarizes some of the important properties of the carbon isotopes. Note that only the rare ( 1%), naturally occurring, stable carbon isotope, namely, C, has a nuclear spin and is observable by NMR. The organic chemist is fortunate that 99% of natural carbon is the isotope C with no nuclear spin, so that proton and carbon-13 NMR spectra of organic compounds are not complicated by spin - spin splitting arising fi om adjacent carbon atoms. The radioisotope C is made by thermal neutron irradiation of lithium or aluminum nitride (equation 1). It decays back to stable yN by jS emission, with a half-life of 5570 years (equation 2). Cosmic rays generate thermal neutrons, which leads to the formation of C02 in the atmosphere (equation 1). Metabolism of... 

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. 

Example C and 0 are difficult to separate chemically because they have similar chemical properties, yet the two isotopes have different nuclear stability. Carbon-12 is a stable nuclide, whereas carbon-14 decays with a half-life of 5730 y (see Section 17.7). 

The rate (frequency) of disintegration is an inherent property of a given radioisotope and varies widely among isotopes. The half-life (time of survival of half the initial set of radioactive atoms) may be millions of years (e.g., Np) to a fraction of a second (e.g., P). Since disintegrations in a small interval of time are rare and independent of other time intervals, disintegration in equal finite intervals follows the Poisson distribution. The probability of atoms still being radioactive, P(0) (in which 0 indicates no nuclear transformations), after t intervals with a decay constant 6 (= fraction of radioactive atoms decayed per interval, if seconds, 5 if days) thus equals... 

---