Long-lived isotope

In addition to stable elements, radioactive elements are also produced in stars. The unstable but relatively long-lived isotopes °K, Th, and make up the internal heat source that drives volcanic activity and processes related to internal convection in the terrestrial planets. The short-lived transuranium elements such as Rn and Ra that are found on the Earth are all products of U and Th decay. 

These isotopes are sometimes used as tracers of natural terrestrial processes and cycles. Long-lived isotopes, such as Rb and Sm are used for precise dating of geological samples. When the solar system formed it also contained several short-lived isotopes that have since decayed and are now extinct in natural systems. These include Al, Fe, Pu, Pd, and Al with a half-life of less than a million years is particularly important because it is a potentially powerful heat source for planetary bodies and because its existence in the early solar system places tight constraints on the early solar system chronology. 

C22-0092. The long-lived isotope of radium, Ra, decays by a emission with a half-life of 1622 years. 

However, thorium has only two naturally occurring long-lived isotopes, and all Th measurements by TIMS are limited by the absence of a well-constrained isotope ratio that can be used for internal normalization purposes to correct for instrumental mass fractionation. In this regard, one of the most important advantages of MC-ICPMS over MC-TIMS is the ability to admix two elements with overlapping mass ranges and use the... 

In magmatic processes, both parent and daughter nuclides are usually present in the solid sources, magmas and crystallizing minerals, so that (N2), which is a priori unknown, cannot be neglected. In order to solve Equation (I) for t, the age of fractionation, both terms of this equation are divided by the concentration of a stable isotope (or the activity of a long-lived isotope) of the daughter element. Such a normalization, similar to those used in other classical radiometric methods (Rb-Sr, Sm-... 

The relationship between Th isotopes and long-lived isotope systems... 

Figure 22. U-Th equiline diagram showing U-Th isotopes may be sensitive to the effects of assimilation of pre-existing (>350 kyr) arc basalts or continental crast. This is much more complicated using long-lived isotopic systems (e.g., Sr/ Sr or " Nd/ " " Nd) because in these systems pre-existing arc basalts will be indistinguishable from new magmas and crastal assimilation will be hard to distinguish from subducted sediment addition unless assimilation is coupled to differentiation.

We will show below that the initial Pa/ U = zero assumption holds for a number of corals that have typical low Th concentrations. Initial Pa/ U values for most other carbonates have not been studied in detail. Furthermore, in contrast to thorium, there is no long-lived isotope of protactinium that can be used as an index isotope although some work has employed corrections for initial Pa. Such corrections essentially assume that Th is an isotope of protactinium and assume a bulk earth Th/ U ratio and secular equilibrium between Pa and U. The term for applying this correction is analogous to the initial Th term in Equation (3). 

One of the potential ways to improve repository performance dramatically is through transmutation of long-lived isotopes. We have embarked on a roadmapping process for Accelerator Transmutation of Waste, together with colleagues from Japan, Russia, France, and other countries. 

Once uranium is incorporated into buried bone, shell, coral, or speleothems, the isotope uranium-235 decays, initially into the short-lived isotope (thorium-231) and then into long-lived protoactinium-231. Uranium-238, on the other hand, decays first into two successive short-lived isotopes (thorium-234 and protoactinium-234) and only then into a long-lived isotope, uranium-234 (see Fig. 12). The decay of uranium-235 to long-lived protoactinium-231 is used to date events up to 150,000 years in age that of uranium-234 (derived from uranium-238) to thorium-230 is of use for dating events within the time range 1000-500,000 years. 

Atomic weights are those of the most commonly available long-lived isotopes on the 1999 lUPAC Atomic Weights of the Elements A value given in square brackets denotes the mass number at the longest-lived isotope... 

Among the long-lived isotopes of technetium, only Tc can be obtained in weigh-able amounts. It may be produced by either neutron irradiation of highly purified molybdenum or neutron-induced fission of uraniimi-235. The nuclides Tc and Tc are exclusively produced in traces by nuclear reations. Because of the high fission yield of more than 6%, appreciable quantities of technetimn-99 are isolated from uranium fission product mixtures. Nuclear reactors with a power of 100 MW produce about 2.5 g of Tc per day . 

The relatively long-lived isotopes of Pu suitable for chemistry and metallurgy are those of masses 238, 239, 240, 241, 242, and 244. Plutonium formed in nuclear reactors occurs as a mixture of isotopes. A typical isotopic composition of Pu in spent fuel containing 10.4 kg of Pu/ton of fuel is given in Table VIII. 

The isotopes of Cm available in multigram quantities are Cm with a Ti/2 of only 163 days and Cm with a longer Ti/2 of 18.1 years, still inconveniently short for chemical studies. These isotopes are made by successive neutron captures of Pu in a nuclear reactor. The two relatively long-lived isotopes of Cm, available only in few-mg amounts, are Cm with a Tiy2 of 4730 years and Cm with a Ti/2 of 3.4 x 10 years. The cost of these two isotopes, measured in terms of neutrons used in their formation, is so great that it is probable that only milligram quantities will ever be available for study. The isotope Cm is obtained in >90% isotopic purity from the a-decay of Cf. All of... 

Numerous nuclear reactions have been employed to produce astatine. Three of these are particularly suited for routine preparation of the relatively long-lived isotopes with mass numbers 209, 210, and 211. The most frequently used is the ° Bi(a,xn) At (a = 1-4) reaction, in which bismuth 44, 74,120) or bismuth oxide (7,125) is bombarded by 21-to 40-MeV a-particles. The ° Bi(He, xn) At reaction can also be used to produce isotopes of astatine 152), the nuclear excitation functions (62) favor a predominant yield of ° At and °At. The routine preparation of astatine is most conveniently carried out through the ° Bi(a,xn) At nuclear reactions, from which a limited spectrum of astatine nuclides may be derived. The excitation functions for these nuclear reactions have been studied extensively (78, 89, 120). The... 

The discovery of this element is credited to J.A. Marinsky and L.E. Glendenin who, in 1945, identified its long-lived isotope Pm-147 (ti/2 2.64 years) in the fission products of uranium. They named the element after Prometheus, who according to Greek mythology stole fire from heaven. The element was first isolated from fission product wastes by G.W. Parker and P.M. Lantz in 1948. It first was recovered from natural sources by O. Erametsa in 1965. An amount less than 0.5 g was recovered from 20 tons of rare earths. 

Investigation of physical and chemical properties of recently synthesized, relatively long-living isotopes of superheavy elements (SHEs) with nuclear charges Z=105 to 116 [1, 2, 3, 4] and their compounds is of fundamental importance. Their measured lifetimes may reach several hours and the nuclei near the top of the island of stability are predicted to exist for many years. The experimental study of the SHE properties is very difficult be-... 

Hulubei s reported stable or long-lived isotope, if actually polonium, might be a nuclear isomer of a species which is already known. 

Americans used TNT, RDX and HMX for nuclear weapons in the initial years but their use posed additional hazard of aerosolized-plutonium dispersal. The scattering of this long-lived isotope poses a great danger to human life as well as... 

The isotopic compositions of several elements have changed since the formation of the solar system. Radioactive isotopes have decayed, and the abundances of their daughter isotopes have increased over time. For long-lived isotopes of particular importance to radiochronology (flagged with an asterisk), Table 4.2 gives both the present abundance and the abundance at the time the solar system formed (italicized values). 

Uranium has two long-lived isotopes, 235U and 238U, that decay to 207Pb and 206Pb, respectively. Thorium has one long-lived isotope, Th, that decays to Pb. The isotopic abundances of uranium and thorium are summarized in Table 8.5. The isotopic abundances of terrestrial lead are given in Table 4.2. 

Finally it is worth noting that, unlike sulfur, selenium and tellurium, neither stable nor long-lived isotopes of polonium are known in nature. The only readily accessible isotope of polonium is polonium-210 which is the penultimate member of the radium decay series and which decays by a-emission with a half-life of 138.4 days. 

The inside cover of this book lists the atomic number (the integer mass) of the long-lived isotope of Ra, which is 226. 

The isotopic ratios, altered by spike additions, are then measured on a portion of the sample by mass spectrometry. Even though the method is limited to elements having two or more naturally occurring or long lived isotopes, it is very sensitive and accurate and relatively free from interference effects. Thus, it has a great advantage over other analytical techniques. Thermal source and electron bombardment mass spectrom-... 

CURIUM. CAS 7440-51-9], Chemical element- symbol Cm. at. no. 96, at. wt. 247 (mass number of the most stable isotope i, radioactive metal of the Actinide series, also one of Ihe Transuranium elements, mp estimated 1350 50 C. l7CTn has a half-life of 1.64 x It)7 years, Olher long-lived isotopes arc J,Cm (ti j =9320 years), 4, Cm = 54X0 years I. "Cm... 

NEPTUNIUM. [CAS 7439-99-8]. Chemical element, symbol Np, at. no, 93, at. wt, 237,0482 (predominant isotope), radioactive metal of the Actinide series, also one of the Transuranium elements. Neptunium was the first of [he Transuranium elements [o be discovered and was first produced by McMillan and Abelson (1940) at the University of California at Berkeley. This was accomplished by bombarding uranium with neutrons. Neptunium is produced as a by-pruduct from nuclear reactors. 237Np is the most stable isotope, with a half-life of 2.20 x 106 years, The only other very long-lived isotope is that of mass number 236. with a half-life of 5 x 10- years. 

In 1973, scientists at Oak Ridge National Laboratory and Lawrence Berkeley Laboratory, produced a relatively long-lived isotope of nobelium through the bombardment of 248C,m with 1 0 ions. A total half-title of 58-5 minutes was computed from the combined data of both laboratories, See also Chemical Elements... 

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