Nuclide production

The presence of short-lived nuclides like Ca and Al imply a very short time scale between stellar nucleosynthesis and the formation of planetary bodies. To accommodate this time constraint, it is tempting to try to include some of the short-lived nuclide production... 

The concentration of the radioactive nuclide (reactant, such as Sm) decreases exponentially, which is referred to as radioactive decay. The concentration of the daughter nuclides (products, including Nd and He) grows, which is referred to as radiogenic growth. Note the difference between Equations l-47b and l-47c. In the former equation, the concentration of Nd at time t is expressed as a function of the initial Sm concentration. Hence, from the initial state, one can calculate how the Nd concentration would evolve. In the latter equation, the concentration of Nd at time t is expressed as a function of the Sm concentration also at time t. Let s now define time t as the present time. Then [ Nd] is related to the present amount of Sm, the age (time since Sm and Nd were fractionated), and the initial amount of Nd. Therefore, Equation l-47b represents forward calculation, and Equation l-47c represents an inverse problem to obtain either the age, or the initial concentration, or both. Equation l-47d assumes that there are no other ot-decay nuclides. However, U and Th are usually present in a rock or mineral, and their contribution to " He usually dominates and must be added to Equation l-47d. 

Often n=N—l Pressure parent nuclides Production rate temporary parameter Cooling rate temporary parameter... 

For production of radionuclides during the case of single-stage, continuous exposure without erosion, burial or uplift during nuclide production, Lai (1991) has shown that concentration of the radionuclide scales as ... 

Kouwenberg LLR, Kiirschner WM, McElwain JC (2007) Stomatal frequency change over altitudinal gradients prospects for paleoaltimetry. Rev Mineral Geochem 66 215-242 Lai D (1988) In situ-produced cosmogenic isotopes in terrestrial rocks. Ann Rev Earth Planet Sci 16 355-388 Lai D (1991) Cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models. Earth Planet Sci Lett 104 424-439... 

Raisbeck GM, Yiou F, Jouzel J, Petit JR (1990) 10Be and d2H in polar ice cores as a probe of the solar variability s influence on climate. Phil Trans Royal Soc London A 330 471-480 Reedy RC, Nishiizumi K, Lai D, Arnold JR, Englert PAJ, Klein J, Middleton R, Jull AJT, Donahue DJ (1994) Simulations of terrestrial in-situ cosmogenic nuclide production. Nucl Instrum Methods Phys Res B 92 297-300... 

Lai, D. (1991) Cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models. Earth Planet. Sci. Lett., 104, 424-39. 

Masarik, I, Reedy, R. C. (1995) Terrestrial cosmogenic-nuclide production systematics calculated from numerical simulations. Geochim. Cosmochim. Acta, 136, 381-95. 

Cosmogenic formed in space, or in the atmosphere as it relates to certain nuclide production. 

The rate of nuclide production is dependent on the number and the energy of particles bombarding the target, the cross section of the target and the half-life of the product (see Table 21.7). The decay of these products can be a source of significant amounts of energy, as already discussed. 

Nuclide Production Type of Half-Life Reaction Target Separation... 

Radionuclidic Purity Radionuclidic purity is defined as the fraction of the total radioactivity in the form of the desired radionuclide present in a radiopharmaceutical. Radionuclide impurities may arise from impurities in the target material or from fission of heavy elements in the reactor [2], In radionuclide generator systems, the appearance of the parent nuclide in the daughter nuclide product is a radionuclidic impurity. In a "Mo/"mTc generator, "Mo may be found in the "mTc eluate due to breakthrough of "Mo on the aluminum column. The presence of these extraneous radionuclides increases the radiation dose to the patient and may also obscure the scintigraphic image. 

Radio- nuclide Production Decay mode and half-life [y] Production rate [atoms per m2 per y] Range of dating [y] Application... 

Masarik J. and Reedy R. C. (1994) Effects of bulk composition on nuclide production processes in meteorites. Geochim. Cosmochim. Acta 58, 5307-5317. 

Reedy R. C. (1987a) Nuclide production by primary cosmic-ray protons. Proc. 17th Lunar Planet. Sci. Conf. Part 2 J. Geophys Res. 92, E697-E702. 

Reedy R. C. (1987b) Cosmogenic nuclide production in small metallic spherules. Lunar Planet. Sci. XVIII. Lunar and Planetary Institute, Houston, pp. 820-821. 

Figure 11 Comparison between the fluctuations in the fraction of red-coated lithic grains (dashed curve) with that of cosmogenic nuclide production (smooth curve) in the Earth s atmosphere. This correspondence provides powerful evidence that the Holocene s small cyclic temperature changes were paced by changes in solar luminosity (source...

Bard E., Raisbeck G. M., Yiou F., and Jouzel J. (1997) Solar modulation of cosmogenic nuclide production over the last millennium comparison between and Be records. Earth Planet. Set Lett. 150, 453 162. 

The production rate of Be (half-life = 53 d) as a function of latitude and elevation by Lai and Peters (1967) is shown in Figure 9. Approximately one-third of the nuclide production rate is in the troposphere and two-thirds in the upper atmosphere (stratosphere and higher). This partitioning is valid for all radionuclides except where most is produced by secondary neutrons in the vicinity of the tropopause. 

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