Radionuclides artificial

McCartney M, Kershaw PJ, Woodhead DS, et al. 1994. Artificial radionuclides in the surface sediments of the Irish Sea, 1968-1988. Sci Total Environ 141 103-138. 

The number of naturally occurring radionuclides is limited and few are of analytical value. For the majority of purposes artificial radionuclides are manufactured. Bombardment reactions are generally used in their production. A suitable target material is exposed to an intense flux of the appropriate particles in a nuclear reactor or particle accelerator such as a cyclotron. Thermal neutrons in the reactor... 

Artificial radionuclides Radionuclides produced by humans via the explosion of atomic bombs and in nuclear reactors. 

Fluorine-18 is an artificial radionuclide, discovered in 1937. It decays with a half-life of 109.8 min for 97% by positron emission and for 3% by electron capture to the stable isotope oxygen-18. The maximum jS+-particle energy is 0.635 MeV [4],... 

Several organizations (e.g., NIST, NRC-Canada, and IAEA) provide sediment reference materials containing radionuclides, many of which are only certified for artificial radionuclides ( Cs, Sr, Am, and Pu). Certain specific radionuclides have no certified natural matrix materials, including ocean, lake, and river sediments. Although these sediments are certified for a few naturally occurring and artificial radionuclides, the extent of radioactive equilibrium of the uranium and thorium decay series in these environmental materials is not provided. NIST currently offers an ocean sediment Standard Reference Material (SRM 4357) in... 

Contamination of environment (artificial radionuclides) - nuclear power plants and accidents - nuclear weapons and weapon tests (e.g., nuclear fallout) Tc, 90Sr, 129l, Np, Pu, Th, Cm, Ra 236U/238 U, 240Pu/239 Pu U, Am,... 

Radionuclides occur in the environment in such minute physical quantities that they are commonly referred to as being present at sub- or ultra-trace quantities. As an illustration of this Livens and Rimmer (1988) presented values relating the masses and specific activities of several artificial radionuclides and their typical concentrations in surface soils of the UK (see Table 7-1). This indicates the very small mass usually associated with one Becquerel of radioactivity, although as the half life of a radionuclide increases so does the mass per unit of radioactivity. The molarity concept is... 

From the above it can be concluded that in many instances the introduction of an artificial radionuclide into the environment provides us with a natural tracer experiment. Indeed, this is the basis for the application of deterministic compartmental models, based on tracer kinetics, to radioecology (Whicker and Schultz, 1982). This approach is largely based on the assumption that radionuclide movements will exhibit first order kinetics although the existence of naturally-occurring tracees (stable isotopes) at relatively high abundance may result in more complex concentration-dependent kinetics. Furthermore, nutrient analogues may exert even more complex effects on processes such as radioion absorption across root plasma membranes this will become evident later in the chapter. 

In the next 50 years, more than 2000 other artificial radionuclides were synthesized. 

Radiopharmaceuticals are labeled with artificial radionuclides that are obtained by bombardment of stable nuclei with subatomic particles or photons. Nuclear reactions produced in such a way convert stable in unstable (radioactive nuclei). Several kind of devices are used for such purposes, including nuclear reactors, particle accelerators, and generators. 

Whereas in the past the determination of long-lived radionuclides was dominated by conventional radioanalytical techniques such as a spectrometry, for a few years now ICP-MS has been increasingly used for isotope analysis. Of special interest is the isotope analysis of natural radionuclides ( U, and " U) and especially of artificial radionuclides (236u, 2 °Pu, Am, I, °Sr and others) in environmental samples for evidence of... 

In addition to the analysis of artificial radionuclides, mass spectrometry is useful for characterizing naturally occurring radioactive materials (NORMs). NORMs consist of Th and... 

From that point, on the first artificial radionuclides C, P, and... 

The first artificial radionuclide, °P, was produced in 1934 by Frederic and Irene Joliot-Curie (daughter and son-in-law of Maria Sklodowska-Curie) by bombarding aluminium with protons in an accelerator [4]. Today, more than 2000 artificial radionuclides have been produced and identified, especially after the discovery and use of nuclear fission of uranium U and plutonium Pu. 

Neutron activation analysis (NAA) is a sensitive multielement analytical technique used for both qualitative and quantitative analyses of major, minor, trace, and rare elements. The NAA method is based on the transformation of stable nuclides into radioactive nuclides by bombarding the sample with neutrons, followed by measurement of radiation, particularly gamma radiation. Today, artificial radionuclides in samples can be measured in two ways [15, 16] ... 

A number of artificial radionuclides are produced as a result of activation during nuclear weapons tests, operation of reprocessing plants and reactors in nuclear power stations, and in nuclear studies. Modem radioanalytical techniques have enabled activation products such as Na, Cr, " Mn, Fe, °Co, Ni Zn, °Ag, and " Sb to be detected in the environment [28,29]. Stainless steel containing iron, nickel, and cobalt is an important material in nuclear power reactors and is used to constmct nuclear test devices or their supporting stmctures [30,31]. During neutron activation of the stable isotopes of cobalt, radioactive isotope °Co (J = 5.27 years) is produced. It is a beta emitter and decays into °Ni, with energy niax of... 

A number of natural and artificial radionuclides are, or could be, used as indicators for studying geochemical and biological processes in the natural environment and their concentrations are very low. 

The first case of a nuclear isomer was found in 1921 by Hahn, who proved by chemical methods the existence of two isomeric states of Pa which were called UX2 and UZ. The decay scheme of Pa is plotted in Fig. 5.13. Both nuclear isomers are produced by decay of Th. 234mp ( i/2 = T17m) changes at nearly 100% directly into Later, the production of artificial radionuclides by nuclear reactions led to the discovery of a great number of nuclear isomers. In the case of °Br, for instance, two isomeric states were found (Fig. 5.14), and chemical separation of somBr and °Br is also possible. From the change of nuclear spin and of parity half-lives can be assessed by application of the selection rules (eq. (5.40)) and of eqs. (5.37) and (5.38). The half-lives of nuclear isomers may vary between seconds and many years. 

Whole-body counters consist of a heavily shielded space. The person to be examined is placed inside and surrounded by a large number of scintillation detectors. In this way, y-emitting radionuclides in the body can be detected with high sensitivity and identified. In the absence of contamination by artificial radionuclides, the y radiation from is observed. The uptake of small amounts of artificial y-ray emitters such as Cs can be determined effectively, whereas pure a or p emitters cannot be detected in the body. 

Various artificial radionuclides were then applied in relatively large amounts for external and internal irradiation, and some of these radionuclides are still used in... 

Artificial radionuclides released by nuclear explosions, weapon tests and accidents have been deposited from the air as fall-out on soil and vegetation. In 1963 values of up to 0.8 Bq/1 °Sr and up to 1.2 Bq/1 Cs were measured in precipitations in central Europe. In 1964, the concentration of Cs in beef reached values of about 36 Bq/kg. Consequently, the concentration of Cs in man went up to about 11 Bq/kg. 

This was the first man-made radionuclide. From that time on many species of radionuclides were produced by bombardment of elements with charged particles using the various types of accelerators. In addition, practical use of fission energy allowed production of a great amount of artificial radionuclides, not only by neutron irradiation generated with nuclear reactors, but also by processing spent fuel. 

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