Radionuclides nuclear properties

A wide range of metal radionuclides is used for the diagnosis of disease. Although they are selected on the basis of favorable physical and nuclear properties, the chemical properties of these radionuclides play a vital role in the development of new and improved techniques (267). Some of the metal radionuclides which are suitable for use in diagnosis and/or therapy are listed in Table III. 

Atoms with the same number of protons, but different numbers of neutrons in their nuclei are chemically identical atoms of the same element, but have different masses and may differ in their nuclear properties. Such atoms are isotopes of the same element. Some isotopes are radioactive isotopes, or radionuclides, which have unstable nuclei that give off charged particles and gamma rays in the form of radioactivity. Radioactivity may have detrimental, or even fatal, health effects a number of hazardous substances are radioactive, and they can cause major environmental problems. The most striking example of such contamination resulted from a massive explosion and fire at a power reactor in the Ukrainian city of Chernobyl in 1986. 

The more the analyst knows concerning the numerous nuclear and radiochemical properties and characteristics of the analyzed radionuclide, the easier it is to select the most appropriate analysis and to resolve problems in ascertaining the quality and validity of the results. Especially for non-routine sample analysis, the nuclear properties of the radionuclide of interest must guide selection of the method of analysis and detection. The appropriate passages of the accompanying text Radioanalytical Chemistry are referenced when more detailed discussions are needed. 

Research in nuclear and radiochemistry comprises Study of radioactive matter in nature, investigation of radioactive transmutations and of nuclear reactions by chemical methods, hot atom chemistry (chemical effects of nuclear reactions) and influence of chemical bonding on nuclear properties, production of radionuclides and labelled compounds, and the chemistry of radioelements - which represent more than a quarter of all chemical elements. 

The suitability of a radionuclide for a particular medical application will depend upon its availability in a radiochemically pure form, its nuclear properties and its chemical properties. In respect of the first of these considerations it is necessary to eliminate any extraneous radiation sources from a material destined for medical use. This need for very high radiochemical purity has a bearing on the means by which the radionuclide is produced. One potential method is by nuclear fission of a heavy element. This approach has the advant e that carrier free radioisotopes of high specific activity may be produced. However, because the process produces a complex mixture of FPs, painstaking separation and purification of the desired radionuclide will be necessary. The problem is simplified somewhat by using a pure target isotope to produce an FP which has rather unique properties. Thus fission produces which may be separated from the other FPs by virtue of its volatility. Fission in pure may also be used to prepare Mo in carrier free form, although contamination by Ru, I and Te was a problem in early... 

The majority of the longer-lived transuranic nuclides produced by neutron capture reactions decay primarily by a-emission. Most environmental samples contain radionuclides from the natural uranium and thorium series in concentrations often many times greater than transuranic concentrations. As a result, the chemical problems encountered in these measurements are derived from the requirement that separated trans-uranics should be free of a-emitting natural-series nuclides which would constitute a-spectrometric interferences. Table I lists those transuranic nuclides detected to date in marine environmental samples, together with some relevant nuclear properties. Their relative concentrations (on an activity basis) are indicated although the ratios may be altered by environmental fractionation processes which enrich and deplete the relative concentrations of the various transuranic elements. Alpha spectrometric measurements do not distinguish between 239p Pu, so these are... 

Basic nuclear science includes the synthesis of radionuclides, production of new elements, generation of radioactive and exotic nuclear beams, determination of nuclear properties, and applications of nuclear spectroscopy. 

In 1965, Richards and his collaborators at Brookhaven National Laboratories (N.Y.) have introduced the Mo/ Tc generator for clinical application (Richards 1966). This radionuclide system made technetium-99m available for clinical research and has stimulated the development of the first labeled compounds, which had a considerable impact on radiochemistry and nuclear medicine (Andros et al. 1965 Harper et al. 1966 McAfee et al. 1964a, b Stern et al. 1965, 1966). In the years to follow, diagnostic nuclear medicine procedures based on " Tc pharmaceuticals increased to approximately 85%. The reasons for this rapid growth were the ideal nuclear properties of techne-tium-99m, its availability worldwide as a radionuclide generator system, and the development of new labeling techniques. 

RADC (Ref. 9) A zero-dimensional, steady-state inventory code for calculating the overall plant mass balance for an abitrary number of radionuclides, including the total core inventory, the circulating inventory, the plateout inventory, and the He Purification System inventory. The current version of RADC contains a 250-nuclide library with the nuclear properties (decay constants, fission yields, etc.) from the 1978 compilation by Meek and Ryder. RADC has been used extensively to calculate the source terms that appear in Section 11.1 of previous HTGR PSARs and of the Standard MHTGR PSID. 

Radioactive metals can be used in radio-release methods for the determination of oxidizing agents in aqueous solutions. The decisive factors in the choice of the metal are the following the metal should not react with water, but should react with oxidizing agents to yield ions that do not form precipitates in aqueous media the metal should have a radionuclide with suitable nuclear properties. These conditions are met by thallium ( " TI) and silver ( ° Ag). 

The radionuclide is a very useful analog label for producing radiotracers. Its nuclear properties are also almost ideal for SPECT studies. The radionuclide is very broadly used... 

Nuclear properties of some gamma and positron emitting diagnostic radionuclides (ICRP 1983)... 

Different isotopes have different natural abundances. For example, 99.3% of naturally occurring uranium is uranium-238, 0.7% is uranium-235, and only a trace is uranium-234. Different nuclei also have different stabilities. Indeed, the nuclear properties of an atom depend on the number of protons and neutrons in its nucleus. Recall that a nuclide is a nucleus with a specified number of protons and neutrons. (Section 2.3) Nuclei that are radioactive are called radionuclides, and atoms containing these nuclei are called radioisotopes. 

---