Nuclide radioactive

Krypton-85 has been used for over 25 years to measure the density of paper as it is amanufactured. The total weight of paper can be controlled to a very accurate degree by the use of krypton 85 and other radioactive nuclides. The common name for such a device is a beta gague that can measure the thickness of a material. 

Elements with radioactive nuclides amongst their naturally occurring isotopes have a built-in time variation of the relative concentration of their isotopes and hence a continually... 

Bromine-82 has a half-life of 36 hours. A sample containing Br-82 was found to have an activity of 1.2 X 105 disintegrations/min. How many grams of Br-82 were present in the sample Assume that there were no other radioactive nuclides in the sample. 

We can use Fig. 17.13 to predict the type of disintegration that a radioactive nuclide is likely to undergo. Nuclei that lie above the band of stability are neutron rich they have a high proportion of neutrons. These nuclei tend to decay in such a way that the final n/p ratio is closer to that found in the band of stability. For example, a l4C nucleus can reach a more stable state by ejecting a (3 particle, which reduces the n/p ratio as a result of the conversion of a neutron into a proton (Fig. 17.15) ... 

The earliest studies in this field were conducted largely to benefit from the Szilard-Chalmers effect—namely, the separation of radioactive atoms from the bulk material—in order either to make nuclear chemical study of radioactive nuclides or to effect an enrichment of radioisotopes. In Table II are listed some selected works of this type. 

The only respect in which the hot atom chemistry of organometallic compounds has so far been applied to other fields of study is in the area of isotope enrichment. Much of this has been done for isolation of radioactive nuclides from other radioactive species for the purpose of nuclear chemical study, or for the preparation of high specific activity radioactive tracers. Some examples of these applications have been given in Table II. The most serious difficulty with preparation of carrier-free tracers by this method is that of radiolysis of the target compound, which can be severe under conditions suited to commercial isotope production, so that the radiolysis products dilute the enriched isotopes. A balance can be struck in some cases, however, between high yield and high specific activity (19, 7J),... 

As shown in Example, Equation is used to find a nuclear half-life from measurements of nuclear decays. Equation is used to find how much of a radioactive substance will remain after a certain time, or how long it will take for the amount of substance to fall by a given amount. Example provides an illustration of this t q)e of calculation. In Section 22-1. we show that Equation also provides a way to determine the age of a material that contains radioactive nuclides. 

One of the problems with radioactive nuclides such as Pu is that their decay cannot be stopped, so... 

C22-0023. Potassium-40 is a radioactive nuclide that occurs naturally. This nuclide emits 3 particles with the... 

Each radioactive nuclide has a characteristic, constant half-life. This means that it acts as a clock, ticking ... 

P, a radioactive nuclide with a half-life of 14.3 days. The amount of the nuclide present is cut... 

Radioactive dating is most valuable in estimating the age of materials that predate human records, such as the Earth itself Calculating the age of a sample from the amounts of its radioactive nuclides and their decay products... 

If the amount of a radioactive nuclide in a rock sample is N, the sum of this amount plus the amount of its product nuclide is A/q. For argon dating, Nq is the sum of potassium-40 and argon-40 present in a sample of rock. Assuming that Ar gas escapes from molten rock but is trapped when the rock cools and solidifies, the lifetime obtained by substituting these values into Equation is the time since the rock solidified. Such analyses show that the oldest rock samples on Earth are 3.8 X 10 years old. 

Analyses of this type are correct only if all of the product nuclide comes from radioactive decay. This is not known with certainty, but when age estimates using different pairs of nuclides give the same age and samples from different locations also agree, the age estimate is likely to be accurate. Note also that 3.8 X 10 years agrees with the qualitative limits derived from naturally occurring radioactive nuclides. 

Radioactivity serves as a useful clock only for times that are the same order of magnitude as the decay half-life. At times much longer than t j2, the amount of radioactive nuclide is too small to measure accurately. At times much... 

C22-0051. A radioactive nuclide of mass number 94 has been prepared by neutron bombardment. If 4.7 pg of this nuclide registers 20 counts per minute on a radioactivity counter, what is the half-life of this nuclide ... 

The concept most commonly used when dealing with radioactive nuclides is activity. By definition, the activity of a number of atoms of a nuclide is the number of decay events per unit of time. The law of radioactivity tells us that this activity is equal to the decay constant times the number of atoms. 

Suppose the initial number of nuclei of a radioactive nuclide is N0, and that the half-life is T. Then the amount of parent nuclei remaining at a time t can be written as Nx = NQ( /2)(tlT>. This relationship is called the radioactive decay equation. What is the number of daughter nuclei present at time t, expressed in terms of N0 and Nx ... 

Decay Constant (A,)—The fraction of the number of atoms of a radioactive nuclide which decay in unit time (see Disintegration Constant). 

Iwata, E., Measurement of Gaseous Radioactive Nuclides in the Atmosphere, Faculty of Science, Kanazawa University, Master Thesis (1986). 

A hollandite structure phase containing Ba, Ti, Al, and O is fabricated with the aim of immobilizing radioactive nuclides, (a) What is the formula of the hollandite (b) It is desired to replace 10% of the Ba with radioactive K. What would the formula of the new phase be (c) It is desired to replace 35% of the Ba with radioactive Sr. What would the formula of the new phase be (d) It is desired to replace 17% of the Ba with radioactive La. What would the formula of the new phase be ... 

Carrier-free radiochemical is a radionuclide that is not contaminated with a stable or radioactive nuclide of the same element. The no carrier added (NCA) designation applies to most of the elements to which the term carrier free is indicated. The specific activity of a carrier-free radioisotope can be calculated by the following formula ... 

Mass-spectroscopic technique has also been used with non-fissile targets after pile or cyclotron bombardment to determine the mass-numbers of radioactive nuclides. In one case, the branching ratios of certain isotopes for and electron capture decay (where different elements are produced by the two routes) were determined from the amount of the stable end-products of radioactive decay, using the mass-spectrometer to identify the isotopes concerned and to correct for any stable impurities of the elements concerned (98). For some purposes, mass-spectroscopic separations could be very valuable technically such as the... 

Accelerator mass spectrometry Instrumental technique for direct enumeration of low-level radioactive nuclides. 

Most radioactive nuclides employed in radiopharmaceuticals have a short half-life. This is beneficial to the patient as the total number of radioactive atoms given to the patient to produce an image is small when the half-life of the radioactive nuelide is short, as compared to longer half-life radioactive nuclides. Fewer total atoms reduce the radiation dose to the patient and thus the risk from a nuclear medi-eine procedure. However, the short half-life of the radioactive nuclide results in a short shelf-life for the radiopharmaeeutical. As a result, most radiopharmaceuticals are eompounded on a daily basis. The most common radioactive nuclide used for this purpose is technetium-99m (Te-99m) with a half-life of 6 hr, emiting only gamma radiation with an energy almost ideal for detection. 

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