Thorium decay chain

Soon after this discovery the harnessing of the technique to the measurement of all the U isotopes and all the Th isotopes with great precision immediately opened up the entire field of uranium and thorium decay chain studies. This area of study was formerly the poaching ground for radioactive measurements alone but now became part of the wonderful world of mass spectrometric measurements. (The same transformation took place for radiocarbon from the various radioactive counting schemes to accelerator mass spectrometry.)... 

In this volume, for the first time, all the methods for determining the uranium and thorium decay chain nuclides in Earth materials are discussed. The range of problems solvable with this approach is remarkable—a fitting, tribute to the Curies and the early workers who discovered them for us to use. 

X 10 yr) and ends with stable ° Pb, after emission of eight alpha (a) and six beta (jS) particles. The thorium decay series begins with Th (ti/2 = 1.41 X 10 °yr) and ends with stable ° Pb, after emission of six alpha and four beta particles. Two isotopes of radium and Th are important tracer isotopes in the thorium decay chain. The actinium decay series begins with (ti/2 = 7.04 X 10 yr) and ends with stable Pb after emission of seven alpha and four beta particles. The actinium decay series includes important isotopes of actinium and protactinium. These primordial radionuclides, as products of continental weathering, enter the ocean primarily by the discharge of rivers. However, as we shall see, there are notable exceptions to this generality. 

There are four radionuclide systems used in the geochronometry of marine deposits C, the uranium and thorium decay chains, cosmogenic (2) nuclides other than and, for detrital volcanic... 

In a gamma-ray spectrum, the reexamination may consist of considering details of the sample plus detector background. For example, peaks in soil samples at 766 and 835 keV that may be falsely attributed to Nb and Mn, respectively, actually can be minor gamma rays in the natural uranium and thorium decay chains. For measurements near or below the MDA, the usual peak identification and quantification software can be replaced with one that is more or less responsive to channel-by-channel fluctuations. 

Antineutrinos emanate from the Earth, primarily from beta decays in the uranium and thorium decay chains. The total signal is estimated to be 50 to 150/year for a 1000 ton detector. The maximum geologic antineutrino energy is 3.27 MeV, corresponding to a 2.5 MeV energy deposition in the detector. Virtually aU of these low energy events will be removed by the 3 MeV cut on the deposited positron energy. 

The 52 second rare-gas member of the thorium decay chain Rn escapes from the thorium deposit and decays to shortlived which then decays to ThB(Pb ) (see Figure 2). The charged recoil atom Is collected on the electrode. The highest efficiency (20jS) of collection of the thorium B was achieved by Morlmoto and... 

Bie most common supply of carrier-free lead radioisotopes has been natural radium or thorium samples, Due to the presence of appreciable amounts of stable lead In pitch-blend which Is the principle source of radium or In thorium ores It Is necessary to obtain the carrier-free material from a sample which has previously been purified from lead. A convenient separation Is that of diffusion of the noble gas member of the radium or thorium decay chain from the parent material and its subsequent decay to radioactive lead Isotopes. Very early In the studies of radioactivity It was found that very high specific RaD(Pb ) sources could be obtained by... 

The need to exclude low levels of natural radionuclides from unnecessary legislation was recognised at an early stage in the UK. The Radioactive Substances Act (RSA, 1993) defined eight radioelements, all within the natural uranium and thorium decay chains, that constituted radioactive material only if present above a certain threshold. Problems arose with anthropogenic radionuclides, not considered above, and owing to various, established practices that required a large number of bespoke and somewhat ad hoc exemption orders the most important of which in the current context was the Phosphatic Substances and Rare Earths etc. Exemption Order (PSRE). The need for elemental activity concentrations meant that, polonium for example was calculated from ... 

A potential complication in the calculation of the annual dose arises from the possibility that the irraniirm or thorium decay chains may not be in eqttilibriirrrt the most commonly observed cause of diseqttiUbriirm is eseape of... 

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