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Multiple decay modes on the Karlsruhe Nuclide Chart
(8th June 2007)
(Qu.) In the Karlsruhe Nuclide Chart, the main and subsidiary modes of decay are usually indicated by large and small triangles respectively inside the box (as in the 30.0 ms metastable state Ir-167m). However this is not the case with the nuclide Ir167 ground sate. What is the reason for this?
(Ans.) For most nuclides, there is usually one or two main decay mode (defined as modes with a branching ratio ≥ 5%) with subsidiary modes (branching ratio < 5%). In the case of Ir167 there are three decay modes with branching ratios ≥ 5%. In this case the box structure is modified to show all three modes.
The metastable state Ir-167m (30.0 ms) has the following decay modes and branching ratios:
α=0.8, ß+=0.196, p=0.004
hence the two main modes are α and ß+ (large yellow and red triangles) with the subsidiary mode p (small brown traingle, top left corner).
The ground state Ir-167 (35.2 ms) has the following decay modes and branching ratios:
α=0.48, p=0.32, ß+=0.2
since the brachnig ratios are all ≥ 5%, there are three main modes. In such a case, the decay modes are drawn as rectangles as shown.
In Nucleonica, the nuclide box structure is somewhat different from that of the Karlsruhe Nuclide chart. Here the box has a main mode (indicated here by the colour yellow) and subsiduary modes (indicated by the small red and brown triangles)
Is U-234 primordial?
(16th May 2007) from Dr Jesse Shore, Senior curator, Sciences, Powerhouse Museum, Australia
(Qu.) I have been studying the 7th edition of the chart of the nuclides to assist me in developing an exhibition about nuclear science. The chart indicates uranium 234 as primordial. I understand that it is a decay product in the U238 decay series and that it occurs in nature in small amounts. Given its half-life of approximately 2x10e5 years I would have thought that none of it is primordial and instead its abundance is solely from radiogenic parents. Have I misinterpreted the chart regarding this nuclide?
Nucleonica Team:
(Ans.) That's a very interesting question. You are absolutely correct. The U-234 is not primordial. However for all practical purposes it can be treated as being such.
Due to the relatively short half-life (2.5E5 y), any U-234 present following the supernova explosion (which led to the formation of our solar system) has of course decayed a long time ago. The U-234 in uranium is produced by the radioactive decay of U-238. Since the U-234 also decays with a half.life of 2.5E5 years, the U-234 is in "radioactive equilibriium" (where the production rate is balance by the decay rate) with its parent U-238. Due to this radioactive equilibrium, the amount of U-234 in uranium is significant - approximately 0.0054%.
The black rectangle in the nuclide chart allows us to allocate an abundance to this isotope (0.0054%). Uranium obtained from an ore will contain this amount of U-234. So as I said above it is convenient to treat it as primordial.
This raises other aspects too. Why for example is Th234 not "primordial". Although it has a half-life of only 24 days, it is in radioactive equilbrium with U-238. Well the answer is just that the amount of Th-234 is neglibible. For this reason there is no black rectangle.
Radiotoxicity of Po-210
(9th May 2007)
(Qu.) What is the effective dose obtained by inhalation of 1 µg Po210?
(Ans.) 700 Sv / µg.
Inhalation radiotoxicity of Po-210 vs. Pu-238
(9th May 2007)
(Qu.) What is the difference in inhalation radiotoxicity between Pu-238 and Po-210?
Nucleonica Team:
(Ans.) This information can be obtained form the Datasheets/ Derived Data: The inhalation radiotoxicity for Pu238 is 70 Sv /µg - a factor of only 10 lower than that for Po-210 (i.e. 700 Sv/µg).
Coloured text in the NucleonicaWiki?
(16th May 2007)
(Qu.) How do I use colours in the NucleonicaWiki?
(Ans.) This text shows the use of colours! For more information see Editing Help, HTML in Wikitext.
What are Auger Electrons?
A good explanation of this is given in the following animation on the Auger effect
See also wikipedia on this.
