360 



ISOTOPIC TRACERS AND NUCLEAR RADIATIONS [Chap. 13 



large specific ionization, under certain conditions each particle crossing the 

 sensitive volume of the chamber will be recorded. Corrections for absorption 

 and geometry can then be readily made to determine the absolute number of 

 particles emitted. By this technique, Kovarik and Adams [4] showed that 

 1 gm of uranium emits a total of 2.501 X 10 4 alpha particles per second. 



Fig. 100. Alpha-particle ionization chamber. Principal components are: A, high-voltage 

 electrode on which sample is mounted; B, collecting electrode; C, guard ring; D, bottom 

 plate; E, breach thread; F, amphenol insulator; G, high-voltage wiping contact; H, inlet 

 for nitrogen or argon. [Redrawn from A. II. Jaffey, T. P. Kohman, and J. A. Crawford, 

 U.S. Atomic Energy Commission Report MDDC-388, 1946.] 



Knowing the isotopic constitution of uranium, mainly from the work of 

 A. O. Nier [5], the disintegration rate and half-life of each of its three isotopes 

 can be determined, as shown in Table 35. 



Table 35. Disintegration Rates of the Naturally Occurring Uranium Isotopes 



