![]() ![]() Finally, the sample was collected in a small glass coil filled with charcoal, and the activity was determined by measurement of the 81-keV gamma ray, characteristic of 133 Xe, using a HPGe detector. After a concentration process, quantification of stable xenon, as well as radon separation, were performed using preparative gas chromatography. This older method utilized adsorption of xenon on activated charcoal in a copper coil placed in a low temperature freezer. ![]() Continuous measurements of 133 Xe samples collected weekly using a partially automatic technique was performed for 10 years (1990–2000) at three places in Sweden. In Sweden, verification of a future CTBT has been the main motivation for the development of noble gas detection systems, and sampling and analysis of 133 Xe have been performed for more than 20 years. This verification system will provide world-wide monitoring for evidence of nuclear explosions and includes 321 monitoring stations and 16 radionuclide laboratories. Altogether, detection of radioxenon is an attractive tool for disclosing clandestine tests of nuclear weapons, and has been included in the verification regime for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). However, since the isotopic ratios ( 135 Xe / 133 Xe and 133m Xe / 133 Xe) in a nuclear reactor release are very different from that of a nuclear detonation, it is possible to discriminate between the two release types. When monitoring xenon gas releases from a subsurface nuclear detonation, the most important competing background is the fission gas release from nuclear power plants. ![]() Another very important reason is the chemical inertness of the noble gases which allows them to escape from underground nuclear explosions more easily than isotopes produced in solid form. This is one of the basic reasons why monitoring of radioactive noble gases in the atmosphere has been performed for decades (see, for some early examples). Most of these isotopes decay within seconds, but a few ( 133 Xe, 135 Xe, 131m Xe, and 133m Xe) have half-lives of several hours to several days (see Table 1), and are produced in amounts that can be detected at large distances from where they were emitted. About 20 radioactive isotopes of xenon are formed in fission of heavy elements like uranium or plutonium. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |