Editing Radioactive waste (section)

=== Physics ===
{{Main article|Fission product yield}}
{{See also|Radioactive decay}}
{{Medium-lived fission products}}
{{Long-lived fission products}}
The radioactivity of all radioactive waste weakens with time. All [[radionuclide]]s contained in the waste have a [[half-life]]—the time it takes for half of the atoms to decay into another [[nuclide]]. Eventually, all radioactive waste decays into non-radioactive elements (i.e., [[stable nuclide]]s). Since radioactive decay follows the half-life rule, the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like [[iodine-129]] will be much less intense than that of a short-lived isotope like [[iodine-131]].<ref>{{cite web |date=28 March 2011 |title=What about Iodine-129 – Half-Life is 15 Million Years |url=http://www.nuc.berkeley.edu/node/2115 |url-status=dead |archive-url=https://web.archive.org/web/20130513121013/http://www.nuc.berkeley.edu/node/2115 |archive-date=13 May 2013 |access-date=1 December 2012 |work=Berkeley Radiological Air and Water Monitoring Forum |publisher=University of California |language=en-us |publication-place=Berkeley, California}}</ref> The two tables show some of the major radioisotopes, their half-lives, and their [[fission product yield|radiation yield]] as a proportion of the yield of fission of uranium-235.

The energy and the type of the [[ionizing radiation]] emitted by a radioactive substance are also important factors in determining its threat to humans.<ref>{{cite book |title=Introduction to Radiological Physics and Radiation Dosimetry |last=Attix |first=Frank |year=1986 |publisher=Wiley-VCH |location=New York |isbn=978-0-471-01146-0 |pages=2–15,468,474 |url=https://books.google.com/books?id=PL8971RdEfoC}}</ref> The chemical properties of the radioactive [[chemical element|element]] will determine how mobile the substance is and how likely it is to spread into the environment and [[contaminate]] humans.<ref>{{cite book |last=Anderson |first=Mary |author-link=Mary P. Anderson |title=Applied Groundwater Modeling |author2=Woessner |first2=William |publisher=Academic Press Incorporated |year=1992 |isbn=0-12-059485-4 |location=San Diego, California |pages=325–327 |language=en-us}}</ref> This is further complicated by the fact that many radioisotopes do not decay immediately to a stable state but rather to radioactive [[decay product]]s within a [[decay chain]] before ultimately reaching a stable state.