World Library  
Flag as Inappropriate
Email this Article

Minor actinide

Article Id: WHEBN0003096890
Reproduction Date:

Title: Minor actinide  
Author: World Heritage Encyclopedia
Language: English
Subject: Nuclear fuel, Radioactive waste, Integrated Nuclear Fuel Cycle Information System, Plutonium-238, Post Irradiation Examination
Publisher: World Heritage Encyclopedia

Minor actinide

Transmutation flow between 238Pu and 244Cm in LWR.[1]
Fission percentage is 100 minus shown percentages.
Total rate of transmutation varies greatly by nuclide.
245Cm–248Cm are long-lived with negligible decay.

The minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium, americium, curium, berkelium, californium, einsteinium, and fermium.[2] The most important isotopes in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252.

Plutonium and the minor actinides will be responsible for the bulk of the radiotoxicity and heat generation of used nuclear fuel in the medium term (300 to 20,000 years in the future).[3]

The plutonium from a power reactor tends to have a greater amount of Pu-241 than the plutonium generated by the lower burnup operations designed to create weapons-grade plutonium. Because the reactor-grade plutonium contains so much Pu-241 the presence of americium-241 makes the plutonium less suitable for making a nuclear weapon. The ingrowth of americium in plutonium is one of the methods for identifying the origin of an unknown sample of plutonium and the time since it was last separated chemically from the americium.

Americium is commonly used in industry as both an alpha particle and low photon energy gamma radiation source. For instance it is used in many smoke detectors. Americium can be formed by neutron capture of Pu-239 and Pu-240 forming Pu-241 which then decays by beta decay to Am-241.[4] In general, as the energy of the neutrons increases, the ratio of the fission cross section to the neutron capture cross section changes in favour of fission. Hence if MOX is used in a thermal reactor such as a boiling water reactor (BWR) or pressurized water reactor (PWR) then more americium can be expected in the used fuel than that from a fast neutron reactor.[5]

Some of them have been found in fallout from bomb tests. See Actinides in the environment for details of the actinides in the environment.

Transuranics in LWR spent fuel (burnup 55 GWdth/T) and mean neutron consumption to fission[6]
Isotope Fraction DLWR Dfast Dsuperthermal
Np-237 0.0539 1.12 -0.59 -0.46
Pu-238 0.0364 0.17 -1.36 -0.13
Pu-239 0.451 -0.67 -1.46 -1.07
Pu-240 0.206 0.44 -0.96 0.14
Pu-241 0.121 -0.56 -1.24 -0.86
Pu-242 0.0813 1.76 -0.44 1.12
Am-241 0.0242 1.12 -0.62 -0.54
Am-242m 0.000088 0.15 -1.36 -1.53
Am-243 0.0179 0.82 -0.60 0.21
Cm-243 0.00011 -1.90 -2.13 -1.63
Cm-244 0.00765 -0.15 -1.39 -0.48
Cm-245 0.000638 -1.48 -2.51 -1.37
Weighted sum -0.03 -1.16 -0.51
Negative numbers mean net neutron producer


  1. ^
  2. ^
  3. ^
  4. ^
  5. ^
  6. ^
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Hawaii eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.