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Transuranic waste (TRU) is, as stated by U.S. regulations and independent of state or origin, waste which has been contaminated with alpha emitting transuranic radionuclides possessing half-lives greater than 20 years and in concentrations greater than 100 nCi/g (3.7 MBq/kg).
Elements having atomic numbers greater than that of uranium are called transuranic. Elements within TRU are typically man-made and are known to contain americium-241 and several isotopes of plutonium. Because of the elements' longer half-lives, TRU is disposed of more cautiously than low level waste and intermediate level waste. In the U.S. it is a byproduct of weapons production, nuclear research and power production, and consists of protective gear, tools, residue, debris and other items contaminated with small amounts of radioactive elements (mainly plutonium).
Under U.S. law, TRU is further categorized into "contact-handled" (CH) and "remote-handled" (RH) on the basis of the radiation field measured on the waste container's surface. CH TRU has a surface dose rate not greater than 2 mSv per hour (200 mrem/h), whereas RH TRU has rates of 2 mSv/h or higher. CH TRU has neither the high radioactivity of high level waste, nor its high heat generation. In contrast, RH TRU can be highly radioactive, with surface dose rates up to 10 Sv/h (1000 rem/h).
The United States currently permanently disposes of TRU generated from defense nuclear activities at the Waste Isolation Pilot Plant, a deep geologic repository.
Other countries do not include this category, favoring variations of High, Medium/Intermediate, and Low Level waste.
Chemical elements contains 11 transuranic actinide elements, with atomic numbers ranging from 93 to 103. An element is defined by its atomic number, the number of protons in the atomic nucleus. Nuclei with the same atomic number but different numbers of neutrons are isotopes of the same element. The number of possible isotopes that have been attested in the laboratory is listed in the table shown for each element. The mass number of an isotope is the total number of protons and neutrons. All of the transuranic actinides are unstable. For any element, the most stable isotope is the one with the longest half-life, or time until half of the original amount present decays. The possible decay modes of the most stable isotope include Alpha particle emission, which drops the atomic number by 2 and the mass number by 4; Spontaneous Fission (SF), in which the nucleus breaks into several fragments; Beta particle emission, which increases the atomic number by 1 but leaves the mass number unchanged; and Electron Capture (EC), which decreases the atomic number by 1 but leaves the mass number unchanged.
- "THE WASTE ISOLATION PILOT PLANT LAND WITHDRAWAL ACT as amended by Public Law 104-201 (H.R. 3230, 104th Congress)". New Mexico Radioactive Waste Consultation Task Force WIPP Transportation Safety Task Force. Retrieved 2011-03-21.
- Department of Energy Carlsbad Field Office (Jun 2002). "Chapter 1, "Introduction and Statement of Purpose and Need"". Final Environmental Assessment for Actinide Chemistry and Repository Science Laboratory. DOE/EA-1404 (PDF). US Department of Energy. Retrieved 2011-03-21.