Transuranic waste
Encyclopedia
Transuranic waste is, as stated by U.S. regulations and independent of state or origin, waste which has been contaminated with alpha emitting
Alpha decay
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...

 transuranic radionuclides possessing half-lives greater than 20 years and in concentrations greater than 100 nCi
Curie
The curie is a unit of radioactivity, defined asThis is roughly the activity of 1 gram of the radium isotope 226Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie, for whom the unit was named. In addition to the curie, activity can be measured using an SI derived unit,...

/g (3.7 MBq
Becquerel
The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...

/kg).

Elements having atomic numbers greater than that of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

 are called transuranic. Elements within TRU are typically man-made, and are known to contain americium-241 and several isotopes of plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...

. Because of the elements' longer half-lives, TRU is disposed of more cautiously than low level waste
Low level waste
Low-Level Waste is a term used to describe nuclear waste that does not fit into the categorical definitions for high-level waste , spent nuclear fuel , transuranic waste , or certain byproduct materials known as 11e wastes, such as uranium mill tailings...

 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
MSV
mSv or MSV may refer to:*Medium Speed Vehicle, an administrative classification in certain jurisdictions for a 35MPH version of the NEV...

 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
Waste Isolation Pilot Plant
The Waste Isolation Pilot Plant, or WIPP, is the world's third deep geological repository licensed to permanently dispose of transuranic radioactive waste for 10,000 years that is left from the research and production of nuclear weapons...

, a deep geologic repository.

Other countries do not include this category, favoring variations of High, Medium/Intermediate, and Low Level waste.

External links

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