Radioactive Waste Management/Low Level Radioactive Waste
Low-Level Waste (LLW) in the United States is a term used to describe nuclear waste that does not fit into the categorical definitions for high-level waste (HLW), spent nuclear fuel (SNF), transuranic waste (TRU), or certain byproduct materials known as 11e(2) wastes, such as uranium mill tailings. In essence, it is a definition by exclusion, and LLW is that category of radioactive wastes that do not fit into the other categories. If LLW is mixed with hazardous wastes, then it has a special status as Mixed Low-Level Waste (MLLW) and must satisfy treatment, storage, and disposal regulations both as LLW and as hazardous waste. While the bulk of LLW is not highly radioactive, the definition of LLW does not include references to its activity, and some LLW may be quite radioactive, as in the case of radioactive sources used in industry and medicine.
The definition of low level waste is set by the nuclear regulators of individual countries, though the IAEA provides recommendations. Some countries, such as France, specify categories for long-lived low (and intermediate) level waste.
Disposal
[edit | edit source]Depending on who "owns" the waste, its handling and disposal is regulated differently. All nuclear facilities, whether they are a utility or a disposal site, have to comply with NRC regulations. The three low-level waste facilities in the U.S. are Barnwell, South Carolina, Richland, Washington, and Clive, Utah. The Barnwell and the Clive locations are operated by EnergySolutions, whereas the Richland location is operated by U.S. Ecology. Barnwell and Richland accept Classes A through C of low-level waste, whereas Clive only accepts Class A LLW. The DOE has dozens of LLW sites under management. The largest of these exist at DOE Reservations around the country (e.g. the Hanford Site|Hanford Reservation, Savannah River Site, Nevada Test Site, Los Alamos National Laboratory, Oak Ridge National Laboratory, Idaho National Laboratory, to name the most significant).
Classes of US Low Level wastes are detailed in 10 C.F.R. § 61.55 Waste Classification enforced by the Nuclear Regulatory Commission, reproduced in the table below. These are not all the isotopes disposed of at these facilities, just the ones that are of most concern for the long-term monitoring of the sites. Waste is divided into four classes, A through C, and greater than class C where A is the least radioactive and C is the most radioactive. Class A LLW is able to be deposited near the surface, whereas Classes B and C LLW have to be buried progressively deeper. There currently is no place to dispose of greater than class C waste. It has been proposed that the same location of spent nuclear fuel could potentially handle low lever waste. However, throughout the world there currently is not a licensed location for spent nuclear fuel disposal.
In 10 C.F.R. § 20.2002, the NRC reserves the right to grant a free release of radioactive waste. The overall activity of such a disposal cannot exceed 1 mrem/yr and the NRC regards requests on a case-by-case basis. Low-level waste passing such strict regulations is then disposed of in a landfill with other garbage. Items allowed to be disposed of in this way are: glow-in-the-dark watches (radium) and smoke detectors (americium) among other things.
| Radionuclide | Class A (Ci/m^3) | Class B (Ci/m^3) | Class C (Ci/m^3) |
|---|---|---|---|
| Total of all nuclides with less than 5 year half life | 700 | No limit | No limit |
| H-3 (Tritium) | 40 | No limit | No limit |
| Co-60 | 700 | No limit | No limit |
| Ni-63 | 3.5 | 70 | 700 |
| Ni-63 in activated metal | 35 | 700 | 7000 |
| Sr-90 | 0.04 | 150 | 7000 |
| Cs-137 | 1 | 44 | 4600 |
| C-14 | 0.8 | 8 | |
| C-14 in activated metal | 8 | 80 | |
| Ni-59 in activated metal | 22 | 220 | |
| Nb-94 in activated metal | 0.02 | 0.2 | |
| Tc-99 | 0.3 | 3 | |
| I-129 | 0.008 | 0.08 | |
| Alpha emitting transuranic nuclides with half life greater than 5 years | 10 nCi/g | 100 nCi/g | |
| Pu-241 | 350 nCi/g | 3500 nCi/g | |
| Cm-242 | 2000 nCi/g | 20000 nCi/g |
LLW should not be confused with high-level waste (HLW), spent nuclear fuel (SNF) or transuranic waste (TRU). These require different disposal pathways. TRU wastes from the US nuclear weapons complex is currently disposed at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico, though other sites are considering on-site disposal of particularly difficult to manage TRU wastes.