Radioactive Waste Management/Low Level waste

From Wikibooks, open books for an open world
Jump to navigation Jump to search
NRC Graphic of a Low-Level Waste Facility.

Low-Level Waste (LLW) 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.

Low-level waste includes items that have become contaminated with radioactive material or have become radioactive through exposure to neutron radiation. This waste typically consists of contaminated protective shoe covers and clothing, wiping rags, mops, filters, reactor water treatment residues, equipments and tools, luminous dials, medical tubes, swabs, injection needles, syringes, and laboratory animal carcasses and tissues. The radioactivity can range from just above background levels found in nature to very highly radioactive in certain cases such as parts from inside the reactor vessel in a nuclear power plant. Low-level waste is typically stored on-site by licensees, either until it has decayed away and can be disposed of as ordinary trash, or until amounts are large enough for shipment to a low-level waste disposal site in containers approved by the Department of Transportation.

The definition of low level waste is set by the nuclear regulators of individual countries, though the IAEA provides recommendations.

In the United States low-level waste disposal occurs at commercially operated low-level waste disposal facilities that must be licensed by either NRC or Agreement States. The facilities must be designed, constructed, and operated to meet safety standards. The operator of the facility must also extensively characterize the site on which the facility is located and analyze how the facility will perform for thousands of years into the future.

There are three existing low-level waste disposal facilities in the United States that accept various types of low-level waste. All are in Agreement States.

The Low-level Radioactive Waste Policy Amendments Act of 1985 gave the states responsibility for the disposal of their low-level radioactive waste. The Act encouraged the states to enter into compacts that would allow them to dispose of waste at a common disposal facility. Most states have entered into compacts; however, no new disposal facilities have been built since the Act was passed.

USA Agreement States[edit | edit source]

NRC provides assistance to States expressing interest in establishing programs to assume NRC regulatory authority under the Atomic Energy Act of 1954, as amended. Section 274 of the Act provides a statutory basis under which NRC relinquishes to the States portions of its regulatory authority to license and regulate byproduct materials (radioisotopes); source materials (uranium and thorium); and certain quantities of special nuclear materials. The mechanism for the transfer of NRC’s authority to a State is an agreement signed by the Governor of the State and the Chairman of the Commission, in accordance with section 274b of the Act.

NRC assistance to States entering into Agreements includes review of requests from States for 274b Agreements, or amendments to existing agreements, meetings with States to discuss and resolve NRC review comments, and recommendations for Commission approval of proposed 274b agreements. Additionally, NRC conducts training courses and workshops; evaluates technical licensing and inspection issues from Agreement States; evaluates State rule changes; participates in activities conducted by the Conference of Radiation Control Program Directors, Inc.; and provides early and substantive involvement of the States in NRC rulemaking and other regulatory efforts. The NRC also coordinates with Agreement States the reporting of event information and responses to allegations reported to NRC involving Agreement States.

On March 26, 1962, the Commonwealth of Kentucky became the first Agreement State. In December 1964, the U.S. Atomic Energy Commission hosted the first annual joint meeting with a group of these States. Today, 37 States have entered into Agreements with NRC, and others are being evaluated.

NRC and the Agreement States regulate low-level waste disposal through a combination of regulatory requirements, licensing, and safety oversight.

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 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 three classes, A through 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.

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.