Low-level waste

Commercial and government facilities exist for LLW processing, including treatment, conditioning, and disposal. Generators prepare LLW for ship­ment to licensed disposal facilities. Commercial LLW disposal facilities are designed, constructed, and operated under licenses issued by either the NRC or an Agreement State, based on NRC health and safety regulations governing waste disposal quantities, forms, and activity levels. The DOE operates disposal facilities for LLW that it owns or generates and uses com­mercial LLW disposal sites in certain circumstances.

LLW is disposed of in near-surface facilities, i. e. a land disposal facility in which radioactive waste is disposed of in or within the upper 30 m of the Earth’s surface. Currently, commercial generators of Class B and C wastes in 36 states do not have access to a disposal site for these wastes, which are being stored pending a disposal pathway.

Greater-than-class C LLW

Greater-than-class C (GTCC) LLW waste is a form of LLW containing long — and short-lived radionuclides with properties requiring a more robust disposal strategy than for other classes of LLW. In the context of this chapter, ‘more robust’ means a greater degree of isolation, durability, and performance than is associated with near-surface disposal for other classes of LLW. This could include intermediate-level waste, as defined by some nations. The authority to possess this type of radioactive material is included in NRC or Agreement State licenses.

GTCC LLW may generally be grouped into the following three types: sealed sources, activated metals, and other waste. Other GTCC LLW includes contaminated equipment, trash, and scrap metal from miscellane­ous industrial activities, such as manufacturing of sealed sources and laboratory research. Most GTCC LLW is activated metal, generated by decommissioning NPPs, and disused sealed sources. Although the US inven­tory of GTCC LLW is modest, the construction of new commercial reactors and other proposed actions could generate additional quantities of GTCC LLW. GTCC LLW is stored until an adequate method of disposal is estab­lished by the DOE.

Radioactive wastes are treated primarily to produce a structurally stable, final waste form and minimize the release of radioactive and hazard­ous components. The United States does not commonly make a distinction between the terms ‘treatment’ and ‘conditioning.’ Conditioning is defined in the international community as an operation producing a waste form suitable for handling, such as conversion of a liquid to a solid, enclosure of the waste in containers, or overpacking. Treatment is defined as those opera­tions intended to improve the safety and/or economy by changing the characteristics of the waste through volume reduction, removal of radionu­clides, and change in composition. US terminology covering both condition­ing and treatment is generally referred to as treatment or processing. Treatment is used in this broader context in this chapter.

18.1.5 High-level waste

HLW from commercial reprocessing activities has been vitrified and is stored at the former reprocessing plant in West Valley, New York. Defense HLW is stored, managed, and treated at three DOE sites: Savannah River Site (SRS) in South Carolina, Hanford Site in Washington, and Idaho National Laboratory (INL) in Idaho.

The NWPA of 1982 established the federal responsibility for the disposal of SNF and HLW. The NWPA assigned responsibilities for the disposal of SNF and HLW to three federal agencies:

1. DOE for developing permanent disposal capability for SNF and HLW

2. EPA for developing generally applicable environmental protection standards

3. NRC for developing regulations to implement EPA standards; deciding whether to license construction, operation, decommissioning, and closure of the repositories; and certifying packages used to transport SNF and HLW to the licensed repositories.

The NWPA, as amended in 1987 (Nuclear Waste Policy Amendments Act), directed the DOE to characterize a site at Yucca Mountain, Nevada, for its potential use as a deep geological repository. The geology at Yucca Moun­tain is a welded volcanic tuff and the climate is arid desert. (Other sites in salt and basalt had previously been under consideration.) However, in 2009, the Obama Administration decided that Yucca Mountain was no longer an option to be considered (see Section 18.6).

Spent fuel storage

The United States produces SNF in commercial NPPs and research reac­tors. Currently, 104 licensed nuclear power reactors provide about 20% of US electricity. Information on US nuclear power reactors is provided in the Convention on Nuclear Safety US National Report (IAEA, 2012).

All operating nuclear power reactors are storing SNF in NRC-licensed, onsite SNF pools, and over half are storing SNF in NRC-licensed independ­ent spent fuel storage installations (ISFSIs) located onsite. Given the cir­cumstances regarding reconsideration of the US strategy for underground geologic disposal of SNF and HLW and the work performed by the Blue Ribbon Commission (BRC) on America’s Nuclear Future (see Section 18.6), the current US approach to SNF management will continue. SNF will remain in onsite storage at the NPP where it was generated in spent fuel pools or at ISFSIs until a national long-term strategy is decided.

Most NPPs that have been decommissioned or are undergoing decom­missioning also have SNF stored onsite pending disposal. Most permanently shut-down commercial nuclear power reactors currently have, or are plan­ning to have, their SNF stored at onsite ISFSIs. NRC amended its regula­tions in 1990 to allow licensees to store SNF in NRC-certified dry storage casks at licensed power reactor sites. Dry storage systems were developed as the preferred alternative (versus new pool construction). Most SNF is loaded in canisters with inert gas and welded closed. The canisters are then placed in storage casks or vaults/bunkers. Some cask designs can be used for both storage and transportation.

There are two primary canister-based, dry-cask storage systems for SNF in the United States (NRC, 2012a). One design involves placing canisters vertically or horizontally in a concrete vault used for radiation shielding and protection of the canister. The other design places canisters vertically on a concrete pad and uses both metal and concrete storage overpacks for radiation shielding and canister protection (NRC, 2012b).

Table 18.4 summarizes the types and numbers of US SNF storage facili­ties. Complete lists of these facilities of SNF storage facilities are provided in the annex of the United States Fourth National Report for the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management (the complete document can be found at: http://www. em. doe. gov/pdfs/4th_US%20_Nat%20_Report%20%2009-21 -11.pdf). Fig. 18.2 shows the location of independent SNF storage installa­tions and other SNF storage facilities.

Recently, the NRC has renewed the licenses for several ISFSIs for a 40-year term, extending the total storage duration authorized by NRC for

60 years. The NRC determined that the licensees’ aging management plans along with their surveillance activities were sufficient to ensure that the SNF can be safely stored and retrieved at the end of the 60-year storage period (NUREG, 2011).

SNF results from the once-through fuel cycle (i. e., no further processing conducted). It contains greater than 99% of the radioactivity and has unique characteristics compared to wastes from fossil plants. Because only about 5% of the energy value has been consumed in the reactor, it can also rep­resent a future energy resource. The energy release from nuclear fission per ton of fuel is about a million times greater than the energy release from the burning of fossil fuels. The waste volume generated is about a million times less. The quantity of SNF is small per unit of energy produced. The small quantity (-20 tons per reactor per year) makes multiple waste management options economically feasible: multiple direct disposal options and multiple options to process the SNF chemically for recovery of selected materials for recycle and/or conversion into different waste forms.

Reactors discharge SNF that contains fissile materials (fuel) and fission products (waste). The radioactivity and decay heat of SNF decreases rapidly with time; thus, to reduce handling risks and costs, SNF is stored before transport, disposal, or recycling. SNF storage is a required step in all open and closed fuel cycles. This is a consequence of the nuclear characteristics of SNF. The radioactivity decreases rapidly with time, resulting in radioac­tive decay heat and gamma radiation decreasing rapidly with time. There are large safety and economic incentives to allow the radioactivity of SNF to decrease before transport, processing, or disposal.

Upon reactor shutdown, SNF is intensely radioactive and generates large quantities of decay heat — equal to about 6% of the power output of the reactor. However, the radioactive decay heat decreases very rapidly reach­ing 0.5% in one week. The refueling strategy in light water reactors (LWRs) is to transfer the SNF from the reactor core to the SNF storage pool where the water provides cooling and radiation shielding. After about ten years, the radioactivity will decrease by another factor of 100.

If SNF is to be disposed of in a repository, it will likely be stored for approximately 40-60 years prior to disposal. Peak temperatures in a geo­logical repository are limited to ensure long-term repository performance. If the temperatures are too high, the performance of the waste form, waste package, and geology may be impaired. Peak repository temperatures would be controlled by limiting the allowable decay heat per waste package. If the SNF is stored for several decades, several advantages would result: the decay heat per ton of SNF decreases; more SNF can be placed in each waste package; the waste packages can be spaced closer to each other underground; the size (footprint) of the repository is reduced; and the cost of the repository is reduced. Like SNF, the HLW will be cooled for 40-60 years before ultimate disposal to reduce the decay heat.

Radioactive wastes in the United States have many designations depending on their hazards and the circumstances and processes that created them. The NRC regulates most, but not all, sources of radioactivity, including LLW and HLW disposal, and residues from the milling of uranium and thorium. Uranium mill tailings, the final byproduct of uranium ore extrac­tion, are considered radioactive wastes. Radioactivity can range from just above background to very high levels, such as parts from inside the reactor vessel in a NPP. The everyday waste products generated in medical labora­tories and hospitals, contaminated by medical radioisotopes, is also desig­nated as RAW.

Tables 18.2 and 18.3 identify the types of commercial and DOE radioac­tive wastes. NRC regulations classify LLW in the commercial sector as Class A, Class B, and Class C. Radioactive waste owned or generated by the DOE is classified as HLW, TRU waste, or LLW. In addition, the DOE manages large quantities of uranium mill tailings and residual radioactive material. This residual radioactive material, which resulted from the Manhattan Project, is managed under the Uranium Mill Tailings and Radiation Control Act (UMTRCA) Title I. Waste may also contain hazardous waste constitu­ents. Waste with both radioactive and hazardous constituents in the United States is called ‘mixed’ waste (mixed LLW or mixed TRU waste). Generally, the source of HLW is reprocessed SNF. TRU waste consists of items such as protective clothing, tools, glassware, equipment, soils, and sludge con­taminated with man-made radioisotopes beyond or ‘heavier’ than uranium in the periodic table of the elements.

a From the Nuclear Waste Policy Act of 1982, as amended. b Title 10 CFR Part 40, Domestic Licensing of Source Material (Section 40.4).

18.1.4 Spent fuel and RAW classification

The US classification system has two separate subsystems: one applies to commercial waste, and NRC regulations define it; the other applies to DOE

SNF and waste. The two systems are used for different purposes and differ­ent situations so conflicts do not occur. If ownership of radioactive waste is transferred from the DOE to a commercial entity licensed by the NRC, the waste is then subject to NRC regulation (and classification).

Spent fuel

The United States defines ‘SNF’ as fuel that has been withdrawn from a nuclear reactor following irradiation, the constituent elements of which have not been separated by reprocessing. US law generally uses the term ‘SNF’ rather than ‘spent fuel,’ and the DOE has begun using the term ‘used fuel’ to acknowledge that in the future, the material may have residual value through recycling. For the purposes of this chapter, used fuel is referred to as SNF in accordance with the conventional terminology unless otherwise noted.

The AEA, as amended, provides a statutory basis for the NRC to relinquish to individual states portions of its authority to license and regulate byprod­uct materials (radioisotopes), source materials (uranium and thorium), and certain quantities of special nuclear materials. Of the 50 states, 37 have entered into agreements with the NRC to assume this responsibility.

The role of the Agreement States is to regulate most types of radioactive material in accordance with the compatibility requirements of the AEA. These types of radioactive materials include source material (uranium and thorium), reactor fission byproducts, and byproduct materials as defined in Section 11 e of the AEA, and quantities of special nuclear materials not sufficient to form a critical mass. The NRC, under its own internal practices, periodically reviews the performance of each Agreement State to ensure compatibility with its regulatory standards.

Agreement States issue radioactive material licenses, promulgate regula­tions, and enforce those regulations under the authority of each individual state’s laws. The Agreement States conduct their licensing and enforcement actions under direction of the governors in a manner compatible with the licensing and enforcement programs of the NRC.

The EPA delegates authorities to states in two areas of RAW management. NESHAPs regulations are based on the requirements of the Clean Air Act, and the authority for delegating compliance responsibility to the individual states is described by law. A state must have emission limits at least as stringent as the federal EPA national standards, although most states have not asked for delegation responsibility of radionuclide NESHAPs. The EPA has a similar process for delegating RCRA hazardous waste requirements to states. The state must have a program at least as stringent as the federal program, and the application for authorization must address specific areas of compatibility. For example, the State of New Mexico is authorized by the

EPA to carry out the base RCRA and mixed waste programs in lieu of equivalent federal programs. The New Mexico Environment Department reviews permit applications for treatment, storage, and disposal facilities for hazardous waste under Subtitle C of RCRA. The WIPP Hazardous Waste Facility Permit is renewed every ten years.

States authorized by the EPA play a significant role in regulation and independent oversight of DOE facilities. Most of the DOE ’s cleanup is performed under the Comprehensive Environmental Response, Compen­sation, and Liability Act (CERCLA) through Federal Facility Agreements and under RCRA through various consent and compliance orders. These enforceable regulatory agreements and orders with federal and state agen­cies establish the scope of work to be performed at a given site and the dates by which specific cleanup milestones must be achieved. Failure to comply with these agreements and orders is subject to fines and penalties.

State regulatory authorities

Provisions of law allow federal agencies to delegate or relinquish certain regulatory responsibilities to the states having radioactive materials or nuclear facilities. NPPs are regulated by federal authorities. Regional arrangements allow closer coordination, such as using radioisotopes for medical uses. These arrangements are not necessarily mandatory; however, where the state can demonstrate adequate competencies, the appropriate federal agency can transfer regulatory authority.