Near-surface disposal

To facilitate near-surface disposal of nuclear wastes, efficient removal of the ty = 30 year fission product °Sr is desirable. The SREX process [60]... 

Waste that exceeds concentration limits for exempt waste would be classified as low-hazard if it poses no more than an acceptable (i.e., barely tolerable) risk to a hypothetical inadvertent intruder at a dedicated near-surface disposal facility for hazardous wastes, with the important condition that an acceptable risk or dose used to determine low-hazard waste should be substantially higher than a negligible risk or dose used to determine exempt waste. 

Near-surface disposal system or, for high-activity, longer-lived waste, geologic repository4... 

Near-surface disposal in situ or at processing site 6 small volumes may be managed as low-level waste... 

Most low-level waste, except high-activity, longer-lived waste that is anticipated to be produced in small volumes, is intended for disposal in a near-surface facility. The acceptability of near-surface disposal for most low-level waste is based primarily on assessments of the long-term performance of such facilities, which indicate that the health risks to the public, including future inadvertent intruders, should be acceptable. 

Thus, assessments of long-term health risks to the public, including future inadvertent intruders at near-surface disposal sites, are important in selecting disposal technologies for radioactive wastes... 

Near-surface disposal system or geologic repository11... 

Second, generic and site-specific assessments of near-surface disposal facilities for radioactive waste have shown that allowable doses to hypothetical inadvertent intruders usually are more restrictive in determining acceptable disposals than allowable doses to individuals beyond the boundary of the disposal site. This conclusion is based on predictions that concentrations of radionuclides in the environment (e.g., ground-water) at locations beyond the site boundary usually should be far less than the concentrations at the disposal site to which an inadvertent intruder could be exposed, owing to such factors as the limited solubility of some radionuclides, the partitioning of radionuclides between liquid and solid phases, and the dilution in transport of radionuclides in water or air beyond the site boundary. More people are likely to be exposed beyond the site boundary than on the disposal site, but acceptable disposals of radioactive waste in near-surface facilities have been based on assessments of dose to individuals, rather than populations. 

The recommendation that generic scenarios for exposure of hypothetical inadvertent intruders should be used in classifying waste is consistent with the approach used by NRC in 10 CFR Part 61 to establish different subclasses of low-level radioactive waste that are generally acceptable for near-surface disposal (Class-A, -B, and -C waste) or are generally unacceptable for near-surface disposal (greater-than-Class-C waste). Such scenarios have not been used to... 

The assumed disposal systems for exempt waste and low-hazard waste both involve near-surface disposal, and either type of waste often would be emplaced sufficiently close to the surface that inadvertent intrusion into the waste could occur as a result of normal human activities. However, there are differences in the two types of disposal systems that should be taken into account in developing appropriate scenarios for inadvertent intrusion. Disposal facilities for low-hazard waste frequently include engineered barriers to deter inadvertent intrusion, impenetrable waste forms, or deliberate emplacement of more hazardous wastes at locations where access to the waste during normal human activities would be less likely. Most importantly, as noted previously, current plans call for institutional control to be maintained over hazardous waste disposal sites for a considerable period of time after facility closure, which allows for substantial... 

In developing generic scenarios for inadvertent intrusion into near-surface disposal facilities used to determine limits on concentrations of hazardous substances in exempt and low-hazard waste, consideration must be given to the question of how far into the future the scenarios should be applied, as well as the earliest time at which the scenarios could occur. This issue arises because the potential risk posed by some radionuclides e.g., uranium) increases with time, due to the long-term buildup of radiologically significant decay products, and some hazardous chemicals could be transformed over time into more hazardous forms. NCRP believes that scenarios for inadvertent intrusion used to classify waste should be applied over a time period consistent with the time period for applying standards for protection of members of the public beyond the boundaries of waste disposal sites. 

DOE s high-level wastes as if they were among the most hazardous of all radioactive wastes. However, the concentrations of hazardous substances in some of these wastes are similar to those in low-level radioactive waste that is normally intended for disposal in near-surface facilities. In contrast, some chemical wastes that are highly hazardous, compared with other wastes, and nondegradable are being sent to near-surface disposal facilities. Both of these situations occur largely because of the source-based aspects of existing waste classification systems. 

Low-level waste Any waste not classified as spent fuel, high-level waste, transuranic waste, or uranium or thorium mill tailings Near-surface disposal system or, for high-activity, longer-lived waste, geologic repositoryf... 

Mill tailings Residues from chemical processing of ores for their source material (i.e., uranium or thorium) content Near-surface disposal in situ or at processing site 8 small volumes may be managed as low-level waste... 

Waste Isolation Pilot Plant (WIPP) in New Mexico is only disposal facility authorized in law commercial transuranic waste also may be acceptable for near-surface disposal on a case-by-case basis. 

NRC has developed licensing criteria for near-surface disposal of waste that contains source, special nuclear, or byproduct materials in 10 CFR Part 61 (NRC, 1982a). These regulations are intended to apply primarily to disposal of commercial low-level waste. They do not include a definition of low-level waste but essentially defer to the current statutory definition in the Low-Level Radioactive Waste Policy Amendments Act of 1985. Thus, low-level waste can include wastes with high concentrations of radionuclides that are not generally acceptable for near-surface disposal in accordance with the licensing criteria in 10 CFR Part 61 (NRC, 1982a). 

Current DOE policy also permits near-surface disposal of most of its low-level waste (DOE, 1988c 1999c). Disposal of DOE s low-level waste is not licensed by NRC, unless the waste is sent to a licensed... 

Requires permanent isolation means concentrations of radionuclides greater than those that would be generally acceptable for near-surface disposal. 

The concentration limits for near-surface disposal either are the Class-C limits specified in NRC s 10 CFR Part 61 (NRC, 1982a) and discussed in Section 4.1.2.3.3 or, for other radionuclides, are the Class-C limits calculated using NRC s risk analysis methodology for near-surface disposal (Oztunali and Roles, 1986 Oztunali et al., 1986). 

Short-lived wastea Concentrations of long-lived, alpha-emitting radionuclides restricted to 4 kBq g"1 in individual waste packages and average of 0.4 kBq g"1 over all waste packages Near-surface disposal system or geologic repositoryb... 

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