There is no separate pathway for radionuclides. Rather, there are special considerations that come into play within each of the four pathways when radioactive substances are present.
HRS Table 7.1 highlights where the differences are within the four pathways and the rest of Chapter 7 explains the differences.
If a site has both chemical and radioactive hazardous substances apply the HRS "as-is" for the chemical wastes and apply the special considerations in the evaluation of the radioactive wastes.
Examine HRS Table 7.1 carefully as the "roadmap" to special considerations.
Here is a brief summary of the differences:
- Observed releases are different because a more statistical
approach is taken for radionuclides. Different sampling technology
makes this possible.
- Toxicity, ecotoxicity, persistence, and mobility values are calculated
differently for radionuclides. All you have to remember is to use
SCDM for Radionuclides (SCDM)
- Where there are both radioactive and chemical substances,
the HRS provides that you use the highest value in selecting the most hazardous
substance for a pathway.
- Hazardous waste quantity is calculated for only tier A and
B, based on curies rather than pounds. If both radioactive and chemical
substances are present in a source, the HRS provides a conversion that allows
the two quantity values for the source to be added.
- Targets are different only in that radiological benchmarks
are used to establish Level I or Level II concentrations. These benchmarks
are in SCDM.
Even where there are differences in the treatment of radionuclides, those differences have been kept as parallel as possible to the HRS as you already know it.