American National Standard N13.12

Surface and Volume Radioactivity Standards for Clearance

The need for comprehensive, clearance¹ criteria for items, equipment, and facilities contaminated with radioactive materials has been recognized for several decades. Initial attempts to develop this standard began in 1964 and were limited in scope to the consideration of surface contamination. Volume contamination, including radioactive contamination dispersed throughout the material, materials activated by neutrons, and contaminated soils were all beyond the scope of the initial efforts.

Over the last 10 or 15 years, an increasing trend has been to conduct an exposure pathway assessment supporting the development of new regulations or standards. Of particular note have been the efforts of the U.S. Nuclear Regulatory Commission (NRC) to develop revised decommissioning regulations, guidance from the National Council on Radiation Protection and Measurements (NCRP) on the development and application of screening models, and the International Atomic Energy Agency (IAEA) efforts to develop clearance (formerly exemption) criteria. The intent of these efforts is to more closely link secondary (derived) criteria with a primary dose (or risk) criterion.

This standard provides both the primary dose standard for clearance and derived screening levels, based on the dose standard. The purpose and scope of this standard are provided in Section 1.0 and basic definitions are provided in Section 2.0. Section 3.0 contains the basic dose criterion (in terms of the primary dose standard for clearance) and the derived screening levels (in terms of the activity per unit surface area or mass). Section 4.0 provides information useful in the implementation of this standard and covers a wide variety of topics including the role of process knowledge, instrument selection, surface versus volumetric measurements, summing radionuclide fractions, concentration averaging, removable contamination levels, measuring activities above natural background, representative sampling and testing, and quantitative versus qualitative measurement techniques. Section 5.0 describes records and Section 6.0 provides the references cited in this standard. A more complete discussion of the technical basis for the primary dose criterion and a discussion of as low as reasonably achievable (ALARA) considerations for clearance are found in Annex A. Details about the derivation of the screening levels, their relationship to the primary dose criterion, a comparison with other guidance and previous radiation dose estimates, and a comparison with instrumentation detection limits are provided in Annex B. Annex C contains normative and informative references supporting the information in Annex A and Annex B.

¹ Clearance is the removal of items or materials that may contain residual levels of radioactive materials within authorized practices from any further control of any kind. Clearance is distinct from authorized radioactive discharges. Clearance implies that the subject materials or objects were under regulatory control—exclusion and exemption do not. Exclusion is the designation by a regulatory authority that the magnitude or likelihood of an exposure is essentially unamenable to control through requirements of a standard and such exposures are outside the scope of standards, e.g., exposure from 40K in the body, from cosmic radiation at the surface of the earth and from unmodified concentrations of radionuclides in most raw materials. Exemption is the designation by a regulatory authority that specified uses of radioactive materials or sources of radiation are not subject to regulatory control because the radiation risks to individuals and the collective radiological impact are sufficiently low. [Sources: International Atomic Energy Agency(IAEA), Vienna; Principles for the Exemption of Radiation Sources and Practices from Regulatory Control, Safety Series No. 89 (IAEA 1988); and International Basic Safety for Protections against Ionizing Radiation and for the Safety of Radiation Sources, Safety Series No.115 (IAEA 1996a).]

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