Document: NRC Regulatory Guide
Document ID: 96baa826-d3bb-478b-8f38-e74500f6d433
Document Type: regulatory_guide
Title: 06/2009 (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0911/ML091170109.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.21
CFR Part: 
CFR Title: 

Content:
a risk-informed perspective, a radionuclide is considered a principal radionuclide if it contributes either (1) greater than 1 percent of the 10 CFR Part 50, Appendix I, design objective dose for all radionuclides in the type of effluent being considered, or (2) greater than 1 percent of the activity of all radionuclides in the type of effluent being considered. Regulatory Guide 1.109 lists the three types of effluent as (1) liquid effluents, (2) noble gases released to the atmosphere, and (3) all other radionuclides released to the atmosphere. In this context, the term “principal radionuclide” has special significance with respect to the required sensitivity levels (e.g., LLDs) for an analysis. The LLDs specified in NUREG- 1301/1302 may be used, or LLDs may be determined based on the other methodologies (e.g., as outlined in MARLAP). Once principal radionuclides are identified, they should be monitored in accordance with the sensitivity levels (e.g., LLDs) listed in the ODCM. For radionuclides that are not identified as principal radionuclides, licensee discretion may be applied to the sensitivity of analysis provided that there is no reduction in the effectiveness of the radioactive effluent control program. If analytical sensitivities are chosen that are different from those in NUREG-1301 and NUREG-1302, the basis for the deviations should be documented. For example, data quality objectives (DQOs) and other concepts from Regulatory Guide 4.15, “Quality Assurance for Radiological Monitoring Programs (Inception through Normal Operations to License Terminations)— Effluent Streams and the Environment,” Revision 2, issued July 2007 (Ref. 20), may be useful for determining risk-informed sensitivity levels for an analytical method. If a risk-informed approach is used, principal radionuclides should be determined based on an evaluation over a time period that includes a refueling outage (e.g., one fuel cycle). A periodic reevaluation should be performed to