Document: NRC Regulatory Guide
Document ID: 05969442-49ea-4f4a-a9e2-de3a14628b5e
Document Type: regulatory_guide
Title: Minimization of Contamination and Radioactive Waste Generation:  Life-Cycle Planning - HISTORY 07/2013 – Periodic Review of Revision 0 – No issues identified
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML0805/ML080500187.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.21
CFR Part: 
CFR Title: 

Content:
Release of Contamination from Undetected Leaks Past experience has shown that leaks of radioactive material from SSCs containing radiation can go undetected over long periods of time if these SSCs are not readily accessible for surveillance or when the amount of leaking material is below the sensitivity of the survey instrument. Under these conditions, 1 Unless already defined in an application or licensing basis document, radiologically significant generally refers to the presence of radioactive materials at levels which could result in radiation exposures and doses in excess of the 10 CFR Part 20 requirements for radiation workers and members of the public, or in excess of liquid and airborne effluent concentration limits and releases to sewers under Appendix B to Part 20. RG 4.21, Page 7 contamination from undetected leaks can accumulate as subsurface residual radioactivity that may require remediation prior to license termination. This contamination generally occurs as minor leaks over an extended period of time. SSCs that are buried, embedded in concrete, or in contact with soil (such as spent fuel pools, underground tanks, and buried pipes) are particularly susceptible to undetected leakage. Facilities undergoing decommissioning commonly discover previously undetected contamination in the subsurface environment. These releases were generally minor leaks that occurred over an extended period of time. Many of the leaks occurred in areas where it was difficult or impossible to conduct regular inspections. This likely contributed to the failure to identify the leaks at the time of occurrence. Monitoring of some SSCs was not sufficiently sensitive to identify small leaks and leakage rates. Such situations and conditions should be avoided during facility design. Leak detection systems should be included within the facility design that are capable, to the extent practical, of detecting minor leaks that otherwise, over time, could potentially cause significant