United States Nuclear Regulatory Commission - Protecting People and the Environment

ISCORS Assessment of Radioactivity in Sewage Sludge: Modeling to Assess Radiation Doses (NUREG-1783, EPA 832-R-03-002A, DOE/EH-0670, ISCORS Technical Report 2004-03)

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Publication Information

Date Published: February 2005

Developed by:
The Sewage Sludge Subcommittee on Radiation Standards
Interagency Steering Committee on Radiation Standards (ISCORS)

U.S. Department of Energy

U.S. Environmental Protection Agency

State of New Jersey Department of Environmental Protection

Middlesex County Utilities Authority

Northeast Ohio Regional Sewer District

Division of Waste Management and Environmental Protection
Office of Nuclear Material Safety and Safeguards
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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The treatment of municipal sewage at publicly owned treatment works (POTWs) leads to the production of considerable amounts of residual solid material known as sewage sludge, which is widely used in agriculture and land reclamation. Elevated levels of naturally-occurring and man-made radionuclides have been found in sewage sludge samples, suggesting the possible radiation exposure of POTW workers and members of the public. The Interagency Steering Committee on Radiation Standards (ISCORS) therefore conducted a limited survey of radioactivity in sewage sludge across the United States. Concurrently, to assess the levels of the associated doses to people, it undertook to model the transport of the relevant radionuclides from sewage sludge into the local environment. The modeling work consisted of two steps. First, seven general scenarios were constructed to represent typical situations in which members of the public or POTW workers may be exposed to sewage sludge. Then, the RESRAD multi-pathway environmental transport model generated sewage sludge concentration-to-dose conversion factors. This report describes the results of this dose modeling effort, and provides a complete description and justification of the dose assessment methodology.

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