Decontamination Limits for Americium-241
See the memorandum from R. E. Cunningham to H. D. Thornburg dated September 15, 1981.
This memo provides appropriate surface and soil decontamination limits for Am-241. Based on the total dose from inhalation and ingestion, the soil concentration limit for Am-241 is calculated to be 30 picocuries per gram (pCi/g) in order not to exceed the 3 millirad per year recommended by the EPA.
Acceptable surface contamination levels for Am-241 are specified in "Guidelines for Decontamination of Facilities and Equipment Prior to Release for Unrestricted Use or Termination of Licenses for Byproduct, Source, or Special Nuclear Material." The maximum and average levels of fixed Am-241 contamination permitted on surfaces released for unrestricted use is 300 and 100 disintegration per minute per 100 square centimeters (dpm/100 cm2), respectively. Removable contamination should not exceed 20 dpm/100 cm2.
With respect to soil decontamination limits, the EPA recommended on November 30, 1977, radiation dose guidelines for transuranium elements such that no individual will receive a radiation dose in excess of 1 millirad per year to the lung and 3 millirad per year to the bone from exposure to the contaminated soil (42 FR 60956-60959). In this case, the solubility classification of Am-241 is a W compound (see ICRP Publication 30) and its existence in soil will contribute to the inhalation and ingestion pathways through resuspension of soil in air and uptake from plants. The critical organ is the bone. Based on the total dose from inhalation and ingestion, the soil concentration limit for Am-241 is calculated to be 30 pCi/g in order not to exceed the 3 millirad per year limit.
Regulatory references: None
Subject codes: 3.6, 7.6, 8.4, 12.4