Soil and Indoor Radionuclides Related to the Plymouth Pilgrim Nuclear Power Plant Area

Given the importance of internal dosimetry from inhaled or ingested radioactive particles attributable to nuclear fuels and fission, in this study we analyzed samples collected from indoor home dusts and surface soils in areas surrounding and up to 13 km from the Pilgrim Nuclear Power Plant (PNPP) in Plymouth, Massachusetts (USA). Indoor dust (n=15) from homes (n=10) and outdoor soil samples (n=31, yielding a total of n=46 original samples) were analyzed by γ-spectrometry, and α- and β-rate counting. Sixteen aliquots (16) from the 46 samples were analyzed by α-spectrometry for varying combinations of isotopic uranium, and isotopic thorium, and by Scanning Electron Microscopy with Energy Dispersive X-ray analysis. Detection of uranium and thorium confirmed that radioactive particles were of power plant origin. The presence of fission-related radionuclides was also confirmed by α- and γ-spectrometry. The highest activities of cesium-137 and lead-210 were observed in public areas outside of radiation protection zones near the PNPP, but evidence of fission related radionuclides was found up to 12.1 km. Testing of soil and dust collected <1 km from the plant detected up to 20 times the background activity for cesium-137 and lead-210. Elevated thorium-234, and trace activities of cobalt-60 and uranium-235 were detected in surface soils sampled <1 km from the plant using γ-spectrometry, including uranium (>0.5%) and thorium (>5.0%) in microparticles. These isotopes were undetected or at background at beyond these distances. This study suggests that radioisotopes released from nuclear power plants may be found in the soils and indoor dusts of surrounding homes.