Estimation of exposure levels of terrestrial biota and radiation exposure around IPEN´s facilities

Abstract

Humans are exposed to natural radiation; soil is a major source of external and internal exposure of radiation. The external exposure from the soil is associated with gamma radiation and internal exposure mainly from radon inhalation. The aim of this study is to evaluate the exposure levels of terrestrial biota and to estimate the radiation exposure around IPEN facilities. The Institute comprises several nuclear and radioactive facilities including a research reactor, cyclotrons and a radioisotope and radiopharmaceutical production plant. The ERICA Tool was used to calculate the exposure levels of terrestrial biota; the estimation of radiation exposure for humans was determined using a model proposed by UNSCEAR (Absorbed dose rate in air and Annual effective dose equivalent) and Excess Lifetime Cancer Risk. Six soil points were collected and their activity concentrations were measured by gamma spectrometry, using a HPGe detector. Two soil points showed a risk coefficient greater than 1, suggesting that the screening dose ratio of 10μGy h 1 might be exceeding for the most exposed species, namely lichen and bryophytes, even though the activity concentration values of the analyzed radionuclides showed no evidence of soil contamination due to the atmospheric discharges of the IPEN facilities. Thus, the radioactive discharges in the soil from all facilities are negligible. Hence, the authors concluded that the ERICA Tool can be useful in assisting environmental radiological monitoring program for decision making, especially regarding: points collected, sample types and sampling frequency.