Measurements performed in Goiânia after a new intervention action in 2001.

Brazil's worst radiological accident took place in 1987, in the city of Goiânia. In 1999 and 2000, detailed measurements of 137Cs contamination were performed in junkyard II, one of the places involved in the accident. High values of 137Cs activity per unit mass were found in soil layers at depths between 10 and 40 cm from the surface, reaching values as high as 175 kBq x kg(-1). High values of 137Cs concentration in fruits and plants were also observed. Moreover, values of ambient dose equivalent rate at 1 m above the ground were found to be higher than the limit of 1.0 microSv x h(-1) set by the Brazilian National Nuclear Energy Commission (CNEN) in 1987. In February 2000, the CNEN was informed about the results of our measurements. As consequence, in August 2001, the CNEN performed a new intervention action in the area, covering all its extension with a concrete layer and removing some plants and trees. The new remedial action reduced the dose rate to approximately 13% of the value prior to covering the site in concrete, reaching values below the CNEN limit, as demonstrated by the measurements presented here.