Reassessment of the Goiânia radioactive waste repository in Brazil using HYDRUS-1D

Abstract

Abstract:In September 1987 an accident occurred with a cesium chloride (CsCl) teletherapy source taken from a cancer therapy institute in Goiânia, Brazil. Misuse of the abandoned source caused widespread contamination of radioactive material (about 50 TBq of 137 Cs) in the town of Goiânia. Decontamination of affected areas did lead to about 3,500 m 3 of solid radioactive wastes, which were disposed in two near-surface repositories built in concrete in 1995. This paper documents a safety assessment of one of the low-level radioactive waste deposits containing 137 Cs over a time period of 600 years. Using HYDRUS-1D, we first obtained estimates of water infiltrating through the soil cover on top of the repository into and through the waste and its concrete liners and the underlying vadose zone towards groundwater. Calculations accounted for local precipitation and evapotranspiration rates, including root water uptake by the grass cover, as well as for the effects of concrete degradation on the hydraulic properties of the concrete liners. We next simulated long-term water fluxes and 137 Cs transport from the repository towards groundwater. Simulations accounted for the effects of 137 Cs sorption and radioactive decay on radionuclide transport from the waste to groundwater, thus permitting an evaluation of potential consequences to the environment and long-term exposure to the public. Consistent with previous assessments, our calculations indicate that very little if any radioactive material will reach the water table during the lifespan of the repository, also when accounting for preferential flow through the waste.

Rien van Genuchten: A short autobiography

“…One major focus in Brazil was on radioactive materials, including the environmental aspects of mining and milling activities using “naturally occurring radioactive materials,” or NORMs (Pontedeiro et al., 2010). Other projects involving radioactive waste stemmed from uranium mining activities (Cotta et al., 2020) and the mishandling of cesium‐containing teletherapy equipment, which caused widespread pollution (Pontedeiro et al., 2018). We further looked more closely at the fluid flow properties of carbonate rocks using NMR and microCT data along with pore network modeling (e.g., Godoy et al., 2019), the latter often in collaboration with Amir Raoof at Utrecht University.…”

Immediate decisions based on long-term consequence evaluation for a radiological event

“…Approximately 19 mg of caesium-137 chloride was released from a radiotherapy unit by metal scavengers who were selling the shield lead as scrap metal. 1 The information regarding a potential event characterized by radioactive environmental contamination might be unavailable, with respect to its preliminary description. This lack of information tends to complicate the first response actions and its evaluation.…”