Modeling of an Optimized Multilayer Cover Design for a Uranium Mill Tailings Disposal

• Type: Article in International Conference Proceedings Book
• Date: 2011

Authors

Maria de Lurdes Dinis (Author) FEUP; António Fiúza (Author) FEUP

Conference proceedings International

Title: Waste Management Symphosia 2011

The annual Waste Management (WM) Conference, presented by WM Symposia (WMS), is widely regarded as the premier international conference for the management of radioactive material and related topics. WMS is a non-profit organization dedicated to education and opportunity in waste management. It was founded to provide a forum for discussing and seeking cost-effective and environmentally responsible solutions to the safe management and disposition of radioactive waste and radioactive materials.

Phoenix, Arizona, USA, 27 Fevereiro a 04 de Março

Scientific classification

FOS: Engineering and technology > Other engineering and technologies

CORDIS: Physical sciences > Mathematics ; Natural sciences > Environmental science ; Technological sciences > Engineering ; Physical sciences > Physics ; Physical sciences > Computer science

Other information

Abstract (EN): This paper presents a computer based algorithm to evaluate the performance of an engineered cover design for a uranium tailings disposal. The developed research was applied to a specific case study, the Urgeiriça uranium mining site located in the central north region of Portugal. A multi-layer cover design was proposed in the remediation program for this site to be placed above the tailings disposal. The tailings composition is highly heterogeneous, in particular for radium concentration which varies between 3,000 and 67,000 Bq/kg. A value of 7.21 Bq.m-2.s-1 was calculated for radon exhalation through the tailings, considering an average radium concentration of 12,900 Bq/kg. The cover was designed to mitigate the releases of radon gas to the surface and to minimize water infiltration to the mill tailings. An algorithm was developed to simulate the radon flux attenuation given by an arbitrary cover providing as an output the radon flux exhalation through the cover system. In addition, it is also possible to estimate the thickness of the cover that allows a radon flux inferior to the acceptable one, to accomplish legal limits. The algorithm is based on the diffusion theory describing the long-term radon transport through the tailings and the cover’s material and it was implemented in Matlab. The algorithm was simulated for the multi-layer cover design proposed in the remediation program, for an optimized multilayer cover design, and another simulation was done to accomplish a defined threshold. The cover proposed in the remediation program, with 5.15 meters thickness, eliminated almost all the radon exhalation (99.82%). The optimized multilayer cover with 3 or 2 meters could achieve similar results: the radon exhalation decreases, respectively 99.55% or 96.39%. To accomplish the legal limits a cover system with 1 meter would be enough to reduce the average radon exhalation to the defined threshold.

Language: English

Type (Professor's evaluation): Scientific