Co-treatment of mixed radionuclides in large volumes of contaminated water by carbonate precipitation reactions

Supervisors: Ian Burke (School of Earth and Environment); Doug Stewart (Civil Eng.) and James Graham (National Nuclear Laboratory)

OUTLINE: Treatment of radioactive effluents and groundwaters containing 137Cs and 90Sr at low molar concentrations is traditionally achieved by cation exchange. However, the effectiveness of the process is reduced by completing ions present in groundwaters (e.g. Ca2+, Na+) and anionic radionuclides are not removed (99Tc, 14C). Biological methods are currently being considered as an in situ treatment for radionuclides in contaminated ground; however, ex situ biological treatment is likely to be too slow, costly and complex for practical use. Inorganic precipitation of 90Sr2+ and 14C as insoluble carbonates (and 99Tc as reduced TcO2), therefore offers a lower cost alternative, producing a solid residue that is readily grouted in cement wasteforms. The studentship will develop novel precipitation reactions for inorganic carbonate that also result in high uptake of radionuclides under both aerobic and reducing conditions. The mechanism of radionuclide uptake will be determined as and the long term stability of the wasteform produced will be tested. The results will be compared to other treatment options or use of commercially available ion exchange resins. Thermodynamic modelling will then be used to understand the reaction progression and to optimise the reaction. The project will also seek scale up the most promising reaction conditions to column scale to develop methods applicable to flowing systems and large volume treatment. A full cost-benefit analysis will also be performed for an installed engineered treatment system versus likely alternative methods.

Objectives

1. Use labortaory experiements to investigate the potential use of alkaline carbonate precipitation reactions for the co-treatment of waters contaminated with 14C, 90Sr and 99Tc.
2. To test this novel method against commercially available removal methods (e.g. ion exchange resins) and compare effectiveness with the likely costs involved.
3. To begin to scale up the treatment design via model simulations and column scale experiments to understand the applicability of carbonate precipitation reactions for large scale treatment.

Eligibility: UK or EU citizens normally resident in the UK. The applicant must satisfy the requirements to register as a doctoral student at the University of Leeds, which involves holding appropriate Honours, Diploma or Masters Degree and having passed the appropriate English language tests. Applications are invited from graduates who have, or expect to gain, a good degree in chemistry, geology, environmental science, materials science, chemical engineering or another relevant science discipline. Relevant Masters level qualifications are also welcomed. The applicant should have a good command of both written and spoken English.

See http://www.see.leeds.ac.uk/people/i.burke for more details.