Cellulose degradation and nuclear waste management: characterization of cellulose degradation products by ESI-ToF-MS

SCK•CEN Mentor

Hendrix Katrien, khendrix@sckcen.be, +32 (0)14 33 32 55

Expert group

R&D Waste Packages

SCK•CEN Co-mentor

Mastroleo Felice , fmastrol@sckcen.be , +32 (0)14 33 23 88

Introduction

Many forms of radioactive waste contain significant amounts of cellulose, such as paper tissues. Some of these waste forms are currently cemented and would be disposed of in a deep underground repository. Other cellulose containing waste forms would be disposed of in a near‑surface repository. However, due to irradiation and the highly alkaline and anaerobic conditions in such disposal facilities, cellulose will degrade into various smaller organic molecules. This can cause safety issues, as these molecules could increase the mobility of multivalent radionuclides. Indeed, by forming strong complexes, the solubility of these radionuclides in the waste form increases. Moreover, sorption of these radionuclides will be reduced as these complexes do not have a charge. Most research focusses on the formation of iso-saccharinic acid, as its α isomer strongly complexes with trivalent and tetravalent long-lived radionuclides. To fully assess the safety issues at hand, it is also necessary to investigate if other degradation products are formed and to identify these organic molecules. 

Objective

In this study, the various degradation products of cellulose will be identified and quantified. Moreover, the influence of irradiation, temperature, pH and the presence of oxygen on the degradation products will be investigated at different points in time.

Cellulosic material in the form of paper tissues was subjected to a range of conditions (high pH, elevated temperature, absence/presence of oxygen and irradiation) to provoke degradation. The subsequent degradation products are to be analysed by ESI-ToF MS technique. This is a mass spectrometry (MS) technique using electrospray ionisation (ESI). ESI produces an aerosol of ions by applying a high voltage on a liquid sample, which subsequently goes through a Time-of-Flight (ToF) mass analyzer resulting in a specific spectrum that allows to identify the molecules in the liquid. To optimize the ESI-MS method for these samples, commercially available, isolated degradation products that are known from literature, will be injected separately. This will allow the unraveling of the more complex MS spectra of the actual cellulose degradation samples.

During this master thesis, the focus will be on analytical, organic chemistry, having a broader scope within radioactive waste management. This research is part of the Cement-Organic-Radionuclide Interactions (CORI) work package, within the European Joint Programme on Radioactive Waste Management (EURAD). The work will be done at SCK CEN, where the necessary equipment, installation and materials are present.

The minimum diploma level of the candidate needs to be

Academic bachelor

The candidate needs to have a background in

Chemistry , Bio-engineering