Assessment of the Impact of Fiber Mass UP2 Degradation Products on Ni(II) and Eu(III) Sorption
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
The waste produced at Swedish nuclear power plants is deposited in an underground repository, SFR. Different substances in the waste or in degradation products may exhibit complexation properties. The complexation of deposited radionuclides with such ligands may affect the mobility of the radionuclides and decrease their sorption on the cement phase, which is used as protective barrier in SFR. In this study, metal ions adsorption to cement in the presence of fiber mass UP2 degradation products under alkaline conditions has been studied. Model metal ions used in this work were nickel (II) and europium (III).
It has been shown that alkaline degradation of UP2 is dependent on both pH and temperature. Alkaline degradation of UP2 was performed at two different alkalinities. Degradation at pH≈12.5 and constant stirring gave a TOC content of about 900 mg/L, after 6 month at 32 °C. Degradation at higher pH≈13.5, but at the same temperature and stirring conditions, resulted in a TOC concentration of about 5100 mg/L after 6 month degradation. Additionally, UP2 also degraded at elevated temperature. Result from this case gave a TOC concentration of about 252 mg/L after 3 month, when UP2 was conditioned at pH≈12.5 and T=60-65 °C without continuous stirring. Degradation at these forced conditions after 6 month resulted in a decreased pH of the sample (pH=9.3) and a TOC content of about 1100 mg/L.
Sorption experiment of Ni(II) and Eu(III) onto hydrated cement was made in presence of the UP2 degradation products at different solid to liquid (S:L) ratio (available cement surface area). A precipitate was found on the cement material in the Ni(II) sorption experiments which prevents a proper evaluation of the results. The Kd values for Eu(III) sorption after 33 days of equilibration in the presence of degradation products, is in the range 0.1- 0.28 [m3/kg] for cement with a BET specific surface area of about 94.9 m2/g, i.e. giving a partition coefficient of (1.0- 3.0)×10-6 m3/m2.
Place, publisher, year, edition, pages
UP2 fiber, degradation, radionuclides, sorption, cement
IdentifiersURN: urn:nbn:se:kth:diva-185690OAI: oai:DiVA.org:kth-185690DiVA: diva2:922823