Characterisation of a high pH cement backfill for the geological disposal of nuclear waste: the Nirex Reference Vault Backfill

TY - JOUR

T1 - Characterisation of a high pH cement backfill for the geological disposal of nuclear waste

T2 - Applied Geochemistry

AU - Vasconcelos, Rita G. W.

AU - Beaudoin, Nicolas

AU - Hamilton, Andrea

AU - Hyatt, Neil C.

AU - Provis, John L.

AU - Corkhill, Claire L.

PY - 2018/2/28

Y1 - 2018/2/28

N2 - In a conceptual UK geological disposal facility for nuclear waste within a high-strength, crystalline geology, a cement-based backfill material, known as Nirex Reference Vault Backfill (NRVB), will be used to provide a chemical barrier to radionuclide release. The NRVB is required to have specific properties to fulfil the operational requirements of the geological disposal facility (GDF); these are dependent on the chemical and physical properties of the cement constituent materials and also on the water content. With the passage of time, the raw materials eventually used to synthesise the backfill may not be the same as those used to formulate it. As such, there is a requirement to understand how NRVB performance may be affected by a change in raw material supply. In this paper, we present a review of the current knowledge of NRVB and results from a detailed characterisation of this material, comparing the differences in performance of the final product when different raw materials are used. Results showed that minor differences in the particle size, surface area and chemical composition of the raw material had an effect on the workability, compressive strength, the rate of hydration and the porosity, which may influence some of the design functions of NRVB. This study outlines the requirement to fully characterise cement backfill raw materials prior to use in a geological disposal facility and supports ongoing assessment of long-term post-closure safety.

AB - In a conceptual UK geological disposal facility for nuclear waste within a high-strength, crystalline geology, a cement-based backfill material, known as Nirex Reference Vault Backfill (NRVB), will be used to provide a chemical barrier to radionuclide release. The NRVB is required to have specific properties to fulfil the operational requirements of the geological disposal facility (GDF); these are dependent on the chemical and physical properties of the cement constituent materials and also on the water content. With the passage of time, the raw materials eventually used to synthesise the backfill may not be the same as those used to formulate it. As such, there is a requirement to understand how NRVB performance may be affected by a change in raw material supply. In this paper, we present a review of the current knowledge of NRVB and results from a detailed characterisation of this material, comparing the differences in performance of the final product when different raw materials are used. Results showed that minor differences in the particle size, surface area and chemical composition of the raw material had an effect on the workability, compressive strength, the rate of hydration and the porosity, which may influence some of the design functions of NRVB. This study outlines the requirement to fully characterise cement backfill raw materials prior to use in a geological disposal facility and supports ongoing assessment of long-term post-closure safety.

KW - geological disposal

KW - nuclear waste

KW - cement

KW - mineralogy

KW - microstructure

UR - http://www.sciencedirect.com/science/journal/08832927?sdc=2

U2 - 10.1016/j.apgeochem.2017.11.007

DO - 10.1016/j.apgeochem.2017.11.007

M3 - Article

VL - 89

SP - 180

EP - 189

JO - Applied Geochemistry

JF - Applied Geochemistry

SN - 0883-2927

ER -