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Research output: Contribution to conference - Without ISBN/ISSN › Conference paper › peer-review
Research output: Contribution to conference - Without ISBN/ISSN › Conference paper › peer-review
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TY - CONF
T1 - Towards the decontamination of plutonium contaminated bricks
T2 - ANS Global
AU - Kennedy, J.
AU - Boxall, C.
AU - Banford, A.
AU - Demmer, R.
AU - Parker, A.
PY - 2019/9/22
Y1 - 2019/9/22
N2 - There is a need for the decontamination of a number of plutonium-contaminated bricks encountered in a legacy BUTEX reprocessing plant on Sellafield site in the UK. Documentary review has indicated that the source of the contamination was a 8 mol dm -3 nitric acid process stream containing 10 mmol dm -3 of Pu in either the (III) or (IV) oxidation state. Here we have sought to emulate the behaviour of Pu(III) by treatment of fired clay brick surfaces with a solution of 10 mmol dm -3 Ce(III) nitrate in 8 mol dm -3 nitric acid. XRD, porosimetry and EDX measurements of the untreated bricks reveal them to be comprised of low porosity silica and aluminosilicate phases with a surface layer of a low-Si content Al-C-N oxide derived from the atmosphere of the kiln in which the bricks were fired. Depth profiling after an initial 6 week acid soak reveals that the acid penetrates <10 mm into the brick. SEM/EDX analysis reveals that acid treatment significantly roughens the brick surface due to dissolution the above described Al-C-N oxide layer. The EDX data also shows that virtually no Ce is retained as tenacious contamination at the brick surface; this may be due to a either a mass action/kinetic effect or taken to indicate that trivalent Ce(III) is less likely to absorb at the crystalline silica/aluminosilicate surface of the brick than its more easily hydrolysable tetravalent equivalent. Preliminary higher-resolution EDX analysis indicates that small quantities of Ce(III) can be detected in pores or cracks on the surface of acid-treated brick samples. This suggests that Ce(III) may be non-tenaciously sequestered into surface defects - and that a simple salt wash may be sufficient to remove it. Based on the above observations, potential decontamination strategies are discussed and future studies outlined.
AB - There is a need for the decontamination of a number of plutonium-contaminated bricks encountered in a legacy BUTEX reprocessing plant on Sellafield site in the UK. Documentary review has indicated that the source of the contamination was a 8 mol dm -3 nitric acid process stream containing 10 mmol dm -3 of Pu in either the (III) or (IV) oxidation state. Here we have sought to emulate the behaviour of Pu(III) by treatment of fired clay brick surfaces with a solution of 10 mmol dm -3 Ce(III) nitrate in 8 mol dm -3 nitric acid. XRD, porosimetry and EDX measurements of the untreated bricks reveal them to be comprised of low porosity silica and aluminosilicate phases with a surface layer of a low-Si content Al-C-N oxide derived from the atmosphere of the kiln in which the bricks were fired. Depth profiling after an initial 6 week acid soak reveals that the acid penetrates <10 mm into the brick. SEM/EDX analysis reveals that acid treatment significantly roughens the brick surface due to dissolution the above described Al-C-N oxide layer. The EDX data also shows that virtually no Ce is retained as tenacious contamination at the brick surface; this may be due to a either a mass action/kinetic effect or taken to indicate that trivalent Ce(III) is less likely to absorb at the crystalline silica/aluminosilicate surface of the brick than its more easily hydrolysable tetravalent equivalent. Preliminary higher-resolution EDX analysis indicates that small quantities of Ce(III) can be detected in pores or cracks on the surface of acid-treated brick samples. This suggests that Ce(III) may be non-tenaciously sequestered into surface defects - and that a simple salt wash may be sufficient to remove it. Based on the above observations, potential decontamination strategies are discussed and future studies outlined.
KW - Aluminum oxide
KW - Brick
KW - Contamination
KW - Decontamination
KW - Depth profiling
KW - Fuels
KW - Light water reactors
KW - Nitric acid
KW - Nuclear fuel reprocessing
KW - Plutonium compounds
KW - Silica
KW - Surface defects
KW - Acid treatments
KW - Crystalline silica
KW - Fired clay bricks
KW - Higher resolution
KW - Measurements of
KW - Oxidation state
KW - Reprocessing plant
KW - Surface layers
KW - Cerium compounds
M3 - Conference paper
SP - 556
EP - 565
Y2 - 22 September 2019 through 26 September 2019
ER -