Abstract
Thermodynamic modelling has been used to study the behaviour of the activation products Ni-59, Nb-94 and Zr-93 in the cementitious/bentonite/crushed-rock near field of a radioactive waste repository. The work had two main aims: (a) to obtain estimates of the most realistic solubilities for the three radioelements present in decommissioning waste under the near-field conditions, (b) to calculate the rate of migration of the radionuclides through the near-field barriers. The calculated solubilities at pH 12.4 and 25 deg C are approximately 1*10{sup -7} M, 4*10{sup -9} M and 6*10{sup -8} M for Ni, Zr and Nb respectively. These values correspond to solubilities measured for amorphous-type solids where very efficient solid-liquid separation is achieved. Uncertainties in the data values are discussed. Calculations to investigate the effect of a lower host-rock temperature on these solubilities suggest that the solubilities will rise to about 1*10{sup -5} M, 8*10{sup -9} M for Ni, Zr and Nb respectively, but there is less certainty in the input data. Modelling has been performed using the CHEQMATE computer code to calculate the rate of migration of the radioelements through the concrete and bentonite/crushed-rock barriers, assuming solubility control and control by corrosion of the source metals. The results demonstrated that
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Heath, T G;
Moreton, A;
Porter, F;
Sharland, S;
Smith, A;
Tweed, C
[1]
- AEA Technology, Harwell (United Kingdom). Harwell Lab.
Citation Formats
Heath, T G, Moreton, A, Porter, F, Sharland, S, Smith, A, and Tweed, C.
Modelling study of the distribution of activation products in a cementitious repository.
Finland: N. p.,
1993.
Web.
Heath, T G, Moreton, A, Porter, F, Sharland, S, Smith, A, & Tweed, C.
Modelling study of the distribution of activation products in a cementitious repository.
Finland.
Heath, T G, Moreton, A, Porter, F, Sharland, S, Smith, A, and Tweed, C.
1993.
"Modelling study of the distribution of activation products in a cementitious repository."
Finland.
@misc{etde_10146397,
title = {Modelling study of the distribution of activation products in a cementitious repository}
author = {Heath, T G, Moreton, A, Porter, F, Sharland, S, Smith, A, and Tweed, C}
abstractNote = {Thermodynamic modelling has been used to study the behaviour of the activation products Ni-59, Nb-94 and Zr-93 in the cementitious/bentonite/crushed-rock near field of a radioactive waste repository. The work had two main aims: (a) to obtain estimates of the most realistic solubilities for the three radioelements present in decommissioning waste under the near-field conditions, (b) to calculate the rate of migration of the radionuclides through the near-field barriers. The calculated solubilities at pH 12.4 and 25 deg C are approximately 1*10{sup -7} M, 4*10{sup -9} M and 6*10{sup -8} M for Ni, Zr and Nb respectively. These values correspond to solubilities measured for amorphous-type solids where very efficient solid-liquid separation is achieved. Uncertainties in the data values are discussed. Calculations to investigate the effect of a lower host-rock temperature on these solubilities suggest that the solubilities will rise to about 1*10{sup -5} M, 8*10{sup -9} M for Ni, Zr and Nb respectively, but there is less certainty in the input data. Modelling has been performed using the CHEQMATE computer code to calculate the rate of migration of the radioelements through the concrete and bentonite/crushed-rock barriers, assuming solubility control and control by corrosion of the source metals. The results demonstrated that the assumption of solubility control of corrosion control made little difference to the model, because in the corrosion control case the metals reached their solubility limits rapidly. The inclusion of groundwater flow increased the metal ion concentration by less than a factor of 2 in each case. The fluxes out of the TVO repository after a given time were predicted to be significantly less than those from the IVO repository due to the greater thickness of concrete in the TVO repository. (orig.). (16 refs., 9 figs., 23 tabs.).}
place = {Finland}
year = {1993}
month = {Sep}
}
title = {Modelling study of the distribution of activation products in a cementitious repository}
author = {Heath, T G, Moreton, A, Porter, F, Sharland, S, Smith, A, and Tweed, C}
abstractNote = {Thermodynamic modelling has been used to study the behaviour of the activation products Ni-59, Nb-94 and Zr-93 in the cementitious/bentonite/crushed-rock near field of a radioactive waste repository. The work had two main aims: (a) to obtain estimates of the most realistic solubilities for the three radioelements present in decommissioning waste under the near-field conditions, (b) to calculate the rate of migration of the radionuclides through the near-field barriers. The calculated solubilities at pH 12.4 and 25 deg C are approximately 1*10{sup -7} M, 4*10{sup -9} M and 6*10{sup -8} M for Ni, Zr and Nb respectively. These values correspond to solubilities measured for amorphous-type solids where very efficient solid-liquid separation is achieved. Uncertainties in the data values are discussed. Calculations to investigate the effect of a lower host-rock temperature on these solubilities suggest that the solubilities will rise to about 1*10{sup -5} M, 8*10{sup -9} M for Ni, Zr and Nb respectively, but there is less certainty in the input data. Modelling has been performed using the CHEQMATE computer code to calculate the rate of migration of the radioelements through the concrete and bentonite/crushed-rock barriers, assuming solubility control and control by corrosion of the source metals. The results demonstrated that the assumption of solubility control of corrosion control made little difference to the model, because in the corrosion control case the metals reached their solubility limits rapidly. The inclusion of groundwater flow increased the metal ion concentration by less than a factor of 2 in each case. The fluxes out of the TVO repository after a given time were predicted to be significantly less than those from the IVO repository due to the greater thickness of concrete in the TVO repository. (orig.). (16 refs., 9 figs., 23 tabs.).}
place = {Finland}
year = {1993}
month = {Sep}
}