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Modelling of the near-field chemistry of the SMA repository at the Wellenberg site

Technical Report:

Abstract

Of the materials which make up the L/ILW repository for short-lived low- and intermediate-level wastes, around 95 weight percent consists of concrete, around 4% of steel and around 1% of high molecular weight organic waste components. In this report, models are used to evaluate the long-term stability of concrete, steel and high molecular weight organic components under repository conditions. The results of this study will then form the basis for describing release of radionuclides from the disposal caverns, and particularly the sorption of nuclides on concrete. In the disposal caverns, concrete is exposed to a range of processes which affect its stability. External processes include the leaching of hydrated cement by percolating groundwater, while internal processes include dissolution of repository components in cement porewater which can then react with the concrete. Of greatest significance in this respect are the high molecular weight organic waste components which degrade to organic acids in the disposal environment and then react with the basic components of the concrete. The leaching of hydrated cement is described, using a mixing tank model, as a sequence of batch experiments in which the same cement block reacts repeatedly with fresh groundwater. The model is based on the work  More>>
Authors:
Neall, F B [1] 
  1. Paul Scherrer Inst. (PSI), Villigen (Switzerland)
Publication Date:
Sep 01, 1994
Product Type:
Technical Report
Report Number:
PSI-94-18
Reference Number:
SCA: 400201; 052002; PA: AIX-26:007756; EDB-95:009070; SN: 95001300787
Resource Relation:
Other Information: PBD: Sep 1994
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; CONCRETES; LEACHING; SWITZERLAND; UNDERGROUND DISPOSAL; EXPERIMENTAL DATA; GROUND WATER; MATHEMATICAL MODELS; PH VALUE; REDOX REACTIONS; THEORETICAL DATA; 400201; 052002; CHEMICAL AND PHYSICOCHEMICAL PROPERTIES; WASTE DISPOSAL AND STORAGE
OSTI ID:
10103919
Research Organizations:
Paul Scherrer Inst. (PSI), Villigen (Switzerland)
Country of Origin:
Switzerland
Language:
English
Other Identifying Numbers:
Other: ON: DE95610661; TRN: CH9400375007756
Availability:
OSTI; NTIS; INIS
Submitting Site:
CHN
Size:
83 p.
Announcement Date:
Jun 30, 2005

Technical Report:

Citation Formats

Neall, F B. Modelling of the near-field chemistry of the SMA repository at the Wellenberg site. Switzerland: N. p., 1994. Web.
Neall, F B. Modelling of the near-field chemistry of the SMA repository at the Wellenberg site. Switzerland.
Neall, F B. 1994. "Modelling of the near-field chemistry of the SMA repository at the Wellenberg site." Switzerland.
@misc{etde_10103919,
title = {Modelling of the near-field chemistry of the SMA repository at the Wellenberg site}
author = {Neall, F B}
abstractNote = {Of the materials which make up the L/ILW repository for short-lived low- and intermediate-level wastes, around 95 weight percent consists of concrete, around 4% of steel and around 1% of high molecular weight organic waste components. In this report, models are used to evaluate the long-term stability of concrete, steel and high molecular weight organic components under repository conditions. The results of this study will then form the basis for describing release of radionuclides from the disposal caverns, and particularly the sorption of nuclides on concrete. In the disposal caverns, concrete is exposed to a range of processes which affect its stability. External processes include the leaching of hydrated cement by percolating groundwater, while internal processes include dissolution of repository components in cement porewater which can then react with the concrete. Of greatest significance in this respect are the high molecular weight organic waste components which degrade to organic acids in the disposal environment and then react with the basic components of the concrete. The leaching of hydrated cement is described, using a mixing tank model, as a sequence of batch experiments in which the same cement block reacts repeatedly with fresh groundwater. The model is based on the work by Berner (1990) but has been extended to include other solid cement phases and can, in a simple way, take account of the degradation of high molecular weight organics and their reaction with hydrated cement. The mixing tank model shows that, given the low water fluxes that are expected for a L/ILW repository, concrete remains stable over geological time spans provided only small volumes of high molecular organics are present. If high concentrations of these materials ar present, the longevity of the concrete may be reduced. (author) figs., tabs., refs.}
place = {Switzerland}
year = {1994}
month = {Sep}
}