scholarly journals The effects of aging on compressive strength of low-level radioactive waste form samples

1996 ◽  
Author(s):  
J.W. Jr. McConnell ◽  
R.M. Jr. Neilson
Keyword(s):  
Compressive Strength ◽  
Radioactive Waste ◽  
Waste Form ◽  
Low Level ◽  
Effects Of Aging ◽  
Low Level Radioactive Waste

A Procedure to Evaluate the Potential for Microbially Influenced Degradation of Cement-Solidified Low-Level Radioactive Waste Forms

1995 ◽  
Vol 412 ◽  
Author(s):  
R. D. Rogers ◽  
M. A. Hamilton ◽  
R. H. Veeh ◽  
J. W. Mcconnell
Keyword(s):  
Radioactive Waste ◽  
Evaluation Method ◽  
Structural Integrity ◽  
Nuclear Regulatory Commission ◽  
The United States ◽  
Ion Exchange Resin ◽  
Waste Form ◽  
Low Level ◽  
Waste Forms ◽  
Low Level Radioactive Waste

AbstractBecause of its apparent structural integrity, cement has been widely used in the United States as a binder to solidify Class B and C low-level radioactive waste (LLW). However, the resulting cement preparations are susceptible to failure due to the actions of stress and environment. An environmentally mediated process that could affect cement stability is the action of naturally occurring microorganisms. The U.S. Nuclear Regulatory Commission (NRC), recognizing this eventuality, stated in their Technical Position on Waste Form, Revision 1, that the effects of microbial action on waste form integrity must be addressed. This paper provides recent results from a program that examined the effects of microbially influenced degradation (MID) on cement-solidified LLW. Data are provided which were obtained during the development of an evaluation method using acid-producing bacteria. Results presented here are from work with one type of these bacteria, the sulfur-oxidizingThiobacillus. Commercially prepared, cement-solidified, low-level radioactive waste form samples made from power reactor wastes were evaluated using a new biodegradation test developed for the NRC. Testing demonstrated that MID has the potential to severely compromise the structural integrity and nuclide retentiveness of ion-exchange resin and evaporator-bottoms wastes that have been solidified with cement. It was found that the waste form specimens physically deteriorated after 60 days of exposure to the thiobacilli. Also, the data show that significant amounts of Cs-137, Cs-134, Co-60, C-14, Tc-99, and Sr-90 contained in the waste forms were leached in the presence ofThiobacillus.

The Possibility for Microbially Influenced Degradation of Cement Solidified Low-Level Radioactive Waste Forms

1992 ◽  
Vol 294 ◽  
Author(s):  
Robert D. Rogers ◽  
Melinda A. Hamilton ◽  
John W. Mcconnell
Keyword(s):  
Radioactive Waste ◽  
Structural Integrity ◽  
Nuclear Regulatory Commission ◽  
Waste Form ◽  
Sufficient Evidence ◽  
Reduced Sulfur Compounds ◽  
Burial Site ◽  
Low Level ◽  
Acid Producing Bacteria ◽  
Low Level Radioactive Waste

ABSTRACTThe Nuclear Regulatory Commission (NRC) regulations 10 CFR Part 61, “Licensing Requirements for Land Disposal of Radioactive Waste,” regulate the disposal of radioactive waste and provides, among other stipulations, that class B and C low-level radioactive waste (LLW) be stabilized. This is intended to ensure that solidified waste does not structurally degrade and cause subsidence in the disposal unit's cover system. It is reasoned that deterioration of the waste form could adversely effect the stability of the burial site and lead to the release of radionuclides to the environment. Because of its apparent structural integrity, cement has been widely used as a binder to solidify LLW. However, the resulting preparations called pozzolanic cements are susceptible to failure due to the actions of stress and environment.This paper presents data from the literature that document the significance of biologically mediated chemical attack on concrete, in general. Concrete is susceptible to aggressive reaction with acids (both mineral and organic) of natural and anthropogenic origin. If persistent, such reactions ultimately lead to structural failure. Groups of microorganisms have been identified that are capable of metabolically converting organic and inorganic substrates into organic and mineral acids.The literature supports the conclusions that acid-producing bacteria of one type or another could be prevalent in all soils, even at depths expected for burial of LLW. Given the appropriate conditions of micro-environment and suitable substrate for growth, these bacteria will create conditions conducive to concrete deterioration. Growth substrates used by acid-producing bacteria (i.e., ammonia compounds, other reduced nitrogen compounds, sulfur and reduced sulfur compounds, reduced iron compounds, as well as organic carbon) could be naturally present in the disposal environment or be provided by the contents of the waste form.Sufficient evidence is presented which demonstrates the potential for microbially-influenced deterioration of cement-solidified LLW. These data are the basis for the NRC initiating the development of appropriate tests to determine the resistance of cement-solidified LLW to microbiologically induced degradation.

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