Award Date


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Biological Science

First Committee Member

Penny S. Amy

Number of Pages



The study of microorganisms in oligotrophic environments is vital to understanding the geology and ecology of Nevada, and in particular, Yucca Mountain and the Nevada Test Site. Native to the Yucca Mountain tuff and to the Nevada Test Site soil are microorganisms, existing in biofilms, which are capable of corroding metals, and producing acids or enzymes that can degrade materials such as wood and cardboard. Studying the environmental conditions that could promote the growth of such microorganisms is essential for the modeling of the Yucca Mountain repository and the waste burial program on the Nevada Test Site. The first phase of this research is to determine boundary limits of temperature and humidity, as they relate to biofilm formation on candidate repository canister materials used in the Yucca Mountain Repository. It is necessary to model a stable, high-level nuclear waste repository that will not corrode within the institutionalized period of 300 years. The second phase involves a different approach from the Yucca Mountain repository modeling. The Nevada Test Site is the location for a proposed low-level nuclear waste repository. Breakdown of waste packaging material will cause a shifting and collapsing of waste material and surrounding backfill which can collapse the closure cap. Water could percolate down into the waste material creating a leachate that could affect water reservoirs. This study of biofilms should allow the development of a microbially based process to accelerate degradation of waste packaging material prior to closure; A separate investigation relating to the proposed, high-level nuclear waste repository deals with detecting thermophilic bacteria from calcite deposits within the fractures of Yucca Mountain. There is a possibility that the calcite deposits resulted from an upwelling of subsurface, thermal water containing dissolved calcium carbonate. As water cooled, the dissolved minerals precipitated forming calcite deposits. The thermal water might have selected for thermophilic bacteria; thus, their presence could lend support to the subsurface, thermal water origin of Yucca Mountain's calcite deposits. The possibility that subsurface, thermal water could rise inside Yucca Mountain may impact Yucca Mountain's suitability as the proposed site of a high-level nuclear waste repository.


Biodegradation; Implications; Integrity; Microbial; Microbially Induced Corrosion; Nuclear Waste Storage; Storage; Structural; Structural Integrity; Waste

Controlled Subject

Microbiology; Environmental engineering

File Format


File Size

5683.2 KB

Degree Grantor

University of Nevada, Las Vegas




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