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Review of Microbially Influenced Corrosion of High-Level Waste

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Review of Microbially Influenced Corrosion of High-Level Waste CNWRA 93-014 A S S. l ' -S I& 0X- 0,,,, al-s~~~~~~~~~~~ _ Prepared for Nuclear Regulatory Commission Contract NRC-02-88-005 Prepared by Center for Nuclear Waste Regulatory Analyses San Antonio, Texas June 1993 CNWRA 93-014 A REVIEW OF THE POTENTIAL FOR MICROBIALLY INFLUENCED CORROSION OF HIGH-LEVEL NUCLEAR WASTE CONTAINERS Prepared for Nuclear Regulatory Commission Contract NRC-02-88-005 Prepared by Gill Geesey Department of Microbiology Montana State University Bozeman, Montana Edited by Gustavo A. Cragnolino Center for Nuclear Waste Regulatory Analyses San Antonio, Texas June 1993 RECEIVED JUN 281993 CNWRA-WO PREVIOUS REPORTS IN SERIES Number Name Date Issued CNWRA 91-004 A Review of Localized Corrosion of High-Level Nuclear Waste Container Materials - I April 1991 CNWRA 91-008 Hydrogen Embrittlement of Candidate Container Materials June 1991 CNWRA 92-021 A Review of Stress Corrosion Cracking of High-Level Nuclear Waste Container Materials - I August 1992 CNWRA 93-003 Long-Term Stability of High-Level Nuclear Waste Container Materials: I - Thermal Stability of Alloy 825 February 1993 CNWRA 93-004 Experimental Investigations of Localized Corrosion of High-Level Waste Container Materials February 1993 ii ABSTRACT The potential for microbially influenced corrosion (MIC) of the candidate and alternate container materials for the proposed Yucca Mountain repository site is examined on the basis of an extensive review of the literature. A brief description of the environmental conditions expected outside the waste packages, in terms of the geology, hydrology, water chemistry, radiation, temperature, and moisture content, is followed by a detailed discussion regarding the characteristics of microbial life in subsurface environments. Energy and nutrient requirements to sustain bacterial colonies are examined in conjunction with the effect of various environmental parameters involved, such as salinity, water availability, temperature, pH, and the presence of electron acceptors. In the extensive discussion on MIC, separate consideration is given to different classes of metallic materials, including mild steels, copper and copper alloys, austenitic stainless steels, nickel and nickel alloys, and titanium and its alloys. It is concluded that all the alloys reviewed, with the possible exception of titanium, may be susceptible to MIC. The lack of relevant information on nickel-base alloys containing chromium as the main alloying element is emphasized. Finally, a set of recommendations is included to address some of the uncertainties confronted in predicting the occurrence of MIC under the environmental conditions anticipated at the proposed Yucca Mountain repository site. iii CONTENTS Section Page FIGURES .......................... vii TABLES ........................ viii ACKNOWLEDGMENTS .................. ix EXECUTIVE SUMMARY .................. x 1 INTRODUCTION .1-1 2 SITE CHARACTERIZATION .2-1 2.1 WASTE PACKAGE CONFIGURATION .2-1 2.2 CANDIDATE CONTAINMENT MATERIALS .2-1 2.3 ENVIRONMENT OUTSIDE THE WASTE PACKAGE .2-1 2.3.1 Geology .2-1 2.3.2 Hydrology .2-3 2.3.3 Water Chemistry .2-3 2.3.4 Radiation .2-5 2.3.5 Temperature .2-5 2.3.6 Moisture Content .2-6 2.4 ENVIRONMENT INSIDE CONTAINERS .2-6 3 BIOLOGICAL PROCESSES .3-1 3.1 THE UBIQUITOUS NATURE OF MICROORGANISMS .3-1 3.2 THE BIOFILM MODE OF GROWTH .3-2 4 CHARACTERISTICS OF MICROORGANISMS IN SUBSURFACE ENVIRONMENTS .4-1 4.1 INTRODUCTION .4-1 4.2 CHARACTERIZATION OF SPECIFIC SITES .4-2 4.2.1 Savannah River Plant Site .4-2 4.2.2 Idaho National Engineering Laboratory Site .4-3 4.2.3 Hanford Site .4-3 4.2.4 Nevada Test Site, Rainier Mesa . 44 4.2.5 Pajarito Plateau, New Mexico. 4-4 4.3 BIOTRANSFORMATION OF SUBSURFACE MICROORGANISMS .4-5 4.4 ANAEROBIC BIOTRANSFORMATIONS IN THE SUBSURFACE ENVIRONMENT....................................... 4-7 4.4.1 Anaerobic Biotransformations in the Deep Subsurface ..................... 4-8 4.4.2 Summary of Subsurface Microbiology .4-10 4.4.3 Environmental Parameters Affecting Subsurface Microbial Processes .4-10 4.4.3.1 Ionizing Radiation .4-11 4.4.3.2 Salinity ................................................. 4-11 4.4.3.3 Water Availability ........................................... 4-12 iv CONTENTS Section Page 4.4.3.4 Temperature .............................................. 4-13 4.4.3.5 Hydrogen Ion Concentration .................................... 4-15 4.4.3.6 Electron Acceptors and Redox Potential ............................. 4-15 4.4.3.7 Nutrient Availability ......... ................................ 4-16 4.4.4 Energy Requirements of Microorganisms in the Repository Environment .... ..... 4-18 4.4.5 Microbial Influence on the Integrity of Radioactive Waste Repositories: Near-field Effects . .................................................. 4-19 5 MICROBIALLY INFLUENCED CORROSION OF METALS ................ 5-1 5.1 INTRODUCTION ........................................... 5-1 5.2 MICROBIALLY INFLUENCED CORROSION OF MILD STEEL .... ......... 5-2 5.2.1 Factors Influencing MIC of Mild Steel ............................... 5-4 5.2.1.1 MIC of Mild Steel Under Anaerobic Conditions ......................... 5-4 5.2.1.2 MIC of Mild Steel Under Fluctuating Aerobic and Anaerobic Conditions .... ..... 5-6 5.2.1.3 Corrosion of Mild Steel by Iron-Reducing Bacteria ....................... 5-6 5.2.1.4 MIC of Mild Steel Under Aerobic Conditions .......................... 5-6 5.2.2 Influence of Microorganisms on Hydrogen Embrittlement and Stress Corrosion of Mild Steel ................................................. 5-8 5.2.3 Physical and Chemical Conditions for Corrosion of Mild Steel ................ 5-8 5.2.3.1 Anion Concentrations . ......................................... 5-8 5.2.3.2 High Salinity/Low Water Content .................................. 5-8 5.2.4 Container Corrosion Studies on Mild Steel and Summary ................... 5-9 5.3 MICROBIALLY INFLUENCED CORROSION OF COPPER AND COPPER ALLOYS . ................................................ 5-10 5.3.1 Corrosion and Fouling of Copper ................................. 5-10 5.3.2 Characteristics of Copper Corrosion in Freshwater Involving Microorganisms ..... 5-11 5.3.3 Factors Contributing to Microbially Influenced Pitting Corrosion of Pure Copper in Freshwater . .............................................. 5-14 5.3.3.1 Temperature . .............................................. 5-14 5.3.3.2 Water Chemistry ........................................... 5-14 5.3.4 MIC of Pure Copper in Marine Environments ......................... 5-15 5.3.5 Corrosion of Copper Alloys ..................................... 5-15 5.3.6 MIC of Copper Alloys in Marine Environments ........................ 5-16 5.3.6.1 Short-Term Experiments on MIC of Copper Alloys ...................... 5-16 5.3.6.2 Medium-Term Studies on MIC of Copper Alloys ....................... 5-17 5.3.6.3 Long-Term Studies of MIC of Copper Alloys .......................... 5-18 5.3.7 Summary of Fouling and Corrosion of Copper Alloys .................... 5-18 5.3.8 Proposed Mechanisms of MIC of Copper and Its Alloys ................... 5-19 5.3.8.1 Role of Microbial Exopolysaccharides in Localized MIC of Pure Copper .... .... 5-19 5.3.8.2 Mechanisms of Corrosion of Copper Alloys in Seawater ................... 5-20 5.3.9 Extrapolation of Copper Corrosion in Marine and Freshwater Systems to the Yucca Mountain Repository Site ...................................... 5-21 v CONTENTS Section Page 5.4 MICROBIALLY INFLUENCED CORROSION OF STAINLESS STEELS ... .... 5-22 5.4.1 Microbiological Reactions at the Metal Surface ......................... 5-24 5.4.2 Microbiological Reactions Distant from the Metal Surface .................. 5-26 5.4.3 Summary . ............................................... 5-26 5.5 MICROBIALLY INFLUENCED CORROSION OF NICKEL ALLOYS .... ..... 5-26 5.5.1 MIC of Commercial Nickel ..................................... 5-27 5.5.2 MIC of Nickel-Copper Alloys ................................... 5-29 5.5.2.1 Effect of Temperature on MIC of Monel ............................. 5-30 5.5.2.2 Effect of Chlorination on MIC of Monel ............................. 5-30 5.5.3 MIC of Nickel Alloys Containing High Levels of Chromium ................ 5-31 5.5.4 Summary . ............................................... 5-32 5.6 MICROBIALLY INFLUENCED CORROSION OF TITANIUM AND ITS ALLOYS .5-32 5.6.1 Superiority of Titanium Over Other Metals in Resistance to MIC ............. 5-33 5.6.2 Susceptibility of Titanium to Severe Microbial Environments .5-34 5.6.3 Possibility of Microbial Enhanced Hydrogen Embrittlement of Titanium .5-34 5.6.4 Possible Near-Field Effects ................................... 5-34 5.6.5 Titanium as an HLW Container Material . ............................ 5-35 6 RECOMMENDATIONS .6-1 6.1 GENERAL RECOMMENDATIONS .6-1 6.2 SPECIFIC RECOMMENDATIONS .6-1 6.3 SUMMARY OF KEY RESEARCH AREAS THAT NEED TO BE CONSIDERED ... 6-2 7 ABBREVIATIONS .7-1 8 GLOSSARY .8-1 9 REFERENCES .9-1 vi FIGURES Figure Page 3-1 Schematic showing successive stages in biofilm development ..... ............ 3-3 5-1 Schematic of the morphology and the various processes associated with Type 1 pitting corrosion of copper in stagnant, hard waters. In the same figure, variations corresponding to Type 2 pitting corrosion are also indicated. 5-12 5-2 Schematic illustrating the morphology of the unusual pitting corrosion of copper observed in the presence of bacteria. 5-13 vii TABLES Table Page 2-1 Nominal chemical compositions of current DOE candidate and selected alternate
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