Effect of the Residual Heat Release of the Nuclear Waste Stored in an Unsaturated Zone on Radionuclide Release

2010 ◽  
Author(s):  
Lubna K. Hamdan ◽  
John C. Walton ◽  
Arturo Woocay
Keyword(s):  
Heat Release ◽  
Nuclear Waste ◽  
Unsaturated Zone ◽  
Yucca Mountain ◽  
Minimum Length ◽  
General Corrosion ◽  
Waste Package ◽  
Flow Through ◽  
Radionuclide Release ◽  
Residual Heat

Over time, nuclear waste packages disposed in geological repositories are expected to fail gradually due to localized and general corrosion. As a result, water will have access to the nuclear waste and radionuclides will be transported to the accessible environment by ground water. In this paper we consider a serious failure case in which penetrations at the top and bottom of the waste package will allow water to flow through it (flow-through model). We introduce a new conceptual model that examines the effect of the residual heat release of the nuclear waste stored in an unsaturated environment on radionuclide release. This model predicts that the evaporation of water at the hotter sheltered areas (from condensate and seepage) inside the failed waste package will create a capillary pressure gradient that drives water to wick with its dissolved and suspended contents toward these relict areas, effectively preventing radionuclides release. We drive a dimensionless group to estimate the minimum length of the sheltered areas required to sequester radionuclides and prevent their release. The implications of this model on the performance of the proposed repository at Yucca Mountain or unsaturated zone geological repositories in general are explored.

Zircaloy Corrosion in a Repository Environment

1999 ◽  
Vol 556 ◽  
Author(s):  
Jerry D. Christian
Keyword(s):  
Spent Nuclear Fuel ◽  
Near Field ◽  
Yucca Mountain ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Geochemical Environment ◽  
Waste Package ◽  
Saturated Water ◽  
Radionuclide Release ◽  
Corrosion Data

AbstractAssessments are made of the corrosion characteristics of spent nuclear fuel Zircaloy cladding in a Yucca mountain repository environment and the potential for the cladding to provide protection against radionuclide release following waste package failure. Considerations and assumptions includes a waste package life near 10,000 years and air-saturated water contacted with waste package corrosion product goethite, based on the near-field geochemical environment evaluated in the Yucca Mountain Viability Assessment [3]. Literature corrosion data (general, pitting, and localized crevice attack) are evaluated on the basis of these conditions and the expected chemical environments that can result on the surface of the fuel. General corrosion of Zircaloy is expected to be negligible and result in a lifetime of the SNF cladding of several hundred thousand years, approaching a million years. General surface pitting is not expected. Effects of crevice localized corrosion for periods beyond 10,000 years are uncertain and require modeling development and experimental characterization. Details of the evaluations that provide the basis for the conclusions are presented.

Integrated Analysis for Long-Term Degradation of Waste Package at the Potential Yucca Mountain Repository for High-Level Nuclear Waste Disposal

2002 ◽  
Vol 713 ◽  
Author(s):  
Joon H. Lee ◽  
Kevin G. Mon ◽  
Dennis E. Longsine ◽  
Bryan E. Bullard ◽  
Ahmed M. Moniba
Keyword(s):  
Corrosion Rate ◽  
Nuclear Waste ◽  
Yucca Mountain ◽  
Integrated Analysis ◽  
Total System ◽  
General Corrosion ◽  
Waste Package ◽  
High Level Nuclear Waste ◽  
High Level

ABSTRACTThe technical basis for Site Recommendation (SR) of the potential repository for high-level nuclear waste at Yucca Mountain, Nevada has been completed. Long-term containment of the waste and subsequent slow release of radionuclides from the engineered barrier system (EBS) into the geosphere will rely on a robust waste package (WP) design, among other EBS components as well as the natural barrier system. The WP and drip shield (DS) degradation analyses for the total system performance assessment (TSPA) baseline model for the SR have shown that, based on the current corrosion models and assumptions, both the DSs and WPs do not fail within the regulatory compliance time period (10,000 years). From the perspective of initial WP failure time, the analysis results are encouraging because the upper bounds of the baseline case are likely to represent the worst case combination of key corrosion model parameters that significantly affect long-term performance of WPs in the potential repository. The estimated long life-time of the WPs in the current analysis is attributed mostly to the following two factors that delay the onset of stress corrosion cracking (SCC): (1) the stress mitigation to substantial depths from the outer surface in the dual closure-lid weld regions; and (2) the very low general-corrosion rate applied to the closure-lid weld regions to corrode the compressive stress zones. Uncertainties are associated with the current WP SCC analysis. These are stress mitigation on the closure-lid welds, characterization of manufacturing flaws applied to SCC, and general corrosion rate applied to the closurelid weld regions. These uncertainties are expected to be reduced as additional data and analyses are developed.

Design by Analysis of Waste Packages at Yucca Mountain for Impact Loads

2009 ◽  
Author(s):  
Randy J. James ◽  
Kenneth Jaquay ◽  
Michael J. Anderson
Keyword(s):  
Nuclear Waste ◽  
Impact Loading ◽  
Structural Integrity ◽  
Structural Response ◽  
Yucca Mountain ◽  
Impact Loads ◽  
Geologic Repository ◽  
Dynamic Simulations ◽  
Nuclear Waste Storage ◽  
Waste Package

The proposed geologic repository under development at Yucca Mountain, Nevada, will employ multiple shell metallic containers (waste packages) for the disposal of nuclear waste. The waste packages represent a primary engineered barrier for protection and containment of the radioactive waste, and the design of these containers must consider a variety of structural conditions to insure structural integrity. Some of the more challenging conditions for structural integrity involve severe impact loading due to hypothesized event sequences, such as drops or collisions during transport and placement. Due to interactions between the various components leading to complex structural response during an impact sequence, nonlinear explicit dynamic simulations and highly refined models are employed to qualify the design for these severe impact loads. This paper summarizes the Design by Analysis methodologies employed for qualification of waste package design under impact loading and provides several illustrative examples using these methods. Example evaluations include a collision of a waste package by the Transport and Emplacement Vehicle (TEV) and two scenarios due to seismic events, including WP impact within the TEV and impact by falling rock. The examples are intended to illustrate the stringent Design by Analysis methods employed and also highlight the scope of structural conditions included in the design basis for waste packages to be used for proposed nuclear waste storage at Yucca Mountain.

scholarly journals The Proposed Yucca Mountain Repository from a Corrosion Perspective

2006 ◽  
Vol 932 ◽  
Author(s):  
Joe H. Payer
Keyword(s):  
Corrosion Resistance ◽  
Nuclear Waste ◽  
Yucca Mountain ◽  
Department Of Energy ◽  
Process Models ◽  
Localized Corrosion ◽  
Waste Package ◽  
Advanced Technologies ◽  
The U.S

ABSTRACTIn this paper, the proposed Yucca Mountain Repository is viewed from a corrosion perspective. A major component of the long-term strategy for safe disposal of nuclear waste at the Yucca Mountain Repository is first to completely isolate the radionuclides in the waste packages for long times and to greatly retard the egress and transport of radionuclides from penetrated packages. Therefore, long-lived waste packages are important. The corrosion resistance of the waste package outer canister is reviewed, and a framework for the analysis of localized corrosion processes is presented. An overview is presented of the Materials Performance targeted thrust of the U.S. Department of Energy/Office of Civilian Radioactive Waste Management's Office of Science and Technology and International. The thrust program strives for increased scientific understanding, enhanced process models and advanced technologies for corrosion control.

Preferential Radionuclide Release Due to Alpha Decay: Effects on Repository Performance

2004 ◽  
Vol 824 ◽  
Author(s):  
David A. Pickett ◽  
William M. Murphy
Keyword(s):  
Nuclear Waste ◽  
Spent Nuclear Fuel ◽  
Alpha Decay ◽  
Nuclear Regulatory Commission ◽  
Yucca Mountain ◽  
Total System ◽  
Secondary Phases ◽  
Regulatory Commission ◽  
Radionuclide Release ◽  
The U.S

AbstractWe model preferential release of 237Np, 234U, 230Th, 226Ra, and 210Pb from disposed commercial spent nuclear fuel as a result of alpha recoil damage, using the U.S. Nuclear Regulatory Commission (NRC) Total-system Performance Assessment (TPA) model for the potential repository at Yucca Mountain. Time-dependent augmentation of the ingrown component is simulated by increasing the initial parent inventory; we have used a factor of five increase, based on natural system observations. For 237Np, the magnitude of preferential release is subject to solubility limits. Stochastic TPA runs show a significant effect on modeled dose of preferential 237Np release, but low impact from the other four radionuclides. The mechanism could be ineffective if 237Np is incorporated into secondary phases. While our results are exploratory in nature, this approach to modeling decay-related enhancement of release can be applied in other nuclear waste disposal settings.

scholarly journals Review of Corrosion Modes For Alloy 22 Regarding Lifetime Expectancy of Nuclear Waste Containers

2002 ◽  
Vol 757 ◽  
Author(s):  
Raúl B. Rebak ◽  
John C. Estill
Keyword(s):  
Corrosion Rate ◽  
Nuclear Waste ◽  
Outer Layer ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Corrosion Resistant ◽  
Waste Package ◽  
Environmentally Assisted Cracking ◽  
Alloy 22 ◽  
Lifetime Expectancy

ABSTRACTAlloy 22 (UNS N06022) was selected to fabricate the corrosion resistant outer barrier of a two-layer nuclear waste package container. This paper reviews the main corrosion degradation modes that are predicted for the outer layer of the container. Current results show that the containers would perform well under general corrosion, localized corrosion and environmentally assisted cracking (EAC). For example, the general corrosion rate is expected to be below 100 nm/year and the container is predicted to be outside the range of potential for localized corrosion and environmentally assisted cracking.

scholarly journals A Quantitative Assessment of Microbiological Contributions to Corrosion of Candidate Nuclear Waste Package Materials

1999 ◽  
Vol 556 ◽  
Author(s):  
T. Lian ◽  
S. Martin ◽  
J. Horn ◽  
D. Jones
Keyword(s):  
Corrosion Rate ◽  
Nuclear Waste ◽  
Fold Increase ◽  
Yucca Mountain ◽  
Department Of Energy ◽  
Microbiologically Influenced Corrosion ◽  
304 Stainless Steel ◽  
Detection Methods ◽  
Nuclear Waste Repository ◽  
Waste Package

AbstractThe U.S. Department of Energy is contributing to the design of a potential nuclear waste repository at Yucca Mountain, Nevada. A system to predict the contribution of Yucca Mountain (YM) bacteria to overall corrosion rates of candidate waste package (WP) materials was designed and implemented. DC linear polarization resistance techniques were applied to candidate material coupons that had been inoculated with a mixture of YM-derived bacteria with potentially corrosive activities, or left sterile. Inoculated bacteria caused a 5- to 6-fold increase in corrosion rate of carbon steel C 1020 (to approximately 7-8μm/yr), and an almost 100-fold increase in corrosion rate of Alloy 400 (to approximately μm/yr) was observed due to microbiological activities. Microbiologically Influenced Corrosion (MIC) rates on more resistant materials (CRMs: Alloy 625, Type 304 Stainless Steel, and Alloy C22) were on the order of hundredths of micrometers per year (μm/yr). Bulk chemical and surfacial endpoint analyses of spent media and coupon surfaces showed preferential dissolution of nickel from Alloy 400 coupons and depletion of chromium from CRMs after incubation with YM bacteria. Scanning electron microscopy also showed greater damage to the Alloy 400 surface than that indicated by electrochemical detection methods.

Unsaturated Zone Waters From the Nopal I Natural Analog, Chihuahua, Mexico - Implications for Radionuclide Mobility at Yucca Mountain

1999 ◽  
Vol 556 ◽  
Author(s):  
David A. Pickett ◽  
William M. Murphy
Keyword(s):  
Unsaturated Zone ◽  
Yucca Mountain ◽  
Nuclear Waste Repository ◽  
Spent Fuel ◽  
Path Modeling ◽  
Rock Interaction ◽  
Colloidal Transport ◽  
Natural Analog ◽  
Initial Silica ◽  
Radionuclide Release

AbstractChemical and U-Th isotopic data on unsaturated zone waters from the Nopal I natural analog reveal effects of water-rock interaction and help constrain models of radionuclide release and transport at the site and, by analogy, at the proposed nuclear waste repository at Yucca Mountain. Geochemical reaction-path modeling indicates that, under oxidizing conditions, dissolution of uraninite (spent fuel analog) by these waters will lead to eventual schoepite precipitation regardless of initial silica concentration provided that groundwater is not continuously replenished. Thus, less soluble uranyl silicates may not dominate the initial alteration assemblage and keep dissolved U concentrations low. Uranium-series activity ratios are consistent with models of U transport at the site and display varying degrees of leaching versus recoil mobilization. Thorium concentrations may reflect the importance of colloidal transport of low-solubility radionuclides in the unsaturated zone.

Sign in / Sign up

Export Citation Format

Share Document