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Title: The Integration and Abstracyion of EBS Models in Yucca Mountain Performance Assessment

Abstract

The safety strategy for geological disposal of radioactive waste at Yucca Mountain relies on a multi-barrier system to contain the waste and isolate it from the biosphere. The multi-barrier system consists of the natural barrier provided by the geological setting and the engineered barrier system (EBS). In the case of Yucca Mountain (YM) the geologic setting is the unsaturated-zone host rock, consisting of about 600 meters of layered ash-flow volcanic tuffs above the water table, and the saturated zone beneath the water table. Both the unsaturated and saturated rocks are part of a closed hydrologic basin in a desert surface environment. The waste is to be buried about halfway between the desert surface and the water table. The primary engineered barriers at YM consist of metal components that are highly durable in an oxidizing environment. The two primary components of the engineered barrier system are highly corrosion-resistant metal waste packages, made from a nickel-chromium-molybdenum alloy, Alloy 22, and titanium drip shields that protect the waste packages from corrosive dripping water and falling rocks. Design and performance assessment of the EBS requires models that describe how the EBS and near field behave under anticipated repository-relevant conditions. These models must describe coupledmore » hydrologic, thermal, chemical, and mechanical (THCM) processes that drive radionuclide transport in a highly fractured host rock, consisting of a relatively permeable network of conductive fractures in a setting of highly impermeable tuff rock matrix. An integrated performance assessment of the EBS must include a quantification of the uncertainties that arise from (1) incomplete understanding of processes and (2) from lack of data representative of the large spatial scales and long time scales relevant to radioactive waste disposal (e.g., long-term metal corrosion rates and heterogeneities in rock properties over the large 5 km{sup 2} emplacement area of the repository). A systematic approach to EBS model development and performance assessment should include as key elements: (1) implementation of a systematic FEPs approach, (2) quantification of uncertainty and variability, (3) sensitivity analyses, and (4) model validation and limitations. The approaches used for these key elements in the Yucca Mountain repository program are described in Section 2 of this paper. A specific example of Yucca Mountain EBS model development and integration, related to the modeling of localized corrosion of Alloy 22, is discussed in Sections 3 and 4.« less

Authors:
; ;
Publication Date:
Research Org.:
Yucca Mountain Project, Las Vegas, Nevada
Sponsoring Org.:
USDOE
OSTI Identifier:
894817
Report Number(s):
SAND2006-0172P
MOL.20061026.0022, DC# 46839; TRN: US0700413
DOE Contract Number:
NA
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; ALLOYS; BIOSPHERE; CORROSION; FRACTURES; IMPLEMENTATION; POSITIONING; RADIOACTIVE WASTE DISPOSAL; RADIOACTIVE WASTES; RADIOISOTOPES; SAFETY; SHIELDS; TITANIUM; TUFF; WASTES; WATER; WATER TABLES; YUCCA MOUNTAIN

Citation Formats

S.D. Sevougian, V. Jain, and A.V. Luik. The Integration and Abstracyion of EBS Models in Yucca Mountain Performance Assessment. United States: N. p., 2006. Web. doi:10.2172/894817.
S.D. Sevougian, V. Jain, & A.V. Luik. The Integration and Abstracyion of EBS Models in Yucca Mountain Performance Assessment. United States. doi:10.2172/894817.
S.D. Sevougian, V. Jain, and A.V. Luik. Wed . "The Integration and Abstracyion of EBS Models in Yucca Mountain Performance Assessment". United States. doi:10.2172/894817. https://www.osti.gov/servlets/purl/894817.
@article{osti_894817,
title = {The Integration and Abstracyion of EBS Models in Yucca Mountain Performance Assessment},
author = {S.D. Sevougian and V. Jain and A.V. Luik},
abstractNote = {The safety strategy for geological disposal of radioactive waste at Yucca Mountain relies on a multi-barrier system to contain the waste and isolate it from the biosphere. The multi-barrier system consists of the natural barrier provided by the geological setting and the engineered barrier system (EBS). In the case of Yucca Mountain (YM) the geologic setting is the unsaturated-zone host rock, consisting of about 600 meters of layered ash-flow volcanic tuffs above the water table, and the saturated zone beneath the water table. Both the unsaturated and saturated rocks are part of a closed hydrologic basin in a desert surface environment. The waste is to be buried about halfway between the desert surface and the water table. The primary engineered barriers at YM consist of metal components that are highly durable in an oxidizing environment. The two primary components of the engineered barrier system are highly corrosion-resistant metal waste packages, made from a nickel-chromium-molybdenum alloy, Alloy 22, and titanium drip shields that protect the waste packages from corrosive dripping water and falling rocks. Design and performance assessment of the EBS requires models that describe how the EBS and near field behave under anticipated repository-relevant conditions. These models must describe coupled hydrologic, thermal, chemical, and mechanical (THCM) processes that drive radionuclide transport in a highly fractured host rock, consisting of a relatively permeable network of conductive fractures in a setting of highly impermeable tuff rock matrix. An integrated performance assessment of the EBS must include a quantification of the uncertainties that arise from (1) incomplete understanding of processes and (2) from lack of data representative of the large spatial scales and long time scales relevant to radioactive waste disposal (e.g., long-term metal corrosion rates and heterogeneities in rock properties over the large 5 km{sup 2} emplacement area of the repository). A systematic approach to EBS model development and performance assessment should include as key elements: (1) implementation of a systematic FEPs approach, (2) quantification of uncertainty and variability, (3) sensitivity analyses, and (4) model validation and limitations. The approaches used for these key elements in the Yucca Mountain repository program are described in Section 2 of this paper. A specific example of Yucca Mountain EBS model development and integration, related to the modeling of localized corrosion of Alloy 22, is discussed in Sections 3 and 4.},
doi = {10.2172/894817},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 11 00:00:00 EST 2006},
month = {Wed Jan 11 00:00:00 EST 2006}
}

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