Safety concept, FEP catalogue and scenario development as fundamentals of a long-term safety demonstration for high-level waste repositories in German clay formations

2018 ◽  
Vol 482 (1) ◽  
pp. 313-329 ◽  
Author(s):  
A. Lommerzheim ◽  
M. Jobmann ◽  
A. Meleshyn ◽  
S. Mrugalla ◽  
A. Rübel ◽  
...  
Keyword(s):  
System Analysis ◽  
Selection Process ◽  
High Level Waste ◽  
Reference Scenario ◽  
Safety Concept ◽  
Scenario Development ◽  
Future System ◽  
Alternative Scenarios ◽  
High Level ◽  
Waste Repositories

AbstractA safety concept and a safety demonstration concept for the disposal of high-level radioactive waste in German clay formations have been developed. The main safety objective is to retain the radionuclides inside a ‘Containment Providing Rock Zone’. Thus, the radionuclide transport should be restrained by adequate safety functions of the geological and geotechnical barriers. The compliance with legal dose constraints has to be demonstrated for probable evolutions and less probable evolutions.As a basis for system analysis, generic geological reference models, disposal concepts and repository designs have been developed for northern and southern Germany. All data relevant for future system evolution were compiled in two FEP (features, events and processes) catalogues. They provide information on FEP characteristics, their probabilities of occurrence, their interactions and identify ‘initial FEP’ that impair the safety functions of relevant barriers. A probable reference scenario has been deduced systematically from the probable ‘initial FEP’, and from probable processes relevant for radionuclide mobilization and transport. Four different starting points to develop alternative scenarios (i.e. less probable evolutions) were identified.The scenario development methodology is applicable to different kinds of host rock and therefore may be a basis for the preliminary safety analyses necessary in the future site selection process in Germany.

scholarly journals Spent Fuel as a Waste Form - Data Needs to Allow Long Term Performance Assessment Under Repository Disposal Conditions.

1986 ◽  
Vol 84 ◽  
Author(s):  
V. M. Oversby
Keyword(s):  
Performance Assessment ◽  
Waste Form ◽  
High Level Waste ◽  
Detailed Knowledge ◽  
Spent Fuel ◽  
Expected Performance ◽  
High Level ◽  
Term Performance ◽  
Physical And Chemical ◽  
Waste Repositories

AbstractPerformance assessment calculations are required for high level waste repositories for a period of 10,000 years under NRC and EPA regulations. In addition, the Siting Guidelines (IOCFR960) require a comparison of sites following site characterization and prior to final site selection to be made over a 100,000 year period. In order to perform the required calculations, a detailed knowledge of the physical and chemical processes that affect waste form performance will be needed for each site. While bounding calculations might be sufficient to show compliance with the requirements of IOCFR60 and 40CFRI91, the site comparison for 100,000 years will need to be based on expected performance under site specific conditions. The only case where detailed knowledge of waste form characteristics in the repository would not be needed would be where radionuclide travel times to the accessible environment can be shown to exceed 100,000 years. This paper will review the factors that affect the release of radionuclides from spemt fuel under repository conditions, summarize our present state of knowledge, and suggest areas where more work is needed in order to support the performance assessment calculations.

Assessment of Redox Conditions in the Near Field of Nuclear Waste Repositories: Application to the Swiss high-level and intermediate level waste disposal concept

2003 ◽  
Vol 807 ◽  
Author(s):  
Paul Wersin ◽  
Lawrence H. Johnson ◽  
Bernhard Schwyn
Keyword(s):  
Solid Phase ◽  
Near Field ◽  
Intermediate Level ◽  
Redox Conditions ◽  
High Level Waste ◽  
Redox Potentials ◽  
Spent Fuel ◽  
Reducing Conditions ◽  
High Level ◽  
Waste Repositories

ABSTRACTRedox conditions were assessed for a spent fuel and high-level waste (SF/HLW) and an intermediate-level waste (ILW) repository. For both cases our analysis indicates permanently reducing conditions after a relatively short oxic period. The canister-bentonite near field in the HLW case displays a high redox buffering capacity because of expected high activity of dissolved and surface-bound Fe(II). This is contrary to the cementitious near field in the ILW case where concentrations of dissolved reduced species are low and redox reactions occur primarily via solid phase transformation processes.For the bentonite-canister near field, redox potentials of about -100 to -300 mV (SHE) are estimated, which is supported by recent kinetic data on U, Tc and Se interaction with reduced iron systems. For the cementitious near field, redox potentials of about -200 to -800 mV are estimated, which reflects the large uncertainties related to this alkaline environment.

Optimal mixing scheme for graphite–bentonite mixtures used as buffer materials in high-level waste repositories

2021 ◽  
Vol 80 (17) ◽  
Author(s):  
Yun-zhi Tan ◽  
Zi-yang Xie ◽  
Fan Peng ◽  
Fang-hong Qian ◽  
Hua-jun Ming
Keyword(s):  
High Level Waste ◽  
High Level ◽  
Waste Repositories ◽  
Optimal Mixing

Which Processes could define Temperature Limits on the Outer Surface of a Container in a Disposal Facility ?

2020 ◽  
Author(s):  
Guido Bracke ◽  
Eva Hartwig-Thurat ◽  
Jürgen Larue ◽  
Artur Meleshyn ◽  
Torben Weyand ◽  
...  
Keyword(s):  
Outer Surface ◽  
Site Selection ◽  
Selection Process ◽  
Temperature Limit ◽  
Crystalline Rock ◽  
Safety Concept ◽  
Disposal Facility ◽  
High Level ◽  
A Site ◽  
Host Rocks

<p>When the recommencement of the search for and selection of a site for a disposal facility for HLRW in Germany was stipulated by the Site Selection Act (StandAG 2017) in 2017, a <strong>precautionary </strong>temperature limit of 100 °C on the outer surface of the containers with high-level radioactive waste in the disposal facility section was set. This <strong>precautionary </strong>temperature limit shall be applied in preliminary safety analyses provided that the “maximum physically possible temperatures” in the respective host rocks have not yet been determined due to pending research. Therefore, this issue is addressed and discussed in this paper, contributing to “pending research” by a review of the literature.</p><p>This presentation briefly discusses a few examples of thermohydraulical, mechanical, chemical and biological processes in a disposal facility, because temperature limits are derived based on safety impacts regarding THMCB-processes. The temperature-dependent processes have been extracted from databases for features, events and processes (FEP-databases). Furthermore, it is dicussed if the feasibility to retrieve and recover HLRW is hampered at high temperatures.</p><p>It is concluded that a design temperature concerning single components of a disposal facility for the preservation of their features can be derived when a safety concept is established. However, the interactions of all relevant processes in a disposal concept must be considered to determine a specific temperature limit for the outer surface of the containers. Therefore, applicable temperature limits may vary for particular safety and disposal concepts in the following host rocks: rock salt, clay stone and crystalline rock.</p><p>Technical solutions for retrieval and design options for recovery seem to be viable up to temperatures of 200 °C with different, sometimes severe, downsides according to expert judgement.</p><p>It is summarized that emperature limits regarding the outer surface of the containers can be derived specifically for each safety concept and design of the disposal facility in a host rock. General temperature limits without reference to specific safety concepts or the particular design of the disposal facility may narrow down the possibilities for optimisation of the disposal facility and could adversely affect the site selection process in finding the best suitable site.</p>

scholarly journals Is it Possible to Demonstrate Compliance with the Regulations for High-Level-Waste Repositories?

1992 ◽  
Vol 294 ◽  
Author(s):  
Felton W. Bingham
Keyword(s):  
Numerical Modeling ◽  
Data Collection ◽  
Performance Assessments ◽  
High Level Waste ◽  
Spent Fuel ◽  
Distant Future ◽  
Site Investigations ◽  
High Level ◽  
Waste Repositories ◽  
Shed Light

ABSTRACTThe regulations that currently govern repositories for spent fuel and high-level waste require demonstrations that are sometimes described as impossible to make. To make them will require an understanding of the current and the future phenomena at repository sites; it will also require credible estimates of the probabilities that the phenomena will occur in the distant future. Experts in many fields—earth sciences, statistics, numerical modeling, and the law—have questioned whether any amount of data collection can allow modelers to meet these requirements with enough confidence to satisfy the regulators. In recent years some performance assessments have begun to shed light on this question because they use results of actual site investigations. Although these studies do not settle the question definitively, a review of a recent totalsystem assessment suggests that compliance may be possible to demonstrate. The review also suggests, however, that the demonstration can be only at the “reasonable” levels of assurance mentioned, but not defined, in the regulations.

scholarly journals Site suitability criteria for solidified high level waste repositories

1979 ◽  
Author(s):  
R.A. Heckman ◽  
T. Holdsworth ◽  
D. Isherwood ◽  
D.F. Towse ◽  
N.L. Dayem
Keyword(s):  
High Level Waste ◽  
Site Suitability ◽  
High Level ◽  
Waste Repositories

scholarly journals A Transport Code for Radiocolloid Migration: With an Assessment of an Actual Low-Level Waste Site

1984 ◽  
Vol 44 ◽  
Author(s):  
Bryan J. Travis ◽  
H. E. Nuttall
Keyword(s):  
High Level Waste ◽  
Waste Site ◽  
Low Level ◽  
Transport Code ◽  
Experimental Laboratory ◽  
Rapid Transport ◽  
High Level ◽  
Waste Repositories ◽  
Low Level Radioactive Waste

AbstractRecently, there is increased concern that radiocolloids may act as a rapid transport mechanism for the release of radionuclides from high-level waste repositories. The role of colloids is, however, controversial because the necessary data and assessment methodology have been limited. To quantitatively assess the role of colloids, the TRACR3D transport code has been enhanced by the addition of the population balance equations. The code was tested against the experimental laboratory column data of Avogadro et al. Next a low-level radioactive waste site was investigated to explore whether colloid migration could account for the unusually rapid transport of plutonium and americium observed. The nature and modeling of radiocolloids are discussed along with site simulation results from the TRACR3D code.

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