Long-term surveillance plan for the Mexican Hat disposal site Mexican Hat, Utah

The UK Low Level Waste Repository Ltd submitted an Environmental Safety Case for the disposal of low-level waste (LLW) to the Environment Agency on the 1st of May 2011. The Environmental Safety Case (ESC) presents a complete case for the environmental safety of the Low Level Waste Repository (LLWR) both during operations and in the long term (Cummings et al, in these proceedings). This includes an assessment of the long-term radiological safety of the facility, including an assessment of the potential consequences of human intrusion at the site. The human intrusion assessment is based on a cautiously realistic approach in defining intrusion cases and parameter values. A range of possible human intrusion events was considered based on present-day technologies and credible future uses of the site. This process resulted in the identification of geotechnical investigations, a housing development and a smallholding as requiring quantitative assessment. A particular feature of the site is that, because of its proximity to the coast and in view of expected global sea-level rise, it is vulnerable to coastal erosion. During such erosion, wastes and engineered barrier materials will be exposed, and could become targets for investigation or recovery. Therefore, human intrusion events have been included that are associated with such activities. A radiological assessment model has been developed to analyse the impacts of potential human intrusion at the site. A key feature of the model is the representation of the spatial layout of the disposal site, including the engineered cap design and the large-scale spatial heterogeneity of radionuclide concentrations within the repository. The model has been used to calculate the radiation dose to intruders and to others following intrusion at different times and at different locations across the site, for the each of the selected intrusion events, considering all relevant exposure modes. Potential doses due to radon and its daughters in buildings constructed on excavated spoil from the repository are a particular concern. Options for managing the emplacement of the radium-bearing waste packages with regard to human intrusion have been assessed. These calculations show that a managed waste emplacement strategy can ensure that calculated doses are consistent with regulatory guidance levels.

Download Full-text

Source Term Development For Tritium at the Sheffield Disposal Site

MRS Proceedings ◽

10.1557/proc-44-961 ◽

1984 ◽

Vol 44 ◽

Author(s):

D. R. Mackenzie ◽

R. E. Barletta ◽

J. F. Smalley ◽

C. R. Kempf ◽

R. E. Davis

Keyword(s):

Radioactive Waste ◽

Waste Disposal ◽

Source Term ◽

Fuel Cycle ◽

Radioactive Waste Disposal ◽

Disposal Site ◽

Waste Disposal Site ◽

Groundwater Samples ◽

Low Level Radioactive Waste

AbstractThe Sheffield low-level radioactive waste disposal site, which ceased operation in 1978, has been the focus of modeling efforts by the NRC for the purpose of predicting long-term site behavior. To provide the NRC with information required for its modeling effort, a study to define the source term for tritium in eight trenches at the Sheffield site has been undertaken. Tritium is of special interest since significant concentrations of the isotope have been found in groundwater samples taken at the site and at locations outside the original site boundary. Previous estimates of tritium site inventory at Sheffield are in wide disagreement. In this study, the tritium inventory in the eight trenches was estimated by reviewing the radioactive shipping records (RSRs) for waste buried in these trenches. It has been found that the tritium shipped for burial at the site was probably higher than previously estimated. In the eight trenches surveyed, which amount to roughly one half the total volume and activity buried at Sheffield, approximately 2350 Ci of tritium from non-fuel cycle sources were identified.

Download Full-text

Modelling of a Generic Near-Surface Disposal System

MRS Proceedings ◽

10.1557/opl.2012.613 ◽

2012 ◽

Vol 1475 ◽

Author(s):

Noelia R. Sileo ◽

Néstor O. Fuentes

Keyword(s):

Performance Assessment ◽

Waste Disposal ◽

Near Field ◽

Simple Calculation ◽

Radioactive Waste Disposal ◽

Disposal Site ◽

Near Surface ◽

License Application ◽

Numerical Tools

ABSTRACTDevelopment of numerical tools for performance assessment studies of radioactive waste disposal facilities, must address the management of the wide-ranging uncertainties associated with the long-term behaviour of these complex systems. Different approaches and assumptions are made in order to identify and describe relationships between the disposal system and its environment. They take into account, among other factors, the uncertainties associated with temporal evolution of the system within a proposed scenario; the landscape changes arising from future human actions, climate and geological events and processes; the relationships between components of the disposal system and its immediate environment; the behaviour and characteristics of radionuclides within the system and their role in contributing to radiation exposure. In all cases, the different scenario-based models are typically used to determine the radiological significance of potential future discharges from waste disposal facilities. However, it is important to keep always in mind that in any specific case, the purpose of developing and/or applying a model may vary from a simple calculation (e.g. to support concept development) to detailed site-specific performance assessment in support of a disposal license application. The assumptions and modelling simplifications that are appropriate to one type of calculation may not be so easily justified in different circumstances. In order to develop the capability of modelling different long-term scenarios for a generic disposal site for low and intermediate level radioactive wastes, implementation of models of both the near-field/geosphere and biosphere were performed using general approaches for geosphere-biosphere interface, with sub-models for the whole system.

Download Full-text

NUMO’s Open Solicitation of Volunteer Municipalities for a Potential Disposal Site

9th ASME International Conference on Radioactive Waste Management and Environmental Remediation: Volumes 1, 2, and 3 ◽

10.1115/icem2003-4584 ◽

2003 ◽

Author(s):

Kazumi Kitayama

Keyword(s):

Radioactive Waste ◽

Preliminary Investigation ◽

Disposal Site ◽

Nuclear Waste Management ◽

The Public ◽

Construction Operation ◽

High Level ◽

Year 2000 ◽

Selection Of

In the year 2000, the Japanese geological disposal program for high-level radioactive waste (HLW) moved from the phase of generic research and development into the phase of implementation. Following legislation entitled the “Specified Radioactive Waste Final Disposal Act” (hereafter “the Act”), the Nuclear Waste Management Organization of Japan (NUMO) was established as the implementing organization in October 2000. The assigned activities of NUMO include repository site selection, developing relevant license applications and construction, operation and closure of the repository. To initiate the first stage, NUMO has chosen an “open solicitation” approach for finding candidate sites in the belief that the support of local communities is essential to the success of this highly public, long-term project extending over more than a century. Based on this concept, NUMO announced the start of open solication for volunteer municipalities for selection of Preliminary Investigation Areas to the public on December 19, 2002. This paper describes NUMO’s open solicitation of volunteer municipalities for a potential disposal site.

Download Full-text