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At least 595 records · Page 33

Groundwater Pathway Model for the Los Alamos National Laboratory Technical Area 21, Material Disposal Area T

This report consists of four major sections, including this introductory section. Section 2 provides an overview of previous investigations related to the development of the current sitescale model. The methods and data used to develop the 3-D groundwater model and the techniques used to distill that model into a form suitable for use in the GoldSim models are discussed in Section 3. Section 4 presents the results of the model development effort and discusses some of the uncertainties involved. Three attachments that provide details about the components and data used in this groundwater pathway model are also included with this report.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Groundwater Pathway Model for the Los Alamos National Laboratory Technical Area 54, Area G, Revision 1

This report consists of four major sections, including this introductory section. Section 2 provides an overview of previous investigations related to the development of the current sitescale model. The methods and data used to develop the 3-D groundwater model and the techniques used to distill that model into a form suitable for use in the GoldSim models are discussed in Section 3. Section 4 presents the results of the model development effort and discusses some of the uncertainties involved. Eight attachments that provide details about the components and data used in this groundwater pathway model are also included with this report. The groundwater modeling effort reported here is a revision of the work that was conducted in 2005 (Stauffer et al., 2005a) in support of the 2008 Area G performance assessment and composite analysis (LANL, 2008). The revision effort was undertaken primarily to incorporate new geologic information that has been collected since 2003 at, and in the vicinity of, Area G. The new data were used to create a more accurate geologic framework model (GFM) that forms the basis of the numerical modeling of the site’s long-term performance. The groundwater modeling uses mean hydrologic properties of the geologic strata underlying Area G; this revision includes an evaluation of the impacts that natural variability in these properties may have on the model projections.

58 GEOSCIENCES↗

Neutron Tomography at the Los Alamos Neutron Science Center

Neutron imaging is an incredibly powerful tool for non-destructive sample characterization and materials science. Neutron tomography is one technique that results in a three-dimensional model of the sample, representing the interaction of the neutrons with the sample. This relies both on reliable data acquisition and on image processing after acquisition. Over the course of the project, the focus has changed from the former to the latter, culminating in a large-scale reconstruction of a meter-long fossilized skull. The full reconstruction is not yet complete, though tools have been developed to improve the speed and accuracy of the reconstruction. This project helps to improve the capabilities of LANSCE and LANL with regards to imaging large or unwieldy objects.

36 MATERIALS SCIENCE↗

Dose Assessment of Los Alamos National Laboratory-Derived Residual Radionuclides in Soils within Tract A-18-2 for Land Conveyance and Transfer Decisions

In 2017, soil sampling for radiological materials was conducted within Tract A-18-2 specifically for land conveyance decisions. Measurements of radionuclides in soil samples were evaluated against a recreational use scenario, and all measurements were below screening action levels for each radionuclide. The total estimated dose was less than 1 mrem/y (< 10 μSv/y) for a hypothetical recreational user (compared to a dose limit of 25 mrem/y (250 μSv/y)). Dose estimates were based on the 95% upper confidence limits for radionuclide concentrations within the Tract. Additionally, dose estimates less than 3 mrem/y are considered to be As Low As Reasonably Achievable, so no follow-up analysis was conducted. Release of this property is consistent with the requirements of DOE Order 458.1 and Policy 412.

54 ENVIRONMENTAL SCIENCES↗

LANSCE: Los Alamos Neutron Science Center

The principle goals of this project is to increase flux and improve resolution for neutron energies above 1 keV for nuclear physics experiments; and preserve current strong performance at thermal energies for material science.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Hydrogeochemical Investigation of Recharge Pathways to Intermediate and Regional Groundwater in Canon de Valle and Technical Area 16, Los Alamos National Laboratory

In aquifers consisting of fractured or porous igneous rocks, as well as conglomerate and sandstone products of volcanic formations, silicate minerals actively dissolve and precipitate (Eby, 2004; Eriksson, 1985; Drever, 1982). Dissolution of hydrated volcanic glass is also known to influence the character of groundwater to which it is exposed (White et al., 1980). Hydrochemical evolution, within saturated zones of volcanic formations, is modeled here as a means to resolve the sources feeding a perched groundwater zone. By observation of solute mass balances in groundwater, together with rock chemistry, this study characterizes the chemical weathering processes active along recharge pathways in a mountain front system. Inverse mass balance modeling, which accounts for mass fluxes between solid phases and solution, is used to contrive sets of quantitative reactions that explain chemical variability of water between sampling points. Model results are used, together with chloride mass balance estimation, to evaluate subsurface mixing scenarios generated by further modeling. Final model simulations estimate contributions of mountain block and local recharge to various contaminated zones.

54 ENVIRONMENTAL SCIENCES↗

Status of Federally Listed Threatened and Endangered Species at Los Alamos National Laboratory

Compliance with the Endangered Species Act at LANL is achieved through the implementation of the LANL Threatened and Endangered Species Habitat Management Plan (HMP; LANL 2017a). This plan is a formal agreement between the U.S. Department of Energy (DOE)/National Nuclear Security Administration (NNSA) and the U.S. Fish and Wildlife Service for the management of endangered species and their habitats at LANL. Actions and activities approved in the HMP were reviewed by the U.S. Fish and Wildlife Service and do not require further consultations. Projects that cannot follow the HMP requirements must go through separate section 7 consultations. The controls for Endangered Species Act compliance are incorporated into an internal project review process through which all LANL projects are reviewed for environmental compliance (LANL 2017b).

54 ENVIRONMENTAL SCIENCES↗