Environmental Radiochemistry

LLNL researchers predict the movement of radioactive isotopes above and below Earth’s surface, fostering long-term environmental stewardship.

A key focus of environmental research at LLNL involves studying the behavior of actinides in order to better understand how to foster long-term stabilization of this highly toxic, radioactive material.

Plutonium is the most abundant and chemically complex anthropogenic actinide. Since the dawn of the nuclear era, the inventory of plutonium in our environment has increased dramatically as a result of nuclear weapons production and testing, nuclear accidents, and inadequate waste management practices. In addition to being highly toxic, plutonium has been shown to migrate in the environment—in soil, as well as in rivers, streams, and groundwater.

Understanding actinide transport through field observations and experiments

Our research includes lab-based experiments, field observations, and computational models aimed at understanding the behavior of actinides.

  • Experiments provide quantitative data regarding the affinities, kinetics, and morphology of actinide associations with mineral surfaces, organic matter, and microbes.
  • Field observations provide direct evidence of the behavior of actinides in the environment at sites that represent diverse environmental challenges.
  • Conceptual models, based on our findings from both field and laboratory studies, enable us to predict actinide migration in the environment.
Examples of field sites: an estuary, two ponds, and the vadose. Click to view larger image. zone
The field sites where LLNL scientists study actinide mobility represent different ecosystems, with known variations in contamination history, providing insight regarding a range of potential remediation strategies.

Our field observations take place at sites representing diverse ecosystems, enabling us to study the connection between specific environmental conditions and actinide mobility. Our field sites include:

  • Water drainage ponds at a nuclear testing site (Nevada National Security Site, Nevada, USA).
  • Reactor cooling ponds linked to a river system (Savannah River Site, South Carolina, USA).
  • An estuary located near a processing facility, where freshwater meets seawater (Ravenglass Estuary, United Kingdom).
  • A waste site in the vadose zone, where flow rates and chemical reactions typically control how rapidly contaminants enter groundwater (Hanford Site, Washington, USA).
  • Carbonate rock that is being investigated as a potential repository for nuclear waste (Israel)

Biogeochemical processes can foster long-term actinide stabilization

Our research teams explore biogeochemical mechanisms that impact long-term stabilization or mobilization of actinides. For example, biologically mediated mineral transformations may lead to long-term stabilization of actinides in sediments. In addition, we study the relationship between actinide movement and various environmental drivers, including the microbiome, mineral redox cycling, and co-precipitation of minerals and actinides.

Examples of sorption/desorption, redox transformation, and aqueous complexation. Click to view larger image.
One key to long-term stabilization of actinides may be found at the intersection of sediment, the microbiome, and mineral surfaces, where biogeochemical processes influence how far and how fast actinides move in the environment.

Plutonium can migrate while associated with microscopic particles known as colloids, which can be composed of organic material, inorganic minerals, or microbes. LLNL scientists explore how plutonium adheres to colloids, which are found in groundwater, rivers, and streams, and what causes plutonium to desorb from the colloids. For example, they investigate how the rates of sorption and desorption control colloid-facilitated actinide transport, and how tightly plutonium binds to each type of mineral colloid.

LLNL’s historical role in actinide-related environmental research

For decades, LLNL scientists have studied the environmental behavior of radioactive elements such as plutonium and uranium. The research is driven by the Laboratory’s historic role assessing the nation’s nuclear stockpile, ensuring the safe storage of nuclear waste, and evaluating the fate and transport of radioactive isotopes in the environment.

This type of research provides decision makers with the scientific basis to support plans for remediation and long-term stewardship of sites where actinide contamination has occurred. It also provides the scientific basis to explore long-term storage of nuclear materials as part of nuclear waste repository science.

Isotope geochemistry

Environmental radiochemistry research at LLNL also includes a wide range of isotope geochemistry research, such as studying the composition of the Earth’s mantle and developing new methods to study underground aquifers and other freshwater resources.

Using naturally occurring and anthropogenic isotopes, LLNL scientists use isotope hydrology to trace the movement of water, which enables them to study how quickly it is replenished and whether it is at risk of contamination. For example, researchers can determine when groundwater was recharged from surface water that percolated down through the soil into the aquifer. Knowing the recharge time helps researchers determine the source of contaminants and the flow of groundwater. Researchers also use the isotopic composition of pervasive pollutants, such as nitrates, to determine the source of contamination. Learn more about LLNL’s isotope hydrology research.

Learn more about environmental radiochemistry research at LLNL

Investigating Water under Earth’s Surface, Science & Technology Review magazine, December 2017

Uncovering Dirty Secrets about Soil Carbon, Science & Technology Review magazine, April/May 2016

Protecting Aquifers to Secure Clean Water for California, Science & Technology Review magazine, March 2016

Plutonium Hitches a Ride on Subsurface Particles, Science & Technology Review magazine, October/November 2011