Plutonium distribution and oxidation states in a reactor leaching ponds system

Area of Science:

• Environmental Science
• Radiochemistry
• Aquatic Ecology

Background:

• Nuclear reactor operations can release radionuclides like Plutonium (Pu) into aquatic environments.
• Understanding Pu behavior in aquatic ecosystems is crucial for environmental monitoring and risk assessment.

Purpose of the Study:

• To quantify Plutonium (Pu) concentrations and oxidation states in a test reactor leaching ponds system.
• To determine the distribution of Pu among water, plankton, particulates, and sediment.
• To assess the role of sediments and plankton in Pu cycling and bioavailability.

Main Methods:

• Analysis of 239,240Pu and 238Pu concentrations in water, net plankton, suspended particulates, and sediment.
• Determination of Pu oxidation states (III, IV, V, VI) in filtered water.
• Calculation of Plutonium Concentration Ratios (CR) and distribution coefficients (Kd).

Main Results:

• Highest Pu concentrations were found in net plankton, with significant temporal variations.
• Sediments acted as the main Pu reservoir, with distribution coefficients (Kd) ranging from 1.6 x 10^4 to 1.2 x 10^5.
• Reduced Pu oxidation states (III and IV) constituted 57-71% of dissolved Pu, contrasting with oxidized forms dominant in other aquatic systems.
• Plutonium association with sediment was inversely related to particle size.

Conclusions:

• Net plankton and sediments play significant roles in Pu dynamics within the studied ponds system.
• The prevalence of reduced Pu oxidation states in the pond water is a unique characteristic compared to other large aquatic systems.
• Sediments are the primary sink for Pu, influencing its environmental fate and transport.