Strontium and cesium release mechanisms during unsaturated flow through waste-weathered Hanford sediments

Journal Article · Sat Oct 01 04:00:00 EDT 2011 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es2010368· OSTI ID:1029039

Chang, Hyun-Shik; Um, Wooyong; Rod, Kenton A; Serne, R Jeffrey; Thompson, Aaron; Perdrial, Nicolas; Steefel, Carl I; Chorover, Jon

Leaching behavior of Sr and Cs in the vadose zone of Hanford site (WA, USA) was studied with laboratory-weathered sediments mimicking realistic conditions beneath the leaking radioactive waste storage tanks. Unsaturated column leaching experiments were conducted using background Hanford pore water focused on first 200 pore volumes. The weathered sediments were prepared by 6 months reaction with a synthetic Hanford tank waste leachate containing Sr and Cs (10-5 and 10-3 molal representative of LO- and HI-sediment, respectively) as surrogates for 90Sr and 137Cs. The mineral composition of the weathered sediments showed that zeolite (chabazite-type) and feldspathoid (sodalite-type) were the major byproducts but different contents depending on the weathering conditions. Reactive transport modeling indicated that Cs leaching was controlled by ion-exchange, while Sr release was affected primarily by dissolution of the secondary minerals. The later release of K, Al, and Si from the HI-column indicated the additional dissolution of a more crystalline mineral (cancrinite-type). A two-site ion-exchange model successfully simulated the Cs release from the LO-column. However, a three-site ion-exchange model was needed for the HI-column. The study implied that the weathering conditions greatly impact the speciation of the secondary minerals and leaching behavior of sequestrated Sr and Cs.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1029039
• Report Number(s): PNNL-SA-82284; 2543; KP1702030
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 19 Vol. 45; ISSN ESTHAG; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
CESIUM
Cs
DISSOLUTION
Environmental Molecular Sciences Laboratory
ION EXCHANGE
LEACHATES
LEACHING
RADIOACTIVE WASTE STORAGE
SEDIMENTS
SIMULATION
STRONTIUM
Sr
TANKS
TRANSPORT
WASTES
WATER
WEATHERING
ZEOLITES
ion-exchange
mineral dissolution
release mechanism
secondary precipitates