PNNL

Professor Yuichi Onda, Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Japan

Cs Fate and Transport at the Fukushima Site, Japan: The 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan released the largest quantity of radionuclides into the terrestrial environment since the 1986 accident at Chernobyl. This accident resulted in 2.7 PBq of ¹³⁷Cs contaminating forests, agricultural lands, grasslands, and urban areas, then subsequently migrating through soil and waterways in the Fukushima Prefecture. Prof. Onda and colleagues in Japan have worked intensively to generate knowledge regarding the deposition, distribution, and transport of fallout radionuclides, especially ¹³⁷Cs, in the terrestrial environment after the FDNPP accident, which were revealed by extensive and continuous environmental monitoring. The researchers present evidence that anthropogenic activities, high run-off, and steep topography led to a rapid decline in the activity concentration of ¹³⁷Cs in soils and rivers, especially in the first year after the accident. The decline in exposed radioactivity was notably faster than that measured after the Chernobyl Nuclear Power Plant accident, likely because of differences in geography and climate, and the intensive remediation activities at Fukushima. These researchers also found that forests in Fukushima have retained a notable amount of ¹³⁷Cs in the upper centimeters of soil that could persist as a source of cesium into rivers. The site is monitored continuously to collect long-term data to understand the complex behavior under different environmental conditions. 

Daniel I. Kaplan, PhD, Savannah River Ecology Laboratory, University of Georgia

Field Demonstration of Reduced Biological Uptake and Immobilization of ¹³⁷Cs Using Illite Clay Additions: The objective of this field study was to evaluate the addition of micaceous minerals to a ¹³⁷Cs-contaminated aquatic system on the Savannah River Site to serve as an effective in situ immobilization technique. The field study was conducted over a 2-year period and incorporated sixteen 3.3-m-diameter column-plots (limnocorrals) that were randomly placed in a ¹³⁷Cs-contaminated pond. In the treated limnocorrals, ¹³⁷Cs concentrations were reduced by 25- to 30-fold in the water, 4- to 5-fold in aquatic plants, and 2- to 3-fold in fish. The addition of the amendment did not adversely affect water chemistry, although increased turbidity and subsequent siltation did alter the aquatic macroinvertebrate insect community. This in situ technology provides a valuable, less environmentally intrusive alternative to costly ex situ technologies.

Jim Szecsody, PhD, Environmental Subsurface Science, Pacific Northwest National Laboratory  

⁹⁰Sr Subsurface Remediation in the Hanford 100-N Area Using Apatite: A permeable reactive barrier was emplaced at the Hanford Site’s 100-N Area to immobilize ⁹⁰Sr in groundwater and in the periodically rewetted zone. This barrier was emplaced by injection of liquid amendments (Ca-citrate, Na-phosphate), which slowly precipitate apatite. Then the ⁹⁰Sr is incorporated into the apatite structure. This presentation describes a) the biogeochemistry used to inject the amendment solution then slowly precipitate apatite, b) the mechanisms and rate at which ⁹⁰Sr  is incorporated into the apatite barrier, and c) field-scale performance. The technology was initially tested at multiple laboratory scales then through two pilot-scale field tests before implementation through a series of wells along a 300-ft section near the Columbia River in the 100-N Area.