Environmental Remediation Examples and Remediation Strategic Planning

Transcription

1 Environmental Remediation Examples and Remediation Strategic Planning Yasuo Onishi October 16, 2011 Pacific Northwest National Laboratory, and Washington State University, Civil and Environmental Department 1

2 2 Radionuclide Pathways to Man

3 Environmental Remediation Assessment Remediation and other response decision making Environmental monitoring experiments Assessment Preliminary assessment to grasp the overall picture and determine critical locations, phenomena, people, etc. use simple methods and models Comprehensive detailed assessment for selected locations, etc. use detailed methods and computer models After making decisions for specific remediation and other responses Detailed site survey Site specific experiments Remediation actions Detailed assessments of prior, during and after remediation

4 Dnieper River Watershed and Chernobyl Nuclear Accident Contamination

5 5 Remediation Examples of Chernobyl Case Better planning and assessment Chemical methods for contaminated Water Zeolite Bentonite Activated charcoal Mineral fertilizers (K, P, N, lime) Physical methods to retard radionuclide movement Clay barriers, dams, ditches, dikes New Safe Confinement Cleaner water supplies New wells Desna River Administrative control 30-km evaluation zone Fishing ban Forest use ban

6 Pripyat River Flooding (~ 1991 Ice Jam) and Remediation Without the Newer East Bank Dike With the Newer East Bank Dike

7 90 Sr Distributions if Chernobyl Shelter Should Collapses Bq/m** Bq/m**2 90 Sr airborne plume Sr on land surface Kiev 90 Sr in the Dnieper River Sr 90 (Bq/m3) Kanev Krem Dndz Dnepr Kahov time (days)

8 Chernobyl Plant At Accident Present NSC construction set-up

9 137 Cs Migration Prediction in Groundwater Bq/m^ E E E E E E E E+003 Without NSC After 100 years Bq/m^3 1.0E E E E+008 With NSC E E+006 After 100 years 1.0E E E E+002

10 Hanford Site: Remediation and Decommissioning Dismantle Remove waste Treat Store Dispose: in-site LLW disposal site : ship to TRU WIPP site : ship to HLW disposal site LLW and its mixed waste TRU (Pu, U, etc.) and its mixed waste HLW Along the Columbia River, 50 burial grounds 579 waste sites 357 excess facilities for decommission 9 reactors for decommission

11 100 N and 100 K-East/K-West Reactors and Trenches 100 N Reactor and a 2-km long Trench 100 K Reactors and a 2-km long Trench 1.7 billion m3 of liquid waste 4 million m3 of liquid waste

12 Site Remediation along the Columbia River Removed 6 million tons of contaminated soil Backfilling and revegitations are the final steps.

13 Pump and Treat of Contaminated Groundwater Withdraw and treat the contaminated groundwater, and injected the de-contaminated water back to the groundwater Not much effective to reduce the contamination, but it is very effective to change the direction and velocity of the contaminated groundwater to not to flow into areas that need to be protected Large-scale groundwater treatment facility is under construction in Hanford

14 134 Cs and 137 Cs Contaminated Soils & Sediments A Potential Ex-Situ Remediation Scheme Soil Washing A Proven remediation technology for radionuclides, heavy metals & hydrocarbons Contaminated Soil Physical Separation 137 Cs TPL? N Lixiviant Extraction Y N Wash Water 137 Cs TPL? Sludge Sorbent Waste Form Y Clean Backfill TPL: Target Performance Level (PNNL Lixiviant: nontoxic, and biodegradable)

15 137 Cs-contaminated Hanford Site Crib Soils Lixiviant Extraction Results (Not-optimized) mm Fraction Hanford Soil Lixiviant Formal Conc Initial 137 Cs Activity (Bq/kg) Final 137 Cs Activity (Bq/kg) 137 Cs activity Reduction (%) E E E E E E E E E E Extractions conducted at 96 C for 6 hr PNNL Lixiviant: nontoxic, and biodegradable

16 Plutonium Migration in South Mortandad Canyon Overland runoff Creek flow discharge Sediment discharge Total Pu Dissolved Pu Particulate Pu

17 17 Cesium-137 Concentration on the Land Surface (in 80-km)

18 Construction of Web-Based Five Detailed Environmental Remediation Distribution Maps Distribution Map 1: Environmental parameter map Distribution Map 2: Radionuclide transport parameter map Distribution Map 3: Radionuclide migration and fate map Distribution Map 4: Remediation distribution map Distribution Map 5: Remediation priority map 18 Data connected to Web Web Page Analysis and Decision making

19 Distribution Map 1: Environmental Parameter Map Radionuclide Concentration Distribution( 134 Cs and 137 Cs) Population distribution Geometry(mountain, plain, river, irrigation waterway, etc.) Land use (farm field, dairy farming, school, hospital, nursing home, road, park, etc.) Land surface and geology (meadow, forest, concrete, sand field, clayey area, etc.) Groundwater and geological parameters (groundwater table height, hydraulic gradient, etc.) 19

20 Distribution Map 2: Radionuclide Transport Parameter Map Weather (rain, snow, temperature, etc.) Land-surface: radionuclide migration parameters Land sloe Soil erosion rate Subsurface: radionuclide migration parameters Porosity Hydraulic conductivity, etc. 20

21 Distribution Map 3: Radionuclide Migration and Fate Maps for 134 Cs and 137 Cs Land Surface: Radionuclide migration amount Radionuclide adsorption Overland runoff amount(rain, snow melt) Soil erosion amount Radionuclide migration amount on the land surface Subsurface: Radionuclide migration amount Radionuclide adsorption Migration amount in unsaturated subsurface water Migration amount in groundwater 21

22 22 Distribution Map 4: Remediation Distribution Map Remediation technology list(excavation, grouting, chemical extraction treatment, etc.) Soil River water, agricultural water, groundwater Remediation method selection for each area shown in Map 1 Remediation area size and amount Performance and maturity of remediation methods Performance and maturity of waste treatment methods Performance and maturity of waste disposal methods

23 Some Remediation of Cesium-Contaminated Contaminated Soil Technology Description Comment Excavation Isolation Grouting In-situ leaching Physical and radiological soil separation Ex-situ soil washing Scrape upper soil layer and either wash soil or dispose. Engineered cover Inject grout material to entrap the radionuclides in a monolith Leach with acid or ion exchange and a complexing agent, such as citrate Separate soils with high concentrations from soils with low concentrations Extract cesium from solids by washing with water or suitable extraction solutions Effective, but remove valuable topsoil unless replaced with new or washed soil. Isolates contaminated materials and reduces exposure Isolates radionuclides, but restrict future land uses Applicable to shallow soil. Excess leachate must be collected. Risk of uncontrolled mobilization. Effectiveness depends on soil characteristics Mature technologies. Effectiveness depends on soil characteristics Effectives depends on soil characteristics

24 Distribution Map 5: Remediation Priority Map Environmental and human risk assessments under Current condition Future conditions due to radionuclide migration Achievability of securing disposal sites Current and future land uses Social and cost considerations Others 24

25 25 Summary Environmental remediation and its assessment examples for the Hanford, Los Alamos and Chernobyl cases were presented. Some remediation technologies and administrative control are applicable to the Fukushima nuclear accident s environmental remediation Remediation strategic planning with a web-based comprehensive remediation distribution maps provides Remediation roadmap Scientific basis on remediation selections Site-specific remediation method, timing, and effectiveness waste treatment and disposal planning Public participation of remediation decision making through webpage Perform remediation activities methodically and quickly before cesium further will spread in the environment.