agu fall 2006 meeting neptune and company, inc. radioactive waste disposal in...
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AGU • Fall 2006 Meeting
Neptune and Company, Inc.
Radioactive Waste Disposal in Radioactive Waste Disposal in Hydrologically-Challenged Environments:Hydrologically-Challenged Environments:
Opportunities for Waste Disposal Opportunities for Waste Disposal Resource OptimizationResource Optimization
John Tauxe, PhD, PE and Paul Black, PhD
http://www.neptuneandco.com/~jtauxe/agu06
AGU • Fall 2006 Meeting
Presentation OutlinePresentation Outline
• introduction of the disposal resource
• identification of exposure mechanisms
• mathematical coupling
• probabilistic analysis
• modeling for regulatory compliance
• modeling for resource optimization
• conclusions
AGU • Fall 2006 Meeting
Nevada Test Site Nevada Test Site as a Waste Disposal Resourceas a Waste Disposal Resource
• remotely sited
• unmatched performance
• permitted operations
• radioactive waste is an insignificant addition to existing contamination from weapons testing
AGU • Fall 2006 Meeting
NTS is in the Basin and Range of NVNTS is in the Basin and Range of NV
Frenchman Flat
Yucca Flat
Area 5 RWMS >Area 5 RWMS >
AGU • Fall 2006 Meeting
Nearly 1000 Tests at Yucca FlatNearly 1000 Tests at Yucca Flat
AGU • Fall 2006 Meeting
The Area 3 RWMSThe Area 3 RWMS
In Yucca Flat
AGU • Fall 2006 Meeting
The Area 5 RWMSThe Area 5 RWMS
In Frenchman Flat
AGU • Fall 2006 Meeting
Mechanisms Controlling Mechanisms Controlling Exposure and Potential DoseExposure and Potential Dose
• radon diffusivity and emanation factor
• ant activity
• cover thickness
environmental fate and transport
human behaviors
• site access and occupancy
• inhalation rate
AGU • Fall 2006 Meeting
Engineering ControlsEngineering Controls
active controls:• signs, fences• security force
passive controls:• site knowledge• cover thickness• barriers
photo copyright George Steinmetz
AGU • Fall 2006 Meeting
Mathematical Coupling of Mathematical Coupling of Modeled ProcessesModeled Processes
Physical processes are modeled as coupled partial differential equations:
radioactive decay and ingrowth
gaseous diffusion
aqueous diffusionaqueous advection
bioturbation
plant uptake and redistributionsoil/water chemical partitioning
air/water partitioning
chemical solubilityatmospheric resuspension
i
jjk
jk
t
ii
jeNN
1)0(1121
)(
CDJ sw ~hnK
vx
CDJ sa ~
b
z
zf
max
11
soilRatm CfQ solaq CC
aqHair CKC
soilplant CCRC
soilw
bdwater CKC
1
AGU • Fall 2006 Meeting
Probabilistic AnalysisProbabilistic Analysis
• modeling parameters are defined stochastically, capturing uncertainty
• Monte Carlo is handled by GoldSim*
• sensitivity analysis performed on results
• sensitive parameters are identified
• value-of-information analysis performed
• revisions through Bayesian updating
*GoldSim is modeling software for probabilistic systems analysis.
AGU • Fall 2006 Meeting
Regulatory Compliance:Regulatory Compliance:A common reason for assessmentA common reason for assessment
• regulations (by EPA, NRC, and DOE) are ultimately concerned with protecting human health by specifying a maximum potential dose or release objective
• performance objectives are assessed through modeling fate and transport and future potential doses to a member of the public or intruder
AGU • Fall 2006 Meeting
Resource Optimization:Resource Optimization:A new reason for assessmentA new reason for assessment
• cost/benefit analysis can help inform candidate waste acceptance and disposal technology and configuration decisions
• takes advantage of attributes of the resource
• optimization can be done only through probabilistic modeling and sensitivity analysis
• ALARA - a decision analysis process to keep doses As Low As Reasonably Achievable
AGU • Fall 2006 Meeting
Optimization of OperationsOptimization of Operations
• design disposal operations to minimize future human health effects
• assess candidate waste streams before they are packaged and shipped
• evaluate closure options and expenses
• minimize long-term maintenance and monitoring costs
AGU • Fall 2006 Meeting
ConclusionsConclusions
• optimization (cost/benefit) is made possible through probabilistic modeling and decision analysis
• extension of decision analysis to other environmental problems...
...CERCLA, RCRA, water resources...
• NTS RWMS: a resource worth saving
http://www.neptuneandco.com/goldsim
AGU • Fall 2006 Meeting