ML21208A218: Difference between revisions

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{{#Wiki_filter:Subsurface Soil Surveys Public Workshop Cynthia Barr Senior Risk Analyst July 15, 2021
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Development of Derived Concentration Guideline Levels (DCGLs or clean-up levels) for Subsurface Residual Radioactivity
 
Surface versus Subsurface DCGLs
* What is surface soil?
  - Typically top 6 inches, but
  - Dependent on what can be scanned and
  - Dose modeling assumptions
* Typically, different radionuclides and pathways will dominate dose for surface versus subsurface soils
  - it is important to understand the importance of source parameters such as area, thickness and depth of residual radioactivity to dose through sensitivity analysis
 
Surface versus Subsurface DCGLs
* Soil Depth (Important Pathways)
  - Surface (external radiation, incidental ingestion, inhalation)
  - Intermediate (plant)
  - Deep subsurface (groundwater dependent pathways)
 
Multiple DCGLs
* Potential need for multiple DCGLs
  - Vertical heterogeneity and sensitivity of dose results to depth and thickness (i.e., significantly different DCGLs for surface versus subsurface residual radioactivity)
  - Various contaminated media (buildings; surface and subsurface soils; groundwater or surface water; and streambed sediments)
 
Multiple DCGL Considerations
* Challenges associated with applying multiple DCGLs
  - Survey of soils for reuse in an open excavation (when and how to survey)
  - Soil layers are in close contact with each other making accounting of residual radioactivity difficult
* Lack of guidance on conduct of MARSSIM statistical tests for multiple soil layers.
* Potential scenarios that could re-distribute residual radioactivity to the surface should be considered.
* Two conceptual models can Scenarios for  be considered Buried
* No soil cover Radioactivity
* Soil cover 7
 
Groundwater Considerations
* In some cases, enough time has elapsed that existing groundwater contamination is present
* The contribution to dose associated with the existing groundwater contamination should be considered
* Biosphere or dose modeling can be used to determine the dose per unit groundwater concentration to determine the contribution of existing groundwater contamination to dose
 
Thank you!}}

Revision as of 02:47, 8 September 2021

2-2-Development of Dcgls for Subsurface Residual Radioactivity
ML21208A218
Person / Time
Issue date: 07/15/2021
From: Cynthia Barr
NRC/RES/DRA
To:
Aird, Thomas - 301 415 2442
Shared Package
ML21208A206 List:
References
Download: ML21208A218 (9)
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