Purpose Of Characterization Surveys. Professional Training Programs

Transcription

1 Purpose Of Characterization Surveys Professional Training Programs

2 PURPOSE OF CHARACTERIZATION SURVEYS: General 2

3 General Scope of Characterization Surveys Generally the most comprehensive of all survey types and generate the most data. ANSI N Required in areas identified as class 1 and 2 by Historical Site Assessment (HSA) or Scoping Survey. MARSSIM. Only a final status survey might be conducted in Class 3 areas. 3

4 General What is Being Characterized Facility structures (e.g., buildings, concrete pads, roads) Environmental media (e.g., primarily soil, but can include sediment, surface and ground water) Residues (e.g., rubble, ash, sludge, slag) 4

5 General Two General Purposes of Characterization Surveys 1. Obtain the information necessary to plan remediation 2. Obtain necessary information to plan the final status survey (FSS) Characterization survey 1 Remedial action (remediation and survey) Final status survey 2 5

6 General Useful References ANSI N Characterization in Support of Decommissioning Using the Data Quality Objectives Process Multi-Agency Site and Survey Investigation Manual (MARSSIM). Revision 1. NUREG U.S. Nuclear Regulatory Commission. Branch Technical Position on Site Characterization for Decommissioning U.S. Nuclear Regulatory Commission. Consolidated Decommissioning Guidance. Characterization, Survey, and Determination of Radiological Criteria. Volume 2. Revision 1. NUREG

7 Information for Planning Remediation Characterization survey Remedial action (remediation and survey) 7

8 Information for Planning Remediation How the Information is Used Assess the scope of proposed decommissioning actions. Support evaluation of alternative decommissioning actions (e.g., for decontamination, waste handling, restricted vs. free release). Ensure the safety of decommissioning workers and public. Evaluate potential environmental releases during decommissioning and determine methods to minimize occurrence and impact. Determine the adequacy of decommissioning funding or financial assurance. 8

9 Information for Planning Remediation How the Information is Used Determine and adjust action levels (e.g., DCGLs). Determine suitability of various survey instruments and analytical methods. 9

10 Information for Planning Remediation Identity of Radionuclides For example: Cs-137, Am-241, Sr-90, H-3 In many cases their identities will already be known. The identity of the radionuclides and the type of radiation they emit affect the action levels and the appropriate survey instrumentation. Identifying difficult-to-detect nuclides is especially important. 10

11 Information for Planning Remediation Physical Form of Radiological Contamination Is it removable or fixed, soluble or insoluble, adsorbed to soil particles or present as large chunks (e.g., fragments of depleted uranium)? Whether it is fixed or removable can affect the action levels, assessment techniques (smears vs. direct measurements), and decontamination options. If it is inhomogeneous or present in large chunks (i.e., spotty) it is more suitable for soil sorting. It is also less likely to become airborne during remediation. If contamination is associated with very fine soil particles, soil washing is a more attractive decontamination option. 11

12 Information for Planning Remediation Concentration of the Radiological Contamination The concentrations help determine whether or not remediation is necessary. The concentrations might not need to be determined for those radionuclides likely to contribute a small fraction of the maximum permissible dose. The concentration of expensive to analyze nuclides (e.g., Sr-90) might not be determined if the need for remediation can be indicated by analyzing other, less expensive to analyze, nuclides (e.g., Cs-137). 12

13 Information for Planning Remediation Extent of Radiological Contamination Estimate the location and areal extent of contamination (e.g., m 2 ). This assessment might include offsite locations. Estimate the depth of contamination (e.g., maximum depth). In soil, this affects the cost and feasibility of excavation. In concrete, this affects the remediation options (e.g., scabbling vs. complete removal of floor or walls). 13

14 Information for Planning Remediation Extent of Radiological Contamination Estimate the volume of any contamination exceeding the action levels. This affects the cost of remediation (and waste disposal), as well as the attractiveness of various remediation methodologies (e.g., soil sorting vs. disposal as waste). Determine if old contamination has been covered by paint, concrete, or asphalt. This will help determine the most suitable survey instrumentation, remediation options, etc. 14

15 Information for Planning Remediation Type, Concentration, and Extent of Non-Radiological Contamination Although important, this topic will not be considered here. Since remediation can remove both radiological and non-radiological contamination, it might not be necessary to assess both in a given area. Evaluate the potential for encountering mixed waste or accidentally generating mixed waste. Mixed waste can be extremely expensive to dispose of. 15

16 Information for Planning Remediation Pathways Affecting Exposures to Workers and Public Information concerning the exposure pathways might already be available from the HSA, but the latter s info might be out-of-date. Changes in demographics might have occurred since the HSA was performed and need to be revaluated. The potential for generating airborne particulates during remediation can be impacted by recent precipitation or lack thereof, vegetative cover, wind conditions, etc. Assess potential pathways for surface runoff during remediation. 16

17 Information for Planning Remediation Pathways Affecting Exposures to Workers and Public Various non-radiological input parameters to the dose models might be evaluated in order to generate sitespecific action levels (DCGLs). Action levels are needed for remediation and the final status survey. In the case of contaminated soil, these parameters can include depth to the water table, suitability of groundwater for drinking, soil-water partition coefficients (k d values), existing contamination in groundwater, etc. 17

18 Information Necessary to Plan Final Status Survey Characterization survey Remedial action (remediation and survey) Final status survey 18

19 Information Necessary to Plan Final Status Survey Input to Calculation of Relative Shift Determine the average and/or median concentrations by analyzing representative samples in each survey unit. These average concentrations can serve as the lower bound of the gray region (LBGR) in the calculation of the relative shift. Determine the variability (standard deviation) of the measurements in each survey unit. This will serve as sigma in the calculation of the relative shift. 19

20 Information Necessary to Plan Final Status Survey Refine Classification and Designation of Survey Units Determine whether or not any measurements are likely to exceed the action level in a given area. If yes, Class 1. If no, Class 2 or 3. Determine whether or not any contamination in an area is likely to exceed a small fraction of the action level. If yes, Class 1 or 2. If no, 3. Determine if the nature of the contamination and the physical characteristics of the area are most compatible with single or multiple survey units. 20

21 Information Necessary to Plan Final Status Survey Establish Ratios between Different Radionuclides Establish ratios between multiple beta (or alpha) emitters to permit the determination of gross beta (or alpha) DCGLs for contamination on building structures. These ratios can also be used to determine weighted detection efficiencies. Establish ratios between inferred nuclides and surrogate nuclides in order to adjust the surrogate DCGLs. 21

22 Characterization and Remedial Action Surveys Flow Chart (Figure 2.7 MARSSIM) Scoping survey Final status survey 22