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Chapter 13
Decontamination Decisions and Process

Excerpt

The decisions and process for decommissioning nuclear facilities play a key role in controlling radiation exposures. The immediate goals of such projects are to reduce or eliminate occupational and public radiation exposures, primarily by isolating contaminants from surfaces and subsurfaces, and to enable cost effective radioactive waste management and disposal. Decisions that define the applicability of various processes and techniques arc at the heart of decommissioning. Potential techniques include washing, heating, chemical or electrochemical action, mechanical cleaning, and others. For large facilities and equipment, applicable methods are mostly chemical or mechanical. For components that have a role in a facility with a continuing operation mission, dilute chemical agents are typically used to nondestructively dissolve just the outermost surface film bearing most of the contamination. Conversely, if there is no potential for reuse, the base metal can also be dissolved. The process for a small contaminated metal shack may he brief, as compaction may be obviously the most viable option, while a large highly radioactive facility may require more complex processes, including options, such as the wide use of robotics. Intermediate project objectives on the path to restoring the facility to a defined end state include:

- Removing loose radioactive contaminants and fixing the remaining contamination

- Minimizing residual radioactive contamination requiring protective storage

- Maximizing recycle and salvage of equipment and materials

- Minimizing volume requiring disposal as radioactive waste

- Segregating waste for shipping and disposal in the least restrictive acceptable form (e.g., unrestricted, clean rubble, sanitary, special class, surface contamination only, hazardous, radioactive low-level, mixed hazardous and radioactive, remote handled, and transuranic waste)

- Minimizing any period requiring protective storage or long-term monitoring

When chemical decontamination is indicated, it may be necessary to temporarily dedicate appropriate facilities for precipitation, filtration, evaporation, demineralization, stabilization, recycling, and or reclamation. Residual concentrates may represent a significant source of radiation before transportation for treatment and/or disposal. Each step is an expense to the budgeted occupational dose and increases the risk of an unplanned release, such as the uptake of radioactive material that results in higher doses than those from handling the contaminated system without extensive decontamination. Planning is therefore the process of selecting options based on a continual and iterative cost-benefit analysis.

  • 13.1 Introduction
  • 13.2 Decision Process
  • 13.2.1 Release of a Structure for Re-Use
  • 13.2.2 Limiting Occupational Dose
  • 13.2.3 Nine Factors to Remember
  • 13.3 Timing
  • 13.4 Elements of a Cost-Benefit Analysis
  • 13.4.1 Assumed Costs per ODE
  • 13.4.2 Determination of ODE Savings
  • 13.4.3 Waste Management
  • 13.4.4 Project Time
  • 13.5 Estimating Direct Decontamination Costs
  • 13.6 Estimating Indirect Decontamination Costs
  • 13.6.1 Permanent versus Contracted Workforce
  • 13.6.2 Status of Needed Plant Systems
  • 13.7 Additional Decontamination Issues

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