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Chapter 17
Decontamination

Excerpt

Decontamination is the removal of material from areas where it is not wanted. This chapter will deal with the removal of radionuclides, but the same or similar technology could be used for the removal of hazardous chemical material. The technology is similar to the cleaning of dirt, oil. or corrosion products except that radionuclides are associated with the material, Both cleaning and decontamination require similar technologies, methods, equipment, and procedures but the degree of cleaning may be different. The degree of cleaning is defined by certain cleanliness standards. Decontamination is based on cleanliness standards that typically revolve around a personal dose rate or contamination level associated with the component or surface being cleaned. For disposal of the cleaning material, the chemical composition of both the waste and the radionuclide content must be understood. The disposal method and packaging will depend on all of these items.

Decontamination is used to reduce the dose that workers may receive from a component or surface, to reduce the potential for airborne radionuclides, or to reduce the associated disposal cost. Some decontamination can allow for the reuse or recycle of the material, although this approach is currently less common. An example of reuse of material is the melting of slightly contaminated steels to be manufactured into shield blocks for a particle cyclotron. The shield blocks keep natural radiation sources from interfering with the acceleration of particles. Many tons of materials have been recycled for use in nonradioactive environments. In order to accomplish a use for “free-release,” the material must not only be cleaned but also surveyed and found to be below the releasable level of the facility. The facilities that perform “free-release” are licensed by the federal government or the state in which they operate. The license and regulations specify the release limits of the facility.

This document is meant as an introduction to decontamination, both chemical and mechanical, with references to direct the reader to greater detail. The listing of any commercial companies should not be construed as a recommendation for the offerings of products or services.

  • 17.1 Introduction
  • 17.2 Pre-planning
  • 17.3 Operational Considerations
  • 17.4 Radioactive Contamination
  • 17.5 Decontamination Factors
  • 17.6 Oxide Dissolution
  • 17.6.1 Reductive Dissolution
  • 17.6.2 Chromium Dissolution by Oxidation
  • 17.6.3 Oxalic Acid Rinse
  • 17.7 The Nature of Contamination
  • 17.7.1 Radioactive Corrosion Products in Power Reactors
  • 17.7.2 Corrosion Product Transportation, Activation, and Deposition
  • 17.8 Chemical Decontamination Processes
  • 17.8.1 CAN-DECON and CAN-DEREM Processes
  • 17.8.2 CITROX Process
  • 17.8.3 CORD Process
  • 17.8.4 LOMI Process
  • 17.8.5 DFD Process
  • 17.8.6 Termination Criteria
  • 17.8.7 Recontamination
  • 17.9 Mechanical Decontamination Processes
  • 17.9.1 Janitorial Decontamination
  • 17.9.2 Advanced Recyclable Media System
  • 17.9.3 Concrete Shaver
  • 17.9.4 Concrete Spaller
  • 17.9.5 Electro-Hydraulic Scabbling
  • 17.9.6 Heavy Duty Roto Peen
  • 17.9.7 Milling Decontamination
  • 17.9.8 Remote Dry Ice Blasting System
  • 17.9.9 Remotely Operated Scabbling
  • 17.9.10 Soft Media Blast Cleaning
  • 17.9.11 Steam Vacuum Cleaning
  • 17.9.12 Water Blasting
  • 17.10 Other Techniques
  • 17.10.1 Electrokinetic Decontamination
  • 17.10.2 Laser Ablation
  • 17.11 Summary

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