Decontamination for Decommissioning, Not a Cure-All: Better Not to Decontaminate for Clearance?

By Michele Laraia, former IAEA Unit Leader, consultant

Michele Laraia’s series of articles are intended to start a conversation and stimulate debate. We invite you to comment or ask questions below (or send us an email) regarding this article either using your name or anonymously, and we will print some of the comments/questions in an upcoming Weekly Digital Report, as well as in the article itself. Laraia will also respond to any comments/questions from readers. Then, stay tuned next month for a new article and new debate.

Introduction

The proposed decontamination objectives and technologies should be justified as part of the decommissioning plan. Particular attention must be paid to the management of secondary waste generated by the decontamination technologies. The decision to decontaminate should be weighed against the total dose and cost. This article will address decontamination for recycle or reuse: decontamination aimed to reduce occupational doses requires a different approach.

It has become fashionable to use “waste minimization” as an international mantra: it is high time for a warning. Instead of “waste minimization,” I prefer to use “waste optimization” for the reasons given below.

The two management options “recycle / reuse” and “disposal” are under discussion here. The decision-making process for implementing or not decontaminating depends on a number of factors, such as national policy, public acceptance, technical feasibility, hazards and risks assessment, and economic issues. The decision in favor of one of the two options can be based on a simple financial assessment, a cost-benefit analysis, or a more sophisticated “multi-attribute analysis” to account for non-monetary factors. Regardless of the approach, it is necessary to produce a justifiable and auditable solution.

Safety Risks

The optimization/minimization of occupational doses based on an ALARA (as low as reasonably achievable) assessment is only one factor to determine whether the implementation of decontamination for clearance is justified or not. For example, the use of decontamination may increase occupational exposures to radiological or non-radiological hazards (e.g. toxic gases, corrosive fluids- beware of spills when decontaminating with nitric acid…).

The “recycle/reuse” option and the “disposal” option present both radiological and non-radiological risks. The handling of materials prior to and in view of decontamination can be more complicated (and take longer and include higher risks) than straightforward disposition in containers. For both options, provisions should be made to avoid external contamination of workers or inhalation of radioactive dust and aerosols generated. The options differ also when assessing the non-radiological risks. In the “recycle/reuse” option, new hazards from exposures to carcinogenic or toxic chemicals are generally involved during the implementation of decontamination. These hazards may be properly managed if sufficient provisions are made and sufficient expertise is available in the decontamination team. In the “disposal” option, the non-radiological risks are rather associated with off-site activities (e.g. transportation, burial, etc.), but the hazardous substances are enclosed in containers and may not be subject to as many handling steps as they are in decontamination.

Regulatory Issues

The implementation of decontamination as well as the choice between the “recycle/reuse” option and the “disposal ” option needs to be addressed in an early phase of the decommissioning. The use of decontamination techniques generally impacts the dose to the workers, the non-radiological risk associated with the use of toxic products, the production of airborne hazards, the volumes and types of radioactive or chemical waste to be managed, the planning, and the costs of decommissioning. Sometimes the liquid wastes generated by decontamination are incompatible with existing treatment systems and new systems must be constructed and installed, and eventually decommissioned. Also it must be demonstrated that sufficient expertise is available to manage the decontamination process.  Therefore, these issues have to be addressed in the decommissioning licensing file (i.e. decommissioning plan, health and safety report, waste management plan and environmental impact assessment). In some countries the nuclear regulator (i.e. the one responsible for radiological hazards) is different from the regulator responsible for non-radiological hazards: this requires specific coordination as radiological and non-radiological criteria can be conflicting.

Besides, keep in mind that a decontamination process that fails to achieve its target is a waste of doses, secondary waste and money (for example, if the aim is to reach a clearance level of 1 Bq/cm2 and decontamination only achieves 2 Bq/cm2). In this regard, an early dialogue with the regulators would be invaluable: averaging patchy residual contamination over a larger surface can make decontamination achieve its target.

Economic Feasibility of Decontamination

The economic assessment should cover the whole process (i.e. from the removal of the components up to their disposal or reuse). Therefore, the costs to be considered include:

  • the costs for removal, segmentation, sorting, decontamination, characterization, packaging and transport, and burial –if any;
  • the residual value of the material/component to be salvaged;
  • the costs of treatment, conditioning, storage and disposal of all the waste generated (i.e. secondary waste included). An inexpensive disposal option will militate against decontamination, but a country with no disposal facilities may pursue decontamination and waste minimization at all costs;
  • the costs of licensing, taxes, insurance ;
  • contingency offsetting the financial risk due to unforeseen events (e.g. changes in the waste tariffs, changes of regulatory positions, etc.); and
  • the consequences on the overall decommissioning project if the goals of decontamination are not (partly or fully) reached.

Finally decontamination to reuse/recycle materials is one option, but many factors should be evaluated to prove that disposal without decontamination is an inferior option. Of course disposal following some decontamination is a third option, which should be assessed as well.

LaraiaAbout the Author:

Michele Laraia is a chemical engineer by background. An Italian citizen, he gained his first degree at the University of Rome in 1973. In 1975, he received a post-graduate degree as nuclear engineer. From 1975 to 1991, he worked at Italy’s Regulatory Body (ENEA/DISP), firstly in the capacity of reviewer of radioactive waste management systems, and since 1982 as licensing manager of decommissioning projects. During the 1982-1991 period, under his management seven small research reactors and other nuclear fuel cycle facilities were totally dismantled in Italy and their sites returned to other uses. In other plants, modifications to license conditions were implemented in preparation to decommissioning.

From July 1991 to 2011, Laraia worked at the International Atomic Energy Agency, Waste Technology Section, as Unit Leader responsible for decontamination and decommissioning of nuclear installations, closeout of uranium mining and milling sites, and environmental restoration.
The objectives of the work were to provide advice to Member States on the planning and implementation of adequate methodologies and technologies for decommissioning of nuclear and radiological installations and site remediation, to collect and disseminate information on good practices for safe and cost-effective decommissioning, and to provide direct assistance (through the Technical Co-operation  Programme) to Member States in the implementation of their programes and establishment of the required infrastructure for decommissioning and site remediation, and to strengthen their technical capabilities. His tasks included the drafting of technical publications, organization of international conferences and seminars, and the management of technical cooperation projects with developing countries, either on a national or regional scale. Some 50 technical reports and other documents for dissemination to the international community were prepared by Laraia as the Scientific Secretary, and another few dozen coordinated with him. His publications (journals, conference proceedings) amount to over 100. Over 30 less-developed countries received direct IAEA assistance with Laraia in the role of leading Technical Officer.

Laraia retired from the IAEA in 2011. Since then, he has offered consulting services in nuclear decommissioning including lecturing, training, reviewing decommissioning plans, and drafting of worldwide overviews and topical reports for a number of national/international organizations.