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IX Treatment of Radioactive Waste: Reduction of the Radioactivity or Volume of Nuclear Wastes

Consideration of Treatment and Disposal of Secondary Wastes Generated from Treatment of Contaminated Water

Abstract The earthquake and tsunami on March 11, 2011, caused severe accidents at the several Fukushima Daiichi Nuclear Power Units, and a significant volume of highly contaminated water was generated from the accident. Several methods have been applied to decontaminate the water, including systems from AREVA S.A. and Kurion, Inc., in addition to the SARRY (Simplified Active Water Retrieval and Recovery System) and ALPS [Advanced Liquid Processing System; incorporated in the MRRS (Multi Radionuclide Removal System)] systems from Toshiba Corporation. After the decontamination treatments using these systems, various kinds of sludge and spent adsorbents were generated as secondary wastes. These wastes are now tentatively stored at the site, but further treatment shall be applied to produce appropriate waste forms for interim storage and final disposal in a repository.

Waste management—the treatment, storage, transportation, and disposal of these wastes—is believed to require several decades. The authors examined how to manage these wastes in consideration of the large volume of waste, the variety of waste types, and the long period required to carry out their treatment and disposal in a safe and efficient manner. The requirements for an inventory list and online waste management system; a development strategy for waste treatment, storage, transport, and disposal; formation of an R&D implementation and evaluation team; and long-term knowledge management are discussed in this chapter.

Keywords Contaminated water • Disposal • Fukushima Daiichi Nuclear Power Units • Inventory • Secondary waste • Treatment

Introduction

A significant volume of highly contaminated water was generated from the accidents at the Fukushima Daiichi Nuclear Power Units. Several methods have been applied to decontaminate the water. After decontamination treatments using several systems developed by AREVA, Kurion, and Toshiba, various kinds of sludge and spent adsorbents were generated as secondary wastes. These wastes are now tentatively stored at the site, but further treatment shall be applied to produce appropriate waste forms for interim storage and final disposal in a repository. Management of these wastes is believed to take several decades. The authors examined how to manage these wastes in consideration of the large volume of waste, the variety of waste types, and the long period to carry out the treatment and disposal in a safe and efficient manner. The issues identified are discussed in the following sections.

Requirements for an Inventory List and Online Waste Management System

A fundamental issue is to establish a raw waste inventory list with information on various characteristics, including chemical and physical form and radionuclide inventory (Table 28.1). This is the first step for pursuing further examination of treatment and disposal of these wastes. However, it is very difficult to establish a

Table 28.1 Important characteristics of radioactive waste that may be used as parameters for waste classification [1]

Origin

Chemical properties:

Criticality

Chemical composition

Radiological properties:

Solubility and chelating agents

Half-lives of radionuclides

Potential chemical hazard

Heat generation

Corrosion resistance/corrosiveness

Intensity of penetrating radiation

Organic content

Activity concentration of radionuclides

Combustibility and flammability

Surface contamination

Chemical reactivity and swelling potential

Dose factors of relevant radionuclides

Gas generation

Decay products

Sorption of radionuclides

Physical properties:

Biological properties:

Physical state (solid, liquid, or gaseous)

Potential biological hazards

Size and weight

Bio-accumulation

Compactibility

Other factors:

Dispersibility

Volume

Volatility

Amount arising per unit of time

Miscibility

Physical distribution

Free liquid content

complete list from the beginning because the volume of waste and variety of waste types is large and certain radionuclides contained in the wastes are difficult to identify and measure. Therefore, stepwise development and evaluation are important. A management system of the waste inventory should be established, and new waste information obtained by several intensive waste characterization projects should be added to the management system, where the information will be shared among concerned organizations.

The management system should include information about treatment method and source term characteristics, including waste form, volume, surface dose rate, ID number, and location of waste package, which are collected when raw wastes are treated. This system should be maintained and used until final disposal of the wastes. When all wastes are disposed of in a designated disposal facility, the inventory list will be used as the waste records of the disposal facility.

 
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