1-17 Management of Removed Fuel Debris

-A Study of Treatment Scenarios for Fuel Debris after Removal-

Fig.1-36 Complete scenario ideas from the removal of fuel debris to final disposal

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Fig.1-36 Complete scenario ideas from the removal of fuel debris to final disposal

Various options exist from removal to final disposal.

 

Table 1-2 Characteristics of each treatment scenario idea

The treatment scenario concepts based on several assumed methods are prioritized based on the extent to which they use existing technology.

Table 1-2 Characteristics of each treatment scenario idea

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The removal of fuel debris from the TEPCO’s Fukushima Daiichi NPS is scheduled to begin around 2020. Treatment (processing and disposal) methods for the removed fuel debris are expected to be finalized during the 20-25 year period following December 2011, when the emission of radioactive material and its radiation dose were confirmed to have been significantly inhibited. Therefore, it is necessary to consider an approach of comparative scenario evaluation and obtain fundamental information for selecting treatment methods by the beginning of the removal. In this study, the characteristics and technological problems of each treatment scenario were extracted and put in order, in preparation for comparative scenario evaluation in the future.

Several scenarios for the removal and disposal of fuel debris are shown in Fig.1-36. Among these scenarios, “Treatment” is regarded as a pre-processing step toward the manufacturing of a stable waste form for final disposal.

The selection of treatment methods was implemented for the following policies (Table 1-2).

(1) Storage until disposal strategies are defined

(2) Simple treatment for final disposal without U/Pu recovery

(3) Stabilizing treatment for final disposal without U/Pu recovery

(4) Present treatment for final disposal with positive U/Pu recovery

Elemental technologies for each treatment scenario were evaluated in terms of economy, amount of nuclear waste, and technological difficulties, on the premise that they function in practice. Consequently, it has been found that long-term storage has more advantageous aspects than the other methods, both economically and technologically. Direct disposal, on the other hand, has been found to produce the least amount of waste.

In summary, long term storage and direct disposal are the most advantageous scenarios, though they have some technological problems. The stabilizing treatment, aqueous processing, and pyrochemical processing options are inferior to the rest in terms of economy and the amount of waste.

The present study was sponsored by the Ministry of Economy, Trade and Industry of Japan (METI).


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