Plutonium fuel fabrication facility (PFFF)21,22

The plutonium fuel fabrication facility (PFFF) operated from 1972 to 2002 for fabricating MOX fuels for Fugen and the experimental Joyo fast breeder reactor (FBR). The decommissioning and dismantling (D&D) project for the PFFF is divided into the following four phases:

• Phase 1 (up to 2010): stabilization and shipment of nuclear material in the facility. Choose decontamination and volume reduction techniques.

• Phase 2 (2010-2015): D&D planning and adaptability tests.

• Phase 3 (2015-2020): size reduction of equipment and glove box. R&D programme carried out.

• Phase 4 (2020-2035): re-use of buildings for waste storage.

An issue relating to the accumulation of special nuclear material became apparent in the 1990s in this facility. Eight glove boxes in the facility had to be replaced by those with an improved automated fuel fabrication system and residuals recovery system. In order to dismantle these glove boxes, it was necessary to have a more durable containment structure than that of the plastic enclosure, commonly used at the time. To circumvent these issues, the glove box dismantling facility, a centralized decommissioning workshop to dismantle glove boxes, was developed. The purpose of the workshop is to safely dismantle the after-service glove boxes and recover the fuel residuals from the glove boxes. The basic concepts of the workshop are as follows:

1. The workshop has the functionality of a glove box. To prevent the spread of contamination, the level of the internal pressure is kept around 300 Pa in gauge pressure negative to the surrounding room pressure.

2. The workshop is installed in a room in the basement of the plutonium fuel production facility (PFPF) and used for glove box dismantling repeatedly.

3. Remote-controlled devices are installed in the workshop to reduce the radiation dose to which workers are exposed.

The activity undertaken was of both remote and hands-on type size reduc­tion. The data and knowledge will be reflected in the planning of the D&D project for PFFF.

Technological developments to reduce secondary waste generation are being carried out. Dismantled equipment is cut and wrapped in plastic sheets and packing tape, and stored in 200 L drums. The amount of packag­ing material (secondary waste) sheets may be about 20% of the volume of dismantled materials. In addition, the packaging activities are performed by workers wearing airline suits. These suits are also secondary wastes. In addi­tion, waste treatment facilities will remove the packaging materials from the dismantled equipment which must then be sorted.

To reduce waste treatment work and the amount of secondary waste, a direct in-drum system for RAW management has been developed. The direct in-drum system can be stored directly in a double-skin drum without packaging. In addition, RAW stored in the drums can easily be retrieved

from them. To prevent the leakage of radioactivity during storage and retrieval of RAW, the lid of the double-skin drum and of the direct in-drum system are connected by a gasket. The direct in-drum system (Fig. 23.3) is attached to the glove to

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