Characteristics of aerosol and air contamination control in reactor decommissioning

In Japan the dismantlement of commercial nuclear power plants will start in late 1990's. The dismantlement of reactor internals, reactor pressure vessel(RPV) and radiation shielding concrete will be very noticeable works from the viewpoint of protection of internal exposure. The remote underwater cutting, disk cutting and controlled blasting will be used to reduce the dose to workers. Through practical experience of JPDR decommissioning, some parameters of size distribution, dispersion rate, re-suspension co-efficient of radioactive aerosol generated during dismantling operation are discussed for dose evaluation. The local exhaust devices and temporary containment room with HEPA filter are also described. (author)