The authors release a homemade cord for calculating fractional depositions of aerosol particles in the respiratory tract. The code, named fDep, has adopted the updated ICRP Human Respiratory Tract Model and can well reproduce the deposition values reported in the ICRP publications for reference workers and members of the public. A copy of the source code is available in text format by contacting one of the authors via email at fdep@qst.go.jp.

Gloveboxes that are contaminated with plutonium in the Plutonium Fuel Fabrication Facility of Japan Atomic Energy Agency are size-reduced and removed as a part of inactive fuel facilities decommissioning project. Recently, we have dismantled one glovebox that stood very near at the wall of a room and one transfer tunnel that penetrated another wall. The conventional tent enclosure cannot be applied to provide adequate containment boundaries in these two cases. We therefore developed new containment boundaries. Since the width between the glovebox and the wall was only 5 cm in the former case, we installed tent mounting plates on the wall and attached tents to create a working environment equivalent to a conventional plastic enclosure. As a result, negative pressure control and radiation control were performed as before. On the other hand, in the latter case, we attached a plastic bag with gloves to the tunnel to allow the cutting operation to be performed in an airtight space, resulting in a change to a less stressful face mask with coverall suit work instead of the air-fed suit work owing to access from outside the boundary. In this report, we present the features of new containment boundaries we have developed and the details of the dismantlement procedures we have implemented. We also analyze work performance of the methods by evaluating data achieve in these activities.

The present study aimed at estimating dose reduction effects of face masks against radon progeny inhalation. As the first step, changes in aerosol number concentrations before and after passing through masks were investigated. Four types of masks were used for the experiment: non-woven masks, N-95 masks, urethane masks, and gauze masks. Reduction rates of aerosol number concentrations for four particle size ranges were measured at two experimental conditions. First, each mask was attached to a tube with a diameter of 55 mm and air was sucked through the mask with a defined flow rate to estimate filtration efficiency. Secondly, a mannequin head wearing each mask was prepared and air was sucked through the mannequin nose and mouth. All four types of the masks showed reduction effects on the aerosol number concentrations. The reduction rates were different among the mask types and also among particle size ranges. In addition, the experiment at the two different conditions indicated that the reduction effect depended on the adhesiveness of the mask to the face as well as the mask types. The aerosol reduction rates for different particle size ranges are expected to be generally useful for inhalation protection against aerosols.