Determination of the internal exposure hazard from plutonium work in an open front hood

The particle size and quantity of a plutonium dioxide surrogate escaping an open front hood during routine work was measured. Aerosols were collected using a cascade impactor, and the amount of surrogate on each stage of the impactor was measured using neutron activation analysis. The aerodynamic mass median diameter of particles in the breathing zone of a worker was found to be 0.35 ± 5.1 μm. During a 2-h period when normal work activities were mimicked, an average of 3% of the material or 11.13 ± 0.54 μg escaped the hood. This was calculated to be equivalent to 10,000 ± 487 Bq (²³⁹Pu). The activity in the breathing zone of the worker is estimated, based on other research, to be 36 times less than this, or approximately 280 Bq. Worker occupancy factors were considered and a committed effective dose equivalent of 5 mSv was calculated. The cost-benefit analysis showed the use of the open front hood as a reasonable protective measure. Although worker exposure may approach the International Commission on Radiological Protection limit, the cost of the ergonomic injuries caused by work in a glove box is 5,000 times greater than the dose received by the worker. Protective measures such as respiratory protection should be evaluated on a case by case basis to keep worker exposure as low as reasonably achievable.