Dose assessment following an overexposure of a worker at a Swiss nuclear power plant

The aim of this work was to assess the doses received by a diver exposed to a radiation source during maintenance work in the fuel transfer pool at a Swiss nuclear power plant, and to define whether the statutory limit was breached or not.

Onsite measurements were carried out and different scenarios were simulated using the MicroShield Software and the MCNPX Monte Carlo radiation transport code to estimate the activity of the irradiating object as well as the doses to the limbs and the effective dose delivered to the operator.

The activity of the object was estimated to 1.8 TBq. From the various dose estimations, a conservative value of 7.5 Sv was proposed for the equivalent dose to the skin on the hands and an effective dose of 28 mSv.

The use of different experimental and calculation methods allowed us to accurately estimate the activity of the object and the dose delivered to the diver, useful information for making a decision on the most appropriate scheme of follow up for the patient.