Radioactivity increase in steam system during rinsing operations at T7 facility

Incident report

May 28, 1999

On May 28, 1999, the radioactivity level of a steam system in the T7 facility of the UP3 plant rose while it was being rinsed with water. Alerted by the radiological monitoring system of the area and by his portable dosimeter, the operator interrupted the rinsing operation and left the area without significant exposure.

A recommendation was made to the nuclear safety authority to classify this event, which had no impact on operating personnel or the environment, as a level 0 event pending further investigation. Investigations carried out within the week revealed a failure in the double-shelled heating system for the process equipment, which contains radioactive solutions.

Given the detection of the design basis failure, the final recommendation to the nuclear safety authority was to classify the incident as a level 1 event on the International Nuclear Event Scale.