4 exposed to radiation during repair work at OL3 nuke plant in June

Four persons were exposed short-term to high radiation dose rates during repair work carried out on hoist equipment at the Olkiluoto 3 (OL3) nuclear plant unit in June 2024, said the owner of the plant Teollisuuden Voima Oyj (TVO) in a press release on Friday.

The exposure incident occurred during the lifting of a dummy fuel element.

The incident, however, did not cause any personal injuries.

TVO on Friday submitted a special report addressing the matter to the Radiation and Nuclear Safety Authority of Finland (STUK) for approval.

STUK will determine the final INES classification during the processing of the special report.

The test weight used for the auxiliary hoist was a dummy fuel element which does not contain fuel.

In this case, however, the dummy element contained a control rod that had been used in the reactor and was radioactive.

The lifting operation was discontinued immediately due to alarms issued by radiation monitors and the dummy element was lowered back underwater.

The maximum personal dose caused by the incident was 40 micro-sieverts (µSv) which did not cause any personal injuries.

The identified causes of the incident include unclear responsibilities, shortcomings of administrative procedures and guidelines as well as deficiencies in communication.

Also, there were no engineering barriers in place designed to prevent the incident by stopping the lifting of the dummy element above the surface of water.

TVO launched actions immediately after the event to prevent the recurrence of a similar event.

From now on, in all work that involves the handling of dummy elements, similar administrative requirements are to be applied in work management as in actual fuel handling work.

In addition, the handling and markings of dummy elements will be made clearer and the presence of radiation protection personnel is required in every lifting operation above the water surface.