Radiotherapy accident in Zaragoza

The 1990 Clinic of Zaragoza radiotherapy accident was a radiological accident that occurred from December 10–20, 1990, at the Clinic of Zaragoza, in Spain.

In the accident, at least 27 patients were injured, and 11 of them died, according to International Atomic Energy Agency (IAEA). All of the injured were cancer patients receiving radiotherapy.

On December 7, 1990, a technician performed maintenance on an electron accelerator at the Clinic of Zaragoza. On December 10, it returned to service after the repairs. On December 19, the Spanish Nuclear Safety Board was scheduled to make its annual review to the device, but due to bureaucratic reasons this review was delayed. The Spanish Nuclear Safety Board found the electron accelerator power was too high. On December 20, 1990, the unit was stopped, and was restarted on March 8, 1991.

Affected patients immediately suffered burns on the skin of the irradiated area, as well as inflammation of the internal organs and bone marrow. The first patient died on February 16, 1991, two months after irradiation. Fatalities increased until, on December 25, 1991, the last of a total of 25 patients died. However, the IAEA established that eleven of the deaths were due to the faulty maintenance.

The number affected might have been higher, because 31 other cancer patients were receiving treatment with the accelerator, but the other unit at the clinic was in perfect working condition.

The radiotherapy unit was repaired without following the correct instructions. The unit, in service 14 years at the time of the failure, had a breakdown in the electron beam accelerator control system ('deviator'). Repairs incorrectly increased output power, so patients that should have received therapy at 7 MeV were instead treated at 40 MeV.

Initially, the hospital was thought responsible for the accident, and specifically, the management of the radiological unit. The manager of the hospital said that the maintenance technician was responsible, and the Health Minister blamed General Electric (GE), the makers of the radiological unit, who had contracted out the maintenance.

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