Worker exposure to X-ray generator

Print View Posted on: 09 May 2022

Event Date: 29 May 2021 Event Type: Irradiation/Accelerator Facility
Event Location: Japan, Setouchi Works of Nippon Steel Corp., Hyogo Pref. INES Rating: 3 (Final)

On May 29, 2021 the fluorescent X-ray adhesion meter (output 50kV x 40mA) was inspected and calibrated at the Nippon Steel Setouchi Works in Himeji City, Hyogo Prefecture.
There are three main operations for irradiating X-rays with this device.
・ Power supply to this device
・ Increase the voltage and current of the X-ray tube
・ Open the shutter of the irradiation window.
These operations are usually performed on the control panel outside the irradiation room where the device is installed.
Initially, the two workers were working on the control panel outside the irradiation room, but when the calibration sample showed abnormal measures, they entered in the irradiation room with the device on power. There is no legal requirement for this facility to have interlocks. which cut off the power supply when the irradiation room door opens.
As the two workers in the irradiation room confirmed some deposits on the X-ray irradiation window of the device, one of the workers removed them with a hand tool, and the other assisted.
The two workers believed that they had closed the shutter of the irradiation window when entering the irradiation room, but it was revealed that the shutter had not been closed and that the workers were exposed to the X-rays emitted from the device during the operation.
On May 30, two workers were admitted to a hospital for treatment because they had non-fatal symptoms such as erythema on their arms and faces. They were discharged by the end of December last year and are still undergoing outpatient treatment.
The exposure assessment due to this event is still being examined by experts, and no final assessment has been made at this time. We will report as soon as the evaluation is finalized.

INES Rating: 3 - Serious incident (Final) as per 09 May 2022
Release beyond authorized limits? No
Overexposure of a member of the public? No
Overexposure of a worker? No

Contamination spread within the facility? No
Damage to radiological barriers (incl. fuel damage) within the facility? No

Degradation of Defence In-Depth No

Person injured physically or casualty? Yes
Is there a continuing problem? No

Masayuki KANEKO
Nuclear Regulatory Authority
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