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Event Report Forms (ERFs) are filed to the IAEA. Sometimes there are multiple event reports, updating the rating, the event description. Here you only see the latest event report

ERF send date: Mon, 24-03-1997
ERF description: On 96-05-24, a radiation control technician was in the process of exiting the reactor building when his gamma meter alarmed. During subsequent survey of the area, he discovered narrow radiation beams (approximately 5 cm diameter) of around 8 mSv/h gamma emanating from horizontal flux detector (HFD) sites 6 and 7, both of which are spare sites with no flux detection instrumentation installed.. The spare HFD sites are located approximately 0.2 meters above the reactor vessel center-line, and contain a guide tube that passes through the core. Examination of the equipment showed that radiation shields normally installed on these ports were not present. Investigation determined that these shields were removed between July 9 to 15 1995, to allow access for pressure tube measurements during the 1995 outage, but were not reinstalled. The outage lasted until late December when the reactor was returned to full power operation. The reactor operated for approximately 5 months without the shields in place. The narrow beam width resulted in the beams being extremely difficult to detect and as such, exposure could have been received yet gone undetected by dosimetry. During this period, two members of station staff worked in the area of the HFD units, but their dosimetry did not detect any abnormal exposure. A detailed reconstruction of the work was used to determine the exposure received. This reconstruction was assisted by review of photographic records taken during the original work. The doses assigned are well within the range experience by Atomic Radiation Workers. The two staff members were assigned whole body doses of 0.92 and 1.75 mSv. Eighteen fuel handlers, who had performed operations in the area, were assigned doses ranging from 0.13 to 1.3 mSv. Exposures to other individuals was estimated as less than 0.1 mSv which is below the reporting level.
This incident, provisionally rated at level 2 on the INES scale, has been reduced to a level 1 rating based on the results of the final dose assessment. No administrative or statutory dose limits were exceeded, however, defence-in-depth was degraded.
ERF rating date: 08-01-1997
ERF contact person: Mr. W. Andersen
ERF address: 700 University Avenue, Canada
ERF affiliation: Ontario Hydro H11-B1, Nuclear Technology Services Division

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Power Reactor Research Reactor Radwaste Facility Enrichment Facility Radiation Source Irradiation/Accelerator Facility Transportation

Fuel Fabrication Fuel Reprocessing Research Facility Mining/Milling Radioisotope Processing/Handling Facility Other