Stichting Laka

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: Fri, 01-02-2013
ERF description: The licensee reported that the shutter on a locked out gauge, that was inside the cupola of a refractory, had fallen and resulted in overexposure of members of the public. The gauge contained a 296 GBq (8 Ci) Cs-137 source. On the morning of 10/24/2011, it was discovered that the shutter on the gauge had fallen, leaving the source unshielded. Inspectors from the New Jersey Department of Environmental Protection (DEP) visited the site on 11/15/2011. A total of 10 non-radiation workers were exposed to radiation. On 11/29/2012, the State of New Jersey completed its dose assessment and determined that some of the workers received a total effective dose equivalent that ranged from 12.79 to 0.54 mSv (1.3 rem to 0.054 rem). Confirmation of the final dose estimate from was received on 1/28/2013. Four workers received doses greater than 10 mSv (1 rem). The gauge was removed, the shield welded back in place, and then sent back to the manufacturer for failure analysis. That analysis revealed that the shutter was badly corroded and rusted, which was unexpected because it was only five years old. A contributing factor of the failure was chipping that occurred during routine maintenance while the gauge was still attached to the cupola. The licensee used pneumatic chipping hammers to remove a refractory brick layer from inside the cupola. The gauge was located in such a position so that visual inspections were difficult. It is believed that the vibrations caused the badly rusted and corroded shield to fall off. To prevent recurrence, the licensee has received a new gauge which is housed in stainless steel with a stainless steel shutter and it has been placed in the same location where visual inspections are difficult. The licensee has committed to having the gauges removed by a licensed service provider if work on the cupola requires jack hammering or other vibrational work. While the sources are removed, the service provider will inspect the gauges for signs of corrosion or other signs of damage or potential failure. If no work requiring gauge removal occurs within 3 years from the last inspection, the licensee has committed to having a service provider come to their facility for the express purpose of removing the gauges to perform a thorough visual inspection. NRC EN47445.
ERF rating date: 29-01-2013
ERF contact person: Patricia Milligan
ERF address: Reported by Nuclear Regulatory Commission (NRC) of United States of America on 22 Feb 2012. Last update on 01 Feb 2013
ERF affiliation: Nuclear Regulatory Commission (NRC)

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