On the morning of August 13, 2014 while cleaning up from a fire event on coal handling conveyer belt #2 at the Ameren
Missouri (Ameren) Rush Island Energy Center it was observed that the nucleonic
gauge located outside of the area of the original fire had some indications of potential damage. The
gauge is located approximately 12 feet above the walkway near the ceiling of the room in an area that was not easily accessible. The
gauge is a Ronan Engineering Model SA1-C10 containing 100 mCi of
CS-137 in sealed solid form. Ameren contacted R. M. Wester (NRC Licensed maintenance vendor) to evaluate the nucleonic
gauge on August 13, 2014 to determine if the
gauge had been damaged due to the fire.
R. M. Wester examination of the source housing showed the exterior to be in good condition with some minor scorching. The shutter check performed showed smooth operation and good beam strength with the shutter open (greater than 200 mR/hr) and good shielding with the shutter closed (1.5 mR/hr). Wipes of the source and the area below the source indicated no contamination or leakage from the source.
An area radiation survey did indicate that some of the lead inside of the source housing had potentially melted and shifted. The on contact readings of the back (0.2 mR/hr), sides/bottom (0.3 mR/hr), and shutter (1.5 mR/hr) were all consistent with expected readings. The 30 cm readings from the source back, sides, and bottom were also as expected (approximately 0.03 mR/hr). The readings on top of the source were higher than expected with a reading of 6 mR/hr on contact and 0.4 mR/hr at 30 cm. These readings on the top of the source do not present an immediate radiological hazard due to their low intensity and the fact that the source is mounted very close to the ceiling in the room. The ceiling support beam and water deflection shield make it difficult to even get a reading 30 cm from the top of the source.
R. M. Wester's recommendation was that the
gauge is functional and it could continue to be use until a replacement device could be procured and installed.