Conference Proceedings Paper
NRU Light Water Reflector Inspections
9th International Conference on CANDU® Maintenance - 2011 December 04-06
Robert H. Lumsden (AECL Nuclear Laboratories)
Ken R. Chaplin (AECL Nuclear Laboratories)
N. Zahn (AECL Nuclear Laboratories)
Nick W. Simpson (AECL Nuclear Laboratories)
In 2009 May, the National Research Universal (NRU) calandria leaked. In the next year the calandria was inspected with six new techniques, repaired, and the repair inspected with four additional new techniques.
The calandria is surrounded by a light water reflector vessel. Concerns that the same corrosion mechanism may have damaged the reflector vessel led to plans to inspect the full circumference of the reflector wall for corrosion damage, through a 64 mm diameter port, from 10 metres away, while inspecting from the corroded surface. The ultrasonic technique is intended to produce a very fine inspection grid, through the corroded surface, using a very small probe body over the approximately 5 metres2 to be inspected.
The calandria vessel inspections were successfully performed, in a short time period, under difficult conditions. This paper will discuss Operating Experiences (OPEX) from the calandria wall inspections that were applied to the reflector wall inspection. Interaction with the CANDU® Inspection Qualification Bureau (CIQB) on procedures, training plans, and mock-up training, led to improvements in how these activities were performed for the reflector wall inspection. Experience with shift turnover meetings led to improvements in how the inspection team captures lessons learned, trends issues, and eliminates reoccurring design and procedure problems. Experience with collected and analyzed data, inspection shift logs, and video captured from inspections and repairs, were used to improve inspection performance. Additionally, how OPEX from radiation/activation and the calibration process affected tool design and procedures, and reduced dose.
This paper will discuss how the next NRU inspections were improved as a result of OPEX from the 2009/10 inspections and industry dialogue.
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