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of the NRU reactor with the provision that in-service inspections of the reactor vessel be conducted annually to monitor for corrosion and assess the repair welds, _Q\P \PM ÅZ[\ WVM \W JM KWVL]K\ML VW TI\MZ than nine months after the restart of the NRU reactor. The reactor was returned to service on August 17, 2010. To examine the NRU nuclear reactor vessel wall during in-service inspections, a team of engineers and technicians with VWVLM[\Z]K\Q^M \M[\QVO 6,< ÅZU -KTQX[M Scientific, Inc. (Waterloo, Ontario, Canada) and robotics specialist Liburdi Automation (Stoney Creek, Ontario, Canada) developed a unique robotic system to perform NDT inspections for signs of corrosion, cracks, and metal loss inside the reactor vessel while it is N]MTML IVL ÅTTML _Q\P PMI^a _I\MZ
Corrosion Inspection in a Nuclear Reactor "In the nuclear industry, any inspection
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inspections, the only way to access the in- terior of the NRU reactor, including the cylindrical aluminum vessel (the calandria vessel) that houses the reactor core, is to insert the inspection equipment through existing 4.75-in (120-mm) diameter open- ings at the top of the ~30-ft (9-m) tall reactor structure. The challenges facing the development team, which included motion control specialists from Utex Scientific, Ltd. (Mississauga, On tario,
Canada), were to develop equipment that could be inserted safely through the [UITT WXMVQVO[ WV \PM ZMIK\WZ¼[ ]XXMZ deck plate and reach the inspection sites near the bottom of the vessel, and then precisely position the NDT equipment at the inspection sites so that quality, repeatable readings could be collected in \PM ^M[[MT¼[ ZILQWIK\Q^M PMI^a _I\MZ ÅTTML environment. The NDT corrosion inspections and
weld build-up repairs completed in the QV\MZQWZ WN \PM 6:=¼[ KITIVLZQI ^M[[MT after corrosion damage was detected in May 2009 were performed using in- spection and welding tools attached to a mechanical arm that was inserted through the 4.75-in openings. The arm was controlled with a series of pulleys, gears, and levers, and manually guided by two to three trained operators. Dur- ing these operations, the calandria vessel did not contain fuel rods or heavy water. Because the in-service inspections take
The extended robotic arm and end effector, shown in the reactor vessel mock-up, must be precisely positioned near the vessel wall to conduct quality NDT scans. Photo courtesy of Eclipse Scientific.
NACE International, Vol. 51, No. 3 March 2012 MATERIALS PERFORMANCE 25