First applications for Diakont's decontamination robot

The provider of refuelling services and tooling to the nuclear industry launched underwater robotic cleaning and decontamination services for light water reactor refuelling and other cavities in October 2016.

The Carlsbad, California-based company said nuclear power plant operators have historically conducted cleaning and decontamination of these surfaces manually, after draining water from the space. However, this is a slow process and can result in excessive personnel dose exposure, it says.

Diakont says its underwater robotic decontamination services - which are carried out whilst the reactor refuelling cavities are flooded - "present a vast improvement over manual decontamination because it reduces personnel dose exposure, reduces radwaste, does not impact plant chemistry, and does not risk inadvertently spreading contamination". Also, the company says its innovative decontamination method avoids the risk of personnel injury and component damage associated with hydrolasing. Additionally, in many cases, performing the decontamination robotically while the cavities are flooded shortens the "critical path outage duration" by up to four hours.

The key functional element of the Diakont cleaning tool is a hybrid crawler-remotely operated vehicle (ROV) tool, operated by a small team of Diakont field technicians from a control station on the perimeter of the refuelling floor. Only a single technician is required at the side of the cavity. The company says the tool "transitions seamlessly during operation between ROV 'flying' mode and cleaning 'crawler' mode, for maximal deployment flexibility and bridge-free operation".

Diakont says no adjustments are required to the tool during operation, including when transitioning between cleaning the cavity floor, walls and complex shapes, such as a drywell head. The cleaning tool attaches and drives along the cavity and component surfaces using a high-force, no-flow vortex generator, even in the presence of residual heat removal or shutdown cooling flow. Efficient, effective cleaning is performed using a rugged brushing action to detach the crud, while vacuuming it away at high flow rates to a submerged filter.

Diakont said that during the refuelling outages earlier this year, its decontamination services were "so effective that the post drain-down decon work for the plants was significantly less than in the past, thus reducing time on critical path and helping the utilities meet their radiation exposure goals". It added that it had helped one plant achieve its under 20-day outage duration goal.

"Diakont's remote underwater decontamination service helped the plant operators meet their INPO [Institute of Nuclear Power Operations] and industry collective radiation exposure goals," says Jacco Goemans, director of nuclear solutions for Diakont.

"Diakont's new robotic tooling paves the way for plant operators to perform a safer, more efficient, and more effective method of reactor plant decontamination and cleaning."