Utilizing Laser Ablation for Nuclear Surface Prep

THURSDAY, JUNE 2, 2022


While there are many methods of surface preparation, high power laser ablation systems have proven to be effective at nuclear sites for industrial contamination.

Traditional surface preparation methods, such as grit blasting and power tool grinding, can be effective, but can produce hazardous waste that then has to be collected and disposed of. Safety also becomes a concern for operators with exposure to hazardous airborne contaminants and other injuries.

In terms of nuclear application, abrasive and CO2 blasting are not suitable for use near other applications, limiting access to work areas for operators. Additionally, abrasive blasting can risk damage to other nearby surfaces and can also remove excess base material.

Laser ablation potentially offers an environmentally friendly, safe and accessible method particularly in the nuclear industry.

About Laser Ablation

Laser ablation is a non-abrasive cleaning method used where laser energy is focused and absorbed by the surface to produce favorable modifications. Applications for laser surface preparation can include removal of paint, adhesives, oxides, oils and mold from metal, glass and composite substrates.

This method does not use consumable media, chemicals or gases. It can also be used in close proximity to other activities, controls or other operating equipment.

According to reports, the first successful testing of laser ablation to remove radioactive coatings, surface contaminants and oxides in power plant applications were conducted in 2006 by the Electric Power Research Institute. Industrial laser systems are available today commercially from power generation to military and medical applications.

These systems typically consist of a portable laser source with a fiber optic beam attached to a hand-held or robot-mounted laser end-effector. Ablated materials are reportedly collected at the target surface by a laser fume extractor with multi-stage filtering to prevent release. 

Capabilities and benefits for laser ablation in the nuclear industry include:

  • Removal of contaminated coatings, oxides and rust and hydrocarbons;
  • Significantly minimizing the volume of radwaste;
  • Radwaste reduced to a less costly waste disposal classification;
  • Dose risk reduction from potential contamination sources;
  • Recovery of costly tooling;
  • Recycling of valuable metals that would otherwise be costly radwaste; and
  • De-painting of critical weld seams for NDT.

In a case study recently presented in Nuclear Engineering International, in Oak Ridge, Tennessee, laser ablation was used to decontaminate carbon-steel from large dump trunk beds used to haul contaminated materials from sites around the decommissioned K-25. Contamination included nuclear isotopes, Beta emitters and Alpha contamination, such as radium.

The original decontamination method, manual grinding using handheld power tools, reportedly required 200-man hours and two technicians for a single dump truck bed. Laser ablation took 7% of that time, with one technician for four hours.

As a result, lead materials were also decontaminated to 100% effectiveness in seconds with only one or two passes under the laser beam alongside 100% efficiency in removing contamination and particles. Testing was conducted by Adapt Laser and Philotechnics Ltd.

In the case of some laser systems, such as Adapt Laser, the technology works by sending nanosecond-length pulses of laser light towards a surface. The laser then vaporizes organic coatings, rust or hydrocarbons. These vaporized residues pass through multistage filtering to be scrubbed free of particles and vapors, thus preventing hazardous airborne contaminants.

Additionally, the system is reportedly easy to operate, safe, easily automated and quiet, without requiring clean up and being environmentally friendly. Laser ablation decontamination presents possibilities in the future to the further the technology through automation, robotics and artificial intelligence.

Lasers for Surface Preparation

In 2018, the Travis Air Force Base, located in California, was one of two bases chosen to test the Clean Laser 1000 and the Clean Laser 300 as a new way to remove both corrosion and paint from aerospace equipment.

Those working on the equipment cannot use paint removers, so sanders have taken their place, but this option also has its problems—namely blending the crack, which covers up the severity of the corrosion, and being unable to tell how much paint material is actually being removed.

Other benefits to the use of the laser in corrosion removal, the Air Force notes, are a reduction in the amount of waste produced (in comparison with a sander), and less personal protective equipment required.

The Clean Laser 1000, made by German firm Clean Laser and one of a number of laser surface-prep devices on the market, reportedly uses no media, chemicals or water, is self-contained and fully mobile, and contained a diode pumped laser source. The laser can also be used for pre-treatment to enhance adhesive bonding, cleaning of large molds and weld seam retreatment.

More recently, in 2021, workers considered implementing lasers to clean inside the Notre Dame Cathedral following a fire that ravaged the 850-year-old structure in April 2019. Chicago-based GC Laser Systems, led by art restoration expert Bartosz Dajnowski, was tested inside the structure in the fall.

The technique was used with the goal of weeding out contamination without using chemical or mechanical abrasion.

“What we do is we calibrate our laser technology to excite the layer of contamination with laser pulses,” he said. “And when that contamination gets hit by a laser pulse, the molecules get so excited by the energy that they absorb, they literally shake themselves apart and just vaporize off the surface.”

A fume capture system catches everything that comes off, but more importantly, the tools can be carefully calibrated to pinpoint what exactly is removed.

"Every material absorbs light differently based on its color and based on its composition. And what we do is we calibrate the parameters of a laser light to excite one material but not another based on how it absorbs infrared.”

   

Tagged categories: Asia Pacific; Blasting; EMEA (Europe, Middle East and Africa); Environmental Controls; hazardous materials; Hazardous waste; Hazards; Health & Safety; Health and safety; Laser cleaning; Latin America; North America; Program/Project Management; Robotics; Surface Preparation; Surface preparation; Surface preparation equipment; Technology; Tools & Equipment; Z-Continents

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