Nuclear Decontamination by Laser Ablation

THE CHALLENGE

To test laser ablation’s ability to reduce radwaste, enable the recycling of contaminated metal, recover the use of costly tools, and reduce dose rates to personnel at nuclear sites. The results would give Adapt Laser data validating the effectiveness of laser ablation for radiological decontamination.

PROJECT DETAILS

Client: Philotechnics Ltd.

Location: Oak Ridge, TN

Company Overview: Philotechnics Ltd. processes and transports radwaste. They provide radioactive and mixed waste management solutions, including decontamination and decommissioning services, radiological health physics staff augmentation, health and safety plan development, and radiological qualification training solutions.

Adapt Laser agreed to provide the laser equipment and on‐site technical support for DECON testing in return for the company providing detailed test results. These included the type and level of contamination reduction as well as any data related to environmental, health, and safety concerns.

The goal of the testing was to evaluate if lasers could be a more effective, environmentally-friendly alternative to industry-standard methods of nuclear decontamination, such as abrasive grinding with power tools. Prior to testing, Adapt Laser provided training to ensure safe and proper use of the laser.

TESTING PROCESS

Testing was performed on various surfaces, which consisted of carbon-steel and lead. Both small-area (15 in2) and large-area (138ft2) tests were done for efficiency, with even passes from the 1,000 watt CL1000 laser system. In cases when the surface did not show a 100% removal of contaminants, further passes were made until contaminants were undetectable or the decrease of detectable activity had reached its negative threshold.

MATERIALS TESTED

We tested the cleaning solutions on a variety of materials with fixed contamination to better understand the effectiveness and safety of laser ablation for radiologically contaminated surfaces. The surface radiation on these materials included Alpha and Beta contaminants.

CARBON-STEEL

Source: Contaminated dump truck beds used in the decommissioning of a nuclear site in Oak Ridge, TN.

Contaminant Details

Varying isotopic consistencies, primarily Uranium 238
Largely Beta emitters, with very low Alpha contamination

Results

Lighter, Beta particles were found more deeply into the materials than heavier Alpha particles
Varied results based on Alpha/Beta concentrations, but, overall, highly effective in time efficiency, environmental protection, ALARA principles, and manual exertion requirements, compared to other options

LEAD

Source: Contaminated lead bricks, lead containers used for transporting radiological materials, and other items from various locations.

Contaminant Details

Mostly Alpha contamination, especially Radium contaminants

Results

100% efficiency of contamination elimination
Up to 60% time-efficiency improvement

ENVIRONMENTAL PROTECTION

Throughout the testing process, constant air monitoring was performed. Results showed no elevation above typical background levels. Personnel and equipment were also evaluated during and after testing. These results showed no migration of contaminants onto the personnel or equipment.

TEST RESULTS

For the small areas (15 in2), the laser treatment took around 25 seconds to remove all foreign materials from the base layer of the carbon-steel. For lead, the ablation time was even less. Decontamination for the large area (138ft2) required only four hours of work from one individual, as compared to the 200 man hours needed to complete the task using the standard method of power tool grinding. For Alpha-contaminated materials, the lasers were able to achieve 100% removal effectiveness of the radiological contaminants.

Data also showed a great improvement to operator safety and a significant reduction in radwaste produced. These findings are very promising for the future use of laser ablation as an effective, environmentally-friendly solution for nuclear decontamination.

LIMITATIONS

Although laser ablation was able to achieve excellent results removing Alpha contaminant layers, the process had more limited success with the more penetrating Beta contaminants contaminants in carbon steel. Test data showed the laser treatment was most effective when radiological contamination did not exceed a depth of one inch. Even in the most challenging areas, laser ablation was able to significantly reduce the overall time required to decontaminate the treated steel to a releasable limit, compared to other options.