Case Study: Radioactive Decontamination with Laser Technology

Demonstration at Perma-Fix Northwest Richland Inc.

Ben Chramtchenko



Demonstration at Perma-Fix Northwest Richland Inc.

Radioactive Decontamination with Laser Technology

July 17th, 2018


Case Study was conducted by Perma-Fix Northwest Richland Inc.


Allied Scientific Pro develops and manufactures laser cleaning, paint stripping and radioactive waste decontamination systems.

Committed to developing the laser technology as an effective, environmental and user-friendly method for the Nuclear Industry, Allied Scientific Pro is working in collaboration with radioactive waste treatment facilities and nuclear plants.


On July 17, 2018, Allied Scientific Pro visited Perma-Fix Northwest Richland Inc. (PFNW) facility to demonstrate the performance of the LaserBlast-100-RAD system.

Perma-Fix Northwest Richland Inc. (PFNW), operates a radioactive waste treatment facility located in Richland, Washington under the Low Level radioactive waste license WN-I0393-1 issued by the Washington Department of Health (WDOH).  

A sizable portion of the work performed is decontamination, sizing and repackaging of the low level waste.  These processes are intended to provide an environmentally friendly way to reduce the amount of waste that must go for disposal through recycling and return to the industry.  Traditionally, mechanical decontamination methods such as sandblasting, grinding, and polishing, are used.  

Notable attendees during the demonstration included personnel of the nuclear plants and the service suppliers, such as the protection director, the CEO and the vendors.

In a combined effort, Allied Scientific Pro and PFNW performed some measurable testing with a laser decontamination system provided by Allied Scientific Pro.  

Several pieces of radiologically contaminated equipment were provided by PFNW to test the equipment.  A baseline survey was performed by the Radiation Protection Technician to define the “starting point” (Suggestion: “initial dosage or initial contamination”) in the process prior to any decontamination work. Table 1 shows the baseline results.


Table 1

Item

Beta Contamination*

Concrete Ecology Block

5,000dpm

Metal Jack Hammer Sleeve (spot 1)

5,000dpm

Metal Jack Hammer Sleeve (spot 2)

3,000dpm

Metal C-Clamp threads

5,000dpm

Metal C-Clamp frame

10,000dpm

Brass/copper/metal Cutting Torch head

15,000dpm

Plate Steel

30,000dpm

Stainless Steel Tote Lid

3,000dpm

Enclosed fiber Lead Blanket

10,000dpm


*Contamination levels reported by trained and qualified RCT (Suggestion: What does RCT stand for?) utilizing handheld real time instrumentation, the Ludlum Model 12 Ratemeter.  

Basic Safety training on handling Laser technology was provided by the Allied Scientific’s staff to the PFNW personnel. Then training on the safe and effective way to use this technology, through video demonstration and basic hands on, was also provided. PFNW also provided basic safety training on Radiation control and exposure since the team will conduct the test in an area posted as the radioactive area.

All the contaminated pieces of equipment were positioned inside an enclosure controlled by negative pressure ventilation. All the observers could see the work performed inside the enclosure through a glass window, protecting them for any exposure or airborne contamination.

A PFNW technician and a Radiation Protection Technician (RCT) operated the Laser Unit inside the controlled area. The laser control and power unit itself was set up in a clean room while the cords and wand portion was wrapped in contamination protective plastic sheeting and then routed to the process ventilation controlled contamination area.  Observers and the lead engineer were also located in the clean room.  A two way communication system was in place to help the Lead Engineer to communicate with the technician and help him with the unit manipulation.

Several tests on different types of material were performed, by modifying parameters, power level, pulse duration, scan speed, rep rate, shape and size of the beam, and the duration of the pass. The results are shown in the table 2 below.

Table 2

Item

Beta Contamination (dpm)*

Pass #**

Laser Power Setting %**

Beta Contamination Post (dpm)*

% Reduction***

Concrete Ecology Block

5,000

1

30%

4,000

20%

2

60%

2,000

60%

3

80%

1,000

80%

4

80%

<1,000

Below Detect

Metal Jack Hammer Sleeve (spot 1)

5,000

1

100%

2,000

60%

2

100%

<1,000

Below Detect

Metal Jack Hammer Sleeve (spot 2)

3,000

1

100%

2,000

67%

2

100%

<1,000

Below Detect

Metal C-Clamp threads

5,000

1

90%

4,000

20%

2

100%

<1000

Below Detect

Metal C-Clamp frame

10,000

1

90%

2000

80%

2

100%

<1000

Below Detect

Brass/copper/metal Cutting Torch head

15,000

1

70%

5000

67%

2

100%

4,000

73%

Steel Plate

30,000

1

100%

20,000

33%

2

100%

10,000

67%

3

100%

4,000

87%

Stainless Steel Tote Lid

3,000

1

100%

<1,000

Below Detect

Enclosed fiber Lead Blanket

10,000

1

30%

10,000

0%


*Contamination levels reported utilizing trained and qualified RCT utilizing handheld real time instrumentation, the Ludlum Model 12 Ratemeter. Post level analysis happened in real time inside the contamination area.

**Each pass of the laser was done at the instruction of the Allied Scientific Pro’s Mechanical Engineers recommendation.  The Laser was adjusted depending upon the observed results to find the most efficient power and method for passing the laser over the contaminated area.  

***It is important to note that the “below detect” notation above does not indicate the contamination is completely gone but rather that it is below the confidence level of the instrumentation used.

The Allied Scientific’s engineer directed the work and provided tips and techniques to the PFNW operator and RCT to ensure successful testing.  A single “pass” with the laser would be made over the contaminated area.  The RCT would then communicate the contamination levels to the engineer.  The engineer would then make changes to the parameters, including the power level, and then instruct the operator on how to proceed on the speed of the pass.


Results Discussion:

The concrete is of a porous composition.  The laser simply removes a very small amount of the surface area but the contamination is able to go deeper into the concrete.  The general porosity of the concrete demanded multiple passes, however after adjustments to the machine and several passes, the section of the previously contaminated concrete was found to be less than the detection limit and therefore met the release limit criteria.

The metal is not nearly as porous as the concrete and the contamination tends to stay closer to the surface.  In this case, the laser removing a very fine amount of surface area can be effective. For the jackhammer sleeves, the engineer moved the power to 100% and after two passes the material was less than the detection level and met the release limit.

The c-clamps were made of a more hardened steel and since the tool could possibly be re-used for its intended purpose, decontamination without damage to the tool was important.  The power was moved to 90% and was effective but not complete.  After adjusting to 100% power and making a second pass, the threads on the c-clamp were found to be below the detection levels and met the release limit.  

The stainless steel tote lid was tested. Stainless steel has the tendency to be more complicated or resistant than other metals to decontamination techniques. However, the materials tested were decontaminated successfully.  It is important to note that the tested (suggestion: testing was done on) the decontaminated portion (suggestion: area) of the lid which was somewhat recessed  and was also at a farther distance from the wand to the surface. However, this did not appear to cause an issue.

The steel plate had the highest level of contamination present and as a result required three passes at full power.  It also had 200 dpm alpha contamination which was successfully removed.

The lead blanket could not be decontaminated with the laser unit because the fiber encasement of the lead itself is comprised of plastic and would only melt in contact with the laser even at only 30% of the max power level.


Advantages:

The advantages of the laser versus traditional decontamination tools include;

  • Reduction of waste by-products such as sand grit and grinder wheels

  • Safety for the operators with no moving parts

  • Zero consumables

  • Low cost of operations

  • Fewer operators needed

  • Quiet operation

  • No damage to the articles being decontaminated


Conclusion:

A larger more powerful unit would probably be needed to fully assess the usefulness of this technology.  The test did offer enough information to form some general observations.

In order to do a more effective and thorough testing, the following would be recommended:

  • A 1000watt unit.

  • A fixed wand and utilizing a roller system to better control the angle and distance of the laser.

  • A wider variety of contaminated materials.  More concrete, wood, softer metals, etc.

  • Higher and more varying levels of contamination.  

  • Measuring timing of the passes to measure efficiency in time and in turn the labor costs

Normally, the laser would be accompanied by a vacuum system to remove with the ablated materials. However,  for this demo PFNW’s vacuum system was used to avoid the radioactive contamination of Allied Scientific’s vacuum system. The contamination would have required the vacuum system to be disposed as low level radioactive waste which  was cost prohibitive and unnecessary for this testing.  This vacuum system would add an attribute (suggestion: would add a value)to the decontamination process in relation to the safety of the operator and the contamination control.

In summary, the laser did prove to be an effective tool for the decontamination of radioactively contaminated parts as tested.  It is portable, quiet, creates very little by-products, and is a safer alternative to traditional mechanical decontamination methods.


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