Radioactive Pollution: Cleaning And Controlling Radioactive Contamination

Radioactive pollution is a highly dangerous and complicated issue to address, often requiring tedious and costly clean-up efforts. The inherent instability of radioactive material means that it emits ionizing radiation in the form of alpha particles, beta particles, and gamma rays, which can be harmful to humans. To protect themselves from radiation exposure, clean-up crews wear protective gear, use Geiger counters, and carry dosimeters to monitor radiation levels. The clean-up process involves limiting the spread of contamination, decontaminating the area, and safely disposing of radioactive waste. This can be achieved through various methods, including the use of robots, water, concrete, and biological processes involving bacteria.

Use robots to stabilise and decontaminate

Robots can be used to stabilise and decontaminate radioactive sites. They are often used to perform tasks that are too dangerous for humans, reducing human exposure to radiation and other hazardous materials.

Remote-Controlled Manipulators

Remote-controlled manipulators are robotic arms equipped with specialised tools and sensors. They can access confined spaces within nuclear facilities, performing tasks such as dismantling equipment, cutting through thick walls, and handling radioactive materials with precision.

Drones

Autonomous drones equipped with radiation detectors and high-resolution cameras can survey and map contaminated areas. They can navigate complex environments, collecting data and creating detailed 3D models of the facility, which aids in planning the decommissioning process and identifying areas requiring specific attention.

Crawling and Climbing Robots

Crawling and climbing robots are designed to manoeuvre through intricate spaces, accessing areas that are challenging for humans to reach. They are equipped with sensors to detect radiation levels, structural weaknesses, and other hazards, assisting in inspections, maintenance, and debris removal while ensuring the safety of human workers.

Underwater Robots

In facilities where water is used as a coolant, underwater robots can be deployed for inspections and maintenance tasks. These robots are engineered to withstand underwater conditions and perform intricate operations, such as repairing submerged structures and identifying leaks in nuclear containment vessels.

Advantages of Using Robots

The use of robots in radioactive stabilisation and decontamination offers several advantages:

• Safety: Minimises human exposure to radiation and hazardous environments, reducing the risks associated with nuclear cleanup.
• Efficiency: Robots can work continuously, enhancing the speed and efficiency of decommissioning projects, ultimately reducing costs and timelines.
• Precision and Accuracy: Robotic systems, with their advanced sensors and precise manipulators, can perform tasks with greater accuracy than human workers.
• Data Collection and Analysis: Drones and specialised robots gather comprehensive data, aiding in informed decision-making throughout the decommissioning process.

Decontaminate self and others to lower exposure

Decontaminating yourself and others is crucial to lower the risk of harm from radioactive exposure. Here are the steps to effectively decontaminate yourself and others:

Remove Contaminated Clothing:

Take off the outer layer of clothing carefully to prevent inhaling radioactive dust. Removing outerwear can eliminate up to 90% of radioactive material. Place the clothing in a plastic bag or sealable container and keep it away from others and pets.

Wash Your Body:

If possible, take a warm shower and gently wash your entire body with soap. Avoid scrubbing, scratching, or scalding your skin. Wash your hair with shampoo or soap, but do not use conditioner as it can cause radioactive material to stick to your hair. Keep cuts and abrasions covered to prevent radioactive material from entering open wounds.

If a shower is unavailable, wash your hands, face, and exposed body parts at a sink with soap and plenty of water. Pay special attention to your hands and face. Use moist wipes, clean wet cloths, or damp paper towels for areas that cannot be washed at a sink. Gently blow your nose and wipe your eyelids, eyelashes, and ears with moist wipes or clean, damp cloths.

Put on Clean Clothes:

If clean clothes are available, wear those stored away from radioactive material. If clean clothes are not accessible, remove the outer layer of clothing, shake or brush it off, and put it back on. Regardless, always rewash your hands, face, and exposed skin after dressing.

Help Others and Pets:

When assisting others, wear waterproof gloves and a dust mask if possible. Follow the same washing and clothing procedures as above. Keep cuts and scrapes covered to prevent radioactive material from entering wounds. Remember to rewash your own hands, face, and exposed skin after providing assistance.

Isolate Contaminated Items:

Place all contaminated wipes, cloths, towels, and clothing in plastic bags or sealable containers. Isolate these bags in a separate area, away from people and pets, to prevent further exposure.

Bioremediation by bacteria

Bioreduction of Radionuclides

Radioactive elements like plutonium or uranium can be precipitated through the metabolic process of reduction, making them easier to collect and dispose of. This is done by adding electrons to the radionuclides, converting them from a soluble to an insoluble state. The insoluble radionuclide is still radioactive but is not as easily transported into groundwater.

There are three categories of reduction: direct, indirect, and genetically bioengineered reduction. Direct reduction occurs when a microorganism uses the oxidized form of a radionuclide directly as an electron acceptor in anaerobic respiration. For example, the bacteria *Geobacter metallireducens* GS15 and *Shewanella oneidensis* reduce oxidized soluble plutonium Pu(VI/V) to the reduced insoluble form Pu(IV).

Indirect reduction occurs when a microorganism uses a non-radioactive element as an electron acceptor, but the reduced element then provides electrons for the reduction of a radioactive element. For instance, *Geobacter metallireducens* and *Shewanella oneidensis* reduce uranium U(VI) indirectly via anaerobic growth.

Genetically engineered bioreduction involves using radiation-resistant bacteria, such as *Deinococcus radiodurans*, which has potent antioxidants and an enhanced DNA repair mechanism. This bacterium has been engineered to express the *Escherichia coli merA* gene, allowing it to convert toxic mercuric ions to elemental mercury, which is less harmful and easier to process.

Biomineralization/Bioprecipitation

Biomineralization refers to the insoluble crystallization of metals through the process of metal precipitation with ligands like sulfides, carbonates, phosphates, and hydroxides, which are enzymatically generated within the microbial cell wall. A study used a reconstructed strain of *Deinococcus radiodurans* with the *Salmonella enterica* gene, *phoN*, which encodes a nonspecific acid phosphatase. This liberated phosphates that could mineralize uranium, and the recombinant strain was able to precipitate over 90% of uranium from a uranyl nitrate solution in just 6 hours.

Biosorption

Biosorption involves surface adsorption and an extracellular complexation process that can be reversed, allowing for the release of the collected waste. The bacterial cell surface has various negatively charged groups, such as phosphates and sulfides, that attract and remove radioactive metals from the environment. Certain strains of *Pseudomonas* can sequester uranium and thorium ions intracellularly through this process.

Bioaccumulation

Bioaccumulation involves the buildup of radioactive waste inside bacterial cells. Some metal ions, including radioactive ones, structurally resemble essential elements for bacterial growth, so microbes take them up from the environment. For example, some *Pseudomonas* species accumulate uranium as uranyl phosphates, and *Micrococcus luteus* accumulates thorium when grown in a thorium and uranium solution.

Use Geiger counters to locate radiation

When cleaning up radioactive pollution, Geiger counters are essential tools for locating radiation. Here's how they work and how they can be used to identify and address radiation sources:

Understanding Geiger Counters

Geiger counters, also known as Geiger-Muller counters, are electronic devices used to detect and measure ionizing radiation. They are widely used in various applications, including radiation dosimetry, radiological protection, experimental physics, and the nuclear industry. The Nuclear Regulatory Commission considers it the most commonly used portable radiation instrument.

How Geiger Counters Work

At their core, Geiger counters contain a Geiger-Muller tube, which is filled with an inert gas such as helium, neon, or argon at low pressure. When radiation enters the tube, it ionizes the gas, freeing electrons and creating positively charged ions. This process generates an electrical current that the counter records over 60 seconds.

Locating Radiation with Geiger Counters

The ability of Geiger counters to detect radiation makes them invaluable for locating radiation sources. Here are some ways in which they can be used for this purpose:

• Identifying Radiation Sources: By moving the Geiger counter through an area, you can pinpoint the exact location of radiation sources. The device will produce audible clicks and provide readings, often in millisieverts (mSv), indicating the presence and intensity of radiation.
• Direction and Intensity Information: Geiger counters not only detect radiation but also provide information about the direction and intensity of the radiation source. This helps workers understand the extent of the contamination and plan their cleanup efforts accordingly.
• Radiation Surveys: Geiger counters are used to perform radiation surveys of an area. This involves systematically moving the device through a location to identify any radioactive contamination. These surveys are crucial for assessing the scope of the cleanup operation and ensuring that no radiation sources are missed.
• Personal Protection: In addition to locating radiation, Geiger counters play a vital role in protecting workers' safety. By carrying these devices, personnel can continuously monitor their exposure to radiation. This is especially important in areas with potential radiation hazards, as it allows workers to take necessary precautions or evacuate if radiation levels approach harmful thresholds.
• Hot Spot Detection: Geiger counters can be attached to the end of long poles or flexible conduits to create "hot spot" detectors. These tools are invaluable for measuring high-radiation areas while protecting operators through distance shielding.
• Discrimination Between Radiation Types: While basic Geiger counters cannot differentiate between different types of radiation, skilled operators can use them to distinguish between alpha and beta particles by varying the distance from the radiation source. This technique is crucial for understanding the nature of the radiation hazard and selecting appropriate cleanup methods.
• Radiation Dosimetry: Geiger counters are used in radiation dosimetry to measure the amount of radiation exposure. This is crucial for ensuring that workers do not exceed safe limits and for assessing the potential health risks associated with radiation exposure.

In summary, Geiger counters are indispensable tools for locating radiation sources during radioactive pollution cleanup operations. They provide critical information about the presence, direction, and intensity of radiation, helping to guide the response efforts and ensure the safety of workers and the public.

Wear protective equipment

When dealing with radioactive pollution, it is crucial to wear protective equipment to shield oneself from harmful radiation and prevent its spread. Here are some key considerations for wearing protective equipment:

Understand Radiation Risks

Before working in a radioactive environment, it is essential to understand the risks associated with radiation exposure. Radioactive material emits ionizing radiation, which can cause microscopic damage to living tissue. High exposure can lead to acute radiation syndrome, while low-level exposure may increase the risk of radiation-induced cancer.

Wear Respiratory Protection

Respiratory protective equipment is crucial to prevent the inhalation of radioactive material. Reusable air-purifying respirators (APR), powered air-purifying respirators (PAPR), and supplied-air respirators (SAR) are recommended to filter and purify the air being breathed in.

Protect Your Skin and Hair

Protective clothing, such as chemical-resistant suits, is essential to prevent radioactive material from coming into contact with your skin and hair. This creates a barrier to block radioactive particles from physically touching your body.

Utilize Dosimeters

Dosimeters are personal radiation detectors that help monitor exposure levels. They are typically worn by individuals working with radiation to track their accumulated doses and ensure they do not exceed safe limits.

Eye and Face Protection

When working with radioactive materials, it is important to protect your eyes and face. Goggles or safety glasses can shield your eyes from radiation and any potential splashes or debris. Face shields or masks can also be worn for additional protection.

Hand and Arm Protection

Gloves are crucial to protect your hands from exposure to radioactive materials. It is recommended to use double gloves to provide an extra layer of protection and minimize direct skin contact with contaminated objects or surfaces.

Foot Protection

Specialized footwear, such as rubber boots, should be worn to protect your feet from exposure to radioactive materials. These boots are designed to block harmful radiation and prevent it from reaching your feet.

Time, Distance, and Shielding

In addition to wearing protective equipment, it is essential to follow the basic principles of time, distance, and shielding. Minimize the amount of time spent near radioactive sources, maximize your distance from them, and use shielding materials such as lead or concrete to reduce radiation exposure.

Remember, when working with radioactive materials, safety should always be the top priority. By wearing the appropriate protective equipment and following recommended protocols, you can help minimize the risks associated with radioactive pollution cleanup and ensure your safety.

Frequently asked questions