With the end of the Cold War, the superpowers left a large amount of low-level radioactive waste. However, the team of scientists from the Department of Energy’s Northwest Pacific National Laboratory (PNNL) has proven that they will become cleaner in the future. It is reported that for the first time, PNNL has conducted continuous vitrification treatment of low-level nuclear waste. In the lab, the research team has conducted a three-gallon (11.4 L) scrap solidification experiment from Hanford Site, Washington. The researchers fixed radioactive chemicals inside and turned the waste into a more durable glass.
PNNL scientists melted radioactive waste into the glass of a test platform designed specifically to mimic the "DirectFeedLow-ActivityWaste" system built at Hanford.
Nuclear waste is a major environmental issue facing humankind:
Even if every nuclear reactor on earth is suddenly shut down and no longer new, we still need to process millions of gallons of waste produced in 3/4 centuries, not to mention the future research reactors and hospital radiation labs. Wasted.
The heart of the problem is to find a place to store nuclear waste for a long time, or to develop a chemically inert process that makes it impossible to interact with the environment.
Among the current nuclear waste disposal programs, the more promising one is “vitrificationâ€â€”that is, the filtered waste is mixed with the glass molding material, and then heated in a melting furnace to produce borosilicate glass—the latter Can maintain stability for thousands of years!
This method is usually used on high-level nuclear waste (such as spent fuel rods), but the reality is that there are hundreds of times lower levels of nuclear waste waiting to be processed:
This includes wastes that have been contaminated with radioactive elements, or those that have been exposed to neutron radiation, such as declining medical isotopes, clothing that has been poisoned, dead carcasses of experimental animals, and a large number of low-reactor reactor residues that are in the form of industry.
The red material is radioactive waste from one of Hanford's underground storage tanks. This is the first time that it was made into a solidified glass in a continuous process, similar to the one that will be put into use in the future.
The good news is that PNNL has collaborated with the US Department of Environment River Conservation Office (ORP), which manages Hanford's nuclear waste storage tanks, and the Washington River Conservation Solutions (WRPS) Agency.
PNNL will pilot the new process of 'direct injection of low-level radioactive waste', which is expected to vitrify the millions of gallons of low-level radioactive waste left over from the United States during the nuclear arms race on a certain day in the future.
The test aims to demonstrate that nuclear waste can be processed continuously (rather than in batches), a better understanding of how this method works, and preparation for scaling up.
During the demonstration, PNNL used liquid nuclear waste from Hanford and used filters and ion exchange columns to clarify solids and heavy metals.
The processed liquid is mixed with the raw materials used to make the glass, which is then pumped into a 5 inch (12.7 CM) wide smelting furnace and heated at a controlled rate to 2100°F (1149°C).
About every 30 minutes or so, about 8 ounces (227 grams) of glass are extruded and the total weight reaches 20 pounds (9.1 kilograms).
At the same time, the radioactive gas released from the vitrification process is condensed and reduced to a liquid. They will be concentrated and used for subsequent vitrification.
Finally, PNNL analyzes the glass and grouting to determine whether they meet the processing criteria.
The agency said they plan to launch another laboratory vitrification test later this year. A different filtration and particle exchange process will be validated during this period. Another batch of liquid from the Hanford Waste Pool will be processed and then made into glass.
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