The salt at the Waste Isolation Pilot Plant outside Carlsbad, New Mexico– where some of the nations Cold War-era nuclear waste is interred– closes on the storage spaces at a rate of a few inches a year, securing the environment from the waste. Nevertheless, unlike invested nuclear fuel, the waste interred at WIPP does not produce heat.
The Department of Energy Office of Nuclear Energys Spent Fuel and Waste Disposition effort seeks to offer a sound technical basis for multiple practical disposal options in the U.S., and particularly how heat changes the method liquids and gases move through and engage with salt, Kuhlman stated. The understanding acquired from this basic research study will be used to improve conceptual and computer models, eventually informing policymakers about the benefits of dealing with spent nuclear fuel in salt beds. Sandia is the lead lab on the task.
” Salt is a practical option for hazardous waste storage due to the fact that far from the excavation any openings are healed up,” Kuhlman stated. “However, theres this halo of damaged rock near the excavation. In the previous individuals have avoided predicting the complicated interactions within the harmed salt since 30 feet away the salt is a perfect, impermeable barrier. Now, we want to deepen our understanding of the early intricacies next to the waste. The more we comprehend, the more long-term confidence we have in salt repositories.”
Trial-and-error in the first experiment
To understand the behavior of harmed salt when warmed, Kuhlman and colleagues have been conducting experiments 2,150 feet underground at WIPP in an experimental area more than 3,200 feet away from ongoing disposal activity. They likewise keep an eye on the circulation and habits of brine, which is salt water discovered within the salt bed left over from a vaporized 250-million-year old sea. The little salt water that is found in WIPP is 10 times saltier than seawater.
” Salt behaves much differently when its hot. If you warm up a piece of granite, it isnt that various,” Kuhlman stated. “Hot salt creeps much faster, and if it gets hot enough, the water in salt water could boil off leaving a crust of salt on the waste container. Then that steam might move away up until it gets cool enough to go back to liquid and dissolve salt, potentially forming an intricate feedback loop.”
Melissa Mills, left, a Sandia National Laboratories geochemist, and Kristopher Kuhlman a Sandia geoscientist, display salt samples from their Waste Isolation Pilot Plant experimental site. They have actually just begun the third phase of a yearslong fundamental science experiment to comprehend how salt and really salted water act near hot hazardous waste containers in a salt-bed repository. Credit: Photo by Randy Montoya/Sandia National Laboratories
Simply put, the scientists are looking at whether the heat from spent nuclear fuel might help confine waste containers, and even secure them from the corrosion that salted water can cause.
Planning for the experiments first phase began in 2017, utilizing existing horizontal holes at WIPP. Throughout this “shakedown” stage, scientists discovered what equipment to utilize in subsequent experiments. The very first heating system, which worked like a toaster, did not get the neighboring salt hot sufficient to boil brine, stated Phil Stauffer, a geoscientist with an expertise in integrating computer designs and real-world experiments who is leading Los Alamos National Laboratorys contributions. The second heating system the group tried, an infrared design, was effective; it worked more like the sun.
” When we put the first radiative heating system into the very first borehole, as part of the shakedown stage, it turns out the air didnt allow the heat to effectively move into the rock,” Stauffer said. “Then we changed to an infrared heating unit, and the heat moved through the air with little energy loss. In the early mathematical simulations, naively we just put in heat; we didnt stress over how the heat got from the heating system into the rock.”
How salt water and gases move through salt
Throughout the experiments 2nd phase, the group drilled 2 sets of 14 horizontal holes into the side of a hall and placed more than 100 various sensing units into the holes around the central horizontal hole including the heating system. These sensing units kept track of the noises, stress, humidity and temperatures as the salt was heated and cooled.
Melissa Mills, a Sandia geochemist, made an unique salt-concrete seal for testing the interactions between cement and salt water.
Kristopher Kuhlman, front, a Sandia National Laboratories geoscientist, and Thom Rahn, a Los Alamos National Laboratory researcher, thoroughly extract a sample of brine from one of the boreholes. Credit: Photo courtesy Sandia National Laboratories
Among the sensors used were nearly 100 temperature sensing units, like those found in home thermostats, so scientists might determine temperature through time at places around the heating system. Yuxin Wu, a geoscientist from Lawrence Berkeley National Laboratory, also set up fiber-optic temperature level sensing units, stress evaluates and electrical resistivity imaging.
Charles Choens, a Sandia geoscientist, utilized special microphones, called acoustic-emissions sensors, to listen to the “pop” of salt crystals as they expand while heated and contract while cooling, Kuhlman said. The team used these microphones to triangulate the place of the popping salt crystals.
Kuhlman stated. When the salt is hot, the permeability goes down, but when it cools down, the cracks momentarily open up and the permeability boosts.”
To evaluate the flow of gases through the harmed salt, the scientists injected percentages of uncommon gases, such as krypton and sulfur hexafluoride, into one borehole and monitored their emergence in another, Kuhlman stated. “When the salt was hot, the gases didnt go anywhere. When we turned the heat off, the gases permeated the salt and came out in another borehole.”
The group injected lab-made brine into one borehole with a little quantity of the component rhenium and blue fluorescent color as “tracers.” The group is keeping an eye on for the emergence of the liquid in other boreholes, which will be sampled at the end of the test.
” The objective with the fluorescent color– once we drill out post-test samples– is to map where the tracer went,” Mills said. “Obviously, well have the ability to state that it went from one borehole to the other, if we detect a rhenium signal, but we wont understand the course it took. Also, brine will communicate with minerals in the salt, like clay. The fluorescent color is a noticeable way to determine where the liquid tracer in fact entered the field.”
In the 3rd stage, which began in mid-October, the team will be drilling a brand-new range of nine heated boreholes, building on what they learned in the previous phases of the experiments.
Operating in difficult conditions underground
The group has actually learned a lot from the first two phases of the experiment, including the very best heating system type, when to drill the boreholes and just how destructive the salt water is, Stauffer and Mills said.
An example of corroded electronic devices from salt water permeating down an insulated wire. The pervasive nature of salt water in the Waste Isolation Pilot Plant was simply among the challenges the Sandia National Laboratories-led research group got rid of throughout the first two phases of their experiment. Credit: Photo courtesy Sandia National Laboratories
“Weve likewise learned to keep back-up devices on hand since salt dust and salt water damages equipment. Its been a process to find out how to work in the salt environment.”
Kuhlman agreed. “Many things can go wrong when you take sensitive laboratory devices and put it in a salt mine.
The scientists are working together with global partners to utilize the data from this job to improve computer system models of the complex chemical, temperature, water-based and physical interactions that take location underground. This will enhance future modeling of nuclear waste repositories internationally.
Eventually, the group would like to scale up to larger and longer experiments to get data relevant to future salt repositories, said Kuhlman and Stauffer. These data, supplementing currently collected data, would notify repository designers and policymakers about the safety of permanently disposing heat-generating hazardous waste in salt repositories.
” Its been intriguing and actually intriguing, for me, to work on a job that is so hands-on,” Mills said. “Getting to design and build the systems and going underground into WIPP has been really gratifying. Researching in an active mine environment can be a difficulty, however Ive been happy to work down there and implement our ideas.”
Sandia National Laboratories scientists Melissa Mills, left, and Kristopher Kuhlman peer through a salt sample from their Waste Isolation Pilot Plant speculative site. Credit: Photo by Randy Montoya/Sandia National Laboratories
Study to improve computer system designs, inform policymakers for future invested nuclear fuel disposal.
Researchers from Sandia, Los Alamos and Lawrence Berkeley national laboratories have actually just begun the 3rd stage of a years-long experiment to understand how salt and really salty water act near hot hazardous waste containers in a salt-bed repository.
Salts special physical homes can be used to supply safe disposal of radioactive waste, said Kristopher Kuhlman, a Sandia geoscientist and technical lead for the job. Salt beds stay steady for hundreds of countless years. Salt heals its own fractures and any openings will gradually creep shut.
Salts unique physical homes can be utilized to supply safe disposal of radioactive waste, said Kristopher Kuhlman, a Sandia geoscientist and technical lead for the job. In the past individuals have actually prevented anticipating the complex interactions within the damaged salt because 30 feet away the salt is an ideal, impermeable barrier. They likewise keep track of the circulation and behavior of salt water, which is salt water found within the salt bed left over from an evaporated 250-million-year old sea. “Hot salt sneaks much faster, and if it gets hot enough, the water in brine could boil off leaving a crust of salt on the waste container. Melissa Mills, left, a Sandia National Laboratories geochemist, and Kristopher Kuhlman a Sandia geoscientist, show salt samples from their Waste Isolation Pilot Plant speculative website.
