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Researchers at the Department of Energy’s Pacific Northwest National Laboratory (PNNL) have started a series of experiments that could result in more energy for the grid by increasing nuclear fuel efficiency. The tests followed the special delivery of eleven “high burnup” rods that were irradiated for research purposes.
The rods will be punctured, cut, mechanically stressed and closely examined. This is all part of testing to learn how the metal alloys fared inside the extreme environment of a nuclear reactor for six years. Temperatures can soar to hundreds of degrees Celsius inside a nuclear reactor.
The larger aim of this research is to understand how advanced fuels developed by Global Nuclear Fuel react to “higher burnup” conditions. Those conditions partly consist of keeping the nuclear fuels inside a reactor for longer than is typical, with the goal of extracting more energy out of the fuel than is done today.
Mark Nutt is the director of PNNL’s nuclear energy market sector. He said, “To draw more energy from these materials and increase plant power is like putting new generating capacity on the grid without having to build any new infrastructure. That’s a useful thing for both fuel vendors and a nation that seeks to realize a fuller nuclear potential.”
The series of experiments underway at PNNL will provide important information about how the research rods reacted to the conditions, and may even guide how future fuels are designed. High burnup fuels will boost the performance of the country’s nuclear power fleet by making more efficient use of existing fuel materials. They will make reactors more resistant to nuclear incidents and perhaps even lower the cost of electricity.
Frank Goldner is the Accident Tolerant Fuel federal program manager in the Office of Nuclear Energy. He said, “This is a significant milestone for our Accident Tolerant Fuel program. The development of this new fuel could further support the Trump Administration’s executive order to facilitate five gigawatts of power uprates at existing power plants by 2030 and high burnup fuels could be a big part of that.”
When the rods first arrived at the PNNL-Richland campus in Washington state, many of the scientists watching the delivery wore expressions of anticipation. The shipping process was well-regulated. It required complex logistical coordination between agencies over a span of fourteen months. As an unloading crew meticulously transferred the sixty-thousand-pound stainless-steel rod-carrying cask into the Radiochemical Processing Laboratory (RPL), a team of technicians, radiation chemists, material scientists and nuclear engineers were ready. Testing was to begin immediately.
Similar to forensic analysis, signatures of past exposure imbued throughout the materials will definitely answer important questions for curious scientists. Does the outer casing, called “cladding,” perform as expected under high burnup conditions? Researchers will search for alteration in the material through “tensile testing” techniques. They’ll also employ a digital image correlation method to paint the cladding with thousands of dots. Then they will trace the movement of those dots as the cladding is pulled apart with great mechanical force to gather significantly more data.
In one experiment, researchers used remotely operated manipulators inside a heavily shielded hot cell to puncture the cladding, releasing the rods’ internal pressure. They then captured the radioactive gases that were released, which revealed how much pressure built up inside the cladding as the rods’ internal contents underwent fission reactions. All of this data will assist Global Nuclear Fuel to further validate the models that estimate how their fuel may perform under various conditions.
Please read Part 2 next