From Texas A&M (US) : “Computational researchers develop advanced model to improve safety of next-generation reactors”

From Texas A&M (US)

Laura Simmons

Pebble-bed reactors use passive natural circulation to cool down, making it theoretically impossible for a core meltdown to occur. | Image: Getty Images.

When one of the largest modern earthquakes struck Japan on March 11, 2011, the nuclear reactors at Fukushima-Daiichi automatically shut down, as designed. The emergency systems, which would have helped maintain the necessary cooling of the core, were destroyed by the subsequent tsunami. Because the reactor could no longer cool itself, the core overheated, resulting in a severe nuclear meltdown, the likes of which haven’t been seen since the Chernobyl disaster in 1986.

Since then, reactors have improved exponentially in terms of safety, sustainability and efficiency. Unlike the light-water reactors at Fukushima, which had liquid coolant and uranium fuel, the current generation of reactors has a variety of coolant options, including molten-salt mixtures, supercritical water and even gases like helium.

Dr. Jean Ragusa and Dr. Mauricio Eduardo Tano Retamales from the Department of Nuclear Engineering at Texas A&M University have been studying a new fourth-generation reactor, pebble bed reactors. Pebble-bed reactors use spherical fuel elements (known as pebbles) and a fluid coolant (usually a gas).

“There are about 40,000 fuel pebbles in such a reactor,” said Ragusa. “Think of the reactor as a really big bucket with 40,000 tennis balls inside.”

During an accident, as the gas in the reactor core begins to heat up, the cold air from below begins to rise, a process known as natural convection cooling. Additionally, the fuel pebbles are made from pyrolytic carbon and tristructural-isotropic particles, making them resistant to temperatures as high as 3,000 degrees Fahrenheit. As a very-high-temperature reactor (VHTR), pebble-bed reactors can be cooled down by passive natural circulation, making it theoretically impossible for an accident like Fukushima to occur.

However, during normal operation, a high-speed flow cools the pebbles. This flow creates movement around and between the fuel pebbles, similar to the way a gust of wind changes the trajectory of a tennis ball. How do you account for the friction between the pebbles and the influence of that friction in the cooling process?

This is the question that Ragusa and Tano aimed to answer in their most recent publication in the journal Nuclear Technology .

“We solved for the location of these ‘tennis balls’ using the Discrete Element Method, where we account for the flow-induced motion and friction between all the tennis balls,” said Tano. “The coupled model is then tested against thermal measurements in the SANA experiment.”

The SANA experiment was conducted in the early 1990s and measured how the mechanisms in a reactor interchange when transmitting heat from the center of the cylinder to the outer part. This experiment allowed Tano and Ragusa to have a standard to which they could validate their models.

As a result, their teams developed a coupled Computational Fluid Dynamics-Discrete Element Methods model for studying the flow over a pebble bed. This model can now be applied to all high-temperature pebble-bed reactors and is the first computational model of its kind to do so. It’s very-high-accuracy tools such as this that allow vendors to develop better reactors.

“The computational models we create help us more accurately assess different physical phenomena in the reactor,” said Tano. “As a result, reactors can operate at a higher margin, theoretically producing more power while increasing the safety of the reactor. We do the same thing with our models for molten-salt reactors for the Department of Energy.”
As artificial intelligence continues to advance, its applications to computational modeling and simulation grow. “We’re in a very exciting time for the field,” said Ragusa. “And we encourage any prospective students who are interested in computational modeling to reach out, because this field will hopefully be around for a long time.”

See the full article here .


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Texas A&M University (US) is a public land-grant research university in College Station, Texas. It was founded in 1876 and became the flagship institution of the Texas A&M University System in 1948. As of 2020, Texas A&M’s student body is the second largest in the United States. Texas A&M’s designation as a land, sea, and space grant institution—the only university in Texas to hold all three designations—reflects a range of research with ongoing projects funded by organizations such as the National Aeronautics and Space Administration (NASA) (US), the National Institutes of Health (US), the National Science Foundation (US), and the Office of Naval Research (US). In 2001, Texas A&M was inducted as a member of the Association of American Universities (US). The school’s students, alumni—over 500,000 strong—and sports teams are known as Aggies. The Texas A&M Aggies athletes compete in 18 varsity sports as a member of the Southeastern Conference.

The first public institution of higher education in Texas, the school opened on October 4, 1876, as the Agricultural and Mechanical College of Texas under the provisions of the Morrill Land-Grant Acts. It is classified among “R1: Doctoral Universities – Very high research activity”. Originally, the college taught no classes in agriculture, instead concentrating on classical studies, languages, literature, and applied mathematics. After four years, students could attain degrees in scientific agriculture, civil and mechanical engineering, and language and literature. Under the leadership of President James Earl Rudder in the 1960s, A.M.C. desegregated, became coeducational, and dropped the requirement for participation in the Corps of Cadets. To reflect the institution’s expanded roles and academic offerings, the Texas Legislature renamed the school to Texas A&M University in 1963. The letters “A&M”, originally A.M.C. and short for “Agricultural and Mechanical College”, are retained as a link to the university’s tradition.

The main campus is one of the largest in the United States, spanning 5,200 acres (21 km^2), and is home to the George Bush Presidential Library. About one-fifth of the student body lives on campus. Texas A&M has more than 1,000 officially recognized student organizations. Many students also observe the traditions, which govern daily life, as well as special occasions, including sports events. Working with various A&M-related agencies, the school has a direct presence in each of the 254 counties in Texas. The university offers degrees in more than 150 courses of study through ten colleges and houses 18 research institutes.

As a Senior Military College, Texas A&M is one of six American public universities with a full-time, volunteer Corps of Cadets who study alongside civilian undergraduate students.


The Texas A&M University System, in 2006, was the first to explicitly state in its policy that technology commercialization was a criterion that could be used for tenure. Passage of this policy was intended to give faculty more academic freedom and strengthen the university’s industry partnerships. Texas A&M works with both state and university agencies on various local and international research projects to forge innovations in science and technology that can have commercial applications. This work is concentrated in two primary locations–Research Valley and Research Park. Research Valley, an alliance of educational and business organizations, consists of 11,400 acres (50 km^2) with 2,500,000 square feet (232,000 m^2) of dedicated research space. An additional 350 acres (1 km^2), with 500,000 square feet (46,000 m^2) of research space, is located in Research Park. Among the school’s research entities are the Texas Institute for Genomic Medicine, the Texas Transportation Institute, the Cyclotron Institute, the Institute of Biosciences and Technology, and the Institute for Plant Genomics and Biotechnology. Texas A&M University is a member of the SEC Academic Consortium.

In 2017 Texas A&M ranked 19th nationally in R&D spending with total expenditure of $905.5 million. In 2004, Texas A&M System faculty and research submitted 121 new inventions and established 78 new royalty-bearing licensing agreements; the innovations resulted in income of $8 million. The Texas A&M Technology Licensing Office filed for 88 patents for protection of intellectual property in 2004.

Spearheaded by the College of Veterinary Medicine, Texas A&M scientists created the first cloned pet, a cat named ‘cc’, on December 22, 2001. Texas A&M was also the first academic institution to clone each of six different species: cattle, a Boer goat, pigs, a cat, a deer and a horse.

In 2004, Texas A&M joined a consortium of universities and countries to build the Giant Magellan Telescope in Chile; the largest optical telescope ever constructed, the facility has seven mirrors, each with a diameter of 8.4 meters (9.2 yd).

This gives the telescope the equivalent of a 24.5 meters (26.8 yd) primary mirror and is ten times more powerful than the Hubble Space Telescope. Ground-breaking for the construction of the telescope began in November 2015.

As part of a collaboration with the DOE National Nuclear Security Administration(US), Texas A&M completed the first conversion of a nuclear research reactor from using highly enriched uranium fuel (70%) to utilizing low-enriched uranium (20%).

The eighteen-month project ended on October 13, 2006, after the first ever refueling of the reactor, thus fulfilling a portion of U.S. President George W. Bush’s Global Nuclear Threat Reduction Initiative.

TAMU researchers have named the largest volcano on Earth, Tamu Massif, after the university.

In 2016, the university was targeted by animal rights group PETA, who alleged abusive experiments on dogs. Texas A&M responded that a video had been posted by PETA with insufficient context, and it said that the dogs had a genetic condition that also affects humans — Duchenne muscular dystrophy — for which there is no cure. “The dogs — who are already affected by this disease — are treated with the utmost respect and exceptional care on site by board-certified veterinarians and highly trained staff. The care team is further subject to scientific oversight by agencies such as the National Institutes of Health (NIH) and the Muscular Dystrophy Association, among other regulatory bodies.”


Texas A&M has participated in more than 500 research projects in more than 80 countries and leads the Southwestern United States in annual research expenditures. The university conducts research on every continent and has formal research and exchange agreements with 100 institutions in 40 countries. Texas A&M ranks 13th among U.S. research universities in exchange agreements with institutions abroad and student participation in study abroad programs, and has strong research collaborations with the National Natural Science Foundation of China [国家自然科学基金] (CN)and many leading universities in China.

Texas A&M owns three international facilities, a multipurpose center in Mexico City, Mexico, the Soltis Research and Education Center near the town of San Isidro, Costa Rica, and the Santa Chiara Study Abroad Center in Castiglion Fiorentino, Italy. In 2003, over 1,200 Aggie students, primarily undergraduates, studied abroad. Marine research occurs on the university’s branch campus, Texas A&M University at Galveston. It also has collaborations with international facilities such as the Hacienda Santa Clara in San Miguel de Allende, Guanajuato.

Texas A&M’s Center for International Business Studies is one of 28 supported by the Department of Education (US). The university is also one of only two American universities in partnership with CONACyT – Consejo Nacional de Ciencia y Tecnología [Consejo Nacional de Ciencia y Tecnología] (CONACYT)(MX), Mexico’s equivalent of the National Science Foundation, to support research in areas including biotechnology, telecommunications, energy, and urban development. In addition, the university is the home of “Las Americas Digital Research Network”, an online architecture network for 26 universities in 12 nations, primarily in Central and South America.

Texas A&M has a campus in Education City, Doha, Qatar. The campus is part of Qatar’s “massive venture to import elite higher education from the United States”. TAMUQ was set up through an agreement between Texas A&M and the Qatar Foundation for Education, Science, and Community Development, a foundation started in 1995 by then-emir Sheikh Hamad bin Khalifa Al Thani and his wife and mother of the current emir, Sheikha Moza bint Nasser. TAMUQ was opened in 2003, and the current contract extends through 2023. The campus offers undergraduate degrees in chemical, electrical, mechanical and petroleum engineering and a graduate degree in chemical engineering. TAMUQ has received numerous awards for its research. Texas A&M receives $76.2 million per year from the Qatar Foundation for the campus. In the agreement with the Qatar Foundation, TAMU agreed that 70% of its undergraduate population at its Qatar campus would be Qatari citizens. The curriculum aims to “duplicate as closely as possible” the curriculum at College Station, but questions constantly arise over whether this is possible due to Qatar’s strict stance on some of the freedoms granted to U.S. students. TAMU has also been the subject of criticism over its Qatari campus due to Qatar’s support of global terrorism and appalling human rights record. Texas A&M Aggie Conservatives, a campus activism group, has spoken out against the campus and called for its immediate closure on the grounds that it violates a commitment to educating Texans, and diminishes the credibility of engineering degrees earned by students at College Station.

In late 2013, Texas A&M signed an agreement to open a $200 million campus in Nazareth, Israel as a “peace campus” for Arabs and Israelis. The agreement led to protests from students at the Qatari campus who claimed that it was “an insult to [their] people”. The campus was never opened. Instead, Texas A&M opened a $6 million marine biology center in Haifa, Israel.