ExaSMR simulation toolkit advances nuclear reactor design

Possible choices to carbon-producing calories assets are turning into ever extra crucial as local weather exchange displays its results at the Earth and in our day by day lives. Even if fossil fuels nonetheless generate a lot of the electrical energy in america, utilities are more and more including renewable assets equivalent to wind and sun to their calories portfolios.

In 2021, 20% of the rustic’s electrical energy got here from renewables vs. 61% from fossil fuels. However by way of 2050, each are projected to offer 44% as renewables proceed to surge and fossil fuels decline.

The place does that depart out of date nuclear calories?

For the previous twenty years, fission reactors have produced a just about unchanging portion of the country’s electrical energy: round 20%. However that share may just get started expanding quickly as new design approaches and reactor applied sciences promise to change into the nuclear energy trade.

The arrival of small modular reactors (SMRs) and complicated reactor ideas (ARCs) indicators a brand new technology of fission energy. Not like maximum business nuclear reactors these days, SMRs are considerably smaller and use standardized designs, thereby lowering building prices and manufacturing time. In the meantime, ARCs discover new applied sciences to supply fission energy extra successfully and safely. Each efforts use laptop simulations to expect the viability of proposed designs and to make stronger them. However operating such fluid dynamics and neutron shipping fashions can also be computationally tough and costly, thus proscribing their use by way of trade.

Exascale SMR (ExaSMR), which is a high-performance computing (HPC) device mission supported by way of the U.S. Division of Power’s (DOE’s) Exascale Computing Challenge (ECP), objectives to make large-scale nuclear reactor simulations more uncomplicated to get admission to, inexpensive to run, and extra correct than the present cutting-edge.

“By way of appropriately predicting the nuclear reactor gas cycle, ExaSMR reduces the choice of bodily experiments that reactor designers would carry out to justify the gas use. Largely, that is what simulation is purchasing firms: a predictive capacity that tells you ways sure options will carry out in order that you do not wish to bodily assemble or carry out as many experiments, which might be significantly dear,” stated Steven Hamilton, ExaSMR mission chief and R&D scientist within the HPC Strategies for Nuclear Packages Staff at DOE’s Oak Ridge Nationwide Laboratory (ORNL).

The ExaSMR mission is operating to give you the nuclear trade’s engineers with the highest-resolution simulations of reactor techniques so far and in flip lend a hand advance the way forward for fission energy.

Coupling physics codes right into a extra robust complete

Nuclear reactors generate electrical energy by way of splitting uranium nuclei to liberate calories in gas rods. Water is heated by way of this calories liberate and turns into sizzling sufficient to become steam that spins electricity-producing generators. ExaSMR integrates probably the most dependable laptop codes to be had for modeling the other physics of this operation, thereby making a toolkit that may expect a reactor design’s complete fission procedure. This toolkit comprises Shift and OpenMC for neutron particle shipping and reactor depletion and NekRS for thermal fluid dynamics.

Even if these types of codes are already neatly established in science and trade, the ExaSMR crew has given them a whole HPC makeover. For the previous 6 years, researchers from ORNL, Argonne Nationwide Laboratory (Argonne), the Massachusetts Institute of Era, and Pennsylvania State College (Penn State) were optimizing the codes for the brand new technology of GPU-accelerated, exascale-class supercomputers, equivalent to ORNL’s Frontier and Argonne’s upcoming Aurora.

OpenMC’s building has been led by way of Paul Romano, and important GPU-optimization paintings for Aurora has been carried out by way of John Tramm; Romano and Tramm are computational scientists at Argonne. Shift used to be at first authored by way of Thomas Evans, team chief for ORNL’s HPC Strategies for Nuclear Packages Staff, and is now optimized for Frontier.

Each codes use Monte Carlo strategies—computational tactics that use extensive numbers of random samples to calculate the possible results of fashions—to simulate how neutrons that transfer in the course of the nuclear reactor have interaction with isotopes, equivalent to uranium, and motive the fission occasions that create warmth within the reactor’s gas rods. The 2 codes additionally type how those isotopes evolve over the years, which predicts the reactor’s lifestyles span.

NekRS—a computational fluid dynamics solver advanced by way of Elia Merzari, affiliate professor of nuclear engineering at Penn State—necessarily describes how the water will transfer and behave when heated by way of the reactor’s gas cylinders. The ExaSMR crew’s ENRICO (Exascale Nuclear Reactor Investigative Code), additionally advanced by way of Romano, allows OpenMC and NekRS to have interaction.

“What we are doing in ExaSMR is a coupled physics simulation between the neutron shipping and the fluid dynamics—you may have those two physics codes which can be speaking from side to side to one another,” Hamilton stated. “The neutron shipping is telling you the place the warmth is generated. That warmth turns into a supply time period for the fluid dynamics calculation. The fluid dynamics tells you what temperature is as a consequence of that warmth supply. After which you’ll be able to modify the parameters within the simulation till each the neutron shipping and the fluid dynamics are in settlement.”

ExaSMR’s talent to appropriately type in excessive decision the entire reactor procedure—thus predicting how a lot warmth the reactor’s fission occasions will produce, the facility of the reactor to switch that warmth to energy turbines, and the lifestyles expectancy of all the gadget—supplies engineers with key insights to make sure the protection and potency in their reactor designs.

Making plans forward to steer clear of stumbling blocks

When the ECP and the ExaSMR mission began in 2016 to arrange device apps and gear for exascale techniques, the ones supercomputers did not exist but—now not even on paper. The crew used to be challenged with figuring out the best way to best possible optimize codes for techniques that had been years clear of being finalized.

“At the start of the mission, we did not even know precisely what the architectures of the exascale machines would appear to be,” Hamilton stated. “It used to be for sure a problem to design our codes whilst having a look forward with self belief that we’d be able to run successfully at the upcoming techniques.”

The crew confronted now not simplest the duty of coupling those separate codes for his or her new use-case situation of large-scale, high-fidelity reactor simulations but additionally the problem of adapting them to new computing architectures with but unknown processors. This uncertainty supposed pushing the boundaries of compilers and device programs by way of trying out use instances that had been a ways past what the device have been examined for on the time—and it all started an ongoing procedure of continuing conversation.

“It required us to have interaction and iterate with the {hardware} distributors and the corporations that produce the device to be sure that their merchandise can deal with our use instances. We’ve researchers who’ve been in virtually day by day touch with people who find themselves writing compilers for the machines and looking to determine problems and put into effect options which can be had to assemble and run our codes,” Hamilton stated.

Luck eventually

The crew’s interplay with distributors and builders paid off with considerable enhancements within the strategies and algorithms utilized by the codes, yielding extensive positive factors in functionality. With its preliminary runs on Frontier, ExaSMR blew previous the crew’s speedup targets for its codes.

Shift carried out SMR simulations on as much as 8,192 nodes of Frontier and concerned simulating over 250 billion neutron histories according to iteration. The functionality accomplished in those simulations is greater than 100× that of the baseline simulations carried out at the Titan supercomputer (i.e., the USA’s maximum robust supercomputer in 2016) and greater than double the functionality growth purpose of fifty× from Titan to Frontier.

NekRS carried out SMR simulations on as much as 6,400 nodes of Frontier, together with the biggest reactor fluid-flow simulation carried out so far with over 1 billion spatial components. The height functionality on Frontier displays a greater than 125× growth over corresponding baseline simulations carried out on Titan.

What is forward for ExaSMR?

Partnering with Westinghouse, which is a manufacturer of business nuclear energy generation, the ExaSMR crew implemented for a DOE Place of job of Complicated Medical Computing Analysis Management Computing Problem grant. Westinghouse needs to guage the have an effect on of the use of higher-enrichment gas than what’s these days used of their reactors. Operating ExaSMR on Frontier will permit them to accomplish high-fidelity simulations to expect how various kinds of fuels would carry out if utilized in a these days running reactor.

Likewise, Hamilton needs to use ExaSMR to present ARC applied sciences being explored within the energy trade, equivalent to the ones being advanced as a part of the DOE Place of job of Nuclear Power’s Complicated Reactor Demonstration Program. This system works with business firms to lend a hand accelerate the demonstration of complicated reactors by way of offering preliminary investment. Two such reactors are slated for near-term deployment by way of 2027: X-energy’s Xe-100 pebble-bed reactor and TerraPower’s Natrium sodium-cooled speedy reactor. 5 further designs from Kairos, Westinghouse, BWX Applied sciences, Holtec World, and Southern Corporate are ramping up for longer-term deployment.

Hamilton foresees ExaSMR turning into an indispensable software for firms which can be coming into a brand new technology of nuclear energy.

“Quite a lot of firms are exploring various kinds of reactor designs these days, and the high-performance, high-fidelity simulations that we are growing have a large number of interesting options for designers,” Hamilton stated. “It is not going, within the close to long term, that we will have sufficient self belief in simulations that they might totally exchange experiments, but when we will be able to scale back the choice of experiments which can be carried out, then there can also be massive monetary positive factors for those firms.”