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Atomic Insights

Atomic energy technology, politics, and perceptions from a nuclear energy insider who served as a US nuclear submarine engineer officer

Graphite Moderated Reactors

China’s high temperature reactor – pebble bed modular (HTR-PM) achieves its first criticality

September 14, 2021 By Rod Adams 34 Comments

On the morning of September 12, 2021, reactor number 1 of the eagerly awaited HTR-PM project was taken critical for the first time. Initial criticality for any new reactor is a big deal for the people involved in the project; this one is a big deal for the future of nuclear energy. It might also become a big deal for humanity’s ability to effectively reduce CO2 emissions enough to slow climate change.

HTR-PM is a demonstration reactor that uses two identical gas-cooled high temperature modular reactors to produce the heat for a modern, subcritical, 200 MWe steam turbine. The steam system operates at the same temperature and pressure as many recently constructed coal heated steam plants that China has been mass producing for more than a decade as it rapidly industrialized and became one of the world’s leaders in manufacturing, metals production and chemicals.

The press release from China National Nuclear Corporation (CNNC) includes the following statement.

They [HTRs) have broad commercial application prospects in nuclear power generation, combined heat, power and cooling, and high-temperature process heat. They are my country’s optimization of energy structure and guarantee of energy supply. An important path to safety and to achieve the “dual carbon” goal.

China National Nuclear Corporation press release dated 09-13-21 (https://www.cnnc.com.cn/cnnc/xwzx65/ttyw01/1112318/index.html) Note: Original in Chinese simplified, translated by Google Translate

Though the announcement does not specifically include coal furnace replacement, producing steam at the same temperature and pressure as used by modern coal plants qualifies as “high-temperature process heat.”

HTR-PM criticality is the most recent step in a long process of commercializing high temperature gas cooled reactors. Though they have a long history, proponents (like me) believe they are an advanced type of commercial atomic fission power technology. (See the high temperature gas reactor history description below.)

China has been purposefully working on high temperature gas reactor technology development for the past 30 years. They have absorbed lessons from HTR experience in Japan, the United States, the UK, and South Africa while also building their own domestic intellectual property and manufacturing capability. According to the China Huangeng Group Co. LTD (CHGC) press release, the project’s direction includes a strong emphasis on building indigenous capacity to build HTR without outside assistance.

As the world’s first pebble-bed modular high-temperature gas-cooled reactor, the demonstration project used more than 2,000 sets of equipment for the first time, and more than 600 sets of innovative equipment, including the world’s first high-temperature gas-cooled reactor spiral-coil once-through steam generator. The first high-power, high-temperature thermal magnetic bearing structure main helium fan, the world’s largest and heaviest reactor pressure vessel, etc., are of great significance to promote my country to seize the world’s leading advantage in the fourth-generation advanced nuclear energy technology.

China Huangeng Group Co. LTD press release dated 09/12/21 (https://www.chng.com.cn/detail_jtyw/-/article/ccgb60va5Gwc/v/962479.html) Note: Original in Chinese simplified, translated by Google Translate

Aside: The above includes a statement that helps explain why HTRs have not been universally popular and why they still face headwinds, even from nuclear energy advocates. Each reactor module produces about 250 MWth, which compares to about 3300 MWth in a 1000 MWe PWR or BWR. Even with higher temperatures and higher efficiency, each core can produce 1/10th of the electricity of light water reactors, but the first HTR pressure vessel is described as “the world’s largest and heaviest pressure vessel.” Pressurized gas has a far lower capacity to move heat than pressurized water.

But there are more factors to be considered in atomic fission power plant economics than the size and weight of the pressure vessel. End Aside.

China is rightfully proud of its accomplishment in achieving HTR-PM initial criticality. There are many more steps in the journey, but this step is important. It marks one more milestone in the process of creating nuclear fission power stations that can take full advantage of the world’s vast coal fired power station infrastructure.

Brief high temperature reactor history

Arguably, the basic idea for HTRs was initially proposed during the earliest days of nuclear power development – immediately following WWII. Dr. Farrington Daniels proposed a high temperature gas reactor as the heat source for what was then a modern steam system. The Daniels Pile project was initially funded by the Manhattan Commission and gathered some momentum before being abruptly cancelled by the nascent Atomic Energy Commission in early 1947.

In the late 1950s Germany’s Rudolf Schulten followed through on the idea and led the project to build the world’f first high temperature pebble bed reactor, the AVR. That small (46 MWth, 15 MWe) prototype operated for about 20 years. Its construction began in 1960, it was connected to the grid in 1967 and it was shut down in 1988.

The US and the UK built their own version of high temperature reactor prototypes, the US at Peach Bottom and the UK’s Dragon reactor at Winfrith in Dorset.

General Atomics, the US company that designed and built the successful prototype at Peach Bottom built a scaled up, significantly different design at Ft. St. Vrain (330 MWe). That reactor had a dismal operating history due to several FOAK system design problems. By the time the defects were corrected, the designer had lost all of the follow on orders. The plant owners had lost patience, didn’t want to own and operate an orphan plant design and shut the system down.

Germany built a larger, 300 MWe pebble bed reactor (THTR) but that reactor had unfortunate timing. It began operating in 1985 with a 1000 day temporary operating license. Before THTR had operated long enough to complete testing and rise to full power operation, the Chernobyl reactor exploded. Reports claimed that the graphite moderator was a primary contributor to the accident and there was a widespread, durable misinterpretation that the graphite actually caught fire.

THTR was a graphite moderated reactor. Owners could not convince the public or the regulators that there are fundamental differences between graphite moderated, helium cooled reactors and graphite moderated, water cooled reactors. THTR was shut down in September 1989 when its initial license expired and that license was not extended.

In the 1990s, South Africa invested several billion dollars and a lot of engineering effort in developing the pebble bed modular reactor (PBMR). A primary reason that effort did not achieve success is that it started with the notion that it was reasonable to build a 200 MWe turbine generator with high pressure helium as the working fluid and then to mount that large machine vertically inside a pressure vessel. That concept works on paper, but executing it proved to be extremely difficult and expensive. Before the project ended, designers had decided to mount the helium turbomachine in a more conventional, horizontal alignment, but the South African government had lost patience by that time.

Chinese technologists, led by Prof. Zhang Zuoyi, learned from PBMR’s experience. They chose to step back to what had worked well for the AVR and to gradually make improvements. They built the HTR-10, a 10 MWe prototype system with a helium to water steam generator that helped them learn on an affordable scale while planning for the next iteration.

HTR-10 has operated well as a prototype. Its capacity factor has been modest, but it wasn’t conceived as a steady state, commercial electricity producer. It has been used to test fuels, test materials, test equipment, train operators and refine operating procedures. In other words, it has done what prototypes are supposed to do.

Construction on HTR-PM began in 2012. It has taken a bit longer than initially planned, but part of the delay rests with the fact that some of the necessary components – like the unique, spiral-coil once-through steam generator – were difficult to design and refine into something that could be efficiently replicated.

The Shidaowan site is planned to eventually host 16 more HTR-PMs. There are already plans underway to design and build an HTR-PM600. That system will use pebble bed reactor models – each the same as the reactor modules used for the HTR-PM) to provide the required heat for a 600 MWe steam turbine power station.

Filed Under: Advanced Atomic Technologies, Atomic history, Business of atomic energy, Gas Cooled Reactors, Graphite Moderated Reactors, International nuclear, New Nuclear, Pebble Bed Reactors, Small Nuclear Power Plants, Smaller reactors

Atomic Show #287 – Darren Gale, VP Commercial Operations, X-Energy talks about Xe-100

November 12, 2020 By Rod Adams 2 Comments

X-Energy is the lead recipient for one of two industry groups selected to receive $80 M in Department of Energy (DOE) funding as part of a public-private partnership program to demonstrate advanced nuclear power plants on an aggressive time table.

Its primary partner in the endeavor is Energy Northwest, which currently owns and operates the Columbia Generating Station in eastern Washington. Energy Northwest will be the owner and operator of the demonstration power station, which will consist of a four-unit installation of X-Energy’s Xe-100 high temperature gas cooled reactor.

Each unit is designed to produce 80 MWe, resulting in a power station output of 320 MWe.

Advanced Reactor Demonstration Program

The award is part of the Advanced Reactor Demonstration Program, which also includes two additional development pathways with longer horizons. The $80 M in FY 2021 funds is a down payment that will provide funds for completing detailed design work and beginning the licensing process.

Future appropriations will be required to complete the projects; the funding opportunity announcement for the program included an award ceiling of $4 B to be shared among three different development pathways.

For Atomic Show #287, I spoke with Darren Gale, X-Energy’s Vice President for Commercial Operations. Darren is the company executive with direct responsibility for executing the company’s contract with the Department of Energy and delivering on the promise to design, license and construct an advanced nuclear reactor power plant.

The ADRP has an aggressive target date for beginning to deliver electricity to the grid is the end of 2027. During our conversation, Darren explained how his company is positioned to deliver on its promise.

Xe-100 Design history

We spoke about how X-Energy has been working on its high temperature pebble bed reactor design for more than a decade. X-Energy was founded in 2009 by Kam Ghaffarian, a successful entrepreneur who founded Stinger Ghaffarian Technologies (SGT) in 1984. Dr. Ghaffarian remains the owner of X-Energy, but is being joined by additional investors.

The design is mature and the company has been engaging with the NRC for several years. It expects to be able to submit a license application within the next year or two; part of the uncertainty includes determining the most appropriate and streamlined licensing pathway.

The Xe-100 is a helium-cooled, high temperature pebble bed reactor that has a number of similarities to the Chinese HTR-PM. They share a common heritage tracing back through the South African HTGR program and to the German AVR demonstration reactor.

As Darren explains, the Xe-100 includes a number of refinements in its fuel design and in its fuel handling system that enable more efficient fuel use.

Another design difference is that each Xe-100 reactor/steam generator modules are connected to its own Rankine cycle steam turbine. In the HTR-PM design, two reactor/steam generator modules feed a single larger turbine.

The 80 MWe power output selection was influenced, in part, by the availability of off-the-shelf steam turbine power plants. Unlike light water reactors, the Xe-100 will produce steam at temperatures (565 ℃) and pressures (16.5 MPa) used in modern supercritical steam systems.

Like the HTR-PM, Xe-100 reactors are continuously fueled while operating, eliminating the need to schedule refueling outages. There will still be a need to periodically shut down the reactor for inspections and steam turbine maintenance. X-Energy expects that there will be more requirements during the early years of operation while the company and the regulator gain experience and understanding of operational effects.

Eventually, though, the company expects to achieve somewhat higher than average availability than conventional reactors that require unavoidable outages for refueling.

Project location

The project will be built in eastern Washington at WNP-1, a site that was licensed for construction of a nuclear power plant in 1975. Using a site that has already been reviewed and approved for use as a nuclear plant greatly reduces the amount of time and effort required for long lead time environmental impact reviews, seismic surveys, and site pre construction surveys.

Though the original plant was never completed, certain civil structures, including a water intake system and pump house were completed before the project was cancelled. Darren explained that the existing infrastructure at the site would require refurbishment, but it enables a more rapid timeline than a greenfield.

Employment opportunities

X-Energy is in the hiring mode. The Xe-100 team head count is approximately 50. Some of the necessary tasks will be completed by contractors. But Darren expects that the permanent team will expand to include 200 or more people within the next year or two.

Most of the project design work is taking place at X-Energy’s Rockville headquarters, but current restrictions related to COVID-19 have required some creative uses of remote work, multiple buildings, and video conferencing. As a result of the learning that has come with that experience, X-Energy will be somewhat flexible in allowing some employees with key skills to work from remote locations.

The Xe-100 demonstration project is an exciting opportunity for advanced reactor designers and supporters to turn ideas and concepts into functioning equipment that generates real power and heat.

I hope you enjoy this episode and participate in the comment threads, especially if you have questions that are not addressed. As you will hear towards the end of the show, Darren expects to be able to return several times during the course of the construction project.

https://s3.amazonaws.com/AtomicShowFiles/atomic_20201111_287.mp3

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Filed Under: Advanced Atomic Technologies, Gas Cooled Reactors, Graphite Moderated Reactors, New Nuclear, Pebble Bed Reactors, Podcast, Small Nuclear Power Plants

Turning nuclear into a fuel dominated business

October 28, 2018 By Rod Adams 66 Comments

Under our current energy paradigm, nuclear power has the reputation of needing enormous up-front capital investments. Once those investments have been made and the plants are complete, the payoff is that they have low recurring fuel costs. Just the opposite is said of simple cycle natural gas fired combustion turbines. They require a small capital […]

Filed Under: Adams Engines, Advanced Atomic Technologies, Business of atomic energy, Economics, Gas Cooled Reactors, Graphite Moderated Reactors, Pebble Bed Reactors, Smaller reactors

Fission heated gas turbines address MIT Future of Nuclear challenges. Easier, straighter, less costly path

September 20, 2018 By Rod Adams 57 Comments

Addressing Recommendations of MIT Future of Nuclear Energy In a Carbon Constrained World The Massachusetts Institute of Technology (MIT) is a world renowned institution that has produced thousands of highly educated engineers and scientists. It is generously supported by foundations, corporations and governments. In 2003, the MIT Energy Initiative, began publishing a series of reports […]

Filed Under: Advanced Atomic Technologies, Gas Cooled Reactors, Graphite Moderated Reactors, New Nuclear, Pebble Bed Reactors, Small Nuclear Power Plants, Smaller reactors

Will China convert existing coal plants to nuclear using HTR-PM reactors?

November 21, 2016 By Rod Adams

It would be a huge benefit to the earth’s atmosphere if China, India, Brazil and the US could reduce direct coal burning while still making use of much of the capital that they have invested in building coal fired power plants. It would make an even larger difference in reducing air pollution in the areas […]

Filed Under: Advanced Atomic Technologies, ANS Winter 2016, Climate change, Gas Cooled Reactors, Graphite Moderated Reactors, New Nuclear, Pebble Bed Reactors

U-Battery – Micronuclear power with intriguing business model

February 14, 2016 By Rod Adams 19 Comments

U-Battery was one of the more intriguing presenters at the Advanced Reactor Technical Summit (ARTSIII) held at the Oak Ridge National Laboratory last week. Even though this was a technical summit, the segments of the presentation that captured my attention were the business model and the funding source. However, certain technical choices are vital to […]

Filed Under: Advanced Atomic Technologies, ARTSIII Feb 2016, Business of atomic energy, Gas Cooled Reactors, Graphite Moderated Reactors, New Nuclear, Nuclear Batteries, Reactors, Smaller reactors

X-Energy introduced its company and first product to Virginia chapter of ANS

October 30, 2015 By Rod Adams 48 Comments

On Tuesday, October 27, three leaders from X-Energy spoke to the Virginia ANS chapter about their company and the Xe-100, the high temperature, pebble bed gas reactor power system that they are designing. During the presentation, meeting attendees learned that X-Energy is an early phase start-up with a total staff of a few dozen people, […]

Filed Under: Advanced Atomic Technologies, Atomic Entrepreneurs, Gas Cooled Reactors, Graphite Moderated Reactors, New Nuclear, Pebble Bed Reactors, Small Nuclear Power Plants, Smaller reactors

Atomic Show #238 – StarCore Nuclear co-founders

April 7, 2015 By Rod Adams

StarCore Nuclear is a Canadian company whose co-founders, David Dabney and David Poole, are experienced engineers and businessmen. They have spent most of the past six years developing a technology and a business model aimed at providing reliable, emission-free electrical power and heat to remote locations. The basis of their technology is a high-temperature helium […]

Filed Under: Advanced Atomic Technologies, Atomic Entrepreneurs, Business of atomic energy, Gas Cooled Reactors, Graphite Moderated Reactors, International nuclear, New Nuclear, Podcast, Smaller reactors

HTR-PM – Nuclear-heated gas producing superheated steam

June 27, 2014 By Rod Adams

The first HTR-PM (High Temperature Reactor – Pebble Module), one of the more intriguing nuclear plant designs, is currently under construction on the coast of the Shidao Bay near Weihai, China. This system uses evolutionary engineering design principles that give it a high probability of success, assuming that the developers and financial supporters maintain their […]

Filed Under: Advanced Atomic Technologies, Gas Cooled Reactors, Graphite Moderated Reactors, International nuclear, New Nuclear, Pebble Bed Reactors, Small Nuclear Power Plants, Smaller reactors

Fission is an elegant way to heat a gas

June 26, 2014 By Rod Adams

What if it was possible to combine the low capital cost, reliability, and responsive operations of simple cycle combustion gas turbines with the low fuel cost and zero-emission capability of an actinide (uranium, thorium, or plutonium) fuel source? Machines like that could disrupt a few business models while giving the world’s economy a powerful new […]

Filed Under: Adams Engines, Advanced Atomic Technologies, Gas Cooled Reactors, Graphite Moderated Reactors, Pebble Bed Reactors, Small Nuclear Power Plants, Smaller reactors

The first Critmass, December 2, 1942

December 2, 2013 By Rod Adams

Seventy one years ago — on December 2, 1942, at 3:25 pm — Enrico Fermi and his team achieved the first controlled, man-made, self sustaining chain reaction in a simple reactor. In recognition of that historical event, several of my nuclear colleagues refer to December 2 as “Critmass” (short for critical mass). The first nuclear […]

Filed Under: Atomic history, Atomic Pioneers, Graphite Moderated Reactors, Technical History Stories

Advances in high temperature nuclear reactor fuel – TRISO integrity at 1800 C!

September 26, 2013 By Rod Adams

The Idaho National Laboratory released the following exciting news on September 25, 2013. IDAHO FALLS — A safer and more efficient nuclear fuel is on the horizon. A team of researchers at the U.S. Department of Energy’s Idaho National Laboratory (INL) and Oak Ridge National Laboratory (ORNL) have reached a new milestone with tristructural-isotropic (TRISO) […]

Filed Under: Advanced Atomic Technologies, Fuel Comparisons, Gas Cooled Reactors, Graphite Moderated Reactors, Pebble Bed Reactors

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