Nuclear Thermal Propulsion is Key Enabling Technology for DARPA Effort

  • DARPA project for nuclear thermal propulsion adds a second track for system integration of two previously awarded contracts
  • NAS ~ For Humans to Reach Mars Advances Are Needed in Space Nuclear Propulsion Technologies Especially in Fuels
  • Fuel Tests / NRG To Begin Irradiation Program For USNC’s Micro Reactor
  • Romania Ratifies Cernavoda Agreement with US
  • Japan / Ministry’s Green Growth Strategy Calls For Fast Reactor And SMR Development
  • DOE Posts FAQ on Future of Nuclear Energy Policies with Acting NE-1 Dr. Kathryn Huff

Nuclear Thermal Propulsion is Key Enabling Technology for DARPA Effort

The U.S. Defense Department’s Advanced Research Projects Agency (DARPA) wants to use nuclear power to send astronauts to the Moon and Mars, and to provide electrical power for their use once they arrive. To this end last April the agency awarded funding to three firms in two “tracks.”

Track A, focused on the baseline design of a nuclear thermal propulsion reactor, and Track B, focused on the operational spacecraft upon which to demonstrate it. Subsequent phases will lead to the detailed design, manufacture, ground tests, and an in-space demonstration of the Draco NTP system.

A third firm, Ultra Safe Nuclear Technologies (USNC-Tech) is providing critical support to both prime contractors in the first phase of the Demonstration Rocket for Agile Cislunar Operations (Draco) program. Draco will develop a nuclear thermal propulsion (NTP) system for cislunar operations, targeting a full-scale, on-orbit demonstration in 2025. USNC-Tech is the only company participating in both Track A and Track B teams.

Awards for Track A

DARPA has awarded contracts for the first phase of the Demonstration Rocket for Agile Cislunar Operations (DRACO) program. The goal of the DRACO program is to demonstrate a nuclear thermal propulsion (NTP) system above low Earth orbit in 2025. The three prime contractors are General Atomics, Blue Origin, and Lockheed Martin..

NAS NTP Propulsion

Conceptual Image of a Nuclear Thermal Propulsion System:
Image: National Academy of Sciences

Rapid maneuver is a core tenet of modern Department of Defense (DoD) operations on land, at sea, and in the air. However, rapid maneuver in the space domain has traditionally been challenging because current electric and chemical space propulsion systems have drawbacks in thrust-to-weight and propellent efficiency.

Activity in cislunar space is rising as space agencies and companies around the world pursue new lunar ambitions, DARPA said. To ensure the accessibility of cislunar space for US government and commercial activities, the US Department of Defense (DOD) must develop new degrees of orbital mobility.

The White House in December 2020 issued a memorandum establishing a national strategy to ensure the development and use of space nuclear power and propulsion systems, including NTP systems, which can power spacecraft for missions where alternative power sources are inadequate.

The technology being developed under the DRACO program could also be foundational to future operations beyond cislunar space, such as the development of an NTP system for the first human missions to Mars.

Cislunar space (alternatively, cis-lunar space) is the volume within the Moon’s orbit, or a sphere formed by rotating that orbit. Volumes within that such as low earth orbit (LEO) are distinguished by other names. Cis-lunar is Latin for “on this side of the moon” but also “not beyond the moon.”

“The performer teams have demonstrated capabilities to develop and deploy advanced reactor, propulsion, and spacecraft systems,” said Maj Nathan Greiner, USAF, program manager for DRACO.

“The NTP technology we seek to develop and demonstrate under the DRACO program aims to be foundational to future operations in space.”

“This first phase of the DRACO program is a risk reduction effort that will enable us to sprint toward an on-orbit demonstration in later phases,” added Greiner.

Award for Track B

With its two partners, USNC-Tech will create a pathway to the first on-orbit demonstration of an NTP system. Subsequent phases will lead to the detailed design, manufacture, ground tests, and an in-space demonstration of the Draco NTP system.

“This is a remarkable moment for NTP development and for our company,” said Dr Paolo Venneri, Executive Vice President of USNC-Tech. “Our selection to participate in not one but two teams for the Draco program shows the strength of our ability to design and analyze these high-performance systems.”

“The United States must emerge as the leader in cislunar space, and our innovative NTP technologies will empower our commercial, NASA, and national security customers to accomplish just that,” said Dr Michael Eades, Director of Engineering at USNC-Tech and company lead for reactor development in Track B.

“Even with the difference in scale of engine and spacecraft, a successfully demonstrated DRACO NTP can directly influence and speed up demonstration of a NASA NTP, said Vishal Patel, analysis lead at USNC-Tech and company lead for spacecraft development in Track A.

As highlighted in the recent study of space nuclear propulsion systems completed by the National Academies of Science, Engineering, and Medicine, some of Draco’s technological achievements could contribute to NASA’s development of an NTP system for its first human missions to Mars.

Mars missions with nuclear thermal propulsion

Profile of Mars Missions Using Nuclear Thermal Propulsion.
Image: National Academy of Sciences

By requiring the use of high-assay low-enriched uranium (HALEU) in Draco, DOD will support the maturation of critical technologies, supply chains, and talent pools directly applicable to the NTP system that NASA is partnering with the Department of Energy (DOE) to produce.

NAS ~ For Humans to Reach Mars Advances Are Needed in Space Nuclear Propulsion Technologies Especially in Fuels

Using nuclear propulsion technologies to support a human mission to Mars in 2039 will require NASA to pursue an aggressive and urgent technology development program, says a new report from the National Academies of Sciences, Engineering, and Medicine.
Public Briefing Slides – PDF file

Space Nuclear Propulsion for Human Mars Exploration” assesses the primary challenges, merits, and risks for developing a nuclear electric propulsion (NEP) system and a nuclear thermal propulsion (NTP) system for a human mission to Mars.

While NEP converts the thermal energy from a nuclear reactor into electrical energy to power electric thrusters, NTP uses the thermal energy from a nuclear reactor to heat a rocket propellant and create thrust. Each system has its own advantages and limitations for use in a crewed mission to Mars.”

Studies comparing NEP and NTP systems are needed to assess the viability of each system for a crewed mission to Mars. Given the need to send multiple cargo missions to Mars prior to the first crewed mission, NASA should use those cargo missions as a means of flight qualification of the selected nuclear propulsion system before it is incorporated into the first crewed mission.

NEP and NTP each have challenges, which are identified in the report. The fundamental challenge for developing an NEP system is scaling up the operating power for each subsystem, something that requires power levels that are orders of magnitude greater than have ever been achieved to date.

Another challenge is developing a compatible chemical propulsion system to provide the primary thrust when departing Earth’s orbit and when entering and departing Mars’ orbit.

The fundamental challenge facing an NTP system is the ability to heat its propellant to the proper temperature, approximately 2,700 K. Other challenges include the long-term storage of liquid hydrogen in space with minimal loss; the need to rapidly bring an NTP system to full operating temperature, preferably in under one minute; and the need to develop full-scale ground test facilities that can safely capture the NTP exhaust.

Fuels are Key Challenges for Design of Nuclear Thermal Propulsion

With regard to fuels, including the use of highly enriched uranium, NAS said in its report,

FINDING. Enrichment of Nuclear Fuels. A comprehensive assessment of HALEU vs HEU for NTP and NEP systems that weighs the key considerations is not available. These considerations include technical feasibility and difficulty, performance, proliferation and security, safety, fuel availability, cost, schedule, and supply chain as applied to the baseline mission.

RECOMMENDATION. Enrichment of Nuclear Fuels. In the near term, NASA and DOE, with inputs from other key stakeholders, including commercial industry and academia, should conduct a comprehensive assessment of the relative merits and challenges of HEU and HALEU fuels for NTP and NEP systems as applied to the baseline mission.

FINDING. NTP Fuel Characterization. A significant amount of characterization of reactor core materials, including fuels, remains to be done before NASA and DOE will have sufficient information for a reactor core design.

RECOMMENDATION. NTP Fuel Architecture. If NASA plans to apply NTP technology to a 2039 launch of the baseline mission, NASA should expeditiously select and validate a fuel architecture for an NTP system that is capable of achieving a propellant reactor exit temperature of approximately 2700 K or higher (which is the temperature that corresponds to the required ISP of 900 sec) without significant fuel deterioration during the mission lifetime. The selection process should consider whether the appropriate fuel feedstock production capabilities will be sufficient.

“Space nuclear propulsion technology shows great potential to facilitate the human exploration of Mars,” said Bobby Braun, director for planetary science at the Jet Propulsion Laboratory and co-chair of the committee that wrote the report.

“However, significant acceleration in the pace of technology maturation is required if NASA and its partners are to complete this mission within the stated timeline.”

Fuel Tests / NRG To Begin Irradiation Program For USNC’s Micro Reactor

(NucNet) Netherlands-based NRG is to carry out a program of irradiation tests on Ultra Safe Nuclear Corporation’s (USNC) proprietary fully ceramic microencapsulated (FCM) fuel at the high flux reactor in Petten.

NRG said the aim of the tests is to demonstrate the safety of the fuel for the 20-year lifespan of Seattle-based USNC’s micro modular reactor. NRG said extensive pre- and post-irradiation tests at its hot cell laboratories will be part of the program.

FCM fuel is a next-generation tristructural-Isotropic (Triso) particle fuel design, replacing the 50-year-old graphite matrix of traditional Triso fuel with silicon carbide, a material that is extremely resistant to radiation and thermal damage.

triso fuel pellets


The SiC matrix in FCM fuel provides a dense, gas-tight barrier, preventing the escape of fission products even if a Triso particle should rupture during operation. The result is a safer nuclear fuel that can withstand higher temperatures and more radiation.

NRG said the higher-thermal conductivity of FCM fuel allows the fuel pellet to have a flatter temperature profile, lowering peak temperatures in nuclear reactors. Unlike conventional nuclear fuels, FCM fuel achieves full-fission product containment across a wide range of temperatures that include operating and failure conditions.

USNC’s micro modular reactor is a 15 MW thermal, five MW electrical high-temperature gas-cooled system with a design that draws on operational experience from reactors developed by China, Germany, Japan and the US. USNC has said it hopes to build and operate a unit by 2026.

The plant consists of two systems: a nuclear plant that generates heat and a power plant that converts heat into electricity or provides process heat for industrial applications. It uses fuel in prismatic graphite blocks and has a sealed transportable core.

The micro modular reactor is at an advanced licensing stage at Atomic Energy of Canada Limited’s Chalk River Laboratories campus in Ontario. The project is a collaboration between USNC and Ontario Power Generation through jointly owned Global First Power Limited Partnership .

Last month, Global First Power’s application for a licence to prepare a site for an MMR at Chalk River moved to the technical review phase of the Canadian Nuclear Safety Commission’s licensing process.

Romania Ratifies Cernavoda Agreement with US

(WNN) The Romanian Senate, the upper house of the country’s parliament, has ratified an intergovernmental agreement on cooperation to expand and modernize Romania’s nuclear power program that was signed between Romania and the USA in October 2020. Areas for cooperation could include the completion of units 3 and 4 at the Cernavoda nuclear power plant and the refurbishment of unit 1 at the plant.

Cernavoda is the only nuclear power plant in Romania and consists of two 650 MWe pressurized heavy-water reactors. Unit 1 went into commercial operation in 1996 and unit 2 in 2007. Operator Nuclearelectrica plans to extend the operating life of unit 1 to 60 years.

Most of the work on units 3 and 4 – like units 1 and 2, CANDU-6 reactors – was done in the 1980s prior to the fall of the government of Nicolae Ceausescu in 1989. In July 2020, Romania launched a tender for a new feasibility study to complete units 3 and 4.

According to the Senate’s website, there were 129 votes in favour of the bill, one against and one abstention. It bill will now be forwarded to Romanian President Klaus Iohannis for his approval.

It’s not clear what the current administration thinks of the agreement which was pushed by the Trump administration as part of an effort to block China’s aggressive export effort for its home grown nuclear reactor the Hualong One which is a 1000 MWe PWR.

The Trump administration promised Romania $8 billion in cash and inkind support for its efforts to complete the two PHWRs. However, so far the Biden administration has not made any public statements about the deal. Given the DOE has only an Acting Assistant Secretary for Nuclear Energy, and a brand new Secretary for the agency as a whole, it could be a while before anything definitive is forthcoming from the U.S. government.

Japan / Ministry’s Green Growth Strategy Calls For Fast Reactor And SMR Development

(NucNet) An updated green growth strategy calls for Japan’s nuclear energy industry to cooperate internationally on fast reactor development and the demonstration of small modular reactor technology, industry group the Japan Atomic Industrial Forum (Jaif) said.

According to Jaif, the strategy, published by Japan’s ministry of economy, trade and industry (Meti) did not include any reference to fast reactor development in an earlier version December 2020.

The strategy calls for the establishment by 2030 of technology for the production of hydrogen using high-temperature, gas-cooled reactors (HTGRs) and commitment to nuclear fusion through international cooperation, including the €20bn International Thermonuclear Experimental Reactor (Iter) nuclear fusion project at Cadarache in the south of France.

Jaif said wording was removed from the original strategy that had called for maximizing the use of nuclear energy. However, a new item was added calling for the promotion of nuclear-related R&D and the training of personnel for the industry.

In the past year Japan has inked an R&D agreement with Poland for development of an HTGR design for commercial use. Poland’s National Centre for Nuclear Research (NCBJ) and the Ministry of Education and Science (MEiN) have signed a contract for design work on a high temperature gas cooled reactor (HTGR).

Under the agreement, plans for  construction of the HTGR will be prepared within three years at NCBJ, which will also develop the basic design, based on technical input from Japan, at a cost of $16.2M.

Japan does not have an SMR project under development and may have to seek a partner from another country to develop a useful design for commercial sale.

DOE Posts FAQ on Future of Nuclear Energy Policies with Acting NE-1 Dr. Kathryn Huff

In her first general policy statement since taking office, Acting Assistant Secretary for Nuclear Energy at DOE, Dr. Kathryn Huff, said she has three priorities.

“First and foremost, the preservation of the existing fleet in the United States is essential to our climate goals. Second, the deployment of new advanced reactor types will underpin our continued leadership in nuclear technology and our needed direction in the context of climate action. Finally, this is only possible if DOE makes progress in the context of an energy- and environmental-just consent-based siting approach process for interim and eventually permanent spent nuclear fuel storage.”

The complete interview is online at the DOE nuclear energy home page.

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