The Army Times reports in an good article, with fascinating graphics, that the US Army is seeking to develop and put in the field a number of very small mobile nuclear reactor to power forward operating bases.

The basic approach is to acquire mobile nuclear reactors the would produce electrical power in the range of one-to-ten megawatts of power.  An earlier report on the Army’s interest in SMRs was published by Defense One in September 2018.

The specifications for the acquisition of these mini-reactors, sometimes referred to incorrectly as “nuclear batteries,” was published in the Federal Business Opportunities aka FedBizOps on 22 January 2019. The announcement came with a detailed list of operational and physical requirements. This announcement is a “Request for Information,” or RFI.  A full blown Request for Proposals (RFP) could be issued later this year.

Note to Readers ~ 04 March 2019 – the correct designation of the issuing office of the RFI is the Office of the Secretary of Defense, Strategic Capabilities Office aka OSD/SCO as an acronym. References to the US Army actually refer to this part of the Pentagon.

The reactors would produce 1-10MWe of electrical power, weight less than 40 tons, be capable of being set up and running after delivery by a C-17 in less than 72 hours; and, run more or less unattended for up to three years.

Benefits for Commercial SMR Developers

If the Army is successful in developing and deploying these mini reactors, the supply chain created by producing them could be capitalized by current and future developments of small modular reactors.

Additionally, assuming the US Army produces enough of them, that cost and schedule data from the line might finally answer the question of how many orders a commercial SMR developer needs to start up its own production line. Note the Army is unlikely to  want to share a production capability needed to assure tactical readiness at forward bases.

The testing and safety review processes for the military reactors would also provide test cases for use by commercial reactors and also inform the NRC about getting smart on these types of reactors. According to the Army Times report test efforts are expected to take place at the Idaho National Laboratory. A spokesperson for the INL told this blog the lab is in discussion with several entities interested in demonstrating reactor concepts in Idaho.

The RFI says that the Defense Department could pick three prototypes for its phase I portion of development. That would require prototype designs and other plans. That phase would go for nine to 12 months, according to the post. The Idaho National Laboratory is cited as offering an estimate that testing and demonstrations could begin as early as 2021.

Use of High Assay Low Enriched Fuel

The  requirements for the reactors, and their small size, indicate that conventional light water reactor designs won’t meet the Army’s needs for portability and rapid set up in forward areas.  It follows that to avoid using highly enriched fuel (HEU), the Army will be more likely to see proposals from vendors that involve the use of high assay low enriched fuel (HALEU) which is uranium fuel with levels of U235 between 5% and 19%.

Note that the Department of Energy has several initiatives underway to produce HALEU and potential military mini SMRs have long been seen as one of the early users of this type of fuel.

Background to the Request for Information

The Army Times reports that Defense Science Board task force published a detailed report in August 2016 (large PDF file) with details of the power requirements in the range of 1-10 MW.  In 2018, the Times notes, the Army’s deputy chief of staff, G-4, published a 148-page study on the use of mobile nuclear power plants for ground operations, adopting the recommendations of the 2016 Defense Science Board. It also advocated, as the board did, that the Army manage ground nuclear reactor programs and pursue existing or near-to-maturity technologies.

In August, 2016, the Defense Science Board identified key gaps in its report: Energy Systems for Forward Remote Operating Bases that the Army is interested in responding to these needs by developing a small mobile nuclear reactor design that can address electrical power needs in rapid response scenarios.

The report said that small mobile nuclear reactors “can make the DOD’s domestic infrastructure resilient to an electrical grid attack and fundamentally change the logistics of forward operating bases, both by making more energy available and by drastically simplifying the complex fossil fuel logistical lines which currently support existing power generators operating mostly on diesel fuel.”

Additionally, a small mobile nuclear reactor would enable a more rapid response during Humanitarian Assistance and Disaster Relief (HADR) operations.

Current Technical Requirements in the RFI

For purposes of this RFI, the Army is interested in small mobile nuclear reactor concept designs that produce electricity and which satisfy, at minimum, the following requirements:

• Threshold Power: 1-10 MWe of electric power generation
• Size/Transport: < 40 tons total weight, sized for transport by truck, ship, and C-17 aircraft
• Inherently safe design, ensuring that a meltdown is physically impossible in various complete failure scenarios such as loss of power/cooling.
• Ultimate heat sink: Ambient Air, capable of passive cooling
• Time to Install and reach Point of Adding Heat (POAH): Threshold: <72 hrs
• Life: Able to generate threshold power (1-10 MWe of electric power generation) for >3 years without refueling
• Time for planned shutdown, cool down, disconnect and removal for transport:  Threshold: < 7 days
• Operation: Semi-autonomous – Not requiring manned control by operators to ensure safe operation. Minimal manning to monitor overall reactor and power plant system health
• Safe Shutdown: Series of both automatic shutdowns as well as failsafe shutdowns with passive cooling upon loss of power
• Health & Safety: No net increase in risk to public safety by either direct radiation from operation or contamination with breach of primary core. Minimized consequences to nearby personnel in case of adversary attack
• Proliferation: Technology, engineering, and operations must demonstrate minimization of added proliferation risk.

Key Advantages of SMRs

The military’s interest in SMRs comes from understanding of five distinct features of solid state designs.

Black Start – SMRs can start up from a completely de-energized state without receiving energy from the grid. This can help an electricity grid meet system requirements in terms of voltage, frequency and other attributes when recovering from an outage.

Islanding– SMRS can operate connected to the grid or independently. If attached to a microgrid with islanding, an SMR could power critical facilities such as hospitals, data centers and military bases.

Fuel Security – SMRs can easily store fuel on-site, allowing them to run, in some instances, for a decade or more without the need of an external fuel supply.

Plants can also stagger the refueling of its modules—allowing them to stay online and provide constant power to the grid without any disruptions.

Modularity – SMRs have a modular design that minimize the use of electrical parts. Many of them use passive cooling features that don’t require any safety-related electric pumps or operator intervention to safely shut down.

Construction – If needed SMRs can be built underground—making them less vulnerable to extreme weather events, earthquakes, electromagnetic pulse (EMP) threats and other intentional destructive acts.

Los Alamos Design for a Mini SMR and  by Others

In September 2018 officials at Los Alamos National Laboratory released details of work taking place there to build a very small reactor to meet the military’s needs.

In the LANL microreactor, the nuclear fuel is HALEU. The fuel is encapsulated in a solid steel monolith to form a sub-critical nuclear core, which is surrounded by a neutron reflector and contains a simple shut-down rod that allows the core to go critical on demand.

The thermal energy created by the fission reactions is efficiently removed from the metal core by high-temperature, alkali-metal heat pipes, a technology in wide use both on earth and in space since the 1970s. Thermal energy is converted into electrical energy—and power is delivered.

A related patent was filed by staff working for the prime contractor at Los Alamos in 2014 for a very small SMR.

The start up HolosGen has some interesting approaches to portability for its 3-13MWe design that comes in a 4-pack configuration that, according to its briefing materials on its web site, would fit inside a truck trailer that could easily navigate ordinary highways.  A slide deck (PDF file) dated April 2018 walks a reader through the details of their design concepts and potential applications including military uses for reliable power.

See also a July 2017 report by the technology blog Next Big Future on various designs by developers of very small fission reactors for military and space applications. Note that some developers of applications for NASA might also see an opportunity to meet the ARMY’S needs.

A directory of developers and related supply chains for advanced reactors was published by  the Gateway for Accelerated Innovation in Nuclear (GAIN), at the Idaho National Laboratory, in January 2019.  Several developers listed in the directory are working on very small reactors.

How feasible or acceptable any of these designs would be to the military is up to DOD.

How the Program Decisions Will Develop Over Time

The language of the RFI is couched in typical government speak. Here is a summary of the decision process.

• Up to three (3) different reactor design efforts may be awarded under Phase I.

The Phase I effort will be a full-scope reactor prototype engineering design study, complete with a programmatic plan to address specifically enumerated risks, along with engineering and manufacturing concerns to articulate feasible path from design to build.

Phase I is anticipated to be a 9-12 month effort, with a defined schedule and specific milestones to be identified in a follow on announce once the acquisition method is determined.

Phase I awardees will work to develop a prototype design for a small mobile nuclear reactor, and produce a programmatic design-to-build plan including a risk reduction testing path for a successive Phase II award.

Routine updates will be required to be submitted to the government for technical progress and evaluation purposes. Final deliverables will require specific risk mitigation actions germane to the specific reactor type design being developed, as well as reaching the equivalent of a Preliminary Design Review (PDR) for full scale design and build.

Phase II will include a complete build and testing of the system prototype.Following a down select to one of the Phase I awardees, a Phase II may proceed with material purchases, execution of the delivered program plan, and building on the existing prototyping design work produced under Phase I.

An announcement following determination of acquisition method is expected for release in Spring 2019. It will include the specific technical requirements, which will be informed in part by the information solicited in the current RFI.

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