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Mobile Nuclear Power Reactors Won’t Solve the Army’s Energy Problems

Imagine the following scenario: A punishing conflict between NATO and Russia grinds on in Eastern Europe as winter closes in. Poland, starved of natural gas and with its civilian power grid under recurring cyberattack, suffers supply-line interruptions and unprecedented diesel shortages. NATO forces find themselves unable to meet their own energy needs at major bases. Does the missile defense radar stay on or the heat? Should the base prioritize powering up the drone-killing close-in weapons system or the surface-to-air missile battery? Some in the U.S. Army believe that using nuclear energy can make these unenviable choices completely avoidable.

As China and Russia develop microreactors for propulsion, the Department of Defense Strategic Capabilities Office is pursuing the ultimate in self-sufficient energy solutions: the capability to field mobile nuclear power plants. In this vision of a nuclearized future, the Army will replace diesel generator banks with microreactors the size of shipping containers for electricity production by the mid-2020s.

Nuclear power is 10 million times more energy dense than fossil fuels and seems to be the ideal solution to securing a robust supply of electricity for the Army free of supply-line vulnerabilities. However, the question is whether or not reactors can truly be made suitable for military use. Are they an energy panacea, or will they prove to be high-value targets capable of crippling entire bases with a single strike? The Army’s nuclear power program is confidently sprinting into uncharted territory in pursuit of a solution to its growing energy needs and has promised to put power on the grid within three years. However, the Army has not fielded a reactor since the 1960s and has made claims of safety and accident tolerance that contradict a half-century of nuclear industry experience.

The Army appears set to credulously accept industry claims of complete safety that are founded in wishful thinking and characterized by willful circumvention of basic design safety principles. Decades of technological advancements in reactor controls and material science will allow these reactors to easily avoid the flaws that precipitated the SL-1 accident, the Army’s last nuclear disaster in 1961. However, over-reliance on a single safety mechanism, the impermeability of the fuel cladding, and refusal to accept the possibility of a release of radioactive material risks an entirely different mode of failure. If deployed without clear-headed understanding of the risks of nuclear power and preparation for significant releases of radioactive material, the Department of Defense risks incurring costs far greater than those of fuel delivery. These risks go far beyond the physical dangers of an attack with radiological consequences. Additionally, the introduction of nuclear power to the battlefield may corrode national security by heightening inter-alliance tensions and familiarizing adversaries with tactics for attacking nuclear infrastructure.

Why the Army Is Considering Mobile Nuclear Power Reactors

The advent of highly networked systems, drones, and battlefield computation is making war increasingly energy-intensive. At least some parts of the U.S. Army think that nuclear power could address some of these problems. In addition to providing energy in austere, hostile terrain, the Department of Defense hopes to use nuclear power to provide electricity to forward operating bases with insecure supply lines and to power large installations in the case of outages impacting the civilian power grid. Though the initial siting of these reactors is likely to be in extremely remote areas such as Guam and Kwajalein, the intent is to adopt these systems across a variety of Department of Defense installations as a means of meeting electrical power needs in the absence of reliable fuel supplies.

Studies by the Defense Science Board and the Department of Defense have identified growing power requirements at forward operating bases as a significant emerging issue and recommend the pursuit of nuclear energy in response. This logic is driven in part by the development of ever more energy-intensive weapons systems as well as analysis that suggests the diesel supply chain for electricity generation has contributed significantly to casualties in past conflicts. As highlighted in a 2018 Army deputy chief of staff study, 52 percent of causalities in Iraq resulted from attacks on land transport missions.

Reactors require infrequent refueling and can therefore dramatically cut the volume of material necessary for the maintenance of military installations, alleviating the costs associated with the hydrocarbon supply chain. In theory, the adoption of such systems could enable greater independence and resiliency when operating far from infrastructure or in highly contested environments. According to proponents of these systems, this capability can be incorporated into the military rather soon. Such reactors are set to provide the Defense Department with “deployable, reliable, resilient and safe operational power for a variety of missions” by the mid-2020s.

A Mobile Nuclear Power Plant Is Not Worth the Risk

The U.S. Army’s mobile nuclear power plant development program is centered on Project Pele, a truck-and-air-transportable microreactor. Pele promises a 1–5 megawatt electric power (1–5 MW(e)) system weighing less than 40 tons and with exterior dimensions compatible with transport by a C-17 transport aircraft. This reactor is intended to be deployed and started up on extremely short notice at otherwise minimally prepared sites, and is intended for deployment at forward operating bases as well as remote sites. This project has progressed rapidly, garnering $133 million in Fiscal Years 2020–2021, with $28 million distributed each to BWX Technologies and X-energy for the development of designs for mobile, small modular reactor systems in 2020. The design phase of the program will terminate in 2022 with “full power testing feasible by the end of 2023,” an astonishingly short timeline in comparison to commercial reactor systems.

According to its proponents, Project Pele will offer a walk-away-safe, accident-tolerant reactor that uses advanced heat transfer technologies and tri-structural isotropic (more commonly known as TRISO) fuel. To maximize transportability, Project Pele’s reactor designs do not rely on deep burial or concrete castings for protection of the core from kinetic attack but instead use the traditional last line of defense — fuel cladding, a thin protective layer that prevents radioactive products from leaving the fuel — as the barrier to catastrophic radiation release. The total mass limit for the Pele reactor (40 tons, or a bit less than an M1 Abrams) leaves very little room for armor. In response to this, the program manager for Project Pele has presented tri-structural isotropic fuels as nearly invulnerable, stating that the fuel materialis a “real game-changer” and that “even in the case of an attack, [the reactor] is not going to be a significant radiological problem.” In the case of a reactor attack, the program does not “require highly specialized training and equipment for forward area emergency response staff because these locations typically possess only simple emergency response equipment and limited emergency staff.”

These requirements conflict directly with the operational history of tri-structural isotropic fuels, the fundamental physical properties of reactor fuel, and its behavior in extreme environments. While resilient to high temperatures and robust in comparison to conventional reactor fuel, tri-structural isotropic particles are far from invulnerable. In normal operation, they release potentially hazardous quantities of fission products that would be widely distributed by any penetration of the reactor vessel. More worryingly, the resiliency of tri-structural isotropic particles to kinetic impact is questionable: The silicon carbide coating around the fuel material is brittle and may fracture if impacted by munitions. Further, graphite moderator material, which is used extensively in most mobile power plant cores, is vulnerable to oxidation when exposed to air or water at high temperatures, creating the possibility of a catastrophic graphite fire distributing radioactive ash. Even in the case of intact (non-leaking) fuel fragments being distributed by a strike, the radiological consequences for readiness and effectiveness are dire.

Given these vulnerabilities, sophisticated adversaries seeking to hinder U.S. forces are likely to realize the utility of the reactor as an area-denial target. In comparison to typical area-denial tactics that require constant use of munitions and can only continue as long as those munitions last, a reactor strike offers months of exclusion at the cost of only a few well-placed high-explosive warheads, a capability well within reach of even regional adversaries, as demonstrated by Iran’s attack on Al Asad air base. While these reactors are not intended to be deployed on the front lines of a conflict, and would reside in well-guarded revetments, a major aspect of the rationale for placing these reactors at forward operating bases is their proximity to conflict and the likelihood of attacks on their supply lines. Likewise, the requirements laid out in Pele make it clear that these reactors will not be buried or encased in concrete, as they are intended to be rapidly mobile. The consequences of a reactor strike are serious and deployment of these systems requires both detailed understanding and extensive preparation for the radiological consequences of a strike.

Even assuming that the fuel material does not leak fission products under the thermal and mechanical shock of an attack, direct irradiation from reactor fuel fragments will pose a hazard that cannot be mitigated by defense equipment for chemical, biological, radiological, nuclear, and high yield explosives. The gamma dose rate at 50cm from a pea-size tri-structural isotropic fuel fragment with burnup similar to what would be anticipated at the end of a fuel cycle would impart a near-fatal dose in under an hour. Such fragments could easily settle on or lodge in equipment, as seen in the cleanup effort following Chernobyl, rendering it useless. It is conceivable that the exclusion area resulting from a successful reactor strike could force large sections of a base to be evacuated for weeks or months due to the external radiation exposure threat alone.

An attack against a mobile nuclear reactor resulting in the release of fission products could pose a contamination hazard that would render materiel useless, even if fuel fragments are successfully located and removed. Should 1 percent of the fuel particles be damaged in a kinetic attack, tens of kilocuries of volatile fission products would be released. Many of these radioisotopes would react with air, water, and soil to create mobile radioactive contamination that would require topsoil removal; disposal of equipment; and extensive, dose-intensive decontamination using caustic agents and media-blasting. As a point of comparison, decontamination of aircraft used in the response at Chernobyl proved so costly that dozens of military helicopters were decommissioned and left to rust at the accident site even as the Soviet Union pursued a campaign in Afghanistan that was heavily reliant on those aircraft.

Even an unsuccessful or minimally damaging attack on a reactor could offer an adversary significant benefits. Due to the risk of radiological release, moderate damage incurred by a reactor installation through a small attack would lead to a significantly extended shelter-in-place order to evaluate consequences in comparison to an attack on a conventional power system. This effect may be used synergistically, allowing the adversary to concentrate or distract personnel for an extended time, potentially increasing the effectiveness of other attacks. This offers the adversary a significantly greater ability to degrade readiness, hold personnel at risk, and decrease morale with minimal expenditure: A strategy that may be especially attractive to adversaries incapable of destroying the reactor outright.

The presence of mobile reactors also threatens to increase intra-alliance tensions, as a number of NATO states and allies have strong anti-nuclear movements and significantly more negative views of nuclear power than the U.S. public. Even in areas where attacks are exceedingly unlikely, the presence, transport, and operation of such reactors have the potential to be a divisive “wedge” issue highly vulnerable to disinformation and propaganda campaigns. Adversaries may latch on to the public’s fear of radioactive contamination from mobile nuclear plants to create anti-American sentiment. Should a reactor be compromised by an adversary attack to any degree, the incident will have massive propaganda value, damaging the international standing of the United States and bolstering opposition to partnerships.

Additionally, placing these reactors in combat zones introduces nuclear reactors as valid military targets, which will familiarize adversaries with the tools and tactics needed to attack nuclear infrastructure. Non-state actors may be able to apply their experience attacking military installations to civilian nuclear infrastructure outside of the theater. While reactors deployed in combat zones will be hardened against such attacks, civilian infrastructure cannot be shielded to the same extent. By deploying these systems to the battlefield, the United States may inadvertently help adversaries build a toolkit to export nuclear terror.

Looking Ahead

While mobile nuclear power plants may offer tactical benefits to supply-line robustness and power reliability at a variety of installations, the publicly available information on the Army’s current flagship project fails to address major strategic issues involved in the development and deployment of small reactors. By expanding the application of small nuclear power plants from remote bases unlikely to face attack to forward operating bases, the majority of nuclear power’s benefits are negated and significant risks introduced. Future work in this field should prioritize “big-picture” thinking about how small reactors may be useful in U.S. military planning with detailed attention to minimizing radiological risk, preserving alliances, and maintaining global nuclear security.

Jake Hecla is a graduate student in the Department of Nuclear Engineering at the University of California, Berkeley. His work focuses on the development of technologies applicable to nuclear nonproliferation. His current work focuses on neutrino detection for nonproliferation, and applications of coded-aperture imaging for radiation localization and mapping.

Update: A previous version of this article stated that the U.S. Army was “pursuing … the capability to field mobile nuclear power plants.” While the customer for this project is the U.S. Army, the funding comes from the U.S. Department of Defense Strategic Capabilities Office.

Image: U.S. Army

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