Should the Pentagon invest in microreactors?

It’s not clear whether the Department of Defense should continue to develop new types of microreactors — primarily because they have uncertain costs and regulations. However, we can use a systematic and repeatable framework for plugging in such information as it becomes available to pave the way for effective DoD investment decisions. We can even use presently available data and information to identify preliminary findings.

For example, the smallest microreactors, which have a power capacity of 1-5 megawatt electric, are too expensive for almost all DoD locations in the United States when comparing average electricity costs to the status quo energy costs — even when a cost of carbon, value of energy resiliency and manufacturing efficiencies are included.

On the other end of the spectrum, larger, advanced nuclear reactors (80-300 MWe) have a lower average cost of electricity but produce too much power for almost any DoD location to consume independently.

In between these two extremes, a medium-sized microreactor (17 MWe) could be a worthwhile investment for up to 21 different DoD locations in the United States .

Regardless of their size, microreactors have significant capital costs. The DoD recently announced a $300 million contract to design, construct and test a microreactor prototype. This is between four and 20 times greater than construction cost estimates from a Nuclear Energy Institute report published in 2019. Although the contract includes more than just construction, the significant cost increase aligns with themes from research out of the Massachusetts Institute of Technology — that nuclear power plant construction cost estimates tend to increase as the microreactor matures from a concept to a prototype.

Rather than just looking at construction costs, a more effective way to compare different electricity-generation sources is their levelized cost of electricity, which is the average cost of electricity over the entire life span. For microreactors, this is largely dependent on how much power can be produced in an instant — the power capacity, or MWe — the percentage of full power capacity delivered over time — the capacity factor as a percentage — and how manufacturing efficiencies decrease costs for each subsequent unit.

Microreactors are more cost-effective if they have a large power capacity (MWe), if they are used consistently for their entire life span (a capacity factor near 100%) and if numerous units are implemented.

The preliminary findings above focus on siting microreactors at DoD locations in the United States. This allows them to have a larger power capacity (MWe) than portable or mobile reactors. The analysis also required DoD locations to have an average power demand greater than the microreactor’s power capacity (MWe) to ensure the microreactor is used consistently for its life span. This increases the capacity factor closer to 100% and keeps the average cost of electricity as low as possible.

Because most DoD locations have relatively low average power demand, there is a trade-off between microreactors with a larger power capacity (MWe) and the number of DoD locations that can use them with a capacity factor near 100%. This partially explains why a medium-sized, 17-MWe microreactor could be a worthwhile investment for the DoD.

In order for a DoD investment in a 17-MWe microreactor to be worthwhile, the DoD must account for a cost of carbon and a value of energy resilience; the microreactor cost estimates cannot increase; and all 21 locations must be viable hosts — all so that manufacturing efficiencies decrease the microreactor costs with each unit.

Therefore, DoD decision-makers may want to first invest in more accurate cost estimates and perform a more targeted investigation of DoD locations to determine if the investment will be worthwhile.

Today, the DoD is developing a stationary and transportable microreactor , but this is not the first time the DoD invested in this technology. The Army Nuclear Power Program, or ANPP, designed, constructed and operated microreactors from 1954-1976 — when nuclear energy was in its infancy. ANPP demonstrated eight microreactors with different designs; three were stationary, three were portable (for transport and reassembly), and two were mobile (on a truck/barge). The program was ultimately discontinued because none of the reactors provided a unique operational capability — each could have been replaced with an alternative energy source — and because they were likely more expensive than those alternative energy sources.

An archival analysis suggests that the energy produced by ANPP microreactors was three to five times more expensive than if diesel generators produced the same amount of energy with a fully burdened cost of diesel fuel, which accounts for costs on top of the fuel itself, like transportation, protection, personnel, etc. These historical examples highlight how important costs are when considering an investment in a substitutable technology.

Ultimately, the decision to invest in a microreactor is complex; numerous assumptions and uncertainties could interact with each other to determine if the investment is worthwhile. Therefore, DoD decision-makers should use a systematic and repeatable decision framework to help manage these complexities; one possible framework can be found in my doctoral dissertation. The framework can equip DoD decision-makers to effectively communicate with each other about the decision to invest in a microreactor and can be reapplied in the future, as microreactor capabilities and DoD location requirements inevitably change.

U.S. Air Force 1st Lt. Kyle D. Haak has a doctorate in policy analysis from Pardee Rand Graduate School. The views expressed in this commentary do not necessarily represent the views of the think tank Rand, the U.S. Air Force, the U.S. Defense Department nor the U.S. government. For more details, watch a presentation online and read the dissertation on this topic.

目前尚不清楚国防部是否应该继续研发新型微型反应器——主要是因为它们的成本和监管存在不确定性。然而，我们可以利用一个系统化且可重复的框架，将此类信息及时纳入考量，从而为国防部做出有效的投资决策铺平道路。我们甚至可以利用现有数据和信息来确定初步结论。

例如，最小的微型反应堆的发电能力为 1-5 兆瓦，与美国国防部目前的能源成本相比，即使考虑到碳成本、能源弹性价值和制造效率，其价格也太高，几乎所有美国国防部所在地都难以承受。

另一方面，规模更大、更先进的核反应堆（80-300兆瓦）的平均电力成本较低，但产生的电力过多，几乎任何国防部场所都无法独立消耗。

介于这两种极端情况之间，中型微型反应堆（17 兆瓦）对于美国多达 21 个不同的国防部地点来说可能是一项值得的投资。

无论规模大小，微型反应堆都需要巨额的建设成本。美国国防部近期宣布了一项价值3亿美元的合同，用于设计、建造和测试微型反应堆原型。这一金额是核能研究所2019年发布的一份报告中估算的建设成本的4到20倍。虽然该合同涵盖的内容不仅限于建造，但成本的大幅增长与麻省理工学院的研究结果相符——核电站的建设成本估算往往会随着微型反应堆从概念阶段发展到原型阶段而增加。

与其仅仅比较建设成本，不如采用更有效的方法来比较不同的发电方式：计算其平准化电力成本，即整个生命周期内的平均电力成本。对于微型反应堆而言，这主要取决于瞬时发电量（功率容量，即兆瓦）、随时间推移的发电量占总发电量的百分比（容量系数）以及制造效率如何降低后续每个单元的成本。

如果微型反应器具有较大的功率容量（兆瓦），在其整个使用寿命期间持续使用（容量系数接近 100%），并且实施多个单元，则微型反应器更具成本效益。

上述初步研究结果侧重于在美国国防部设施内选址建设微型反应堆。这使得微型反应堆的发电容量（兆瓦）高于便携式或移动式反应堆。分析还要求国防部设施的平均电力需求大于微型反应堆的发电容量（兆瓦），以确保微型反应堆在其使用寿命内持续运行。这使得容量系数接近100%，并尽可能降低平均电力成本。

由于大多数国防部设施的平均电力需求相对较低，因此，功率容量（兆瓦）更大的微型反应堆与能够以接近100%的容量系数使用它们的国防部设施数量之间存在权衡。这在一定程度上解释了为什么一座中等规模的17兆瓦微型反应堆对国防部来说可能是一项值得的投资。

为了使美国国防部对 17 兆瓦微型反应堆的投资物有所值，国防部必须考虑碳成本和能源韧性的价值；微型反应堆的成本估算不能增加；所有 21 个地点都必须是可行的安置地点——所有这些都是为了提高制造效率，从而降低每个微型反应堆的成本。

因此，国防部决策者可能希望首先投入资金进行更准确的成本估算，并对国防部所在地进行更有针对性的调查，以确定这项投资是否值得。

如今，美国国防部正在研发一种固定式和可移动式微型反应堆，但这并非国防部首次投资这项技术。早在1954年至1976年间，陆军核动力计划（ANPP）就曾设计、建造并运行过微型反应堆——当时核能技术尚处于起步阶段。ANPP共展示了八座不同设计的微型反应堆：三座为固定式，三座为便携式（便于运输和重新组装），两座为移动式（安装在卡车/驳船上）。该计划最终终止，原因在于这些反应堆均不具备独特的运行能力——每座反应堆都可以被其他能源替代——而且它们的成本可能高于其他能源。

档案分析表明，ANPP微型反应堆产生的能源成本是柴油发电机产生相同能源成本的三到五倍，而柴油发电机产生的能源成本包含了柴油燃料的全部费用，例如运输、防护、人员等。这些历史案例凸显了在考虑投资可替代技术时，成本的重要性。

最终，投资微型反应器的决策十分复杂；众多假设和不确定因素相互作用，共同决定这项投资是否值得。因此，国防部决策者应采用系统化且可重复的决策框架来应对这些复杂性；我的博士论文中就提出了一种可行的框架。该框架能够帮助国防部决策者就微型反应器投资决策进行有效沟通，并且随着微型反应器性能和国防部选址需求的不断变化，未来还可以继续应用。

美国空军中尉凯尔·D·哈克拥有帕迪兰德研究生院政策分析博士学位。本文观点仅代表作者个人立场，并不一定代表兰德智库、美国空军、美国国防部或美国政府的观点。欲了解更多详情，请观看相关在线演示并阅读其博士论文。