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Small modular reactors and nuclear weapons proliferation

Nuclear Monitor Issue: 
Jim Green ‒ Nuclear Monitor editor

Power/weapons connections

First, a refresher on the broad patterns of intersection between (ostensibly) peaceful nuclear programs and weapons proliferation … the world into which an SMR industry might be born. These were neatly summarized last year by Michael Shellenberger from the Environmental Progress pro-nuclear lobby group.1-3 Shellenberger is notorious for peddling misinformation4 and his promotion of nuclear weapons proliferation is stupid and dangerous5-6, but his analysis of the civil/military proliferation problem is sound (and his critique of Generation IV nuclear hype is perceptive7).

Patterns connecting the pursuit of power and weapons stretch back across the 60 years of civilian nuclear power. Shellenberger noted that "at least 20 nations sought nuclear power at least in part to give themselves the option of creating a nuclear weapon".1

"[N]ational security, having a weapons option, is often the most important factor in a state pursuing peaceful nuclear energy", Shellenberger wrote.3 An analysis by Environmental Progress found that of the 26 nations that are building or are committed to build nuclear power plants, 23 have nuclear weapons, had weapons, or have shown interest in acquiring weapons.8 "While those 23 nations clearly have motives other than national security for pursuing nuclear energy," Shellenberger wrote, "gaining weapons latency appears to be the difference-maker."1

Shellenberger pointed to research by Fuhrmann and Tkach which found that 31 nations had the capacity to enrich uranium or reprocess plutonium, and that 71% of them created that capacity to give themselves weapons latency.9

The military origins of SMR programs

Kennedy Maize wrote in POWER magazine in 2015:10

"Small reactors are familiar to the nuclear industry, which began with small machines that bulked up over the years to take advantage of economies of scale. The legendary Shippingport nuclear plant in western Pennsylvania, the first fully commercial pressurized-water nuclear plant, entered service in 1957 and was rated at 60 MW. The U.S. military and the Soviet Union spent considerable sums in the 1950s and 1960s on designs for small, transportable, remote reactors and for reactors to be used in ship propulsion.

"Many of today's SMR plans have their roots in naval reactor technology, as did Shippingport. Its technology was based on Westinghouse reactors that powered the first U.S. nuclear submarines. Argentina's CAREM 25 reactor design came from the Argentine navy. The country unveiled the design at a 1984 IAEA conference. The project then got shelved, but was revived in 2006 as Argentina moved to revitalize its nuclear power program in the face of limited supplies and high prices for imported natural gas. Argentina has few easily accessible indigenous energy resources.

"Russia's floating nukes also rely on maritime technology, reactors developed for its successful fleet of nuclear icebreakers, dating back well into the days of the Soviet Union. The nation's first nuclear icebreaker, the NS Lenin, was launched in 1957, the same year that Shippingport went into commercial service.

"In the U.S., two of the major SMR industrial developers, Babcock & Wilcox and Westinghouse, both have extensive experience with naval reactors."

Small reactors and proliferation

Small power reactors have been used to produce fissile material for weapons. Examples include:

  • Magnox reactors in the UK which were used to generate power and to produce plutonium for weapons.11
  • North Korea has tested weapons using plutonium produced in its 'Experimental Power Reactor' ‒ a Magnox clone.12
  • India refuses to place numerous power reactors (including some of its small PHWR reactors) under safeguards13 and presumably uses (or plans to use) them for weapons production.

Based on historical experience, there's every reason to be concerned about the weapons proliferation risks associated with a proliferation of SMRs. It can be anticipated that countries with an interest in developing weapons ‒ or a latent weapons capability ‒ will be more interested in acquiring SMRs than countries with no such interest ("nations that lack a need for weapons latency often decide not to build nuclear power plants", Shellenberger states1).

Saudi Arabia's interest in acquiring a South Korean-designed SMART SMR may be a topical case study, and South Korea may have found a model to unlock the potential of SMRs: collaboration with a repressive Middle Eastern state that has a clear interest in developing a nuclear weapons capability, with extensive technology transfer thrown in.15

A subsidiary of Holtec International has actively sought a military role, inviting the National Nuclear Security Administration to consider the feasibility of using a proposed SMR to produce tritium, used to boost the explosive yield of the US nuclear weapons arsenal.16

NuScale Power, on the other hand, claims to be taking the high moral ground. NuScale's chief commercial officer said in 2013 that the company is not in business to sell reactors to politically unstable countries.17 Yet in early 2019, NuScale participated in a White House meeting which discussed, among other issues, the possibility of selling nuclear power technology to Saudi Arabia ‒ a known nuclear weapons wannabe in a volatile region.18

The CAREM SMR under construction in Argentina was originally a Navy project with the aim of building nuclear-powered submarines and ships.19,20 Those ambitions resurfaced in 2010. The World Nuclear Association reported: "The Ministry of Defence in Argentina has said it is reviewing the idea of using nuclear reactors to power some of its naval vessels. … One potential supplier of reactors to meet these kinds of requirements would be the nuclear technology firm Invap, which has exported several research reactors and developed the Carem power plant design."21

SMRs as the proliferator's technology of choice

Power reactors (and associated infrastructure) have been used in support of weapons programs22, as have research reactors.23 There is a long-running debate about whether (large) power reactors or research reactors are the proliferators' technology of choice.24-26 Research reactors are relatively cheap (typically several hundred million dollars) but the plutonium production rate is typically low. Power reactors are expensive but produce large amounts of plutonium (and can be run on a shortened irradiation cycle to produce large amounts of weapons-grade plutonium).

SMRs could become the technology of choice for proliferators: reactors that produce significant amounts of plutonium each year without the expense of a gigawatt-scale nuclear power program. In the early 1990s, the director of the Turkish Atomic Energy Authority said Argentina's 25-MW CAREM SMR design "was too small for electricity generation and too big for research or training, however, very suitable for plutonium production".27

The proliferation risks associated with different SMR designs

The IAEA estimates there are around 50 SMR designs. Since they are paper designs, let's assume there are, say, five possible configurations of each design (fast vs. thermal neutrons, different fuels, closed vs. open fuel cycles, etc.) Now let's run through those 250 configurations and consider the proliferation risks associated with each. Or, on second thoughts, let's not. Suffice it to make a few general points.

By far the most important point to make is that any configuration of any SMR design will pose proliferation risks. As the UK Royal Society notes: "There is no proliferation proof nuclear fuel cycle. The dual use risk of nuclear materials and technology and in civil and military applications cannot be eliminated."28

Ramana and Mian state in a 2014 article:29

"Proliferation risk … depends on both technical and non-technical factors. While the non-technical factors are largely not dependent on choice of reactor type, SMRs and their intrinsic features do affect the technical component of proliferation risk. In the case of both iPWRs [integral Pressurized Water Reactors] and fast reactors, the proliferation risk is enhanced relative to current generation light water reactors primarily because greater quantities of plutonium are produced per unit of electricity generated. In the case of HTRs [high temperature gas-cooled reactors], proliferation risk is increased because of the use of fuel with higher levels of uranium enrichment, but is diminished because the spent fuel is in a form that is difficult to reprocess."

Glaser, Hopkins and Ramana compare the proliferation risks of standard light-water reactors, proposed integral pressurized water SMRs (iPWRs) and proposed SMRs with long-lived cores (LLCs) that would not require refueling for two or more decades (typically fast-spectrum designs cooled by helium, sodium, or other liquid metals such as lead and lead-bismuth eutectics).30

The authors state:30

"iPWRs are likely to have higher requirements for uranium ore and enrichment services compared to gigawatt-scale reactors. This is because of the lower burnup of fuel in iPWRs, which is difficult to avoid because of smaller core size and all-in-all-out core management. These characteristics also translate into an increased proliferation risk unless they are offset by technical innovations in reactor and safeguards design and institutional innovations in the nuclear fuel cycle.

"Uranium and uranium enrichment requirements are reduced for fast-spectrum SMRs with LLCs, but in this case strong incentives for spent-fuel reprocessing are likely to result from the high fissile content of the spent fuel. This same characteristic also increases the probability of proliferation success in a diversion scenario …"

A report by the UK Parliamentary Office of Science & Technology offers these generalizations:31

"There is uncertainty over the extent to which widespread SMR use might increase or decrease non-proliferation risk. Some SMRs require less frequent refuelling than conventional nuclear, reducing high risk periods. However, more integrated designs may be more challenging to inspect, and some designs use more highly enriched uranium than conventional nuclear. Both of these aspects could increase proliferation risk."

Uranium enrichment

Ramana and Mian note that attempts to reduce one proliferation risk can worsen another:29

"Proliferation resistance is another characteristic that imposes sometimes contradictory requirements. One way to lower the risk of diversion of fuel from nuclear reactors is to minimize the frequency of refueling because these are the periods when the fuel is out of the reactor and most vulnerable to diversion, and so many SMR designers seek longer periods between refueling. However, in order for the reactor to maintain reactivity for the longer period between refuelings, it would require starting with fresh fuel with higher uranium enrichment or mixing in plutonium.

"Some designs even call for going to an enrichment level beyond 20 percent uranium-235, the threshold used by the International Atomic Energy for classifying material as being of "direct use" for making a weapon. All else being equal, the use of fuel with higher levels of uranium enrichment or plutonium would be a greater proliferation risk, and is the reason why so much international attention has been given to highly enriched uranium fueled research reactors and converting them to low enriched uranium fuel or shutting them down.

"Moreover, an SMR design relying on highly enriched uranium fuel creates new proliferation risks – the need for production of fresh highly enriched uranium and the possibility of diversion at the enrichment plant and during transport. Any reduction of proliferation risk at the reactor site by reducing refueling frequency, it turns out, may be accompanied by an increase in the proliferation risk elsewhere."

In January 2019, the US government allocated US$115 million to kick-start a domestic uranium enrichment project in Piketown, Ohio.32 The HALEU Demonstration Program will aim to produce 19.75%-enriched 'high assay low enriched uranium' (HALEU) using US-designed and operated centrifuge technology.33 The project is being sold as a step towards domestic production of enriched uranium for 'advanced reactors' (including SMRs) but there is also a military agenda. Republican Senator Rob Portman said: "Getting Piketon back to its full potential benefits the skilled workforce here, the surrounding local economy, and strengthens national energy and defense security."32 The Department of Energy said that Centrus subsidiary American Centrifuge Operating was the only firm that qualified for the project, noting that the company is US-owned and controlled, a requirement for enrichment contracts to supply the military.32

Nationalistic military hawks have been lobbying furiously (and evidently successfully) to re-establish domestic uranium enrichment in the US to accommodate the Navy's long-term 'need' for additional highly enriched uranium to fuel its reactors for long intervals between refueling, and the 'need' for a domestic source of low enriched uranium to fuel reactors used to produce tritium for weapons.34

It might be the case that very few if any SMRs are ever built in the US, yet the promise of an SMR industry is already providing cover for military projects.

Plutonium reactors

The US Department of Energy is working on a plan to establish a 'versatile test reactor' as a source of high-energy neutrons to help researchers develop fuels and materials for fast reactors, including SMRs.35 The Department plans to make a decision in 2020 as to whether to proceed with the project.

Edwin Lyman from the Union of Concerned Scientists wrote: "What may not be clear from the name is that this facility itself would be an experimental fast reactor, likely fueled with weapon-usable plutonium. Compared to conventional light-water reactors, fast reactors are less safe, more expensive, and more difficult to operate and repair. But the biggest problem with this technology is that it typically requires the use of such weapon-usable fuels as plutonium, increasing the risk of nuclear terrorism."36

Safeguards and security

Some claim that up to 85 GW of SMR capacity could be installed by 2035, comprising perhaps 1,000 small reactors. How would the IAEA safeguards system cope with the additional workload? The IAEA safeguards system has been chronically underfunded37 and it is implausible that any increased funding made available to the IAEA to safeguard an SMR industry would be commensurate with the increased workload. On the other hand, it is entirely plausible than an SMR industry will fail to materialize and that the safeguards system will therefore not face additional stresses.

The Union of Concerned Scientists discussed SMR security issues in a 2013 paper.38 Some key excerpts are reproduced here but the paper is worth reading in its entirety:

"Fukushima Daiichi demonstrated how rapidly a nuclear reactor accident can progress to a core meltdown if multiple safety systems are disabled. A well-planned and -executed terrorist attack could cause damage comparable to or even worse than the earthquake and tsunami that initiated the Fukushima crisis, potentially in even less time. For these reasons, the NRC requires nuclear plant owners to implement robust security programs to protect their plants against sabotage.

"Despite these concerns, SMR proponents argue for reducing security requirements ‒ in particular, security staffing ‒ to reduce the cost of electricity produced by small modular reactors. In 2011, Christofer Mowry, president of Babcock & Wilcox mPower, Inc., said, "Whether SMRs get deployed in large numbers or not is going to come down to O&M [operations and maintenance]. And the biggest variable that we can attack directly, the single biggest one, is the security issue".

"His position was echoed by the NEI [Nuclear Energy Institute], which submitted a position paper to the NRC in July 2012 on the issue of physical security for SMRs. It clearly laid out the industry view: "The regulatory issue of primary importance related to physical security of SMRs is security staffing. The issue has the potential to adversely affect the viability of SMR development in the U.S. Security staffing directly impacts annual operations and maintenance (O&M) costs and as such constitutes a significant financial burden over the life of the facility. … For this reason, evaluation of security staffing requirements for SMRs has become a key focal point." …

"The NRC staff appears to be open to suggestions for alternative measures that take into account design features of SMRs that may make them less vulnerable to attack. The primary feature that mPower and other SMR vendors appear to credit in seeking relief from security regulations is underground siting. Underground siting would enhance protection against some attack scenarios, but not all. A direct jet impact on the reactor containment is less likely for an underground reactor, but the ensuing explosions and fire could cause a crisis. Certain systems, such as steam turbines, condensers, electrical switchyards, and cooling towers, will need to remain aboveground, where they will be vulnerable. Plants will require adequate access and egress for both routine and emergency personnel. Ventilation shafts and portals for equipment access also provide potential means of entry for intruders. In addition, if SMR sites have smaller footprints, as vendors are claiming, the site boundary will be closer to the reactor, and thus there will be less warning time in the event of an intrusion and potentially insufficient spatial separation of redundant and diverse safety systems.

"In short, knowledgeable and determined adversaries will likely be able to develop attack scenarios that could circumvent measures such as underground siting. In situations such as hostage scenarios, terrorists may even be able to utilize the additional defense afforded by an underground site against off-site police and emergency response. Thus, a robust and flexible operational security response will be required no matter what intrinsic safeguards are added to reactor design."


1. Michael Shellenberger, 29 Aug 2018, 'For Nations Seeking Nuclear Energy, The Option To Build A Weapon Remains A Feature Not A Bug',

2. Michael Shellenberger, 6 Aug 2018, 'Who Are We To Deny Weak Nations The Nuclear Weapons They Need For Self-Defense?',

3. Michael Shellenberger, 28 Aug 2018, 'How Nations Go Nuclear: An Interview With M.I.T.'s Vipin Narang',

4. Nuclear Monitor #852, 30 Oct 2017, 'Exposing the misinformation of Michael Shellenberger and 'Environmental Progress'',

5. Nuclear Monitor #865, 6 Sept 2018, 'Nuclear lobbyist Michael Shellenberger learns to love the bomb, goes down a rabbit hole',

6. Nuclear Monitor #865, 6 Sept 2018, ''Almost Trumpian in its incoherence': Critical responses to Michael Shellenberger's promotion of nuclear weapons proliferation',

7. Michael Shellenberger, 18 July 2018, 'If Radical Innovation Makes Nuclear Power Expensive, Why Do We Think It Will Make Nuclear Cheap?',

8. Environmental Progress, 2018, Nations Building Nuclear ‒ Proliferation Analysis,

9. Matthew Fuhrmann and Benjamin Tkach, 8 Jan 2015, 'Almost nuclear: Introducing the Nuclear Latency dataset', Conflict Management and Peace Science,

10. Kennedy Maize, 1 May 2015, 'Small Modular Reactors Speaking in Foreign Tongues',

11. 'Magnox', accessed 26 Feb 2019,

12. Yongbyon Nuclear Scientific Research Center, accessed 26 February 2019,

13. John Carlson, 15 April 2015, submission to Joint Standing Committee on Treaties, Parliament of Australia,

14. Michael Shellenberger, 29 Aug 2018, 'For Nations Seeking Nuclear Energy, The Option To Build A Weapon Remains A Feature Not A Bug',

15. Nuclear Monitor #800, 19 March 2015, 'Small modular reactors: a chicken-and-egg situation',

16. Thomas Clements, 2012, 'Documents Reveal Time-line and Plans for "Small Modular Reactors" (SMRs) at the Savannah River Site (SRS) Unrealistic and Promise no Funding',

17. Bennett Hall, 9 Aug 2013, 'NuScale refutes SMR critics', Corvallis Gazette-Times,

18. World Nuclear Association, 14 Feb 2019, 'US nuclear industry seeks presidential support',



21. World Nuclear Association, 8 June 2010, 'Nuclear propulsion an option for Argentina',

22. See section 7 in: Nuclear Monitor #804, 28 May 2015, 'The myth of the peaceful atom',

23. Friends of the Earth Australia, 'Research reactors and weapons proliferation',

24. John Holdren, 1983, "Nuclear power and nuclear weapons: the connection is dangerous", Bulletin of Atomic Scientists, January, pp.40-45, or

25. Anthony Fainberg, 1983, "The connection is dangerous", Bulletin of the Atomic Scientists, May, p.60,

26. John Holdren, 1983, "Response to Anthony Fainberg, 1983, 'The connection is dangerous'", Bulletin of the Atomic Scientists, May, pp.61-62.

27. Mustafa Kibaroglu, Spring-Summer 1997, 'Turkey's quest for peaceful nuclear power', The Nonproliferation Review,

28. Royal Society, Oct 2011, 'Fuel Cycle Stewardship in a Nuclear Renaissance',

29. M.V. Ramana and Zia Mian, 4 Sept 2014, 'Too much to ask: why small modular reactors may not be able to solve the problems confronting nuclear power', Nuclear Monitor #790,

30. Alexander Glaser, Laura Berzak Hopkins and M. V. Ramana, March 2017, 'Resource Requirements and Proliferation Risks Associated with Small Modular Reactors', Nuclear Technology, Vol.184, Issue 1,

31. UK Houses of Parliament, Parliamentary Office of Science & Technology, July 2018, 'Small Modular Nuclear Reactors', No. 580,

32. James Osborne, 25 Jan 2019, '$115 million nuclear contract draws scrutiny on Perry', Houston Chronicle,

33. Neil Ford, 27 Feb 2019, 'DOE funding propels US towards first advanced fuel factory by 2023',

34. Nuclear Monitor #850, 'Nuclear power, weapons and 'national security'', 7 Sept 2017,

35. World Nuclear Association, 15 November 2018, 'PRISM selected for US test reactor programme',

36. Ed Lyman, 15 Feb 2018, 'The "Versatile Fast Neutron Source": A Misguided Nuclear Reactor Project',

37. John Carlson, Nov 2018, 'Future Directions in IAEA Safeguards',

38. Edwin Lyman, Sept 2013, 'Small Isn't Always Beautiful: Safety, Security, and Cost Concerns about Small Modular Reactors',