You are here

Small Modular Reactors: no solution for costs, safety and waste problems

Nuclear Monitor Issue: 

The same industry that promised that nuclear power would be "too cheap to meter" is now touting another supposed cure-all for America's power needs:  the small modular reactor (SMR).  The small modular reactor is being pitched by the nuclear power industry as a sort of production-line auto alternative to hand-crafted sports car, with supposed cost savings from the "mass manufacturing" of modestly sized reactors that could be scattered across the United States on a relatively quick basis. The facts about SMRs are far less rosy. 

Proponents of nuclear power are advocating for the development of small modular reactors (SMRs) as the solution to the problems facing large reactors, particularly soaring costs, safety, and radioactive waste.  “Small modular reactors” are defined by the US Department of Energy (DOE) as reactors that would produce 300MWe or less and are made in modules that can be transported. Unfortunately, small-scale reactors can’t solve these problems, and would likely exacerbate them.

There has been a proliferation of proposed Small Modular Reactor designs, but none have applied for certification by the Nuclear Regulatory Com­mission (NRC) yet. The NRC says that it expects to receive its first SMR design certification appli­cation in 2012. The factsheet addresses SMR designs for which the NRC may receive design certification applications in FY2011. It does not include some designs that are being researched but that are not on the NRC list, notably the travelling wave reactor. IEER will produce a separate report later in 2010 on this reactor.

Inherently more expensive?
SMR proponents claim that small size will en­able mass manufacture in a factory, enabling considerable savings relative to field construc­tion and assembly that is typical of large reac­tors. In other words, modular reactors will be cheaper because they will be more like as­sembly line cars than hand-made Lamborghi­nis.

In the case of reactors, however, several offsetting factors will tend to neutralize this advantage and make the costs per kilowatt of small reactors higher than large reactors. First, in contrast to cars or smart phones or similar widgets, the materials cost per kilowatt of a reactor goes up as the size goes down. This is because the surface area per kilowatt of capacity, which dominates materi­als cost, goes up as reactor size is decreased. Similarly, the cost per kilowatt of secondary containment, as well as independent systems for control, instrumentation, and emergency management, increases as size decreases. Cost per kilowatt also increases if each reac­tor has dedicated and independent systems for control, instrumentation, and emergency management. For these reasons, the nuclear industry has been building larger and larger reactors in an effort to try to achieve economies of scale and make nuclear power economically competitive.

Proponents argue that because these nuclear projects would consist of several smaller reactor modules instead of one large reactor, the construction time will be shorter and therefore costs will be reduced. How­ever, this argument fails to take into account the implications of installing many reactor modules in a phased manner at one site, which is the proposed approach at least for the United States. In this case, a large contain­ment structure with a single control room would be built at the beginning of the project that could accommodate all the planned capacity at the site. The result would be that the first few units would be saddled with very high costs, while the later units would be less expensive.

The realization of economies of scale would depend on the construction period of the entire project, possibly over an even longer time span than present large-reactor projects. If the later-planned units are not built, for instance due to slower growth than anticipated, the earlier units would likely be more expensive than present reactors, just from the diseconomies of the containment, site preparation, instrumentation and control system expenditures. Alternatively, a contain­ment structure and instrumentation and control could be built for each reactor. This would greatly increase unit costs and per kilo­watt capital costs. Some designs (such as the PBMR) propose no secondary containment, but this would increase safety risks.

These cost increases are unlikely to be offset even if the entire reactor is manufac­tured at a central facility and some economies are achieved by mass manufacturing com­pared to large reactors assembled on site.

Furthermore, estimates of low prices must be regarded with skepticism due to the history of past cost escalations for nuclear reactors and the potential for cost increases due to require­ments arising in the process of NRC certifica­tion. Some SMR designers are proposing that no prototype be built and that the necessary licensing tests be simulated. Whatever the process, it will have to be rigorous to ensure safety, especially given the history of some of proposed designs.

The cost picture for sodium-cooled reac­tors is also rather grim. They have typically been much more expensive to build than light water reactors, which are currently estimated to cost between $6,000 and $10,000 per kilowatt in the US. The costs of the last three large breeder reactors have varied wild­ly.

In 2008 dollars, the cost of the Japanese Monju reactor (the most recent) was $27,600 per kilowatt (electrical); French Superphénix (start up in 1985) was $6,300; and the Fast Flux Test Facility (startup in 1980) at Hanford was $13,800. This gives an average cost per kilowatt in 2008 dollars of about $16,000, without taking into account the fact that cost escalation for nuclear reactors has been much faster than inflation. In other words, while there is no recent US experience with construction of sodium-cooled reactors, one can infer that (i) they are likely to be far more expensive than light water reactors, (ii) the financial risk of building them will be much greater than with light water reactors due to high variation in cost from one project to another and the high variation in capacity fac­tors that might be expected.

Even at the lower end of the capital costs, for Superphénix, the cost of power generation was extremely high — well over a dollar per kWh since it operated so little. Monju, despite being the most expensive has generated essentially no electricity since it was commissioned in 1994. There is no comparable experience with potassium-cooled reactors, but the chemi­cal and physical properties of potassium are similar to sodium.

Increased safety and proliferation problems
Mass manufacturing raises a host of new safety, quality, and licensing concerns that the NRC has yet to address. For instance, the NRC may have to devise and test new licensing and inspection procedures for the manufacturing facilities, including inspec­tions of welds and the like. There may have to be a process for recalls in case of major de­fects in mass-manufactured reactors, as there is with other mass-manufactured products from cars to hamburger meat. It is unclear how recalls would work, especially if transpor­tation offsite and prolonged work at a repair facility were required.

Some vendors, such as PBMR (Pty) Ltd. and Toshiba, are proposing to manufacture the reactors in foreign countries. In order to reduce costs, it is likely that manufacturing will move to countries with cheaper labor forces, such as China, where severe quality problems have arisen in many products from drywall to infant formula to rabies vaccine.


Despite 50 years of research by many countries, including the United States, the the­oretical promise of the PBMR has not come to fruition. The technical problems encountered early on have yet to be resolved, or apparent­ly, even fully understood. PMBR proponents in the US have long pointed to the South African program as a model for the US. Ironically, the US Department of Energy is once again pursuing this design at the very moment that the South African government has pulled the plug on the program due to escalating costs and problems.

Other issues that will affect safety are NRC requirements for operating and security personnel, which have yet to be determined. To reduce operating costs, some SMR vendors are advocating lowering the number of staff in the control room so that one operator would be responsible for three modules. In addition, the SMR designers and potential op­erators are proposing to reduce the number of security staff, as well as the area that must be protected. NRC staff is looking to design­ers to incorporate security into the SMR de­signs, but this has yet to be done. Ultimately, reducing staff raises serious questions about whether there would be sufficient personnel to respond adequately to an accident.

Of the various types of proposed SMRs, liq­uid metal fast reactor designs pose particular safety concerns. Sodium leaks and fires have been a central problem — sodium explodes on contact with water and burns on contact with air. Sodium-potassium coolant, while it has the advantage of a lower melting point than sodium, presents even greater safety issues, because it is even more flammable than molten sodium alone. Sodium-cooled fast reactors have shown essentially no posi­tive learning curve (i.e., experience has not made them more reliable, safer, or cheaper).

The world’s first nuclear reactor to generate electricity, the EBR I in Idaho, was a sodium-potassium-cooled reactor that suffered a partial meltdown. EBR II, which was sodium-cooled reactor, operated reasonably well, but the first US commercial prototype, Fermi I in Michigan had a meltdown of two fuel assem­blies and, after four years of repair, a sodium explosion. The most recent commercial prototype, Monju in Japan, had a sodium fire 18 months after its commissioning in 1994, which resulted in it being shut down for over 14 years. The French Superphénix, the largest sodium-cooled reactor ever built, was designed to demonstrate commercialization. Instead, it operated at an average of less than 7 percent capacity factor over 14 years before being permanently shut.

In addition, the use of plutonium fuel or uranium enriched to levels as high as 20 percent — four to five times the typical enrichment level for present commercial light water reactors — presents serious proliferation risks, especially as some SMRs are proposed to be exported to developing countries with small grids and/or installed in remote locations. Security and safety will be more difficult to maintain in coun­tries with no or underdeveloped nuclear regulatory infrastructure and in isolated areas. Burying the reactor underground, as proposed for some designs, would not sufficiently address security because some access from above will still be needed and it could increase the environmental impact to groundwater, for example, in the event of an accident.

More complex waste problem
Proponents claim that with longer opera­tion on a single fuel charge and with less production of spent fuel per reactor, waste management would be simpler. In fact, spent fuel management for SMRs would be more complex, and therefore more expensive, because the waste would be located in many more sites. The infrastructure that we have for spent fuel management is geared toward light-water reactors at a limited number of sites. In some proposals, the reactor would be buried underground, making waste retrieval even more complicated and com­plicating retrieval of radioactive materials in the event of an accident. For instance, it is highly unlikely that a reactor contain­ing metallic sodium could be disposed of as a single entity, given the high reactivity of sodium with both air and water. Decom­missioning a sealed sodium- or potassium-cooled reactor could present far greater technical challenges and costs per kilowatt of capacity than faced by present-day above-ground reactors.

Not a climate solution
Efficiency and most renewable technologies are already cheaper than new large reactors. The long time — a decade or more — that it will take to certify SMRs will do little or noth­ing to help with the global warming problem and will actually complicate current efforts underway. For example, the current sched­ule for commercializing the above-ground sodium cooled reactor in Japan extends to 2050, making it irrelevant to addressing the climate problem. Relying on assurances that SMRs will be cheap is contrary to the experi­ence about economies of scale and is likely to waste time and money, while creating new safety and proliferation risks, as well as new waste disposal problems.

(This is a shortened version of the factsheet on Small Modular Reactors produced by Arjun Makhijani and Michelle Boyd for the Institute for Energy and Environmental Research (IEER) and Physicians for Social Responsibility (PSR), September 2010. It is available at:

Contact: Leslie Anderson, +1 703 276-3256

Institute for Energy and Environmental ResearchPSR