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SMR safety issues

Nuclear Monitor Issue: 
Jim Green ‒ Nuclear Monitor editor

'Can we make a nuclear reactor that won't melt down?' That the opening question in a Forbes article written by self-styled energy expert James Conca. His answer: "Yes we can. It's called a small modular nuclear reactor (SMR) and NuScale Power is the company that will build the first one in America."1

Conca continued his January 2018 article:1

"Last year, they submitted to the U.S. Nuclear Regulatory Commission the first design certification application (DCA) for any SMR in the United States. Just two months later, NRC accepted their design certification application. By accepting the DCA for review, the NRC staff confirmed that NuScale's submission addresses all of NRC's initial concerns and requirements.

"Now, less than a year later, the NRC approved NuScale's walk-away-safe concept. That means just what it sounds like ‒ the reactor doesn't need the complex back-up power systems that traditional reactors require and which traditionally add a lot of cost as well as some uncertainty. This is a big deal. It means the reactor just won't melt down or otherwise cause any of the nightmares people think about when imagining the worse for nuclear power. It just shuts down and cools off. ...

"The small size and large surface area-to-volume ratio of NuScale's reactor core, that sits below ground in a super seismic-resistant heat sink, allows natural processes to cool it indefinitely in the case of complete power blackout. No humans or computers are needed to intervene, no AC or DC power, no pumps, and no additional water for cooling. ...

"This nuclear reactor is something that we've never seen before – a small modular reactor that is economic, factory built and shippable, flexible enough to desalinate seawater, refine oil, load-follow wind, produce hydrogen, modular to any size, and that provides something we've all been waiting for – a reactor that cannot meltdown."

Dr Ed Lyman from the Union of Concerned Scientists (UCS) provides a reality check:2

"As discussed in detail in my September 2013 report "Small Isn't Always Beautiful,"3 UCS has safety and security concerns about small modular reactors in general and about the NuScale design in particular. SMR vendors are pushing the Nuclear Regulatory Commission (NRC) to weaken its regulations regarding operator staffing, security staffing, and emergency planning, based on highly optimistic assertions that their reactors will be significantly safer than larger reactors.

"NuScale raises issues because of its fundamental design: up to 12 reactor modules packed together in a swimming-pool type structure. The Fukushima disaster has shown the world the complexity of trying to manage multiple nuclear reactor accidents when crisis strikes, and it is far from obvious that the NuScale concept addresses this issue adequately. UCS also does not have confidence that the NRC's licensing processes will give appropriate weight to multi-unit safety issues. Unfortunately, earlier this month the NRC staff concluded that safety concerns associated with "multiunit core damage events" did not warrant further evaluation in its "Generic Issues" program, which could have resulted in additional regulatory requirements.

"Many of the safety concerns described in the UCS report have now been validated by a Powerpoint presentation that was recently included, perhaps inadvertently, in the many thousands of pages of documents that the NRC has released under a Freedom of Information Act request for documents related to the Fukushima accident. The Powerpoint presentation, entitled "Center for Nuclear Waste Regulatory Analyses: Support to the U.S. Nuclear Regulatory Commission Office of New Reactors"4 (p. 479-529) and dated March 24, 2011, describes safety issues for SMRs such as

  • Potential fire and explosion hazards: below-grade facilities present unique challenges, such as smoke/fire behavior; life safety; design and operation of the HVAC system and removal of waste water.
  • Potential flooding hazards: below-grade reactors and subsystems raise concerns with regard to hurricane storm surges, tsunami run-up and water infiltration into structures.
  • Limited access for conducting inspections of pressure vessels and components that are crucial for containing radiation, such as welds, steam generators, bolted connections and valves.

"The document also spells out safety concerns particular to the NuScale design, observing that the reactors and spent fuel are stored in the same structure and depend on the same pool for cooling; that the bioshield covering the reactors or even the reactors themselves could be displaced in a flood; that the cooling pool could become contaminated with debris or other substances during a flood; and that operation under both normal and accident conditions depends highly on proper operation of valves around the pressure vessel.

"This document underscores the fact that SMRs are novel designs that raise new safety issues, and much analysis and testing will be required in order to verify the vendors' safety claims. There is therefore no basis at the present time for the NRC to grant SMRs any special exemptions to its regulatory requirements, and the Department of Energy should take steps to ensure that its Technical Licensing Support program does not use taxpayer funds to endanger public health by undermining nuclear safety and security standards."

PRISM propaganda

To give another example of disingenuous SMR safety hype, non-existent 'integral fast reactors' (IFR) are said to be meltdown-proof in addition to their other purported benefits. The best-known variant of the non-existent IFR is the non-existent Power Reactor Innovative Small Module (PRISM). Once again Ed Lyman provides a reality check in an article discussing the Pandora's Promise propaganda film:5

"In the IFR concept, which was never actually realized in practice, reactor-spent fuel would be reprocessed using a technology called pyroprocessing, and the extracted plutonium would be fabricated into new fuel. IFR advocates have long asserted that pyroprocessing is not a proliferation risk because the plutonium it separates is not completely purified.

"But a 2008 U.S. Department of Energy review ‒ which confirmed many previous studies ‒ concluded that pyroprocessing and similar technologies would "greatly reduce barriers to theft, misuse or further processing, even without separation of pure plutonium."

"Other Department of Energy studies showed that pyroprocessing, by generating large quantities of low-level nuclear waste and contaminated uranium, greatly increases the volume of nuclear waste requiring disposal, contradicting "Pandora's Promise's" claim it would reduce the amount of waste.

"And what about [Charles] Till's claim that the IFR can't melt down? It's false. "Pandora's Promise" referenced two successful safety tests conducted in 1986 at a small demonstration fast reactor in Idaho called the Experimental Breeder Reactor-II (EBR-II). But EBR-II operators scripted these tests to ensure the desired outcome, a luxury not available in the real world. Meanwhile, the EBR-II's predecessor, the EBR-I, had a partial fuel meltdown in 1955, and a similar reactor, Fermi 1 near Detroit, had a partial fuel meltdown in 1966.

"Moreover, fast reactors have inherent instabilities that make them far more dangerous than light-water reactors under certain accident conditions, conditions that were studiously avoided in the 1986 dog-and-pony show at EBR-II.

"Perhaps the biggest myth in the film is the notion that all U.S. research on fast reactors was terminated. In fact, the IFR program's demise was a shutdown in name only. The Department of Energy has continued to fund research and development on fast reactor technology to the tune of tens of millions to hundreds of millions of dollars a year. The IFR Fuel Reprocessing Facility in Idaho shown in the film ‒ in reality, a plant called the Fuel Conditioning Facility ‒ has been operating for decades, essentially as a jobs program, to reprocess spent fuel from the now-defunct EBR-II, despite the system's serious problems. In 2000, the Department of Energy promised that all the fuel would be processed by around 2007. Three years later, it delayed the projected completion date to 2030.

"Till's assertion in "Pandora's Promise" that "we know how to do these things" does not square with the difficulties the Department of Energy has encountered in trying to operate this troubled plant."

The one true meltdown-proof SMR

First prize for SMR safety idiocy and dishonesty goes to molten salt reactor (MSR) enthusiasts who claim that MSRs are meltdown-proof. MSRs are in fact meltdown-proof, twice over. First, fuel meltdown in MSRs is impossible because MSRs don't exist. Secondly, if MSRs did exist, the fuel couldn't possibly melt because it is liquid.

As with solid-fueled reactors, dispersal of radionuclides via fire or chemical explosion is possible … but fuel melting is not. That's not an advantage of MSRs ‒ it could be a liability.

The UK National Nuclear Laboratory noted in a 2016 report that constructing a safety case for MSRs will necessarily be very different compared to a conventional reactor:6

"This is dictated by the fact that in an MSR the normal operating condition is with the fuel melted and therefore some of the barriers to release of fission products, actinides and activation products in a solid fuel reactor no longer apply. Although MSR designs are typically characterised by strong negative temperature feedback coefficients, un-pressurised systems, tolerance of high temperatures and passive decay heat removal, these features per se may not necessarily make the safety case easy to demonstrate. There will need to be extensive experimental test data available that will substantiate all aspects of the safety case. At present this database does not exist …"


1. James Conca, 24 Jan 2018, 'Can We Make A Nuclear Reactor That Won't Melt Down?',

2. Ed Lyman, 17 Dec 2013, 'Safety and Security Concerns about Small Modular Reactors: NuScale's Design',

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

4. Southwest Research Institute, 'Center for Nuclear Waste Regulatory Analyses: Support to the U.S. Nuclear Regulatory Commission Office of New Reactors',

5. Edwin Lyman, 7 Nov 2013, 'Scientist: Film hypes the promise of advanced nuclear technology',

6. National Nuclear Laboratory, 15 March 2016, 'SMR Techno-Economic Assessment, Project 3: SMRs Emerging Technology, Assessment of Emerging SMR Technologies, Summary Report For The Department of Energy and Climate Change',