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Integral fast reactors: fact and fiction

Nuclear Monitor Issue: 
Jim Green ‒ Nuclear Monitor editor

Integral fast reactors (IFR) would, if they existed, share features of other fast neutron reactors along with some less common or distinctive features including metallic fuel and the coupling of the reactor to pyroprocessing (discussed below). The fuel would sit in a pool of liquid metal sodium coolant, at atmospheric pressure.

IFR's have been the subject of endless hype but as Ed Lyman from the Union of Concerned Scientists notes, the interest of these "staunch advocates … has been driven largely by idealized studies on paper and not by facts derived from actual experience."1

Actual experience has been limited to the EBR-II prototype that operated at Argonne National Laboratory from the 1960s to 1994. Since then, progress has been glacial (see the article in this issue of Nuclear Monitor: 'Whatever happened to the 'integral fast reactor'').

For the most part, the claims of IFR advocates don't stand up to scrutiny.


IFR advocates claim that:

  • "Metal fuel expands if it overheats, shutting off the fission reaction and making a meltdown physically implausible."2
  • "[E]ven a catastrophic situation will not result in a reactor meltdown".3
  • GE Hitachi claims that: "In the event of a worst-case-scenario accident, the metallic core expands as the temperature rises, and its density decreases slowing the fission reaction. The reactor simply shuts itself down. PRISM's very conductive metal fuel and metal coolant then readily dissipates excess heat … without damaging any of its components. This is what is described as "passive safety" a design feature that relies upon the laws of physics, instead of human, electronic or mechanical intervention, to mitigate the risk of an accident."4

In fact, IFR/PRISM reactors would be subject to some of the same risks as other fast-reactor types5 and other risks associated with pyroprocessing.

According to Argonne National Laboratory: "[T]he metal fuel technology base was developed at Argonne in the 1980s and 1990s; its inherent safety potential was demonstrated in the landmark tests conducted on the Experimental Breeder Reactor-II (EBR-II) in April 1986. They demonstrated the safe shutdown and cooling of the reactor without operator action following a simulated loss-of-cooling accident."6

But the 1986 test was a "dog-and-pony show" according to Ed Lyman:7

"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."

Nuclear weapons proliferation

Climate scientist James Hansen claims that IFR technology "could be inherently free from the risk of proliferation"8 and another IFR proponent, Barry Brook, claims they "cannot be used to generate weapons-grade material."9

In fact, IFRs could be used to produce plutonium for weapons. Dr George Stanford, who worked on the IFR (EBR-II) R&D program in the US, notes that proliferators "could do [with IFRs] what they could do with any other reactor − operate it on a special cycle to produce good quality weapons material."10 And IFR advocate Tom Blees notes that: "IFRs are certainly not the panacea that removes all threat of proliferation, and extracting plutonium from it would require the same sort of techniques as extracting it from spent fuel from light water reactors."11

IFR proponents claim they could help solve proliferation problems by using fissile material (especially plutonium) as reactor fuel. But they could also worsen proliferation problems. To quote from an Argonne National Laboratory report: "The reactor ... could be used for excess plutonium consumption or as a breeder if needed ..."12

IFR proponents claim that pyroprocessing does not pose a proliferation risk because the plutonium it separates is mixed with other (non-fissile) actinides. But a 2008 US Department of Energy review concluded that pyroprocessing and similar technologies would "greatly reduce barriers to theft, misuse or further processing, even without separation of pure plutonium."7

IFR advocates Barry Brook and Corey Bradshaw claim that nuclear weapons proliferation "is under strong international oversight."8 Oddly, they cite another IFR advocate, Tom Blees, in support of that statement. But Blees doesn't argue that the nuclear industry is subject to strong international oversight − he argues that "fissile material should all be subject to rigorous international oversight" (emphasis added).14

Blees argues for the establishment of an international strike force on full standby to attend promptly to any detected attempts to misuse or to divert nuclear materials.15 That is a far cry from the IAEA's safeguards system as it currently exists. In articles and speeches during his tenure as the Director General of the IAEA from 1997−2009, Dr. Mohamed ElBaradei said that the Agency's basic rights of inspection are "fairly limited", that the safeguards system suffers from "vulnerabilities" and "clearly needs reinforcement", that efforts to improve the system have been "half-hearted", and that the safeguards system operates on a "shoestring budget ... comparable to that of a local police department".

IFR proponents indulge in disingenuous comparisons. For example, it's fair to say that pyroprocessing poses less of a proliferation risk compared to conventional PUREX reprocessing … but it poses a greater proliferation risk compared to a once-through, no-reprocessing fuel cycle.


GE Hitachi refuses to release estimates of capital and operating costs for its IFR design (which it calls PRISM), saying they are "commercially sensitive".16

Other IFR advocates aren't so shy about offering implausible estimates for IFRs. Steve Kirsch states that the first PRISM reactor "will probably cost around [US]$1 to $2 billion" per 1,000 MW.17 That would make PRISM up to 13 times cheaper (per MW) than the Vogtle AP1000 project in the US.

IFR advocate Tom Blees states that the cost of the first PRISM reactor would be in the range of US$3‒4 billion18 (US$4.8‒6.2 billion / 1,000 MW assuming the estimate is for a twin-reactor block with a capacity of 622 MW).

Future (nth-of-a-kind) PRISMs have reportedly been estimated by GE Hitachi to cost about US$1.7 billion / 1,000 MW18 ‒ radically cheaper than Lazard's latest estimate of US$6.5‒12.5 billion / 1,000 MW for new nuclear plants.19

James Hansen, Richard Branson and GE Hitachi's Eric Loewen claimed in 2012 that IFRs could generate electricity "at a cost per kW less than coal"20 (roughly 2‒3 times cheaper than Lazard's latest estimate of the cost of electricity from new nuclear plants19). Hansen may have been closer to the mark in 2008 when he said: "I do not have the expertise or insight to evaluate the cost and technology readiness estimates" of IFR advocate Tom Blees and the "overwhelming impression that I get ... is that Blees is a great optimist."21


Here are some of the claims made by IFR advocates:

  • GE Hitachi: "In GEH's view, what is generally considered to be "nuclear waste" these days is not really waste at all. Light Water Reactor (LWR) used nuclear fuel is composed of 95 percent uranium, 1 percent transuranics, and 4 percent fission products. Many of these transuranic isotopes have long half-lives, which can create long-term engineering challenges for geologic disposal. By using electro-metallurgical separations, PRISM is designed to perform the recycling of the 96 percent of the fissionable material (uranium and transuranics) remaining in used nuclear fuel."4
  • George Monbiot: "IFRs, once loaded with nuclear waste, can, in principle, keep recycling it until only a small fraction remains, producing energy as they do so. The remaining waste ... presents much less of a long-term management problem, as its components have half-lives of tens, not millions, of years."22
  • Mark Lynas: "For me, the most compelling reason to look seriously at the PRISM is that it can burn all the long-lived actinides in spent nuclear fuel, leaving only fission products with a roughly 300-year radioactive lifetime. This puts a very different spin on the eventual need for a geological repository – instead of something that will be designed to safeguard radioactive material for a million years (technically a very improbable idea), safeguarding waste for 300 years is a very different, and much less challenging, proposition."23
  • Monbiot, Lynas, Fred Pearce, Stephen Tindale and Michael Hanlon: "The PRISM reactor offered by GE-Hitachi [is] a fourth-generation fast reactor design which can generate zero-carbon power by consuming our plutonium and spent fuel stockpiles, thereby tackling both the nuclear waste and climate problems simultaneously ..."24
  • James Hansen: "Nuclear "waste": it is not waste, it is fuel for 4th generation reactors! … The 4th generation reactors can 'burn' this waste, as well as excess nuclear weapons material, leaving a much smaller waste pile with radioactive half-life measured in decades rather than millennia, thus minimizing the nuclear waste problem. The economic value of current nuclear waste, if used as a fuel for 4th generation reactors, is trillions of dollars."25

But even if IFRs worked as hoped, they would still leave residual actinides, and long-lived fission products, and long-lived intermediate-level waste in the form of reactor and reprocessing components ... all of it requiring deep geological disposal. UC Berkeley nuclear engineer Prof. Per Peterson notes in an article published by the pro-nuclear Breakthrough Institute: "Even integral fast reactors (IFRs), which recycle most of their waste, leave behind materials that have been contaminated by transuranic elements and so cannot avoid the need to develop deep geologic disposal."26


According to Tom Blees from the Science Council for Global Initiatives, pyroprocessing ‒ a form of spent fuel reprocessing that dissolves metal-based spent fuel in a molten salt bath ‒ is "proven" technology.27

But if pyroprocessing has been 'proven', it has proven to be a failure. The IFR (EBR-II) R&D program in the US left a legacy of troublesome waste and pyroprocessing has worsened the situation. This saga is discussed in detail by Ed Lyman, drawing on documents released under the Freedom of Information Act.1,28

Lyman states:1

"[P]yroprocessing has taken one potentially difficult form of nuclear waste and converted it into multiple challenging forms of nuclear waste. DOE has spent hundreds of millions of dollars only to magnify, rather than simplify, the waste problem. …

"The FOIA documents we obtained have revealed yet another DOE tale of vast sums of public money being wasted on an unproven technology that has fallen far short of the unrealistic projections that DOE used to sell the project …

"Everyone with an interest in pyroprocessing should reassess their views given the real-world problems experienced in implementing the technology over the last 20 years at INL. They should also note that the variant of the process being used to treat the EBR-II spent fuel is less complex than the process that would be needed to extract plutonium and other actinides to produce fresh fuel for fast reactors. In other words, the technology is a long way from being demonstrated as a practical approach for electricity production."

Ready to deploy?

GE Hitachi claims that "after 30 years of development, the technology utilized by PRISM is ready to be commercialized".16 But government agencies in the US and the UK have reached radically different conclusions (see the article in this issue of Nuclear Monitor: 'Integral fast reactors rejected for plutonium disposition in the UK and the US').

GE Hitachi claims: "PRISM has successfully been through detailed regulatory review in the U.S. In its Report, "Pre-application Safety Evaluation: Report for the Power Reactor Innovative Small Module (PRISM) Liquid Metal Reactor," the U.S. Nuclear Regulatory Commission (NRC) stated: "On the basis of the review performed, the staff, with the ACRS in agreement, concludes that no obvious impediments to licensing the PRISM design have been identified.""16

In fact, the NRC was much more downbeat, stating that "many … uncertainties must be resolved in order to develop a set of analytical tools and a supporting experimental data base necessary for licensing."29

Tom Blees argued in 2011 that the first IFR/PRISM reactor could be built in the US "within the space of the next five years" and that "far from being decades away, a fully-developed fast reactor design is ready to be built."18 But no such reactors have been built ‒ and GE Hitachi has not even submitted a license application.

British IFR advocate Mark Lynas said in 2012: "GE's executives told me that they could get one up and running in 5 years – the PRISM is fully proven in engineering terms and basically ready to go."23 If that's what GE executives said, they were lying and Lynas ought to have been more skeptical. The UK Nuclear Decommissioning Authority is no longer considering IFR/PRISM reactors for plutonium disposition, stating in a March 2019 report that "the studies undertaken by NDA with GEH over the past few years have shown that a major research and development programme would be required, indicating a low level of technical maturity for the option with no guarantee of success."30

In South Australia, nuclear lobbyists united behind a push to persuade the 2015/16 Nuclear Fuel Cycle Royal Commission of the merits of IFR/PRISM reactors. But the stridently pro-nuclear Royal Commission completely rejected the proposal, stating in its May 2016 report: "Fast reactors or reactors with other innovative designs are unlikely to be feasible or viable in South Australia in the foreseeable future. No licensed and commercially proven design is currently operating. Development to that point would require substantial capital investment. Moreover, the electricity generated has not been demonstrated to be cost-competitive with current light water reactor designs."31


1. Ed Lyman / Union of Concerned Scientists, 12 Aug 2017, 'The Pyroprocessing Files',

2. Mark Lynas, 1 March 2012, 'UK moves a step closer to nuclear waste solution',

3. David Flin, 29 Jan 2017, 'PRISM: Waste not, want not',

4. GE Hitachi, accessed 20 May 2019, 'Decades of innovation helped GEH create PRISM',

5. Edwin Lyman, 11 June 2018, 'UCS technical rebuttal to the Idaho National Laboratory's opinions on the Versatile (Fast) Test Reactor',

6. World Nuclear Association, 27 Aug 2014'Cooperation deal to develop advanced reactor',

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

8. Kharecha, P. A.; Kutscher, C. F.; Hansen, J. E.; Mazria, E. 'Options for near-term phaseout of CO2 emissions from coal use in the United States'. Environ. Sci. Technol. 2010, 44, 4050-4062,

9. Barry Brook, 9 June 2009, 'An inconvenient solution', The Australian,

10. George Stanford, 18 Sep 2010, 'IFR FaD 7 – Q&A on Integral Fast Reactors',


12. Harold F. McFarlane, Argonne National Laboratory, 'Proliferation Resistance Assessment Of The Integral Fast Reactor',

13. Brook, B. W., and C. J. A. Bradshaw. 2014. Key role for nuclear energy in global biodiversity conservation. Conservation Biology.

14. Barry Brook, 2009, 'Response to an Integral Fast Reactor (IFR) critique',

15. Blees T. 2008. 'Prescription for the planet: the painless remedy for our energy & environmental crises'.

16. GE Hitachi, accessed 20 May 2019, 'Frequently Asked',

17. Steve Kirsch, accessed 22 May 2019, 'The Integral Fast Reactor (IFR) project: Q&A',

18. Tom Blees, 4 June 2011, 'Response to a consultation on the management of the UK's plutonium stocks',

19. Lazard, Nov 2018, 'Lazard's Levelized Cost of Energy Analysis ‒ Version 12.0',

20. Mark Halper, 20 July 2012, 'Richard Branson urges Obama to back next-generation nuclear technology',

21. James Hansen, 2008, 'Trip Report – Nuclear Power',

22. George Monbiot, 2 Feb 2012, 'We cannot wish Britain's nuclear waste away',

23. Mark Lynas, 1 March 2012, 'UK moves a step closer to nuclear waste solution',

24. A Letter to David Cameron, 15 March 2012,

25. James Hansen, 2011, 'Baby Lauren and the Kool-Aid',

26. Breakthrough Institute, 5 May 2014, 'Cheap Nuclear',

27. Tom Blees, Nov 2018, 'SCGI President's Message, November 2018',

28. Edwin Lyman, 2017, 'External Assessment of the U.S. Sodium-Bonded Spent Fuel Treatment Program',

29. US Nuclear Regulatory Commission, Feb 1994, "Preapplication Safety Evaluation Report for the Power Reactor Innovative Small Module (PRISM) Liquid-Metal Reactor",

30. UK NDA (Nuclear Decommissioning Authority), March 2019, Progress on Plutonium Consolidation, Storage and Disposition,

31. Nuclear Fuel Cycle Royal Commission Report, May 2016,