Integral Fast Reactor Inherent Safety Features

Darian Orozco
February 20, 2016

Submitted as coursework for PH241, Stanford University, Winter 2016


Fig. 1: Experimental Breeder Reactor II, which served as the prototype for the Integral Fast Reactor. (Source: Wikimedia Commons)

The use of nuclear reactors for electricity generation has always had opposition from the public. The Not In My Back Yard movement has often been a focal point of the opposition. The idea being that nuclear energy is inherently dangerous and people don't want to have reactors near them. Accidents such as Three Mile Island, Chernobyl, and Fukashima have helped spread the fear of nuclear energy. Looking at polls of public opinion on the safety of nuclear energy before and after the Chernobyl meltdown showed an increase from 30% to 51% of the public believing that nuclear energy is either not very safe or dangerous. [1] However, when looking at the data it can be seen that nuclear energy is actually the safest form of electricity generation in a death or serious illness per TWh comparison, see Table 1. With world energy demand increasing, new electricity generation stations will be required. Many climate change activists vehemently oppose the burning of coal for electricity and push for more renewables such as solar and wind. However until energy storage technologies advance to a point where they are economically feasible at grid scale, base load generation will be needed. Cleaner burning natural gas is often the answer for places looking to move away from coal despite nuclear reactors having the capacity to provide near carbon free base load electricity. This comes in part due to the public opposition. Even groups such as the Green Peace Party strongly oppose the expansion of nuclear energy despite the data about its safety and carbon footprint. The opposition stems from the belief that reactors are unsafe, but even more so from the concerns over the nuclear waste. The same survey mentioned early found that 61% were pessimistic concerning the safe disposal of waste, a number that didn't change significantly before and after the Chernobyl incident. The Integral Fast Reactor (IFR) provides unique solutions to both these safety concerns using liquid sodium cooling, a pool-type reactor configuration, metallic fuel, and an integral fuel cycle. [2]

Generation Source Deaths from Accidents Related Effects Deaths Related Effects Serious Illness
Coal/Lignite .12 28.55 261.5
Natural Gas .021 2.8 30
Nuclear .022 .052 .22
Table 1: Deaths and Serious Illness per TWh by Electricity Generation Source. [3]

Passive Safety Features

An ideal reactor should be able to safely shut itself down without requiring operator input or outside sources of power. If inherent safety features could achieve this, even in the case of a natural disaster or operator error, reactors would avoid any serious meltdown. In the IFR this achieved by using metallic fuel in a reactor core that sits in a pool of liquid sodium. In this setup a loss of power would lead to the reactor core to be cooled passively by convection. Should the pumps circulating the coolant lose power, the increased temperature causes thermal expansion in the coolant allowing neutrons to escape the reactor core, thus providing negative reactivity feedback that ultimately starts a power rundown. This mechanism is made feasible through the choice of metallic instead of oxide fuel. The metallic fuel has much higher thermal conductivity making it more difficult to raise its temperature allowing for the thermal expansion of the coolant to safely shut down the reactor. These safety features were tested in 1986, by cutting off power, stopping coolant pumps, and not allowing any operator input. The result was a slight increase in core temperature followed by the reactor shutting itself down without the need for power, pumps, or operator input.

Fig. 2: After Chang. [2]

Improved Recycling and Waste Management

To Nuclear waste can be simplified into two groups, fission products, comprising of many different isotopes, and actinides, radioactive elements such as uranium, plutonium, and curium. The importance of making this distinction can be seen in looking at Fig. 2 showing how these groups differ by four orders of magnitude in their approximate lifetime of the nuclear waste. Both the fission products and actinides are produced in reactor cores, however unique to the IFR is the ability to use a site- integrated pyroprocessing center to separate out actinides from the waste. This pyroprocessing technology is far better than current processing techniques at removing actinides. Additionally, the IFR is better equipped for actinide burning than any other reactor type.


Two major hurdles to nuclear safety solved simply in the way the IFR is designed. Although nuclear energy is already a safe source of electricity generation compared to coal and natural gas, this reactor design could put to rest the publics concern over the safety of nuclear energy.

© Darian Orozco. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] C. de Boer and I. Catsburg, "The Impact of Nuclear Accidents on Attitudes Towards Nuclear Energy." Public Opin. Quart. 52, 254 (1988).

[2] Y.I. Chang, "The Integral Fast Reactor," Nucl. Technol. 88, 129 (1989).

[3] A. Markandya and P. Wilkinson, "Electricity Generation and Health," The Lancet 370, 979 (2007).