This nuclear reactor claims to be the safest in existence. And it’s ready to hit the market

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The technologies involved in commissioning nuclear fission reactors have come a long way over the past four decades. The most advanced fourth generation designs propose solutions that make them cleaner, safercompact and cheaper than second-generation reactors such as those currently operating not only in Spain, but in most of the countries in the world that have opted for nuclear energy.

One of these state-of-the-art fission reactors is the SMR-160, which has been designed by the American company Holtec International. The technicians who have devised it assure that this is currently the safest nuclear reactor in existence, and at the heart of its strategy lies a totally passive operation scheme, which, therefore, does not require active safety elements.

As explained by Alfredo García, better known on Twitter for his alter ego @NuclearOperator, in a thread very interesting that you have recently published, this nuclear reactor does not need to receive water from the outside, nor does it need electricity. It doesn’t even require operators intervene if an accident occurs. Sounds really good. In fact, it sounds so good it’s surprising, but these claims are backed by strong technical arguments.

The SMR-160 refines a technology proven in more than 300 nuclear reactors

The device designed by Holtec is a compact and modular nuclear fission reactor of the PWR type (Pressurized Water Reactor). These devices work with pressurized water, and six of the seven operating reactors housed in the five Spanish nuclear power plants of light water in operation use this technology. The remaining reactor, that of the Cofrentes nuclear power plant, is a boiling water reactor (BWR). Boiling Water Reactor).

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According to Alfredo Garcia, 302 of the 443 reactors currently in operation on the planet are of the PWR type, so it is clear that their base technology is widely tested. Interestingly, pressurized water reactors were initially conceived for use in nuclear submarines, but soon proved their suitability for power plants. An important fact: the SMR-160 reactor has 160 MW of electrical power.

As fuel it uses exactly the same one used by most of the nuclear reactors in activity: enriched uranium oxide. If you want to know in detail how the fuel rods used in nuclear reactors are manufactured and what their properties are, you can read the article that we published shortly after our visit to the factory owned by the Spanish public company ENUSA Industrias Avanzadas in Salamanca.

302 of the 443 reactors currently in operation on the planet are of the PWR type, so it is evident that their base technology is widely proven

Conventional PWR nuclear reactors incorporate three different circuits. We talked about them in great depth in the article that we published after visiting the control room simulator that Tecnatom has in San Sebastián de los Reyes (Madrid), but now it is good for us to briefly review what they consist of. The first of them is him primary circuit, which is closed. The vessel containing the fuel rods and the heat exchanger are involved in it.

The heat exchanger acts as a steam generator, so a second circuit is responsible for introducing the cold water into its interior which, when it comes into contact with the hot water from the primary circuit, boils. From there comes the necessary steam to transfer the kinetic energy to the turbine that will make it possible to obtain electricity thanks to the action of the alternator.


Each of the SMR-160 reactors installed in a plant equipped with several units is independent from the other reactors. In addition, it works completely autonomously.

Once the fluid passes through the turbine, the water vapor cools and condenses inside an additional tank to promote the appearance of liquid water that will be reintroduced into the heat exchanger, thus giving rise to a second closed circuit known as secondary circuit. The heat exchanger, turbine and alternator participate in this circuit.

The SMR-160 cooling system does not require additional water. Dissipates thermal energy directly into the atmosphere

The third and last circuit is the cooling circuit, and is responsible for introducing the necessary cold water into the condensation tank to make the condensation of the water vapor possible. The water in this circuit comes from the sea or a river near the nuclear power plant, which is why it is necessary to house this type of power plant near one of these two natural resources, which brings us to one of the tricks that allow the reactor SMR-160 stand out from the conventional PWR reactors.

And it is that the device designed by Holtec does not need to be located near the sea, a river or a lake. Its cooling system does not need the contribution of additional water because it dissipates thermal energy in the form of heat evacuated by the core. straight into the atmosphere using air-cooled condensers. In addition, according to its designers, it is so safe that it can be installed in the vicinity of populated areas without assuming the risks that the proximity of a conventional nuclear power plant would imply.

This changes everything: it is completely passive and does not need electricity to operate

One of the most important advantages of the SMR-160 reactor is that the water circulates through the primary circuit only due to to the action of gravity. In this circuit there are no electric pumps involved, so it does not need electricity to carry out its task.

And, what is even more important, gravity persists indefinitely because, as is logical, it is a force independent of human action, so its effect on the movement of water through the primary circuit is a priori infallible. A brief note: gravity is not actually a force, but that is a discussion that we can develop in another article if you find it interesting.

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As we have just seen, the primary circuit does not require the intervention of any electric pump, but neither do the other cooling and safety systems. By design, this reactor is capable of dissipating heat from the core without the intervention of any pump, so it does not require the slightest external contribution of electricity. The advantage of this strategy is obvious: is immune to power failures.

In addition, if an accident of any kind occurs, all radioactive elements are confined and isolated inside the containment building, which has been designed to dissipate heat directly into the atmosphere through a steel structure. All this sounds very good, but we cannot ignore that one of the strongest assets of the SMR-160 reactor is that, as Alfredo Garcia explains“no operator action is required to place and maintain the reactor in a safe shutdown condition.”

In the event of an accident, whatever its type, all radioactive elements are confined and isolated inside the containment building

Passive safety systems are, in short, one of the most relevant contributions of the III+ and IV generation designs. They are designed to go into operation when, for whatever reason, the nuclear reactor deviates from your normal itinerary of operation. Until the arrival of these designs, these security systems required the express activation of external equipment, but the problem is that this strategy introduces a possible additional point of failure if the latter do not come into operation correctly.

As we have just seen, to solve this problem, the passive safety systems linked to state-of-the-art nuclear reactors resort to natural physical phenomena, such as gravity or heat transfer through convection, in order to act on their own, without anyone asking them to do so. active and without the need to use external power sources. And there is no doubt that this strategy makes a big difference compared to conventional nuclear reactors.

Another promise of the SMR-160: it is cheaper and its commissioning is much faster

Holtec has confirmed that it is ready to begin commercial operation of its SMR-160 reactor. In fact, it plans to put the first one into service in 2029. It will cost approximately $1 billionand the construction of the facilities will last for 36 months, although its designers defend that they will be able to cut this period of time to 30 months in the following units.

According to Holtec, installing each SMR-160 reactor will cost approximately 1 billion dollars.

To put this cost in perspective we can take a look at that of two of the nuclear facilities which are currently under construction. Hinkley Point C, in the United Kingdom, will cost around 23 billion euros, and the third reactor at Flamanville, in France, accumulates a cost of 19 billion euros. Holtec argues that the cheapest option requires deploying its SMR-160 reactor in sets of four, but even so, it is clear that his proposal is much cheaper than the other types of reactors.

On the other hand, the construction of a nuclear power plant so far takes much longer than the 30 to 36 months that Holtec talks about for its SMR-160. This short period is possible because the components of the nuclear facility arrive at their final location prefabricated, so it is only necessary to assemble them. And finally, its useful life is at least 80 years old, so, according to Holtec, with proper maintenance it will be possible to extend it up to 100 years. It sounds good, and there is no doubt that it would be good news if everything that this company has promised us is finally consolidated. We will see.

Images: Holtec International

More information: Holtec International | nuclear operator

The technologies involved in commissioning nuclear fission reactors have come a long way over the past four decades. The most…

The technologies involved in commissioning nuclear fission reactors have come a long way over the past four decades. The most…

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