Small Modular Reactor

Traditional giant nuclear plants have to be built on site. For years, tens of thousands of workers pour huge concrete walls and connect tangled pipes. If the weather turns bad or something goes wrong on site, construction drags on and on, and astronomical extra costs often pile up.

A small modular reactor works more like LEGO. The main parts are assembled as modules in a factory. Modules made in a standardized process get carried to the site by truck, train, or ship and installed there. That means less work on site, so construction time and upfront cost are expected to drop significantly.

Parts are made to spec under strict quality control inside a factory, so defects and failures that can happen during on-site building are also expected to be less likely. And when demand for power grows, you can add reactors one at a time, like snapping on more LEGO bricks. That eases the burden of putting up all the money at the start.

This flexibility means an SMR can be placed right next to where power is needed, such as a remote area, a mine, or a desalination plant that is hard to connect to the grid. Since you don't need to build long lines of huge transmission towers, there's also hope of fewer fights over power lines.

Past accidents at big nuclear plants had different causes. At Fukushima, an earthquake and tsunami cut off outside power and cooling stopped. At Three Mile Island and Chernobyl, equipment failures, operator errors, and design problems played a part. In the case where power was lost, the motor-driven pumps that keep cooling water circulating stopped. The fuel could no longer shed its heat, and it boiled and melted down.

Many SMR designs aim to cool themselves without outside power or human action. They use natural convection: hot water rises and cooler water sinks, so the coolant keeps circulating without any pumps.

On top of that, many designs use an integral vessel design, putting the reactor core and the steam generator inside one sturdy vessel. The big external pipes that used to link the parts together are gone entirely, which greatly reduces the risk of a pipe break leaking radioactive coolant.

Some designs even sink the whole reactor in a giant water tank or bury it deep underground in case of an accident. The goal is to cool it for days using only the surrounding air and water, so a power loss doesn't turn into a major accident. But this hasn't yet been fully proven in real operation.

To be more precise, an SMR isn't a perfect cure-all that beats a big plant in every way. A smaller reactor makes less electricity in total, so the upfront construction cost per kilowatt (kW) of capacity can actually end up higher than for a large plant.

To overcome this economic weakness, reactors need to be churned out in factories by the dozens or hundreds. Only when the market is big enough to reach economies of scale through factory-style mass production can SMRs supply cheap electricity.

Also, being small and safer doesn't mean there's no spent nuclear fuel (used fuel rods) that gives off radiation. One study (2022) even suggests an SMR could produce more radioactive waste for the same amount of power, and the debate continues. Finding a repository to bury high-level radioactive waste safely and permanently is still a major unsolved problem.