Even if you’re not a history buff, you probably know that what happened at the Chernobyl Nuclear Power Plant back in 1986 was bad news. The new HBO series, Chernobyl, has a lot of people asking the same question: Is nuclear power safe? More specifically, some want to know whether or not the other reactors of the same design as Chernobyl’s Reactor No. 4 are ticking time bombs, poised to create a fresh disaster. The good news is that there’s good news, and you have less to worry about than you think.

What happened?

The most basic question is also one of the most complicated ones. In short, the meltdown of Reactor No. 4 was the result of an experiment gone very, very wrong. Plant workers decided to run a test to see if they could manually reroute emergency power fast enough to keep the reactor running at stable levels in the event the backup generators went offline. In most cases, one might expect there to be a failsafe in place when all that’s keeping several tons of uranium stable is the accuracy of the human hand. In this case, however, you’d be wrong.

The plant workers raced against the clock and lost. With no automatic failsafe to trigger the generators, as they’d been manually taken offline for the experiment, the coolant pumps keeping the fission reactions running at a controllable rate dipped well below safe levels. The reactor began to run hot, and though the workers got coolant running again, the activity in the core was rapidly snowballing into a much bigger problem. Control rods were inserted into the reactor core to slow the reactions, but poor alignment caused them to jam a third of the way in. Three seconds was all it took for a series of internal breaks to mix uranium and steam, building up enough pressure to cause an explosion. Shortly after that, a second, much more damaging explosion sent half of the reactor, along with heaps of molten graphite through the roof. Radioactive steam billowed from the hole at the top of the building, sending a cloud of poison over the town of Pripyat.

Chernobyl’s meltdown wasn’t the result of a manufacturing defect or a freak mistake. One of the most infamous disasters in the history of nuclear power was, more than anything, the product of severe human error. Flagrant disregard for safety provisions and probably a little too much early morning vodka resulted in a massive disaster that killed and maimed hundreds and uprooted an entire city. The exclusion zone, which initially included Pripyat and the surrounding area, is finally open to the public again, but that doesn’t mean the area isn’t still dangerous. Certain places like the reactor itself and the basement of the local hospital are still off-limits due to high radiation levels, and visitors face the risk of radiation sickness if they aren’t careful about what they touch.

What about the others?

Not all nuclear plants are created equal. Chernobyl’s Reactor No. 4 was something called an RBMK reactor. They rely on enriched uranium to generate power and graphite control rods to monitor and maintain the fission reactions that make that power. Across Russia, there are 11 remaining RBMK reactors, and while their design is outdated and flawed in more ways than one, there’s no real risk of a meltdown on the scale of Chernobyl unless someone gets another crazy idea for an experiment. The primary issues with RBMK reactors are the location and design of their control rods, the layout of their coolant systems, and the fact that the cooling system tended to create a dangerous positive void coefficient, which played a significant role in the loss of control of Reactor No. 4.

A nuclear future

While it’s understandable to feel a sense of doubt when it comes to nuclear power after watching or reading something about Chernobyl or Three-Mile Island, nuclear power is an ever-evolving field that could decrease our global carbon footprint. Modern nuclear reactors are far safer and more efficient than their predecessors, and next-generation reactors aim only to improve output. Given the volatile nature of the fission materials, modern nuclear plants have a series of safeties and failsafes to ensure a meltdown cannot occur unless someone meddles where they shouldn’t (like what happened at Chernobyl). Improved coolant systems keep reactions running at a consistent and manageable rate, and modern control systems ensure that, in the event of a SCRAM or other emergency, the reactions are slowed to safe levels, preventing a core meltdown and subsequent explosion.

One of the few downsides to nuclear power is that building a plant takes time, something we don’t have a lot of when it comes to minimizing further damage to our environment. Unlike wind turbines, which can be popped up practically overnight,  building a nuclear power plant takes years of zoning, planning, and of course, building. Once they’re up and running, however, their carbon footprint is practically nonexistent. The plumes of white “smoke” you so often see billowing from the concrete cooling towers of nuclear plants are actually steam. The plants themselves don’t produce carbon dioxide, but the process of mining the fuel does. In spite of the environmental costs of production, nuclear power plants are still more environmentally sustainable than fossil-fuel-powered plants. While nuclear might not be the sole solution to a more sustainable and Earth-friendly future, it certainly isn’t something to shy away from or fear. What happened at the Chernobyl plant was indeed a disaster, but it is by no means the norm, even for old RBMK-style reactors.