Safety Features of a Nuclear Reactor

Remarkably, given the volatility of radioactive materials, there have been very few major nuclear disasters since the first nuclear power plant came online in the former Soviet Union during the 1950s. However, following the handful of catastrophic incidents that occurred in the intervening decades, nuclear reactor safety systems have become increasingly sophisticated.

Here, API UK reflects on some of the worst nuclear disasters, the safety features of a nuclear reactor and the role of pneumatics in nuclear power plants.


Safety has always been a major consideration for nuclear energy producers, industry regulators and governments. As a result, the nuclear industry operates under stringent safety standards. Some of those standards were introduced directly from lessons learnt following a handful of unfortunate accidents and failings at nuclear power plants worldwide. The following are three of the most high-profile nuclear disasters ever to occur.


On 28 March 1979, the Three Mile Island power station near Harrisburg, Pennsylvania, suffered a major meltdown to the core of its number two reactor. A malfunction led to the swift and automatic shutdown of the reactor. But when a relief valve failed to close, vital coolant was drained, which meant the heat in the reactor couldn’t be removed – ultimately leading to the meltdown. Remarkably, only a small amount of radioactive gas was released into the atmosphere, and no injuries or adverse health effects were recorded. 


Seven years after Three Mile Island, a catastrophic incident occurred at the Chernobyl 4 reactor in Ukraine. Operators at the plant decided to test how long the turbines in the reactor would continue turning after a loss of electrical power. According to the World Nuclear Association, the “flawed Soviet reactor design” and “serious mistakes” of plant personnel (including disabling automatic shutdown mechanisms) are what led to the ensuing explosions that destroyed the reactor.

Two workers died that night, followed by 28 plant workers and firefighters several weeks later due to acute radiation syndrome. The accident displaced 350,000 evacuees and released 5% of the reactor’s radioactive core into the atmosphere (deposited far and wide across Europe). The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reported that around 5,000 subsequent cases of thyroid cancer were “probably” due to exposure to high doses of radiation.


Japan’s notorious seismic activity was the cause of a nuclear disaster at the Japanese nuclear plant Fukushima Daiichi in 2011. On 11 March that year, a 9.0 magnitude double earthquake triggered a 15-metre tsunami that flooded the entire site. This effectively meant that three of the four reactors at the Daiichi plant could not cool themselves, leading to large-scale meltdowns in each of their cores. Incredibly, there were no fatalities as a direct result of the nuclear disaster. However, 19,500 people were killed by the earthquake or tsunami.


“Apart from Chernobyl, no nuclear workers or members of the public have ever died as a result of exposure to radiation due to a commercial nuclear reactor incident,” said the World Nuclear Association. “Most of the serious radiological injuries and deaths that occur each year (2-4 deaths and many more exposures above regulatory limits) are the result of large uncontrolled radiation sources, such as abandoned medical or industrial equipment.”

If that statement and those figures come as a surprise to you, they should indicate the strict safety standards and practical measures that the nuclear industry has instigated. Of course, no manufacturing process is completely infallible (as we’ve seen from the nuclear accidents mentioned above). But no one is more aware of the dangers of handling and processing radioactive materials than the nuclear industry. As such, nuclear reactor safety systems have become increasingly sophisticated. 


Western nuclear power plants have adopted a so-called “defence-in-depth” approach to maintaining safety within reactors. This principle revolves around the key areas of prevention, monitoring, and action. Not to mention a multi-layered series of safety features consisting of fuel encased in solid ceramic pellets packed into zirconium alloy fuel rods and stored in 30cm thick steel pressure vessels. All of these are contained in a concrete structure with one-metre thick walls. A substantial cooling system will also be found on-site.

In terms of the pneumatic safety features of a nuclear reactor, many sites rely on thousands of valves and actuators to control critical processes. Pneumatic spring-return actuators provide the necessary speed and redundant controls to operate critical process control valves, like quarter-turn valves and diaphragm valves, and to do so effectively in shutdown conditions. Consequently, pneumatic equipment continues to provide a safe and efficient solution for nuclear power plants and the wider nuclear industry.


API UK manufactures a range of durable stainless steel pneumatic cylinders and valves capable of operating in the face of even the most demanding nuclear environments. Constructed from the highest grade of corrosion-resistant AISI 316 stainless steel, our range of double-acting stainless steel cylinders and heavy-duty stainless steel valves are rugged enough to deliver reliable, safe and consistent performance. So, look no further than API UK for dependable, cost-effective pneumatic products for nuclear applications.

To discuss your nuclear application’s requirements or arrange a free on-site visit, speak with our technical team members today. As expert manufacturers of stainless steel pneumatic cylinders and valves, we can explain the options available and guide you towards the best system solution for your application. Call us on 01782 206 995, email [email protected], or complete our contact form.