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Four safety critical nuclear reactor parts you should be paying attention to

Nuclear safety has recently returned to mainstream culture via the popular HBO mini-series Chernobyl. The show dramatizes the 1986 nuclear disaster where a steam explosion and subsequent fires caused at least 5% of the radioactive reactor core to be released into the atmosphere near the city of Pripyat, Ukraine.

Much of Europe was affected by the disaster. Sweden registered increased radiation levels after the explosion and is still reporting concerns. More than 30 deaths of operators and emergency crews have been recorded. However, the total number of fatalities, injuries and illnesses remains unknown. 

Chernobyl is one of two nuclear disasters to be classified as a level 7 accident, which is the maximum classification, on the International Nuclear Event Scale. It is also known as the most disastrous economically. Damage caused by Chernobyl is estimated to be $235 billion.

Since Chernobyl, there have been 57 nuclear accidents, with around two-thirds of them occurring in the United States.

The US Nuclear Regulatory Commission (NRC) closely monitors plants and projects using licensing, inspection and enforcement powers. The NRC insists that the highest of standards are consistently met to ensure public health and safety, environmental quality and national security.

Because of these demands and the high-risk environment of nuclear energy work, professionals need to continuously monitor the state of their equipment. Here are four parts of nuclear reactors where common problems often arise:

1. Steam Generators

Steam generators are used to convert water into steam from the heat that is produced in the reactor core. The steam then gets transferred to the turbines where it produces electricity. There are typically two to four steam generators for each individual nuclear reactor.

When maintenance on a steam generator is required, it causes a complete shut-down of the nuclear reactor, so it is important to be as efficient as possible. One of the most common problems with steam generators are studs becoming loose, and since there are so many studs on each steam generator this process can be time consuming. To minimize downtime, the best service engineers use a Multi-Stud Tensioning system to tension all of the studs on one cover simultaneously.

2. Reactor Coolant Pumps

One of the most important parts of a nuclear reactor, the reactor coolant pump, ensures a safe heat transfer and makes sure the reactor does not overheat.

Because reactor coolant pumps are vital parts of nuclear reactors, they require constant attention. Specifically, the coolant pumps need to be leak-free. This involves tensioning fasteners and studs constantly, which can be extremely tedious work. Many nuclear plants have been moving away from using bolt heaters to tension bolts and instead have adopted a new fastener involving a hardened washer.

3. Boiling Water Reactor Nozzles

There are nozzles all throughout the reactor system. They connect the system’s components and allow for the flow of water and steam.

The main nozzles of the reactor are susceptible to inter-granular stress corrosion cracking. This is often identified while the reactor is being inspected during an outage. Repairs to nozzles require cutting and/or grinding, which can be hazardous to other parts of the reactor. Ultrasonic testing is a fast and efficient way that industry professionals use to diagnose what needs to be cut without harming the rest of the system.

4. Pressurized Water Reactor Pressurizer

The pressurizer component of a pressurized water reactor makes sure that the coolant for the reactor does not boil by maintaining it at a specific pressure which keeps it in its liquid state.

Several lines run between the pressurizer and the safety valve, so it is important to keep the area in good condition. There are nozzles and lines that require repair, often because of high stresses on the pressurizer. Most commonly, overlay repair is necessary, which requires the deployment of technicians and welding machinery.

Nuclear reactors are powerful, yet fragile systems. One incorrect step in a defined process and there could be major consequences. Hydratight provides services for the nuclear power industry with the aim of ending all nuclear accidents. Find out more about the nuclear services we provide here.