Cutting up and transporting pipelines. Sounds simple, right? Far from it, when it comes to the loop pipes – the main coolant pipes around the reactor of a nuclear power plant.
This time, KOBAU’s specialists for the dismantling of nuclear power plants had to master an assignment at the KKU Unterweser that only seemed simple at first glance: the dismantling of four pipelines, each 44 meters long and with a diameter of about one meter. During operation, these conducted the coolant between the reactor, the four main coolant pumps and the four steam generators in the now decommissioned Unterweser nuclear power plant.
What you should know to make KOBAU’s challenges comprehensible: The wall thickness of the piping amounts to full 50 mm and is made of high-alloy heat-resistant steel. In order to make pipe sections out of it that are not too heavy and not too big to be transported, these pipe sections had to be cut into 0.5-meter-long partial pipe sections.
If you are an ambitious DIY’er and you are thinking of using an angle grinder, colloquially also known as Flex, you’ll have to think again. Anything that causes heat or even sparks is not welcome in a nuclear power plant because the risk of contamination transfer would be far too high. Therefore, the options “thermal” or “hot mechanical” cutting have to be eliminated. A normal saw would quickly come to an end here . The solution of our choice was a so-called “circular cutter”, which uses a chisel to remove chips round by round and thus separates the pipe. Similar to how a beaver fells down a tree – only much more precise and efficient.
This process generates virtually no heat, which makes it suitable for use in sensitive areas such as a nuclear power plant. However, each cut also takes time, about two hours each – a beaver needs a little longer for a tree. But the beavers have better working conditions – our specialists in the nuclear power plant need special training, a full face piece respirator and “obstructive” protective gloves.
The pipe sections disassembled in this way have a length of 0.5 meter and still weigh approx. 500 kg but are now “handy” enough for transportation to the handover point in the power plant. The pipe sections are shipped to the USA and melted down there. Due to the high material quality, new pipelines for nuclear power plants are made from them.
Next, the four main coolant pumps will be dismantled, transported and loaded into containers. Each of the pumps weighing 42 tons. But that’s another story for one of the next ROBUR newsletters.
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