Operation Plowshare was a big project run by the United States government in the 1960s. The government wanted to find ways to use nuclear bombs for peaceful purposes, instead of just for war. They thought that they could use nuclear bombs to help with things like mining and construction.
It's like when you have a hammer, you can use it to break things, but you can also use it to build things if you're careful. The government wanted to use their big hammer, the nuclear bomb, to build things.
So, they did some experiments. They exploded nuclear bombs underground to see if they could make big holes for mining or to create canals or lakes.
But, it turned out that using nuclear bombs for peaceful purposes wasn't a good idea. The explosions caused a lot of radioactive dust and contamination, which made people sick and wasn't good for the environment either.
So, the government decided to stop doing these kinds of experiments, and instead focused on finding other ways to solve problems like mining and construction.
In summary, Operation Plowshare was a project where the government tried to use nuclear bombs for peaceful purposes, but it turned out to be a bad idea because it caused a lot of radioactive contamination.