Nuclear energy and the use of it can be controversial topics. There are going to be staunch supporters of it that claim nuclear energy is an energy source that produces a large amount of energy for a relatively low amount of potential waste. Opponents of nuclear energy are likely to cite how long the waste products last as well as discuss how dangerous the power plants themselves can potentially be, and the Chernobyl disaster will likely be a key piece of supporting evidence.
Writing a claim that either supports or opposes nuclear energy can be accomplished using a thesis statement. A thesis statement makes and argument that the body of the paper intends to prove. With such a polarizing topic, you can write a thesis statement that identifies both sides of the debate, and the paper will explore arguments related to both. The following thesis statement is an example of this kind of claim statement.
"Although dangers have been associated with nuclear energy, history has shown that nuclear energy is a safe form of energy that produces a tremendous amount of energy for a relatively small amount of waste."
If you disagree with that statement, it is easily flipped around to support the main claim that nuclear energy is something that should not be used.
The other way to do a thesis/claim statement is to create a statement that is followed with specific ideas that will be used to support the statement. For example, you could write, "Nuclear energy should be used because it is safe, clean, and incredibly powerful."