Is this statement correct?
The "that" clause serves as a complement to the noun "fact" and provides additional information about what is asserted. It doesn't modify the fact; instead, it acts as a subordinate clause that explains or specifies the nature of the fact being asserted.

Here is a sentence.
"The fact is asserted that nuclear power plants are becoming safer to operate than many people think"

Question

Is this statement correct?
The "that" clause serves as a complement to the noun "fact" and provides additional information about what is asserted. It doesn't modify the fact; instead, it acts as a subordinate clause that explains or specifies the nature of the fact being asserted.

Here is a sentence.
"The fact is asserted that nuclear power plants are becoming safer to operate than many people think"

Answer

yep, it unites two parts of the complex sentence
1 power plants are becoming
2 it's a fact

Answer

"That" is serving as a relative pronoun. It's not complementing "fact", it's replacing it to avoid repetition. Without the relative pronoun, you would two sentences with "fact" as the subject:

"The fact is asserted. The fact is that nuclear power plants are becoming safer to operate than many people think"