It's nice to hear from you, too! You have done a good job of researching your topic and providing a convincing argument. You will have to ask your instructor if it is all right to use the first person "I" in your essay. Argumentative essays often allow use of the first person, but some instructors prefer third person.
Yes, you do have some grammar mistakes, although your English is really quite good. Let's look at a few things:
"By this happened, new nuclear energy is existed."
I think what you mean here is "Because of this, nuclear energy is being used more often."
"However, we should not switch to nuclear energy to expose ourselves to great danger and I totally agree with this statement."
You should end this sentence after "danger."
"It will results that public health affected negatively."
This will result in a negative effect on public health.
"In fact, there is also leakage of radiaoactive waste as it is dumped in rural settings."
Check the spelling of "radioactive."
"So ,if we are switching to nuclear energy, great danger is certainly exposing to us."
A switch to nuclear energy can expose the public to great danger.
If your university has a Writing Center, I think you might find that to be a valuable resource. Writing Centers exist for the sole purpose of helping students learn the basics of composition. And of course, EssayForum is always here!