He is researching the effects of underground nuclear tests.

He is spending a lot of time on experimental research.

It is reported that North Korea has conducted another underground nuclear test.

Animal experiments are necessary for the advancement of science, but there are also ethical issues.

Nuclear tests pose a great threat to world peace.

This experimental device is used to create new substances.

He is learning about the handling of experimental animals.

He decided to become a subject of the human experiment for the new drug.

Well then, I'm off.

He admitted that it is difficult to execute the plan, saying 'it is easier said than done.'