Question

why the nuclear and hydroelectric power plants cannot be constructed in densely populated regions????,?

Answer 1

Sites at risk of earthquake or near heavily populated areas would be instantly ruled out.

But concerns of flood risk, coastal conditions and "environmentally-protected" status would be considered "less absolute" and could be overridden.

Nuclear plants are built on the shores of lakes, rivers, and oceans because these bodies provide the large quantities of cooling water needed to handle the waste heat discharge.

Answer 2

they are harmful to living organisms