<human>:  What are the pros and cons of nuclear energy?
<bot>: 

Pros:
1. Relatively inexpensive to generate electricity
2. Low emission of greenhouse gases and pollutants 
3. High-density energy source 
4. Nuclear fuel is very efficient 

Cons:
1. High initial cost 
2. Nuclear waste disposal is difficult and costly 
3. Risk of accidents and their consequences
4. Susceptibility to sabotage and terrorism