Final answer:
The incorrect statement regarding fusion reactors is 'It will be ready in a decade, so we do not need to invest in other energy sources.' This is overly optimistic and does not reflect the current state of fusion research and development.
Step-by-step explanation:
The question is asking to identify which statement is not true regarding fusion reactors. Here are the assessments of the given options:
- Scientists have sustained a fusion reaction where the energy produced was greater than the energy required to initiate the reaction. This has not yet been achieved. As of the knowledge cutoff in 2023, while there have been strides towards a sustainable and efficient fusion reaction, no fusion reactor has successfully produced more energy than was put in.
- Uses the energy released from hydrogen isotopes combining to form helium. This is true; fusion reactors operate on the principle of fusing hydrogen isotopes to form helium, releasing a significant amount of energy in the process.
- Has the potential to be a cleaner, safer energy source than fission. This is also true; nuclear fusion is considered to have the potential to be a much cleaner and safer source of energy when compared to nuclear fission, due to its less radioactive waste and lower risk of accidents like meltdowns.
- It will be ready in a decade, so we do not need to invest in other energy sources. This statement is not true and thus is the mentioned correct option in final answer. Predictions about the timeline for fusion energy to become commercially viable have historically been overly optimistic, and ongoing research suggests that it may still be several decades before fusion reactors are ready for widespread use.