The major problem in harnessing nuclear energy is (c) dispose of spent fuel safely.
Explanation: While other aspects of nuclear energy production are important, the safe disposal of highly radioactive spent nuclear fuel poses a significant long-term environmental challenge.
Why other options are incorrect:
(a) split nuclei:
Fission, the process of splitting nuclei, is the fundamental principle behind nuclear energy generation. While controlling the fission reaction is crucial, the ability to split nuclei is a fundamental aspect of nuclear power.
(b) sustain the reaction:
Maintaining a controlled chain reaction in the reactor is essential for generating energy. However, this is a technical challenge that has been largely solved with reactor design and control systems.
(d) convert nuclear energy into electrical energy:
Converting the heat generated by nuclear fission into electricity is a well-established process using steam turbines. This conversion technology is a challenge, but it’s not the primary hurdle in harnessing nuclear energy.