Final answer:
A conventional fission nuclear reactor cannot explode as a bomb because control mechanisms prevent a rapid chain reaction, it lacks sufficient enrichment and critical mass assembly and possesses safety systems designed for containment. The correct option is c).
Step-by-step explanation:
A conventional fission nuclear reactor cannot explode as a bomb due to several critical design features that differ from nuclear weapons. The primary reason is option c) Control mechanisms prevent rapid chain reaction. In a nuclear reactor, control rods composed of materials such as cadmium or boron act to absorb excess neutrons, thereby regulating the chain reaction rate. Additionally, the nuclear fuel used in reactors is typically less enriched than that used in bombs, and the physical arrangement of the fuel prevents the assembly of a critical mass required for a bomb-style explosion.
Another critical difference is the presence of a nuclear moderator, which slows down the fast neutrons, increasing the likelihood of neutron capture by the fuel and sustaining the controlled chain reaction necessary for energy production. Furthermore, sophisticated safety systems are in place to shut down the reactor during operating anomalies or emergencies. These systems include automatic and manual control rod insertion, emergency coolant systems, and passive safety features designed to be fail-safe. In the unlikely event of a reactor core meltdown, the dispersal of the core materials and the design of the reactor containment structure would still prevent the type of detonation seen with nuclear weapons. Therefore, while a reactor incident can lead to a release of radioactivity and significant consequences, it will not result in a nuclear explosion comparable to a fission bomb.