Yes .trv said:Or are you more leading me towards the respective cross-sections? ...so the answer would depend on the neutron energies. :S.
The critical mass of 235U and 239Pu refers to the minimum amount of these isotopes needed to sustain a chain reaction in a nuclear reactor. It is typically measured in kilograms and varies depending on the type of reactor and its design.
The critical mass is important because it determines whether a nuclear reaction can be self-sustaining. If the amount of 235U or 239Pu used is below the critical mass, the reaction will not continue and no energy will be produced.
The critical mass of 235U and 239Pu is calculated using mathematical models and simulations, taking into account factors such as the shape and composition of the reactor, the amount of neutron moderators and reflectors, and the presence of other isotopes.
Yes, the critical mass can be changed by altering the design and components of the reactor. For example, using more neutron moderators can decrease the critical mass, while using less can increase it. The critical mass can also be affected by the purity and enrichment level of the isotopes used.
If the critical mass is exceeded, an uncontrolled nuclear chain reaction can occur, leading to a nuclear meltdown and release of dangerous levels of radiation. This is why strict safety protocols and regulations are in place to prevent the critical mass from being exceeded in nuclear power plants.