Because of the fission process that consumes the fuels, the old fuel rods must be changed periodically to fresh ones (this period is called a cycle). However, only a part of the assemblies (typically one-third) are removed since the fuel depletion is not spatially uniform.
In fertilization, the sperm and egg both contain one set of chromosomes. the father (sperm) and one from the mother (egg). In SCNT, the egg cell's single set of chromosomes is removed. chromosomes. come from the somatic cell.
The goal is not to create cloned human beings (called reproductive cloning), but rather to harvest stem cells that can be used to study human development and to potentially treat disease. While a clonal human blastocyst has been created, stem cell lines are yet to be isolated from a clonal source.