5×104Sm

5×104Sm refers to a specific isotope of samarium, denoted as samarium-149. The notation indicates that the element samarium (Sm) has an atomic mass number of 149. The number 5 is likely a typo or misinterpretation as it is not a standard part of isotope notation. Samarium is a rare earth element with the chemical symbol Sm and atomic number 62. Isotopes of an element have the same number of protons but different numbers of neutrons.

Samarium-149 (149Sm) is a stable isotope, meaning it does not undergo radioactive decay. It is one of the naturally occurring isotopes of samarium. Its abundance in natural samarium is approximately 13.8%. Samarium-149 has 62 protons and 87 neutrons in its nucleus. It plays a significant role in nuclear reactors as a neutron absorber. Specifically, it is a strong neutron poison due to its large neutron capture cross-section. This property makes it useful for controlling the nuclear chain reaction in certain reactor designs. Over time, samarium-149 can accumulate in nuclear fuel, affecting reactor physics and fuel burnup calculations.