Sm
Samarium
Z = 62 · Lanthanide · 150.4 u
Nuclear Engineering Significance
Sm-149 is the second most important fission product poison after Xe-135 (σ_a = 40,140 b). Unlike xenon, Sm-149 is stable and accumulates permanently — it does not decay away after shutdown. Samarium poisoning must be accounted for in reactor restart calculations and long-term reactivity management.
Basic properties
- Atomic number (Z)
- 62
- Standard atomic mass
- 150.4 u
- Category
- Lanthanide
Isotopes & cross-section data
View in ALLEN →| Isotope | Mass (A) | Half-life | ZAID | Libraries | σ(E) |
|---|---|---|---|---|---|
| Sm-147 | 147 | 1.06e11 y | .80c.71c | View → | |
| Sm-149 | 149 | Stable | .80c.71c | View → | |
| Sm-150 | 150 | Stable | .80c.71c | View → | |
| Sm-151 | 151 | 88.8 y | .80c.71c | View → | |
| Sm-152 | 152 | Stable | .80c.71c | View → |