中子通量计算器 — 公式
## Radioactive Decay Law
Radioactive decay follows first-order kinetics. The activity (and number of atoms) decreases exponentially with time.
### Formula
**A(t) = A0 × e^(-lambda × t) = A0 × (1/2)^(t/t½)**
where lambda = ln(2)/t½ is the decay constant. After one half-life, 50% remains. After two, 25%. After ten, only 0.098% remains.
Radioactive decay follows first-order kinetics. The activity (and number of atoms) decreases exponentially with time.
### Formula
**A(t) = A0 × e^(-lambda × t) = A0 × (1/2)^(t/t½)**
where lambda = ln(2)/t½ is the decay constant. After one half-life, 50% remains. After two, 25%. After ten, only 0.098% remains.
计算示例
I-131 (t½ = 8 days) with initial activity 1 MBq after 24 days.
- Half-lives elapsed = 24 / 8 = 3.0
- Fraction remaining = (1/2)³ = 0.125 = 12.5%
- A(24) = 1,000,000 × 0.125 = 125,000 Bq