Kostenloser Radioactive Decay Rechner
Berechnen Sie remaining radioactive activity after a given time. Track decay through multiple half-lives for any isotope.
Remaining Activity
125,000 Bq
Remaining Activity vs Elapsed Time
Formel
## 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.
Lösungsbeispiel
I-131 (t½ = 8 days) with initial activity 1 MBq after 24 days.
- 01Half-lives elapsed = 24 / 8 = 3.0
- 02Fraction remaining = (1/2)³ = 0.125 = 12.5%
- 03A(24) = 1,000,000 × 0.125 = 125,000 Bq
Häufig Gestellte Fragen
What are common half-lives for medical isotopes?
Tc-99m: 6 hours, I-131: 8 days, F-18: 110 minutes, Co-60: 5.27 years, Cs-137: 30 years. Short half-lives are preferred for diagnostic imaging; longer ones for therapy.
How long until a sample is "safe"?
A common guideline is 10 half-lives (0.1% remaining). For I-131: 80 days. However, safety depends on the initial activity and the specific regulatory limits for the isotope.
Can decay be accelerated?
No. Radioactive decay is a nuclear process unaffected by chemical reactions, temperature, pressure, or any other external conditions. The half-life is an intrinsic property of the isotope.
Lernen