... From 10 to 10,000 years
Evolution over the period 2 to 10,000 years of radioactivity from spent PWR reactor fuel. This diagram compares the activity of fission products and actinides (plutonium and minor actinides) with that of activation products (cladding, package ends). Fission products are initially predominant, but are overtaken after around 200 years by plutonium and minor actinides, which decay more slowly. The decline in fission product activity tails off after 600 years, due to the presence of residual long-lived elements. Logarithmic scales (with powers of 10) must be used to represent the large changes in activity and time.