Plutonium Isotopes in MOX Fuel

The health physics of MOX fuels is highly dependent on the plutonium content. Table 3.3 lists the key plutonium isotopes.

Table 3.3: Plutonium Isotopes in MOX Fuel

Isotope	Half-life (years)	Decay Mode	Spontaneous Fission Neutrons	Key Hazard
Pu-238	87.7	Alpha ( $\alpha$ )	Low	Self-heating — the alpha decay generates significant heat, causing storage problems
Pu-239	24,100	Alpha ( $\alpha$ )	Very low	Fissile — weapons-usable material; criticality and safeguards concern
Pu-240	6,560	Alpha ( $\alpha$ )	High	Significant neutron source from spontaneous fission
Pu-241	14.3	Beta ( $\beta^-$ )	Negligible	Decays to Am-241 which emits a 59.5 keV gamma ray — dose rate increases with time
Pu-242	375,000	Alpha ( $\alpha$ )	Moderate	Spontaneous fission neutron source

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