Assertion: cerium's isotope | /r/HasProperty | half-life
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Source sentences:
text: The 169Yb isotope (with a half-life of 32 days), which is created along with the short-lived 175Yb isotope (half-life 4.2 days) by neutron activation during the irradiation of ytterbium in nuclear reactors, has been used as a radiation source in portable X-ray machines.