劣化ウラン
All uranium compounds are radioactive. However, uranium is usually in depleted form, except in the context of the nuclear industry. Depleted uranium consists mainly of 238U which decays by alpha decay with a half-life of . Even if the uranium contained 235U which decays with a similar half-life of about , both of them would still be regarded as weak alpha emitters and their radioactivity is only hazardous with direct contact or ingestion.