Historical clue formulations

• Plant energy source — 2025-04-12
• Element of heavy metal — 2022-01-29
• Stockpile that may be subject to inspection — 2019-04-13
• Radioactive element — 2017-04-17
• Constituent of pitchblende — 2001-04-20
• Pitchblende ingredient — 1995-01-08