32 Ill. Adm. Code 351.490
Uranium Sinker Bars
Section 351.490 Uranium Sinker Bars
A licensee or registrant may use a uranium sinker bar in
well logging applications only if it is legibly impressed with the words
"CAUTION--RADIOACTIVE--DEPLETED URANIUM" and "NOTIFY CIVIL
AUTHORITIES (or COMPANY NAME) IF FOUND."