A nuclear-powered surface gauge used for soil testing could prove dangerous if whoever stole it tinkers with it and opens it up, Manteca Police warned Tuesday. The “Nuclear Densometer,” valued between $10,000 and $15,000, was taken in a theft from the bed of a pickup truck parked in the 800 block of Nevada Street between 6 p.m. Monday and 6 a.m. Tuesday. It is said to be radioactive.