Workers next month will begin a $1.2-million cleanup of radioactive sludge from a UC Davis research program that killed more than 1,000 beagles. A special task force has checked for hot spots in abandoned research buildings adjacent to the landfill where 35,000 gallons of sludge were buried. Officials hope to avoid having a part of the 6,000-acre campus labeled as one of the nation's dangerous toxic sites. The sludge comes from the dogs' waste and was a byproduct of a 33-year study of the long-range health effects of exposure to low-level radioactivity. The research, started in 1956, involved feeding most of the beagles meat contaminated with radioactive strontium 90, which appears in fallout from nuclear weapons tests or nuclear plant accidents. Some dogs were radiated with cobalt 60.