Radioactive Waste Found Beyond Rockwell Lab : Contamination: Consultant says amounts northwest of Chatsworth appear to pose no immediate health hazard. But activists contend the findings are flawed.

Small amounts of radioactive material have spread beyond the boundaries of Rockwell International’s Santa Susana Field Laboratory northwest of Chatsworth, but the material appears to pose no immediate health hazard, according to the results of a yearlong study released Wednesday.

Rockwell officials hailed the report as confirmation that the company has not endangered the surrounding community. But environmental activists charged that the study, prepared by a consultant hired by Rockwell, was flawed.

They called for an independent study to find the source of the hazardous waste that has migrated beyond the Rockwell lab, where nuclear research and rocket tests were conducted during the past four decades.

Nuclear research at the site was halted in 1989 in the wake of protests by neighbors and environmental activists and Rockwell is now engaged in a $40-million cleanup of contaminated soil, ground water and buildings on its property.

The latest tests found that some soil and water near the Rockwell land were polluted by tritium, a radioactive form of hydrogen, which almost certainly originated at the Rockwell site. The tests also turned up small amounts of radioactive strontium-90, cesium-137 and plutonium-238 outside the lab, but researchers said a search for the source of this contamination was “inconclusive.”

The study results, announced at a public meeting organized by the U.S. Environmental Protection Agency, focused on tests of soil and water at the Brandeis-Bardin Institute, a center for Jewish studies in Simi Valley, and on Santa Monica Mountains Conservancy land.

Both test sites are adjacent to the Santa Susana lab, operated by Rockwell’s Rocketdyne division on 2,600 acres in Ventura County, between Chatsworth and Simi Valley.

Arnold Robbins, an EPA official, said additional testing should be done, but he called the initial results “generally encouraging.”

“There’s nothing telling us there’s an immediate health threat here,” he said.

Last month, federal officials selected a UCLA research team to conduct an 18-month study to determine whether Santa Susana lab workers who were exposed to toxic and radioactive materials had experienced any unusual patterns of illness.

Initially, the company contended that its research work had no impact on ground water outside the Rocketdyne site. But in 1991, well samples on the Brandeis-Bardin property were found to contain low-level radioactive pollution. Brandeis-Bardin officials said that did not pose a health risk because the well water was not used for drinking.

The test results released Wednesday stemmed from additional sampling on Brandeis-Bardin land and Santa Monica Mountains Conservancy land last spring.

At the meeting, Helen Zukin, an attorney for Brandeis-Bardin, said of the test results: “We’re concerned. This is further confirmation that there has been some off-site migration. Clearly, Rocketdyne activities have impacted Brandeis-Bardin’s property.”