A Montgomery County cobalt-processing plant that was investigated by the Maryland Department of Health and Mental Hygiene after a radioactive hot spot was discovered near the plant 14 months ago has been declared a "reasonably safe" operation, state officials said yesterday.

The investigation was initiated after a speck of cobalt-60 was found on a railroad track in November 1980 less than 100 yards from the Dickerson headquarters of Neutron Products Inc., which makes cobalt power cells used to treat cancer patients and to sterilize medical instruments.

After a year-long evaluation of the plant and the company's general operation, investigators -- who never determined where the initial hot spot came from -- have concluded that no major safety hazards exist.

"We found that the company is using licensed material in a reasonably safe manner," said Richard Brisson, a state public health radiation specialist. "We could find no significant health and safety problems. We are comfortable that they have adequate controls over radioactive materials, but there are no guarantees of absolute safety."

Jackson Ransohoff, president of Neutron Products, the second largest company of its kind in the country with sales last year of $3 million,, said he was very happy with the findings of the investigation, which was based on the guidelines of the federal Nuclear Regulatory Commission.

"Our goal has always been to maintain a safe operation," Ransohoff said. "I believe the commission was fair in its findings. And I agree there is no such thing as absolute safety at a plant like ours."

Ransohoff said his company agreed to stop the melting of cobalt at his plant from July until November while officials considered whether to extend the firm's license to continue operations. He said the company, which is now free to resume its application for a new license, continued normal operations by drawing on its reserves of processed cobalt-60.

Brisson said the company has been required to make a series of safety improvements and that its operation will be monitored frequently.