OAK RIDGE, Tenn. - Dr. Karl Z. Morgan, a founder of the field of health physics, the science of human health and radiation exposure, died June 8 after years as a top official at the national laboratory here. He was 91.

Morgan was a member of the metallurgical laboratory staff at the University of Chicago in 1943 when Enrico Fermi and other physicists in the Manhattan Project were developing the world's first atomic bomb there. Morgan was sent to a secret location in Tennessee where uranium was processed for the bombs that were dropped two years later on Hiroshima and Nagasaki Japan.

After the war he remained for 29 years at the plant, which became the Oak Ridge National Laboratory, and was director of health physics at the plant until his retirement.

Morgan founded the Health Physics Society and was its first president, from 1955 to 1957. He also founded the Journal of the Health Physics Society and was its first editor, serving until 1977.

In an article in the June issue of the journal, Morgan was described as "one of a group of six persons who developed and established the new science known as health physics, which today employs thousands of persons in countries throughout the world."

At mid century, Morgan was a proponent of the view then prevailing that with nuclear science and technology a new golden age has come for humanity. "We believe that the nuclear age is here to stay and that its future rests in large measure on the successful control of radiation exposure," he wrote in an editorial in the first issue of Health Physics.

"We must understand the full and ultimate consequences of this exposure and limit it at a level where we, and those that come after us, can reap the maximum benefits of this new age."

For decades Dr. Morgan was considered a pillar of the nuclear establishment. However, his critical activities have also become widely known. Morgan was influential in the campaign for a 1968 federal law that regulated medical X-rays, and campaigned with much energy against the use of x-ray machines in shoe stores. This campaign against much resistance finally lead to a new federal law saing that such machines have to be run by radiologists exclusively. Morgan was invited to the White House to witness the signing of the new law by president Johnson.

Morgan also offered court testimony friendly to people who said they had been harmed by nuclear weapons and the nuclear power industry. All these activities were to the dismay of others in nuclear establishment.

In October 1982, he testified in a lawsuit brought by nearly 1,200 people who accused the federal government of negligence in atomic weapons testing in Nevada in the 1950s, which they said had caused leukemia and other cancers. Morgan, then 75, testified that radiation protection measures in the tests were substandard and "not in the spirit" of what was known at the time about the health hazards of radiation.

He said that the Atomic Energy Commission, the forerunner of the Nuclear Regulatory Commission, had set radiation safeguards and other standards by selectively using information that would support conclusions that had already been reached.

Morgan also testified in behalf of Navajo uranium miners and their survivors, saying federal officials had known about mine radiation dangers but had failed to protect the miners. And he testified in the case of Karen Silkwood against Kerr-McGee. Silkwood was a laboratory technician who reported health and safety violations before being killed in a car crash as she was on the way to meet with a reporter from The New York Times about her accusations.

For many years Morgan was a member of the Internal Commission on Radiation Protection (ICRP). He has repeatedly criticized the actions and recommendations of the ICRP for being in favor of nuclear industry. He also criticized the ICRP´s incestuous way of reelecting its members.

I met Karl Morgan several times at international meetings of concerned scientists.

His thoughtful, distinguished and engaged manner of reporting and discussing and his courageous activities for the improvement of radiation protection made a lasting impression on me- I will never forget what he said about the ICRP as résumé: Although the ICRP has been very useful in the past it has never dared to oppose the interests of the nuclear establishment. I am not sure whether I would put my health and life into the hands of such an organization."

His autobiography, "The Angry Genie: One Man's Walk Through the Nuclear Age," written with Ken M. Peterson, a trial lawyer, was published earlier this year by the University of Oklahoma Press.