Kalman Shure of Shadyside, a pioneer in nuclear reactor shielding who helped design the nuclear submarine Nautilus, died Thursday of complications from a series of strokes. He was 80.

A Brooklyn, N.Y., native, Dr. Shure earned his doctorate in physics at the Massachusetts Institute of Technology in 1951 and promptly began what would be a 43-year career at the Bettis Atomic Power Laboratory, the government-owned lab in West Mifflin that develops naval nuclear propulsion technology.

He thus became involved in the design of the first nuclear submarine, the Nautilus, and went on to develop many of the design methods and standards for nuclear shielding -- both for the naval nuclear program and for other nuclear applications.

"His legacy went way beyond Bettis," said I.K. Abu-Shumays of San Diego, Calif., who worked with Dr. Shure at the lab from 1974 through his retirement in 1994. He was active with the American Nuclear Society's radiation protection and shielding division, helping to set standards and design methods used not only in nuclear propulsion, but in civilian nuclear power plants and in hospital radiology departments.

"He was respected internationally," Abu-Shumays said.

That reputation even helped open doors in Japan for a colleague, Henry Stone, who was trying to sell General Electric reactors. Stone was getting the brushoff from a Japanese official when he spotted on the official's desk a copy of the Reactor Shielding Design Manual, a basic text he had co-authored with Dr. Shure.

When he pointed to his name on the cover, right under Dr. Shure's, the official suddenly opened up. "Perhaps then we should talk," he told Stone.

Despite Dr. Shure's fame within the nuclear community, the strict government secrecy regarding nuclear technology kept him close-mouthed outside of the lab. That was particularly frustrating in the early 1950s for his new wife, Minna, who he met while both were in graduate school in Cambridge, Mass.

"I had nothing to talk to this man about," she recalled. One day, she tried talking to him about a nuclear energy story she had read in the newspaper. He became agitated and told her to stop talking. Apparently, the news included information that shouldn't have been released and he immediately called his superiors to report it.

You couldn't be too careful during the red-hunting McCarthy era, Minna Shure explained. Her husband urged her to be careful even about making jokes, noting an employee at Oak Ridge National Laboratory was fired after his wife joked that they subscribed to the "Daily Worker." And so she kept her mouth shut. "I didn't want my husband to be unemployed."

Keeping quiet came naturally to Dr. Shure, who was slow to speak up in groups. "I asked him how come he didn't speak up more," Minna Shure recalled. "He said, 'All those talkers need a listener.' "

But when he did have something to say, he wasn't shy about it. According to Bettis lore, Dr. Shure once won an argument with the strong-willed Adm. Hyman Rickover, known as the Father of the Nuclear Navy. "If Kal says this is the way it's done, you better listen," colleagues would later joke. "Even the Admiral does."

"He led by example," not with words, recalled a former colleague, still so concerned about classification that he asked not to be identified by name. "He could be very forceful, setting high standards. He wasn't going to tolerate any shortcuts."

Such exacting standards were essential for nuclear submarines, where shielding has to be sufficient to protect sailors only a few feet away from the reactor, yet not so massive as to harm the sub's performance.

Dr. Shure's design principles were so effective, this former colleague noted, that "sailors are working within feet of a nuclear reactor and they actually receive a lesser [radiation] dose than you or I."

In addition to his wife, Dr. Shure is survived by two daughters, Dr. Mavis Shure of Phoenix, Ariz., and Loren Shure of Boston, Mass.; and a brother, Henry Shure of Palm Desert, Calif.

Services will be at 3 p.m. today at Ralph Schugar Chapel, Shadyside, with visitation for one hour prior to the service. Interment will be at Temple Sinai Memorial Park.

Gifts may be made to MIT, 77 Massachusetts Ave., Cambridge, MA 02139-4307 or to Temple Sinai, 5505 Forbes Ave., Pittsburgh 15217.