Enough weapons-grade uranium to make almost 20 atomic bombs is from a factory in Apollo, Pa., that makes nuclear fuel for atomic-powered submarines.

In the 18 years since it began producing nuclear submarine fuel, the factory at Apollo, which is today owned and operated by the Nuclear Materials Division of Babcock & Wilcox Co., has "lost" through faculty accounting and handling procedures more than 280 pounds of uranium enriched with 90 per cent of the isotope known as U-235. Though the uranium would have been used to make fuel for atomic submarines and surface ships, it is identical to the uranium used to make bombs.

The figures of missing uranium are in an internal document put together almost two years ago by the staff of the Nuclear Regulatory Commission and leaked to the press yesterday by sources on Capitol Hill. NRC sources emphasized that none of the missing unranium is believed to have been stolen by terrorists or countries wanting to make weapons.

"We think that all the missing uranium was lost through leaky pipes, sloppy accounting methods and bad scrap and recycling procedures," an NRC source said yesterday. "We do not think any uranium was diverted out of the plant for weapons purposes."

The lost-uranium situation was discovered as a result of eight inspections done at the Apollo plant by the staff of the Nuclear Regulatory Commission and the now extinct Atomic Energy Commission dating back to 1963. The most recent loss was found a year ago and is not covered on the document leaked yesterday.

While the figure of 280 pounds of uranium stands out as missing in the leaked document, the total uranium missing at Apollo is understood to be more than that. The presice total of lost uranium is a secret.

Also a secret is the amount of weapons-grade uranium that moves through the Apollo plant every year and out to factories at Lynchburg, Va. and Uncasville, Conn., where nuclear submarine power plants go through the final stages of fabrication.

The leaked document reveals scores of rule violations at the Apollo plant, which is a converted warehouse that has been operated by three different owners over its 18-year lifetime. The company started out as an independent concern called NUMEC, was bought in 1970 by Altantic-Richfield Corp. and in 1971 by Babcock & Wilcox.

NRC sources said that much of the missing uranium was lost because the Apollo plant did not separate weapons-grade uranium from civilian in the scrap and recycling process. A makeshift wall divided the assembly lines at Apollo that fabricated submarine fuel parts and civilian power plant parts, which use completely different kinds of enriched uranium.

The largest single loss of weapons-grade uranium took place in 1967, and originally involved almost 200 pounds of uranium. That was scaled down to 150 pounds when 50 pounds was exhumed from a nearby burial site where scrap metal was stored. This loss had been reported by The Washington Post almost four years ago.

None of the other losses, involving about 130 pounds of uranium, had been previously reported. Most were in amounts as small as five pounds; one loss showed 50 pounds. A few of the losses invloved leaks of gaseous and liquid uranium compounds that exposed some of the 400 workers at the Apollo factory to high levels of radioactivity.

"There appears to have been seven cases of exposure of individuals to excessive airborne concentrations of U-235 in restricted areas," the document states. "Reported were not furnished to six individuals notifying them that they had been exposed to radiaactive material in excess of that permitted by regulation."

The document points out that the Apollo factory's sewer system was such that it repeatedly leaked excessive amounts of uranium into the Kiskiminetas River near the plant. The document did not go into details of how much radioactivity was leaked into the river.