A factory producing plutonium for nuclear weapons in Hanford, Wash., emitted enough radioactive particles in the mid-1940s to pose a potentially serious risk to any nearby infants, according to experts familiar with a federally financed scientific report expected to be released today.

Secretary of Energy James D. Watkins, jumping the gun on a news conference scheduled in nearby Richland, said yesterday that the report is expected to "contain estimates of potentially large doses" of radioactivity from airborne emissions at the Hanford plant from 1944 to 1947, a period when the hazards of radiation were poorly understood.

Watkins said the volume of radioactive material released during a single episode at Hanford in 1945 was equivalent to 1,000 or more kilos, or 2,200 pounds, and that the total radioactivity of that release was roughly 350,000 to 400,000 curies. A curie is the amount of radiation emitted in one second by 1,400 pounds of enriched uranium.

"The implications of the report are serious," Watkins said, evidently basing his remarks on a telephone conversation this week with John Till, director of the special government-sponsored independent effort to reconstruct the likely radiation doses to nearby residents from surviving records of the plant's operation at the onset of the Cold War.

Watkins said Till's report would estimate that some residents had been exposed over this period to as much as 3,000 rad. A rad is a measure of absorbed radiation dosage. To put that exposure in context, facilities licensed by the U.S. Nuclear Regulatory Commission are required to limit workers' yearly radiation exposure of the type that occurred at Hanford to the equivalent of 15 thousandths of a rad.

Watkins's statement appears to be the first acknowledgement by a senior government official that civilians may have suffered harm from radiation emissions at Hanford.

The principal source of worrisome exposure was radioiodine, Watkins told reporters in Washington. That is the same isotope that caused radiation sickness and thyroid deficiencies in some residents of the Soviet Union because of accidental emissions during the 1986 fire at a commercial nuclear power plant at Chernobyl.

An official familiar with the contents of the new report confirmed that Watkins's estimate is correct for a small portion of Hanford-area residents, noting that the actual doses are subject to some uncertainty. The estimate is close to that predicted by a preliminary 1986 survey by Washington state health officials.

Watkins called the dosage estimates to be released today "high," but said "we don't know who was at the right spot at the wrong time." He added, "we're primarily interested, of course, in the infants," who would be substantially more vulnerable than adults to such radiation.

The report represents only a piece of a larger, continuing effort aimed at determining how many people were affected by the Hanford emissions, and perhaps to identify them. Similar federally financed studies of radiation exposure are being conducted at other facilities.

The existence of the Hanford emissions has been known for many years, although it was kept from nearby residents at the time, according to government records recently unearthed by Senate investigators.