Managers of the government's Paducah, Ky., uranium plant knew for decades of unusual radiation hazards inside the complex but failed to warn workers because of fears of a public outcry, according to documents to be released by a congressional panel this week.

Faded memos unearthed by workers and federal investigators shed new light on what early plant officials knew about the presence of plutonium and other highly radioactive metals in the plant -- knowledge that was kept from the workers for nearly four decades.

In one 1960 document, a government physician wrote that hundreds of workers should be screened for exposure to "transuranics" -- radioactive metals such as plutonium and neptunium -- but he said plant officials feared such a move would cause alarm and lead to higher labor costs.

"They hesitate to proceed to intensive studies because of the union's use of this for hazard pay," says the memo, discovered by Energy Department officials investigating the plant.

The documents from government archives have been turned over to a House Commerce Committee panel, which is holding hearings Wednesday into allegations of unsafe conditions at the Paducah Gaseous Diffusion Plant. The Washington Post obtained advance copies of the documents and prepared testimony of some current and former plant officials.

Accounts of plutonium contamination and illegal waste dumping at the facility have triggered an Energy Department investigation and a class action suit by employees who believe the plant put them at risk.

Energy Secretary Bill Richardson toured the plant on Friday and formally apologized to workers for the government's failure to fully inform them about the risks. He pledged millions of dollars in new spending to compensate ailing workers and to accelerate the cleanup of the plant. And he presented an award to the family of the late Joe Harding, an employee who had tried vainly for years to convince Energy officials that hazards in the plant had caused his fatal illness.

"On behalf of the government I'm here to say I'm sorry," Richardson said. "The men and women who have worked in this facility helped the United States win the Cold War and now help us keep the peace. We recognize and won't forget our obligation to them."

Plant officials, while acknowledging the presence of plutonium at Paducah, have said the amounts were small and were likely of little threat to workers.

Government contractors who ran the plant over the last 47 years have declined to comment because of pending litigation. A Union Carbide Corp. spokesman, in a statement last month, said the alleged acts at Paducah occurred long ago, and none of the current managers had any detailed knowledge of what had happened. Union Carbide operated the plant from 1952 to 1983.

The documents and testimony to be presented at the congressional hearing suggest that the federal government and private contractors running the plant ignored decades of warnings to protect workers from plutonium, a man-made metal that can cause cancer if inhaled in amounts as small as a millionth of an ounce.

"What is clear is that the [government] contractors knew of the need to protect workers from plutonium and other transuranics . . . as early as 1952," Jim H. Key, the ranking environmental and safety official for the plant's unionized employees, states in prepared testimony to be delivered Wednesday.

Key, who has not yet spoken publicly about the allegations of workers' exposure, alleges "widespread, systematic and documented failures" by the government and its contractors to control the spread of radioactive hazards. He describes smoky, radioactive fires inside the plant and thick clouds of radioactive uranium dust -- workplace hazards for which workers were neither trained nor equipped.

Former workers also have come forward with evidence suggesting that past managers viewed the contamination as a practical and economic problem. John Tillson, a hydrologist who analyzed early operations at the plant while working for a cleanup contractor, said Paducah managers tried to recover the transuranics from the plant's waste stream in the 1950s and 1960s, when the metals were in high demand for nuclear materials research.

By 1970 the prices had dropped, and the recovery programs were halted, he said.

Plant officials even began processing sewage sludge from the plant after it was found to contain high levels of uranium. Harold Hargan, a 37-year employee who was detailed to the recovery program, said the uranium in sludge came exclusively from the plant's sanitary system, which included lavatories, wash rooms and laundry facilities. "All that uranium was either on workers' clothes or bodies -- or inside their bodies," he said.

Although no formal epidemiological study has been completed for Paducah, some workers have long raised questions about what they believe are unusual rates and types of cancers in their communities. Those fears have risen sharply in the wake of reports that plutonium and other highly radioactive metals were also present in the workplace, Key, the union safety officer, says in his statement.

"The majority of current and former workers are afraid that they may have been exposed to substances like plutonium without proper protection and that they will, as a result, be stricken with a fatal disease," Key wrote. "I myself have this fear from my 25 years at Paducah."

Hired by the plant's original contractor, Union Carbide, in 1974, Key said he began witnessing safety problems almost immediately. During his first year on the job, he was engulfed in radioactive smoke after helping dump drumloads of highly flammable uranium metal into an open pit on the plant's grounds.

"The uranium spontaneously ignited . . . and a pungent and irritating smoke enveloped us," said Key, an hourly worker and officer in the local chapter of the Paper, Allied-Industrial, Chemical and Energy Workers International Union. "To my knowledge this dumping ground has never been characterized."

Workers inside the building where powdered uranium was processed were not required to wear respirators, even though the dust at times was so thick it was difficult to see, Key said.

"I recall having to hold my breath to get through clouds of unknown fumes," he said.

In the 1970s, Key would observe workers cleaning up spills of "black powder," which he later learned consisted of recycled uranium from the government's plutonium production facilities. Not until 1990 did plant officials tell the union that the powder contained small amounts of "transuranics" -- a class of highly radioactive metals that includes neptunium and plutonium. Plutonium is 100,000 times more radioactive per gram than uranium.

Key cited a 1952 Union Carbide memo that suggests the need for special labeling of "plutonium contaminated locations."

Years later, in a 1985 memo, Energy officials advised Paducah's managers to test workers who handled the recycled uranium for exposure to transuranics. Key notes, "We have no evidence that these recommendations were acted upon or communicated to the workforce."

In 1991, Martin Marietta Energy Systems, which was now operating the plant, began a voluntary program to test workers for exposure. Thirty workers participated, but the test results were "invalidated" due to what the company termed "concerns and discrepancies" regarding the testing lab, Key said.

He said the company refused to release the results to the union, explaining in a memo that "management is reluctant to release this information due to concerns about how it would be used."

Concerns about public reaction were echoed in the 1960 memo from H .D. Bruner, a physician, to Union Carbide and Atomic Energy Commission medical officials. He expressed concerns about relatively large amounts of neptunium in recycled uranium delivered to the Paducah plant. "But I am afraid the policy of the plant is to be wary of the unions and any unfavorable public relations," the memo states.

Although workers in some buildings were furnished with gas masks, Bruner said the respirators were not used and did not appear to be effective against the tiny uranium particles in the air.

"The human factor in handling [the recycled material] should be considered a source of potential exposure," he wrote.