September 29, 1999
Past Recycled Uranium Programs Under Review as
The Department of Energy (DOE) has completed an initial stage of a technical review of past operations involving recycled uranium at gaseous diffusion plants located in Paducah, Kentucky; Oak Ridge, Tennessee; and Piketon, Ohio. The study of recycled uranium is being conducted in parallel with a two-phase investigation ordered by Secretary of Energy Bill Richardson into environment, safety and health concerns at the gaseous diffusion plants. The review of the gaseous diffusion plants provides updated information on the nature and extent of past activities involving the processing, conversion and enrichment of recycled uranium containing trace quantities of plutonium, as well as neptunium and technetium-99.
"We reviewed these sites first because of the nature of the work they conducted and a higher potential for worker exposure to contamination than other sites involved in uranium recycling operations," said David Michaels, Assistant Secretary for Environment, Safety and Health. "Today's information on material flow is intended to clarify and update what is known about past operations at the gaseous diffusion plants from the early 1950s. The numbers are preliminary, and as we validate and refine our results they could change, but I don't expect them to change significantly."
The technical review is part of a DOE-wide study of the flow of recycled uranium to determine where and how much processed recycled uranium was shipped as well as an assessment of the potential for worker radiation exposure. (The attached chart lists DOE sites currently identified as having a role in activities involving recycled uranium.) This information will enable the Energy Department to determine if more extensive reviews of personnel exposures or environmental contamination are required.
Activities involving recycled uranium use at the Paducah Gaseous Diffusion Plant are much better known than at other DOE sites because the issue of contaminants in the Paducah feed was reviewed during the 1980s. To gather information on uranium recycling activities at other sites, DOE has formed a department-wide working group and will task teams at the sites to gather data. The overall data collection is expected to be completed in March 2000, with a final consolidated department-wide report to be prepared by June 2000. The complex-wide review will also include depleted uranium hexafluoride storage cylinders as well as depleted uranium used in other applications.
To date, the department has identified 10 DOE sites in addition to the Paducah plant that processed recycled feed materials containing trace quantities of plutonium and other transuranics from the 1950s. The amounts of materials processed, the numbers of workers involved and the relative concentrations of contaminants varied widely between these sites and will be confirmed in the ongoing study. For example, current estimates show the Paducah plant processed the majority of these materials, with the Oak Ridge Gaseous Diffusion plant handling about a sixth as much and the Portsmouth plant in Ohio processing approximately 1% of the amount processed at Paducah. The Fernald facility in Ohio also processed amounts and concentrations comparable to those of the gaseous diffusion plants.
Chemical separation facilities that made uranium feed materials -- such as, Savannah River, Hanford, Idaho and West Valley -- and material processing sites that processed uranium oxide into metals or other forms in various amounts -- such as Weldon Spring -- are not believed to have the potential for worker exposures from processes that concentrated transuranics which are being examined at the gaseous diffusion plants.
Other DOE and military facilities have been identified on a preliminary basis as receiving uranium material for component fabrication and applications of a commercial or military nature. While the trace concentrations associated with this latter category of facilities are believed to be insignificant from a safety standpoint, as part of its ongoing investigation, DOE is working with the Defense Department, the Nuclear Regulatory Commission and other agencies to confirm amounts processed and concentrations involved.
At the Paducah uranium enrichment plant, recycled uranium was introduced into the enrichment "cascade" shortly after the startup of the plant in 1953 and continued through 1964. Activities were resumed in 1969 and continued through 1976. Paducah received approximately 100,000 tons (90,000 metric tons) of recycled uranium containing an estimated 328 grams of plutonium, 18.4 kilograms of neptunium and 661 kilograms of technetium-99. Operations at Paducah included the conversion of uranium oxide to uranium hexafluoride at a feed plant located onsite. The converted material was subsequently introduced into the gaseous diffusion "cascade" for further enrichment.
The average concentration of plutonium in recycled uranium at all three gaseous diffusion plants is estimated to be about four parts per billion. At both Paducah and Oak Ridge sites, the majority of the plutonium and neptunium was separated out as waste during the initial chemical conversion to uranium hexafluoride. Because of this, only a fraction of the plutonium contamination was actually introduced to the gaseous diffusion cascade at either plant. This waste was subsequently reprocessed to recover additional uranium and then reused.
Of the 328 grams of plutonium present in the 100,000 tons of recycled uranium processed at the Paducah plant, only 0.1 gram of plutonium is estimated to have been introduced into the Paducah cascade. Transuranics including plutonium are believed to have been deposited on internal surfaces of the feed process equipment, with concentrations also being deposited in waste products.
Processing of recycled uranium at the Oak Ridge Gaseous Diffusion Plant began in the early 1950s with the first shipments of recycled uranium oxide from Hanford. A uranium hexafluoride feed plant was operated at Oak Ridge from 1952 until 1961. Recycled uranium was fed to the Oak Ridge enrichment cascade from 1958 to 1962, from 1970 to 1974 and from 1976 to 1977.
The Oak Ridge Plant received approximately 17,800 tons (16,238 metric tons) of recycled uranium. DOE officials believe that the majority of this recycled uranium went through the process of conversion from uranium oxide to uranium hexafluoride. A small fraction of this material was of foreign or commercial origin. Of the recycled uranium received, it is known that approximately 5,800 tons of this amount were fed into the Oak Ridge enrichment cascade. The majority of the remaining 12,200 tons of recycled uranium is assumed to have been enriched at Paducah.
Of the 17,800 tons of recycled uranium received at Oak Ridge and converted to uranium hexafluoride, DOE estimates that the material could have originally contained up to 60 grams of plutonium, 3.5 kilograms of neptunium and 103 kilograms of technetium-99. An additional 121 kilograms of technetium-99 was received from enriched uranium initially processed at Paducah and further enriched in the Oak Ridge plant.
It is currently estimated that the Portsmouth Plant processed a relatively small quantity of recycled uranium as compared to Paducah and Oak Ridge plants. Up to 1,320 tons (1,200 metric tons) of this material entered the enrichment cascade at Portsmouth. Most of this material, 1,210 tons (1,100 metric tons), was received as uranium hexafluoride from Oak Ridge and Paducah sites. The remaining material came from a variety of facilities in the DOE complex.
At the Portsmouth site, the oxide conversion facility processed recycled uranium from 1958 to 1977. Recycled uranium was fed to the Portsmouth cascade from 1955 to 1958 and in 1961, 1969 and 1974. No estimates are currently available for the amount of plutonium or neptunium present in the uranium recycled materials at Portsmouth. However, based on the amount of recycled uranium received, the amount would likely have been small. The Portsmouth plant received approximately 85 kilograms of technetium-99 primarily from uranium previously enriched at Paducah and refed into the Portsmouth cascade.
DOE officials briefed regulators from Kentucky, Tennessee and Ohio on the review as part of a regular meeting to discuss a number of DOE-related issues. The meeting was held today in Lexington, Kentucky.
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