U.S. Department of Energy, Office of the Press Secretary, Washington, DC 20585
The Department of Energy has declassified the total amount of highly enriched uranium inventory at the Rocky Flats Plant near Denver, Colorado. Highly enriched uranium is defined as uranium having an enrichment above 20 percent of the fissionable isotope uranium-235.
Most of the material is stored as metal and weapons components with the rest in other forms.
U.S. Department of Energy
Office of Public Affairs
Contact: Sam Grizzle
U.S. Department of Energy, Office of the Press Secretary, Washington, DC 20585
Q. How safe is the storage of highly enriched uranium at Rocky Flats?
A. Onsite reviews indicate that the storage of highly enriched uranium is safe. Highly enriched uranium has been safely stored at the Rocky Flats Plant throughout its operating history, as well as during the recent termination of operations period. This material is present in various solid and solution forms. The storage requirements for this material address specific concerns with its radiological and toxicological hazards. Storage standards for this material require that it be stored in controlled environments subject to routine surveillance to ensure safety requirements are met. A unique concern with this material is its fissile nature and the possibility of a nuclear criticality accident. Very rigorous controls, including passive and active engineering design features as well as administrative controls, are applied in the storage of this material. These measures preclude any credible series of events leading to a criticality. The double contingency principle is applied to ensure that two very unlikely independent events would have to occur for a criticality to be possible. Thus, the overall likelihood of a criticality event from storage of this material is extremely unlikely.
Q. Does the storage or release of uranium, including depleted uranium and other materials and chemicals from the operations at the Rocky Flats Plant represent a health hazard to the workers or the public?
A. The Department of Energy is addressing the question of health effects from exposure to uranium, both depleted and enriched, by sponsoring a comprehensive package of health studies of Rocky Flats Plant workers and community residents.
A program for surveillance of illness among Rocky Flats workers that systematically collects illness and injury data from employee absence reports began in 1991. This program will identify patterns of illness and injury so that specific workplace exposures can be better monitored and controlled.
At Rocky Flats, the Department of Energy has initiated a comprehensive medical surveillance program that includes three major components. A medical surveillance program to monitor all workers for possible early indicators of disease, a beryllium program to test workers exposed to beryllium and a program to monitor former workers whose lifetime total effective dose equivalent exposure is calculated to exceed 40 rem. From 1984 through 1987, three cases of chronic beryllium disease were diagnosed among workers who had symptoms of lung disease. About 1000 current employees participated in 1987-1991 studies of chronic beryllium disease conducted by the National Jewish Center for Immunology and Respiratory Medicine. The studies demonstrated the effectiveness of the blood lymphocyte proliferation test in finding early cases of the disease. Twenty-one cases of chronic beryllium disease were eventually diagnosed. In June 1991, the Department of Energy initiated a surveillance program that offered the blood test to current and former employees.
Over 4000 additional individuals have been provided the blood test, 75 have had abnormal results, 21 have been diagnosed as having chronic beryllium disease, 8 do not have the disease, and 46 are in progress or scheduled to receive diagnostic medical examinations. (A total of 44 cases of chronic beryllium disease have been diagnosed from 1984 to the present.)
In 1980 the Rocky Flats Plant initiated a medical recall program for former employees who were receiving doses greater than 0.5 rem per year from internally deposited radionuclides (plutonium, americium, and uranium). In 1992, about 340 former employees were eligible for the program. The Office of Health began funding the program in July 1992. The criteria for inclusion changed to 40 rem lifetime total effective dose equivalent exposure to both internal and external radiation. Dose recalculations are not complete, but it is expected that between 500 and 700 former employees will be eligible for the program. Since July 1992, 332 individuals have been provided medical examinations which include bioassay tests and body counting to provide better estimates of lifetime dose. A complete health history is collected on each participant. The health experiences of this group are given to the principal investigator of the National Institute of Occupational Safety and Health managed epidemiologic studies at the Rocky Flats Plant to help form hypotheses for epidemiologic analyses.
The Rocky Flats Plant operates a medical monitoring program for current employees that provides over 5000 work related medical examinations per year. Fifteen hundred and seventy-three employees are currently enrolled in the medical monitoring program for radiation workers. Thirty current employees are monitored because of internal depositions of radionuclides resulting in annual doses greater than 0.5 rem. Three hundred and twenty-seven employees are medically monitored for exposure to chemical carcinogens, primarily asbestos. Four hundred and twenty-four are hazardous waste workers. Information on recordable occupational injuries and illnesses and nonoccupational injuries and illnesses that result in 5 or more days away from work are analyzed to detect higher than expected rates or negative trends.
At the Rocky Flat Plant during calendar year 1993, there were 2,566 employees that were monitored for plutonium and 470 who were monitored for uranium by their routine bioassay monitoring program. Among those monitored there was one individual with a positive bioassay. That individual had received an uptake of uranium in 1989 with a dose determined to be 83,500 mrem committed effected dose equivalent (the dose from an uptake that is delivered to an individual over a 50-year period). No positive internal doses were noted for uranium during calendar year 1993. From other work place indicators, it was also determined that 10 individuals had positive doses for plutonium that ranged from 1-380 mrem committed effective dose equivalent. There was no potential for tritium (H-3) dose for any individual.
The Department of Energy has conducted several epidemiologic studies of workers at the Rocky Flats Plant. A preliminary study of 452 deaths indicated a statistically significant excess of deaths due to benign and unspecified brain tumors that were not associated among workers with exposure to plutonium. This finding led to a special study of 16 deaths due to primary brain tumors among white males employed anytime from 1952 through 1977 that was published in 1984. The study did not demonstrate statistically significant associations between tumor deaths and exposure to internally deposited plutonium, external radiation, or other occupational risk factors. The same conclusions were reached when looking only at deaths due to brain tumors of the glioma cell type or when considering the time between first exposure to plutonium and external radiation and death.
The first major study of 5,413 white males employed at least 2 years at Rocky Flats was published in 1987. Deaths were included that occurred through 1983. This study examined the association between deaths due to brain cancer and internal depositions of plutonium, and external exposure to ionizing radiation. The excess risk of brain tumors noted in 1983 was still present. There was no evidence of increasing deaths due to all cancers with increasing radiation exposure. Among the cohort, there were no statistically significant excess death rates among the 28 cause of death categories. A statistically significant, but slight excess risk for all causes of death and a strong excess risk for tumors of the lymphatic and bone marrow system, combined, were found in workers with high plutonium depositions when compared to workers with low depositions. A comparison of workers with 1 rem or more of external radiation to those with less than 1 rem revealed no statistically significant excess death rates among the 28 cause of death categories. The excess of brain tumors is the subject of continuing investigation at Rocky Flats. A followup study, including vital status through 1990 and updated radiation exposures is expected to be completed in 1994.
In another program a historical toxicologic review of the Rocky Flats operations and a community dose reconstruction study is being performed by the Colorado Department of Health under a Department of Energy State Health Agreement. The toxicologic review, completed last year, indicated that plutonium and carbon tetrachloride were the major contaminants released. Dose estimates are preliminary and additional work underway will complete gaps in information and reduce statistical uncertainties in the results.
Q. Where are you going to take the highly enriched uranium stored at Rocky Flats?
A. The basic option is to send the highly enriched uranium to the Y-12 Plant, but we are still studying options. Plans are for the material to not remain at the Rocky Flats Plant.
Q. Why are there significant amounts of enriched uranium at Rocky Flats, we thought that the plant worked on plutonium?
A. Rocky Flats worked mainly on plutonium weapon pits, but also worked with highly enriched uranium.