Bioassay Programs Urinalysis Program

Workers exposure to uranium was assessed by periodically measuring the concentration of uranium in urine samples. Urine samples were collected and analyzed more frequently from individuals who had shown positive uranium bioassay results in the past. During the 1950s and 1960s, urine samples were typically analyzed for uranium, and in most cases for alpha activity. Typically, the sample collection procedure involved the collection of Monday morning urine specimens (the morning following two or more days off the job). This was non-conservative, and the collection date evolved to a “Friday” sample during the 1970s and 1980s. Considering that numerous routine urinalysis results reflected uranium intakes in the years of operation and the rate at which soluble uranium is excreted, some uranium intakes were likely not identified or properly investigated. Technetium analysis was added in the 1970s.

The PORTS restriction criterion from the start of operations to December 1956 was based on the most conservative urinary uranium excretion limit at the time. The minimum level of activity reported for uranium was 5 µg uranium/L and/or 0.3-dpm/100 ml for alpha activity. These limits were based on insoluble uranium in the lungs. However, after several years of Plant operation and experience it was determined that the allowable excretion level of uranium would be more realistic if it were based on soluble materials and

Mass Spectrometer Used to Improve Isotopic Analysis of Process Gas

toxicological consideration for the kidney. Investigation levels were subsequently raised to 50 µg uranium/L and/or 10 dpm/100 ml for alpha activity, which was not a conservative decision because actual solubility in some areas was not always known.

Positive urinalysis samples resulted in an increased frequency of collection, and each case appears to have been given individual attention, with separate records being maintained by the Industrial Hygiene and Health Physics Department. In cases of suspected inhalation of uranium, such as during releases, the department supervisor was responsible for recommending that the personnel involved submit a urine sample. Personnel were placed on accelerated sampling schedules if they were engaged in special projects or were in contact with high-assay material; worked in areas with air sampler results indicating significant levels of airborne contamination; or as a direct request from the Medical Director. All samples above a predetermined recall guide for uranium or alpha activity were followed by an immediate recall sampling until a negative result was obtained.

Throughout Plant history, there were numerous administrative restrictions for concentrations of uranium in urine above the administrative guidelines. These employees were reassigned to areas with less potential for uptake. Biological retention times for these exposures are closely related to the solubility of the compound. Information from interviews with former workers and much of the sample analysis data from the late 1950s assumed intakes to be from soluble compounds. This assumption may not have been conservative for some aerosols generated during all operations. Health and safety activity reports from the mid-1960s identified that excessive inhalation of uranium compounds was the major radiation and contamination risk at PORTS. PORTS documents also reveal that internal deposition became a problem in 1965 from handling insoluble enriched uranium, and that urine sample results were neither reliable nor as sensitive as analysis for soluble forms. Consequently, an in-vivo body counter program was initiated in 1965. Documents reviewed for the first quarter of 1978 indicated that “Based on the weight analysis via fluorimetric detection and the monitoring frequency it is possible to exceed, undetected, the maximum permissible weekly uptake.” The documents also indicated that samples were collected and analyzed for technetium. Correspondence dated as late as 1988 related to oxide repackaging stated that “Oxides of uranium are known to have different chemistry from the uranium fluoride compounds generally encountered

at the site. The current urine monitoring program is not adequate to detect significant exposures to uranium oxides in a timely fashion.” This correspondence also noted that “available analysis of the oxide does not include sufficient information to determine whether exposure controls are appropriate since they are based on [transuranics] being insignificant for the purposes of dose assessment and control.”

In-Vivo Radiation Monitoring

Since the inception of the in-vivo monitoring program at PORTS in 1965, the selection of individuals for in- vivo analysis was based on work history, work environment, airborne concentrations, and past in-vivo and urine sample results. The PORTS Medical Director, upon recommendation of Industrial Hygiene and Health Physics, approved the individuals selected for restriction and subsequent removal. There were two classes of work restrictions: 1) an individual was neither to be exposed to any form of uranium material nor assigned to areas where there was potential for airborne uranium compounds; and 2) the individual was limited to work in areas where the average airborne alpha activity should not exceed a small percentage of the limit. There were two problems with the criteria. First, the large number of unexpected releases in most buildings made the first criteria difficult and unrealistic to administer. Second, a restricted individual should not have been placed in a work location with any potential airborne radiation activity. In-vivo radiation monitoring (lung counting) was initially conducted by sending individuals to either Fernald or Oak Ridge. Later, PORTS used a mobile laboratory from Oak Ridge. Data indicated that personnel were monitored at about six-month intervals for uranium, neptunium, and technetium. The analysis was generally reliable for insoluble forms of uranium since the lung was the critical organ.

In a report prepared for Martin Marietta Utility Services in 1990, the effectiveness of the mobile whole body counter was evaluated for analysis of uranium, neptunium, plutonium, and americium. Additionally, a review was conducted of historical lung counting data from Martin Marietta Utility Services sites, with particular emphasis on neptunium-237. A summary of the findings indicated that the counter’s capability for analysis of those radionuclides, with the exception of uranium-235, was somewhat questionable due to system hardware limitations (i.e., use of sodium iodide detectors, resolution of spectra insufficient to identify peaks in the presence of background radiation,

efficiency calibrations did not use multiple source strength measurements for isotopes other than uranium- 235). The studies of historical data indicated difficulties, including the inability to retrieve the appropriate data, lack of system access, and insufficient documentation. The root cause for most of the problems could be attributed to physical limitations of the system, lack of understanding of these limitations, and the lack of adequate training. Incomplete isotopic and uranium solubility characterization, coupled with design and analytical limitations, has impacted the Plant’s ability to demonstrate that all internal exposures have been accurately detected and assessed.