On January 26, 1993, at the Plutonium Finishing Plant (PFP) at Hanford, Internal Dosimetry personnel of the Battelle Pacific Northwest Laboratory (PNL) notified an individual assigned to the PFP Standards Laboratory of his confirmed internal deposition of Plutonium 239. The individual received the inhalation intake on November 13, 1991, in a room in the Standards Laboratory. The individual stated that when he was venting sample bottles containing plutonium nitrate, he overfilled one of the bottles, and some of the solution spilled on his hand. Personnel performed nasal smears at the time of the incident and results were less than the minimum detection activity (ORPS REPORT RL--WHC-PFP-1993-0009).
In January, 1992, the individual involved in the incident received a bio-assay that was delayed four months as a result of contract difficulties with the firm performing the tests. In May, 1992, additional results were received that indicated the presence of plutonium but the specific amount was below the quantifiable limits of the equipment used. The dosimetry staff at Westinghouse Hanford Company performed a preliminary assessment and, after additional testing, sent the results to PNL dosimetry staff for evaluation. (PNL is responsible for evaluating and monitoring internal contamination events for the entire Hanford Site.)
PNL calculated the 50-year committed effective dose equivalent to be 1100 mrem with the highest annual effective dose equivalent of 110 mrem in calendar year 1992. PNL staff sent the calculation results to the individual on January 26, 1993. The individual was placed on a quarterly test schedule for urine sampling for plutonium and also scheduled for a high sensitivity chest count.
Coincidentally, the same technician was involved in a spill of Plutonium Isotopic Solution in the same room at the PFP on January 19, 1993 (ORPS REPORT RL--WHC-PFP- 1993-0007).
Investigators of this incident cite inattention to detail as a contributing cause of the spill. Investigators are still determining the root cause and corrective actions for the internal deposition event. At this time, the investigation is focusing on personnel error. An early identification of internal deposition of radioactive material is essential to computing an accurate, committed, effective dose equivalent that allows effective utilization of personnel in achieving ALARA goals.