NS reviewed two events this week involving internal contamination at the Hanford Plutonium Finishing Plant (PFP). On March 17, 1993, one worker received internal contamination and three others received nasal contamination when a filter holdown clamp retaining device failed while they were preparing to change a High Efficiency Particulate Air (HEPA) filter. The two millwrights were testing the filter holdown clamp when one clamp retaining device apparently failed, allowing part of the clamp to slide partially out of the contaminated filter box. This released contamination into the room where personnel were working. None of the ten workers in the room were wearing respiratory protection.
The two millwrights received sufficient contamination that they were injected with DTPA, a chemical used to reduce the absorbtion of metals such as plutonium and americium into organs in the body. Pacific Northwest Laboratory Health Physics personnel estimate the 50-year Committed Effective Dose Equivalent for the individuals is less than five rem. Neither of the two Continuous Air Monitors (CAMs) in the room alarmed. (ORPS Report RL--WHC-PFP-1993-0018)
Facility personnel are determining the failure mechanism and its applicability to other filterboxes. PFP Management stopped work on the filterbox until the assessment is completed and initiated a review of all other work involving radioactive filters.
Five days later on March 22, 1993, three operators received nasal contamination and one received facial skin contamination while attempting to clear a clogged rotameter. The rotameter is part of a clean-air system that supplies air to radioactive waste tank air bubblers, which are used to determine tank levels by measuring the weight factor and specific gravity of the tank contents. After unsuccessfully attempting to clear the rotameter by adjusting the air inlet valve and tapping on the flow tube with a ball- point pen, the operators returned the rotameter to its normal configuration. Shortly afterwards they heard a hissing sound and the room CAM alarmed. The two operators and two other persons immediately exited the room. Operations personnel donned appropriate protective clothing and respiratory protection, re-entered the room, closed the rotameter air-inlet valve, and wrapped the rotameter with plastic and tape to prevent additional spread of contamination. Whole body surveys on the four persons showed no evidence of internal contamination. Facility personnel have not yet determined the source of the contamination. (ORPS Report RL--WHC-PFP-1993-0020)
As a result of these and other recent occurrences at PFP, the Plant Manager curtailed certain operations and maintenance activities at the facility. An independent investigation team was established to review all activities being conducted at PFP and to identify barriers to additional occurrences (ORPS Report RL--WHC-PFP-1993-0022).
NS will provide additional information on corrective actions and lessons learned from the PFP events in future OE Weekly Summaries.