Lesson Learned Statement:When planning work in areas with high concentrations of contamination that can become airborne, it is important to identify the levels of contamination prior to work starting and to continuously monitor personnel working in these conditions. Always calculate with a conservative safety factor when determining the required PPE.
Discussion:On February 2, 2001 as D&D Operators were packing waste in the Process Mechanical Crane Room Enclosure (PMCRE) when radiological controls personnel noted an increasing level of airborne radioactivity and that a towel swipe of the area near the rolling hatch cover opening showed an elevated level of loose radiological contamination. They terminated the entry. Later analysis revealed that the Derived Air Concentration (DAC) Values exceeded the supplied air respirators with HEPA cartridge backup being used. The intended maximum airborne value for this type of PPE is 1000 DAC. Analysis of the Breathing Zone Air Sampler (BZAS) worn by one of the operators indicated that the DAC was approximately 2150, which is 2.15 times the protection factor.
Discussion with RP and D&D personnel found that the loose contamination in the PMCR is known to be high and that containment efforts (use of “clear coat” and laying down of mats) were taken. During the packaging and movement of the waste, one of the mats was “snagged” and the resultant movement stirred up the loose contamination. The work in the PMCR has been in progress for approximately 2 months and this is the first instance of this type of problem.
The second event occurred after D&D Operations personnel and an RCT had power vacuumed floor of a 16 by 23 foot room and removed accumulated debris for about 4 hours. Operations personnel were suited up in double protective clothing (PC) with supplied breathing air and electronic dosimetry in addition to normal dosimetry. This was the fifth entry for this job. The workers observed nothing unusual upon exiting the work area.
Approximately 1 hour after the entry was terminated, Radiation Protection evaluated the air samples and found that the airborne activity levels were above the DAC Values for the supplied air respirators with HEPA Cartridge backup PPE that was used. The intended maximum airborne value for this type of PPE is 1000 DAC. Analysis of the BZAS worn by one of the operators indicated that the DAC was approximately 6000. Nasal swabs were collected during the dress down of the involved personnel. These swabs were processed and results returned negative. Whole body counts and urine samples taken from the involved workers were negative.
During the critique, the work methods employed were described and analyzed by the participants to assist in identifying any activity that could have caused an unexpected increase in the airborne concentrations. None were identified. The personnel movements and work tasks were described to try to find a trigger event for this occurrence.
Analysis:These two events necessitate that RP should evaluate dress requirements for similar work tasks. The work in the ARPR was stopped until an evaluation could be completed. In both of these events there were no personnel contaminations and the workers were in complete compliance with the work documents for the activities.
Recommended Actions:Always calculate with a conservative safety factor when determining the required PPE. In both cases the work had started and an event triggered a higher concentration of airborne contamination. To remedy the first event in the PMCRE, a layer of fixative was applied over the whole floor area and then covered with a tarp for the workers to walk on. This solved the problem. In the Acid Recovery Pump Room, workers completed the debris removal while wearing a Bubble Hood and vinyl suit over a supplied air respirator. The floor area was then grouted and workers were then able to go back to wearing full face respirators with supplied air. Additional actions are taken to increase localized monitoring of airborne activity in high contamination areas where conditions are likely to change. It would also be beneficial to further investigate how other sites are monitoring workers in high airborne contamination areas.
Originator:West Valley Nuclear Services
Contact:Richard Hazard, (716)942-4367
Name Of Authorized Derivative Classifier:Not required
Name Of Reviewing Official:Joe Marek
Priority Descriptor:Yellow / Caution
References:Critique Minutes CM2001-004
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DOE Function / Work Categories:Radiation Protection
ISM Category:Analyze Hazards
Hazard:Personal Injury / Exposure - Radiation / Contamination
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