McGuire Nuclear Station Welding Exposure OSHA Asbestos Class III Refresher 2009
Summary of event During an outage, air monitoring samples taken on welders inside carbon steel piping indicated overexposures to welding fumes & manganese. Six samples taken 6 of 6 over ACGIH TLV of 0.2 mg/m3 for Mn 2 of 6 over OSHA PEL of 1.0 mg/m3 for Mn 3 of 6 over OSHA PEL of 5 mg/m3 for welding fumes (no ACGIH TLV) No health effects reported by workers 2
Sequence of events Prior to outage, McGuire EHS reviewed work planned for confined spaces. This space (steam crossover piping) is entered for welding during most outages. Evaluated first as permit-required confined space, but once drained, cooled, ventilated, isolated, and tagged is normally downgraded to an alternate entry space. Practice in past has been continuous air monitoring for O2, CO, explosive gases, and H2SO4. 3
Sequence of events (con t) Industrial Hygiene was contacted by job supv. & asked to purchase dust masks for welders comfort. (Pipe has heavy buildup of corrosion products.) Because of planned welding and flammability concerns, use of dust masks (P-100s) was denied & suitable welding dust mask was found. (For unknown reasons, welders did not wear these masks.) Respirators have never been worn in this space at any of Duke s nuclear stations. 4
Sequence of events (con t) Ventilation was set up by using large blowers at entry to pipe the welders used and at another pipe opening. Vent path was established when manways were removed from moisture separator reheaters. Industrial hygienist took air samples on different days to get data to better characterize conditions for future work. 5
Piping System 6
Sequence of events (con t) Samples were sent to offsite lab for analysis since McGuire does not have ability to analyze these types of samples. Normal turnaround time for this analysis is ~2 weeks. Samples can be rushed to turnaround in 3-4 days, but were not rushed due to no suspicion of overexposure. 7
Sequence of events (con t) Samples were received indicating overexposures to Manganese and welding fumes. Workers and their supervisors were notified. Subsequent search of air monitoring database revealed no similar samples had been recorded at any facility across the Duke enterprise. IHs at Catawba, Oconee and Corporate offices were notified to alert them of possible conditions of overexposure at other Duke facilities. Nuclear Network message was sent. 8
Sequence of events (con t) Nuclear EHS took immediate action to require respirators to be worn for any welding activities on carbon steel in confined spaces. Additionally, EHS groups were directed to sample all welding activities on carbon steel in confined spaces to build sample database information. 9
Cause analysis An apparent cause investigation concluded that the overexposures resulted from inadequate hazard analysis and pre-job planning. Maintenance conducted welding inside the piping without requesting additional EHS evaluation because ventilation had been established. They understood EHS had given approval for this activity in the past once ventilation was set up. 10
Cause analysis (con t) Contributing causes: EHS did not take air flow measurements to ensure adequate ventilation established. Amount of welding in this piping was much greater than in previous outages. Turbine shell was not removed this outage as it had been done in previous outages which inhibited air flow through this piping. 11
Corrective Actions Require respirators for welding on carbon steel in confined spaces until sample database information supports that adequate protective measures can be taken to prevent overexposure. Update confined space entry process to ensure EHS takes air flow measurements to ensure adequate ventilation. Request Corporate EHS develop a Duke Energy EHS Compliance Manual section to provide better guidance for welding activities. (Currently no corporate or nuclear specific guidance exists.) 12
QUESTIONS??? 13