Lesson Learned Statement:The failure to periodically check high-efficiency particulate air (HEPA) filters for contamination, when on the discharge of a diaphragm pump, can result in the HEPA filter becoming saturated and contamination exiting the barriers setup to contain it. It should also be noted that a diaphragm can leak through and remain operational.
Discussion:During a routine radiological survey of dirty laundry received at the Oak Ridge National Laboratory (ORNL) Decontamination Laundry, technicians detected radiological contamination on the white, company-issued coveralls that had been worn by a Lockheed Martin Energy Research (LMER) supervisor. The supervisor is involved in a project that is being performed by LMER under contract to Bechtel Jacobs Company LLC. An investigation resulted in the discovery of contamination on the floor of the Building that houses the pump module which is utilized to transfer wastewater. A smear taken from a high- efficiency particulate air (HEPA) filter located on the air discharge of the double diaphragm transfer pump was found to be contaminated. This indicated that the diaphragm was leaking, allowing small amounts of contaminated waste to mix with the discharge air. It was ascertained that the contamination of the worker's coveralls occurred when he was relieving pressure from a prime water hose, causing a stream of water to hit the contaminated floor and splash back on the coveralls. This explained the pattern of contamination on the coveralls which was distributed over the waist and knee areas. The worker wearing the coveralls followed the radiation work permit and posted instructions as they were written at the time the coveralls were contaminated. At that time, due to the radiological condition of the facility, only gloves and shoe covers were required with a frisk of hands and feet after removing the personal protection equipment (PPE). After discovery of the change of radiological conditions, the PPE was upgraded to include two pair of shoe covers and Tyvek coveralls over company clothing. The frisking requirements were revised to include a whole body frisk. After decontamination of the structure, the PPE requirements will revert back to the original PPE. There was much discussion as to whether the more stringent PPE requirements should be kept after the building was decontaminated, but it was decided by the investigation team that impacts to the area of pollution prevention (increased generation of solid waste), budget, and worker safety (increased heat stress) outweighed the risks and probability of another incident of this type. The probability of another incident has been greatly reduced by the actions taken and the action to periodically take a smear of the HEPA filter exhaust for contamination. In addition, the revised requirements that a whole body frisk (instead of only hands and feet) when exiting the area will remain in affect.
Analysis:The direct cause of the occurrence is the failure of the pump diaphragm which allowed the discharge air from the transfer pump to become contaminated and eventually saturate the HEPA filter, thus allowing contamination to spread onto the floor of the pump module. Normally, a puncture of the diaphragm in this type pump will render the pump useless, but in this case, the pump was operating with the leaking diaphragm. It is not known when the pump diaphragm began leaking, but it is believed that the leak was very small, as the pump continued to operate with the leaking diaphragm. The root cause of the occurrence is end-of-life failure of the pump diaphragm. According to the pump manufacturer, the diaphragm of this type pump should pump 210,000 to 735,000 gallons (2,000,000 to 7,000,000 cycles) before failure depending on conditions the pump is used. Because of the type wastewater being transferred, time between use, and temperature variations, the environment for this pump is considered very harsh. It is estimated that the pump transferred approximately 300,000 gallons of waste so the failure of the pump diaphragm was not unexpected. Changing out the pump before estimated failure was discussed, but due to the high radiation and contamination levels inside of the pump module, this was not considered good as low as reasonably allowable (ALARA) practice.
Recommended Actions:The following actions were taken to mitigate recurrence: 1) the diaphragm pump (which was installed in 1987) was replaced with a new pump; 2) the contaminated HEPA filter was replaced; 3) the out-of-tank procedures was revised to add the smearing of the HEPA filter discharge whenever feed and concentrate samples are taken; 4) the incident was communicated to all Waste Operations operating personnel; and, 5) a lessons learned was issued.
Originator:Bechtel Jacobs Company, LLC; Randy J. Mehlon, 423-574-6830 Performance/Quality Assurance
Validator:W. E. Palmer, 423-576-4075, Office Of Quality Services
Contact:Joanne E. Schutt, 423-574-1248
Name Of Authorized Derivative Classifier:H. R. Woods
Name Of Reviewing Official:
Priority Descriptor:Blue / Information
Keywords:HEPA FILTER, CONTAMINATION, RADIOLOGICAL, COVERALLS, PUMP, DIAPHRAGM, PPE
References:Occurrence Report: ORO--BJC-X10WSTEMRA-1998-0001
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DOE Function / Work Categories:Environmental Restoration
Hazard:Personal Injury / Exposure - Mechanical Injury (Striking / Crushing)
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