On November 27, 1995, the occurrence reporting coordinator at the Weldon Spring Site issued the final occurrence report for an event that occurred on October 18, 1995, in which a subcontractor was sprayed with contaminated raffinate sludge while removing a pressure gage. Raffinate is a waste product of a uranium recovery process. Although the subcontractor immediately removed most of the contamination with a towel, health physics technicians estimated his maximum skin contamination was 35,853 dpm/100cm2 alpha. This event provides useful lessons learned related to opening systems with unknown or suspect pressure. (ORPS Report ORO--MK-WSSRAP-1995-0022)
On October 18, 1995, two subcontractors were performing testing and maintenance activities at the Weldon Springs Chemical Stabilization/Solidification Pilot Plant. Using a test procedure, they were pumping sludge material from a sludge storage tank through pipe lines and monitoring pressure drops when they noticed that one of the gages was not operating properly and decided to remove it. The associated pump was locked out, pressure was relieved, and the valve to the defective gage was closed. When one of the subcontractors began to remove the gage, raffinate sludge material sprayed from the fitting onto the neck of the other one, contaminating him. The raffinate contained Th-230, an alpha emitter.
The sprayed subcontractor was wearing a face shield and saranex suit as well as other personal protective equipment. He immediately removed the material with a towel and contacted his supervisor. The supervisor surveyed him with a beta-gamma detector and found no contamination. The subcontractor was then taken to another area where technicians surveyed him for alpha contamination and measured 34 dpm/100cm2. Health physics technicians subsequently estimated that the maximum skin contamination levels, before being removed, was 35,853 dpm/100cm2.
Investigators found a blockage in the line that prevented pressure relief when the system was bled and resulted in the residual pressure and spraying of the worker. However, because the workers were not prepared for the residual pressure, investigators determined that the root cause was a training deficiency caused by insufficient hands-on experience. They noted that personnel involved with testing and repairing the pumping system were not well trained in recognizing pressure-related hazards. The subcontractor planned to train all operators involved with pilot plant activities to recognize pressure-related hazards and to wrap or otherwise shield joints before opening them if the system pressure is unknown.
NFS engineers have reported the following similar events in the Weekly Summary.
.. On February 27, 1994, two operators at the Idaho Chemical Processing Plant were contaminated on their face and neck when they were sprayed with low-level radioactive liquid from a tank truck they had just unloaded. They were adding denatured ethanol alcohol to the tank to prevent the remaining solution from freezing. Pressure gages indicated no pressure in the tank, but when the operators opened the valve on the unloading port of the tank to add the alcohol, they were sprayed with a mist of radioactive solution. (OEWS 94-09, ORPS Report ID--WINC-WASTEMNGT-1994-0004)
.. On October 27, 1994, a plutonium handler at the Lawrence Livermore National Laboratory was sprayed on the face and chest with contaminated air after disconnecting a line he thought was depressurized. He and another plutonium handler were trying to remove fluid that was blocking a vacuum service line by blowing compressed air through the line. After connecting the line to a compressed air source and cycling the compressed-air supply valve several times, one of the handlers saw liquid and particulate coming out of the line and both handlers mistakenly believed that the line was clear. When one of the handlers removed the compressed air tygon tubing from the nozzle of the vacuum line, contaminated air sprayed out of the still-blocked and pressurized air line. Technicians detected approximately 20,000 dpm/100cm2 alpha contamination on his forehead and 10,000 dpm/100cm2 on his chest. (OEWS 94-44, ORPS Report SAN--LLNL-LLNL-1994-0069)
These events illustrate the need for precautions when opening systems containing hazardous material with unknown or suspect pressure. Contamination or injury can result even if specified personnel protective equipment is worn, as was the case in each of these events. Operators should be trained to recognize conditions in which normal pressure indications may not be accurate or where residual pressure may exist. Recommended precautions when opening systems under such conditions include additional shielding between personnel and the system break point; and, when possible, keeping personnel out of the path of potential discharges.