Lesson Learned Statement:Only one procedural barrier exists that prevents possible fire with personnel injury or equipment damage when performing PAO testing with a NUCON model *F-1000-DG-F* Thermal Generator. Site/facility operating procedures need to comply with vendor recommendations. A new hazard analysis needs to be performed if a different aerosol is used.
Discussion:On April 27, 1999, operations personnel were performing in-place HEPA filter penetration testing. The equipment being utilized was a Nuclear Consulting Services Inc. (NUCON) model *F-1000-DG-F* Generator. West Valley Nuclear Services (WVNS) Operations personnel were at the point of aerosol generation during the performance of an approved procedure when a flame was observed. The generator heater temperature had stabilized at 720 degrees Fahrenheit and the liquid flow valve was placed in the ON position. Fine flow adjustment to a predetermined flow rate was made using a rota-meter indication. The next procedure step is to slowly open the vapor adjust control valve (carrier air) until a steady supply of aerosol is observed. At this time, as the valve was slowly opened, a flame two to three feet long was observed emitting from the aerosol generator discharge port. The attending operator immediately closed the vapor control valve and the liquid flow valve, which extinguished the flame. There were no personnel injuries associated with this event. Preliminary investigation into the event discovered that the current vendor manual for the generator recommends that air flow (*carrier air*) be initiated prior to establishing liquid flow. Subsequent controlled simulations by the generator vendor revealed that in instances wherethe liquid flow was established BEFORE the vapor adjust control valve (carrier air) was opened, flames were observed emitting from the aerosol discharge port in about 75% of these tests. As a result of the preliminary investigatory work, WVNS and NUCON are initiating the following: 1) The WVNS operating procedures will be changed to require the vendor recommended valve sequencing (carrier air to be initiated prior to establishing liquid flow through the heater block), and appropriate cautions will be added to alert operations personnel. This administrative barrier is the only factor preventing similar events from occurring when using this model of equipment. 2) NUCON will modify all model *F-1000-DG-F* units utilized at WVNS to change the heater block controller temperature setpoint to 625 degrees Fahrenheit (+/- 25 degrees Fahrenheit). Appropriate warnings and cautions will be incorporated into the WVNS operating procedures to verify this operating range prior to initiating liquid flow. (The vendor can be contacted to discuss why operation within these temperature parameters is safe.) 3) NUCON will modify all model *F-1000-DG-F* units utilized at WVNS to have vapor adjust control valves that always maintain minimal air flow (carrier air), even if the valve is in the closed position. This modification will assure that the event does not recur, regardless of the implementation or success of the other newly instituted barriers. 4) NUCON will revise advertising literature and the model *F-1000-DG-F* manual to indicate that this unit is compatible with PAO applications WITH MODIFICATIONS.
Analysis:West Valley Nuclear Services (WVNS) began using PAO as the challenge aerosol-testing medium for high-efficiency particulate air (HEPA) filters. Previously, the site had used Di (2-ethylhexyl) phthalate (DEHP, commonly referred to as DOP) for this purpose and these aerosols were supposed to be interchangeable.. The equipment being utilized was a Nuclear Consulting Services Inc. (NUCON) model *F-1000-DG-F* Generator. The chemical aerosol utilized was manufactured by the Henkel Corporation, Emery Group, with the product name of *Emery 3004 Synthetic Hydrocarbon 4 CST Fluid,* referred to as polyalphaolefin or PAO, which is a synthetic aliphatic hydrocarbon. When performing PAO testing, the inter-relationship between four variables have serious implications. First, the generator heater block controller setpoint must be evaluated. Currently, all NUCON Model *F-1000-DG-F* production units have a heater block temperature that is regulated at 725 degrees Fahrenheit (+/- 25 degrees Fahrenheit). Second, the auto-ignition temperature of DOP is approximately 735 degrees Fahrenheit and the auto-ignition temperature of PAO is 649 degrees Fahrenheit. Third, the flow rate of the liquid becomes more critical to the equation as higher flow rates of PAO are introduced through the heater block of the generator (utilized in larger capacity systems of 25,000 cfm airflow and larger). The greater the amount of PAO flowing through the heater, the greater the chance that some of the PAO fluid will not completely vaporize in the heater and possibly ignite at the discharge port. Lastly, the carrier air valve (vapor control valve) must have air flowing through the heater block before the liquid (PAO) flow is established.
Recommended Actions:Review in-place HEPA filter penetration testing that utilizes PAO in conjunction with thermal generators; it is necessary to fully understand the inter-relationship between the different components commercially available. Evaluate current procedures and equipment to assure product compatibility and personnel safety. Also verify that temperature settings plus equipment tolerance do not place personnel in a hazardous condition.
Originator:Jack Styne, WVNS, 716-942-2178, email@example.com
Contact:Kim Wilson, WVNS, 716-942-4771, firstname.lastname@example.org
Name Of Authorized Derivative Classifier:
Name Of Reviewing Official:
Priority Descriptor:Yellow / Caution
Keywords:HEPA filter, DOP testing, PAO testing, polyalphaolefin, PAO, Emery 3004, flame, aerosol
References:Occurrence Report OH-WV-WVNS-CF-1999-0002
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DOE Function / Work Categories:Maintenance - Other
Hazard:Personal Injury / Exposure - Hazardous Material (General)
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