This incident occurred due to moisture in the sample line monitoring system. Removing moisture from the sample line increases the reliability of the equipment. Further evaluations are being considered for improving system reliability.

Although most of the hydrogen fluoride piping system was open to the atmosphere before the elbow was cut, the lines were not purged. Two plugs of residual material on either side of the elbow remained in place, thus allowing hydrogen to be trapped in the elbow. In the future, piping systems containing hydrogen fluoride or other chemicals should be purged to ensure that they are free from hazards prior to starting D&D activities.

Follow-up investigation of this occurrence confirms that it was inadvertent. Attention to detail while performing any task is a must for all personnel. This is to insure the safety of both the individual performing the task and others that may become involved.

Work pre-planning is essential whenever maintenance or work activities may have an adverse impact on everyday operations. When there are changes to the operational status of any critical system, especially a safety critical system, those changes must be communicated to affected personnel. Standard operating procedures (SOPs) must be fully implemented, and the implementation should be verified during facility and organizational assessments.

Additional information on planning for maintenance and start-up and inspection of equipment is available in the Hydrogen Safety Best Practices Manual.

The simplicity of this situation has made us aware that increased consideration must be given to all aspects of the workplace when preparing preliminary hazard assessments. Some hazardous situations appear so trivial that they can be easily overlooked and serious consequences not understood. Also, some hazardous situations are not readily recognized by the layman and we should consider inviting professionals from other organizations to assist us with assessments and reviews on a periodic basis.

Adequate ventilation of battery charging facilities is addressed in the Lessons Learned Corner on this website.

Hazard assessment is critical during the design, fabrication, and installation of system modifications to ensure hazards and potential hazards are addressed prior to system start-up and operation.

Personnel should be aware that items requiring special receiving inspections should still be verified/examined by the end user prior to use.

Given that the anaerobic chamber and associated nearby electrical equipment were not designed or expected to handle a potentially explosive atmosphere, nearly all conditions necessary to have a much more serious event were present if the problem had not been discovered and the bag was not successfully purged of the hydrogen mixture.

Hydrogen use in anaerobic chambers is discussed in the Lessons Learned Corner on this website.

All chemicals, including gases, should be clearly labeled and expiration dates (if applicable) identified. Incidents are more common when incompatible chemicals are mixed or when chemicals are stored/transferred using incompatible equipment. Personnel should ensure that labels are read and understood prior to mixing, dispensing, or transferring chemicals.

The manufacturer will be notified of the failed parts identified as a result of the follow-up testing plan. These results may be useful to them for their information and forwarding to others with the same equipment.

Designs for high-tech systems/components evolve based on operating experience. The design changes should resolve identified deficiencies and are part of a continuous improvement process to increase reliability and productivity.

Laboratory accidents can happen despite the best preparation and careful attention to procedures. However, the lesson to be learned here is that employees must always be sure they understand the hazards of the activities, and that they know how to respond to emergencies. This is accomplished through on-going training in emergency procedures, and in understanding the procedures and equipment.

Diligence needs to be practiced when performing assigned work tasks. To guard against complacency, it is necessary to emphasize adherence to established procedures, including appropriate reviews of preventive maintenance instructions (PMI) and related on-the-job training (OJT). Another lesson learned was that the craftsmen need to be familiar with the total system safety controls. They did not realize, for example, that the furnaces would automatically purge hydrogen with an inert gas for safety reasons in the event of a flow interruption. Had they known this, they would not have been in a hurry to correct the error and turn the hydrogen back on. The hurried action caused an immediate surge in the flow, and in turn caused the excess flow valve to shut. This compounded one error into two errors. They should have stopped when they initially made the error, and notified the hydrogen system engineer.

The lessons learned in this situation center around basic conduct of operations principles. Policies and procedures related to operations performance, safety performance, and management oversight were in place. They were not employed appropriately.

There were approved operations procedures in place to provide direction to personnel to ensure that the SHMS would be operated within its design basis. Those approved and available procedures provided the needed operational direction to accomplish safety, process quality, and control activities. Had the operator made use of the available procedures, the incident very likely would not have occurred.

When operational direction is available (procedures, turnover logs, etc), compliance with that operational direction is required. Communications and shift turnover protocols in this situation were wholly inadequate. Accurate communication is essential for the safe and efficient operation of facilities, systems, and equipment; highly reliable communication provides accurate transmission of information within a facility. That transmission of communication did not occur in this situation. The facility operations personnel should have known the status of all equipment and systems, and should have been able to maintain control at all times. The saltwell pumping activities require interface and coordination between roving operators, specific evolution-related operators, and shift supervisors. That integrative communication did not take place. From the shift supervisor on down, shift personnel should have been aware of operations planned or in progress; status of facility systems and equipment; and any abnormal conditions which may have existed. That information was not effectively documented or transmitted. In addition, the authorization, communication, and documentation of status changes was not thoroughly executed.

Startup and shutdown of systems and equipment require assessing status on a continuing basis. Notification of changes in system status by operators and shift supervisors must be comprehensive and complete to ensure an understanding of and adherence to precautions and prerequisites for safe shift evolutions.

On-site personnel performing treatment of reactive metals/chemicals must continue to exercise caution. Although there is an inherent risk in treating reactive metals/chemicals, personnel must adhere to conduct of operations principles to include conducting a formal pre-evolutionary briefing. During the briefing, a review of the job safety analysis and/or other applicable policies/procedures should be discussed to ensure strict compliance with all safety precautions associated with personnel protection. Prior to commencement of treatment processes, laboratory hoods must be designed with appropriate blast shielding or other pre-determined engineering safety features.

Thoroughly plan and schedule work such that the correct tools are at the job site. If activities take place that take the job supervisor away from the job location while critical steps are to be performed, the work should be temporarily stopped. A ferrous tool used in combination with spark-less tools is a potential spark producer.

Utilize a Six Sigma Black Belt to statistically evaluate LFL monitor reliability and determine the failure rate based on the existing technology.

Revise the tank uncertainty calculation and surveillance to include a wider "Required Accuracy" range like the other tanks LFL monitors "Required Accuracy" ranges.

Evaluate minimizing the "Calibration Staff" for the LFL monitors, i.e., establish a small qualified crew of maintenance personnel who are allowed to calibrate the LFL monitors.

Also, submit DSA change request to require installed monitors only when tanks are in agitation e.g., slurry pump operation, salt dissolution, interstitial liquid removal. When in static state, utilize the portable LFL measurement instrumentation. With appropriate basis, this could result in elimination of installed LFL monitoring equipment on specified tanks.

In the future, the laboratory will issue a memorandum about this incident to illustrate the need to wear safety glasses with side shields, store chemicals compatibly, take care when placing chemicals in the refrigerators for storage, and keep the quantities minimal. The laboratory will issue guidance regarding chemical storage hazards, identifying the hazard and requiring all chemicals to be stored according to compatibility, with secondary containment provided, in approved refrigerators.

The main point to keep in mind is to minimize the quantities of reactive materials to be stored in refrigerators. Chemicals placed in refrigerators should be stored with regard to their chemical compatibility, and secondary containment should be provided to prevent contact with incompatible chemicals.

Additional discussion about working with reactive metal-hydride materials in the laboratory can be found in the Lessons Learned Corner on this website and in the Hydrogen Safety Best Practices Manual.

Implementing and enforcing the laboratory's stop work and restart policy and procedures in conjunction with peer reviews for new processes and experiments should help prevent future accidents due to a lack of recognition of potential reactions and hazards. This abnormal event points out the need to call appropriate personnel when an abnormal event occurs. Safety personnel recommended all cleaning products be treated as potentially reactive mixtures.

There is no such thing as an "always safe" cleaning solvent, including water. The reactivity and safety hazards of all materials must be considered, and only materials properly evaluated for the particular process involved must be selected.

In the future, proposed processes and experiments need to be reviewed for potential hazards. Both a chemical engineer and chemist interviewed recognized the potential reactions and hazards when carbon and magnesium oxide or carbon and aluminum oxide are heated to above 1400° C. However, other staff members did not have the same degree of understanding of the potential reactions and hazards involved. The technician was instructed to clean the interior surface of the furnace top before the results of samples taken were analyzed because it was assumed that the support/spacer plate used during the process was an aluminum oxide plate. A peer review of proposed processes and experiments would have provided a needed potential reactions and hazards review.

Frequently inspect and maintain all elements of hydrogen-related systems.

A flammable gas explosion is an analyzed hazard and gas detection/shut off is a safety significant control system that requires a limiting condition for operation (LCO). The rigor of the evaluation of flammable gas systems was inadequate. There was no independent calculation for the hydrogen cylinder and there was no report to document the findings of the evaluation. As a result, incorrect assumptions were made about the acceptability of the hydrogen cylinder. Calculations, independently verified by an engineer, must be included for processes involving a flammable gas and must accompany the hazard control plan for approval.