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.

1. Test safety system components even if they are new.
2. Do not rely on listening for valve movement as confirmation that a valve is closing; measure downstream pressure to determine if the valve is really sealing properly.
3. Lock the valves when working in gas manifolds.
4. Maintain a clear path to the exit in case of an emergency.

Recommended Actions:

• The recommended safe storage time for AHF is two years. Contact the vendor for pick up and disposal for cylinders more than two years old. (Unused gas should also be returned, even if it has been less than two years since it was obtained.)
• If the cylinder is less than two years old and there is a desire to keep it, then: Check the pressure of the cylinder. It must be within the maximum pressure stamped on the neck of the bottle. If the pressure is at or above the cylinder's maximum pressure, contact the vendor for pick up and disposal. Do not attempt to move the cylinder yourself.

If below the cylinder's maximum pressure, vent excess pressure through an appropriate medium. Use a two-person team. Conduct venting in a fume hood. Control all ignition sources during venting, since most of the vent gas will be H₂. At a minimum, wear chemical goggles, nitrile gloves, and a lab coat for protection against gaseous HF. Keep an HF exposure kit on hand. An eyewash and safety shower must be readily accessible (within a ten-second travel distance). Any skin, eye or respiratory irritation may be indicative of a possible exposure. Follow the first aid procedures listed on the exposure kit.

In any event, the lesson that should be derived from this incident is the fact that the explosion could have been avoided either by using an inert gas instead of air across the diaphragm, or by monitoring the hydrogen concentration in the upper hemisphere.

As demonstrated by the fire discussed above, lack of adequate maintenance, system monitoring and oversight of maintenance of these facilities can contribute to the ignition of a fire that is difficult to extinguish and poses an extreme danger to fire fighting personnel. Properly maintaining, monitoring and overseeing of hydrogen storage facility equipment can minimize the risk of fire or explosion.

This incident illustrates how a hydrogen fire which appears to be 'quite small' can actually be only the visible portion of a much larger fire. Observation alone is not a reliable technique for detecting pure hydrogen fires and/or assessing their severity.

An important lesson to be derived from this incident is the need to carefully engineer and test all repairs and modifications to high-pressure process equipment.

This incident illustrates how difficult it is to completely purge hydrogen out of a large, complex piece of equipment. Uniform mixing and dilution is unlikely in all the partially enclosed spaces, crevices, etc. If a hazardous operation such as welding must be performed with an air atmosphere (instead of inert gas) in the equipment, reliable gas concentration measurements should be obtained at several different locations. In the case of the generator, a direct measurement of hydrogen concentration may well have been more reliable than the 100 percent CO₂ reading on the densitometer. Furthermore, the gas composition should have been determined at the welding site as well as the top of the generator.

The importance of purging hydrogen piping and equipment is discussed in the Lessons Learned Corner on this website.

This incident illustrates the danger of hydrogen being inadvertently released through blown water seals. Similar incidents have occurred in non-nuclear industrial facilities, but offgas systems present a special hazard because of the stoichiometric proportions of the offgas mixture.

The mechanisms and rates by which hydrogen gas is generated and subsequently accumulated in the holding tank need to be fully understood by vendors and employees alike. Active venting, warning signs, and local alarms designed to activate when hydrogen ventilation lines are obstructed are essential.

The above described events are an indication of a potential licensee/vendor interface problem. Based on the information received, the vendor was not completely informed via the purchase specifications regarding the service condition to which the valve would be exposed. Further, all users of these valves were not notified of the initial problem through either oversight by the vendor or as a result of the valves being supplied through an intermediate source. To avoid similar incidents in the future, onsite personnel need to ensure that their vendors receive comprehensive specifications relating to the application, use and service conditions associated with all of the stainless steel valves implemented in applications susceptible to hydrogen embrittlement.

A web-based resource developed by Sandia National Laboratories to provide data on hydrogen embrittlement of various materials is available at Technical Reference for Hydrogen Compatibility of Materials.