A liquid hydrogen neutron moderator developed a leak between the canister that contains liquid hydrogen and the insulating vacuum jacket.

The moderator assembly consists of an exterior metal vacuum jacket with an interior metal transfer line and canister that contain liquid hydrogen. The moderator canister is constructed of aluminum and is approximately five inches wide, five inches high, and two inches deep. The liquid hydrogen supply lines to the moderator canister are constructed of stainless steel. The operating temperature of the moderator varies from -420 degrees Fahrenheit to a possible 300 degrees Fahrenheit. Mechanical operators discovered a leak following a cleaning operation on the moderator. The cleaning operation was performed to remove impurities that could freeze view more

During a facility walk-through, it was noted that a combustible gas (hydrogen) monitoring system installed in a furnace room was inoperable (the system had been unplugged). This system is used to detect and warn facility employees of an explosive or flammable environment. An explosive or flammable environment can only occur if there is a leak in the system, which would not be expected to occur during normal operations. When the system was reactivated, no leaks were indicated.

The incident had the following three causes:

A procedure describing administrative controls necessary to ensure safe operations in the area should have been developed and implemented prior to disabling the hydrogen monitoring system.
The hydrogen monitor was not hard-wired, which allowed it view more

A hydrogen monitor leak detector (HMLD) was out of service because of a failed membrane. The HMLD heater circuit and the ion pump and its associated controller were de-energized and red-tagged to ensure the system remained shut down. The ion pump and controller were later found energized. The ion pump circuit is a low-power (120-V, 1 amp) circuit and the pump operates in the micro-amp range. There was no damage to equipment from this inadvertent energization. There was also no personnel safety hazard since the tag out was not for maintenance purposes and since the system was in its normal operating configuration.

The direct cause is listed as personnel error, inattention to detail. This category most closely describes the inadvertent actuation of the controller toggle switch. view more

A routine security patrol reported a strong odor of sulfur coming from a battery charging facility. The battery charging facility is used for charging the various forklift batteries for the shipping and receiving operation. The building is approximately 450 sq. ft. and has four charging stations. Emergency response was initiated and the incident commander responded to the scene. Initial air monitoring indicated readings above the Lower Explosive Limit (LEL) for hydrogen gas. The local fire department responded and setup for the situation. Facilities personnel responded and turned power off to the building. The building was ventilated and verified to be safe by the fire department. There were no injuries or damage.

The exhaust fan for the building failed, allowing hydrogen gas to view more

A process area alarm activated. The alarm was caused by an instrument channel located above a reaction vessel off-gas system final HEPA filter canister, which indicated 25% of the lower explosive limit (LEL) for hydrogen. Since the only source of hydrogen is from the reaction vessel during the reaction of sodium with concentrated sodium hydroxide, the immediate actions were to shutdown the reaction process and place the facility in a safe condition.

The root cause was inadequate or defective design. Had the pre-filter drains been vented to outside the building, no hydrogen could accumulate in the process area. The corrective action for this is to complete an Engineering Task Authorization (ETA) to install a sample/drain collection system with loop seals to prevent any release of view more

A temperature excursion occurred in a sealed environmental chamber during a 0°C ambient temperature test. An elevated temperature in the chamber resulted in a small fire that was confined to the environmental chamber. Visual observation indicated no damage to nearby equipment, including nearby computer cables.

A committee was assembled with the task of identifying the cause of the incident. The committee concluded that the fire was caused by failure of the heater control system for the environmental chamber. The failure of the heater control system caused the chamber temperature to eventually exceed 200°C. As the chamber temperature increased, plastic materials and electrical insulation present in the chamber started to decompose. A battery scheduled for testing was also located view more

A control room received a tank lower flammability limit (LFL) analyzer low sample flow alarm. The control room operator initiated the appropriate alarm response procedure and the facility entered limiting conditions of operation. At the time of the alarm, the facility was experiencing severe weather and the field operator was unable to investigate the alarm in the field. After the severe weather cleared, the field operator investigated the alarm and found the sample flow to be low and out-of-limits.

At the given facility, composite lower flammability limit (CLFL) monitors are used to detect the presence of hydrogen and other flammable gases in waste tank vapor spaces. Maintaining the concentration of flammable vapors in tank vapor spaces below CLFL levels maintains tank view more

While research staff were working in a lab, a staff member opened the primary valve to a 0.2" (1500 psi) hydrogen gas line connected to a manifold supplying instruments in the lab. Upon opening the valve, the hydrogen gas line failed at a fitting on the switching manifold, releasing a small amount of hydrogen gas. The staff member closed the valve immediately, then inspected the gas line and found the front ferrule (of the compression-style fitting) to be missing. There were no injuries or damage to equipment.

In the follow-on discussion with research staff, it was learned that approximately one month earlier, a similar condition (front ferrule missing from a fitting) was found while performing a modification to a similar manifold. Following a critique, management expressed view more

A deficiency was discovered in the application of a hydrogen sensor in the Rotary Mode Core Sampling (RMCS) portable exhauster. The sensor is installed in the flow stream of the exhauster designed to be used with a RMCS truck for core sampling of watch list tanks, and is part of the flammable gas detector system. During the previous week, a quarterly calibration of the sensor, per maintenance procedure, was attempted by Characterization Project Operations (CPO) technicians. Ambient temperatures during the sensor calibration were approximately 20 to 30 degrees F. Inconsistencies in calibration results and the failure of the sensor to meet the response-time calibration requirement lead to the conclusion that the unit could not reliably perform its safety function at low ambient view more

Several workers sustained minor injuries and millions of dollars worth of equipment was damaged by an explosion after a shaft blew out of a check valve. The valve failure rapidly released a large vapor cloud of hydrogen and hydrocarbon gases which subsequently ignited.Certain types of check and butterfly valves can undergo shaft-disk separation and fail catastrophically or "blow-out," causing toxic and/or flammable gas releases, fires, and vapor cloud explosions. Such failures can occur even when the valves are operated within their design limits of pressure and temperature. Most modern valve designs incorporate features that reduce or eliminate the possibility of shaft blow-out. However, older design check and butterfly valves, especially those with external appendages such view more