
Use of Cryogens at Fermi Lab Could Pose Rescue Problems
Fire departments usually make rescue efforts while exposed to high temperatures, smoke and gases. Fire fighters at the Fermi National Accelerator Laboratory near Batavia, Ill., are confronted with possible rescue situations in extremely cold temperatures because of the presence of thousands of gallons of supercold liquids, called cryogens, as cold as 450 degrees below zero.
Fermilab, as it is called, is engaged in high-energy physics research. The main atomic-particle accelerator is in a circular tunnel 20 feet underground and 4 miles in circumference.
Fermilab photos.
Like a giant slingshot, the Fermilab accelerator swings special tiny particles faster and faster around the ring—up to 50,000 times each second. Magnets are used to pull the particles into a circular path and accelerate them.
When maximum energy builds up, the particles are thrown out of the ring and along the connecting straight track. By throwing particles against different atomic nucleii and noting what happens, scientists are able to learn more about the nature of matter and energy.
Tremendous amounts of energy, costing about $1 million a month, are needed to run the accelerator. A new system now being installed features superconducting magnets and the cryogenic liquids. The supercold temperatures will reduce electrical resistance. Then higher energy levels can be built up at lower cost.
But what happens if an accident occurs and the cryogenic liquids spill? The fire department gets the call.
Cryogens
The cryogens are liquid helium and liquid nitrogen, because they remain liquid even at the lowest temperatures. A rupture of the system would result in an immediate and extreme drop in temperature within the 12-foot-diameter tunnel. A vapor cloud would quickly form, and normal oxygen levels would be reduced by the released helium and nitrogen.
Technicians working in the tunnel will be equipped with emergency escape masks which would normally enable them to reach a safe exit ahead of the spreading oxygen deficiency and dropping temperatures. But a technician working in the vicinity of the rupture could be injured or disoriented and require prompt rescue.
There are 26 service buildings at ground level, spaced at equal distances around the accelerator ring. These buildings each have access passages down to the tunnel and would be the entry point for the fire department. Large exhaust fans and input fans are also at alternate service buildings. The fans will assist in purging the tunnel of nitrogen and helium during a spill incident.
No data
To our knowledge, however, there are no test data available concerning operation of SCBA, two-way radios and protective clothing at extreme low temperatures. Present data cover only temperatures down to 40 degrees below zero that could be experienced due to weather.
Lower temperatures may require the development of specialized equipment. The laboratory has authorized some testing to explore the extent of our problem. An existing prototype tunnel, approximately 200 feet long, has been authorized for our use and is being instrumented with temperature and oxygen analyzers, TV cameras, recorders and other equipment. The tunnel has distribution piping and nozzles to allow controlled liquid nitrogen spills.
Our intent is to discover the physiological limitations and hazards of operating in such a hostile atmosphere. Laboratory cryogenic and environmental specialists are working with the fire department.
We would appreciate information from any readers who may have knowledge concerning the handling of cryogen spills in confined areas. Contact me at Fermilab, P.O. Box 500, Batavia, Ill. 60510, or phone 312-840-3428.