the amount of cooling water in the reactor, leading operators to shut off the emergency core cooling system. The shutoff thus caused a number of the fuel rods to overheat.

In addition, the committee says early consideration should be given to "providing remotely controlled means for venting high points in the reactor system," such as the hydrogen bubble that formed during the accident.

Hendrie has told the Senate Sub­committee on Nuclear Regulation that NRC will "take whatever steps are necessary" to prevent further ac­

cidents. However, he says, the gov­ernment should examine the entire nuclear power regulatory framework rather than "just thinking of im­proved hardware or other technical fixes" as a means of preventing future accidents.

He is calling for a re-examination of the ability of nuclear plants to deal with emergencies, upgraded training for reactor operators, increased em­phasis on safety regulations in the steam-producing units of the power plants, and review of NRC licensing procedures. D

Chemical train derails and burns in Florida Fire and explosion followed the de­railment of 28 cars of a 118-car Louisville & Nashville train carrying 10,600 tons of chemicals over the Yellow River, 50 miles northeast of Pensacola, Fla., on Sunday morning, April 8.

As it lit up the desolate, swampy countryside between the towns of Crestview and Milligan, Fla., the ac­cident also may shed light on the state of chemical transport safety, the safety record of the L&N in particu­lar, inspection procedures of the Federal Railway Administration, and the status of safety recommendations of the National Transportation Safety Board.

Two acetone cars exploded and burned at once, also igniting liquid sulfur in one car. A third acetone car burned for 60 hours. Methanol was transshipped from two cars derailed on the burned-out wooden trestle, while all but 3000 gal burned in a third car. A phenol car hanging off the trestle began leaking slightly, as did a chlorine car thrown into the water

Firemen and L&N inspectors look over wreckage of derailed, burned train

and two of 17 anhydrous ammonia cars. Also derailed were a carbon tet­rachloride tanker and a urea car.

Chemtrec, the emergency response organization of the Manufacturing Chemists Association, was called by state civil defense in about 30 min­utes. On learning of the presence of a chlorine car, the Chemtrec team called in Chlorep, the emergency re­sponse team of the Chlorine Institute.

River water was pumped between skins of the phenol car to solidify the cargo and stop the leak. The 10-inch hole in the chlorine car was patched, and the car pulled from the river. The contents then were bled into pits lined with plastic film and filled with dilute caustic solution.

According to the Federal Railway Administration, in the 30 months preceding June 1978, L&N trains carrying hazardous cargo were in­volved in 121 accidents, with release of chemicals from 42 cars, causing 19 deaths, 71 serious injuries, and evac­uation of 7280 people in seven states.

Ironically, FRA had ordered a 30-mph speed limit on L&N trains carrying hazardous cargo over that Pensacola & Atlantic subdivision only three days before, but lifted it the next day after FRA officials had in­spected the track. L&N spokesmen say the derailed train was traveling at only 30 mph.

FRA administrator John Sullivan stepped up his criticism of the rail­road, however, blaming management for assembling such a long train of hazardous cargo. In February, he said L&N had the worst record of any railroad in the country in handling hazardous materials.

The National Transportation Safety Board has taken over the in­vestigation and may hold hearings. One item of interest will be whether the tank cars were equipped with head shields to prevent end puncture and with shelf couplers that would not puncture ends of other cars. D

Chains of magnetite found in some bacteria Like ancient mariners, some aquatic bacteria determine the direction in which they travel by carrying lode-stone compasses with them.

More precisely, they carry whole strings of lodestone compasses that enable them to sense the earth's magnetic field and orient their movement to it, says Richard B. Frankel of Massachusetts Institute of Technology and Richard P. Blake-more of the University of New Hampshire [Science, 203, 1355 (1979)].

The bacteria are from a yet-un­named class first discovered by Blakemore in 1975. They are magne-totactic; that is, they swim toward the north pole in a weak magnetic field (C&EN, May 8,1978, page 20). Since 1975, a number of bacterial species, both freshwater and marine, with this ability have been found in locations in the U.S. and in the Baltic Sea.

What Blakemore and Frankel have done now is to grow one strain of these bacteria under carefully con­trolled culture conditions and then examine the organisms by electron microscopy and Môssbauer spec­troscopy to see how they are able to sense the earth's magnetic field.

They find that the bacteria contain about 10 times the normal amount of iron. And this extra iron is in the form of cubes of magnetite, 50 nm on a side, strung together into chains, about 22 cubes long.

Magnetite, or lodestone, FesC^, is a common iron-containing mineral, which was used by early mariners to make compass needles. In bulk, it must be subjected to a large magnetic field before it becomes a permanent magnet so that all the dipole mo­ments in a sample become aligned. A 50-nm cube, however, has only a sin­gle dipole moment and is inherently a small, permanent magnet, Frankel says. Crystals greater than about 80 nm on a side have multiple dipole moments, and crystals smaller than about 40 nm do not have stable mag­netic moments and thus would make poor magnets, he says. It takes about 20 of these 50-nm cubes, working to­gether, to be able to detect a weak magnetic field such as the earth's.

The scientists are not certain what advantage this string of internal magnets gives to the bacteria that possess them. One possibility is that since at the latitudes where the bac­teria are found the earth's magnetic field points primarily down rather than north, the magnets may help the bacteria to swim toward bottom sediments, their best habitat. D

6 C&EN April 16, 1979