Problem Fuels

As the fuels of the space and atom age get more powerful, they also get harder to handle. Last week General Bernard Schriever, new chief of the Air Forces Research and Development Command, announced that liquid hydrogen, until recently hardly more than a laboratory curiosity, is being produced in considerable quantities as a rocket fuel. Liquid hydrogen is tricky stuff; it boils at minus 423DEG F., only about 37DEG above absolute zero. If it is not stored in elaborately insulated containers, it quickly turns to hydrogen gas, and a small amount of the gas makes a dangerous explosive mixture with the oxygen in the air.

But liquid hydrogen's virtues more than make up for its faults. When it is burned with liquid oxygen, the combination gives 40% more thrust than an equal amount of kerosene and oxygen. This improvement has a disproportionate effect on a rocket's efficiency, would more than double its payload.

No hydrogen-oxygen rocket of appreciable size has flown so far, but for a year Aerojet-General Corp. has been ground-testing hydrogen rocket motors at its Sacramento plant. Some tests have yielded more than 100,000 Ibs. of thrust. The treacherous new fuel burns cleanly and smoothly, and it is not as hard to store and get along with as some doubters feared.

Perverse Plutonium. Another problem fuel is plutonium, which may some day become the principal source of nuclear fission energy. Last week the Argonne National Laboratory dedicated its new $4,000,000 Fuel Fabrication Facility, whose principal job is to make fractious plutonium behave.

Plutonium is found in nature only in tiny traces. But when fissionable U-235 is burned in a nuclear reactor with the U-238 that forms the bulk of natural uranium, some of the neutrons that it sends out are captured by the U-238 atoms, turning them into plutonium (Pu-239). The plutonium can then be separated from uranium by a comparatively simple chemical process. If the reactor is made right, it "breeds," i.e., it makes more plutonium than it burns U-235. Used as fuel in turn, the new-made plutonium breeds even faster, making good nuclear fuel out of a blanket of inert uranium surrounding the reacting core. This breeding process is exciting to nuclear engineers because U-235 is scarce (only 0.7% of natural uranium) and will always be expensive. Plutonium made from U-238 may prove much cheaper.

But plutonium is about the most perverse material yet known to man. As a metal it is preposterous; while being heated to its rather low melting point (1184DEG F.), it passes through six different crystalline forms, expanding and contracting as much as 8.9% of its volume. It warps and distorts itself, disrupting anything to which it is attached. Because of this, Argonne Lab has given up trying to use pure plutonium in reactors, is making fuel elements out of plutonium alloyed or combined with other materials.

Dreadful Poison. Plutonium must be handled as if it were thousands of times more toxic than the deadliest poison, which it is: it is strongly radioactive, and if a microscopic amount of it gets into the human body it causes dreadful damage. Exposed to air, it oxidizes quickly, and the oxide floats off as a deadly, impalpable dust. If it is machined in air, the shavings burst spontaneously into flame, giving off clouds of deadly smoke.

Argonne's new facility contains a series of airtight compartments. Each will be equipped with miniature machines and filled with helium to prevent spontaneous combustion. The ingots of plutonium, about the size of a matchbox, will be handled by remote control, or through the 1,576 "glove ports," where the workers put their hands into long rubber gloves fitted to holes in the glass viewing panels.

Even when plutonium is stored in a carefully designed container, workers live close to catastrophe. Each small chunk of plutonium must be kept a respectful distance from the others, lest they combine to form the critical mass that sets off an atomic reaction. Even a human body in the wrong place can reflect enough neutrons into a chunk of plutonium to set off a chain reaction that could kill everyone in the lab with a blast of radiation.

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