Advanced Invention

Plans are afoot to reuse spent reactor fuel in the U.S. But the advantages of the scheme pale in comparison with its dangers

• Spent nuclear fuel contains plutonium, which can be extracted and used in new fuel.
• To reduce the amount of long-lived radioactive waste, the U.S. Department of Energy has proposed reprocessing spent fuel in this way and then “burning” the plutonium in special reactors.
• But reprocessing is very expensive. Also, spent fuel emits lethal radiation, whereas separated plutonium can be handled easily. So reprocessing invites the possibility that terrorists might steal plutonium and construct an atom bomb.
• The author argues against reprocessing and for storing the waste in casks until an underground repository is ready.

KITCHEN SINK HELIOSPHERE: If the solar wind is like a stream of water spreading out on a flat sink bottom, then the boundary where the flow breaks against onrushing soapy water (interstellar gas) is the termination shock (recently encountered by the spacecraft Voyager 2) and the region of slower-moving water beyond it is the heliosheath.
Courtesy of J.R. Jokipii

Hurtling through space 31 years after its launch, the Voyager 2 spacecraft has sent back the most detailed view yet of the shock wave that marks the thinning of the solar wind, the charged particles streaming from the sun.

Researchers say the crossing confirms that the heliosphere—the region swept out by the solar wind—is actually lopsided, perhaps due to a tilted magnetic field in local interstellar space.

The shock wave, or heliospheric termination shock, occurs when the supersonic wind thins to the point that it can no longer rebuff the denser haze of charged particles flowing through interstellar space. Instead, the solar wind suddenly collapses in on itself.