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Hamish Johnston: May 2008 Archives

The sad saga of the MAPLE nuclear reactors may have finally come to a close with today’s announcement from Atomic Energy of Canada (AECL) that the firm will no longer try to get the pair of reactors licensed to produce medical isotopes.

MAPLE was conceived in the 1980s as a replacement for AECL’s ageing NRX and NRU research reactors at Chalk River, Ontario. “M” stands for “multipurpose”, and the MAPLE was intended for both basic research as well as the commercial production of radioactive isotopes for medical and other applications.

Two MAPLE reactors were finally built at Chalk River in 2000, but it soon became apparent that they both suffered from serious safety problems associated with shoddy workmanship. As a result the facilities have never been granted full operational licences by the Canadian nuclear regulator.

AECL has also had safety problems with the 50-year old NRU, which had to be shutdown unexpectedly for about a month in 2007, leading to an international shortage of medical isotopes.

In the case of NRU, the Canadian government stepped in to restart the reactor — overruling its own regulator. AECL may be gambling that its move to scrap MAPLE may cause the government to pressure the regulator into approving the reactors.

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“Many of [Einstein’s] ground-breaking discoveries were blighted by mistakes, ranging from serious misconceptions in physics to blatant errors in mathematics”.

So says a promotional blurb for Einstein’s Mistakes: The Human Failings of a Genius, a new book from the American physicist and author Hans C Ohanian that will be published in September by W W Norton.

Ohanian has posted an eight-page taster of his work on the arXiv preprint server, in which he presents a “critical examination” of how Einstein went about proving his most famous equation E = MC2. All of these proofs, claims Ohanian, “suffer from mistakes”.

This is not the first time that Einstein’s proofs have come under scrutiny, with various detractors and supporters arguing since at least 1908 — three years after the equation was first derived.

Elsewhere in the world of Einstein biography, a letter on religion written in 1954 by the physicist to the German philosopher Eric Gutkind has come up for auction in London. “The word God is for me nothing more than the expression and product of human weakness…”, wrote Einstein who died the next year — and has presumably discovered whether or not this letter was a mistake.

The high Tc superconductivity community has been abuzz lately with the discovery of a growing number of iron-based materials that remain superconducting at temperatures as high as 55 K.

The first such material (fluorine-doped LaOFeAs) was reported by physicists in Japan earlier this year and has a transition temperature (Tc) of 26 K. Since then, researchers in China replaced the lanthanum (La) with samarium (Sm) and boosted Tc to 55 K. The Japanese team, meanwhile, put their material under pressure and increased Tc to 43 K.

Now, just as physicists are beginning to understand the mechanism behind these iron-based materials, scientists in Russia have come up with a new twist by replacing iron with nickel. They found that fluorine-doped LaONiBi is a superconductor with a Tc of 4K.

While this Tc is much lower than the iron-based materials, the team reports that LaONiBi has very similar structural and electronic properties as its iron-based cousins. This suggests that with a bit of fiddling with doping levels and other properties, the Tc could be boosted considerably.

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