On a December afternoon in Chicago during the middle of World War II,scientists cracked open the nucleus at the center of the uranium atom and turned nuclear mass into energy over and over again.


They did this by creating for the first time a chain reaction inside a new engineering marvel:the nuclear reactor.

他們創(chuàng )造了在世界上尚屬首次的連鎖反應工程新奇跡:核反應爐

Since then, the ability to mine great amounts of energy from uranium nuclei has led some to bill nuclear power as a plentiful Utopian source of electricity.


A modern nuclear reactor generates enough electricity from one kilogram of fuel to power an average American household for nearly 34 years.


But rather than dominate the global electricity market,nuclear power has declined from an all-time high of 18% in 1996 to 11% today.


And it's expected to drop further in the coming decades.


What happened to the great promise of this technology?


It turns out nuclear power faces many hurdles,including high construction costs and public opposition.


And behind these problems lie a series of unique engineering challenges.


Nuclear power relies on the fission of uranium nuclei and a controlled chain reaction that reproduces this splitting in many more nuclei.


The atomic nucleus is densely packed with protons and neutrons bound by a powerful nuclear force.


Most uranium atoms have a total of 238 protons and neutrons,but roughly one in every 140 lacks three neutrons,and this lighter isotope is less tightly bound.


Compared to its more abundant cousin,a strike by a neutron easily splits the U-235 nuclei into lighter, radioactive elements called fission products,in addition to two to three neutrons,gamma rays,and a few neutrinos.