I am apparently one of the only people who actually enjoyed The Amazing Spider-Man 2.  The movie holds a 53% critic approval rating on Rotten Tomatoes, with the consensus that the movie “suffers from an unfocused narrative and an overabundance of characters.”  (Yet the deplorable Spider-Man 3 fared better, earning a 63% approval rating…)  OK, fine.  I can buy that there was room for improvement in the story telling.

One flaw that could have used some work?  The mishandling of plutonium.

Spider-Man first swings on screen as he’s taking on Aleksei Sytsevich, a Russian mobster who decided to hijack an Oscorp truck carrying plutonium because… well, he’s a villain and that’s what villains do.  As his two accomplices begin to unload the plutonium canisters, the truck computer alerts, “Warning, plutonium 2-3-8 is a radioactive material and is highly explosive.”

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But here’s the thing: plutonium-238 isn’t highly explosive.

In chemistry, you learn that atoms are made of protons, neutrons, and electrons.  The number of protons in an atom determines what element it is.  While all atoms within a particular element contain the same number of protons, they may not contain the same number of neutrons.  These are called isotopes.  Isotopes within an element are chemically identical, but have different nuclear properties.  For example, carbon-12 (six protons and six neutrons) is a stable isotope, while carbon-14 (six protons and eight neutrons) is radioactive and beta decays into nitrogen-14.

Plutonium is no exception.  There are no stable isotopes of plutonium, but there are several unstable isotopes.  The plutonium mentioned in The Amazing Spider-Man 2 is plutonium-238, consisting of 94 protons and 144 neutrons.  Plutonium-238 is an alpha emitter with a half-life of 87.7 years, decaying to uranium-234 (and eventually turning into the stable lead-206).  Because of its high decay heat, plutonium-238 is often used in radioisotope thermoelectric generators, which you may recognize from The Martian.  Plutonium-238 is not used in explosives.

It’s possible the film-makers meant to refer to plutonium-239 (94 protons and 145 neutrons), which is the plutonium isotope used in nuclear weapons.  Weapons-grade plutonium contains greater than 90% of plutonium-239.  In a plutonium nuclear weapon, explosives placed on the surface of the weapon are detonated, forcing the plutonium inward.  With the volume decrease and the density increase, the plutonium material hits critical mass, creating an exponentially growing nuclear chain reaction, and thus an explosion.  That’s right- plutonium-239 isn’t likely to be explosive on its own, but at least it would have had a better claim in the movie than plutonium-238.

While plutonium-238 isn’t used for nuclear weapons, we should still appreciate that Spider-Man took the time to prevent the samples from smashing on the ground, even if he did casually toss the plutonium samples while whistling his theme song.  Can you imagine Peter dropping one of those containers and contaminating the area?  The NRC would have had a field day.

Andrew Garfield;Paul Giamatti

Keep calm and science on.

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