What Went Wrong?

Tales from the Nuclear Age

Copyright© 2011 by Charles Glassmire

 Sept. 2, 2011

 What went Wrong?

           To the astonishment of the scientific community, the Bravo shot of the 1954 Operation Castle had gone very wrong. Expecting a detonation magnitude of 3 to 5 megatons from this early thermonuclear device, the actual shot had measured out at over 15 megatons. The generated debris cloud had become many times greater in size than calculated and, together with an unexpected wind shift before the shot, had spread fallout eastward into some of the populated Marshall Islands of Rongelap, Rongerik and others. Test buildings had been destroyed, measuring instruments vaporized, abandoned ships sent to the bottom of the Bikini lagoon, 28 U.S. service men on the Rongerik weather station had been exposed, a Japanese fishing boat had been contaminated (later resulting in a fisherman’s death), and several hundred Marshallese received doses of radiation much higher than permissible levels.

          Some 200 of these Rongelap natives had been moved south to escape the fallout for safe treatment to Kwajalein Island. They abandoned their fallout-contaminated homes and belongings, and now, being temporary wards of the U.S. government, were a population without a country.

          Why was the Bravo shot three times more powerful than expected? The answer lies in the assumptions made by the Los Alamos designers regarding an isotope of the element Lithium, called Lithium seven ( 7Li )

         First we must note that a thermonuclear weapon is really two weapons in one. An “ordinary” atomic bomb is first set off and the heat and X-rays from this bomb are used to set off the second thermonuclear weapon, causing the hydrogen to fuse and releasing copious energy.

          To put Hydrogen gas into a Hydrogen Bomb, the gas must first be condensed to cryogenic temperatures. The first H Bomb test (Ivy Mike) had successfully done this, but the equipment to keep the gas cold was enormous, heavy, and cumbersome. No way could this approach ever become a usable weapon.

          So on this second test (Castle Bravo), the Hydrogen was supplied as a solid chemical called Lithium Deuteride, using heavy Hydrogen (called “Deuterium”). It didn’t need to be kept cold, and Lithium was an especially nice choice to be in the bomb because it has a very low binding force holding its nucleus together. Thus its nucleus is likely to break apart and give up extra energy to the detonation.

         But there was a “gotcha”.

          About 7 percent of natural lithium is the lithium 6 isotope (6Li), and 92 percent is the Lithium 7 isotope (7Li). Lithium 6 is expensive to make, but is more desirable since it was considered to fission easily in the detonation. So the Lithium Deuteride for the test was enriched to 40% Li 6 at great expense. The designers assumed Li 7 didn’t enter into the reaction much at all.

          Big mistake.

          Unknown at the time, it turns out Li 7 also fissions when hit with a neutron, giving off an alpha particle, a tritium nucleus and another neutron! The tritium (which is very heavy Hydrogen) then fuses with the deuterium and hydrogen floating around, adding to the fusion power released in the explosion! In addition, the free neutron increased the neutron flux available. This additional neutron flux then increased the fissions in the atomic bomb part of the detonation, releasing more fission power to the detonation!

          So failing to account for the behavior of the Lithium 7 isotope added severely to the released power of the thermonuclear explosion and also increased the amount of fallout generated. The Hydrogen reaction doesn’t produce any fission products. The fission products come from the atomic bomb part of the device, when atoms split apart creating other lighter radioactive atoms. The presence of higher neutron flux makes more fissions and generates more radioactive fallout.

          Perhaps there is some lesson here in the stumbling progression of human endeavors, especially among those who dare to meddle with the fundamental forces of the universe.

          As to the migration of the innocent Rongelap population, their journey is ongoing and will be continued in the next installment…

 (to be continued …)

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2 Responses to “What Went Wrong?”

  1. Charles Glassmire Says:

    why is there an ad/link at the bottom of my post for oil dispersants? This is not part of my blog and should not be used by anyone reading my blog post called “What went Wrong”. This link was not entered with my permission and should be deleted.
    Charles Glassmire

  2. nikkitravis77 Says:

    Explanation of the ads on your page from a fellow blogger:

    The site is part of the WordAds program and has elected to show ads to earn money from their site.
    The site is one of the sites hosted on WordPress.com that is on their free plan. They run ads on these sites to help cover costs but these types of ads are run sparingly in an attempt to interfere as little as possible with the experience of reading a site.

    In both of the above cases, the ad you saw could be coming from a number of ad partners. The ads change depending on factors like your location and the type of site you are visiting.

    If you are a WordPress.com user and you would like to permanently remove all ads from your site, please take a look at their paid plans. Otherwise you are stuck with the ads.

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