Heavy Water

[Subdeacon Joe]

Feb. 28 marks the anniversary of Operation Gunnerside,

 

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Those differences are subtle, but there is something heavy water does that normal water can’t. When fast neutrons released by the splitting of atoms (that is, nuclear fission) pass through heavy water, interactions with the heavy water molecules cause those neutrons to slow down, or moderate. This is important because slowly moving neutrons are more efficient at splitting uranium atoms than fast-moving neutrons. Since neutrons traveling through heavy water split atoms more efficiently, less uranium should be needed to achieve a critical mass; that’s the minimum amount of uranium required to start a spontaneous chain reaction of atoms splitting in rapid succession. It is this chain reaction, within the critical mass, that releases the explosive energy of the bomb. That’s why the Germans needed the heavy water; their strategy for producing an atomic explosion depended upon it.

The American scientists, in contrast, had chosen a different approach to achieve a critical mass. As I explain in my book, “Strange Glow: The Story of Radiation,” the U.S. atomic bomb effort used enriched uranium – uranium that has an increased concentration of the easily split uranium-235 – while the Germans used unenriched uranium. And the Americans chose to slow the neutrons emitted from their enriched uranium with more readily available graphite, rather than heavy water. Each approach had its technological trade-offs, but the U.S. approach did not rely on having to synthesize the extremely scarce heavy water. Its rarity made heavy water the Achilles’ heel of the German nuclear bomb program.

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The Norwegians were then able to sneak past sentries and find their way to the heavy water production room, relying on maps of the plant provided by Norwegian resistance workers. Upon entering the heavy water room, they quickly set their timed explosives and left. They escaped the scene during the chaotic aftermath of the explosion. No lives were lost, and not a single shot was fired by either side.

Outside the plant, the men backtracked through the ravine and then split into small groups that independently skied eastward toward the safety of neutral Sweden. Eventually, each made his way back to their Norwegian unit stationed in Britain.

The Germans were later able to rebuild their plant and resume making heavy water. Subsequent Allied bomber raids on the plant were not effective in stopping production due to the plant’s heavy walls. But the damage had already been done. The German atomic bomb effort had been slowed to the point that it would never be finished in time to influence the outcome of the war.

Today, we don’t hear much about heavy water. Modern nuclear bomb technology has taken other routes. But it was once one of the most rare and dangerous substances in the world, and brave soldiers – both British and Norwegian – fought courageously to stop its production.

 

[Trailrider #896]

Thor Heyerdahl, one of the Norwegian unit, went on to explore the Pacific on his boat Kon Tiki.  BTW "Heavy Water" is the source for deuterium oxide and tritium.  If you want more bang for the buck, you can make a fusion bomb...if you have a fission bomb to set it off!   I don't think either are SASS compliant.