Low-background steel and ancient lead are valuable as radiation shields. Acquiring them is complicated.
The first detonation of an atomic bomb changed the world irrevocably. Rather than remaining contained in the New Mexico desert, the effects of the Trinity Test of July 16, 1945, reverberated across the globe and across history. Within a month, the U.S. had dropped nuclear bombs on the Japanese cities of Hiroshima and Nagasaki, bringing World War II to an end and ushering in the nuclear age. In so many ways, that day is still with us. In a literal sense, it still lingers in the air we breathe.
Starting with that first detonation and increasing with each subsequent nuclear bomb explosion, background radiation seeped into our atmosphere. It’s not enough to make us sick, but it is enough to affect specialized scientific equipment that relies on the ability to measure radiation. If the machines themselves are made from irradiated materials, they won’t be as accurate as they need to be. For that reason, low-background steel and other pre-1945 metals are highly valuable for some pretty important projects. Because making steel involves forcing air into molten iron, any steel made after that first detonation contains background radiation, even if it uses pure oxygen. The best source of low-background steel is underneath the waves, in shipwrecks. There’s no shortage of those, but they come with caveats.
Sophisticated physics experiments that require radiation shields, radiation-detecting hospital equipment, and – though NASA has never confirmed this – it’s possible even space probes and satellites have relied on low-background steel from shipwrecks.
After World War I, the defeated Germans scuttled their High Sea Fleet in the waters of Scapa Flow in Scotland’s Orkney Islands. British sailors managed to get some of the ships to shore, but more than 50 sank. The value of this low-background steel would not be realized for decades, but after salvage efforts, plates from some of the sunken ships have been used in hospitals from Scotland to the U.S. There has even been conjecture that parts of the Scapa Flow ships ended up on Voyager 1 or Explorer 1, patrolling outer space. The scuttling of the German fleet was mostly peaceful, though nine Germans did die when the British opened fire trying to prevent the action.
Most ships containing low-background steel, however, had much more violent fates. Hundreds of ships are buried beneath the South China and Java seas, casualties of World War II battles. Buried with them are thousands of sailors. As many as 40 of those ships have been partially or totally destroyed, a Guardian investigation found. The process can take weeks, with divers carrying explosives down to the wrecks, attaching them and detonating them to break the ships into smaller chunks. Barges then use cranes to bring the chunks to the surface. As the practice is illegal, the crews pretend to be operating fishing vessels. In May, Malaysian authorities detained a Chinese-registered ship that had ammunition believed to be from the British HMS Prince of Wales and HMS Repulse onboard.
“You may as well just go into a war cemetery and dig it up. It’s no different to me, at all,” James Hunter, curator of naval heritage and archaeology at the Australian National Maritime Museum, told the Guardian about such harvesting.
Back to the Future
A positive development in so many ways, the amount of background radiation in the atmosphere has been steadily decreasing since the 1963 Partial Nuclear Test Ban Treaty dramatically decreased the number of atmospheric atomic bomb detonations. Levels are now roughly 5% of what they were 60 years ago. Assuming nuclear war and tests remain in the past, low-background steel will quickly lose its value, as all steel will once again be low-background steel. World War II shipwrecks might still be plundered, as scrap metal remains a valuable resource. What will remain highly valuable, though, is ancient lead.
Lead contains radioactive uranium isotopes. When it’s freshly mined is when it contains the most. Over time, it loses it radioactivity, but it can be hundreds of year before the lead is completely non-radioactive. Where can we find such lead? In shipwrecks, of course.
The University of Chicago has used lead ballast from the 18th-century Spanish galleon San Ignacio, which sunk off the Florida Keys in 1733, in physics experiments. Reaching back even further, Italy’s National Institute for Nuclear Physics used, with permission from the National Archaeological Museum, lead recovered from a Roman shipwreck off Sardinia as radiation shielding for experiments in its Cryogenic Underground Laboratory for Rare Events. Ancient lead has played a key role in the search for dark matter, and the use has not been without controversy.
“Underwater archaeologists see destruction of heritage as a loss of our past, our history, whilst physicists support basic research to look for answers we do not yet have,” Elena Perez-Alvaro, author of Underwater Cultural Heritage: Ethical Concepts and Practical Challenges, told SINC. “Are these experiments important enough to destroy parts of our past, to discover something about our future?” she said to Scientific American.
Her collaborator M. Fernando Gonzalez-Zalba believes they are.
“These experiments can reveal some of the most fundamental properties of the universe, and answer questions such as what are we and where we come from,” he told Scientific American. “I think it’s worth it.”