Low-background steel

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Low-background steel, also known as pre-war steel, pre-atomic steel, or pre-nuclear steel, [1] [2] is any steel produced prior to the detonation of the first nuclear bombs in the 1940s and 1950s. Typically obtained from scrapped ships, salvaged shipwrecks, and other steel artifacts of this era, it is often used as a shielding material for particle detectors and whole-body counting equipment because more modern steel is contaminated with traces of nuclear fallout. [3] [4] Other low-background materials, such as ancient lead, are sometimes used for especially sensitive equipment.

Contents

History and rationale

Schema Bessemer metallurgie.svg
In the Bessemer process, air is forced upward into the converter.
Schema LD metallurgie.svg
In the basic oxygen steelmaking (BOS) process, oxygen gas is introduced from above.
Fabrication Flight, fixing the fleet (6360305).jpg
The thorium used in gas tungsten arc welding is one source of radioactive contamination of steel.
Body counting room at Rocky Flats Plant.jpg
A body counting room at the Rocky Flats Plant near Denver, Colorado, made entirely from pre-World War II steel, photographed in 1985
ShieldandCryostatXENON100.jpg
The shield of the time projection chamber of the XENON100 dark matter experiment utilizes ancient lead.

From 1856 until the mid 20th century, steel was produced in the Bessemer process, where air was forced into Bessemer converters converting the pig iron into steel. By the mid-20th century, many steelworks had switched to the BOS process, which uses pure oxygen instead of air. However, as both processes use atmospheric gas, they are susceptible to contamination from airborne particulates. Present-day air carries radionuclides, such as cobalt-60, which are deposited into the steel, giving it a weak radioactive signature. [5] Another source of radioactive contamination was the coating of steel cauldrons in cobalt-60 in order to monitor wear. [6] [7] Steel that would otherwise be expected to be low-background can itself be contaminated due to thorium contained in welding rods, such as those used in gas tungsten arc welding. [4] [8]

World anthropogenic background radiation, caused by atmospheric nuclear testing, peaked at a level 0.11  mSv/yr (4%) above the natural 2.40 mSv/yr. It began to fall in 1963, when the Partial Nuclear Test Ban Treaty was enacted, and by 2008 it had decreased to only 0.005 mSv/yr above natural levels. [9] This has made special low-background steel no longer necessary for most radiation-sensitive uses, as new steel now has a low enough radioactive signature. [5] [10] Some demand remains for the most radiation-sensitive uses, such as Geiger counters and sensing equipment aboard spacecraft. [11] For the most sensitive equipment, even low-background steel can be too radioactive, and other materials like high-purity copper may be used. [4]

At the end of World War I, the German Navy scuttled around 50 ships in Scapa Flow instead of turning them over to the British Royal Navy. These ships have historically been one source of low-background steel. [11] [12] In cases where World War II–era shipwrecks in and near the relatively shallow Java Sea and western South China Sea have been illegally scavenged, it has been suggested that the target is low-background steel. [13] However, some–including Andrew Brockman, a maritime crime researcher and archaeologist–argue that conventional salvage is more likely. [6] [10]

Other low background materials

The ancient Romans used lead to produce parts for their ships, including anchor stocks like these. (Antiquarium Turritano, 2015) Porto Torres - Antiquarium Turritano (50).JPG
The ancient Romans used lead to produce parts for their ships, including anchor stocks like these. (Antiquarium Turritano, 2015)

Some specialized particle detectors, including CUORE, XENON100, and Canfranc Underground Laboratory, have used low-background lead for shielding. [14] [15] [16] This is sourced from ancient Roman lead, some of which is sourced from ancient Roman shipwrecks. [17] [18] Ancient lead has lower radiation levels than freshly refined lead because lead ore is naturally radioactive, and after processing, it still contains lead-210, a radioactive isotope of lead which has a half-life of 22 years. Ancient lead has had enough time for the lead-210 to decay to the point where it is "totally absent", so the lead can be used in highly sensitive equipment. [17] [19]

Cultural impact

In 2025, technology experts such as Rajiv Pant and John Graham-Cumming began to use low-background steel as a metaphor to describe the practice of archiving web content that existed before 2022 in an effort to preserve information that was produced by humans without "contamination" from large language models such as ChatGPT. [20] [21] [22] [23] [24]

See also

References

  1. ↑ Manohari, M.; Mathiyarasu, R.; Rajagopal, V.; Meenakshisundaram, V.; Indira, R. (2011). "Calibration of phoswich-based lung counting system using realistic chest phantom" . Radiation Protection Dosimetry. 144 (1–4): 427–432. doi:10.1093/rpd/ncq325. PMID   21044995.
  2. ↑ Mahaffey, James (2009). Atomic Awakening: A New Look at the History and Future of Nuclear Power. pp. 226–227.
  3. ↑ Aaron, D. Jayne; Berryman, Judith (1997). "Rocky Flats Plant, Emergency Medical Services Facility". U.S. Department of Energy, Office of Legacy Management. HAER No. CO-83-S (Rocky Flats Plant, Building 122). Archived from the original on 8 June 2019.
  4. 1 2 3 Mandelbaum, Ryan F. (19 December 2017). "How Physicists Recycled WWII Ships And Artillery To Unlock The Mysteries Of The Universe". Gizmodo. Archived from the original on 27 May 2023. Retrieved 25 May 2023.
  5. 1 2 Adams, Cecil (10 December 2010). "Is steel from scuttled German warships valuable because it isn't contaminated with radioactivity?". The Straight Dope. Archived from the original on 16 September 2015. Retrieved 18 January 2011.
  6. 1 2 Oelbaum, Jed (10 May 2018). "The Worldwide Scavenger Hunt For Vintage, Low-Radiation Metals". Good.is. Archived from the original on 27 May 2023. Retrieved 27 May 2023.
  7. ↑ Prepared by the Secondary Reachback Data Mining Group (July 2013). 60Co Contamination in Iron and Steel (Report). U.S. Department of Homeland Security. pp. 12–13. Retrieved 2025-12-23.
  8. ↑ "Thorium Containing Welding Rod (1990s)". Museum of Radiation and Radioactivity. Retrieved 2026-01-27.
  9. ↑ Sources and Effects of Ionizing Radiation. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) (Report). Vol. I. New York: United Nations. 2010 [2008]. p. 6. ISBN   978-92-1-142274-0. UNSCEAR 2008 Report. Archived from the original on 2019-07-16. Retrieved 2015-02-18.
  10. 1 2 Jones, Laurence; Berry, Jessica; Richardson, Giles (2025-05-20). "Is pre-nuclear steel behind WWII ship targeting?". UK Defence Journal. Retrieved 2026-01-27.
  11. 1 2 Chapman, Kit. "Low-background steel". Chemistry World. Retrieved 2025-12-20.
  12. ↑ Thomas, Ling (2025-07-02). "Why WWII shipwrecks could soon help solve a cosmic mystery". BBC Science Focus Magazine. Retrieved 2025-12-20.
  13. ↑ "The world's biggest grave robbery: Asia's disappearing WWII shipwrecks". The Guardian. 3 November 2017. Archived from the original on 22 May 2022. Retrieved 26 April 2024.
  14. ↑ Andrews, Robin George (2019-10-25). "Why the Search for Dark Matter Depends on Ancient Shipwrecks". The Atlantic. Retrieved 2025-08-30.
  15. ↑ "Roman lead will shield CUORE experiment". CERN Courier. 2010-06-07. Retrieved 2025-12-23.
  16. ↑ Behrens, Annika (2014). Light Detectors for the XENON100 and XENON1T Dark Matter Search Experiments (PDF) (PhD of Natural Sciences thesis). Zurich University of Applied Sciences. p. 20. Retrieved 2026-01-26.
  17. 1 2 Moskowitz, Clara (18 December 2013). "Ancient Roman Metal Used for Physics Experiments Ignites Science Feud". Scientific American. Springer Nature. Retrieved 8 December 2025.
  18. ↑ "Lead from a Roman ship to be used for hunting neutrinos". Interactions. 2010-04-15. Retrieved 2026-01-27.
  19. ↑ Alessandrello, A.; Cattadori, C.; Fiorentini, G.; Fiorini, E.; Gervasio, G.; Heusser, G.; Mezzorani, G.; Pernicka, E.; Quarati, P.; Salvi, D.; Sverzellati, P.; Zanotti, L. (1991-07-02). "Measurements on radioactivity of ancient roman lead to be used as shield in searches for rare events". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 61 (1): 106–117. doi:10.1016/0168-583X(91)95569-Y. ISSN   0168-583X.
  20. ↑ Sparkes, Matthew (2025-07-21). "Should we preserve the pre-AI internet before it is contaminated?". New Scientist. Retrieved 2026-01-27.
  21. ↑ Barr, Alistair (2025-06-04). "Thanks to ChatGPT, the pure internet is gone. Did anyone save a copy?". Business Insider. Retrieved 2026-01-27.
  22. ↑ Edwards, Benj (2025-06-18). "Scientists once hoarded pre-nuclear steel; now we're hoarding pre-AI content". Ars Technica. Retrieved 2026-01-27.
  23. ↑ Palmer, Shelly (2025-06-19). "We used to hoard pre-nuclear steel". SaskToday.ca. Retrieved 2026-02-01.
  24. ↑ Claburn, Thomas (2025-06-15). "ChatGPT polluted the world forever, like the first atom bomb". The Register. Archived from the original on 2026-01-26. Retrieved 2026-02-01.
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