Low-background steel

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A body counting room at the Rocky Flats Plant near Denver, Colorado, made entirely from pre-World War II steel, photographed in 1985 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

Low-background steel, also known as pre-war steel [1] and pre-atomic steel, [2] is any steel produced prior to the detonation of the first nuclear bombs in the 1940s and 1950s. Typically obtained from ships (either as part of regular scrapping or shipwrecks) and other steel artifacts of this era, it is often used for modern particle detectors because more modern steel is contaminated with traces of nuclear fallout. [3] [4]

Contents

Some specialized particle detectors, including CUORE and Canfranc Underground Laboratory, have used low-background lead for shielding. [5]

Rationale

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. [6] Another source of radioactive contamination was the coating of steel cauldrons in cobalt-60 in order to monitor wear. [7] Steel that would otherwise be expected to be low-background can itself be contaminated due to thorium in welding rods. [4]

Present day

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. [8] 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. [6] Some demand remains for the most radiation-sensitive uses, such as Geiger counters and sensing equipment aboard spacecraft. For the most sensitive equipment, even low-background steel can be too radioactive, and other materials like high-purity copper may be used. [4]

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. [9] Andrew Brockman, a maritime crime researcher and archaeologist, argues that conventional salvage is more likely. [7]

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. 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. ↑ Andrews, Robin George (2019-10-25). "Why the Search for Dark Matter Depends on Ancient Shipwrecks". The Atlantic. Retrieved 2025-08-30.
  6. 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.
  7. 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.
  8. ↑ 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.
  9. ↑ "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.
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