Low-background steel is any steel produced prior to the detonation of the first atomic bombs in the 1940s and 1950s. With the Trinity test and the Atomic bombing of Hiroshima and Nagasaki in 1945, and then subsequent nuclear weapons testing during the early years of the Cold War, background radiation levels increased across the world. Modern steel is contaminated with radionuclides because its production used atmospheric air. Low background steel is so-called because it does not suffer from such nuclear contamination. This steel is used in devices that require the highest sensitivity for detecting radionuclides.

From 1856 until the mid 20th century, steel was produced in the Bessemer process where air was forced into blast furnaces 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.^[1]

World anthropogenic background radiation levels peaked at 0.15 mSv above natural levels in 1963, the year that the Partial Nuclear Test Ban Treaty was enacted. Since then, anthropogenic background radiation has decreased exponentially to 0.005 mSv per year above natural levels.^[2]

However cobalt-60 still contaminates modern steel because it has been recycled through the scrap metal supply chain.^[3]

Devices that require low-background steel include:

• Geiger counters
• Medical apparatus: whole body counting and lung counters
• Scientific equipment: photonics
• Aeronautical and space sensors

As these are detecting radioactive emissions, they require an extremely low radiation environment in order to work correctly. Low background counting chambers are made from low-background steel with extremely heavy radiation shielding. They are used to detect the minutest nuclear emissions.^[4]

The primary source of low-background steel are ships that have been under water since before the Trinity test, most famously the scuttled German WWI battleships in Scapa Flow. ^[5]

Vorlage:Reflist

1. ↑ Cecil Adams: Is steel from scuttled German warships valuable because it isn't contaminated with radioactivity? In: The Straight Dope. 10. Dezember 2010; abgerufen im 1. Januar 1. 
2. ↑ Vorlage:Citation
3. ↑ Vorlage:Citation
4. ↑ D. Jayne Aaron, Judith Berryman: Rocky Flats Plant, Emergency Medical Services Facility - HAER No. CO-83-S (Rocky Flats Plant, Building 122). U.S. Department of Energy, Office of Legacy Management, 1997; abgerufen im 1. Januar 1. 
5. ↑ Daniel Allen Butler: Distant Victory: the Battle of Jutland and the Allied Triumph in the First World War. Praeger Security International (Greenwood Publishing Group), Westport, Connecticut, USA 2006, ISBN 0-275-99073-7, S. 229 (google.com).