Low-background steel
Low-background steel is steel that was made before the first atomic bomb explosions in the 1940s. It is less radioactive than modern steel. It is used, for example, in particle or radiation detectors , which should have the lowest possible background effect .
background
Starting with the Trinity test and the atomic bombs being dropped on Hiroshima and Nagasaki and as a result of the nuclear weapons tests during the first years of the Cold War , radiation exposure increased worldwide.
Since steel is produced using fresh air, steel produced today is contaminated by radionuclides . Steel made before 1945 is free from this contamination. It is used in devices for precise measurements of radionuclides.
The most important source of low-background steel are ships that sank before the Trinity test, especially the ships of the German deep-sea fleet that were sunk in Scapa Flow by their crews in 1919 . Other (illegal) sources are in Malaysian and Indonesian waters.
Causes of Radionuclide Contamination
Both in steel production with the Bessemer pear , in which air is blown into the pig iron , and in the Linz-Donawitz process , which uses oxygen instead, air is used as the starting product, which is contaminated by fine dust. Nowadays there are radionuclides like Cobalt-60 in the air, which get into the steel during manufacture and give it a weakly radioactive signature.
Human-generated radioactivity reached its maximum in 1963, the year in which the Treaty on the Ban on Nuclear Weapons Tests in the Atmosphere, Space and Underwater was signed, at 0.15 mSv / a above natural radioactivity.
Modern steels are still contaminated with cobalt-60, because old steels, which have been produced since 1945 and are thus contaminated, end up in modern steel via recycling.
Other metals with low radioactivity
Also lead with particularly low radioactivity is used, for example. B. in lead castles to shield measuring devices for low level measurements. For the highly sensitive neutrino detectors of the CUORE experiment , 2000 year old, low- radiation lead from the cargo of a ship that sank off Sardinia was used.
Web links
Individual evidence
- ^ 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 , pp. 229 ( limited preview in Google Book search).
- ↑ Sources and Effects of Ionizing Radiation (UNSCEAR 2008 Report) Volume I, page 6.
- ↑ Reducing Risks in the Scrap Metal Industry - Sealed Radioactive Sources , International Atomic Energy Agency (IAEA), 2005, pages 2-6 (PDF).
- ↑ "Low-radiation lead - up to 5 mBq / g"
- ↑ "Lead building blocks in a modular system [... On request, low-radiation lead for shielding measuring devices for low level measurements"]
- ↑ Lead from an antique ship protects high-tech experiment