Low-background steel
Encyclopedia
Low-background steel is steel
produced prior to the end of World War II
. Following Atomic bombing of Hiroshima and Nagasaki, and the nuclear weapons testing during the Cold War
, world background radiation
levels increased substantially. Steel produced during or after this testing became contaminated
with radionuclide
s and consequently, is unsuitable for certain radiation-sensitive purposes.
, steel was produced using the Bessemer process
, in which air is blown into a blast furnace
in order to convert Pig iron
into steel. Since the mid-20th century, the Bessemer process has been supplanted by the BOS process
, which uses pure oxygen instead of air.
Both processes are susceptible to contamination from airborne dust. Present-day dust carries radionuclides, particularly cobalt 60
, which are deposited in the steel, making it weakly radioactive.
s, medical applications (Whole body counting
and Lung counter
s) and physics applications (photonics
) frequently require an extremely low radiation environment, called a Low background counting chamber. A low background counting chamber is a room built with extremely heavy radiation shielding made from low-background steel.
s and the German fleet scuttled at Scapa Flow
.
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.
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
produced prior to the end of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. Following Atomic bombing of Hiroshima and Nagasaki, and the nuclear weapons testing during the Cold War
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
, world background radiation
Background radiation
Background radiation is the ionizing radiation constantly present in the natural environment of the Earth, which is emitted by natural and artificial sources.-Overview:Both Natural and human-made background radiation varies by location....
levels increased substantially. Steel produced during or after this testing became contaminated
Radioactive contamination
Radioactive contamination, also called radiological contamination, is radioactive substances on surfaces, or within solids, liquids or gases , where their presence is unintended or undesirable, or the process giving rise to their presence in such places...
with radionuclide
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
s and consequently, is unsuitable for certain radiation-sensitive purposes.
Radionuclide contamination
From 1856 until the mid-20th centuryHistory of the modern steel industry
The history of the modern steel industry began in the late 1850s, but since then steel has been basic to the world's industrial economy. This article is intended only to address the business, economic and social dimensions of the industry, since the bulk production of steel began as a result of...
, steel was produced using the Bessemer process
Bessemer process
The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855. The process was independently discovered in 1851 by William Kelly...
, in which air is blown into a blast furnace
Blast furnace
A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.In a blast furnace, fuel and ore and flux are continuously supplied through the top of the furnace, while air is blown into the bottom of the chamber, so that the chemical reactions...
in order to convert Pig iron
Pig iron
Pig iron is the intermediate product of smelting iron ore with a high-carbon fuel such as coke, usually with limestone as a flux. Charcoal and anthracite have also been used as fuel...
into steel. Since the mid-20th century, the Bessemer process has been supplanted by the BOS process
Basic oxygen steelmaking
Basic oxygen steelmaking , also known as Linz-Donawitz-Verfahren steelmaking or the oxygen converter process is a method of primary steelmaking in which carbon-rich molten pig iron is made into steel. Blowing oxygen through molten pig iron lowers the carbon content of the alloy and changes it into...
, which uses pure oxygen instead of air.
Both processes are susceptible to contamination from airborne dust. Present-day dust carries radionuclides, particularly cobalt 60
Cobalt 60
Cobalt 60 is a Front 242 side project featuring Front 242's Jean-Luc de Meyer and Dominique Lallement. They are an electro-industrial/EBM group, though they frequently use guitars, an uncommon feature among artists of the genre...
, which are deposited in the steel, making it weakly radioactive.
Applications
Certain techniques and devices require very low radiation materials. Geiger counterGeiger counter
A Geiger counter, also called a Geiger–Müller counter, is a type of particle detector that measures ionizing radiation. They detect the emission of nuclear radiation: alpha particles, beta particles or gamma rays. A Geiger counter detects radiation by ionization produced in a low-pressure gas in a...
s, medical applications (Whole body counting
Whole body counting
In Health Physics Whole body counting, refers to the measurement of radioactivity within the human body. The technique is only applicable to radioactive material that emit gamma rays, although in certain circumstances, beta emitters can be measured also....
and Lung counter
Lung counter
A Lung counter is a system consisting of a radiation detector, or detectors, and associated electronics that is used to measure radiation emitted from radioactive material that has been inhaled by a person and is sufficiently insoluble as to remain in the lung for weeks, months or years.Often, such...
s) and physics applications (photonics
Photonics
The science of photonics includes the generation, emission, transmission, modulation, signal processing, switching, amplification, detection and sensing of light. The term photonics thereby emphasizes that photons are neither particles nor waves — they are different in that they have both particle...
) frequently require an extremely low radiation environment, called a Low background counting chamber. A low background counting chamber is a room built with extremely heavy radiation shielding made from low-background steel.
Sources
Naval vessels constructed prior to the Cold War are a primary source of low-background steel. Chief among these are reserve fleetReserve fleet
A reserve fleet is a collection of naval vessels of all types that are fully equipped for service but are not currently needed, and thus partially or fully decommissioned. A reserve fleet is informally said to be "in mothballs" or "mothballed"; an equivalent expression in unofficial modern U.S....
s and the German fleet scuttled at Scapa Flow
Scuttling of the German fleet in Scapa Flow
The scuttling of the German fleet took place at the Royal Navy's base at Scapa Flow, in Scotland, after the end of the First World War. The High Seas Fleet had been interned there under the terms of the Armistice whilst negotiations took place over the fate of the ships...
.
Decreasing background radiation
World anthropogenic background radiation levels peaked at 0.15 mSvSievert
The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...
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.