Radioactive contamination

For example, if a radionuclide used in nuclear medicine is spilled (accidentally or, as in the case of the Goiânia accident, through ignorance), the material could be spread by people as they walk around.

In nuclear accidents, a measure of the type and amount of radioactivity released, such as from a reactor containment failure, is known as the source term.

The United States Nuclear Regulatory Commission defines this as "Types and amounts of radioactive or hazardous material released to the environment following an accident.

When radioactive materials are concentrated to a detectable level outside a containment, the area affected is generally referred to as "contaminated".

In the case of liquids, this is by the use of high integrity tanks or containers, usually with a sump system so that leakage can be detected by radiometric or conventional instrumentation.

Where the material is likely to become airborne, then extensive use is made of the glovebox, which is a common technique in hazardous laboratory and process operations in many industries.

A particular problem is encountered with naturally generated radon gas which can affect instruments that are set to detect contamination close to normal background levels and can cause false alarms.

Naturally occurring radioactive materials (NORM) can be brought to the surface or concentrated by human activities such as mining, oil and gas extraction, and coal consumption.

In the United Kingdom, HSE has issued a user guidance note on selecting the correct portable radiation measurement instrument for the application concerned.

The UK NPL publishes a guide on the alarm levels to be used with instruments for checking personnel exiting controlled areas in which contamination may be encountered.

Airborne contamination is measured by specialist radiological instruments that continuously pump the sampled air through a filter.

Airborne particles accumulate on the filter and can be measured in a number of ways: Commonly a semiconductor radiation detection sensor is used that can also provide spectrographic information on the contamination being collected.

"Contamination control products" is a broad term that includes fixatives, strippable coatings, and decontamination gels.

The national government is under pressure to clean up radioactivity due to the Fukushima nuclear accident of March 2011 from as much land as possible so that some of the 110,000 displaced people can return.

[citation needed] If a survey or map is made of a contaminated area, random sampling locations may be labeled with their activity in becquerels or curies on contact.

In the case of low-level contamination by isotopes with a short half-life, the best course of action may be to simply allow the material to naturally decay.

Longer-lived isotopes should be cleaned up and properly disposed of because even a very low level of radiation can be life-threatening when in long exposure to it.

People can be exposed to potentially lethal radiation levels, both externally and internally, from the spread of contamination following an accident (or a deliberate initiation) involving large quantities of radioactive material.

In a contaminated facility, hot spots may be marked with a sign, shielded with bags of lead shot, or cordoned off with warning tape containing the radioactive trefoil symbol.

[14] Radioactive contamination by definition emits ionizing radiation, which can irradiate the human body from an external or internal origin.

Penetrating radiation such as gamma rays, X-rays, neutrons or beta particles pose the greatest risk from an external source.

Large quantities of inhaled or ingested radioactive iodine may impair or destroy the thyroid, while other tissues are affected to a lesser extent.

The radiation risk proposed by the International Commission on Radiological Protection (ICRP) predicts that an effective dose of one sievert (100 rem) carries a 5.5% chance of developing cancer.

[16] The ICRP further states "For internal exposure, committed effective doses are generally determined from an assessment of the intakes of radionuclides from bioassay measurements or other quantities (e.g., activity retained in the body or in daily excreta).

A 2015 report in Lancet explained that serious impacts of nuclear accidents were often not directly attributable to radiation exposure, but rather social and psychological effects.

[20] Forced evacuation from a radiological or nuclear accident may lead to social isolation, anxiety, depression, psychosomatic medical problems, reckless behavior, even suicide.

[20] Frank N. von Hippel, a U.S. scientist, commented on 2011 Fukushima nuclear disaster, saying that "fear of ionizing radiation could have long-term psychological effects on a large portion of the population in the contaminated areas".

[21] Evacuation and long-term displacement of affected populations create problems for many people, especially the elderly and hospital patients.

[19] Such great psychological danger does not accompany other materials that put people at risk of cancer and other deadly illness.

Visceral fear is not widely aroused by, for example, the daily emissions from coal burning, although, as a National Academy of Sciences study found, this causes 10,000 premature deaths a year in the US population of 317,413,000.

The Hanford site represents two-thirds of the United States' high-level radioactive waste by volume. Nuclear reactors line the riverbank at the Hanford Site along the Columbia River in January 1960.
As of 2013, the Fukushima nuclear disaster site remains highly radioactive , with some 160,000 evacuees still living in temporary housing, and some land will be unfarmable for centuries. The difficult cleanup job will take 40 or more years, and cost tens of billions of dollars. [ 1 ] [ 2 ]
Bomb pulse : the global airborne contamination by atmospheric nuclear weapon tests almost doubled the concentration of 14 C in the Northern Hemisphere. Plot of atmospheric 14 C, New Zealand [ 4 ] and Austria . [ 5 ] The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere. . [ 6 ]
Large industrial glovebox in the nuclear industry
Geiger-Muller counters being used as gamma survey monitors, seeking radioactive satellite debris
A clean-up crew working to remove radioactive contamination after the Three Mile Island accident .
Periodic table with elements colored according to the half-life of their most stable isotope.
Elements which contain at least one stable isotope.
Radioactive elements: the most stable isotope is very long-lived, with half-life of over four million years.
Radioactive elements: the most stable isotope has half-life between 800 and 34.000 years.
Radioactive elements: the most stable isotope has half-life between one day and 130 years.
Highly radioactive elements: the most stable isotope has half-life between several minutes and one day.
Extremely radioactive elements: the most stable isotope has half-life less than several minutes.
The radiation warning symbol ( trefoil )
Alpha radiation consists of helium-4 nucleus and is readily stopped by a sheet of paper. Beta radiation, consisting of electrons , is halted by an aluminium plate. Gamma radiation is eventually absorbed as it penetrates a dense material. Lead is good at absorbing gamma radiation, due to its density.