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3.3.4 Radioactively contaminated sites, sources of contaminations and radionuclides of concern

Contents
3.3.4.1 Radioactively contaminated sites
3.3.4.2 Radionuclides of concern
3.3.4.3 Background radioactivity and selecting background reference areas

3.3.4.1 Radioactively contaminated sites

The use of radioactive materials for a variety of purposes has resulted in contamination of sites and/or groundwaters (i.e., land areas, including structures, waste dumps, soils, rocks, biota, surface and groundwaters, etc.) throughout the world. The radionuclides involved may have been produced for a variety of reasons, including scientific research, industry, medicine or warfare. Another possibility is that they are simply an unnatural concentration of the naturally occurring radioactive elements. The affected sites can range from small localized areas in urban environments to larger areas encompassing many tens or hundreds of square kilometres.

The source of the radioactive contamination may be from a known activity at the site and the radionuclides involved may be known. Records may give information about the radionuclides involved and their likely disposition and chemical state. Alternatively, a chance discovery may have revealed the presence of contamination and no other information is available. It might be that the site is populated and immediate steps must be taken to ensure no harm is done, or it could be that people are easily excluded and there is adequate time to undertake investigations.

These and other differences mean that each site and/or groundwater must be treated as a unique situation taking into account its own particular circumstances. In general, all potentially contaminated sites and/or groundwaters will need an evaluation (characterization) based on the principles given herein. In minor cases of contamination, many steps can be treated summarily, but usually all will still have to be dealt with.

Some examples of radioactively contaminated sites and/or groundwaters that might be encountered are given below. The list is not exhaustive but is intended to show the wide range of problems that might be found; they can vary in extent from large land sites to relatively small sites such as a manufacturing facility.

  • Nuclear power production and nuclear fuel cycle activities. The various stages of the nuclear fuel cycle and the operation and decommissioning of nuclear reactors all have the potential to create contaminated sites. The contamination may include mill tailings; spillage of uranium ore end product at the mine and in transport; waste from enrichment and fuel fabrication operations; fission product and actinide waste streams from reprocessing of fuel elements; radioactive effluents from normal operations of nuclear power plants; wastes produced during decommissioning of reactors; and major releases under accident conditions, e.g., contamination from uranium ore and yellowcake handling, 137Cs contamination of river banks following accidents at a nuclear power plant, contamination problems occurring on railway property due to rain run-off of fission product contaminants from fuel transportation containers.
  • Production and use of radioactive substances for medical, research or industrial purposes. Radioactive materials have been used widely since their discovery for a variety of scientific, medical and industrial uses. In some cases, either through ignorance, carelessness, or accident, sites have been left contaminated with residues of the operations. Such sites include factories where radium was used in luminescent paint and thorium was used in thorium coated gas mantles. Other locations where radionuclides have been handled have the potential for leaving contamination and the possible widespread dispersal of radium contamination in the surrounds of production plants.
  • Mining and chemical processing associated with uranium and thorium impurities. Because uranium and thorium are present in many ores containing other useful minerals, the mining of these ores and the processing to recover materials such as copper, gold, niobium, coal and monazite will generally produce waste streams containing significant amounts of radioactivity. These have the potential to result in unacceptably contaminated sites. Examples are contamination from the processing of monazite ores, contamination issues arising from naturally occurring radioactive materials (NORM) found in coal slag piles, or by-products of the fertilizer industry -technically enhanced naturally occurring radioactive materials1. However other activities would also result in the accumulation of NORM, such as:
    • Oil and gas extraction.
    • Fertiliser production.
    • Phosphoric acid production.
    • Iron and steel production.
    • Cement industry.
    • Ceramics industry.
  • Military activities and the production, testing and use of nuclear weapons. The manufacture of nuclear weapons involves the handling, transport and storage of large quantities of radioactive materials. The testing of weapons may involve nuclear yield and the release of fission products and activation products, or may involve the deliberate dispersal of radioactive materials in the environment. Some military use is made of depleted uranium which may contain fission products if obtained from reprocessed fuel. All of these activities have, in the past, resulted in contaminated sites, many of very large areas.
  • Major incidents. In the course of nuclear weapons production and transport, there has been several severe accidents resulting in considerable contamination. These include: Windscale Pile 1, Kyshtym (1957), Palomares (1966) and Thule (1968). The spread of contamination by accident or by human ignorance are illustrated by the cases of the Chernobyl reactor (1986) and Goiania (1987).
  • Authorised dispose of wastes to approved landfill sites containing low levels of radioactivity. Moreover, wastes with very low levels of radioactivity can also be disposed of in general waste, including consumer products like smoke detectors, leading to the generation of landfill emissions containing radioactivity, such as tritium in leachate. Some landfill sites may have in the past accepted wastes from naturally occurring radioactive material (NORM) and technically enhanced naturally occurring radioactive material1 industries resulting in elevated levels of natural radionuclides in the emissions.

(Note of the editor, dated 9 September 2011: “Table 3.10 Examples of typical radioactively contaminated sites worldwide as well as details of expected radionuclide contaminants” have been deleted. This information is now covered and expanded in tables presented in Appendix A.)

3.3.4.2 Radionuclides of concern

The radioactive contaminants associated with a given contamination problem may be quite site specific. The classes of radionuclides that may be encountered include fission products, activation products, uranium and other naturally occurring radionuclides, other man-made radioisotopes, transuranics, tritium, and so on.

In Appendix A sources of mixed contamination (eg radioactive and hazardous) are presented. Appendix A. This Appendix A contains information on candidate radiological contaminates which can be present at a site or in groundwater with or without hazardous contaminants and visa versa, with as main aims that:

  • Awareness is created by stakeholders e.g. industry, regulators, owners, communities, etc. about the possible presence of other radiological and hazardous contaminants then one might expect at a specific site, so that an appropriate strategy, implementation and execution of a programme to remediate this site can be developed that has the support of all stakeholders;
  • New contaminated sites can be prevented by learning of the past by presenting these detailed overviews from in literature reported radiological contaminants in the presence of hazardous contaminants.

This information in this Appendix is on candidate radiological contaminants in the presence of candidate hazardous contaminants and visa versa. Presented information is extracted from freely available literature. The presented overviews in this Appendix are setup with the goal to be as complete as possible, to provide relevant information and references about each candidate contaminant and to direct readers to more detailed information. However, it is sometimes very hard to lay hands on this more detailed information eg examples of contaminated sites, mobility of contaminants, lessons learned, etc.
The following overview tables are presented:

  • Table A.1: General overview of the radiological and hazardous contaminants, and type of activitities where these contaminates have been detected during already performed remediation activities.
  • Table A.2: Candidate radiological contaminants
  • Table A.3: Candidate hazardous contaminants.
    Candidate contaminants are presented in alphabetical order and additional information of the candidate contaminant can be found in the last columns of table A.2 and Table A.3 respectively.
Radioactive contaminants Radioactive contaminants Radioactive contaminants
Activation products 3H (Tritium) Th (Thorium)
Activation and fission products 14C (Carbon) 232Th
Fissile components of test
weapons
60C (Cobalt) U (Uranium)
Fission products Nb (Niobium) U depleted
Fission products (long-lived) 90Sr (Strontium) U fuel and fission products
High levels of radioactive
liquids incl. transuranic
elements
99Tc (technetium) U natural
“Immobile elements” I (Iodine) 235U and 238U
NORM (Natural Occurring
Radioactive Materials)
129I 238U + daughters
Radionuclides 137Cs (Caesium) 241Am (Americium)
Radionuclides (tracers) 154Eu and 155Eu (Europium) Pu (Plutonium)
α-emitters 210Pb (Lead) Pu fissile material
β-emitters 226Ra (Radium) Pu fuel and fission products
γ-emitters Radium and Thorium Pu isotopes
n-emitters Zr (zirconium)

Table 3.11a Overview of the radiological contaminants reported worldwide (in alphabetical order).

Hazardous contaminants Hazardous contaminants Hazardous contaminants
Al (Aluminum, produced
residues and wastes
caused by mining,
milling and processing
of aluminum ore)
Chromium solutions Th (Thorium)
Asbestos Corrosive substances Natural Gas and oil
(produced residues
and wastes due to
mining, milling and
processing)
Aviation fuel Cu (Copper, produced
residues and wastes
caused by mining,
milling and processing
of copper ore)
NaNO3 (Sodium nitrate
solutions)
Barium Degreasing material (NO3)-
Be (Beryllium) Degreasing solvents Niobium (see Tantalum)
Biological materials Etching solutions Oils
Building materials (due
to possible applied
additives)
Explosive residues Organic solvents
CCl4 (Carbon
tetrachloride)
Fe (Iron, produced
residues and waste
due to mining, milling
and processing)
Phosphate (produced
residues and wastes
due to mining, milling
and processing)
Cellulosics F (Fluorine) Pb (Lead, contaminated
due to use as shielding
material in the
nuclear industry)
Ceramic materials
(due to possible
elevated levels of U
and Th in additives)
F- Rare earths elements,
REE, (produced residues
and wastes due to mining,
milling and processing)
CHCl3 (Chloroform) Fluorite (due to
possible elevated
levels of U)
Red mud
CH4 (Methane – natural
gas, produced residues
and wastes due to
mining and processing)
Au (Gold, produced
residues and wastes
due to mining, milling
and processing)
Rutile (see Titanium)
CH10-xClx (PCBsb) Heavy metals (SO4)2- (Sulphiric acid)
C2HCl3 (Trichloroethylene
TCEa)
Heavy minerals Uranium
C6H4(CH3)2 (Xylene) Hg (Mercury) Tantalum / niobium
(produced residues and
wastes due to mining,
milling and processing)
C6H5CH3 (Toluene) High explosives Tin (produced residues
and wastes due to mining,
milling and processing)
Cl (Chlorine) Lubricants VOCsc
Chlorinated solvents Metals Water (produced residues
and wastes due to
mining and processing)
Contaminated clothing Mo (Molybdenum, produced
residues and wastes
due to mining, milling
and processing, and
mainly U-series)
Yttrium oxide
Cr6+ (Chromium 6+) Monazite (due to
possible elevated
levels Th in the ore)
Zircon and zirconia
(produced residues
and wastes due to mining,
milling and processing)

Table 3.11b Overview of hazardous contaminants reported in the presence of radiological contaminants worldwide (in alphabetical order).

a) TCE trichloroethylene
b) PCB’s polychlorinated biphenyls
c) VOC’s volatile organic compounds
d) TBP tributylphosphate

Type of activity or usage Type of activity or usage
Aircraft crash Accident sites Phosphate fertilizer
production
In general, no detail
Energy production Coal-fired power stations Prototype engines Test nuclear engines
Gas cooled nuclear
reactors; operations
Prototype reactors Test reactors
Nuclear power plants Research facilities Incinerator wastes
Hospitals In-vivo testing Radioecological and
biology studies
Medical laboratories Research reactors In general, no detail
Pharmaceutical testing Neutron activation
Industry Coloring agents for
glazing
Thorium gas mantel works In general, no detail
Instrument manufacturing
and maintenance including
luminising dials and other
luminising materials
Weapons assembly Depleted uranium
penetrators and armor
Mining, milling and processing Machining
Oil and gas productions In general, no detail
Phosphate productions Warhead development,
temperature testing
Radium luminising works Weapons production Fuel fabrication
Welding rods Irradiated fuel processing
Military bases Nuclear submarine decommissioning Plutonium purification
Mining, milling and processing of ores. Examples: copper, gold,
iron, niobium,
molybdenum, monazite,
natural gas, oil,
phosphate, rare earth
elements, silver,
tantalum, thorium
hydroxide, tin,
uranium, water,
yttrium oxide,
zircon and zirconia, etc
Reactor operations
Nuclear power plants In general, no detail Waste storage: Landfills
Nuclear power plants
and Research reactors
Neutron activation Weapons testing In general, no detail
Nuclear weapons Fuel (reprocessing)
fabrication plants.
Radiological warfare
agent testing
Peaceful nuclear explosions Oil and gas reservoir
enhancement
Safety testing of weapons

Table 3.11c Overview of type of activity or usage where radiological contaminants have been reported worldwide (in alphabetical order).
.

3.3.4.3 Background radioactivity and selecting background reference areas

It is important to distinguish between radioactive contaminations resulting from:

  • Human activities on the site.
  • The background level of radioactivity, which arises from natural radioactivity in the soils and rocks, and in some cases from former human activities.
  • Levels of man-made radionuclides originating from sources unrelated to the site (for example, atmospheric fallout from the Chernobyl accident).

Background levels of radioactivity will vary spatially both from one site to another and within the same site. In addition, background levels of radiation can vary over time as well. The principal factor that controls the background level of natural radionuclides at a site is the level of radioactivity in the rock from which the soil was derived. Natural series radionuclides can also be concentrated in different parts of the soil column and weathering profile, typically associated with iron oxides, clay minerals and organic material. Therefore, it is to be expected that background levels of naturally occurring radionuclides in the rocks and soils will vary with depth.

Many sites contain areas of made ground; that is, material that has been imported onto the site, or moved from another area of the site, to fill depressions and raise ground level. Some types of made ground, such as ash and metallurgical slag materials, contain elevated levels of naturally occurring radionuclides. Others, such as imported sand and clay, may have levels of radioactivity below that of the natural soil at the site. This may make determination of background levels difficult, where the usual practice would be to go to a known, uncontaminated area nearby to determine the local background rate. This method might not take account of the content of any made ground on the site. Variations in natural background level may be detected by some walkover radiation surveys and should be taken into account when deriving background levels for the site (see Section 3.3.3).

The level for action must be distinguishable from background, otherwise it may be difficult to suitably differentiate for clean-up.

Levels of atmospheric fallout-derived radionuclides (for example, 3H and 137Cs) are influenced largely by altitude and rainfall patterns. In general atmospheric fallout has arisen from the testing of nuclear weapons and from more recent events, principally the Chernobyl accident.

Levels of radioactivity in the environment can be influenced by past or present authorized radioactive discharges into the atmosphere and aquatic systems. The impact of marine discharges can extend some distance away from the site due to the accumulation of material in sediments over an extended period of operations.

Levels of radioactivity may also occur at significant levels due to the naturally-occurring uranium, thorium, and actinium series; 40K; 14C; and tritium (3H).

Care has to be taken with discharges in the past. These discharges may be allowed according to the applicable laws at that time and therefore they may be not subjected to the present regulations.
External radiation dose rates from the background levels of radioactivity in rocks and soils depend on the levels and nature of the radioactivity. Typical background dose rates are 0.05 – 0.1 µSv/h.

Radio-nuclide concentrations in background water samples should be determined for a sufficient number of water samples that are upstream and downstream of the site or in areas unaffected by site operations. Consideration should be given to any spatial or temporal variations in the background radio-nuclide concentrations.

Careful assessment of the background to provide a baseline is required, together with the enhancement as a direct result of the practices carried out on the site.

1 Formerly called TENORM, since 2010 the NORM industry is in favour to call all radioactive material with elevated levels of primordial nuclides just NORM, independent the cause of the elevation.