It inclu es the sele tion of the sampl ng s rat eg , the outl ne of the samplng plan, the pr sentation of g ene al samplng methods an eq ipment, as wel as the methodolo y of the pr -tr a
General
During the planning process, the sampling strategy for the site under investigation is determined according to the objectives described in Clause 4 item a), resulting in the definition of a sampling plan.
Initial investigation
Whatever the objective of the work being carried out, certain preliminaries shall be undertaken during the initial investigation phase to help define the sampling strategy, such as the following:
— analysis of historical and administrative data, company archives, previous studies, and interviews with former employees, which help identify potential sources of radioactive contamination;
This article focuses on gathering data regarding the geological, hydrological, and pedological features, along with key climatic parameters, to effectively characterize the spatial and temporal variations in radioactivity levels within a specific area.
— survey of the site under investigation to identify its topography, the nature of the vegetation cover, and any peculiarities that can affect the techniques and the sampling plan;
For farmland management, it is essential to gather information from farmers regarding the types and depths of agricultural practices, such as sub-soiling, drainage, ploughing, and harrowing Additionally, understanding the use of chemical fertilizers and additives is crucial, as these can contribute to increased natural radioactivity depending on the nature and quantity of the products applied.
In the absence of data on radioactive soil contamination or when contamination is suspected, it is essential to conduct in situ analytical investigations with portable detectors or perform preliminary sampling followed by laboratory analysis to determine appropriate sampling areas and strategies.
Types of sampling strategies
Sampling strategies are either orientated or probabilistic depending upon the objectives and the initial knowledge of radioactivity distribution over the area under investigation.
Orientated strategies are based on a priori constraints that lead to a selection of sampling units in a specific area under special scrutiny because of particular interest or level of contamination.
Probabilistic strategies are based on a selection of sampling units without any a priori constraints.The selection of sampling units and points is described in 6.2.
Selection of the sampling strategy
The chosen sampling strategy must align with the specific objectives and relevant endpoints, such as safeguarding human health and the environment, while also considering social and economic factors It is essential that the selected strategy accurately represents the distribution of radionuclides in the soil of the investigated area to ensure reliable results.
Although the strategy can only be defined on a case-by-case basis, the selection of the sampling strategy should follow these stages:
— analysis of the records, which enables an historic study of the sampling site, in particular of its previous use (identification of the source);
— evaluation of preferential migration pathways and/or accumulation areas;
— site reconnaissance with respect to the boundaries of the sampling areas and sampling undertaken;
— site reconnaissance: a rapid analytical investigation using portable radioactivity detectors can be used to characterize the distribution of the radioactivity of the areas to be studied.
This phase of the planning process involves making numerous decisions that can lead to significant and expensive activities It also encompasses defining data quality objectives based on the parameters to be analyzed.
Annex A gives a flow diagram that helps in the selection of a sampling strategy according to the objectives of the investigation.
The selected strategy influences the sampling density, as well as the temporal and spatial distribution of the units from which samples are gathered, while also considering the timing of the sampling.
— potential distribution of radionuclide: homogeneous or heterogeneous (“hot” spots);
— minimum mass of soil necessary to carry out all the laboratory tests; and
— maximum number of tests that can be performed by the laboratory for the study.
A prediction of soil contamination presence and its distribution can often be established, necessitating verification through an oriented sampling strategy A systematic variant of this strategy, utilizing selected representative sampling points, is effective for routine monitoring of sites with known radioactive origins and distribution patterns This approach enables a more precise determination of the number and location of sampling points compared to purely probabilistic methods By combining subjective selection with statistical techniques, quality requirements for interpretation can be met In cases where the spatial distribution of radioactivity is unknown, an oriented spatially random strategy should be employed.
Probabilistic strategies utilizing random sampling are effective only when the radioactivity distribution on a site is homogeneous In cases where there are occasional heterogeneities, such as point sources, it is advisable to adopt a systematic sampling strategy tailored to the understanding of these heterogeneities across various sampling areas.
For investigations aimed at characterizing recent soil surface deposits, such as those resulting from routine authorized gaseous releases or accidents, it is advisable to collect samples from the top layer of the soil.
To study a polluted site and assess the vertical migration of radionuclides, it is essential to collect samples from various depths These layers can be defined by uniform thickness or as representative of different soil horizons, which aids in predicting potential groundwater contamination.
The sampling strategy leads to a set of technical options that are detailed in Clause 6.
General
A sampling plan is a detailed procedure that outlines the necessary actions for fieldwork based on the chosen strategy It specifies the human resources required for sampling and is closely tied to the study's objectives, the site's environmental characteristics, the laboratory's testing capabilities, and the data quality standards needed for accurate result interpretation.
The sampling plan will be developed individually for each case, encompassing essential details for effective sampling This includes identifying sampling areas and units, specifying the locations of sampling points, determining the types of samples (single or composite), outlining the number of increments for composite samples, establishing the sampling frequency, and specifying the required sample mass based on intended tests Additionally, the plan will address material archiving requirements and vertical distribution considerations.
Selection of sampling areas, units, and points
General
After establishing the sampling strategy, the sampling areas and units are determined based on initial investigation findings In certain instances, legal requirements dictate the boundaries of these areas and the placement of sampling units, particularly in the context of new nuclear installations These definitions stem from a reference radiological study conducted for the project For accident investigations, the size and location of sampling units are influenced by environmental factors such as wind strength and direction, topography, and variations in source characteristics, including radionuclides, activity levels, and release duration.
For a probabilistic strategy, the sampling units can be selected either by systematic or random approaches whereas it cannot be done by a random approach for an orientated strategy.
For both strategies, the sampling points can be selected either by a systematic or a random approach.
On the same site, depending on the heterogeneity of the radioactivity distribution, a combination of these strategies can be applied to the different sampling areas.
Sampling for use with a probabilistic strategy
In a probabilistic strategy, identified sampling areas are overlaid with a grid that delineates the sampling units The grid mesh size must consider the site's surface area, the laboratory's analytical capacity, and financial limitations that affect the number of samples analyzed Consequently, the surface area of the grid units can vary significantly, ranging from a few square meters to several square kilometers, depending on the specific site being studied.
A radioactivity map generated from a preliminary in situ radiological inspection, as outlined in ISO 18589-7, allows for a sampling grid that aligns with the radioactive cartography This map can feature a denser grid in areas suspected of contamination, while a less dense grid may be used in regions where contamination is presumed absent.
Systematic sampling involves selecting a sampling point at each knot or center of the sampling unit, with the total number of sampled units influenced by the environmental heterogeneity and access limitations due to the area's topographical complexity In contrast, random sampling requires referencing the sampling units and randomly selecting a specified number.
To assess the environmental impact of a specific source of radioactivity, it is essential to compare it with the background activity level This background level can be measured in an area presumed to be free from contamination by the source being studied, such as locations not affected by effluent discharges from the facility in question, serving as the reference area.
Sampling for use with an orientated strategy
An oriented sampling strategy defines the sampling area based on the investigation's objectives, utilizing environmental data and cartographic results to guide the process.
The sampling plan is based on a subjective selection of sampling units as a result of prior knowledge of the area and/or initial in situ radioactivity investigations.
To effectively collect samples with the highest activity levels in the absence of radioactivity data, conducting a preliminary radiological investigation using a portable detector is essential This investigation facilitates the creation of a site map that identifies contaminated areas and aids in developing a precise sampling plan, including the exact locations for sampling units, as outlined in ISO 18589-7.
This initial investigation aims to evaluate the risks associated with worker exposure during sampling operations It will also establish necessary radiation protection measures, particularly those to be implemented on-site to safeguard personnel from radiation hazards.
In routine surveillance of a nuclear installation, the sampling unit can be chosen as the point of maximum concentration of the predicted fallout of gaseous discharges from the plant.
When assessing the radioactivity of soil and environmental components such as air, water, and bio-indicators, it is crucial to consider the interrelation of these elements in the selection of sampling units.
Selection criteria of sampling areas and sampling units
By analyzing historical environmental studies and conducting visual site reconnaissance, we can identify sampling areas characterized by uniform topological features and vegetation cover This process involves distinguishing between elevated and sloping zones, as well as differentiating herbaceous areas from bushy ones, and forested regions from cultivated and ploughed lands.
When selecting sampling units, prioritize areas with undisturbed soil layers and well-maintained herbaceous cover, ensuring the surface area is several square meters Document any disturbances, noting their scale, nature, and origin In addition to assessing radioactivity in plants, conduct radioactive surveillance of disturbed soils For agricultural land, consider the upper layer, equivalent to the ploughed depth, as homogeneous if contamination occurred prior to ploughing For industrial or built-up areas, investigate the ground fill material, accounting for its inherent heterogeneity and deposition method.
For routine surveillance, the sampling units that are regularly sampled over time have to be kept clear of trees and bushes.
When describing the soil profile as part of the sampling strategy, the thickness of each layer should be based on pedological characteristics or the anticipated vertical migration rate of radionuclides For detailed sampling methods related to depth collection, refer to section 7.2.3, and an example of a sampling plan can be found in Annex C.
For farmland, border effects, in particular, can be avoided by remaining at least 20 m inside the perimeter of the plot, unless otherwise specified in the objectives of the study.
Identification of sampling areas, units, and points
Sampling areas and units shall be identified by the following parameters:
— administrative district, name of the town, site, or commonly accepted name of location;
— name or reference of the sampling area and units;
— geographic coordinates established using a topographic map or a global positioning system.
For accurate delineation of area limits and identification of sampling units, it is advisable to utilize an official topographic map from a national authority, ensuring it has a sufficiently detailed scale.
The sampling points are described by their geographical coordinates using a topographic map or a global positioning system.
Selection of field equipment
When selecting equipment, it is essential to adhere to ISO 10381-2 standards Special emphasis must be placed on the quality of the sampling tools to ensure they do not compromise the integrity of the radionuclides being measured, preventing any pollution or loss during the sampling process.
The choice of equipment for soil sampling is determined by the sampling plan, which specifies the sampling depth and soil type For setting boundaries, materials like posts and tapes are used For surface or near-surface samples, tools such as shovels, coring tools (metallic frames, gouge augers, gimlets, straight probes, and spades) are essential, ensuring that equipment is cleaned between samplings For samples extending up to a depth of 2 meters, augers or construction machinery are recommended.
— mechanical digger with bucket to dig a trench from which samples are taken (attention shall be paid to weak walls in crumbly or disturbed soils);
For sampling at depths exceeding 2 meters, a core driller with non-reactive drilling tubes is essential, while mechanical or hydraulic thrust sampling tubes are also utilized for various sampling needs Additionally, specific equipment is required for all sampling processes to ensure accurate results.
— stainless steel spatula or knife;
— container(s) with a capacity of at least 10 l;
— clean, dry canvas sheets that do not react with soil, measuring approximately 2 m 2 ;
— wide-necked bags, or bottles, or plastics boxes with a capacity of at least 2 l, which are moisture- resistant, waterproof, dustproof, and do not react with the soil;
— sample identification equipment: labels, markers, etc.;
When investigating volatile radionuclides, it is crucial to implement specific precautions to prevent the loss of volatiles during sample collection and storage Additionally, specialized equipment is essential for accurately determining surface activity.
— balances with a maximum range and sufficient accuracy;
— measuring tape or gauge of sufficient length to measure the dimensions of the increments.
General
The sampling process, outlined in the sampling plan, is guided by the study's objectives Sample collection and preparation are independent of the chosen sampling strategy, whether probabilistic or oriented Detailed objectives for sampling at various depths, including the upper layers up to 20 cm and deeper layers for different applications, are specified in section 7.2.1.
The generic instructions presented in 7.2.2 to 7.2.3 are applicable to the following cases:
— initial characterization of radioactivity in the environment;
— routine surveillance of the impact of nuclear installations or of the evolution of the surrounding general territory;
— investigations of accidents and incidents;
— planning and surveillance of remedial action;
— de-commissioning of installations and disposal of soil from the site;
— specific advice is given on
— investigation of the vertical distribution of radionuclides, including samples taken from a trench;
— determination of the activity deposited in the soil.
Collection of samples
Selection of sampling depth versus objectives of the study
7.2.1.1 Initial characterization of radioactivity in the environment
For undisturbed soil, the depth of the layer or layers for sampling can be determined using either of the following two approaches.
— Uniform approach, with sampling performed at depths independent of the natural variations of the soil characteristics [13] ,[14] For example, a surface layer can be sampled as a single unit down to
For effective sampling of potential future fallout, it is recommended to collect a surface layer in two segments: one from the surface to a depth of 5 cm and another extending from 5 cm to 20 cm.
A non-uniform sampling approach is tailored to the natural characteristics of the soil, where sampling layers are defined by the depth of the root layer or the pedological features of the profile When multiple soil horizons exist, it is essential to collect a distinct number of samples for each horizon to ensure accurate representation.
In soils affected by human activities like farming, two distinct sampling approaches are utilized: the uniform approach, which involves sampling at a depth tailored to local agricultural practices—typically up to 20 cm or more based on ploughing depth; and the non-uniform approach, which considers the specific characteristics of the soil This latter method requires determining the surface layer based on the disturbed horizon's depth and sampling lower layers according to their pedological traits, necessitating separate samples for each distinct soil horizon present.
7.2.1.2 Routine surveillance of the impact of nuclear installations or of the evolution of the surrounding general territory
For effective soil sampling, undisturbed soils are chosen based on a consistent method outlined in section 7.2.1.1 To ensure comparability between samples from different operations, it is crucial to select areas that have not been sampled for at least one year Additionally, when establishing a reference surface layer during the site's initial characterization, the same depth should be maintained to assess potential fallout accurately.
When the physical and chemical properties of soil are uniform within a sampling unit and there is no expected change in its radioactive characteristics over time, it is sufficient to conduct sampling at a single point.
Soil increments should be collected using an appropriate tool to obtain at least 1 kg of dry soil from each sampling point To ensure comparability of results across different groups conducting territory surveillance, it is essential to collect soil from the same depth at each sampling location.
7.2.1.3 Investigations of accidents and incidents
In the event of a potential contamination following an accident, it is crucial to conduct surface sampling across the entire suspect area as soon as technically possible, while adhering to radiation protection principles The primary goal is to assess the extent of horizontal contamination and, in cases of heterogeneous diffuse pollution with identified source points, to evaluate the resulting activity gradient.
As a measure of preparedness for an accident or incident, particularly suitable sampling units around facilities can be selected in advance to allow for adequate sampling immediately after an event.
For assessing soil radioactivity after recent contamination, it is advisable to sample the surface to a maximum depth of 5 cm Accurate measurement of surface activity requires precise determination of the sampled surface area, as well as the mass of both the sorted and laboratory samples Consistent sampling depth increments must be documented, as outlined in Clause 9.
When addressing past contamination, the sampling procedure must account for the movement of radionuclides in the soil It is essential to conduct sampling at various depths, up to a maximum determined by the vertical migration rates influenced by soil characteristics and the chemical and physical properties of the radionuclides For more information, refer to section 7.2.3.
When construction debris, such as building materials, is found on-site, it is essential to conduct a radiological characterization to determine if these materials may pose a risk as potential sources of radionuclides and radiation exposure.
Fallout contamination can limit the availability of suitable sampling locations, particularly in urban or forested environments Therefore, it is advisable to conduct operations in open areas that are distanced from residential buildings and trees.
7.2.1.4 Planning and surveillance of remedial action
This operation entails comprehensive horizontal and vertical profile sampling throughout the investigation area to assess the properties of disturbed soil at various depths The sampling depth may be extended until the radionuclides of interest are undetectable In agricultural settings, the sample depth must be at least equal to the greater of the ploughed depth or the root layer depth.
There are two scenarios regarding site contamination: it may be well-documented, such as in historical uranium-mining locations, or it may stem from unrecorded past activities that have only recently raised suspicions.
When contamination is clearly identified, protective measures are typically implemented Remedial action planning can then proceed according to the established generic process outlined previously.
In cases of suspected radioactive soil contamination, whether due to rumors, individual requests, or accidental discoveries of past radionuclide use, it is essential to assess the site's status and initiate prompt investigation measures, irrespective of the suspicion's source.
Sampling surface soil
When selecting sampling units, it is essential to remove and preserve a portion of the above-ground vegetation at each sampling point, particularly for transfer pathway studies To prevent cross-contamination of samples, standard precautions must be observed during the sampling process In cases where soil exhibits high activity concentration, it is crucial to clean the sampling device between each point to avoid contamination.
To collect soil samples effectively, insert the core into the soil to a depth of at least 5 cm, depending on the study's objectives After removing the core, place the soil plug, along with any remaining plant material and roots, into a suitable container This process should be repeated for each sampling point within the unit, and the individual soil plugs should be combined to create a composite sample.
The coring tool, which holds the soil plug, can be taken to the laboratory for extraction In the lab, increments can be combined and coarse elements can be removed, allowing for more favorable conditions than those available on-site.
For certain dry, loose soil types, a square frame measuring 20 cm on each side and 5 cm in height, or a ring with a 10 cm diameter and 5 cm depth, can be utilized The frame is pressed into the soil surface, and the soil within is excavated to a depth of 5 cm using a small scoop, then transferred to a suitable container This process is repeated at each sampling point within the sampling unit, and the collected soil increments are combined to create a single composite sample.
Sampling soil profile
This operation entails sampling to assess the level of contamination at various depths and to analyze the gradient of activity concentrations The depth of sampling is determined by the soil characteristics and the study's objectives If activity is detected at significant depths, drilling boreholes may be required.
For cohesive soils that are easily penetrable to a depth of a few tens of centimeters, sampling can be conducted using a coring tool with an internal sheath In contrast, for other soil types, samples may be obtained from a trench up to approximately 2 meters deep or through core drilling techniques that extract samples from depths of several meters.
NOTE The trench technique is preferable to other techniques because it allows a better observation of soil horizons with a minimum of disturbance.
In soils exhibiting natural or artificial macroscopic heterogeneities, such as contraction gaps in clay or drainage ditches, it is advisable to collect samples away from these structures unless absolutely necessary Any anomalies observed should be documented on the sample sheet For highly permeable soils, like sand, which facilitate deeper migration of radionuclides, sampling should extend to a soil horizon where these radionuclides are no longer present.
When sampling soil layers, it is essential to ensure that the thickness of each section corresponds to the total profile depth divided by the number of sampling levels Additionally, precautions must be taken to avoid overlapping sample layers from different soil horizons.
The soil description must include details about the soil horizons and their physical characteristics, such as color, texture, structure, and coarse-element content, to facilitate the interpretation of the results.
A trench is excavated using appropriate equipment, typically measuring between 0.5 m to 1 m in width and 2 m to 4 m in length, to effectively analyze the complete stratification profile of the soil The trench dimensions are influenced by the tools employed, such as a mechanical digger with a bucket, the desired depth—averaging around 2 m—and the characteristics of the soil being examined.
The vertical wall of the trench is scraped using a knife to find the soil horizons that are not compacted or contaminated by the digging instrument.
Soil increments, each with a minimum mass of 1 kg, are manually collected from the wall using a spatula, ensuring that distinct soil horizons remain unblended The quantity of increments taken from each horizon is determined by the dimensions of the sampling unit and the necessary mass for testing.
To ensure accurate sampling, it is crucial to prevent soil from falling into the probe trench before and during the process Increments from the same horizon should be collected in a clean container or plastic bag, and the composite sample must be thoroughly mixed with a shovel or suitable tool During this procedure, clods should be broken up, and any coarse elements larger than 2 cm should be either removed or collected separately, depending on the study's objectives.
7.2.3.3 Samples at depth by core drilling
First, a surface sample with a minimum mass of 1 kg of dry matter and from a maximum depth of 5 cm is taken using a suitable piece of equipment as described in 7.2.2.3.
Core samples are obtained at the specified depth through core drilling with appropriate equipment The cores are carefully removed from the coring tool and placed onto a clean, inert, and dry surface, ensuring that the orientation (top-bottom) and depths of the samples are clearly marked.
In a uniform sampling method with defined depth layers, cores are extracted from the surface layer and divided into at least five distinct sections, ensuring that the various soil layers remain unblended These sections represent the increments of the sampled layers.
In a horizon approach, soil cores are extracted beginning with the surface layer and are sliced according to the boundaries of distinct soil horizons identified throughout the core length These sections represent the increments of the various sampled horizons.
The quantity of cores to be extracted, along with the increments per layer or horizon, is determined by the diameter of the coring tool, the size of the sampling unit, and the necessary mass of the test sample.
The constitution of the composite sample and laboratory sample is described in 7.3.
Using a coring tool equipped with an internal sheath allows for easy removal of the sheaths for transportation to the laboratory In the lab, the sheath can be opened, and the sample horizons or layers can be identified and cut Additionally, increments from the same horizon or layer can be combined, and coarse elements can be eliminated, all under more favorable conditions than those available on-site.
Preparation of the sorted sample
Increments from the same sampling unit should be collected in a clean container or plastic bag The composite sample is then spread on a clean, level, inert surface and mixed thoroughly with a shovel or appropriate tool, ensuring that clods are broken up and any coarse elements larger than the desired size are addressed.
2 cm are removed (or collected separately, depending on the objective of the study) in order to obtain a sorted sample.
In specific studies, it is essential to estimate the proportion of coarse elements relative to the mass of the sampled soil and to measure their radioactive characteristics Additionally, the petrographic nature or anthropogenic origin of rubble, along with the apparent porosity of the sample, should be documented Note that the latest tests requiring specialized techniques are excluded from this scope.
The quartering technique (see ISO 11464 [19] ) can be used to split the sorted sample to obtain a subsample of approximately 1 kg of dry matter.
All sorted samples sent to the laboratory shall be identified and a sample sheet drawn up in conformity with the instructions in 7.4.
When analyzing radionuclides in volatile compound form, it is essential to keep soil samples from different horizons separate and avoid mixing them Additionally, increments should not be combined or subjected to homogenization or clod-crushing treatments.
Identification and packaging of samples
General
Each soil sample must be placed in a non-reactive, clean container that is securely sealed to prevent loss of contents and protect against external contaminants such as water and dust.
The identification label shall be attached to the outside of the packaging.
Sample identification
The label of the container shall identify each sample and contain the following information:
— code identifying the sample, the sampling area, and the sampling unit;
— additional information, such as the depth and thickness of the soil horizon sampled, may be added.
Sample sheet
The sample sheet enclosed with the sample or series of samples shall include at least the following information:
— identification and characteristics of the sample (for example: location, depth, and thickness of the soil horizon sampled, etc.) as indicated on the packing label;
— sampling technique and the associated equipment;
— date and time the sample was taken;
— any observations necessary to interpret the results.
The topography of the sampling area, if uneven, is specified, particularly if the samples are taken from the following areas:
1) in low-lying areas (trenches, plough furrows, depressions, etc.);
2) on elevated areas (embankments, ridges, plateaus, etc.);
3) in areas where the underlying rock is exposed;
5) on the edge of the area.
When the study expresses the results of the analysis in terms of the surface activity (see Clause 9), the sheet shall also include:
— the thickness of each layer sampled;
— the mass of the sorted sample, mss;
— the mass of any sorted subsample, m′ss.
This sheet is completed, where necessary, with:
— an evaluation of area homogeneity;
— a description of the use of the land;
— a description of samples The information whether impurities such as large stones, roots, etc were removed from the sample before packaging should be included in the sampling sheet;
— the weather conditions if samples are taken following an incident or accident.
When collecting samples from various depths, it is essential to fill out the sample sheet with a detailed description of the soil horizons, highlighting the distinct layers and their physical attributes such as color, texture, structure, and the percentage of coarse elements.
Examples of sampling sheets for a single/composite sample and for a soil profile are given in Annex D and Annex E, respectively.
Transport and storage of samples
The packaged samples and their sample sheets should be transported as quickly as possible to the laboratory for analysis.
To prevent contamination, it is essential to maintain proper transport and storage conditions for the material The test report should specify the required transport and preservation temperatures for the samples when necessary.
The following are particularly recommended:
— to avoid any warming of the sample during transportation to the laboratory and to use, where possible, insulated containers;
Upon arrival at the laboratory, samples should be stored at or below 4 °C and kept in the dark if necessary, especially if there is a delay of a few days before treatment For extended storage, samples can be preserved in a freezer at −18 °C or dried at a maximum temperature of 40 °C and stored in an airtight package.
— to limit the time between sampling and radioactive analyses, especially when researching radionuclides with short half-lives;
When investigating volatile, organically bound, or highly soluble radionuclides such as iodine, tritium, and chlorine, it is crucial to implement specific precautions to prevent sample loss during storage.
It is essential to conduct measurements promptly after sample collection If subsequent tests involve determining the bulk density of samples in their natural state or assessing their water content, extra precautions must be taken to prevent compaction or water loss.
Principle
The physical processing of soil laboratory samples to measure radioactive nuclides requires drying, crushing, sieving, and homogenizing steps to be carried out.
A preliminary analysis of laboratory samples using gamma spectrometry enables the detection of volatile radionuclides, which is essential for selecting an appropriate pre-treatment procedure that ensures accurate quantification of their activity.
Laboratory equipment
The following equipment is necessary to carry out the pre-treatment of the laboratory sample:
— a ventilated drying room or drying cabinet with a temperature of (40 ± 5) °C;
— a heated, ventilated oven with a temperature of (105 ± 10) °C;
— equipment for the reduction of clods, possibly combined with a sieve, pestle and mortar, pounder, grinder, crusher, or grip breaker;
— a sieve with a 2 mm mesh size;
— a sieve with a 200 àm or 250 àm mesh size;
— a metal or plastic tray with raised edges;
— freeze-drying equipment (when appropriate).
Procedure
With consideration for the composition of the test sample, the following steps shall be carried out.
— Spread a thin layer of 1 cm to 2 cm of the entire initial test sample onto flat containers and manually break up the sample using a suitable instrument.
— Remove all remaining plant parts (tufts of grass, roots, etc.).
— Leave the sample to dry at ambient temperature or in a ventilated cabinet heated to a temperature less than 40 °C for 24 h to 48 h, according to the moisture in the sample.
— Break up the remaining clods of earth with suitable equipment.
— Separate the fine earth from the coarse elements using a 2 mm sieve and note their masses.
— Dry the powder at (105 ± 10) °C to a constant weight When measuring volatile radionuclides, it is better to freeze-dry the sample or dry it to a maximum fixed temperature of (40 ± 5) °C.
— Crush with a mortar, a mixer, or a ball mill.
— Sieve using a 200 àm or 250 àm sieve, then homogenize the powder obtained.
— Repeat the crushing and sieving steps until the entire sample has been processed.
— Weigh the total powder and the unsieved material, then discard Record the mass obtained The powder part constitutes the test sample.
The procedures outlined in ISO 11465 [22] must be followed for drying temperatures and grain sizes Any alterations to this procedure require justification and must be documented in the test report.
Operators should be aware of the potential contamination risks from the laboratory environment or from mixing samples of different layers or origins To minimize these risks, it is advisable to process samples in an increasing order of activity whenever possible.
For rapid radioactive analysis, samples can be dried directly in an oven, then crushed and sieved without the need for ambient temperature drying.
The mass of removed parts such as plants, coarse elements, and water can be weighted.
For radioactivity characterization of unsieved material larger than 200 µm or 250 µm, often derived from petrographic sources or anthropogenic origins like construction debris, the material is crushed to create a uniform powder suitable for testing.
9 Determination of the activity deposited onto the soil
General
To estimate the total amount of radionuclides deposited in the soil from sources such as radioactive gaseous effluent discharges or past atmospheric nuclear tests, soil samples should be collected from depths of 5 cm and between 20 cm to 30 cm It is important to record the thickness, \( e_i \), and the surface area, \( S_i \), of the sampled layers.
Determination using surface activity data
A specific procedure for sampling can be illustrated through a generic example involving a regular square grid In this method, five increments are collected to form a composite sample, with each increment sourced from the center and the four corners of the grid Each increment is obtained from a defined surface area, such as a frame measuring 20 cm on each side and extending to a maximum depth of 5 cm.
Figure 1 — Schematic sketch of a regular square grid and of its five increments with known surface area
The sum, S, of the areas corresponding to the soil surface increments, Si, for the five surface increments, i, is defined by Formula (1):
Five increments from the same gridding are collected in a clean container or plastic bag The composite sample is then spread on a clean, level, inert surface and mixed thoroughly with a shovel or suitable tool, ensuring that clods are broken up and coarse elements larger than a specified size are addressed.
2 cm are removed (or collected separately, depending on the objective of the study) The resulting mass, mss, of the sorted sample is noted.
The surface activity, \( A_S \), is determined from the activity per unit of mass, \( a \), when the test-sample mass, \( m_{ts} \), reflects the total mass of the sorted sample from the sampled layer, as outlined in Formula (2).
The quartering technique, as outlined in ISO 11464, is employed to divide a laboratory sample to achieve a mass of 1 kg of dry matter The test sample obtained represents a mass fraction, denoted as \$\frac{m_{ss}}{m_{ss}}\$ of the sorted sample, and the surface activity is determined using Formula (3).
Determination by integration of soil profile activity data
The operation entails comprehensive sampling throughout the contaminated area to assess the extent of surface and subsurface contamination Surface samples are collected up to a depth of 5 cm, while deeper layers are sampled in 10 cm increments or at each soil horizon change, continuing until the radionuclides of interest are no longer detectable.
The surface activity, AS, is computed from the activities per unit of mass, aj, over a soil profile of j layers using Formula (4):
The quartering technique, as outlined in ISO 11464, is employed to divide a laboratory sample to achieve a mass of 1 kg of dry matter The test sample reflects a mass fraction, denoted as \$\frac{m'_{ss}}{m_{ss}}\$ of the sorted sample, and the surface activity is determined using Formula (5).
To ensure compliance with ISO/IEC 17025, all procedures for determining the radioactivity of soil samples must be fully traceable This includes thorough documentation of the sampling strategy, the selected plan, the operations conducted during sampling, and the chain of custody for sample preparation.
Records of the sampling and laboratory procedures must be documented, with each entry dated and signed by an authorized individual to verify the accuracy of the results Additionally, any pertinent information that may have influenced the outcomes during the steps outlined in ISO 18589 should be included in the final test report.
It is essential to maintain comprehensive records of all measuring equipment used in the confirmation process of results These records must verify that each piece of equipment, such as balances and ovens, meets the specified metrological requirements Additionally, calibration certificates, verification reports, and other pertinent information should be readily accessible.
Diagram of the selection of the sampling strategy according to the objectives and the radiological characterization of the site and sampling areas
Diagram of the evolution of the sample characteristics from the sampling site to the laboratory
Example of sampling plan for a site divided in three sampling areas (A, B, C)
1 unsampled zone boundaries 6 composite sample of n increments samples
2 unsampled zone too small 7 mix and eliminate coarse elements
3 sampling unit 8 composite sorted sample
5 unsampled points: low point, outcrop 10 laboratory samples
Annex D (informative) Example of a sampling record for a single/composite sample
Sample identification: Sampling area: Sampling unit:
SAMPLING UNIT CHARACTERISTICS: SAMPLE CHARACTERISTICS number of increments
Reference topographic map: Topographic situation: Depth:
Z: Z: Z: Z: Mass a) , m’ ss : a To be completed where necessary.
NATURE OF THE SAMPLING AREA
Use of the land: NORTH
VII VI V IV III II I
Basic grid: x metres CHARACTERIZATION OF SAMPLE
Surface dose rate Special requirements needed for handling
Organic products Type of soil horizon
FOLLOW-UP (LABORATORY) ADDITIONAL INFORMATION
Search for the following radionuclides: Description of pedological profiles
Physical-chemical pedological analysisOther
Annex E (informative) Example for a sample record for a soil profile with soil description
Sample identification: Sampling area: Sampling unit:
AREA CHARACTERISTICS: SAMPLE OR SAMPLE SERIES
Reference topographic map: Topographic situation: Depth:
X: Use of the land: Surface area a) , S :
Geographical Co-ordinates Y: Mass a) m ss :
Z: Mass a) m ’ ss : a To be completed where necessary.
VII VI V IV III II I
Basic grid: x metre CHARACTERIZATION OF SAMPLES TAKEN
Number Depth Colour Texture Coarse elements
Organic products Degree of eutrophication Type of soil horizon
FOLLOW-UP (LABORATORY) ADDITIONAL INFORMATION
Search for the following elements: Description of pedological profiles
Physico-chemical pedological analysesOther
DESCRIPTION OF THE SOIL PROFILE N° horizons Soil 1 2 3 4 5 6 7 8 9 1 0 1 1
Texture Colour(s) Moisture Coarse elements Organic Roots Structure(s) Porosity Consistency Secondary elements Various
01 5 – A ll r ig ht s r es er ve d
[1] MERIWETHER J.R., BURNS S.F and BECK J.N Evaluation of soil radioactivities using pedologically based sampling techniques Health Phys 1995, 3 pp 406–409
[2] International Atomic Energy Agency 1989 Measurement of Radionuclides in Food and the
Environment Technical Report Series, No 295 Vienna
[3] IPSN, 2000 Guide méthodologique Gestion des sites industriels potentiellement contaminés par des substances radioactives
[4] UNE 73311-1, 2002 Procedimiento de toma de muestras para la determinación de la radioactividad ambiental — Parte 1: Suelos, capa superficial
[5] AKU 1999 Recommendations for the surveillance of environmental radioactivity (in German),
Loseblattsammlung des Arbeitskreises Umweltüberwachung (AKU) des Fachverbandes für Strahlenschutz e.V., November 1999, Winter M., Narrog J., Kukla W., Vilgis M (eds.) ISSN 1013-4506
[6] ISO 10381-1, Soil quality — Sampling — Part 1: Guidance on the design of sampling programmes
[7] ISO 10381-4, Soil quality — Sampling — Part 4: Guidance on the procedure for investigation of natural, near-natural and cultivated sites
[8] ISO 10381-5, Soil quality — Sampling — Part 5: Guidance on the procedure for the investigation of urban and industrial sites with regard to soil contamination
[9] RICHARD O.G., 1987 Statistical Methods for Environmental Pollution Monitoring, Van Nostrand
[10] SCHEFFER, F and SCHACHTSCHNABEL, P, 1998 Lehrbuch der Bodenkunde, 14, neu bearbeitete und erweiterte Auflage, Ferdinand Enke Verlag
[11] NUREG – 1575, EPA 402-R-97-106, DOE/EH-0624, 2000 Multi-Agency Radiation Survey and Site
[12] CEEM Comparative Evaluation of European Methods for Sampling and Sample Preparation of
[13] MUNSELL Soil Color Charts GretagMacbeth, New York, 2000
[14] PORTA J., et al 1994 Edafología para la agricultura y el medio ambiente, Ed Mundi-Prensa, Madrid
[15] DUCHAUFOUR Ph., 1995 Abrégé de pédologie, sol, végétation, environnement, MASSON (Paris)
[16] Soil Survey Staff, 1975 Soil Taxonomy A Basic System of Soil Classification for Making and
Interpreting Soil Surveys, USDA, Handbook No 436
[17] ASTM C998-90, 2005 revision Standard Practice for Sampling Surface Soil for Radionuclides
The NF M 60-790-2 standard, established in 1998, provides comprehensive guidelines for measuring radioactivity in the environment, specifically focusing on soil It outlines the criteria for selecting sampling zones, as well as best practices for soil sampling, transportation, and preservation of soil samples This guide is essential for ensuring accurate and reliable measurements of environmental radioactivity.
[19] ISO 11464, Soil quality — Pretreatment of samples for physico-chemical analysis
[20] UNE 73311-5, 2002 Procedimiento para la conservación y preparación de muestras de suelo para la determinación de radioactividad ambiental
[21] HASL – 300, 1997 The Procedures Manual of the Environmental Measurements Laboratory U.S
Department of Energy 28th Edition
[22] ISO 11465, Soil quality — Determination of dry matter and water content on a mass basis —
[23] ISO 10381-2, Soil quality — Sampling — Part 2: Guidance on sampling techniques
[24] ISO 18589-7, Measurement of radioactivity in the environment — Soil — Part 7: In situ measurement of gamma-emitting radionuclides