2. Designing environmental monitoring programmes
How to design, implement and review environmental radiological monitoring programmes. Including considerations of the source, pathway and receptors, and the level of impact associated with the site.
This section describes the process and provides guidance for designing, implementing, and reviewing environmental radiological monitoring programmes, whilst ensuring that the requirements in the developing an environmental monitoring programme section are met.
Operators should seek agreement of the monitoring objectives for their programmes from the relevant regulator and formalise the monitoring arrangements with the regulator before implementation.
When designing a new monitoring programme, it will be necessary to develop a conceptual model of the source, pathway and receptors which will include consideration of the following:
- the type of facility and the stage of its life cycle (such as commissioning, operational, decommissioning)
- information about the environment around the site, which could include the land use types (including details on agriculture), water body types, water flow rates, freshwater and seawater boundaries in estuaries, sites of accretion and erosion in rivers and estuaries
- information from existing monitoring programmes or from monitoring programmes at similar sites, in particular, this might identify likely areas where radionuclides might accumulate
- information from habit surveys (existing and, or new) that will identify what sorts of food are being consumed and from where and where people spend their time
- modelled and existing monitoring data to predict the behaviour of radionuclides in the environment around a site, taking into account meteorological conditions (such as wind speed and direction), tidal currents and so on – to help target the areas of highest activity concentration or likely activity concentrations in places which might lead to exposure of people or wildlife
- trial monitoring (for example using instruments) to investigate the areas of highest activity concentration or likely activity concentrations in places which might lead to exposure of people or wildlife
- suitability of monitoring locations to meet the required objectives, for example where the dose impact of current discharges is being assessed by monitoring estuarine sediments, an area of accreting sediment will need to be monitored
- investigate the likely spatial and temporal variability in activity concentrations at monitoring locations (important if the exact location for sampling could vary - for example due to access difficulties) to ensure that it is acceptable for the purpose of the objective, using monitoring trials or the judgement of suitably qualified and experienced persons
When reviewing an existing radiological monitoring programme, it will be necessary to consider the same factors as those for the new programmes, together with the following:
- expectations of interested parties about monitoring for assurance purposes
- impact on long-term trend data
- knowledge of optimal sample or monitoring types (for example dose rate rather than soil analysis)
Note: Guidance for undertaking habit surveys is provided by the National Dose Assessment Working Group (NDAWG).
A useful first step in designing a monitoring programme is to establish the level of impact associated with the site and the presence of sensitive receptors.
The term impact is used in a wide sense to include both environmental impacts from discharges and potential from abnormal releases, and business risks, such as reputational risks.
The magnitude of effort in designing and carrying out the monitoring programme should be commensurate with the level of impact.
Assessing the impact helps ensure proportionality requirements are met.
The levels of impact are defined as follows.
Programmes for higher impact sites
Higher impact sites are defined as those where there is the potential for abnormal releases, or the environment is complex and difficult to characterise or the dose to the representative person (modelled and assessed at discharge limits or via retrospective dose assessment when sufficient monitoring results are available) is greater than 0.01 millisievert per year (mSv/y) (threshold of optimisation (Managing Radioactive Substances and Nuclear Decommissioning: UK policy framework)) or there is high public interest.
For these sites, the monitoring programme would be expected to be comprehensive addressing all the relevant objectives and covering all the main pathways. Full quality assurance would be expected with an accredited quality management system meeting the principles of relevant ISO standards.
Programmes for lower impact sites
Lower impact sites are ones where the discharges are reasonably uniform with a low potential for abnormal releases, the environment is well characterised, the dose to the representative person (assessed as above) is less than 0.01 mSv/y for all exposure pathways and there is low public interest.
For these sites, the monitoring programme would be expected to be smaller than a programme for a higher impact site. The minimum programme may only need to address the objectives of providing assurance, and detecting abnormal, fugitive, and non-permitted releases. The quality assurance requirements can be less stringent for these programmes. A quality management system would still be required to meet the principles of the relevant ISO standards, but not necessarily accredited.
Programmes for lowest impact sites
Lowest impact sites are ones where, for example, dose from discharges to air or water are less than 0.001 mSv/y for all exposure pathways, there is no legitimate public concern and no potential for abnormal releases.
There may be no expectation to address even the minimum objectives of providing assurance, and detecting abnormal, fugitive, and non-permitted release for these sites. Consequently, an environmental radiological monitoring programme may not be required by the regulator.
Programmes for sites with potential for variable impact (such as decommissioning sites)
As site operations change and move through decommissioning (post operational clean out through care and maintenance and dismantling to land remediation), the levels of impact associated with them will change and this should be taken in to account when reviewing the programme. See the example monitoring programmes section.
Although a site’s continued environmental impact may become less, there may be activities on site that could lead to intermittent releases of radioactivity. This could be during planned operations such as systems and facilities clean-up, demolishing buildings, or fugitive emissions from waste stores. Potentially historic contamination may also be redistributed. For example, the removal of an active effluent system may result in changed handling of water on site. This in turn may affect groundwater volumes and flow resulting in the movement of contamination.
There is still a need to be alerted to these emissions and potential changes in contamination behaviour and be able to understand their impacts.
For these sites, targeted monitoring should be employed when operations with the potential for release or redistribution of contamination are being undertaken. For example, air monitoring during building demolition, or groundwater monitoring when changes are made to systems that affect water movement or buried structures are being removed.
Trigger levels for this targeted monitoring should be set and, if reached, wider monitoring of environmental receptors should be undertaken.
It is suggested to include monitoring systems within waste stores to detect emissions and if a waste store is in the open environment environmental monitoring may be included to assess impacts.
The relevant monitoring objectives should be established, when designing a routine radiological monitoring programme. The monitoring objectives which are selected will reflect who is undertaking the programme, its scope, and the site impact.
A regulator’s programme for monitoring around all nuclear sites may require most of the monitoring objectives to be achieved, whereas an operator’s programme for a single nuclear site will have a smaller number of objectives.
It is unlikely that the objectives relating to dose and impact on wildlife (Objectives A and B) will be relevant for a low impact site programme.
Operators should ensure that the regulators are satisfied with the selected monitoring objectives. For all monitoring programmes, it may be appropriate to consult with local stakeholders over the selected monitoring objectives.
Assess total representative person dose
- dose rate monitoring (terrestrial)
- dose rate monitoring (inter-tidal or marine)
- high volume air sampling
- water (tap, surface, groundwater)
- grass (dose surrogate)
- landfill leachates
- sewage or sludges
- sediment – estuary, coastal or freshwater
- seaweed
- milk and dairy products
- meat and meat products
- poultry, eggs
- fruit and vegetables
- wildlife or game
- fish – marine and freshwater
- crustaceans and molluscs – marine and freshwater
- freshwater weed
Assess total impact on wildlife
- dose rate monitoring (terrestrial)
- dose rate monitoring (inter-tidal or marine)
- water (tap, surface, groundwater)
- soil
- sediment – estuary, coastal or freshwater
- seawater collected from shore
- wildlife or game
- fish – marine and freshwater
- crustaceans and molluscs – marine and freshwater
Provide assurance
- dose rate monitoring (terrestrial) – also workforce reassurance
- dose rate monitoring (inter-tidal or marine)
- contamination monitoring (inter-tidal or marine)
- high volume air sampling
- passive shades
- total deposition
- water (tap, surface, groundwater)
- soil
- grass (dose surrogate)
- landfill leachates – also workforce reassurance (landfill operatives)
- sewage or sludges – also workforce reassurance (public sewage treatment workers)
- sediment – estuary, coastal or freshwater
- seawater collected from shore
- seaweed
- milk and dairy products
- meat and meat products
- poultry, eggs
- fruit and vegetables
- wildlife or game
- fish – marine and freshwater
- crustaceans and molluscs – marine and freshwater
- freshwater weed
Check or complementary monitoring
- dose rate monitoring (terrestrial)
- dose rate monitoring (inter-tidal or marine)
- contamination monitoring (inter-tidal or marine)
- high volume air sampling
- passive shades
- total deposition
- water (tap, surface, groundwater)
- soil
- grass
- landfill leachates
- sewage or sludges
- sediment – estuary, coastal or freshwater
- seawater collected from shore
- seaweed
- milk and dairy products
- meat and meat products
- poultry, eggs
- fruit and vegetables
- cereal (crops)
- wildlife or game
- fish – marine and freshwater
- crustaceans and molluscs – marine and freshwater
- freshwater weed
Assess background (very far field)
- dose rate monitoring (terrestrial)
- dose rate monitoring (inter-tidal or marine)
- high volume air sampling
- total deposition
- water (tap, surface, groundwater)
- soil
- grass
- sewage or sludges
- sediment – estuary, coastal or freshwater
- seawater collected from shore
- seaweed
- milk and dairy products
- meat and meat products
- poultry, eggs
- fruit and vegetables
- cereal (crops)
- wildlife or game
- fish – marine and freshwater
- crustaceans and molluscs – marine and freshwater
- freshwater weed
Assess long term trends (indicator)
- dose rate monitoring (terrestrial)
- dose rate monitoring (inter-tidal or marine)
- contamination monitoring (inter-tidal or marine)
- high volume air sampling
- passive shades
- total deposition
- water (tap, surface, groundwater)
- soil
- grass
- landfill leachates
- sewage or sludges
- sediment – estuary, coastal or freshwater
- seawater collected from shore
- seaweed
- milk and dairy products
- meat and meat products
- poultry, eggs
- fruit and vegetables
- cereal (crops)
- wildlife or game
- fish – marine and freshwater
- crustaceans and molluscs – marine and freshwater
- freshwater weed
Comply with international obligations
- high volume air sampling
- total deposition
- water (tap, surface, groundwater)
- seaweed
- milk and dairy products
- meat and meat products
- fish – marine and freshwater
- crustaceans and molluscs – marine and freshwater
Detect abnormal, fugitive and non-permitted releases (Indicator)
- dose rate monitoring (terrestrial)
- dose rate monitoring (inter-tidal or marine)
- contamination monitoring (inter-tidal or marine)
- high volume air sampling
- passive shades
- total deposition
- water (tap, surface, groundwater)
- grass
- landfill leachates
- sewage or sludges – for operators being done as part of clearance, regulators may do for public sewage treatment works
- sediment – estuary or coastal freshwater
- seawater collected from shore – scale from pipes
- seaweed
- milk and dairy products
- fruit and vegetables
- wildlife or game
- crustaceans and molluscs – marine and freshwater
- freshwater weed
Understand and monitor behaviour of radionuclides in the environment
- dose rate monitoring (terrestrial)
- dose rate monitoring (inter-tidal or marine)
- contamination monitoring (inter-tidal or marine)
- high volume air sampling
- passive shades
- total deposition
- water (tap, surface, groundwater)
- soil – only relevant for dynamic environments
- grass
- sewage or sludges
- sediment – estuary or coastal freshwater
- seawater collected from shore
- seaweed
- milk and dairy products
- meat and meat products
- fruit and vegetables
- wildlife or game
- fish – marine and freshwater
- crustaceans and molluscs – marine and freshwater
- freshwater weed
The framework for what should be monitored, where and how often, is based on an interpretation of IAEA guidance considering Environmental and source monitoring for purposes of radiation protection and the complementary report on Programmes and systems for source and environmental radiation monitoring.
Guidance on the main monitoring techniques and sample types to meet different monitoring objectives is provided in the sampling and monitoring techniques section.
Use the information in that chapter to select the monitoring and sampling types which meet the programme objectives.
The techniques associated with monitoring and sampling may also need to be tailored to meet a specific objective. These differences are indicated in the relevant sections of the sampling and monitoring techniques section.
General
Usually, the operator will undertake the main routine monitoring programme, with regulators undertaking a smaller, complementary, programme for assurance purposes.
However, some objectives are best carried out by one organisation, for examples, operators undertaking monitoring to detect abnormal, fugitive, and non-permitted releases and regulator programmes assessing backgrounds (very far field), such as through national programmes.
With programmes for lower impact sites, it may be appropriate for the regulator to carry out the monitoring to achieve a particular objective rather than the operator. This position needs to be agreed to prevent omissions.
The total number of samples or monitoring activities (monitoring locations at different times) around a nuclear site or in a national programme should fall within the range of total samples or monitoring activities per year as indicated in each section of the sampling and monitoring techniques section.
It is expected that the total number of samples or monitoring activities will lie in the bottom half of the range for programmes for lower impact sites and in the top half for programmes for higher impact sites. Indicative programme ranges are given in the relevant sections of the sampling and monitoring techniques section. A larger number of samples would be required if doses approach the dose constraint.
Often, the monitoring for one objective will satisfy the monitoring requirements for other objectives (this is indicated by their groupings in the specific sections of the sampling and monitoring techniques section), for example monitoring to assess total representative person dose (Objective A) could also embody monitoring to provide assurance (Objective C). The general exceptions are where sampling or monitoring is carried out to assess the background, impacts on wildlife (in some cases) and for detecting abnormal or fugitive releases.
Where there are national programmes designed to assess the background or comply with international requirements, additional site-specific background sampling requirements may not be required.
Considerations for sampling frequency
When deciding upon the frequency or timing of sampling, the following should be considered:
-
some objectives will require higher frequencies (such as detecting abnormal releases) whilst lower frequencies will be acceptable for other objectives, for example check monitoring (Objective D) or assessing far field backgrounds (Objective E)
- frequencies may be lower where the discharge profile is relatively stable (that is the quantities discharged are relatively similar on a month by month or quarter by quarter basis)
- monitoring may be timed to occur after a release if it occurs very infrequently
- higher frequencies may be necessary where short-lived radionuclides are being monitored
- frequencies should be consistent with the rate of change observed in the environment (for example lower rates of change will lead to lower frequencies)
- frequencies should be higher where action levels (such as those for dose constraint) are approached
- monitoring may be timed to coincide with food growing seasons or activities of members of the public (for example beach occupancy)
- if short-term measurement campaigns are being undertaken, for example for measurement of air particulate using HVAS, seasonal factors such as wind direction should be taken into consideration
Supplementary data
Where the behaviour of radionuclides can be affected by changing environmental conditions such as meteorology or river flow, consideration should also be given to collecting supplementary data for example wind direction and wind speed or sediment grain size. This could be used to:
- optimise the position of monitoring points
- confirm the source of any unusual or elevated measurements
Specific radionuclides should be selected for the monitoring programme, based on the source term (considering the magnitude of release and environmental impact) and radionuclides limited by permits, including those that could be released as fugitive emissions.
For current discharges, analysis should be considered for:
- radionuclides which are limited in the permits
- significant components of a group limit (for example strontium-90 limited under any other beta or gamma emitting radionuclide group limit)
- radionuclides required as a result of international obligations
- radionuclides required for background monitoring
Proven surrogate radionuclides may be used (such as where the radionuclide fingerprint is relatively stable).
For historical discharges, and potential abnormal releases (also of relevance to decommissioning sites) account needs to be taken of what radionuclides have been or could be expected to be released. As for current discharges, the programme can be optimised to those radionuclides giving the highest dose or known to accumulate in the environment and proven surrogates could be used.
For both current and historical discharges, in-growth of progeny may need to be considered (such as americium-241 from plutonium-241).
Results need to be appropriate for the monitoring objective for which they are gathered, for example limits of detection need to be stringent enough to allow useful data to be generated, but not too onerous as to incur excessive cost. As a guide, limits of detection should be of the order of the activity concentration which could give rise to a dose of 0.0003 mSv/y for the dose related objective (Objective A) and providing assurance objective (Objective C). This is to ensure that retrospective dose assessments are not overly conservative. For the indicator objectives (Objectives F and H) they should be no higher than 10% of the peak concentration.
Different analytical methods can be used, again considering the use to which the data will be put and whether a screening value (such as from a gross measurement or quick turnaround method) is good enough or accurate information is required.
Samples containing radionuclides with short radioactive half-lives need to be analysed quickly. The speed with which an analysis can be undertaken will also be important where there is a need to have an early warning of abnormal or fugitive release. In this case, there will be a balance between the speed of the analysis to satisfy the early warning requirement and ensuring that the results are of sufficient quality, particularly as there may only be a few results.
Only a limited set of radionuclides need be analysed for samples collected to meet the assessment of long-term trends objective (Objective F).
Once the programme has been devised, it should be shared with the regulator. Also, any inter-dependent elements, such as the sharing of samples between the regulator and operator programmes on the grounds of sustainability or particular samples meeting the check monitoring objective should be agreed.
For new monitoring programme related to new facilities or operations, the monitoring should commence prior to operations starting so that a baseline of environmental activity concentrations can be established. Note this is not the same as site baseline monitoring prior to development of a new nuclear site or discharge, which is outside the scope of this guidance.
As an example, for a new nuclear power station the operator and regulator monitoring programmes should start 3 years and 1 year, respectively, prior to fuel being brought on site.
For existing programmes where a review has been undertaken a good change over point to the revised programme is the beginning of a calendar year.
To ensure the effectiveness and quality of the monitoring programme audits should be undertaken this would typically be a high-level audit undertaken every 1 to 2 years depending on the site’s impact, with a more thorough audit within a 3 to 5-year timeframe.
Both operator and regulator programmes should be subject to review on a periodic basis, this would typically be an annual high-level review, with a more thorough review within a 3 to 5-year timeframe. The frequency of this will be dependent on the variability of discharges and environmental concentration and the availability of new information (such as habit surveys, changes on site (operational to decommissioning, change of decommissioning activity), changes in farming practices).
It may be appropriate for the review to involve local communities and to ensure they are aware of the results of the programme and can raise issues.
The review should consider whether the objectives for the monitoring programme are still valid. If other objectives are identified, these may already be achievable through the current programme, if not, further monitoring would be required. If objectives are no longer required care needs to be given to removing monitoring to ensure that samples are not being removed that are still required to meet other objectives.
If over time the results are consistent and at, or close to, the limit of detection and there is a decreasing discharge profile the frequency of monitoring could be reduced. The number of locations (spatial distribution) could also be reduced if the data collected are showing the same trends and similar magnitude of results.
Reviews should take place as a site’s status changes, for example moving into decommissioning, change of decommissioning activity or a period of care and maintenance.
Operators should inform the Environment Agency in advance, in writing, of any proposed significant modifications to the monitoring programme.