IAEA Nuclear Security Series No. 41‑T

Technical Guidance Preparation, Conduct and Evaluation of Exercises for Detection of and Response to Acts Involving Nuclear and Other Radioactive Material out of Regulatory Control

The IAEA’s Nuclear Security Series provides international consensus guidance on all aspects of nuclear security to support States as they work to fulfil their responsibility for nuclear security. The IAEA states that “The overall objective of a State’s nuclear security regime is to protect persons, property, society, and the environment from the harmful consequences of a nuclear security event. With the aim of achieving this objective, States should establish, implement, maintain and sustain an effective and appropriate nuclear security regime to prevent, detect and respond to such events. The nuclear security regime covers nuclear material and other radioactive material, whether it is under or out of regulatory control, and associated facilities and associated activities throughout their lifetimes.

The steps on the way to achieving this include the development of a national detection strategy, the development of detection systems and the processes to monitor and act upon alarms. The response to a genuine event includes notification and confirmation/assessment, location and categorisation, recovery of sources and collection and preservation of evidence. These are explained in detail in IAEA Nuclear Security Series No. 15.

There is an expectation stated in paragraph 6.21 that “The State should carry out exercises under the plan using credible scenarios. Competent authorities should perform exercises and drills at regular intervals, in order to evaluate the effectiveness of the plan. When possible, States should consider participating in regional and international exercises and drills.” IAEA Nuclear Security Series No. 41‑T gives a comprehensive account of how these could be managed.

Exercises can be based on a structured and moderated discussion (a table top exercise) or on activities performed in an operational or field situation to enact a realistic scenario in a manner that simulates, to some extent, the stress and practical constraints of an actual incident (a drill or field training exercise).

The steps taken to plan an exercise include:

  • Determination of the key activities to be exercised – the scope and objectives of the exercise;
  • The format and type of exercise, identifying the constraints that these impose;
  • Agreeing a planning timeline with the key stakeholders;
  • Developing and approving an exercise scenario;
  • Identifying the exercise participants and their roles and determining how any gaps where organisations are not playing will be filled;
  • Developing evaluation criteria.

The report goes through these steps in more detail giving useful advice and warnings as it does. It defines the roles of Exercise Director and exercise planning team; controllers and facilitators, evaluators and players and the support from media spokesperson, observers, safety officer, qualified expert in radiation protection and the rapporteur.

Section 4 of the report discusses: setting up the exercise and preparing for exercise safety; providing exercise briefings; conducting exercise play; and holding debriefing activities and section 5 evaluation.

Appendix 1 gives a useful list of example key activities and actions while Annexes give templates for exercise planning, exercise documentation, assessment and feedback forms and exercise reports as well as an example exercise scenario.

This report is a useful read and contains useful resources for anyone planning such an exercise.

What is the case for the nuclear emergency planning community’s snobbishness about improvised respiratory protection for the general public?

In my many years as an emergency planner in the nuclear industry I’ve never heard a real debate about respiratory protection as a public protective action in the event of an accidental atmospheric release of radioactivity. It has always been dismissed because without proper masks and fit testing the protection factors offered are compromised.

In 1981 the IAEA [1] identified that respiratory protection was one way to reduce dose uptake in workers and members of the public. It recognised that high levels of protection require properly designed and fitted devices and realised that these would only be available to those with planned roles in a response. They accepted that if any use is to be made of such measures by the public, the simple equipment and techniques to be employed can only be of a very rudimentary nature.

They provided a quite extensive table of filtration factors for common materials. This included the finding that 16 layers of man’s cotton handkerchiefs provides a geometric mean efficiency of 94.2% against aerosols of 1-5 μm particle size – a protection factor not to be sneezed at. At eight layers the efficiency drops to 88.9%. A single bath towel is worth 73.9%.

The public, they said, “can be advised to use such simple items while proceeding to take shelter, and possibly during sheltering. Similar precautions could be recommended while members of the public were being evacuated from a contaminated area”.

In 2002 the US NCR published a document [2] which suggested that improvised respiratory protection can be used as a secondary protective action that can be used to provide a nontrivial level of additional protection. They also provide a table of protection factors.

In 2007 IAEA stated that [3] “Improvised respiratory protection (e.g. a wet cloth over the mouth and nose) has been shown to be effective but it has not been demonstrated that the public will apply it effectively during an emergency. Improvised respiratory protection should not be assumed to provide adequate protection from an inhalation hazard and therefore its implementation should not be allowed to interfere with evacuation or sheltering”. This does not say that improvised respiratory protection should not be recommended under any circumstances; it just says it should not be used instead of shelter or evacuation.

The latest advice on the protection of the public in the event of a nuclear accident from PHE [4] makes no mention at all of RPE, improvised or otherwise. This publication suggests a dose reduction factor of 0.6 for inhalation dose from shelter in place over the period of a release.

So why have we taken improvised respiratory protection out of our tool box of techniques to reduce public dose? It seems to offer protection factors at least comparable with shelter in place for particulate activity.

We worry about golf courses and caravan parks within our DEPZs where shelter in place is considered likely to be ineffective. Could we at least provide a supply of half decent face masks with the stable iodine tablets we store at these establishments as a secondary protection while thinking about evacuation?

Does the Covid-19 experience that shows that large fractions of the population will wear face masks when advised and has made them far more available to the public change our current attitude?


  1. IAEA, Safety Series No. 55, Planning for Off-Site Response to Radiation Accidents in Nuclear Facilities
  2. US NCR, Perspectives on Reactor Safety, NUREG/CR-6042, Rev. 2 SAND 93-0971
  3. IAEA Safety Standards Series No. GS-G-2.1, Arrangements for Preparedness for a Nuclear or Radiological Emergency (2007), https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1265web.pdf
  4. PHE, Public Health Protection in Radiation Emergencies, PHE-CRCE-049, (2019).

Learning for nuclear emergency planning from COVID-19?

The model of the UK response to a nuclear emergency that results, or may result, in a plume of radioactive material spreading across populated areas of the countryside is to get the local responders, notably the local authority, emergency services and health services, in one place to discuss, decide, coordinate and respond.

Within the model is a unit called the Science and Technical Advise Cell (STAC) with the mission “to ensure timely coordinated scientific and technical advice during the response to an emergency”. We were told that “The STAC should bring together technical experts from those agencies involved in the response and who may provide scientific and technical advice to the Gold Commander. The purpose of the cell would be to ensure that, as far as possible, scientific or technical debate was contained within the cell so that the SCG (and others involved in the response) received the best possible advice based on the available information in a timely, coordinated and understandable way.”

Implicit in this process is the assumption that in any event there is an objective truth and that if scientists chat about it for a while they will determine and understand that truth and be able to explain it to the decision makers who have been too busy on other aspects of the response to explore the science for themselves. The decision makers will be jolly grateful to the STAC and, armed with the scientific consensus, will go on to make the right decisions. They might even say time after time that they are being driven by the science.

In this ideal world, these decisions will be reported to the public and to the media, will be implemented and the crisis will be bought to a close. Also in this ideal world the decisions turn out to be the “right” decisions and the only decisions that could be considered to be “right”, all other options, explored and unexplored, being “wrong”.

One thing we have definitely seen with the coverage of Covid-19 is that the media will not just forward your advice to the public as you might hope. Instead they will turn out an army of interpreters who, fearful that Mrs Miggins and her neighbours will not understand that those in a defined area are being asked to shelter and those outside the area are not, will explain at length what they think “shelter” means and why it has been recommended. They will then find a talking head to explain it again and then another to say that the previous interpretation was wrong and that the public should be being advised to do something else entirely. They will summarise by saying that there is a lack of clarity in what the advice is and who it applies to before cutting to a member of the public who will confirm, in response to a loaded question, that they don’t understand the advice and that they are very worried.

Returning to the decision making, the major issue is that the science does not give all the answers. We may be able to estimate radiation doses to the public, with and without protective actions, but these will be educated guesses rather than accurate. The amount of dose saved (benefit) that makes a protective action (with a cost) worthwhile is debatable and probably different for different people in different situations. The decision to interrupt the lives of people and ask them to stay in their homes knocking back stable iodine tablets is therefore a judgement call not the outcome of a neat equation. This is particularly true when you realise that the estimates of future doses are horribly dependent on assumptions made about what is happening, and what is going to happen, in the bowels of a damaged nuclear facility, what the weather will be when the activity gets out and where the members of the public will be and what they will be doing. Again the media will bring out an army of “experts” to discuss the technology, the science and the decision making process and will argue that the science is debatable, the process flawed and that any of the decisions made are dubious.

Maybe what should happen is that advisors advise and decision makers decide. The spokesperson issuing the advice should state that the decisions have been taken by the Strategic Coordination Group who took into account scientific advice, advice about the incident and how it could develop and the concerns of and for the people affected.

The media should be asked to transmit the advice as given and to resist reheating and reinterpreting it.

That will work.

What are the lessons for the nuclear industry from Covid-19? How do we ensure that our protective action decision making process is robust, transparent, unambiguous and trusted to ensure a high level of public compliance and optimum dose reduction?

DEPZ Determinations under REPPIR-19

I am interested to see what impact on DEPZs we see following the introduction of REPPIR-19 and the bizarre way they are now set. With REPPIR-01 the size and shape of the DEPZ was in the gift of the ONR who had a cumbersome process covering technical, practical and strategic issues (see here). They had detailed discussions with the operator about the site’s safety case and the potential for accident. In this discussion both sides fielded teams of experts, well versed in safety cases and nuclear emergency plans. These discussions could take years.

In REPPIR-19 the safety case still exists and is still discussed at great length between the teams of experts within the operator and ONR organisation. This is a never ending cycle of review and revision.

Under regulation 4 of REPPIR the operator “must make a written evaluation before any work with ionising radiation is carried out for the first time at those premises” (a later clause includes continuing work) and must be “sufficient to identify all hazards arising from the work which have the potential to cause a radiation emergency”. The operator must provide “details of the evaluation” to the ONR. We start to move away from the safety case. Intriguingly this regulation does not require the ONR to bless the work but we can safely assume that if they think it substandard they will require a discussion and a revision. Can’t we?

Under regulation 5 the operator must make an assessment to consider and evaluate a full range of possible consequences of the identified radiation emergencies. This also goes to the ONR but, again, no blessing is mentioned in the regulation.

Regulation 7 requires that the operator produce a consequence report and send it to the local authority. This report is not even a précis of the large body of work that has gone on before. It tells the local authority where the site is, recommends a minimum size for the DEPZ, and discusses which protective actions may be required promptly and how far downwind they should go. This is a very brief document.

Regulation 11 then requires the local authority to consult with a range of organisations and set a DEPZ. What seems to be happening is a local authority officer writes a paper for the council setting out the options (in some cases that might be “this is the proposed DEPZ accept or reject?”). This is discussed at a meeting at which it may not be the only matter to discuss and either rejected or accepted. Did I mention that the local authorities were given a matter of weeks between receiving the consequence reports and having to set the DEPZ by law?

So setting the size of the DEPZ has gone from being in the remit of the national regulator, with teams of experts and able to take their time and apply the same policy uniformly across the UK, to a rushed decision by local authorities who are reassured in the guidance that they don’t need to understand the technical background to the subject. That will work.

I’ll keep track of DEPZ determinations at http://www.katmal.co.uk/reppir2019progress.html .

REPPIR-19 Implementation progress

I’m interested to see the impact of REPPIR-19. Yesterday (22/2/2020) was the day that REPPIR-19 comes fully into force and all duty holders were required to be compliant.

Searching the internet I’ve not been about to find all of the publications expected. Those I have found are listed at katmal.co.uk/REPPIR2019progress.html.  I’ll develop this page further as time goes by.

The physics of the Chernobyl accident

My latest book, an attempt to explain the Chernobyl accident to people who know a bit about physics but not a lot, placing it between the many accounts that have concentrated on the human story and some very technical reports, is now available on amazon after a professional work over by Art Works who have greatly improved the layout and type setting.

Find it at https://amzn.to/33lHN6w

What do we know about Covid-19?

Since everybody seems to be writing about Covid-19 I thought I should as well.

Update.  There is now a cacophony of Covid-19 writing. I'm not even going to try to stay up to date, let alone write anything more.

COVID-19 is the illness seen in people infected with a new strain of coronavirus not previously seen in humans. On 31st December 2019, Chinese authorities notified the World Health Organisation (WHO) of an outbreak of pneumonia in Wuhan City, which was later classified as a new disease: COVID-19. Based on current evidence, the main symptoms of COVID-19 are a cough, a high temperature and, in severe cases, shortness of breath.

On 30th January 2020, the WHO declared the outbreak of COVID-19 a “Public Health Emergency of International Concern”.

COVID-19 is now classified as an airborne high consequence infectious disease (HCID) in the UK.

Situation reports are available from:

Printed situation reports (worldwide – WHO) are available from: https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reports

The world situation can be monitored at https://experience.arcgis.com/experience/685d0ace521648f8a5beeeee1b9125cd

UK Government latest information and advice is available from: https://www.gov.uk/guidance/coronavirus-covid-19-information-for-the-public

The numbers of confirmed cases in the UK is going to be published daily at 2pm each day on https://www.gov.uk/guidance/coronavirus-covid-19-information-for-the-public#number-of-cases

The table above is from 6/3/20

The Government also maintain a site giving updates on Covid-19: epidemiology, virology and clinical features. https://www.gov.uk/government/publications/wuhan-novel-coronavirus-background-information/wuhan-novel-coronavirus-epidemiology-virology-and-clinical-features

On 30/1/2020 the government raised the UK risk level from low to moderate. https://www.gov.uk/government/news/statement-from-the-four-uk-chief-medical-officers-on-novel-coronavirus


It is not yet clear how this virus will spread and the impact it will have. However, as of 4th March 2020 it is spreading widely across the world and there appears to be an exponentially increasing number of cases in the UK. Business have been advised to plan for 20% absenteeism at the peak.

The government summary of what is known about the virus may be a bit out of date – this is a fast moving event. It does say that “Although evidence is still emerging, information to date indicates human-to-human transmission is occurring. Hence, precautions to prevent human-to-human transmission are appropriate for both suspected and confirmed cases” and “We do not know the routes of transmission of COVID-19; however, other coronaviruses are mainly transmitted by large respiratory droplets and direct or indirect contact with infected secretions. In addition to respiratory secretions, other coronaviruses have been detected in blood, faeces and urine.”

“Fever, cough or chest tightness, and dyspnoea are the main symptoms reported. While most patients have a mild illness, severe cases are also being reported, some of whom require intensive care.”

When you have dyspnea, you might feel:

  • Out of breath,
  • Tightness in your chest
  • Hungry for air (you might hear this called air hunger)
  • Unable to breathe deeply
  • Like you can’t breathe (suffocation)

As of 3 March, a total of 13,911 people have been tested in the UK, of which 13,860 were confirmed negative. 51 were confirmed as positive (up to 85 on the 4th March).

We might expect the number of cases to rise rapidly over a period and then start to drop. The peak intensity and the duration of the disruption is hard to predict. The “social distancing” strategy is intended to reduce the height of the peak but at the expense of increasing the duration. There is a distinct possibility of repeat outbreaks in subsequent years, although these days we can hope that a vaccine will be developed. Each wave can have different inflection rates and different fatality rates. The figure below shows the 3 different waves of illness in the USA during the 1918 flu pandemic.


Figure ref < here>

Government Strategy

(https://www.gov.uk/government/news/health-secretary-sets-out-government-battle-plan-for-covid-19 1st March)

Every government department to have a designated ministerial virus lead to help oversee government response to the global threat of COVID-19

Cross-government ‘war room’ of communications experts and scientists also set up ahead of public information blitz in coming weeks

Further COBRs planned this week, with ministerial COBR meetings upgraded to be held more frequently, if required.


The overall phases of the Government plan to respond to COVID-19 are:

  • Contain: detect early cases, follow up close contacts, and prevent the disease taking hold in this country for as long as is reasonably possible
  • Delay: slow the spread in this country, if it does take hold, lowering the peak impact and pushing it away from the winter season
  • Research: better understand the virus and the actions that will lessen its effect on the UK population; innovate responses including diagnostics, drugs and vaccines; use the evidence to inform the development of the most effective models of care
  • Mitigate: provide the best care possible for people who become ill, support hospitals to maintain essential services and ensure ongoing support for people ill in the community to minimise the overall impact of the disease on society, public services and on the economy.


These phase may have run its course with an increasing number of cases confirmed in the UK. (At this stage care is needed when interpreting the rise in confirmed cases. It may be more representative of the rise in testing rather the rise in cases).


The delay phase of the response will probably be based on public information campaigns urging hygiene, social distancing and recognition of symptoms. The intention is a lower the peak incident rate but probably at the cost of prolonging the course of the epidemic.

The government concern about planning for this stage is that the proposed actions have a social impact (and an economic one).

The company would probably prefer a longer duration, relatively shallow event rather than a shorter, sharper one that compromises site safety by having too many people off at once. At company efforts should focus on delay, at least initially.


For an operational site or company the mitigate stage is about maintaining site safety at all times and remaining fleet of foot to achieve what production is possible.

What happens when you have a suspect carrier on site?

For contacts of a suspected case in the workplace, no restrictions or special control measures are required while laboratory test results for COVID19 are awaited. In particular, there is no need to close the workplace or send other staff home at this point. Most possible cases [currently] turn out to be negative. Therefore, until the outcome of test results is known there is no action that the workplace needs to take. (COVID-19: guidance for employers and businesses).

The Company should consider implementing a policy of “social distancing” and added cleaning.

If it is confirmed that a carrier has been on site the PHE will carry out a risk assessment and give advice to the management (We can imagine that this will only continue to happen if the number of cases remains low).

Self-certification and isolation advice

The self-isolation advice given by NHS-UK is https://www.nhs.uk/conditions/coronavirus-covid-19/.

If there’s a chance you could have coronavirus, you may be asked to stay away from other people (self-isolate).

This means you should:

  • stay at home
  • not go to work, school or public places
  • not use public transport or taxis
  • ask friends, family members or delivery services to do errands for you
  • try to avoid visitors to your home – it’s OK for friends, family or delivery drivers to drop off food

You may need to do this for up to 14 days to help reduce the possible spread of infection.

Home isolation advice can be found at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/869149/PHE_Guidance_Advice_sheet_for_home_isolation_English.pdf and for sharing a house with someone in home isolation at https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/869261/PHE_Advice_sheet_for_people_who_live_in_the_same_accommodation_as_the_patient_English.pdf

By law, medical evidence is not required for the first 7 days of sickness. After 7 days, it is for the employer to determine what evidence they require, if any, from the employee. (A) Any company should agree and promulgate its policy for sick pay if the virus hits.

Employees may be advised to isolate themselves and not to work in contact with other people by NHS 111 or PHE if they are a carrier of, or have been in contact with, an infectious or contagious disease, such as COVID-19. (A) Again any company needs clear guidance on behaviour and pay under these circumstances.

Office cleaning

Coronavirus symptoms are similar to a flu-like illness and include cough, fever, or shortness of breath. Once symptomatic, all surfaces that the person has come into contact with must be cleaned including:

  • all surfaces and objects which are visibly contaminated with body fluids
  • all potentially contaminated high-contact areas such as toilets, door handles, telephones

Public areas where a symptomatic individual has passed through and spent minimal time in (such as corridors) but which are not visibly contaminated with body fluids do not need to be specially cleaned and disinfected.

If a person becomes ill in a shared space, these should be cleaned using disposable cloths and household detergents, according to current recommended workplace legislation and practice.

Guidance to the cleaners about personnel protective equipment (water proof gloves) and cleaning chemicals to use when cleaning potentially contaminated areas should be clear and transparent. (A) Write and promulgate enhanced cleaning regime for shared areas and for areas that might be infected.

All waste that has been in contact with the individual, including used tissues, and masks if used, should be put in a plastic rubbish bag and tied when full. The plastic bag should then be placed in a second bin bag and tied. It should be put in a safe place and marked for storage until the result is available. If the individual tests negative, this can be put in the normal waste.

Should the individual test positive, you will be instructed what to do with the waste.

How to protect your self

This section based on WHO advice https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public

Wash your hands frequently

Regularly and thoroughly clean your hands with an alcohol-based hand rub or wash them with soap and water.   Why? Washing your hands with soap and water or using alcohol-based hand rub kills viruses that may be on your hands.

How long any respiratory virus survives will depend on a number of factors, for example:

  • what surface the virus is on
  • whether it is exposed to sunlight
  • differences in temperature and humidity
  • exposure to cleaning products

Under most circumstances, the amount of infectious virus on any contaminated surfaces is likely to have decreased significantly by 72 hours.

Once similar viruses are transferred to hands, they survive for very short lengths of time. Regular cleaning of frequently touched hard surfaces and hands will, therefore, help to reduce the risk of infection.

Maintain social distancing

Maintain at least 1 metre (3 feet) distance between yourself and anyone who is coughing or sneezing. Why? When someone coughs or sneezes they spray small liquid droplets from their nose or mouth which may contain virus. If you are too close, you can breathe in the droplets, including the COVID-19 virus if the person coughing has the disease.

Avoid touching eyes, nose and mouth

Why? Hands touch many surfaces and can pick up viruses. Once contaminated, hands can transfer the virus to your eyes, nose or mouth. From there, the virus can enter your body and can make you sick.

Practice respiratory hygiene

Make sure you, and the people around you, follow good respiratory hygiene. This means covering your mouth and nose with your bent elbow or tissue when you cough or sneeze. Then dispose of the used tissue immediately.

Why? Droplets spread virus. By following good respiratory hygiene you protect the people around you from viruses such as cold, flu and COVID-19.

If you have fever, cough and difficulty breathing, seek medical care early

Stay home if you feel unwell. If you have a fever, cough and difficulty breathing, seek medical attention and call in advance. Follow the directions of your local health authority.

Why? National and local authorities will have the most up to date information on the situation in your area. Calling in advance will allow your health care provider to quickly direct you to the right health facility. This will also protect you and help prevent spread of viruses and other infections.

Stay informed and follow advice given by your healthcare provider

Stay informed on the latest developments about COVID-19. Follow advice given by your healthcare provider, your national and local public health authority or your employer on how to protect yourself and others from COVID-19.

Why? National and local authorities will have the most up to date information on whether COVID-19 is spreading in your area. They are best placed to advise on what people in your area should be doing to protect themselves.


Despite a further review of all the available evidence up to 30 November 2012 there is still limited evidence to suggest that use of face masks and/or respirators in health care setting can provide significant protection against infection with influenza when in close contact with infected patients. The effectiveness of masks and respirators is likely to be linked to consistent, correct usage and compliance; this remains a major challenge – both in the context of a formal study and in everyday practice. (https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/316198/Masks_and_Respirators_Science_Review.pdf

Employees are not recommended to wear facemasks (also known as surgical masks or respirators) to protect against the virus. Facemasks are only recommended to be worn by symptomatic individuals (advised by a healthcare worker) to reduce the risk of transmitting the infection to other people. (COVID-19: guidance for employers and business

Guidelines on soil and vegetable sampling for radiological monitoring. IAEA, Technical Reports Series No. 486

[Report here  IAEA, tech Rep No. 486]

This publication addresses the sampling of soil and vegetation in terrestrial ecosystems, including agricultural, forest and urban environments, contaminated with radionuclides from events such as radiation accidents, radiological incidents and former nuclear activities.

A big issue with surveys of radioactivity in soil and vegetable following a major atmospheric release of radioisotopes is the complexity. We are generally interested in the dose implications of the release to people. There are various pathways to take into account; inhalation dose, cloud dose, ground dose, resuspension dose, direct contamination of foods and uptake into the food chain. You have the situation where a cloud with a range of radionuclides with a range of physical and chemical forms meets a highly complex and heterogeneous system i.e. the real world. How do you decide what to measure? How do you ensure that your measurements are representative? What are your monitoring objectives?

A monitoring programme might be required after a nuclear accident and should be implemented:

  • To help safeguard the environment;
  • To assess hazard, risk and effective response arrangements;
  • To provide public reassurance;
  • To assess the impact on wildlife;
  • To assess the dose to a representative person;
  • To generate data to serve as a reliable database, to establish a baseline, or to substantiate compliance with laws and regulations;
  • To provide an independent check on the monitoring or modelling undertaken;
  • To detect abnormal, fugitive and unauthorized releases;
  • To support legal or regulatory action or to be used in ascertaining compensation and liability in case of spills or accidents;
  • To delineate boundaries for clean areas or to establish priorities and thresholds for the cleanup of contaminated sites;
  • To ascertain the type of treatment or disposal required for cleaning contaminated sites;
  • To understand or assess the long term trends on the behaviour of radionuclides in the environment or the accumulated impact from licensed discharges.

Chapter 2 states that “soil and vegetation can become contaminated when radioactive solids, liquids or vapours are deposited on the surface, mixed with the soil or contaminated from a groundwater source”. It then goes on to discuss some of the factors that affect the fate of deposited radionuclides and the pathways by which people can be exposed to radiation dose (external radiation, skin contamination, inhalation and ingestion).

The IAEA report gives a number of lists of factors that should be considered when a sampling programme is designed. It warns that many sampling programmes fail to achieve their aims because of a failure to take account of the many variables that affect radionuclide movement in the environment.

Warnings such as “the inhomogeneous distribution of contaminants is often the largest contributor to uncertainty in the data and is usually not quantified”; “It is not uncommon for the concentrations of target analytics in soil samples collected within a short distance (e.g. 1 m) to have differences of 50–100%”, “Extreme spatial heterogeneity, such as the presence of ‘hot’ particles (particles of anomalously high activity) in samples can cause large errors in extrapolating the data”; “It is therefore necessary to know about: (i) the source of radioactive contamination; (ii) the physical and chemical characteristics of the radioactive material; and (iii) its depth migration into soils to obtain a representative sample from a field site” are sprinkled through the report.

The report identifies a number of different sampling strategies, judgemental sampling; simple random sampling; two stage sampling; stratified sampling; systematic grid sampling; systematic random sampling; cluster sampling; double sampling; search sampling; transect sampling. They define each of these strategies and have a useful table suggesting which might be appropriate for differ objectives (Table 2.1). This would be a very useful discussion to read prior to starting a major new sampling programme.

There is also a useful discussion about treating the variability of contamination within an area as being composed of three components; the trend across the site, localised variations (hot spots) and random variations. This analysis helps make sense of the distribution of results if applied appropriately.

Section 2.4.1 contains a discussion about the migration of radionuclides downwards into the ground. This depends on the chemical properties of the radionuclide and the soil in question. For example tritium can migrate with soil water and penetrate below root depth very quickly. On the other hand most plutonium is found in the surface few centimetres years after deposition.

An optimal sampling programme achieves the maximum number of objectives, is undertaken in accordance with appropriate quality standards. It is also fundamental that performance criteria (e.g. monitoring and sampling uncertainty, detection limits and confidence levels) are set to meet the objectives, while simultaneously ensuring proportionality and taking account of the urgency of the information required.

In-situ gamma spectroscopy can yield large area data more quickly. These can be undertaken from manned helicopter or fixed wing aircraft, drones at various heights and speeds, vehicles or carried by personnel. Different equipment used in different ways gives a different layer of information. The higher, faster processes cover more area at the expense of detail, good for finding major hot spots. Slower, lower surveys give more idea of local variation. All tend to be variants of a detector (these come with a range of resolutions and efficiencies) coupled to a GPS and a data logger. In practice a layered approach is often optimum.

An approach mentioned by the IAEA is to take a series of measurements, maybe over a number of evenly spaced grid points, and to declare an area as uniformly contaminated if the variation of each measurement from the mean is less than a pre-set value (30% is mentioned). If the variation is greater than this then the area should be subdivided.

The differences in sampling residential, agricultural and forested areas is discussed.

Chapter four discusses the tools and methodologies for sampling in useful detail. Chapter five is about sample preparation. Six quality assurance and seven safety.

Case studies, including in depth reviews of the sampling around Chernobyl and Fukushima, makes up the remainder of the report.

This report is an excellent introduction to environmental sampling. It explains much of the complexity, which many people would underestimate, in an easy to understand manner.

New article in Nuclear Engineering International

I’m pleased to have another article published in Nuclear Engineering International. This one is about EdF’s excellent in-van gamma spectroscopy system which will improve the speed and accuracy of off-site dose estimates if there is ever an off-site release.