Should we evacuate elderly people in a nuclear or radiological accident?

There is an interesting talk on the ICRP’s ICRP Digital Workshop: The Future of RP by Jessica Callen-Kovtunova entitled Making ICRP Recommendations ‘Fit for Purpose’ for the Response to a Nuclear or Radiological Emergency.

In this she reports a meta-analysis of 600+ papers which reviewed the impact of protective actions and claims that for every 1000 people evacuated we may expect 7 deaths among the general public due to dislocations caused by the protective action and between 15 and 117 among residents of facilities for long stays and the elderly as well as between 120 – 220 mental health problems.

They compare this to 5 deaths prevented by evacuating 1000 people with an averted dose of 100 mSv each (this appears to be based on the ICRP-103 approximation of the overall fatal risk coefficient of 5% per sievert).

They conclude that: “Taking protective actions consistent with dose criteria used in many countries could result in far more excess deaths than hypothetical excess radiation-induced deaths prevented.  We must include these effects to protect people effectively.”

If we agree with these findings, and before doing that I’d like a closer look at the applicability of the evidence, we must ensure that the current ERL for evacuation is reconsidered and its application to homes for the elderly, in particular, given very careful thought.

If we start to think about different protective action thresholds for different age groups maybe we could also consider stopping planning to give those over 40 -50 years old stable iodine.

Keeping the ICRP Recommendations Fit for Purpose

The science behind radiological protection is complex. It starts with the physical interaction between ionising radiations and the material that composes the human body (and other biota), then considers the potential changes induced by these interactions, including the response of different issues within the body and the whole body implications of those local responses, and tries to quantify the harm that might be done (detriment). It then considers the acceptability of this harm in terms of the tolerability of risks and by putting them into perspective with other risks.  It also considers how different groups and individuals might respond if exposed, recognising workers, the public and patients as different groups with different potential gains and losses and planned, existing and emergency exposure situations. The field thus encompasses physics, biology, sociology, ethics and politics.

The International Commission on Radiological Protection was “established to advance for the public benefit the science of radiological protection, in particular by providing recommendations and guidance on all aspects of protection against ionising radiation. The Main Commission is the governing body, setting policy and giving general direction” (Ref).  The recommendations of the ICRP form the basis of radiological protection around the globe. A useful review of the effects of this last major restatement of the recommendations can be found in a PHE paper “Application of the 2007 Recommendations of the ICRP to the UK”. (Ref)

ICRP have now pre-released a major discussion document as an early step in the consultation process for the next round of recommendations. Christopher Clement et al 2021 J. Radiol. Prot. in press. On line (updated version) available at This article is based on the accepted manuscript 20 July 2021.

In this we are reminded that the objective of the system of radiological protection described in ICRP-103 is “to contribute to an appropriate level of protection for people and the environment against the detrimental effects of radiation exposure without unduly limiting the desirable human actions that may be associated with such exposure”. The review that preceded this document started 20 years ago and took 10 years. “While it is safe to conclude that the System is robust and has performed well in relation to the protection objectives, the System must adapt to address changes in science and society to remain fit for purpose.

It is suggested that the ICRP-103 objective to prevent tissue reactions (deterministic effects to us oldies) should be modified to recognise that there are medial situations, emergency situations (and space exploration) where tissue reactions may be tolerated to achieve the desirable benefit of a particular activity. This seems sensible but is going to add, rather than remove, complexity.

A review of the lifetime risk estimates imbedded in the concept of detriment is due a review to reflect the evolution of scientific knowledge of risks and expert judgement. “In addition, explicit recognition of differences in detriment with age at exposure and between males and females could improve the clarity of application of the System, showing, in particular, that risks to young children are greater than risks to adults, and that risks to older individuals are low.” This could be useful, for example, in removing the perceived need to evacuate elderly people from their homes during a radiological or nuclear emergency to avert radiation doses of as little as 30 mSv which are of no real threat to them.

The discussion paper points out that the current system “principally deals with health effects resulting directly from exposure to radiation” which is not entirely in line with the WHO definition of health as “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”. Including mental and social wellbeing in the system can only make it much more complicated, situation dependent and subjective (but pretty much removes the need to worry about the physics of the fundamental interactions).

There is a section (Section 2.3) on the protection of the environment and non-human biota. I have always considered this a job creation scheme for radiobiologists and mathematical modellers (of which I used to be one) and of little practical value in the real world of radiation safety. I realise that this view sees me ejected from the moral high ground.

In Section 2.5 the paper reports that “There have been many requests for more guidance on how to balance societal, economic, and other factors in the optimisation of protection and safety, requiring input from many fields of expertise” and summarises the work that ICRP have published in this general area. This includes ICRP Task Group 114 which seems to suggest that there are occasions where the lowest exposures or risks are sought when a better balance could be achieved to advantage.

Also in this section is a discussion of a more holistic approach in safety assessments of medical facilities. Again, this seems to be running the risk of making the system more complex and maybe asking too much of one stream of work.

Section 2.6 discusses dose limitation and worries that, since it only applies to planned exposure situations, it fails the “ethical obligation to protect individual people under all circumstances”. This seems to me to be a bit like worrying that the seat belt and airbags in my car don’t provide me with any protection when I am walking around a shopping centre.

The report suggests a broader principle which would apply in all situations and encompass the concepts of limits, constraints and reference levels, possibly combining the latter two concepts into one. This is an interesting thought, worth thinking about provided the ICRP are willing to back peddle if it does not work out as hoped.

Dose constraint

A prospective and source-related restriction on the individual dose from a source, which provides a basic level of protection for the most highly exposed individuals from a source and serves as an upper bound on the dose in optimisation of protection for that source. For occupational exposures, the dose constraint is a value of individual dose used to limit the range of options considered in the process of optimisation. For public exposure, the dose constraint is an upper bound on the annual doses that members of the public should receive from the planned operation of any controlled source.

Reference level

In emergency or existing controllable exposure situations, this represents the level of dose or risk, above which it is judged to be inappropriate to plan to allow exposures to occur, and below which optimisation of protection should be implemented. The chosen value for a reference level will depend upon the prevailing circumstances of the exposure under consideration.


The report states that “defining a fundamental principle to protect the individual would result in a System where all three fundamental principles apply under all circumstances regardless of the exposure situation or category. This change would require the re-examination and clarification of the distinctions between limits, constraints, and reference levels”. (I’m not sure how you can put a useful dose limit on an accident or malicious use of radiation).

Section 2.7 suggests that the experience of using the three exposure situations introduced by ICRP-103 has led to the opportunity to update, clarify and expand the guidance. This seems reasonable and the application to space travel interesting.

ICRP identify ethics, communications and stakeholder involvement and education and training as important overarching considerations and briefing discuss each in turn in Section 3.

It is proposed to use absorbed dose (in gray) for the control of doses to individual organs and tissues for the avoidance or minimisation of tissue reactions leaving equivalent dose (in sievert) as an intermediate step in the calculation of effective dose. “Radiation weighting could then be considered separately for tissue reactions and stochastic effects for the calculation of radiation-weighted absorbed dose in Gy and effective dose in Sv, respectively.” This is intended to “apply scientific knowledge more appropriately and simplify radiological protection, with a clearer distinction between organ/tissue doses in absorbed dose in Gy and effective dose in Sv”. This does seem more transparent than the switch we currently make from seiverts to grey at (an arbitrary) high dose as at low dose you are concerned about stochastic effects and high doses with tissue reaction.

The paper reports discussions with ICRU with the intention that “the measured quantities for the estimation of effective dose would be related directly to effective dose in the reference phantoms, renamed as ‘dose quantities’ (ambient and personal dose) rather than ‘dose equivalent quantities’. Operational quantities for the measurement of doses to the skin and lens of the eye will become ‘absorbed dose quantities’”. Another episode where those of us who work around radiological protection are required to forget the hard learned jargon we work with and replace it with a different set.

In Section 4.2, discussing effective dose, the paper discusses the increased use of more accurate and differentiated anthropomorphic phantoms leading to more accurate and transparent values of detriment and relative detriment separately for males and females of different age groups. The report suggests that “Revisions to the methodology of calculation of effective dose could improve its suitability for the assessment of risk. Best estimates of health risk should be calculated using estimates of absorbed doses to organs/tissues and age- and sex-specific risk models for individual types of cancer, but risk estimates at low doses will still be subject to the uncertainties inherent in risk projection models”. The question this raise in my mind is “are the age and sex differences larger than the uncertainties in the estimates?”

It is suggested in Section 4.4 that the revision of dose per unit intake values in the light of the new recommendations should be more rapid than previous experiences due to preparatory work and experience gained. This seems to be a reasonable hope.

Section 5 suggests a review of the classification of radiation effects as either stochastic effects or harmful tissue reactions to ensure that it remains fir for purpose, suggesting that “For example, for protection purposes, it may be useful to distinguish between severe and other tissue reactions, or between short-term and long-term health effects”. This seems reasonable. There are occasions where the gain from a process may be worth suffering a mild or temporary tissue effect.

Since the last recommendation were made there has been considerable research and epidemiological study of the impacts of low exposures to ionising radiation. A Task Group is currently reviewing the linear no threshold assumption in the light of this work. It looks likely to survive.

It is almost certain that different people have different susceptibility to harm from ionising radiation but likely that there is insufficient information to include this in a system to protect workers and the public. “However, there are already efforts to individualise radiological protection of patients which should be considered in the review of the System, taking into account scientific, ethical, and practical aspects”.

Similarly, there is now more information on heritable effects that should be considered.

Likewise, there is more data on relative biological effectiveness and it is likely that a more sophisticated approach may now be appropriate.

The idea that “detriment could be calculated separately for males and females and at different ages at exposure, and the corresponding values of relative detriment could be used directly in the calculation of effective dose, rather than the current use of simplified age- and sex-averaged tissue weighting factors” sounds good. As does “explicit treatment of detriment from irradiation in utero could also be re-evaluated”.

There will also be a conversation about the replacing detriment with other proposed measures of harm such as fatality or disability-adjusted life years.

The discussion paper concludes that “The last review of the System of Radiological Protection was initiated 23 years ago, and the current General Recommendations (ICRP, 2007) were published 14 years ago. The System has performed well and remains robust, and there are significant practical benefits to stability in the System. Nonetheless, it must progress to remain fit for purpose as society evolves, scientific understanding advances, and new uses of ionising radiation emerge”.

The ICRP and others continue to research the effects of ionising radiation on people, biota and the environment. A time comes when the strengths and weaknesses of the current system should be discussed and new knowledge should be systematically reviewed incorporated into a revised international system of radiological protection. It appears that that time is approaching. This paper is one step in the consultation process. An ICRP Digital Workshop on 19 – 20th October is another step (Ref).

I shall watch this process develop with interest and get involved if I deem it good use of my time.






FEMA – Key Planning Factors and Considerations

What would you do?FEMA report

…if a dozen dead birds are found near a truck accident site?

…if 20 people complain of tingling in the mouth after eating at a fast-food restaurant?

FEMA have some answers. They have published a new 324-page document discussing key planning factors and considerations for response to and recovery from a chemical incident August 2021).

The report shows the potential complexity of responding to a chemical event. Unlike radiological events, chemical events could result in overwhelming numbers of acute casualties, some of which require urgent medical attention with the correct treatments and anti-toxins for the chemical involved – which may not be identified at the start of the event. First responders may be in immediate danger from the contamination themselves, something that is not likely to be true to the same extent for radiological emergencies.

There are broad similarities between the response to a chemical event and to a radiological event (a dangerous substance that can move with air and/or water movements, the need to make decisions with weak information, a complex issue to explain to the public while needing them to urgently take heed of advice, a potentially complex recovery process) but also important differences (rapid onset of medical crisis, wider range of substances to understand).

The FEMA report provides brief details of several chemical accidents, showing the range of events that are included in this class and the complexity of response. It also identifies and discusses the characteristics that are common to chemical accidents which includes the fact that their on-set can be rapid, a quick and effective response is required to save lives, first responders can become exposed, decisions need to be made quickly with a limited understanding of what has occurred, large areas can be affected, communications with the public and between responders is important, medical facilities can be overwhelmed and recovery may take a long time.

It then lists seven Key Planning Factors (KPF), each of which is then given a chapter:

    1.   “Prime the Pump” Pre-Event Planning;
    2.   Recognize and characterise the Incident;
    3.   Communicate with External Partners and the Public;
    4.   Control the Spread of Contamination;
    5.   Augment Provision of Mass Care and Human Services to Affected   Population;
    6.   Augment Provision of Health and Medical Services to Affected   Population;
    7.   Augment Essential Services to Achieve Recovery Outcomes.

It justifies pre-planning with the observation that “A large-scale chemical incident with mass casualties is a realistic threat facing both urban and rural communities nationwide. The risk of misuse or accidents involving toxic industrial chemicals (TIC), which are widely stored in large quantities and are routinely transported by rail, waterway, highway, and pipeline, is substantial”. They also believe that a terror attack using chemicals is credible.

Multiagency planning and preparation are required to face this threat and enable a prompt and effective response. A “whole community” concept of operations is suggested.

The report suggests a systematic approach to planning and preparedness with several discrete steps recommended, each of which is explained in detail with lists of suggested consultees, reference documents, check lists and resource requirements.

It stresses the importance of agreeing how decisions will be made suggesting a process whereby stakeholders agree which decisions will need to be made, the minimum information needed to make them and the potential sources for that information. Decision making processes should be established to select among available options for evacuation, shelter-in-place, decontamination and waste management balancing political/social priorities and public health protection against time and cost constraints, and, therefore, should include discussion of reimbursement/ compensation for resources provided and contingencies if resources are damaged, destroyed, etc.

Another important area for discussion is medical resources. The planning process should establish protocols and procedures for the prioritization of medical resources.

There are a range of ways in which a chemical event can become known – this varies from automatic alarms on chemical plant, reports of smells or gas clouds, reports of unexplained illnesses or collapses of people or animals, active monitoring of public spaces and food. The quicker these signs can be picked up the better. The report discusses possible indicators, what they might mean and how best to use them. By considering what signs might be available and what they might mean in advance the planners increase the likelihood that an event can be detected earlier allowing a better response.

The next step is to characterise the release and its extent with the safety of first responders as a high priority. This requires equipment, training and coordination.

There is a nice discussion about atmospheric dispersion and modelling.

The third KPF refers to communication with external partners and the public. It stresses the importance of communication to enable a coordinated response across multiple agencies, jurisdictions and levels of authority and to inform the public providing key information and advice on self-preservation while countering misinformation and misperceptions.

The section discusses how communications can support a coordinated response, how to inform the public, how to provide time-critical messaging, strategies for effective communications, and best practice (the latter being a useful checklist of 13 elements).

Controlling the spread of contamination (KPF 4) may save lives and will protect the environment. Depending on the nature of the incident, controlling the spread of contamination may involve environmental containment and/or remediation efforts; decontamination of people, goods, or property; and interventions such as evacuations and food recalls. A lot of important decisions may be needed, and considerable expertise and resource bought to bear.

The support of the affected population (Augment provision of mass care and human services to affected population) (KPF-5) provides life-sustaining and human services to disaster- affected populations, including feeding operations, emergency first aid, distribution of emergency items, and family reunification. Additional resources and services may need to be mobilized to support individuals with disabilities, limited mobility, limited English proficiency, children, household pets, and service and assistance animals. Mass evacuations result in a varied group requiring a range of support services.

The basic objective for Emergency Mass Care is to provide for basic survival needs including food, water, emergency supplies, and a safe, sanitary, and secure environment but hopefully it would go beyond that and cater for other needs, reducing the potential for psychological harm.

The report discusses the support that sheltered and evacuated populations might have and the multi-agency strategies that might be considered to prepare to meet these needs, the facilities that may be required to manage evacuations, provide respite, assistance and shelter.

KPF 6 is concerned with augmenting the provision of health and medical services to the affected population. A chemical event could result in a rapid build-up of casualties requiring specialist assistance, including determination of the active agent, the appropriate medical care and the steps required to protect the responders and medical facilities from contamination.

The report discusses medical treatment for chemical casualties which may require that the symptoms presented are treated while the active agent is unknown i.e. provision of oxygen to those exposed to a lung irritant.

The report mentions “CHEMPACKS” which are containers of nerve agent antidotes placed in safe locations around the country (the USA). I do not know if this system is replicated in the UK. The report recognises limitations to this system.

The Tokyo nerve agent attack in March 1995 was serious – 12 people died, 54 were severely injured, and around 980 were mildly to moderately affected. However, most of the 5000-seeking help, many of them with psychogenic symptoms, were understandably worried that they might have been exposed. This demonstrates the value of rapid information dissemination via the media in reassuring the public. It also shows the importance of effective triage at receiving centres in ensuring that medical resources are reserved for those who really have been exposed.

The final KPF is “augment essential services to achieve recovery outcomes”. This section suggests that recovery begins during the planning and response phases. It divides the recovery into three overlapping stages: short term (days), intermediate (weeks – months) and long term (months – years).

Activities and resources needed to attain recovery outcomes will vary depending on the scenario, context, and location of the chemical incident as well as the incident’s impacts on the local infrastructure, economy, and workforce.

The overall objectives of recovery plans and prioritizations are to restore critical services as quickly as possible to limit cascading effects, and to return the affected community to a sense of normality.

After discussing each of the KPFs the report discusses federal preparedness, response and recovery, outlining the four escalating tiers of federal response. These are (1) an on-scene coordinator assessing the situation and watching the response (2) escalation to invoke the National Oil and Hazardous Substances Pollution Contingency Plan (3) a request to the Department of Homeland Security for coordination capabilities and additional federal agency support (4) a Presidential Disaster Declaration under the Stafford Act. These are discussed in turn with examples.

The report provides links to a wide range of additional information and both planning and response tools. Appendices provide a wealth of information including an overview of nine common toxidromes (syndromes caused by exposure to dangerous levels of toxins), a review of US chemical incident policy, legislation and regulation and chemical planning and notification requirements for responsible parties, environmental containment and remediation options, a flow chart showing how medical attention can be targeted and coordinated.

This is a detailed document covering a wide range of material. For a person with responsibility for planning for, or responding to, a chemical incident in the US it is probably a must read. For people with similar responsibilities elsewhere it is a recommended read – read it and compare your level of readiness with that described.




Dirty bombs and malicious source placement

There are a couple of reports of interest to local authority nuclear emergency planners in a recent Journal of Radiological Protection (Volume 40, Number 4, December 2020). These are part of the European Commission’s CATO mission which “proposes to develop a comprehensive Open Toolbox for dealing with CBRN crises due to terrorist attacks using non-conventional weapons or on facilities with CBRN material” (

The first comes from the Belgium Nuclear Research Center with Carlos Rojas-Palma as the lead author (Carlos Rojas-Palma et al 2020 J. Radiol. Prot. 40 1205). This reports on a series of experiments in which mocked up Dirty Bombs of a variety of designs were detonated in urban-like environments. These used a number of tracers to represent the radioactive elements and a variety of detection and measure techniques to record the dispersion.

The report is constrained by security concerns so is unfortunately a bit coy about some of the important details.

Following a ground level explosion activity was found up to 5 m high on nearby walls and that the activity on the ground at 30 m was about 5 % of that at 9 m. They concluded that most of the dispersion was ballistic rather than turbulent. Whereas that might be true in this case, or even in most cases, it might not always be true; it could be assumed to depend on the physical form of the radioactive source and its packing and the force, temperature and geometry of the explosion.

The authors state that, in this instance, the radiological red zone would extend beyond a 50 m perimeter but, without any idea of the effective source strength and the blast being published the value of this observation is greatly reduced.

The paper suggests that any aid or movement of severely injured victims would ideally be performed by personnel in full protective equipment.

Airborne radiation levels can remain elevated for tens of minutes. This is affected by the weather conditions and the layout of buildings. Respiratory protection should be considered for anyone working in the red zone.

The levels of deposition on dummies placed in the vicinity of the blast suggest that decontamination will be needed for people within 50 m of the blast and monitoring, prior to release or decontamination, for those further out.

Deposition on walls was significantly lower than that on the ground but it is suggested that a thorough decontamination of the surrounding area would be needed to satisfy public demand.

For a device detonated in a car the distribution of ground deposition was rather random, making surveying and reporting harder and more time consuming. It was suggested that the fraction of radioactivity remaining in the vehicle would pose difficulties for forensic investigations.

This is a limited report of a series of careful experiments. It is to be hoped that the full results are available to, and explained to, the relevant emergency planners and first responders.

The second report, also with Carlos Rojas-Palma as the lead author (Carlos Rojas-Palma et al 2020 J. Radiol. Prot. 40 1286), discusses retrospective dosimetry to assist in the radiological triage of mass casualties exposed to ionising radiation. It suggests that the outcome of a terrorist event could be mass casualties with radiation exposure of individuals ranging from very low to life threatening and in numbers that surpass the capability of any single laboratory. Thus, it argues, an international network of laboratories would be needed. The European RENEB network is such a network (according to their website at PHE is a member). A paper outlining their objectives is available at

This report discusses a series of exposure experiments with a 0.65 TBq and a 1.5 TBq Ir-192 sources, a bus and a collection of water-filled canisters and anthropomorphic phantoms. Detectors included a range of TLDs (Thermoluminescent dosimeter), OSLs (Optically Stimulated Luminescence) and body-temperature blood samples.

The project achieved three things: measurements of the doses that could be accrued by people sitting on a bus near an unshielded radioactive source, an inter-comparison of the reading of dosimeters by different laboratories and the evaluation of newly developed retrospective dosimetry methods. “Retrospective dosimetry” allows the doses of accidently exposed people to be measured after the event and can be used to inform the medical care they receive.

IAEA Integrated Regulatory Review Service (IRRS) visits ONR

In October 2019 there was an IAEA Integrated Regulatory Review Service (IRRS) visit to the UK. Its report can be found <here>.

The IAEA state that: “The Integrated Regulatory Review Service helps host States strengthen and enhance the effectiveness of their regulatory infrastructure for nuclear, radiation, radioactive waste and transport safety.

IRRS teams evaluate a State’s regulatory infrastructure for safety against IAEA safety standards. The teams compile their findings in reports that provide recommendations and suggestions for improvement, and note good practices that can be adapted for use elsewhere to strengthen safety. Mission reports describe the effectiveness of the regulatory oversight of nuclear, radiation, radioactive waste and transport safety and highlight how it can be further strengthened”. <here>

Prior to the visit the UK authorities conducted a self-assessment and presented a preliminary action plan and supporting documents. The IRRS team, which consisted of 18 senior regulatory experts from 14 IAEA Member States, 2 IAEA staff members and 1 IAEA administrative assistant, and 3 observers, reviewed these and a number of other documents before their visit and then spent two very busy weeks in the UK. This included interviews with 16 regulatory bodies and governmental departments.

Of particular interest to me are the references to emergency planning.

The mission commented that the “emergency planning zones established under REPPIR 2019 are not fully in alignment with the requirements of GSR part 7”. They recommend that the “Government should review the UK EP&R framework to explain how the requirements of GSR Part 7 are met in terms of planning zones and distances, and if any gap exists develop appropriate regulatory requirements”.

We must remember that GSR part 7 is IAEA advice and its section 2 states that it is “established in addition to and not in place of other applicable requirements, such as those of relevant binding conventions and national laws and regulations”. It goes on to say that where there is conflict between the GSR-7 and other requirements “the government or the regulatory body, as appropriate, shall determine which requirements are to be enforced”. I would expect that the ONR would have to champion UK regulation over IAEA advice.

We know that the UK “planning zones” do not match those of the IAEA. The UK zones have developed over many years and have, in the past, suited the UK emergency planning framework. REPPIR-19 was an opportunity to undertake a review of planning zones but it was an opportunity missed. The current system of a DEPZ with a torturous definition and an arbitrary outline planning zone does nobody any favours.

GSR-7 defines a precautionary action zone (PAZ) where arrangements are made to implement urgent protective actions and other responses before any significant release in order avoid or to minimize SEVERE DETERMINISTIC effects. This is severe accident territory and a release profile consistent with older designs of contained reactors for which a containment failure after several days of heating up was conceivable. So the PAZ as described in GSR-7 does not seem to make a great deal of sense in the modern world.

The next IAEA zone is the urgent protective action planning zone (UPZ). This is an area where arrangements have been made to initiate urgent protective actions and other response actions, if possible before any significant release of radioactive material occurs, on the basis of conditions at the facility, and after a release occurs, on the basis of monitoring and assessment of the radiological situation off the site, in order to reduce the risk of stochastic effects. This is broadly similar to the plans at many British sites where some protective actions are initiated on declaration and then thought is given to extending their scope and range if conditions merit it. It is important to realise that, in the UK, the default protective action areas are contained within the DEPZ but not defined by it.

The IAEA have an extended planning distance (EPD), beyond the urgent protective action planning zone, for which arrangements are made to implement further protective actions if monitoring and assessment on the day show that they may reduce stochastic effects if implemented within a day to a week or up to a few weeks following a significant radioactive release. UK outline planning and the gap between the automatic protective action zone and the DEPZ, sort of covers this zone.

Finally the IAEA define an ingestion and commodities planning distance (ICPD) beyond the extended planning distance where plans are in place to protect the food chain and water supply. That this zone is missing in the UK regulation does not mean that the relevant protective actions are not given the attention they deserve. The control of potentially contaminated food and drink is covered in REPPIR-19 (it is part of the operator’s consequence report and mentioned throughout guidance).

The “zones” are a bit arbitrary; are a planning tool and are best reserved for describing the national concept of operations to be applied to a fleet of reactor sites rather than to a particular site. Excellent emergency plans could be written without any use of the terms DEPZ and OPZ. What really matters is that the emergency plan is capable of initiating sensible default protective actions without delay and then rapidly considering the situation and responding to the particular characteristic of the emergency as those characteristics emerge.

I’d prefer to see a process in which the protective actions comes first and the zones second. Sensible plan compontents include:

  • On-site. UK plans tend to be quiet about what happens to the people (possibly several hundred) on the site. I’ve heard reservations about evacuating the site despite the fact that it is probably the only sensible thing to do because it will alarm sheltering residents. Cooping employees up in “mustering stations” i.e. the works canteen does not seem viable beyond a few hours and provides them with little protection.
  • An automatic protective action plan where shelter/exclusion and stable iodine are pre-planned in detail and initiated without discussion on declaration over an area likely to require them in a reasonably foreseeable emergency. (This could be a keyhole shape informed by the wind direction on the day).
  • A deliberative protective action plan that looks at how the protective actions of shelter and stable iodine could be extended further downwind if required and under what circumstances. This plan should detail the monitoring required to support decision making, the decision making process and how the protective actions will be achieved in a timely manner.
  • An agricultural precautionary protective action plan, where thought is given to how far downwind food interventions might be needed as an automatic action and as a deliberated action, what these might be and how they might be achieved. Informing farmers of the implications of this would be part of the public information cycle.
  • An evacuation plan looking at the circumstances under which authorities might want to evacuate areas close to the site (including the potentially hundreds of people on the site) and how it could be done.
  • A communication plan considering how people in the area will be informed of the plans and their parts in them, before any event and how they will be alerted and advised on the day. 

The US concepts of “plume exposure zone” and “ingestion pathway emergency planning zone” are rather more logical than the IAEA ones.

Neither the GSR-7 or REPPIR-19 planning zones definitions are ideal. Since REPPIR-19 has recently been introduced and the planning zones all reviewed there is likely to be little appetite in the UK to make any changes so it will be interesting to see how the ONR cope with this recommendation.

Plant Data

Another observation made by the mission was that “ONR does not have previously agreed format for plant data and information transfer during an emergency” coupled with the suggestion that “ONR should consider establishing pre-defined communication with the operating organizations in terms of plant data and other information during emergencies”.

The big questions here are “what plant data would be useful to ONR?” and “What would they do with it if they had it?”

If ONR were going to analyse plant data in real time and use it to generate advice to the local responders and the national government they would have to greatly extend their expertise in reactor accident management. This would only be a good idea if (a) there is something worth measuring i.e. there are parameters such as temperature, pressure, radiation levels, flow rates that can give the responders better knowledge of what is happening and what is likely to happen next (b) that data is measured and displayed somewhere (c) the ONR know what it means and will definitely be there to interpret it and (d) we don’t really trust the operator to correctly analyse and report the situation.

If ONR just need the data to be better informed spectators then I’d rather not bother.

I remember talking around this subject several times in relation to the rather primitive Magnox reactors. The conclusion was that there were very few parameters that were useful and could be measured and transmitted after a major cooling circuit failure and ignition of a fuel channel fire or two and unless they had happened there wasn’t really a problem. We always thought it would be different with PWRs which have far more instruments and loss of cooling accident sequences with periods where temperatures and pressures could be rising and threatening containment integrity.


Another observation was that “The RCIS provides ONR with adequate infrastructure to respond in emergencies and its staff has been increased significantly in recent years. However, ONR does not have an overarching emergency response plan that defines its response objectives, the organizational response structure and functions, how the response actions are coordinated within the RCIS and its external stakeholders, etc. There are RCIS procedures for each position; however, these procedures are not linked together with an overarching document. The new ONR management system, under development, does not currently include a sub-process of ONR EP&R capability maintenance”.

It is a bit surprising that ONR has such a large structure and has recently extended it without actually articulating its objectives. I wonder if everyone has the same view about what it is for.

The mission goes on to observe that “the ONR does not have an overarching emergency response and preparedness plan to coordinate the response functions and maintain response capability within the RCIS. The action plan identified the ONR does not have a formal training and qualification programme for its staff responding to an emergency” and suggests that “The ONR should consider integrating its response arrangements into a response and preparedness plan and formalize training and qualification of emergency response staff”. This could be summarised as “if you are going to do something, understand why you are doing it, work out how you are going to do it and make sure your people know how to do it on the day”. On the face of it, this is sensible advice. 

Having been on both sides of this type of exercise I recognise that only a small fraction of the worth of the exercise is held in the final report. Being on the receiving side and trying to justify your plans and planning process against a polite but sustained challenge from a team of experts who are used to looking at things differently forces you to think deep in a way that the day job seldom does. You learn a lot.

Similarly being on the away team you read reports and think you’ve found gaps but, in discussion, you become to realise that different is not wrong and often where you see gaps you’ve missed the filling in a different component of the plan. They do some things, maybe a lot of things differently to you and many of them they do better than you. Everybody learns, everybody wins.

Keith Pearce, January 2021

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  I’ll develop this page further as time goes by.

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  I’ll develop this page further as time goes by.

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.

The Chilca Incident – industrial over-exposure

The Chilca Incident

The IAEA have published a very detailed review of this event and the learning to be gained from it.


A serious radiological accident occurred in Peru around midnight on 11 January 2012 during non-destructive testing in the district of Chilca, in the Cañete Province of Lima. An iridium-192 source in a radiography camera being used to test pipeline joints became stuck inside the guide tube, resulting in three workers being overexposed to ionizing radiation.

Pipes were being welded together and a radiography camera was being used to determine the quality of the welds. The equipment used consisted of a 192Ir source inside a shield (see picture). When an exposure is required a remote winding mechanism is used to move the source from inside the shield, along a tube and into collimator – this produces a beam of gamma rays that are used to make the measurement.

The process involves attaching the collimator and guide tube to one side of the pipe being tested and an unexposed film to the other side of the pipe, then retreating, winding

Device used to store and deploy radiation source

the source out, making the exposure and then winding the source in and repeating. The blackening of the film shows where gamma rays have been less well attenuated and can highlight defects in the weld or pipe wall. The team of three took 97 exposures during a night shift. Finishing at 02:20 on 12 January 2012.

The company provided the workers with a kit that included a set of tools and equipment for operational and personal safety. However, the two assistants, Co-worker 1 and Co-worker 2, left their personal dosimeters in the transportation vehicle; thus, Worker 1 was the only worker wearing a personal dosimeter. None of the workers used alarming dosimeters or direct reading dosimeters. They did not adequately test that the source was returning to the shield at the end of each exposure.

At the end of the shift, when the equipment was being dismantled, it was discovered that the source had not returned to its housing.

At 02.30 worker 1 was sick and he continued to be sick for the next few hours. In the course of the night co-worker1 experienced fatigue and co-worker 2 dizziness.

On investigation it was found that some of the films were overexposed.

On 15 January 2012 erythema (redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries which occurs with any skin injury, infection, or inflammation and is a symptom of radiation burning) appeared on the left hand index finger of Worker 1. The company then realized that the workers had been overexposed to radiation.

The Peruvian Institute of Nuclear Energy (IPEN) was alerted and responded by recommending hospitalisation of the three workers. A formal request for assistance (the first of three as the situation developed) was sent from IPEN to the IAEA on 20 January 2012 under the Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency (the Assistance Convention) for dose reconstruction and medical advice. International support helped to understand the medical conditions of the exposed workers and determine their treatment, to understand the doses received and to consider further actions.

The prodromal symptoms of the three were carefully recorded and they were subjected to close examination and observation. The three patients were classified in accordance with the Medical Treatment Protocols for Radiation Accident Victims (METREPOL) system. This considers neurovascular, haematological, cutaneous and gastrointestinal issues and rates each person on a scale of 1 (minimum severity) to 4 (maximum severity) for each. Consideration of the symptoms displayed, the time to onset and their severity allows the doctors to estimate the dose and dose distribution received by a patient and this allows them to predict the course of their illness and to determine the most appropriate treatment.

Worker 1 was the most severely exposed to radiation during the accident. He received a significantly heterogeneous whole body dose of 1.8 Gy (with 75% of the body having received a dose in the range of 4 Gy), as well as doses ranging from 20 to 50 Gy to the extremities of both hands. He was subject to a programme of care and investigation in Peru, Chile and in France. He received reconstructive surgery and cell therapy (mesenchymal stem cells (MSCs) or MSC injections) but still had to have parts of his hand amputated on day 101 after the event.

It was concluded that the work had been badly managed. The trained radiological protection officer was not present, the equipment had been assembled by an untrained person, no attempt had been made to confirm the correct retraction of the source, there were no alarming dosimeters and two of the team were not wearing the supplied dosimeters. This shows poor application of rules and guidance and a poor safety culture.

An observation was that “significant time (6 d) was taken to recognize the radiological nature of the accident, despite the availability of substantial evidence and clinical manifestations. Consequently, as has happened in many other radiological accidents, valuable time was lost before the workers were given appropriate medical evaluation and treatment.” It is suggested that doctors should be trained to suspect and to identify the effects of radiation when patients present with the symptoms of acute radiation syndrome or their case history suggests it is possible.

It was observed that there were problems associated with the analysis of samples and with the sending samples by airline as they demanded confirmation that they were not dangerous. There were also delays with treatment, particularly treatment abroad, on cost grounds, the workers lacking insurance.

The important message here is that these accidents happen and are continuing to happen. Could it happen in the UK? We would like to think not but it only takes a few mistakes with this type of equipment to result in over-exposure. Would it be detected more quickly? We would like to think so. There is at least a suggestion that the workers involved were not open with their initial reports as they feared blame for failing to work to procedures more than they feared the consequences of overexposure and delayed treatment.

This could happen in any county in the UK. It is worth being aware of that and considering how the local authority would react to an event in their area.