Ionising Radiations Regulations 2017 (IRR17) Guidance - Part 4 - Designated Areas

Part 4 of this IRR17 guide presents the requirements for designated areas (including specific requirements for controlled areas). Radiation Protection Supervisors (RPS), Local Rules and monitoring of areas is also included. We will particularly deal with a common issue where no designated area is required (e.g. small security x-ray machine at an airport where physical entry to the cabinet it not possible). The regulations imply that local rules and RPS are not required where there is no designated area. We will explain why we strongly advise that local rules and RPS are always present.

  • IRR17 (17) - Designation of controlled or supervised areas
  • IRR17 (18) - Local rules and radiation protection supervisors part 1
  • IRR17 (18) - Local rules and radiation protection supervisors part 2
  • IRR17 (19) - Additional requirements for designated areas
  • IRR17 (20) - Monitoring of Designated Areas

IRR17 (17) - Designation of controlled or supervised areas

Schedule 4 of IRR17 details the matters for mandatory consultation with a Radiation Protection Adviser (RPA). The role of the RPA is considered in IRR17 - Regulation 14 (Radiation protection adviser). The designation of controlled and supervised areas is one of the matters requiring mandatory consultation.

Controlled Areas

Following a suitable risk assessment (IRR17 - Regulations 8), the employer needs to designate an area under their control as a Controlled Area, where the following apply:

  • it is necessary for a person who enters the area to follow special procedures designed to restrict exposure, or prevent or limit a radiation accident; or
  • the exposure of an employee is likely to exceed 6mSv whole body dose a year, or 15mSv to the lens of the eye, or three-tenths of any relevant dose limit in Schedule 3 of IRR17 (for employees aged 18 and over).

Special procedures in the above paragraph refer to more than ‘generic safety procedures’ which would ordinarily be applied in the area regardless (i.e. simple good safety practice). These procedures must be specifically designed for the purpose of radiation protection.

Likely to exceed means during routine work and during any reasonably foreseeable radiation accident. For many employers designation is based on the potential for a reasonably foreseeable accident, rather than expected annual occupational exposures for routine work. Other employers designate on the basis of the safety systems and checks required, prior to and during exit from, an area where high radiation exposures are imminent. Examples of this would be the 'search and lock-up' of an industrial radiography enclosure prior to exposing a radioactive source, or exiting a radiotherapy room ('last person out button') prior to treating a patient. In these circumstances, it is common to be aware of visual (active signage) and audible alarm signals to warn all persons that radiation exposure is imminent (or the the radiation system is being prepared to emit radiation).

With respect to numerical limits, IRR17 does not go further than the above criteria. The IRR17 ACoP does include additional criteria for controlled area designation which are where:

  • the external dose rate exceeds 7.5 micro Sv/h when averaged over a working day. It should be noted that designation is still required when the dose rate is less than 7.5micro Sv/h, but where special procedures are required to meet IRR17 (9)
  • the hands of an employee can enter an area and the 8-hour time average dose rate exceeds 75 micro Sv per hour
  • there is a significant risk of spreading radioactive contamination outside the working area (the RPA can advise on significant risk)
  • it is necessary to prevent (or closely supervise access to the area by employees who are not directly connected to the radiation work (relevant to the industrial radiography and radiotherapy examples provided above )
  • employees are liable to work in the area for a period sufficient to receive an effective dose of 6mSv / year (legally correct but a rare reason to designate these days)
  • employees untrained in radiation protection are likely to enter that area where the dose rate exceeds 7.5 micro Sv/h (averaged over one minute)
  • where the dose rate is less than 7.5 micro Sv/h when averaged over a working day, but the instantaneous dose rate at any point exceeds 100 micro Sv/h
  • where industrial site radiography is taking place where the dose rate exceeds 7.5 micro Sv/h when averaged over one minute.

The bullet point 'where the dose rate is less than 7.5 micro Sv/h when averaged over a working day, but the instantaneous dose rate at any point exceeds 100 micro Sv/h' can be inverted to read (with some caution) 'no controlled area required where instantaneous dose rate (IDR) exceeds 7.5 micro Sv/h, where the dose rate averaged over a working day is < 7.5 micro Sv / h, as long as the IDR dose rate does not exceed 100 micro Sv/h'. The use of this derived definition, keeping in mind all the bullet points above, is useful for shielding justification of radiotherapy bunkers (and similar facilities), where the IDR might clearly exceed 7.5 micro Sv/h, but where time averaging analysis shows that the micro-Sv-in-any-one-hour is substantially less than 7.5 micro Sv, (generally less than 0.15 micro Sv for a UK facility where persons untrained in radiation protection have access, such as public areas). [0.15 micro-Sv-in-any-one-hour is equivalent to 6 micro Sv/week, and 300 micro Sv/year, using standard working hours data - this being a recognised constraint below the 1mSv effective whole body annual dose limit applied to other persons.]

The bullet 'employees untrained in radiation protection are likely to enter that area where the dose rate exceeds 7.5 micro Sv/h (averaged over one minute)' is not very helpful and we would recommend you talk to your RPA if you believe this effects your radiation work. This point, derived from the IRR17 ACoP, somewhat conflicts with other areas of this regulation. In addition, it applies to employees but apparently not members of the public (who could not be trained in radiation protection anyway). Our analysis of micro-Sv-in-any-one-hour is far more sensible and we would argue this point with the regulators (or judge!).

Do not over-designate, or designate for the wrong reasons

The need to control access will also influence the decision of whether an area needs to be designated. There may be some management arguments for designating a controlled area in order to restrict access for reasons other than simply radiation protection – perhaps to enhance security. However, over designation should be avoided unless the area can meet all the requirements – particularly those in IRR17 - Regulation 19 (Additional requirements for controlled areas).

Designation based on annual expected exposure is best avoided

Caution should be given to designating on the basis of expected annual dose to employees alone. For example, if an area is occupied by an employee for 2000 hours a year (40 week, 5 days per week), then a continuous ambient dose rate of only 3 micro Sv/h would be enough to require designation on the basis that the 6 mSv/ year is reached.

Who is responsible for designating the area as controlled (or supervised)?

The employer in control of the area is responsible for the area's designation. This will be obvious for many fixed systems behind company walls (e.g. research laboratories or industrial irradiators). However, in the medical sector, it is common to formally hand over the area between the hospital and contractors (e.g. installation or service engineers). The test here, among other things, is 'who has the finger on the button which can produce a radiation exposure in the area?'. If a service engineer is working on an x-ray unit and requires it to admit radiation as part of diagnostic checks, then the area usually becomes the controlled area of the engineer's employer (with associated risk assessment, local rules, contingency arrangements, restriction of access etc). Once the work is complete the engineer would hand back the controlled area to the hospital. In the medical sector there is a specific procedure for this handover and hand back, this can be obtained from our downloads section 'Medical controlled area handover procedure'. The principles noted here are of course relevant to other employers with controlled areas outside the medical sector.

What do I need to consider when designating an area as controlled or supervised?

(Supervised areas are considered separately below, however the advice in this section applies in the determination of all designated areas, controlled or supervised).

The following matters should be considered:

(a) who is likely to require access to the area (and who should not require access to the area)

(b) the level of supervision required (including entry and exit procedures, as well as the work which takes place in the area)

(c) the nature of the radiation sources in use and the extent of the work in the area (including sealed or unsealed radioactive sources, and radiation generators)

(d) the likely external dose rates to which anyone can be exposed (IRR17 Regulation 8 - risk assessment - should have this data)

(e) the likely periods of exposure to external radiation (a good understanding of the task, the nature of the source, and occupancy is vital)

(f) the physical control methods already in place, such as permanent shielding and ventilated enclosures (including physical and procedural safety interlocks etc)

(g) the importance of following a procedure closely in order to avoid receiving significant exposure (compare working with unsealed radioactive materials, and a fully shielded table top cabinet x-ray system)

(h) the likelihood of contamination arising and being spread unless strict procedures are closely followed (IRR17 Regulation 8 - risk assessment should consider this)

(i) the need to wear PPE in that area (requires understanding the nature of the source, and weighing up benefits of PPE against other radiation safety principles)

(j) maximum doses estimated for work in the area (useful, but avoid trying to infer annual exposures from limited measurement or assessment).

Are controlled areas fixed once designated?

In some cases, for example a laboratory holding unsealed radioactive material, the area is likely to remain designated for the lifetime of planned work. However, there are certain cases where controlled areas may not be fixed (and this will normally be specified in local rules).

i) There may be circumstances where a work area such as a ward / treatment area in a Nuclear Medicine department can be de-designated at the end of the working day - post monitoring (to prove absence of radioactive contamination). This would then allow cleaners access without needing to consider radiation protection (otherwise they would be working under a written system of work, in the local rules, to allow them access to the controlled area).

ii) Certain medical facilities (e.g. diagnostic x-ray, linear radiotherapy treatment rooms) may have a way of turning off and 'locking off' a system so that inadvertent / unauthorised generation of radiation is not reasonably foreseeable. If this is the case then its usual that active 'controlled area' signage (e.g. illuminated warning signs) are wired into the generator / linac safety circuit so they cease to be illuminated when no radiation generation is possible. Conversely, they will always be illuminated when radiation generation is possible. Note: the ability to de-designate an area when not generating radiation only applies where the generator is shut down / locked off as described. It does not apply to an area where regular entry and exit is require between each period of radiation generation. The reason for this is that special procedures will be required during the day to ensure no person (unless they are a patient in the case of a medical facility) is left in the area prior to radiation being emitted. Furthermore, for some facilities such as large industrial irradiation plants, monitoring prior to entry post shut down is a special procedure likely to require permanent controlled area designation.

Active signage showing no designation, controlled area, and radiation generator (Do not enter)

Controlled Areas: X-ray enclosures and the Health and Safety Executive (HSE)

X-ray enclosures such as those used for cargo screening (particularly those where entry is possible) are commonly designated as controlled, and for good reason. Special procedures are required to control exposures (e.g. making sure no person is inside the unit prior to generating x-rays, and during the handover and hand back of the area to a service engineer). In respect of the service engineer, they will be using special procedures to restrict exposure, in particular the special checks necessary at the end of the work to ensure that radiation safety critical systems (interlocks, shielding, warning lights etc) are functional.

We have been aware of cases where the HSE have also required that the user of x-ray equipment in the food and beverage industry have their x-ray enclosures designated as controlled. This includes those enclosures where its difficult to gain entry (other than by hand), where detectors at the entry or exit will cause cessation of x-rays should they detect a hand (instead of expected product for screening), and where dose analysis has shown that exposures to the hand will not lead to ‘controlled area’ levels of exposure. Furthermore, conversation with an HSE inspector for radiation also indicated they might expect a fully enclosed x-ray cabinet (i.e. access only via an interlocked door), even where that cabinet is not large enough for person entry, to be designated as ‘controlled’ (but would not expect a controlled area sign).

In the above cases, local rules, an RPS and a risk assessment would always be present (even though the area might not be formally designated), since IRR17 as a whole still applies. The use of local rules and the appointment of a RPS is then simply good health and safety practice. However, it was the view of HSE (in conversation with Ionactive) that special produces were required to gain entry to the food screening unit (e.g. to free a stuck product), and in the case of the fully contained x-ray cabinet, special procedures would be required by a service engineer to ensure the x-ray cabinet was safe following service / maintenance. In these cases, practical radiation safety (and its management via local rules and the RPS) is evident, but clearly there is an expectation that controlled area status is expected. If you already have local rules, RPA and risk assessment (etc) in place, then designating the inside of the x-ray cabinet in the above examples requires minimal additional effort. If in doubt seek advice from your RPA.

Supervised Area

Over the last 20 years or so we have seen very few supervised areas when compared to controlled areas. This may come as a surprise, particularly when you look at average annual exposures across many groups and find them substantially below 1 mSv effective whole body dose. The issue is 'potential' exposure as apposed to expected exposure during routine work. Nevertheless, we think that over designation takes place in many work areas. The formal considerations for designating a supervised, after suitable risk assessment are where:

  • it is necessary to keep conditions under review to determine whether the area should be controlled or supervised; or
  • a person is likely to receive an effective dose greater than 1mSv per year, or an equivalent dose greater than one tenth of any relevant dose limit referred to in Schedule 3 (except in the case of dose to the lens of the eye, where > 5mSv but < 15 mSv would require a supervised area).

The criteria for supervised (and controlled) areas are summarised in the table below.

Controlled and supervised area annual dose thresholds for designation
Controlled and supervised area annual dose thresholds for designation

Typical areas that might be designated as supervised include:

  • Laboratories for research using low activity radioactive material. It is common in the university sector to designate a small area of a larger laboratory as supervised, for the purposes of controlling radiation exposure in that area and ensuring records are maintained and disposals are made down designated sinks.
  • Research 'hot labs' where higher activity radioactive materials are dispensed or processed - it is common to designate the laboratory as supervised and the fume cupboard as controlled.
  • Change areas (where lab coats / gowns / overshoes are worn or taken off) are often supervised. This area might also be used for hand washing and personal monitoring with a hand or foot monitor. The area acts as a 'buffer zone' between non-designated areas outside and the controlled area beyond the changing room.

If you need advice regarding any of the matters in this section, please consider a formal consultation with an Ionactive RPA (see Radiation Protection Adviser services).

IRR17 (18) - Local rules and radiation protection supervisors part 1


The strict legal requirements under IRR17 for local rules are focused on Controlled Areas. However, the regulations also allow for their adoption – where appropriate – in Supervised Areas.

For the purpose of enabling work to be carried out in accordance with IRR17, every radiation employer should make and set down in writing local rules that are appropriate to the radiation risk and the nature of the work. The radiation employer must then take all reasonable steps to see that they are brought to the attention of relevant persons and are observed.

To assist the employer with this duty, the radiation employer needs to appoint one or more suitable Radiation Protection Supervisors (RPSs) and include the names of such individuals in the local rules.

As we have already noted in IRR17 - Regulation 17 (controlled and supervised areas), there are some valid reasons why an employer will designate an area even where expected doses might suggest otherwise. There are equally good reasons - and legislative requirements – for appointing a ‘RPS Type of Individual’ even where the legally defined Radiation Protection Supervisor role is not strictly necessary. Examples include:

  • Appointing an RPS to ensure that general duties under the Management of Health and Safety at Work Regulations 1999 (MHSW99) (e.g. implementing health and safety arrangements) are in place – with respect to radiation safety and therefore IRR17 compliance
  • Appointing a RPS for the purposes of achieving radiation material accountancy and security (e.g. for the Environmental Permitting (England / Wales) Regulations 2016)
  • Appointing a RPS to act as the eyes and ears of the employer – in addition to any statutory role they may have
  • Appointing a RPS to ensure that specific IRR17 regulations are complied with (e.g. risk assessment, training, maintenance and similar).

The last bullet point is particularly important since regardless of the need (or not) for local rules and the RPS, the requirement to comply with all relevant sections of IRR17 remain.

It will be recognised as good practice for all employers who utilize ionising radiation, to appoint one or more RPSs and use local rules to assist in meeting compliance with IRR17 (and the ALARP principle). However, where the RPS and local rules are not strictly required under IRR17 Regulation 18, the employer (with advice from a Radiation Protection Adviser) can make provisions for an RPS and local rules which are proportional to the radiation risk (but may not comply absolutely with the requirements set out below).

Local rules

Before we look at local rules in some detail it is worth considering the following general points:

  • Local rules must be readable. Although their length and complexity is obviously going to be related to the radiation risk, if they are too long and complicated they will not be read at all.
  • Local rules need to be obvious and on display, and those persons who are working in radiation areas need to be prompted to read them. Many employers require that new workers read the rules and then sign a declaration that they have ‘read and understood the local rules and will abide by them’. There are advantages to this, but it does not obligate the need for suitable and sufficient supervision. IRR17 indicates that local rules can be stored on electronic systems – but should be readily available.
  • Local rules should not be treated as a radiation protection manual. We have seen too many local rules that take up a whole A4 binder. Local rules are not designed to explain the merits of one radiation monitor over another – they are there to simply state you need to undertake monitoring (e.g. where, how often and with what). If necessary, the local rules can reference to more detailed document (e.g. code of practice, procedure or similar) which contains all the detailed reference information.
  • Local rules are for the Ionising Radiations Regulations 2017! They should not detail chemical safety, health and welfare issues or other safety information not related to ionising radiation. If they do the message is often diluted and they lose their impact. The exception to this is where radioactive materials are present (as opposed to x-ray generators) – then it is permissible to include accountancy and waste management issues required by the Environmental Legislation. However these should be no more than ‘rules’ – the detail should be included elsewhere otherwise the local rules become too bulky and will not be read.
  • Local rules are not required where no designated areas exist. However, most employers continue to use them to ensure that all areas of IRR17 are complied with and to meet best practice. Ionactive recommends all its clients to have in place local rules for all sources of ionising radiation present in the workplace.

A typical set of local rules should contain the following:

  • Management & Supervision – details of the management and supervision of the work
  • Information, instruction and training – procedures for ensuring staff have received sufficient information, instruction and training
  • Dose investigation level – 15mSv (or lower as specified by the radiation employer) [IRR17 (9)(8)]
  • Contingency arrangements (where a risk assessment under IRR99 (8) has identified a reasonably foreseeable radiation accident).[IRR17(13)(2)]
  • Name of the appointed RPS for the area (contact details etc). [IRR17 (18)(5)]
  • Identification and description of the designated area (and details of designation – supervised or controlled). [IRR17 (19)(1)]
  • Arrangements / working instructions etc aimed at restricting exposures (to include arrangements for allowing non-classified radiation workers to enter the controlled area). [IRR17 (19)(3)]

If local rules are only being used to meet best practice (i.e. there is no designated area) then you may not need to include, for example, the dose investigation level, since you annual dose limit will need to be below 1mSv (and you will probably not be using dosimetry either).

The above ‘mandatory’ items can then be supplemented (if required) by any or all of the following (depending on nature of the work).

(a) testing and maintenance of engineering controls and design features, safety features and warning devices (i.e planned routine tests)

(b) radiation and contamination monitoring

(c) examination and testing of radiation monitoring equipment

(d) personal dosimetry (the distribution and collection, what to do if dosimetry is lost etc)

(e) arrangements for pregnant and breastfeeding staff

(f) details of significant findings of the risk assessment, or where it can be found (including a copy or risk assessment reference is good practice)

(g) a programme for reviewing whether doses are being kept ALARP and local rules remain effective

(h) procedures for initiating investigations etc

(i) procedures for contacting and consulting the appointed RPA ( often left out, as this is not a mandatory inclusion. Ionactive thinks it should be).

Proceed to IRR17 (18) - Local rules and radiation protection supervisors part 2 to consider the role of the RPS.

IRR17 (18) - Local rules and radiation protection supervisors part 2

Please also read part 1 of our guidance on IRR17 (18)

Radiation Protection Supervisor (RPS)

The RPS is not responsible for radiation safety. That responsibility cannot be delegated down from senior management – or indeed the ‘employer’.

The RPS role is to assist in meeting compliance, ensuring radiation exposures are as low as reasonably practicable (ALARP), supervising the work in compliance with local rules and offering local advice and support. Note: The RPS is not an "adviser" in the same way as the Radiation Protection Adviser (RPA) - however, the RPS should be competent and confident to provide local advice regarding the content of the the local rules (for example correct use of radiation monitors).

Whoever appoints the RPS needs to ensure the RPS has delegated authority to act (this is not the same as having delegated responsibility). For this reason it is important that the RPS

  • should be appointed in writing by a senior responsible manager
  • should have an appointment letter which specifies their duties (we advise RPS delegates to not accept an RPS appointment verbally).

The requirement to have an RPS does not replace the employer’s general responsibility under the Management of Health and Safety at Work Regulations 1999 (Regulation 5 and 7 for monitoring and health and safety assistance respectively). This is one reason why the RPS can be appointed regardless of the legal need to do so under IRR17.

Attending a Radiation Protection Supervisor training course does not automatically mean the delegate becomes an RPS - this only happens when formally appointed in writing by their employer.

RPS - are you suitable?

In order for the RPS to be suitable for appointment, they should:

(a) know and understand the requirements of the regulations and local rules relevant to the work with ionising radiation (attend an RPS training course will help)

(b) command sufficient authority from the people undertaking the work (they need to be suitable and in a position to undertake their role with support from management)

(c) understand the necessary precautions to be taken and the extent to which they will restrict exposures (i.e. understand the nature of the sources of ionising radiation in the workplace)

(d) be given sufficient time and resources to carry out their functions (the role will vary between an hour or two a month, and several days a week)

(e) know what to do in an emergency (perhaps the most important requirement, since this is where the RPS will be required to demonstrate their knowledge)

Note (b) - whilst appointing a senior manager or health and safety lead as RPS may have some advantages, it is not always practicable (the RPS needs to be familiar with the work on the 'shop floor'). This is why the wording of the appointment letter needs to make clear that the RPS has delegated authority to act as noted earlier.

Note (e) - an RPS may not always feel their role is given the credit it deserves (often it will be a small part of their day job.) However, when things go wrong their role will quickly raise to the position of 'tell us what we need to do, and we will do it'. So the RPS has to be really clear about their role in implementing contingency arrangements after a radiation accident (e.g. following a radioactive spill of unsealed material in a laboratory).

What does the RPS actually do?

What follows is a list of potential duties and tasks that might be carried out by the Radiation Protection Supervisor. The list is not exhaustive and the reader may think of (or carry out) other duties not listed below.

  • Preparation of local rules
  • Periodic review of local rules
  • Ensure employees are aware of the content of local rules (and comply with them)
  • Undertake routine or bespoke radiation and contamination monitoring around the workplace
  • Make arrangements for the testing of monitoring instruments
  • Perform checks on safety and warning systems (e.g. functional checks of interlocks and emergency stops)
  • Issue and collection of personal dosimetry
  • Meeting regulators and accompanying them on inspections
  • Co-ordination with any relevant contractors on site (who may well be outside workers)
  • Regular liaison with the Radiation Protection Adviser
  • Make arrangements for annual health reviews (for classified persons)
  • Undertake investigations of exposure abnormalities (e.g. unexpected personal dosimetry result)
  • Identify training requirements (for RPS, management, employees undertaking radiation work etc)
  • Training for new users of ionising radiation.
  • Performing risk assessments and determining contingency plans
  • Taking part in emergency exercises (contingency plan rehearsal is new in IRR17)
  • Radioactive material accountancy and radioactive waste management
  • Arranging the disposal of accumulated radioactive waste
  • Assist in the design of new facilities
  • Undertaking the day to day maintenance of any records in support of the above duties (there are many!)

The employer / RPS should consider obtaining advice from a Radiation Protection Adviser (RPA) ensure the RPS role and local rules are sufficient and proportional to the work being carried out.

How do I appoint the RPS?

An appointment made in writing is required, an example RPS appointment letter is shown below.

Example of a Radiation Protection Supervisor (RPS) appointment letter
Example of a Radiation Protection Supervisor (RPS) appointment letter

IRR17 (19) - Additional requirements for designated areas

General access considerations

Designated areas must be adequately described in Local Rules.

In the case of Controlled Areas, physical demarcation is required where it is reasonably practicable, but there are exceptions for dental and veterinary x-ray sets, and mobile medical units. In these cases, it is necessary for an operator to be able to see people approaching and to de-energise the equipment if necessary. This exception can also be extended to certain other portable x-ray devices such as XRF Positive Material Identification (PMI) units.

Suitable signs must be displayed in positions indicating the area to be designated and the nature of the sources and exposure risks. For example, it is often useful to indicate if there is a contamination risk, a radiation risk or both. It should not be possible for any person to gain physical access to a designated area and not know (i.e. they must have passed a barrier / signage or similar). For the higher hazard radiation sources (e.g. entry to an industrial irradiator), access should be restricted so that unauthorised entry is not permitted. If physical and locked access is not reasonably practicable (e.g. radiotherapy treatment room), then the access point must be protected by an interlocked system that will remove the radiation hazard. This could be achieved by an interlocked gate or light curtain which removes the power supply from an electrical generated radiation source, or withdraws a radioactive source into its shielded storage container.

Controlled area signage examples
Controlled areas signage examples

Entry to a controlled area

For a person to enter a controlled area, they must either be a Classified Person, an Outside Worker (classified or non-classified), or a person who enters under written arrangements which are designed to ensure the dose received will not exceed the thresholds that would otherwise require that person to be classified (and a suitable dose assessment should demonstrate that this is the case). The thresholds were outlined in IRR17 - regulation 17, and are shown below.

Threshold values for controlled and supervised areas
Threshold values for controlled and supervised areas

A written arrangements are likely to be acceptable where, for example, the employer has designated a whole room as ‘Controlled’ but the work requiring designation is only carried out in a small part of it. However, when considering all Ionactive clients (ionising radiation users), the significant majority do not have classified persons, despite having controlled areas. Therefore these users operate a scheme of work (written arrangements) as part of their local rules, even where significant sources of ionising radiation are present. The test to determine if a scheme of work is justified (rather then a classified person entry requirement) is as follows:

  • For routine work in the controlled area, will likely annual exposures be less than those shown in the above table?
  • For the above work, will likely annual exposures be less than those shown in the above table for all reasonably foreseeable radiation accidents arising from the work?

If the answer is 'yes' for both of the conditions given above, then a scheme of work is suitable - allowing non classified persons entry. This justification is easier to make where 'special procedures designed to restrict exposure' are used as the basis for the controlled area designation, rather than compliance with dose rate criteria or contamination limits given in IRR17 - Regulation 17. For example, with a radiotherapy linac treatment room, risk assessments show that the above two conditions can be met - occupational exposures to employees working in such areas are generally no greater than background.

Over-designation should be avoided since the administrative burden and access requirements are significantly increased.

IRR17 (20) - Monitoring of Designated Areas

This regulation requires adequate routine monitoring of the levels of radiation and radioactive contamination, other than by the use of personal dosimeters (which is covered later), in order to determine the efficiency of the measures employed to control exposure.

Regardless of the type or extent of the monitoring required, an important part of the RPS role is to ensure such checks are carried out in an efficient and timely manner – and in accordance with local rules. This does not necessarily mean that the RPS should undertaken the monitoring.

Adequate Monitoring

What constitutes adequate monitoring depends on many factors including the nature and extent of the ionising radiations present, the process being undertaken and the output of a suitable and sufficient risk assessment. For example, surface contamination monitoring does not need to be undertaken in an area where only x-ray generators are used.

Furthermore, the detection of direct radiation leakage (not contamination) from such x-rays generators requires different techniques than those which might be employed to measure contamination (e.g. narrow beam vs. contamination spread, small point source detector vs. large area contamination monitor, x-rays vs. alpha particles).

Regardless of the nature of the ionising radiation source, the following needs to be considered:

  • What kinds of measurements should be made (e.g. dose rate, air concentration, surface contamination)
  • Where the measurements should be made
  • How frequently, or on what occasions should they be made
  • Method of measurement (type of instrument, sampling technique)
  • Who should make the measurements (RPS, radiation users, Radiation Protection Adviser)
  • What records should be kept and for how long
  • Reference levels and the actions to be taken should they be exceeded (to be specified in local rules)
  • When monitoring procedures should be reviewed

External radiation vs. Internal radiation hazards

Measuring Dose Rate using an Ion Chamber
Measuring Dose Rate using an Ion Chamber

For areas designated on the basis of external radiation, monitoring should include measurement of dose rates, averaged over a suitable period if necessary.

This is very important, for example, when deciding what exposure potential is derived from an x-ray security scanner. It may well be that the dose rate measured from the opening of such a device exceeds 7.5 micro Sv/h instantaneously at the moment of measurement, but when averaged over the minute may be equivalent to < 1 micro Sv/h.

For areas designated on the basis of internal radiation, monitoring should include, as appropriate, measurements of air concentration and surface contamination. In either case the monitoring regime should be adequate to indicate whether levels are satisfactory for the continuation of the work, and to detect the breakdown of control systems.

Sometimes monitoring is used to prove the negative rather than measure a positive dose rate above background. Therefore even where no controlled area exists (e.g. around the outside of a fully shielded x-ray cabinet), it might be appropriate to use a radiation monitor to demonstrate that the controlled area is still adequately shielded.

Monitoring equipment - suitability and selection

It is important that those carrying out the monitoring have a proper understanding of the capabilities and restrictions of the equipment they are using and know how to interpret the results. This is one particular area where there is a mandatory requirement for the employer working with ionising radiation to consult with the RPA. See IRR17 (14) Radiation Protection Adviser for advice on mandatory consultation of the RPA.

Particular issues to take into account include:

  • The monitoring equipment must be suitable for the type, nature, intensity and energy of the radiation being monitored. Using the wrong type of monitor is akin to being blind or at the very least only seeing in black and white. You will not ‘see’ the whole picture, and in many cases, you will not see anything at all.

  • Monitoring equipment used in any designated area (and this should be extended to whenever a source of ionising radiation needs to be quantified) must have been appropriately tested within the preceding 12 months. Furthermore, a new piece of equipment should be appropriately tested and calibrated by a suitably qualified person. Larger organisations are likely to have such a person internally, whereas for small users it’s often necessary to look for such services externally.

Monitoring records

Records of monitoring should include the instrument used, date, time, location of monitoring, background measurement (if appropriate), the monitoring results and an indication if levels are being approached where remedial action will be necessary. Zero / background results should always be recorded.

An important objective of the monitoring process is to determine if the correct designation is being employed (e.g. Supervised or Controlled).

All monitoring records should be kept for at least 2 years. However, it is recommended that they are kept for as long as is reasonably practicable, and in any case not destroyed until consideration is given to duties under environmental legislation (as this applies to radioactive materials).

Interaction between IRR17 and environmental legislation

In considering the above matters it is important to note that there is significant overlapping between the IRR17 requirements, and those in the permits / registrations / authorisations issued under Environmental Permitting (England / Wales) Regulations 2018 / Environmental Authorisations (Scotland) Regulations 2018 / Radioactive Substances Act 1993 (Amendment) Regulations (Northern Ireland) 2011. Monitoring areas to determine contamination levels, clearance monitoring to allow free release of material to the environment (as non-radioactive), evaluation of ‘exempt’ or ‘out-of-scope’, and measurements to determine aqueous disposal activity down a sink are all examples of where monitoring will have both safety and environmental purpose.

Environmental monitoring
Environmental Monitoring (IRR17 & Environmental Legislation)