When is an 'industrial radiography walk-in enclosure' not an industrial radiography enclosure (and therefore does not require an HSE consent)?


The title of our latest blog article might appear cryptic upon first reading - this is deliberately so. This article considers a room which at first glance might appear to be an industrial radiography facility, complete with x-ray tube, active signage, last person out buttons, e-stops and an interlocked shielding door. If it is what it appears to be, then a consent from HSE is required. However, as far as the Ionising Radiations Regulations IRR17 (IRR17) are concerned, what the facility looks like (or what features it contains), does not necessarily determine if a registration or consent is required - it's use determines this (or more precisely, the practice being undertaken).

Note: this article considers radiation generators and not radioactive sources. For a detailed discussion on the use of radioactive sources in industrial radiography, please see the following Ionactive article: Potential occupational, non-occupational and accidental radiation exposures in industrial radiography using radioactive sources.

Fully shielded and safety interlocked x-ray room

Imagine you have a new x-ray facility. Its features are something like this.

  • Room internal space is about 5m by 5m.
  • Access to the room is via a single sliding door which is interlocked to the radiation safety circuit.
  • The room is fully shielded using concrete and / or lead.
  • The x-ray room has an adjoining control room where there is a leaded viewing window between this space and the x-ray room.
  • At the centre of the x-ray room is a 120 kV / 5mA x-ray tube mounted on a gantry with projection available in any direction around the room including the ceiling and floor. The generator for the x-ray unit is located in the corner of the room.
  • Below the x-ray tube is a table where objects to be x-rayed can be placed.
  • The x-ray room contains a LPO (last person out) button in the corner furthest from the door. When pressed an audible buzzer is heard and an amber light flashes in the room, the operator has 20 seconds to check the room (for other persons), exit the room and close the door. Successful closure of the door within the 20 seconds 'confirms' the safety system and all interlocks are then live. Failure to do this within 20 seconds means that the LPO procedure must be repeated.
  • Inside the room is a set of e-stops (one on each wall) - pressing any of these during the LPO procedure, or during an x-ray exposure, will terminate x-rays.
  • Inside the room is a three stage active coloured light system with the following meaning: Green "system on", Amber "x-rays imminent" and Red "x-ray on". These illuminate in sequence when all interlocks have been made and the operator selects 'x-ray on' in the control room. During the "x-rays imminent" stage a loud bell sounds, this audible indicator ceases once x-rays are underway.
  • The three stage active light system is also repeated outside the room by the door and also in the control room.
  • The three stage active light system is fail safe, if a bulb fails the system will not generate x-rays.
  • If the door is opened during the 'x-ray on' procedure then the x-ray generator will instantly stop. Closing the door again will not allow x-ray generation to restart, the LPO (sometimes known as a 'search and lock up') procedure must be repeated.
  • The control room has features to prevent unauthorised access (to the x-ray room / control room) and also unauthorised operation of the x-ray system (e.g. inhibit keys, finger print readers and similar).

For those who work in such facilities most or all of the above features will be very familiar.

Note that the one thing we have not mentioned above is exactly what you are using the facility for. This matters and will influence whether you need an HSE Consent or HSE Registration, as required by IRR17. For those familiar with with industrial radiography you might well expect to conduct such work in this facility - we will look at this first.

Industrial Radiography

We will first consider use of this facility for the specified practice: industrial radiography. In summary we can say the following about this practice.

Industrial radiography is the use of ionising radiation in non destructive testing (NDT).

NDT is a process where an article is "tested", and in the case of industrial radiography, uses ionising radiation (via a radioactive source, x-ray tube or accelerator) to form an image on radiation sensitive film or real time imaging systems, to detect potential or actual defects. NDT can also use other non ionising radiation techniques such as ultrasound or dye penetration. The aims of NDT are therefore:

  • To undertake a 'test' to assess the integrity of a component / item.
  • To ensure that the 'test' does not alter the nature of the item in any way (i.e. is non destructive).

Examples of industrial radiography would therefore include:

  • Determination of the integrity of a weld in a gas pipeline.
  • Determination of the integrity of a pressure vessel (perhaps as part of an insurance assessment).
  • Looking for cracks or defects in a jet engine turbine blade.
  • Looking for a fracture in a bridge metal support following damage caused by an extreme weather event.

Note that 'looking for a broken bone in a human patient' is not included. This is not classed as a test and is classed as diagnostic radiology (which has a special meaning such that certain provisions noted above - e.g. fail safe active lights - do not apply - see para 126 of the IRR17 ACoP for further details of this example).

Consider also that the UK IRR17 regulations define industrial radiography in the following way: 'means the use of ionising radiation for non-destructive testing purposes where an image of the item under test is formed (but excluding any such testing which is carried out in a cabinet which a person cannot enter)' (Reg 2-1). Note that NDT is included in the definition, meaning that the image formed is a product of the process of NDT, not just any process that forms an image using ionising radiation. Further note that the specific word 'test' or 'testing' is specifically used.

If industrial radiography is taking place in the UK, then there is a requirement for the employer to obtain a consent from HSE before this specified practice commences. Ionactive has consent related content online - the following may be of use:

As of October 2023 obtaining a consent is quite a complex and expensive process (see second link for details). This is supposed to reflect the nature / hazard / risk from the radiation source being used. As you will see next, this is as much to do with what you are doing, as to what you are using.

Museum x-ray imaging of a painting

Imagine you work for a museum that curates precious artwork. Money has been spent and you have been given an x-ray imaging room that will be used to x-ray paintings. The aim is to look for hidden canvas and other artifacts below the top (visible) canvas without making cuts, or otherwise damaging the artwork.

The x-ray imaging room you have been given is identical to the room described in the previous section in every detail.

You are NOT testing the item (artwork) for a defect, you are not performing NDT. You are not performing industrial radiography (see definitions in the previous section). You are merely using x-rays to see beneath the top layer, you are investigating the art history which may be contained within. You are researching, experimenting, increasing knowledge and adding value to the art specimen under assessment. You may write a research paper of your findings, or use the x-ray images in teaching of undergraduate art history students. If you are involved in the academic side of the museum you might have a MSc or PhD student lined up to use the x-ray facility, under your direction, to help with their own research and dissertation etc.

We have chosen a painting as an example, but this could easily be a natural history specimens such as an ancient fish or perhaps a dinosaur bone. Or, you could be a science museum, seeking information about the inner workings of an enigma machine without disturbing its delicate inner workings. You are not 'testing' the item (NDT), you are investigating it for research purposes.

This is not NDT, it is not industrial radiography and you do NOT need a consent from HSE. What you need in place is a registration for use of an x-ray generator (or more precisely a radiation generator). Industrial radiography is a specified practice, whereas x-ray imaging in its various forms is a certain practice (i.e. work with x-ray generators).

Hope you are still with us so far? Perhaps you feel some unease, or perhaps even an element of disquiet about this. Perhaps you think comparing the various definitions is just semantics? We have sympathy. What we can state is that the safe operation of the facility noted in this section is identical to the safe operation of the industrial radiography room featured earlier.

[Ionactive post article submission - additional content. Often we sleep on an article submitted - and something else pops up - here is one of them. Suppose, for whatever reason, a consent was desired (or advised) for our museum x-ray room (wrong decision but let's go with it). This means that the work being carried out is industrial radiography (NDT) as noted in the previous section. It does not matter what is being radiographed (e.g. painting or other museum specimen), a decision has been made that it is a specified practice. Therefore, it would be expected that those working in the x-ray room were trained in NDT - this would be a requirement of compliance with the consent (suitable and sufficient training of personnel conducting NDT industrial radiography). Pointing out that you know how to x-ray a painting or other museum specimen will not rub, the expectation now is that you are trained in the radiographic procedures of NDT. So you would need to be in touch with the British Institute of Non-Destructive Testing (BINDT) and seek advice on training in radiographic NDT (specifically RT – Radiographic testing). This would lead to you undertaking training for your PCN (Personnel certification in non-destructive testing). In order to obtain a Level 1 PCN in RT you would need to take a Basic Radiation Safety (BRS) course before being allowed anywhere near a radiography bay (yes, you will be undertaking practical work as part of your Level 1 training and for this you need your BRS first). During your Level 1 training you will learn all about welding processes and weld defects, properties of X- and gamma-rays, film selection, film processing and much more! <-- all in order to carry out NDT (industrial radiography) on your painting or other museum specimen.

So, don't get a consent for your museum x-ray room - you need a registration. NDT is a highly specialised set of techniques, conducted by experienced personnel who have undergone months / years of training under the eye of trained NDT specialists and training institutes.]

Should the x-ray room described have a consent regardless of use?

Note that Ionactive does not make up the rules / the regulations.

Ionactive comment: If we were writing the regulations, then the x-ray facility described in the two previous sections would have a consent. Why? Because both present exactly the same level of risk of exposure (if someone were inside when the x-ray tube was energised). That said, in our above examples we have stated a 120 kV x-ray tube. This is probably on the limit of what you would need for imaging a painting and perhaps most museum specimens. On the contrary, 120 kV is on the low side of industrial radiography, so you are more likely to have a 200-300 kV x-ray system running at up to 10mA. It then follows that the dose rate inside an industrial radiography room, directly from the x-ray tube collimator, will be higher than that from a typical x-ray tube used in the imaging example given above. This can be countered by the fact that industrial radiography objects (usually steel) will provide a degree of local shielding directly in front of the x-ray tube collimator, whereas many museum specimens will provide less local shielding (i.e. likely to be much less dense than steel).

[Ionactive ponder. The speed limit on a motorway is 70 MPH. You might think it should be 60 MPH to increase safety and lower emissions. If the law says it is 70 MPH then that is the speed limit. You may choose to drive slower - but that is your choice, you do not get to change the law.]

With the second x-ray example described (x-raying a painting or museum specimen), you might choose to have a consent anyway. We are sure that HSE would not be too fussed (another application fee). Dare we suggest that some RPA's might also vote for a consent - after all, assistance with the required radiation safety assessment may require additional RPA input (and therefore RPA fees). If you are pondering this please make sure you reread the last paragraph of the previous section (your journey in NDT training awaits ...)

Regardless - as things stand, the above noted x-raying of the painting or museum specimens, as described in our x-ray room, does not require a consent, it requires a registration.

In the past we have discussed such issues with HSE (including those which follow below), and have their written confirmation of our thoughts in emails (these are naturally not for public consumption). However, there is nothing to stop HSE making a ruling (a position statement or equivalent) regarding what they consider needs a consent in 2023 and beyond.

Other uses of x-ray generators that require a registration

The latest (October 2023) HSE guidance for registrations states the following:

Work with radiation generators

A radiation generator is a device capable of generating ionising radiation such as X-rays, neutrons, electrons or other charged particles.

This includes the following work:

  • X-ray devices used by dentists, vets, chiropractors and NHS trusts
  • X-ray devices used by
    • an airport to scan baggage
    • a post room in an office building to scan incoming packages
    • a port or dock to scan incoming or outgoing cargo
  • a handheld X-ray Fluorescence (XRF) device used to determine the metallurgic content of metal
  • using X-rays in a cabinet that cannot be entered to examine products

Ionactive comment: We do not think that the above description goes far enough. Where is the screening / imaging of objects (other than to suggest security screening or cargo)? Also the last line ' using X-rays in a cabinet that cannot be entered to examine products'. What does 'examine products' mean, and how does that fit with the definition of industrial radiography (see earlier)? Does this mean that using x-rays to examine a product in a room, rather than an enclosure that cannot be entered, imply that this is a specified practice (i.e. industrial radiography)? If that were the case (or intention of HSE), then the legal definition of industrial radiography in IRR17 (noted earlier) needs amending, since this definition uses NDT (non destructive testing), and we have already stated that x-raying a painting or museum specimen is not 'testing'. Furthermore, where do you draw the distinction between examining a 'product' in a room, and a piece of cargo in a large x-ray machine (that can be entered on foot through a flappy shielded curtain, rather than through an interlocked shielding door in our x-ray room described earlier)?

Let us now examine some specific examples given above.

X-ray devices used by dentists, vets, chiropractors and NHS trusts

The grouping of this set of uses is interesting.

  • Dental, chiropractors and NHS trust relate to medical exposures - which we might group, by way of example, as diagnostic radiology (this is a term that is used in the IRR17 ACoP, para 126). The term radiology could also be used on its own for procedures that use medical x-rays for positioning (e.g. interventional cardiology).
  • Veterinary use of x-rays for imaging of animals is NOT diagnostic radiology. We know this is so as HSE have been visiting veterinary practices and ensuring that their active x-ray-on lights 'fail safe' (i.e. if the light fails the x-ray will terminate). This is NOT a requirement for diagnostic imaging of humans (again, see IRR17 ACoP, para 126). This makes some sense - if an active light failed in a medical CT scan room and the CT scanner stopped, the patient might receive half a scan providing negligible diagnostic benefit, but still receive an exposure (so no overall benefit to the patient). this would then require an additional scan at a later date and yet more exposure.

Note that either of the above certain practices could have taken place in our x-ray room (described at the start of this article). It is true that in the case of diagnostic radiology things are different, IRR17 says so. However, in the case of veterinary x-ray we know that this is not diagnostic radiology (hence HSE insistence on fail safe active lights etc).

We know that all the uses of x-rays noted above require a registration from HSE (and not a consent). Putting diagnostic radiology aside (it is a special case involving the x-raying of humans), what is the exposure risk difference between x-raying a live animal in our above described x-ray facility, and x-raying a painting or museum specimen? Nothing at all. This supports the case, in addition to our assessment thus far, that x-raying of passive specimens in our x-ray room should only require a registration and not a consent.

Consider x-ray imaging a horse. This could not be reasonably performed in our described x-ray room. The horse would be lightly sedated, would remain standing and its head would be held by a veterinary nurse wearing a leaded apron. Further staff would be used to place an imaging panel in the desired location (e.g. femur). Another employee would operate a portable x-ray system - ensuring that at the moment of exposure there is no person in the beam. This procedure needs a precise set of local rules, and apart from the PPE (leaded apron), relies on doing the right thing - human factors. Compare and contrast the x-raying of a horse as described, with the x-ray imaging of a painting / museum specimen in a room with interlocks, e-stops and similar? Recall that the horse x-ray procedure only requires a registration and not a consent. Which of the two do you think could present an overall higher radiation exposure risk - the horse x-ray, or the painting / museum specimen x-ray in our purpose made x-ray room?

Ionactive comment: We reemphasise here that we are looking at what the regulations require. We have already stated earlier that there is some merit in our x-ray facility, described in the first section of this article, having a consent regardless of use. However, this is not how IRR17 works - with IRR17, use matters, rather than just the nature of the room / facility / device emitting ionising radiation.

X-ray devices used by airport baggage screening/ post rooms / port or docks screening cargo

This is a huge area of ionising radiation use. We will put aside the smaller x-ray units (such as those screening carry on baggage at an airport or units used in postal rooms), since these are generally too small to be entered (deliberately or by accident). These units will require a registration from HSE.

We will concentrate on the much larger machines and installations - these will include:

  • Cargo screening systems at cargo / freight forwarding companies - typically 160 - 300 kV x-ray systems.
  • Screening systems at ports and docks (some of these will use accelerators which is outside the scope of this article and would require a consent). Most will use kV x-ray generators, and hence require a registration.

Generally the type of equipment featured above will have the following attributes:

  • Large enough to take whole pallets / containers (normally loaded by forklift trucks).
  • Large enough to be entered by a person (not desirable or permitted when x-ray generation is underway, but reasonably foreseeable).
  • Many of the larger cabinet x-ray systems have the interior space of a small room (nearing the area space of our x-ray room described earlier).
  • The infeed and outfeed of the systems are generally protected by leaded curtains - not interlocked doors.
  • Systems will contain x-ray "on" warning lights and feature e-stops etc.

The systems described above will require an HSE registration and not a consent.

Compare the above features to our x-ray room for imaging the painting and museum specimens. Our room contains LPO buttons, search and lock up, active signage which fails safe, and an interlocked door which if opened will terminate x-rays. In theory, you could just walk into a cargo screening unit, or ride on the conveyor and receive an exposure. Typical in-beam dose rates of such systems will be several mSv/h (and many will contain two or three x-ray generators and hence higher compounded dose rates). The latest CT security screening machines will have internal dose rates in the 100's of mSv/h.

Shielding from scattered x-rays relies on leaded curtains which need to be inspected - parts of them can literally drop off due to wear and tear. Reliance is also placed on human factors; it has been known for shielding curtains to be folded back over the stop of the unit to allow 'light' objects to be screened - completely prohibited in the local rules.

Whether such bad practice is reasonably foreseeable is for employer / RPA judgement, but at least with our x-ray room (with a single lower energy x-ray generator) you are protected by an interlocked door.

If someone made a case that the above systems did require a consent (they do not), it would not make sense to insist the lower exposure risk x-ray room (for screening our painting / museum specimen) would also need a consent (notwithstanding the fact that we are not conducting NDT in the room). If you like numbers and calculations you might argue that the dose rate in the x-ray room is higher than the dose rate in the cargo screening systems. But remember, the x-ray room door is protected - you cannot just walk in and receive an exposure.

Handheld X-ray Fluorescence (XRF) device used to determine the metallurgic content of metal

Ionactive comment: Much is made of the headline dose rates of these handheld devices that operate at up to 50kV. They can produce a dose rate at the exit point of 500 mSv/h or more. The actual beam width is tiny (mm2) and so it is impossible to receive a whole body dose at magnitudes implied by the headline dose rate. The same can be said for extremity dose, but the reasoning is less robust. So it might be possible to deliver an extremity dose to a finger which might, in the worst case scenario, approach a dose limit (although in Ionactive experience this would be extremely unlikely and would require multiple unintended exposures to the same finger).

Notwithstanding the above qualifier, these are x-rays 'guns'. All modern devices have proximity sensors , back scatter detectors and similar, meaning you cannot point and shoot into free space. Nevertheless, they are an open x-ray generator which is not used in a shielded room with interlocked doors and active signage. These devices require an HSE registration and not a consent.

Compare and contrast this with a museum curator setting up a painting or natural history specimen in a dedicated purpose built room (our x-ray room), using the LPO to warn everyone to leave the room, confirming this by shutting the interlocked door. Whilst the exposure potential in the room is greater, the protective features lower the risk to negligible levels as described previously. At the very least, if the XRF handheld device does not require a consent (only a registration), then our own x-ray room with all its protective feature, and not undertaking NDT, will only require a registration.

We have already noted "using X-rays in a cabinet that cannot be entered to examine products" - this is outside the scope of this article since we are discussing x-ray work where access into the area is reasonably foreseeable (i.e. an x-ray room or large x-ray cargo screening unit). It should be noted that there is an expectation, driven by the ALARP principle, that such portable handheld XRF devices should, where reasonably practicable, be attached to a purpose made desktop shielding enclosure (these have interlocked lids). These are desirable where the item to be analysed can be physically placed into the enclosure. The use of the portable XRF in handheld mode should be reserved for situations where you have to walk the x-ray device to the item requiring analysis (e.g. the side of a large boiler component).

Other portable x-ray devices (not XRF or veterinary imaging systems)

We noted earlier that the list of x-ray uses (for a registration) could be expanded. Here is an example of where the 'use' can determine whether a registration or consent is required. In this example the actual radiation exposure risks appear to have little influence on the decision making process.

Imagine you have a portable battery operated x-ray unit (about the size of a suitcase). Some of the features might be as follows:

  • The device can operate at up to 90kV and 1 mA.
  • The device is used in pulse mode (i.e. several pulses a second rather than a continuous x-ray beam).
  • Dose per pulse at 1m might be 10 micro Sv (unshielded, directly inline with the collimator).
  • The device has a control box with a 3m lead, connected to the back of the unit. The user must stand 3m behind the unit when x-rays are to be generated.
  • The device contains a prewarn amber lamp mounted on top. When x-rays are switched on a buzzer will sound and the amber lamp will be illuminated for about 5 seconds, the buzzer then ceases and a red flashing lamp denotes that x-rays are being generated (you will usually hear an audible click with each pulse).

If the above setup seems unusual then recall that portable x-ray systems are used in hospitals everyday (i.e. move the x-ray system to the patient). These hospital systems require a registration but since they are diagnostic radiology we will say no more (since we know this is a special case as mentioned earlier in this article).

Consider how this portable x-ray system might be used, and how this will influence the requirement for a registration or consent.

  • The device is used by GCHQ (or equivalent) to screen an embassy partition wall for listening devices (bugs). This will require a robust set of local rules, the area the other side of the wall will need to have access restricted. There is no reliance on PPE, interlocked doors and similar, much of the radiation safety relies on human factors (doing the right thing). This x-ray screening requires a registration (it is not NDT).
  • The device is used by an industrial radiographer to undertake NDT of thin bore pipework on a new boiler house installation. In practical terms the use of the device, and the protective procedures followed, is no different to the embassy screening example. It could be argued that the boiler house is a better controlled environment, with a permit-to-work (PTW) system and daily work briefings and similar, as compared to the embassy where employees the other side of the wall to be screened are told to pop off for 30 minutes and have a coffee. Nevertheless, this work requires a consent from HSE (since it is industrial radiography, performing NDT).

The above examples do not use our robust x-ray room as described earlier in this article. The use of the portable x-ray unit in the above examples is procedurally identical. They are both performed in open space (a work area), but require a registration / consent based on their use and not on the radiation risk they present. Considering radiation exposure risk alone, some might argue that there is a stronger case for a consent applying to the embassy screening work, when compared to the boiler house NDT. But overall, this example does show that how you use an x-ray device influences how you choose a registration or a consent for the work being undertaken.

Ionactive comment: Let us finish this section with an extreme scenario - but not an impossible situation! Suppose our museum x-ray room operator is paranoid that there is a listening device behind the wooden panelling which covers the radiation shielding walls internally. So the x-ray facility is locked off and the door opened wide. A security technician is invited in by the museum management and asked to x-ray image the wooden panelling around the room (using the pulsed x-ray source noted above). The company conducting this work in your x-ray room only needs a registration (it is not NDT), despite the fact that they are not using any of the engineered protective features that you would rely on if you were x-ray imaging your painting or other specimen. Think about that.

Final thoughts

Do not over designate for the sake of it (i.e. registration vs consent) - that alone does not make the x-ray facility safer (one way or the other).

The x-ray room we have described in this article is equally safe for the NDT examination of pipe welds, as it is for the x-ray imaging of the painting or other museum specimens. The safety features are exactly the same.

The NDT use of the room requires a consent from HSE.

The x-ray imaging use of the room (exclusively for the painting and other museum specimens) requires a registration and not a consent.

If our analysis in this article were determined by HSE to be wrong, then there is guidance to be rewritten, and potentially some changes to IRR17 to be made. And for what? Surely tangible radiation safety is imperative, not interpretation of wording? As noted earlier, and not for public consumption, we have email correspondence which aligns with our thinking, particularly with regard to the last example given (embassy wall screening vs. NDT of pipework, both using the same equipment and practical procedures).

If you are interested in this subject you might also like to read this later article (December 2023) - "Potential occupational, non-occupational and accidental radiation exposures in industrial radiography using radioactive sources".

Mark Ramsay

Radiation Protection Adviser

Chartered Radiation Protection Professional

October 2023

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