Permits to Work · Mandatory · Construction

Permit to Work — Radiography

The Radiography Permit authorises the use of ionising radiation sources for weld inspection or structural testing on construction sites. It mandates controlled and supervised area boundaries, exclusion zone barriers, radiation warning signage, and dose monitoring for classified workers. Work must be carried out by an approved Radiation Protection Supervisor in accordance with the site radiation risk assessment.

Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. IRR 2017 remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.

Legal basis	Ionising Radiations Regulations 2017 (IRR 2017) + Radiation (Emergency Preparedness and Public Information) Regulations 2019 (REPPIR)
RPA	Radiation Protection Adviser — a qualified expert appointed under IRR 2017 Regulation 14 to advise the employer on compliance with the regulations. Must be consulted before any radiographic work.
RPS	Radiation Protection Supervisor — appointed under IRR 2017 Regulation 18 to supervise compliance with local rules and ensure controlled area procedures are followed on site.
Controlled area	Any area where the dose rate exceeds 7.5 microsieverts per hour, or where there is a significant risk of spreading radioactive contamination. Must be physically demarcated and access restricted.
NDT radiography sources	Iridium-192 (Ir-192), Selenium-75 (Se-75), Cobalt-60 (Co-60) — high-activity sealed sources used for non-destructive testing of welds, castings, and structural components
Enforcing authority	Health and Safety Executive (HSE) and the Office for Nuclear Regulation (ONR) for certain categories of source

1. Industrial Radiography — High-Activity Sources

Industrial radiography uses high-activity sealed radioactive sources to inspect welds, castings, and structural components for internal defects that cannot be detected by visual examination or surface methods. The sources used in construction-related NDT (non-destructive testing) — principally Iridium-192, Selenium-75, and Cobalt-60 — emit gamma radiation that penetrates steel sections and produces an image on radiographic film or a digital detector. These sources are inherently dangerous. An unshielded Ir-192 source can deliver a lethal whole-body dose in minutes at close range.

The Ionising Radiations Regulations 2017 (IRR 2017) set out the legal framework for the safe use of ionising radiation in the workplace. They require the employer to appoint a Radiation Protection Adviser (RPA), designate controlled and supervised areas, appoint a Radiation Protection Supervisor (RPS) to oversee compliance on site, establish local rules, provide dosimetry to classified workers, and maintain exposure records. The permit to work for radiography exists to ensure that every exposure is formally planned, that the controlled area is established and enforced, and that no person other than the radiography crew enters the controlled area during the exposure.

Radiography on construction sites is particularly hazardous because the work is carried out in an environment shared with other trades. Unlike a purpose-built radiography enclosure, a construction site has no permanent shielding. The controlled area must be established using physical barriers and warning signs, and every person on site must be excluded from the controlled area for the duration of the exposure. This requires careful coordination with all other contractors working in or near the affected area.

Unauthorised entry into a controlled area causes life-changing injury

A person who enters a controlled area during an active radiographic exposure will receive a radiation dose that may not produce immediate symptoms but can cause deterministic effects (radiation burns, tissue necrosis) and stochastic effects (cancer) depending on the dose received. At close range to an unshielded Ir-192 source, a lethal dose can be accumulated in under 5 minutes. There is no safe threshold for exposure to ionising radiation — the dose must be kept as low as reasonably practicable (ALARP). The permit system, the controlled area barriers, and the RPS presence on site are the critical controls that prevent unauthorised exposure.

2. Radiography PTW — Required Content

The radiography permit to work must contain sufficient detail to identify the source, the controlled area, the supervision arrangements, and the emergency procedures. This is one of the most detailed permits in the permit-to-work system because the consequences of a failure are severe and irreversible. The following table sets out the fields that must be completed on every radiography permit.

Field	Required content
Source details	The radionuclide (Ir-192, Se-75, or Co-60), the activity of the source in gigabecquerels (GBq), the source serial number, and the exposure device model and serial number. The source details must match the transport documentation and the employer's source inventory. The permit must also record the date the source was last leak-tested and confirm the test was satisfactory.
RPA consultation	Confirmation that the Radiation Protection Adviser has been consulted on the radiographic work, the controlled area dimensions, the shielding requirements, and the local rules. The RPA must have provided written advice specific to the site conditions, including the distance calculations for the controlled area boundary based on the source activity, the exposure time, and any available shielding.
RPS on site	The name and contact details of the Radiation Protection Supervisor who will be present on site during the radiographic work. The RPS must be physically present at the controlled area during all source exposures. The RPS is responsible for enforcing the local rules, monitoring the controlled area boundary, and ensuring that the exposure proceeds in accordance with the permit.
Controlled area demarcation	The dimensions and boundaries of the controlled area, the method of demarcation (physical barriers, warning tape, illuminated signs), and the access control arrangements. The controlled area must be large enough to ensure that the dose rate at the boundary does not exceed 7.5 microsieverts per hour during the exposure. The RPA calculates the required distance based on the source activity and available shielding. All entry points to the controlled area must be physically barriered and posted with radiation warning signs.
Local rules	Confirmation that written local rules are in place and have been communicated to all persons involved in the radiographic work. Local rules must identify the controlled and supervised areas, the names of classified persons, the dose investigation levels, the contingency arrangements for source recovery failure, and the procedures for entering and leaving the controlled area.
Dosimetry	Confirmation that all classified persons involved in the exposure have been issued with personal dosimeters (film badge or TLD), that dosimeters are being worn correctly, and that electronic personal dosimeters (EPDs) with audible alarm thresholds are in use. The EPD alarm must be set at a level agreed with the RPA, typically 50 microsieverts for a single exposure sequence.
Survey meters	Confirmation that calibrated radiation survey meters are available at the controlled area and that the radiography crew has been trained in their use. Survey meters must be used to check the source is fully retracted into the shielded container after every exposure, and to confirm the dose rate at the controlled area boundary before barriers are removed. The survey meter calibration must be current (within the last 12 months).
Emergency procedure	The written emergency procedure for a source recovery failure (source stuck in the exposed position), a dropped or damaged source container, or an overexposure incident. The procedure must include immediate actions (evacuation, extending the controlled area), notification contacts (RPA, RPS, HSE, employer), and the location of emergency recovery equipment. The emergency procedure must be physically available at the controlled area during every exposure.
Exposure log	A record of every individual exposure made under the permit, including the exposure number, the time the source was wound out, the exposure duration, and the time the source was retracted. The log must be completed in real time by the radiographer. After every exposure, the survey meter must be used to confirm the source is fully retracted, and this confirmation must be recorded in the log.
Post-work survey	Confirmation that a radiation survey has been carried out after the final exposure to verify that the source is fully shielded, the dose rate at the surface of the container is within the manufacturer specification, and the dose rate at the controlled area boundary has returned to background levels. Only after this survey has been completed and recorded may the controlled area barriers be removed and the area returned to general access.

3. Common Mistakes

Controlled area too small for the source activity

The controlled area boundary must be at a distance where the dose rate does not exceed 7.5 microsieverts per hour during the exposure. This distance depends on the source activity, the exposure direction, and any shielding in place. Using a standard barrier distance without calculating the actual required distance for the specific source and site conditions can result in persons outside the barrier receiving doses above the controlled area threshold. The RPA must calculate the controlled area dimensions for each site setup.

No RPS present during the exposure

The Radiation Protection Supervisor must be physically present at the controlled area during all source exposures. The RPS is not a remote role — they must be on site, at the controlled area boundary, monitoring access and enforcing the local rules. Carrying out radiographic exposures without an RPS present is a breach of IRR 2017 and removes the primary supervision control for preventing unauthorised entry into the controlled area.

Other trades not cleared from the controlled area

Radiography on construction sites requires the complete evacuation of all persons from the controlled area before the source is exposed. This means coordinating with every contractor and trade working in or near the area. Failure to clear the area — because workers were not informed, were in an area that appeared to be outside the barrier but was within the calculated distance, or returned to the area during the exposure — is the most common cause of accidental overexposure on construction sites.

Post-exposure survey not carried out before barriers removed

After the final exposure, the radiographer must carry out a survey with a calibrated radiation survey meter to confirm the source is fully retracted into the shielded container and the dose rate at the controlled area boundary has returned to background levels. Removing the barriers and allowing general access before this survey is complete risks exposing persons to a source that has not been fully retracted. Source retraction failures do occur, and the post-exposure survey is the only way to detect them.

Exposure log not completed in real time

The exposure log must be completed during the radiographic work, not retrospectively. Each exposure must be recorded with the time the source was wound out, the exposure duration, the time the source was retracted, and the survey meter reading confirming full retraction. A log that is filled in after the work is complete from memory is not a reliable record and does not serve its purpose as a real-time control document. In the event of an incident, the exposure log is the primary evidence of what happened and when.

4. Related Documents

Document	Relationship
E1 — Permit to Work: Generic	The generic permit to work template provides the overarching permit framework. The radiography permit is a specialist extension with significantly more detail due to the severity of the hazard. The generic permit principles — authorisation, precautions, time limits, and close-out — all apply, but the radiography permit adds source identification, RPA consultation, RPS presence, controlled area demarcation, dosimetry, and post-exposure survey requirements.
E10 — Permit to Work: Lone Working	Radiographic work must never be carried out by a lone worker. A minimum of two persons (the radiographer and an assistant or the RPS) must be present during every exposure. However, where radiography is carried out during night shifts or on sites with limited occupancy, the lone working permit principles apply to the journey to and from the radiography location and to the periods between exposures when the crew may be isolated from other site personnel.
E9 — Permit to Work: Night Works	Radiography is frequently scheduled during night shifts to minimise disruption to other site activities. Where radiography is carried out at night, the night works permit controls apply in addition to the radiography permit. Lighting at the controlled area boundary must be sufficient for warning signs to be visible and for the RPS to monitor access. Fatigue management is critical for radiography crews working night shifts, given the consequences of procedural errors.
E14 — Permit Handback and Close-Out	The close-out of a radiography permit requires specific additional steps: the post-exposure radiation survey confirming the source is fully shielded, the removal of controlled area barriers, the completion of the exposure log, and confirmation that the area has been returned to general access. The close-out must be signed by the RPS and the permit issuer.

5. Frequently Asked Questions

What is the difference between a controlled area and a supervised area?▾

A controlled area is designated under IRR 2017 Regulation 17 where the dose rate exceeds 7.5 microsieverts per hour or where there is a significant risk of spreading contamination. Access to a controlled area is restricted to classified persons and persons entering under a written system of work. A supervised area is designated where it is necessary to keep conditions under review but the dose rate is below the controlled area threshold. In practice, for site radiography, the controlled area is the primary concern — it is the area around the source during exposure where the dose rate exceeds the threshold and where no one may be present other than the radiography crew.

Can radiography be carried out during normal working hours on a busy site?▾

It can, but the practical difficulties are significant. The entire controlled area must be cleared of all persons during every exposure. On a busy construction site, this may require stopping work across a large area and evacuating multiple trades. For this reason, radiography is typically scheduled during out-of-hours periods — evenings, nights, or weekends — when fewer people are on site. Where radiography must take place during normal hours, the coordination required to clear the controlled area, maintain barriers, and prevent re-entry during exposures is substantial and must be planned in detail.

What happens if the source fails to retract after an exposure?▾

A source retraction failure (commonly called a “stuck source”) is a serious radiological emergency. The source remains in the exposed position, continuing to emit radiation at full intensity. The emergency procedure requires immediate evacuation of all persons to a safe distance, extension of the controlled area, notification of the RPA, the employer, and the HSE. The source must not be approached until a recovery plan has been developed and approved by the RPA. Source recovery is carried out using specialist long-handled tools to maximise the distance between the source and the operator. Under no circumstances should anyone attempt to recover a stuck source by hand.

Do all radiography crew members need to be classified persons?▾

Under IRR 2017 Regulation 22, an employer must designate as a classified person any employee who is likely to receive an effective dose exceeding 6 mSv per year. Industrial radiographers who regularly carry out source exposures will almost certainly exceed this threshold and must be classified. Classification requires a medical examination by an appointed doctor, personal dosimetry, dose records maintained by an approved dosimetry service, and annual dose record reviews. Persons who are not classified must not enter the controlled area during an exposure.

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