Understanding radiation and gamma dose rates: What your monitor is really telling you.

Ionising radiation is a powerful and essential tool in today’s industrial world. Whether it’s supporting Oil & Gas operations, powering nuclear energy, or enabling life‑saving diagnostics in medical and life sciences, radiation helps us work smarter and safer.

Among the various forms of ionising radiation, gamma rays (γ) play a particularly important role in industrial applications and radiation safety monitoring.

What are gamma Rays?

Gamma rays (γ) are high‑energy electromagnetic waves that are highly penetrating. Photons are naturally emitted following the decay of alpha (α) or beta (β) particles, releasing energy that allows gamma radiation to power advanced industrial technologies.

By measuring gamma ray attenuation as it passes through materials, industries can:

• Measure material levels and densities inside vessels and pipelines (Nucleonic instrumentation | Tracerco)
• Perform non‑destructive testing (NDT) on welds and pipework
• Analyse geological formations in real time during drilling operations (Mud Monitor– Tracerco Ltd)

Where industrial gamma sources come from

The gamma sources used in industrial systems are artificial, tightly controlled, and highly predictable in performance:

• Cobalt‑60 (Co‑60) produced through neutron activation
• Caesium‑137 (Cs‑137) – harvested from nuclear reactors.

These sources are strictly regulated in the UK by the HSE and environmental agencies. Users must demonstrate safe handling through dose-rate monitoring, ensuring exposure remains ALARP (As Low As Reasonably Practicable) or ALARA (As Low As Reasonably Achievable) worldwide.

Limiting dose rate through effective monitoring

Radiation dose is measured in Sieverts (Sv) in the UK and Rem in the US. To limit radiation exposure, operators rely on three key protective principles:

• Time: Minimize the duration of exposure
• Distance: Increase separation from the source
• Shielding: Block or attenuate gamma rays with suitable absorber.

Dose rates are typically measured in microsieverts per hour (µSv/hr). Once you know the dose rate in an area and how long someone remains there, cumulative exposure can be calculated.

Under IRR17, any area above 7.5 µSv/hr must be designated and signposted as a “Controlled Area”, restricting access, and maintaining safe working conditions. Areas below this threshold are considered safe for routine work.

Gamma radiation is invisible to our five senses, therefore dependable and accurate dose‑rate monitors are essential for radiation safety.

Tracerco Dose‑Rate Monitors: Built for Safety and Performance

Tracerco’s dose‑rate monitors are trusted worldwide for their reliability, durability, and performance in tough industrial environments.

Tracerco T402 / T402HR

Designed for accuracy and ease of use, the T402 series measures both dose rate and peak dose:

• Extended high‑range capability: up to 100 mSv/h (10,000 mrem/h) on the T402HR
• Backlit display for low‑light environments
• Rugged (Ingress Protection) IP65 housing for harsh field conditions
• Adjustable alarms for immediate safety feedback

Ideal for: Industrial, Military and First Responders

Tracerco T202

The T202 is the go‑to intrinsically safe monitor for hazardous areas:

• ATEX & IECEx: Zone 0, 1, 2 rated (no hot work permit is required)
• Lightweight, robust design for daily use
• Clear digital displays with peak‑reading capability.
• IP65 protection against dust and water

Ideal for: Oil & Gas, mining, and industrial applications

Both instruments detect X-rays and gamma rays from 59–1332 keV and offer numeric and bar-graph displays for easy interpretation.

Calibration and compliance

To maintain accuracy and regulatory compliance, dose‑rate monitors must be:

• Calibrated every 12 months (IRR17 Reg 20(3))
• Maintained in good working order
• Never used if uncalibrated or damaged

Routine calibration ensures readings remain reliable, helping operators meet industry and safety regulatory.

To learn more about Tracerco’s Radiation Monitor Calibration Services, visit: Radiation Monitor Calibration Servicing– Tracerco Ltd

Real‑World Applications

Annual nucleonic inspections:

IRR17 requires users of nucleonic gauges to assess their integrity through dose-rate monitoring. The dose rate on the surface of the gauge can be measured using the Tracerco^TM T202 to ensure there are no gamma-ray leaks through the shielding.

Vessel entry:

Vessels fitted with nucleonics may need to be entered during on-site shutdowns and turnarounds. While the nucleonic source must be isolated prior to entry, a dose rate monitor is used to confirm that the source has been isolated and that the vessel is safe to enter.

You can use the ‘PEAK’ function on a Tracerco^TM T202/T402 with extension poles to check the vessel safely without stepping foot inside.

Radiography:

Radiographers must establish “Controlled Area” boundaries, ensuring dose rates at the boundary remain below 7.5 µSv/hr. Dose rate monitoring is also carried out to confirm that radiography sources are returned to their housings upon completion of work.

Transport of radioactive material:

Carriage under Dangerous Goods regulations requires measuring dose rates. Excepted packages may need surface dose measurements, while others require a 1-meter dose check to calculate the Transport Index (TI).