The art of normal


Craig Duff relates the evolution of the hand-held RIID – from cumbersome baggage to palm-of-the-hand capability

Wearable gamma-neutron spectrometers are increasingly seen as must-have pieces of equipment by radiological specialists in the armed forces, the police services, the Border Force and the emergency services. So radioisotope identification devices (RIIDs) have evolved to become more sensitive and accurate, whilst becoming smaller, more robust and more user-friendly

A radiation incident can be naturally occurring radioactive material, a commercial radioactive substance or a potentially weaponised source. Distinguishing between them requires quick and accurate analysis, since that will drive the response. This is done by spectroscopic analysis using a RIID, a lightweight, portable gamma spectrometer.

Kromek, the County Durham-based firm which specialises in radiation detection devices, has been at the forefront of developing hand-held RIIDs over the past decade. In 2020, Kromek launched its latest variant, the D5 RIID. 

“The D5 RIID is a step-change in portable spectroscopy, which builds on the technology of previous devices, particularly the D3S – which is used in over forty countries around the world.”

Critically one of those countries is the USA, where more than 10,000 units have been delivered. The UK and USA are leading the way in RIID development. In the USA, both the Defense Advanced Research Projects Agency (DARPA) through the SIGMA programme, and the Defense Threat Reduction Agency (DTRA) via a series of training exercises around the country, are supporting Kromek’s technology development. In the UK, government agencies continue to use and further evaluate Kromek wearable detectors.

Low weight but high accuracy
With RIIDs now widely used in a variety of circumstances, the portability of such devices has become increasingly important. So the new D5 RIID is just 660 g – compared with legacy instruments which weigh more than 1.5 kg. Measuring 173 mm x 79 mm x 41 mm, the D5 RIID is light and unobtrusive enough to be both belt and body worn.

It is vital that the size and weight of any portable RIID does not affect its sensitivity and detection capabilities. Kromek has developed a detector for isotope identification across all categories. It uses a 1.5” x 1.5” CLLBC detector crystal, a specific gamma-neutron scintillator which is medium resolution and an area efficiency of 1.62 (compared with a 2” x 2” sodium iodide crystal used in other RIID models).

This ensures that the D5 RIID, despite its small form factor and lightweight design, has a radiometric capability which is 62% better than other available devices. Radiation can be detected from a range of gamma sources from 30 KeV to 3 MeV and also from neutron sources.

Detecting all isotopes
Most importantly, the D5 RIID has unparalleled performance when detecting and identifying isotopes across the energy range at very low dose levels (less than one fifth of normal background levels) – meaning that radioactivity will never be missed.

The dose accuracy of the D5 RIID is ±10% and it can accurately identify isotopes at dose rate levels lower than 0.01 µSv/h (microSieverts per hour). This sensitivity means that detection performance for distant sources is between 40 and 50 times better than the default global standard – ANSI N42.34 – of performance criteria for hand-held instruments for the detection and identification of radionuclides, for gamma dose rate measurement and for an indication of neutron radiation.

Modern RIIDs must be able to identify radiological threats in a variety of scenarios. They need to detect mixed, shielded and heavily masked isotope configurations and confirm radionuclide identification across naturally-occurring radioactive materials (NORM), industrial, medical and special nuclear materials, categorising each isotope accordingly.

As the technology of hand-held RIIDs has matured, the built-in isotope library of the device has become more extensive. The D5 RIID’s isotope library, whose radiological algorithms were proven by Oak Ridge National Laboratory in the USA, meets both ANSI N42.34 and the more demanding US Department of Homeland Security Domestic Nuclear Detection Office (DNDO) technical capability standards.

At the same time, when constantly scanning for threats and maintaining a high level of sensitivity, it is essential to have an exceptionally low false alarm rate. The D5 RIID has just one in 24 hours, ensuring that this RIID constantly delivers the correct information to enable the user to make quick and effective decisions.

A networked solution
The advance in RIID technology and software development means that the newest RIIDs must now interface with or be integrated into existing systems, including smartphones, to enable a ‘reach-back’ capability. High-resolution spectral results obtained in the field can be transmitted immediately to an offsite location such as a laboratory for secondary adjudication, strengthening the accuracy of the data provided.

They can also be integrated with a network of hubs and sensors to give a wide, real-time overview of the radiological threat. Critically, the connectivity and sensitivity of the D5 RIID allows the building of customised national or local systems using the same sensor.

And as missions get longer and require greater autonomy, the endurance of portable RIIDs has had to improve. Some of the latest variants offer enhanced battery life via dual battery systems. These combine an internal rechargeable battery with a set of replaceable AA-sized batteries (a cheap and readily available battery size) – allowing for speedy in-field replacement. Either option can be used in isolation, or the two systems in unison, providing a battery life in excess of 24 hours.

Designed for all environments
Today’s RIIDs need to be usable in the most extreme environments – so require an operational range of -20 deg C to +50 deg C. Because the portability of the devices has improved, the newest RIIDs also need to be ruggedised to withstand harsh and challenging environments. They have to function regardless of humidity, temperature shocks, being dropped or fully submerged in water. The most technologically advanced RIIDs now conform to the American MIL-STD-810G environmental design and test limits for vibration sensitivity and are water resistant equivalent to the international standard IP67.

Developed for high-hazard environments, a hand-held RIID must be usable by someone in full PPE yet also not function erroneously. Extensive research and testing of the latest D5 RIID has resulted in a detector which fits ergonomically in one hand and can be belt- or body-worn.

As radiological and other CBRN threats proliferate, all government departments and agencies, including the Ministries of Defence, Home Office (Interior) and Border Force, will increasingly rely on the widespread use of portable RIIDs to increase the capacity and tempo of scanning capacity.

“The step changes in size and weight reduction and sensitivity increase, coupled with greater operational bandwidth such as reach-back and building systems around the same spectrometer, particularly the D5 – now make radiation detection the art of the normal. Something hugely welcome in the operational environment.” 

The introduction of the latest wearable RIIDs is proof that a small size does not need to compromise detection capability. The increase in potential radiological threats and hazards means that it is more important than ever for CBRN practitioners to have an ultra-portable device. And RIIDs are now standard use in a wide variety of operating scenarios around the world. They provide immediate and accurate information about radiological hazards – capability that is no longer a luxury, but a necessity.


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