Spreader Bar Detection System (SBDS)

1. Introduction

Ports are essential nodes of global trade, but their throughput and operational complexity also make them particularly exposed to nuclear and radiological risks. The International Atomic Energy Agency (IAEA) Incident and Trafficking Database (ITDB) records 4,626 confirmed incidents involving nuclear and other radioactive material out of regulatory control between 1993 and 2025, of which approximately 14 % involved nuclear material [1]. The IAEA further reports that more than half of all such thefts since 1993 occurred during authorized transport, a share that rises to nearly 70 % when considering only the past decade, and that in about 59 % of those transport-related cases the material has never been recovered [2].

Should radioactive material, such as an orphan source or misdeclared Class 7 cargo, enter the maritime container flow undetected, the consequences may be severe: occupational and public exposure, environmental contamination, disruption of critical infrastructure, and significant economic losses across the supply chain. In its most adverse form, diverted material could be used to construct a radiological dispersal device, the so-called “dirty bomb”. Radiation detection technology is therefore widely recognized as an indispensable component of a layered, defense-in-depth nuclear security architecture [3].

2. Problem statement

Conventional radiological screening at ports relies primarily on Radiation Portal Monitors (RPMs) equipped with large polyvinyl toluene (PVT) plastic scintillators. PVT offers high intrinsic gamma efficiency at low cost and is well suited to large-area passive screening; however, its energy resolution is intrinsically poor which limits the ability to identify specific radionuclides [4], [5]. PVT-based RPMs reliably indicate elevated gamma fields, but provide insufficient spectroscopic information to distinguish naturally occurring radioactive material (NORM) from medical or industrial sources or from isotopes of concern such as caesium-137 and cobalt-60. Performance requirements for such portal monitors are specified in standards such as ANSI N42.38 and IEC 62244.

Secondly, RPMs typically measure containers only when they enter or leave the terminal. Transshipment containers and units that remain inside the terminal yard may never traverse a fixed portal. Detection performance can be further degraded by vehicle speed and the standoff distance between detector and container, all of which can create blind spots and increase the probability of missing a genuine threat. Spectroscopic portal monitors and handheld radionuclide identification devices (RIIDs) exist, but the former remain fixed choke points with the same coverage gaps, while the latter introduce additional handling and risk operational delays.

Two functional requirements therefore emerge for the next generation of port-level radiological screening: (i) comprehensive coverage of every container handled, with measurement geometries close enough to preserve sensitivity; and (ii) sufficient spectroscopic information to enable isotope identification at the first detection stage, allowing responders to make proportionate decisions on isolation, verification and recovery.

3. Spreader Bar Detection System (SBDS)

Building on more than two decades of experience in designing radiation detection systems for the scrap, steel, waste and logistics sectors, Radensys has developed the Spreader Bar Detection System (SBDS), which integrates spectroscopic gamma detectors directly into the spreader bar of a container crane. With a single SBDS installation per crane, every container handled is automatically screened during the normal lift-cycle of approximately 20–40 seconds, with the detector positioned in close proximity to the container surface. Screening is thereby embedded into existing terminal workflows without additional handling, dedicated infrastructure, or operational delay.

A central design choice of the SBDS is the use of crystal-based scintillation detectors, which provide the energy resolution required to identify gamma-emitting isotopes [4], [5]. The system can therefore distinguish between NORM signatures such as potassium-40, legitimate medical or industrial sources, and isotopes commonly associated with malicious use such as caesium-137 and cobalt-60.

The SBDS addresses both gaps identified above. It increases effective coverage by screening containers that would otherwise bypass fixed portals and raises the information content of the first detection stage from a generic “gamma alarm” to an identified isotope measurement. The same spectroscopic data also supports clearance procedures, allowing operators to confirm that cargo and operational areas are safe before normal activities resume.

4. Conclusion

The radiological threat landscape at maritime ports is shaped by persistently high volumes of transport-related incidents reported to the IAEA, and by the well-documented spectroscopic limitations of legacy PVT-based portal monitors. A robust defense-in-depth response requires not only more detection points, but smarter ones.

By integrating crystal-based gamma detectors into the spreader bar of a container crane, the Radensys SBDS converts each routine container movement into an isotope screening event, without disrupting terminal operations. The result is broader coverage, more actionable alarms and a more proportionate response, contributing meaningfully to the protection of personnel, critical infrastructure and the global supply chain against nuclear and radiological risks.

References

1. International Atomic Energy Agency, Incident and Trafficking Database (ITDB), 2025 Factsheet, IAEA, Vienna, 2025. Available: https://www.iaea.org/sites/default/files/25/03/itdb-factsheet.pdf
2. International Atomic Energy Agency, “IAEA Database: About 55 % of Nuclear and Other Radioactive Material Thefts Since 1993 Occurred During Transport,” IAEA Press Release, March 2026.
3. International Atomic Energy Agency, Nuclear Security Recommendations on Nuclear and Other Radioactive Material out of Regulatory Control, IAEA Nuclear Security Series No. 15, Vienna, 2011.
4. E. R. Siciliano et al., “Comparison of PVT and NaI(Tl) scintillators for vehicle portal monitor applications,” Nuclear Instruments and Methods in Physics Research A, vol. 550, pp. 647–674, 2005.
5. Y. Altmann et al., “Expectation-propagation for weak radionuclide identification at radiation portal monitors,” Scientific Reports, vol. 10, art. 6811, 2020. doi:10.1038/s41598-020-62947-3.