The study, led by Sachin Shet and Ankan Charan of the Manipal Institute of Technology along with colleagues including S.V. Suryanarayana, S. Ganesan, Sabu Thomas, Srinivas Shenoy Heckadka, Bharath K Bhat and Sudha Kamath, focused on a 10 by 10 by 10 centimeter block of Ordinary Portland Cement grade 43 concrete with a measured density of 2.41 grams per cubic centimeter. The block was placed in the horizontal irradiation channel of a heavily shielded concrete bunker housing a sealed 16 curie americium-beryllium neutron source, an installation that has served the Manipal facility since its calibration in January 2007 and whose decay-corrected activity stood at 15.51 curies, or 573.87 gigabecquerels, as of May 2026.

The americium-beryllium source generates neutrons through the beryllium-9 (alpha, n) carbon-12 reaction, in which alpha particles from the decay of americium-241 strike a beryllium target. The result is a broad, continuous neutron spectrum extending up to roughly 11 megaelectronvolts, with a characteristic emission peak near 4 to 5 megaelectronvolts and a coincident 4.438 megaelectronvolt gamma ray from the first excited state of the carbon-12 nucleus. Critically, because the source sits inside a concrete bunker, neutrons scatter repeatedly from the surrounding walls before reaching the sample, introducing a substantial thermal component that is entirely absent from the bare-source spectrum described by the ISO 8529-1 standard used in the simulations.

To quantify how many neutrons survive the journey through the concrete, the researchers attached thin foils of high-purity gold-197, more than 99.99 percent pure, to the front and rear faces of the block. Gold is a classical neutron flux monitor because its capture cross-section for the gold-197 (n, gamma) gold-198 reaction is large and well characterized, with a thermal value of 98.6 barns and a resonance integral of roughly 1550 barns. The team irradiated the assembly for 19 hours, then counted the characteristic 411 kiloelectronvolt gamma ray emitted by the decaying gold-198 using a high-purity germanium spectrometer calibrated with a europium-152 source, applying careful corrections for true coincidence summing at the extremely close 5 millimeter source-to-detector distance.

The measured spectrum-integrated capture reaction rates were 9.25 times ten to the minus nineteenth per atom per second at the front face and 5.42 times ten to the minus nineteenth at the rear face, each with combined relative uncertainties below 4 percent. The OpenMC Monte Carlo code, driven by the ENDF/B-VII.1 nuclear data library and 80 million neutron histories, predicted 9.884 and 5.710 times ten to the minus nineteenth respectively. The differences, 6.85 percent at the front and 5.39 percent at the rear, correspond to approximately 1.9 and 1.1 combined standard deviations, an agreement the authors attribute in part to localized density and compositional variations in the real block relative to the nominal model.

Even more striking was the agreement in the transmission ratio. The experimental ratio of rear-to-front reaction rates came out at 0.586, while the simulation gave 0.578, a difference of just 1.37 percent. Because systematic uncertainties largely cancel in a ratio, this figure represents the cleanest validation of the computational model. The researchers derived a transmission factor of 0.594, meaning the 10 centimeter block reduces the detectable neutron flux by roughly 41 percent beyond the geometric attenuation already expected from distance and environmental scattering. Simulations also confirmed that fast neutrons are attenuated more efficiently than thermal ones, consistent with hydrogen in the concrete moderating and capturing fast neutrons, and that room-return scattering keeps the flux at 20 centimeters at 51.33 percent of the 10 centimeter value, far above the 25 percent predicted by a simple inverse-square law.

The elemental composition of the concrete, drawn from the PNNL-15870 Rev. 2 compendium and consistent with Bureau of Indian Standards specifications, lists silicon, oxygen, calcium, aluminum, potassium, iron, sodium and trace manganese among its key constituents. Energy-dispersive X-ray spectroscopy confirmed the presence of the principal medium-Z elements on the actual block surface, with an elevated calcium-to-silicon ratio reflecting analysis of cement-paste-rich zones rather than any discrepancy with the bulk reference composition used in transport calculations.

Beyond shielding, the study probed what the neutron field does to the concrete itself. Gamma-ray spectrometry of the irradiated block, begun two hours after the 19-hour exposure, revealed prominent photopeaks from sodium-24 and manganese-56. Sodium-24 arises mainly from thermal capture on the concrete’s sodium content, with a secondary fast-neutron contribution from the aluminum-27 (n, alpha) reaction, while manganese-56 is produced by thermal capture on trace manganese impurities, present at only 100 to 500 parts per million but amplified by manganese-55’s large 13.3 barn capture cross-section, and by the iron-56 (n, p) pathway. A peak at 1460.8 kiloelectronvolts was traced to naturally radioactive potassium-40 rather than activation. These findings underscore that even trace constituents can dominate the induced radioactivity of concrete shielding, a consideration of real consequence for decommissioning and waste management.

The authors are candid about the scope of their work. Measurements were taken at only two positions, sufficient to determine a bulk transmission factor but not to resolve the spatial attenuation profile inside the block, and no secondary gamma-ray dose calculations were performed despite the significant induced activity from sodium-24 and manganese-56. Both limitations, they note, define the agenda for future campaigns at the Manipal facility, where multiple foil positions and dose assessments could extend the benchmark.

For a field racing toward compact reactors, fusion pilot plants and novel shielding composites doped with boron, heavy minerals and fibers, the message of this study is quietly reassuring: ordinary concrete behaves largely as the simulations say it should, and the open-source OpenMC framework paired with ENDF/B-VII.1 data is a trustworthy guide to its performance. As new materials are proposed to replace or augment it, this experimentally validated baseline provides the yardstick against which they will be judged.

Subject of Research: Experimental and Monte Carlo benchmarking of neutron shielding and activation in ordinary concrete using an AmBe neutron source

Article Title: Neutron shielding assessment of ordinary concrete in an AmBe mixed-energy neutron field

Article References: Shet, S., Charan, A., Suryanarayana, S., Ganesan, S., Thomas, S., Heckadka, S. S., Bhat, B. K., & Kamath, S. (2026). Neutron shielding assessment of ordinary concrete in an AmBe mixed-energy neutron field. Results in Physics, 89, Article 108753. https://doi.org/10.1016/j.rinp.2026.108753

Image Credits: AI Generated

DOI: 10.1016/j.rinp.2026.108753

Keywords: neutron shielding, ordinary concrete, americium-beryllium source, OpenMC, Monte Carlo simulation, gold foil activation, neutron transmission, HPGe spectrometry, induced radioactivity, sodium-24, manganese-56, nuclear reactor shielding

As nuclear techniques and technologies advance, the materials used for ionizing radiation detection must also evolve. Silicon carbide stands out as a robust candidate due to its excellent electrical, thermal, and radiation-resistant properties. The study conducted by Pérez and his colleagues focuses on understanding how these P-N junction detectors behave when exposed to various neutron energies. The implications of this research are vast, with potential benefits in enhancing detector efficiency and reliability.

One of the keystones of any scientific investigation is rigorous experimental evaluation. In their experiment, the researchers meticulously characterized the SiC detectors’ performance factors, including their detection efficiency, energy resolution, and operational stability. Through a series of controlled tests at the RA-6 reactor, they exposed the detectors to a spectrum of neutron irradiation conditions, simulating the realistic scenarios they might encounter in the field. This level of detail is crucial, as it provides a comprehensive understanding of how these detectors might perform in practical applications.

The study elaborates on the methodology employed to assess the SiC detectors, detailing how the researchers used a range of neutron energies to stress-test the materials. This comprehensive evaluation not only sheds light on the fundamental behavior of silicon carbide under neutron irradiation but also highlights how different energy levels affect the overall performance metrics of the detectors. Through a combination of empirical data and analysis, the researchers compiled a wealth of information that can be utilized to optimize future SiC detector designs.

Results from the experiment indicate that the silicon carbide P-N detectors maintained a commendable level of performance even when subjected to significant radiation doses. Notably, the detectors demonstrated a remarkable resilience to both thermal and fast neutrons, a finding that positions them as effective tools for a variety of nuclear applications ranging from reactor monitoring to safety assessments. The data gleaned from these tests underscore the potential of SiC technology in revolutionizing how we detect and measure radiation.

Another significant aspect addressed in this research is the operational longevity of the silicon carbide detectors. The repeated exposure to neutron irradiation and the subsequent analysis of performance metrics are crucial for understanding how these devices would behave over time. The research team observed that, while some traditional materials suffer degradation with prolonged irradiation, silicon carbide exhibited a stable response, signifying its long-term viability in high-radiation environments.

One of the most compelling reasons for studying the response of silicon carbide detectors is their dual functionality in radiation detection. The study undertaken by Pérez and his team elucidates the capacity of these detectors to accurately discern between different types of radiation, a critical factor for applications in safety and security. Accurate radiation profiling is imperative in sectors such as medical diagnostics, nuclear power generation, and national security settings, providing a significant advantage for using silicon carbide technologies.

The implications of this research extend beyond immediate applications; they open doors to developing advanced detector technologies capable of operating in extreme conditions. As the global energy landscape shifts and places increased emphasis on nuclear power generation, the urgency to implement reliable and efficient detection systems becomes paramount. The findings from the RA-6 reactor tests propel the field towards more innovative and secure nuclear practices.

In terms of collaborative efforts, the research emphasizes the need for a multi-disciplinary approach involving material scientists, chemists, and nuclear engineers. Such collaborations can lead to enhanced development strategies for new radiation detection systems. By pooling knowledge and resources, the scientific community can accelerate the transition from theoretical benefits of silicon carbide to practical implementations, potentially changing the way radiation is monitored in various sectors.

As the research continues to gain traction, discussions regarding the scalability of silicon carbide detector technology are of utmost importance. Future initiatives may focus on manufacturing techniques that can simplify the production process while maintaining the high performance that has been observed. A shift towards larger-scale deployment of silicon carbide detectors could yield cost savings and accessibility improvements for institutions requiring high-quality radiation detection.

Moreover, the implications of these findings transcend geographical boundaries. As nuclear technology is harnessed for various peaceful purposes worldwide, the need for effective monitoring and detection is a shared global concern. The advancements in silicon carbide detector technology can benefit countries aiming to enhance their nuclear safety protocols and environmental monitoring systems, ultimately contributing to a safer world.

Ultimately, the research conducted by Pérez, Blostein, and Zamorano stands as a testament to the progress in silicon carbide technology for radiation detection. As the findings gain attention in the scientific community, they pave the way for further investigations and innovations. Through continuous research efforts and developments in detector technologies, a future where radiation detection is more reliable, efficient, and accessible is on the horizon.

The exciting nature of this research encapsulates not just the technical aspects of silicon carbide detectors but the broader implications for society as a whole. As technologies evolve, the race to create safer and more effective radiation monitoring systems continues. The insights gained from this study position the silicon carbide P-N detectors as frontrunners in the field of nuclear safety, promising an exciting future in radiation detection technologies.

The journey doesn’t end here; the scientific community must continue to explore, innovate, and apply these findings in diverse arenas. As we strive towards a deeper understanding of nuclear materials, the road ahead is filled with potential and promise for technological advancements that may one day become the gold standard in radiation detection.

Subject of Research: Silicon carbide P-N detectors under thermal and fast neutron irradiation

Article Title: Experimental evaluation of silicon carbide P-N detectors under thermal and fast neutron irradiation at the RA-6 nuclear research reactor.

Article References:

Pérez, M., Blostein, J.J., Zamorano, F. et al. Experimental evaluation of silicon carbide P-N detectors under thermal and fast neutron irradiation at the RA-6 nuclear research reactor.
Sci Rep (2025). https://doi.org/10.1038/s41598-025-32175-8

Image Credits: AI Generated

DOI: 10.1038/s41598-025-32175-8

Keywords: Silicon carbide, P-N detectors, neutron irradiation, nuclear research, radiation detection, experimental evaluation.