Executive summary
Non-destructive evaluation (NDE) is one of the quiet pillars of modern industrial manufacturing. Aerospace, automotive, defence, energy, electronics — every supply chain ends in a quality-control step that asks whether what was made matches what was specified, without breaking what was made. The default tool for that question, in India and globally, is X-ray inspection.
X-rays are excellent at imaging dense materials. They are also, by the physics of how they interact with matter, essentially blind to light elements: hydrogen, lithium, carbon, boron, water. That blind spot used to be a niche issue. As Indian industry has moved into lithium-ion battery manufacturing, aerospace composites, additively-manufactured aerospace components, and sealed assemblies with embedded adhesives, the blind spot has become a structural gap.
The complementary probe is neutron imaging. Neutrons interact with atomic nuclei rather than electron clouds, which inverts the contrast: light elements show up clearly, dense metals become transparent. India has world-class research neutron sources at BARC and IGCAR. It has essentially no commercial neutron-imaging capacity to serve industrial users.
1. Why X-rays are blind to light elements
X-ray attenuation scales roughly with the electron density of the target material, which scales with atomic number. Tungsten attenuates X-rays roughly five thousand times more than lithium per unit mass. Inside a sealed lithium-ion cell, an X-ray beam will image the steel casing and the copper current collector clearly, and produce essentially no signal from the lithium electrolyte or the carbon anode — the parts where the interesting failure modes actually live.
Neutron attenuation does not follow atomic number. It follows the nuclear-physics cross-section, which varies non-monotonically across the periodic table and is large for several light elements that X-rays cannot see — particularly hydrogen, lithium, and boron. The two probes are complementary in the literal sense: each sees what the other cannot.
2. Where this matters in Indian industry today
Lithium-ion battery manufacturing
India’s domestic battery industry is in early scale-up. Cell formats are converging on prismatic and pouch designs that pack lithium-rich electrodes into thin, sealed metal cases. The dominant failure modes — lithium plating, electrolyte distribution non-uniformity, dendrite formation, separator integrity — are essentially invisible to X-ray inspection. They are visible to neutron imaging.
Internationally, neutron-imaging beamlines at research facilities (the Paul Scherrer Institute in Switzerland, NIST in the US, FRM-II in Germany) routinely image lithium-ion cells during charge-discharge cycles to study these failure modes. The work has been done. What is missing in the Indian context is commercial-scale neutron imaging for production-quality control, not for research.
Aerospace composites
Carbon-fibre reinforced polymer (CFRP) composites dominate modern aircraft and increasingly modern launch vehicles. The failure modes — delamination, water ingress, voids in the resin matrix, debonded skin-to-stringer interfaces — all involve light elements (carbon, hydrogen, oxygen) inside light-element bulk material. X-ray works for high-Z inserts; neutron works for the bulk.
India’s aerospace sector — ISRO programmes, HAL, the growing aerospace MSME base — uses CFRP at increasing rates. The qualification standards for composite parts assume an inspection regime that includes neutron imaging at the research-and-qualification stage; the production-line inspection currently improvises with ultrasonic and X-ray methods that have known coverage gaps.
Additive manufacturing
Metal additive manufacturing — powder-bed fusion in particular — produces parts whose internal porosity and residual-stress distribution are non-trivial to characterise non-destructively. X-ray computed tomography is the workhorse, but it struggles at high resolution inside dense parts, and is blind to the trapped hydrogen and oxygen that affect cracking behaviour. Neutron tomography fills both gaps. The Indian additive-manufacturing community currently sends specimens abroad for neutron characterisation.
Sealed defence assemblies
Some defence components — energetic-material assemblies, sealed actuators, certain electronic packages — cannot be disassembled for inspection. Neutron radiography images them without breaking the seal. The Indian defence-NDE community has operated on a small scale via research-reactor access at BARC for decades. Production-rate access has been the gap.
3. The infrastructure question
Globally, neutron imaging has historically been done at research reactors. Reactor neutron beamlines deliver high flux and excellent spectral characteristics, but they live inside a regulatory and capital envelope that is not appropriate for a commercial industrial-inspection service. The cost, the licensing, the scheduling around research priorities — all of it makes reactor beam time scarce for non-research users.
The alternative architecture is an accelerator-based neutron source: a compact, contained, dedicated installation that produces a neutron beam suitable for industrial imaging without a fission chain reaction. Accelerator-based neutron-imaging facilities exist commercially in Japan, Germany, and the US. India has none.
The technology to build them is mature. The licensing pathway, under the AERB Category-II framework for accelerator-based sources, is established. The bottleneck has been the absence of a commercial actor with the engineering capacity, the regulatory tolerance, and the patient capital to build one. Under the SHANTI Act 2025, that bottleneck has eased.
4. What this would actually look like at industrial scale
A commercial neutron-imaging service does not need to look exotic. The physical installation is comparable to a mid-sized industrial X-ray facility: a contained accelerator hall, a moderator and beam-shaping stack, a sample-handling area, an imaging detector, a control room, and the regulatory documentation that surrounds all of it.
The service it provides is also comparable to existing X-ray inspection: parts arrive, they are imaged, the images are interpreted, the report is delivered. What changes is the imaging contrast and what becomes visible. The same battery cell that an X-ray scan shows as “casing intact” can show a neutron scan with electrolyte maldistribution that predicts a cycle-life problem before the part ships.
5. Why this matters for the country, not just the firm
India’s industrial ambition — particularly the Make-in-India push in advanced electronics, defence manufacturing, aerospace, and energy storage — runs on a quality-control assumption that is currently met for X-ray-visible failure modes and not currently met for neutron-visible ones. The gap is small at today’s production volumes. It compounds as production scales.
Importing inspection services from abroad — specimens shipped, scanned, returned — works for prototype and qualification work. It does not work for production-rate inspection. A domestic capability for industrial neutron imaging is not a luxury research facility. It is a piece of industrial-quality infrastructure on the same logical level as accredited testing labs for materials testing, metrology, and electromagnetic compatibility.
6. The honest framing
This article does not argue that neutron imaging will become the dominant industrial NDE method in India. X-ray inspection is mature, ubiquitous, cheap, and excellent at what it does. The argument is narrower: that the Indian industrial-NDE toolkit is missing a complementary capability that the country’s manufacturing strategy has structurally created demand for. Filling that gap is engineering, not magic.
ASPL’s Phase 1 accelerator is designed for dual use — the same proton-lithium neutron source that supports BNCT clinical operations during clinical hours is intended to support industrial neutron imaging during off-hours. The configuration is described, briefly, on the applications page. The point is the architecture, not the company: a contained, accelerator-based, dual-use neutron source is a credible way to bring this capability to Indian industry.
Sources & further reading
- Prof. Prabhat Ranjan, “The Probe Indian Industry Has Been Doing Without” (May 2026)
- IAEA, Neutron Imaging: A Non-Destructive Tool for Materials Testing (TECDOC series, public)
- Peer-reviewed lithium-ion battery neutron-imaging literature (Paul Scherrer Institute, NIST, FRM-II groups)
- BARC neutron-radiography programme briefings (DAE)
- AERB — Category-II accelerator-source licensing framework