MIRU recently welcomed Mr. Sakai, formerly of Tokyo Steel and now with global steel engineering leader Danieli, to our Shinbashi office for an in-depth discussion on Danieli’s groundbreaking scrap processing technology, the Danieli Scrap To Melt (DSTM) system.
Mr. Sakai has followed an impressive career path, graduating from the University of Tokyo before joining Mitsui & Co., later moving to Tokyo Steel. In March this year, he joined Danieli, where he is primarily engaged in international investment projects, traveling extensively around the world. Despite his busy schedule, he visited MIRU’s office in Shinbashi for this exclusive discussion.
From Surface Analysis to Full-Volume Analysis: How Neutron Technology Changes Scrap Sorting
Tanamachi: Mr. Sakai, thank you for joining us today. I reviewed the materials you sent beforehand, and I must say Danieli’s new sorting system, DSTM, is fascinating. At first, I imagined something similar to a conventional shredder operation, but it appears to be completely different. What surprised me most is the use of neutron technology. How exactly does it work?
Sakai: Thank you for having me. DSTM stands for Danieli Scrap To Melt. Danieli has supplied advanced electric arc furnace (EAF) technologies worldwide for decades, and DSTM was developed with the goal of optimizing the entire scrap melting process.
The system combines Danieli’s high-performance heavy-duty shears, which improve scrap density and size consistency, with advanced sorting technologies and quality control tools such as PGNAA (Prompt Gamma Neutron Activation Analysis).
We commercialize the PGNAA technology in partnership with a U.S.-based company. Thermal neutrons emitted from a radioactive isotope source are directed at scrap moving along a conveyor belt. The atomic nuclei inside the metal become excited and subsequently emit gamma rays with energies unique to each element.
Akai: Gamma rays? We often hear about sorting systems using X-rays or infrared technologies, but neutron-based analysis sounds entirely different.
Sakai: Exactly. Conventional XRF (X-ray fluorescence) technology analyzes only the surface layer, typically about 100 microns deep. Even advanced LIBS (Laser-Induced Breakdown Spectroscopy) analyzes only about 5 to 10 microns below the surface.
PGNAA, however, measures the average composition of the entire metal mass non-destructively. It performs true full-volume analysis. Continuous measurements can be conducted every minute, and copper content can be analyzed with an accuracy of approximately ±0.02%.
Tanamachi: So even painted components or scrap bundles containing embedded motors can be accurately analyzed for internal copper content. That sounds like exactly the kind of technology steelmakers around the world have been waiting for.
Controlling Copper Through Batch Sorting Rather Than Individual Picking
Tanamachi: One question comes to mind. If the system can identify composition so accurately, does it use robotic arms to remove individual pieces—almost like Maxwell’s Demon selecting one item at a time?
Sakai: No, it doesn't operate at the individual piece level. The Dynamic Scrap Analysis System continuously measures the average alloy chemistry of the scrap stream in real time.
Based on the measured composition, a high-speed diverter chute automatically directs scrap into different storage bunkers.
Akai: So the destination changes depending on the chemical composition?
Sakai: Exactly. For example, if copper content is the sorting parameter, material with less than 0.20% copper can be directed to Bunker 1, material between 0.20% and 0.30% to Bunker 2, and material exceeding 0.30% to Bunker 3.
Simulation results show that approximately 34% of the material can be sorted into Bunker 1 with an average copper content of 0.097%, 31% into Bunker 2 at 0.244%, and 35% into Bunker 3 at 0.519%.
In this way, each bunker consistently remains within its target chemistry range.
Tanamachi: I see. That means operators can intentionally create stockpiles of premium-grade scrap with average copper content below 0.2%. This approach could fundamentally increase the value of scrap materials.
AI, Deep Learning, and Predictive Scrap Quality Control
Akai: Since the system continuously collects composition data online, can AI be used to learn from it? It seems like operators could accumulate valuable knowledge about how different feed materials affect final copper levels.
Sakai: Absolutely. Similar technologies have been operating in the United States since the early 2000s. More than twenty facilities have adopted the system, generating analytical data for over 26 million tonnes of material.
Before these technologies existed, processors could only learn the chemistry of their scrap after steelmakers melted it. Now, recyclers can understand exactly how specific feedstocks and processing methods influence final scrap chemistry.
As a result, a systematic approach to controlling scrap quality is becoming established within the recycling industry.
Tanamachi: That's powerful. Operators can build databases showing how material from specific yards or suppliers behaves over time. Could Danieli also develop AI systems around this concept?
Sakai: Certainly. Danieli has a dedicated division called Danieli Automation, which develops customized AI software solutions.
The system compares composition data measured before melting with the actual chemical analysis after furnace processing. By continuously refining the correlation between predicted and actual results, operators can steadily improve accuracy.
For steelmakers, receiving scrap with guaranteed chemistry provides confidence and allows them to pay higher prices for reliable material.
Challenges for Japan: The Californium Neutron Source
Tanamachi: Technically, the system sounds extremely attractive. What are the biggest barriers to introducing it in Japan? Is the neutron source itself the main issue?
Sakai: That's correct. Unlike X-rays, which can be generated electrically, neutron systems require radioactive isotopes.
Typically, Californium-252 (Cf-252) is used as the neutron source. While extremely effective, it has a relatively short half-life of approximately 2–3 years, meaning periodic replacement is necessary.
Additionally, many Japanese companies remain cautious about installing radioactive sources within their facilities, particularly because of concerns regarding safety and potential loss or mismanagement of the material.
Akai: That makes sense. In Japan, the perception that radiation equals danger is still quite strong, which could become a significant hurdle for wider adoption.
Competing Scrap Philosophies: Refining Scrap vs. Utilizing Lower-Grade Materials
Tanamachi: I'd like to ask one final question regarding strategy.
Many Japanese EAF producers, including Tokyo Steel, are currently focused on utilizing increasing volumes of lower-grade scrap containing higher levels of copper and impurities. Their approach is to adapt production technologies and develop applications that can accommodate such materials.
Danieli’s DSTM, on the other hand, takes the opposite approach—refining and upgrading lower-grade scrap so that it can once again be used in higher-value applications.
These seem like fundamentally different philosophies toward scrap utilization. Is Danieli planning to emphasize this approach in the Japanese market?
Sakai: The effective utilization of obsolete scrap is one of the industry's most important challenges, and I believe there is room for multiple approaches depending on each company's technological strengths.
For producers targeting premium steel products, strict residual copper limits—often between 0.15% and 0.20%—make scrap quality control essential.
In addition, another highly effective solution is the use of direct reduced iron (DRI) produced by Danieli’s ENERGIRON technology, which can help dilute residual elements and improve steel quality.
Tanamachi: In an era increasingly dominated by recycled raw materials, DSTM appears poised to become a unique and indispensable solution. Thank you very much for sharing these valuable insights today.
I'm sure MIRU readers will find this discussion both informative and highly impactful.
（IRUNIERSE YT translated from【MIRU特別鼎談】ダニエリが切り拓く鉄スクラップの未来：中性子線を用いた革新的選別機「DSTM」の衝撃）
