【Technical Overview】
When neutrons collide with heavy atomic nuclei, they can induce the splitting of the nucleus into two or more lighter nucleus, and releasing a significant amount of energy with additional  neutrons. This process, in turn, initiates surrounding nuclear fission reactions, setting off a chain reaction, as illustrated in Figure 1. Due to the immense energy generated by nuclear fission chain reactions, they serve as the foundation for commercial nuclear power generation. However, if the chain reaction is not adequately controlled, it may lead to accidents and disasters, commonly referred to as 'nuclear criticality' incidents. Therefore, mastering the safety and control methods of nuclear fission chain reactions is crucial for countries implementing nuclear power technology for peaceful use.
 
For over a decade, NARI has committed to the realm of nuclear criticality safety analysis, positioning itself as the sole domestic entity equipped with comprehensive nuclear criticality safety analysis technology. Safety concerns within this domain are of significant public interest, particularly wherever spent nuclear fuel is stored, as nuclear criticality safety issues persist. The nuclear criticality safety analysis technology developed by NARI offers a comprehensive solution, guarantees the criticality safety of spent nuclear fuel in Taiwan.


Figure 1. Fission Chain Reaction

【Project Planning/Technical Applications】
The nuclear criticality safety analysis technology has demonstrated widespread practical applications, as illustrated in Figure 2. Such as in Phase 1 of the spent nuclear fuel disposal project for Chinshan Nuclear Power Plant, NARI independently conducted the criticality safety analysis of the dry storage cask system and gained approval from the regulatory authority. Additionally, in the analysis of spent fuel pools, NARI introduced a burnup credit method. This technological advancement played a key role in retrofitting cask loading pools at Kuosheng Nuclear Power Plant, effectively addressing capacity challenges and averting premature shutdowns.
 
In the high-level waste final disposal project, NARI took the lead in integrating the burnup credit method with complex geometric models for disposal canisters. Through the accumulation of over a decade of technical expertise and experience, its technological proficiency now aligns with international standards. The resulting benefits have the potential to significantly improve the criticality safety margin of disposal canisters, reduce the quantity of required canisters, and minimize the underground disposal site area. This, in the other words, translates into substantial cost savings in construction expenses and constitutes a noteworthy contribution to both safety and economic efficiency.


Figure 2. Application Achievements in Criticality Safety Analysis of Spent Nuclear Fuel

【Future Planning】
The in-house developed nuclear criticality safety analysis technology of NARI meets international standards. In addition to having a track record of domestic applications, NARI has also collaborated with our foreign counterparts and with achievements recognized through reviews by the U.S. Nuclear Regulatory Commission (NRC). It is expected to be applied in various areas such as indoor dry storage at Chinshan Nuclear Power Plant, Kuosheng Nuclear Power Plant and Maanshan Nuclear Power Plant, as well as transportation of spent fuel via land or surface, and high-level waste final disposal. NARI will continue to align with international advanced technologies, contributing to the ongoing storage, transportation, and final disposal of spent nuclear fuel, as well as the decommissioning of nuclear power plants. This commitment ensures the criticality safety of spent nuclear fuel in Taiwan.

【Contact Information】
Name：Po-Feng, Lin
Tel：03-4711400 ext. 6154
E-mail：linbofeng@nari.org.tw