Framework proposed for predicting risk in pressurized water nuclear reactors
Framework proposed for predicting risk in pressurized water nuclear reactors lead image
Pressurized water reactors make up the majority of today’s nuclear reactor. However, during their operation, they are prone to eroded products depositing on the surface of the fuel rods, called Chalk River unidentified deposits (CRUD). The resulting enrichment of boric acid can disrupt power distributions, leading to axial offset anomalies and CRUD-induced power shifts (CIPS) that lead to increased safety risks.
Researchers have developed a tool for predicting CIPS in pressurized water reactors. The approach by Zhang et al. dynamically combines analysis of CRUD deposition, boron concentrations and neutron flux to deliver comprehensive and up-to-date predictions of the effects on power dynamics of a reactor.
“The problem itself is a multi-scale physical phenomenon, which encompasses mesoscale boron concentration, meso- to macro-scale CRUD deposition and neutron flux calculation,” said author Dingyi Pan.
With increasing wear and stress on the fuel cladding, collections of boron in the pores of CRUD deposition, called axial offset anomalies, pose risks of depressing flux and releasing radioactive fission products.
The team demonstrated their framework through a 500-day case study, which showed that the most CRUD deposit thickness and boric acid concentration occurs primarily in the upper half of the fuel rod.
When the deposition reaches a maximum boric acid concentration ratio between what is deposited and bulk coolant boric acid concentration greater than 300, the heat flux becomes significantly reduced, precipitating severe axial offset anomalies and CIPS.
The group next aims to use their tool to develop strategies for risk control. They also plan to integrate it into existing frameworks so risk of axial offset anomalies can be further mitigated in the future.
Source: “An integrated framework for the prediction of axial offset anomaly in pressurized power reactors,” by Zhiqiang Zhang, Jinhe Wang, Shuixiong Lei, Jianhua Qin, and Dingyi Pan, International Journal of Fluid Engineering (2025). The article can be accessed at https://doi.org/10.1063/5.0274866 .
