This study developed a comprehensive safety assessment model implemented in Microsoft ® Excel for the multi-stage processing

of decommissioning waste. The model enhances existing approaches by allowing fl exible combinations and sequencing

of processing steps while considering material transformations such as phase separation during melting and incineration.

It integrates the International Atomic Energy Agency Safety Reports Series No. 19 for small facilities and a module based

on United States Nuclear Regulatory Commission Regulatory Guide 1.109 for large facilities to support age-specifi c public

dose assessments. Partial verifi cation of the public dose assessment module using NRCDose3 Code version 1.1.4 confi rmed

its accuracy and reliability. The model was tested at the comprehensive radioactive waste processing facility within the Kori

nuclear power plant site and incorporated various waste types and processing steps including melting and incineration.

Assessment accounted for phase changes and nuclide redistribution during processing. External exposure from 60 Co and

137 Cs was dominant for most workers under normal conditions, while 54 Mn exposure was signifi cant for slag workers due

to radionuclide partitioning. In abnormal conditions, inhalation became the major exposure pathway for workers and the

public. This model off ers a robust framework for evaluating radiological impacts in decommissioning waste processing to

ensure enhanced protection for workers and the public.