## 2 Materials and Methods
### RADTRAN 6 Code  
RADTRAN is an internationally renowned computer algorithm for assessing the risk and effects (consequences) of transporting radioactive materials in both incident-free (normal) and accident situations. It is a transportation risk analysis code in which the analysis is based on transportation scenarios (accident-free and accident situations), the likelihood (probability) of each transport scenario, and the effects or outcomes (dosage) of each scenario. Risk is the product of probability and consequence in a quantitative  
Figure 3: Route segments between Seoul to Gyeongju. sense, RADTRAN uses a collection of algorithms that multiply the likelihood and effects of a given situation to calculate risk. The output of both RADTRAN's incident free computations and accident risk calculation are expressed in units of dose and collective dose, but when the probability term is included in accident risk calculations, the collective dose is referred to as \"dose risk\". RADTRAN can also be used in conjunction with dispersed inputs and a random sampling code to calculate uncertainty and perform probabilistic risk assessments. Highway, rail, and waterways are among the modes of transportation considered in RADTRAN, whereas tractor-trailers and light-duty vehicles for highway, railars, and barges and other ships for waterway transport are examples of vehicles linked with these modalities. RADTRAN was developed at Sandia National Laboratory and has since been extended and advanced to improve its analytical capability. The following is the chronological development of the RADTRAN computer code versions, where RADTRAN I, RADTRAN II, RADTRAN III, RADTRAN IV, RADTRAN V, and RADTRAN VI were developed in 1977, 1983, 1986, 1992, 2000, and 2009, respectively. RADTRAN VI is the current version with physical and radiological data in its internal library are used together with analyst input data to assess risk and collective exposure dose. The assessment can be route-specific by assigning values such as vehicle speed, population density, accident rate, and traffic volume. To estimate the risk and exposure dose, the code uses various models, including models for the receptor population, exposure pathways, package behavior in accidents, accident probability, and severity. RADTRAN consists of files for default values for some parameters, including standard meteorological weather, which is the average US weather data, isopleth area, average breathing rate, and residential building factors. There is also a file for dose conversion factors, which are based on ICRP 72 and Federal Guidance reports (FRG) 11 and 12 [35, 36, 37]. The ICRP 72 compiles age-dependent committed effective dose coefficients for the members of the public from the intakes of radionuclides by ingestion and inhalation. However, dose estimation using RADTRAN does not consider age-dependent, but rather population or collective dose (Person-Sv or man-Sv). The code also uses the Gaussian dispersion puff model for radionuclide atmospheric dispersion during an accident scenario. Particulate matter concentrations are assumed to change with time in this model [33]. Furthermore, RADTRAN has been used globally to assess the risk and dose for the transportation of artificial radioactive materials with levels ranging from low to intermediate to high, such as spent nuclear fuel, enriched nuclear fuel, and industrial radioisotopes, via land, sea, and air. For example, a collective dose of approximately 5.04 \(\times\) 10\({}^{-8}\) person-mSv was reported during the transport of radioactive materials through the Suez Canal in Egypt using the RADTRAN IV computer code [38]. [PERSON] et al. (1999) also reported insignificant dose and exposure risk for accident analysis of spent fuel transport by rail in India using the RADTRAN IV computer code [39].