Development of Scan Survey Adjust Method for Radioactively Contaminated Sediment in Underwater Conditions

Abstract

Kim, J.-H.; Cho, G.-S.; Lee, J.-J.; Hong, S.-B.; Lee, E.-J.; Lee, B.-C., and Seo, B.-K., 2021. Development of scan survey adjust method for radioactively contaminated sediment in underwater conditions. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 325-329. Coconut Creek (Florida), ISSN 0749-0208. The nuclear power plants located near the coast and river to supply the cooling water. Therefore, unexpected radioactive materials leakage can contaminate the sediment on the coast, river, and lake. The conventional hotspot assessment methods are sampling and scan survey. The sampling method has limitations due to the sample representation, while the scan survey method is an easy way to assess hotspot distribution. However, the scan survey method can overestimate or underestimate the hotspot size depending on the radioactivity concentration, because this method determines the hotspot is exist when the measured count rate or dose rate exceeds the criteria level. In this study, the scan survey adjust method of sediment scan survey has developed. To this, the distribution of spatial effective dose rate was assessed by MCNP(Monte Carlo N-Particle) simulation. Also, the overestimation factor, which is the ratio of the actual hotspot size and estimated hotspot size was calculated. For the scan survey adjust method devised using the overestimation factor, maximum dose rate, and dose rate increase factor. Using this method, the scan survey experiment results were adjusted. As a result, 137Cs survey result that was underestimated were adjusted 11.51∼73.05% overestimate. 60Co survey result that was 2∼3 times overestimated was adjusted 2.02∼45.73% overestimate. Therefore, the scan survey adjusts method can prevent hotspot underestimation and reduced the relative error. This method can improve the accuracy of the hotspot scan survey in sediment. © 2021 Coastal Education Research Foundation Inc.. All rights reserved.