Study on Evaluation Models of Management Data for Decommissioning of FUGEN

In the Fugen nuclear power plant (FUGEN), the dismantling of equipments in the turbine building has started in 2008, and the dismantling of equipments around the reactor is scheduled around in 2015. To evaluate the management data on this dismantling of equipments around reactor appropriately, it is very important to study whether the conventional evaluation models have the applicability for FUGEN or not. Thus, the management data on the dismantling of equipments in 3rd/4th feedwater heater room conducted in 2008 was calculated with the conventional evaluation models. The conventional evaluation models were made by data obtained from Japan Power Demonstration Reactor (JPDR) decommissioning program. It was found that there were large differences between the calculated values and the actual data. For finding the cause in the difference between them, the dismantling of equipments in 3rd/4th feedwater heater room was divided into three processes: i) the preparation process, ii) the dismantling process, and iii) the clean-up process. In the both process of preparation and clean-up, the calculated values were smaller than the actual data. These were mostly caused by the plant scale difference between JPDR and FUGEN, because the conventional evaluation models were built by analyzing the actual data on the decommissioning of JPDR which is smaller than FUGEN. The primary expression depending on the area of working space was built as new evaluation models for the preparation and clean-up processes. In the dismantling process, on the other hand, it was found that there were characteristic differences in the dismantling of feedwater heater as follows: 1) the calculated values were significantly larger than the actual data, 2) the actual data for the dismantling of 3rd feedwater heater was larger than that of 4th one, though these equipments were almost same weight. It was found that these were brought by the difference in the descriptions of dismantling of feedwater heaters, and the new evaluation models reflecting the descriptions of dismantling were built for the appropriate evaluation of the management data. The calculated values with the new evaluation models for each process showed the good agreement with the actual data. In this report, study on evaluation models of management data for dismantling of equipments in the feedwater heater room will be described.