PNNL

Abstract

Dismantling the reactor core and surrounding structural components of the Chornobyl Nuclear Power Plant (NPP) is a major technical concern for those planning closure and decontamination and decommissioning (D&D) of the plant. Issues include when and how dismantlement should be accomplished and what the radwaste classification of dismantled systems would be at the time of disassembly. While radiation levels and residual radiological characteristics of the majority of the plant systems are measured directly using standard radiation survey and radiochemical analysis techniques, actual measurements of reactor zone materials are not practical due to high radiation levels and inaccessibility. Thus neutron transport analysis was used to estimate induced radioactivity and radiation levels in the Chornobyl NPP reactor core materials and structures. Analysis results suggest that the optimum period of safe storage is 90 to 100 years for the reactor. For all of the reactor components except the fuel channel pipes (or pressure tubes), this will provide sufficient decay time to allow unlimited worker access during dismantlement, minimize the need for expensive remote dismantlement, and allow for the dismantled reactor components to be classified as low- or medium-level radioactive waste. The fuel channel pipes will remain classified as high-activity waste requiring remote dismantlement for hundreds of years due to the high concentration of induced nickel-63 in the Zircalloy pipes.