A Correlation of the 60Co and Beta-emitting Radionuclides in the Activated Concrete of KRR-2

Abstract

Dismantling work of the Korean Research Reactor-2 (KRR-2), including its shielding concrete, was completed in 2006. Some parts of the shielding concrete of the KRR-2 were activated by a thermal neutron reaction during operation of the reactor. The levels of gamma and beta-emitting radionuclides in the dismantled concrete are required to be measured and evaluated. The samples were collected from the inner surface to 90 cm horizontal depth on one side of the shielding concrete. The gamma-emitting radionuclides in the activated concrete were analyzed by using HPGe spectrometer. The radioactivities of 3H and 14C were determined by a commercially available tube furnace and liquid scintillation counter and 55Fe and 63Ni by a combined method of an extraction chromatography and a liquid scintillation analysis. A correlation of the measurement results based on the 60Co radioactivity was investigated to estimate the radioactivity level of the activated concrete. The radioactivities of 3H and 55Fe in the dismantled concrete revealed a good correlation with that of 60Co. The correlation formulas are y = 0.77x + 1.68 (r=0.984) and y = 0.96x +1.26 (r=0.995), respectively. In the case of 14C, the correlation is represented as y = 0.60x −1.82 (r=0.998) in the higher range of activity.