The wood samples were measured as rectangular and powder
samples. The precision of the measurement of rectangular samples
was confirmed by the following method. Firstly, 137Cs concentrations
from the rectangular samples (CA) and that of the upside
down rectangular samples (CB) were compared (linear approximation:
CB ¼ 1.0012 CA, R2 ¼ 0.9946). Secondly, the average of
137Cs concentrations of the rectangular samples (CAve) and the
powder samples (CP) were compered (linear approximation:
Cp ¼ 0.9862 CAve, R2 ¼ 0.9969). The relationships for both were
shown as a linear equation with slope of unity and strong positive
correlation. Therefore, it was confirmed that the measurement of a
rectangular sample was sufficient to accurately evaluate 137Cs
concentration in the wood in this study