The Cosmic Ray Energetics And Mass instrument on the International Space Station (ISSCREAM)
aims to measure the energy spectra of cosmic ray (CR) nuclei from Z=1 to Z=26
with energies from $10^{12}$ eV to $10^{15}$ eV. The calorimeter (CAL) was designed to measure the energy
of the CR particles. The ISS-CREAM on-orbit data provide evidence that the CAL may have
either suffered from an efficiency problem or its absolute energy scale may be in need of calibration. As a
result, a careful scrutiny of the absolute energy calibration of the CAL is required. We describe an
approach to calibrate the energy scale using the on-orbit data of the boronated scintillator detector,
which is independent of the CAL data and reduces potential bias. We discuss the issues revealed by
the on-orbit data, demonstrate how this can be corrected using the boronated scintillator detector
and present preliminary results.