[en] The feasibility of using a gas-filled proportional counter as an in-core gamma-ray spectrometer was examined. The detector fill gas was matched to the stainless steel detector wall using general cavity theory considerations. The gas consisted of a mixture of argon, xenon, and methane, with 14C added for calibration purposes, and at a fill pressure of 10 atmospheres. The maximum energy deposition in the cylindrical counter, whose length was 1.25 in. and whose inside diameter was 0.593 in., was 395 keV. Results have shown that pressures of under 5 atmospheres should be used in counters of the type examined here. Two types of preamplifiers were used in the work, a proton-recoil type preamplifier and a typical gamma-ray proportional preamplifier. The proton-recoil type preamplifier proved too sensitive for gamma-ray spectroscopy with better results observed while using the typical gamma-ray proportional preamplifier. Energy calibrations were attempted using 14C, 137Cs and 57Co, but results appear inconclusive