Researchers at the Savannah River National Laboratory (SRNL) examined the stability of Dow Corning Q2-3183A antifoam agent to radiation and aqueous hydroxide solutions. Initial foam control studies with the Hanford tank waste showed that the antifoam agent reduced foaming. The antifoam agent was further tested using simulated Hanford tank waste spiked with an antifoam agent that was heated and irradiated (2.1x104rad/h) at conditions (90 degrees C, 3M NaOH, 8h) expected in the processing of radioactive waste through the Waste Treatment and Immobilization Plant (WTP) at Hanford. After irradiation, the concentration of the major polymer components polydimethylsiloxane (PDMS) and polypropylene glycol (PPG) in the antifoam agent was determined by GPC. No significant loss of the major polymer components was observed after 24h and only 15wt% loss of PDMS was reported after 48h. The presence of degradation products were not observed by gas chromatography (GC), gas chromatography mass spectrometry (GCMS), or high performance liquid chromatography mass spectrometry (HPLC-MS). G values were calculated from the GPC analysis and tabulated. These analyses indicate that any loss of effectiveness of the antifoam agent within 24h of addition to the waste solution is not primarily due to chemical degradation but results from the separation and/or redistribution of the antifoam components from each other by physical means.