Abstract: The nature and structures of strong complexing compounds formed during the irradiation of 30% TBP-dodecane-1 N HNO3 with a dose of 500 Mrads in a 60Co facility at a dose rate of 1×107 rads/h are studied by means of TLC, IR and gas chromatography-mass spectrometry.The results of TLC indicate that there are four phosphates components in the phase of water extraction: one neutral phosphate (called neutral (1)) and three acidic phosphates (called acid (2),acid (3) and acid (4) respectively). It is found that the value of Hf index of neutral (1) is so small, and the amount of acid (4) is so insignificant, that the determination of various properties only of acid (2) and acid (3) are carried out.IR spectra of acid (2) and acid (3) show vibration characteristic for P=0, P-O-C, P-OH and alkanes, indicating that the products investigated are derivatives of phosphates.Determination of Hf index indicates that the hafnium complexing ability of acid (3) is larger than acid (2). Acid (3) is difficultly scrubbed by 5% Na2CO3 solution and it easily induces emulsion and interface compounds. In spite of the fact that the amount of acid (3) is much less than acid (2), it plays a much worse role in the deterioration of solvent properties than acid (2). Identification by MS of acid (2) shows intensive peaks at mass numbers of 169, 113, which indicates the similarity of the structure acid (2) to dialkylphosphate O(C4H9-O-P-OH)OR, as reported in the literature. MS of acid (3) shows intensive peaks atass numbers 127, 109, which indicates the similarity of the structure of acid (3) to mono-alkylphosphate O(HO- P-OH)OR, which has not been described in the literature at present.GC-chemical ionizing MS and GC-electronic ionizing MS identification are applied in order to obtain molecular formula arid molecular weight. Before analysis the samples are methylated by means of CH2N2.Analysis of acid (2) indicates that there are seven dialkyl long chain acidic phosphates. In acid (3) there are five monoalkyl long chain acidic phosphates.Finally a mechanism for the formation of the strong complexes acid (2) and acid (3) through radicals of HDBP, H2MBP and R is proposed.