The physical and chemical properties of radioactive waste drums, which have been temporarilystored on site, should be characterized before their shipment to a disposal facility in order to provethat the properties meet the acceptance guideline. The investigation of NDT(Nondestructive Test)method was figured out that the contents in drum, the quantitative analysis of free standing waterand void fraction can be examined with X-ray NDT techniques. This paper describes thecharacteristics of X-ray NDT such as its principles, the considerations for selection of X-ray system,etc. And then, the waste drum characteristics such as drum type and dimension, contents in drum,etc. were examined, which are necessary to estimate the optimal X-ray energy for NDT of a drum.The estimation results were that: ®Á the proper X-ray energy is under 3 MeV to test the drums of320 ߧ and less; ®Ë both X-ray systems of 450 keV and/or 3 MeV might be needed consideringthe economical efficiency and the realization. The number of drums that can be tested with 450keV and 3 MeV X-ray system was figured out as 42,327 and 18,105 drums (based on storage of2006. 12), respectively. Four testing scenarios were derived considering equipment procurementmethod, outsourcing or not, etc. The economical and feasibility assessment for the scenarios wasresulted in that an optimal scenario is dependent on the acceptance guide line, the wastegenerator's policy on the waste treatment and the delivery to a disposal facility, etc. For example, itmight be desirable that a waste generator purchases two 450 keV mobile system to examine thedrums containing low density waste, and that outsourcing examination for the high density drums,if all NDT items such as quantitative analysis for 'free standing water' and 'void fraction', andconfirmation of contents in drum have to be characterized. However, one 450 keV mobile system seems to be required to test only the contents in 13,000 drums per year.