Identification of Actinides Inside Nuclear Waste Packages by Measurement of Fission Delayed Gammas
ABSTRACT A characterization of the alpha-activity due to the presence of actinides inside nuclear waste packages is necessary to select the best mode of storage. Non-destructive active methods, based on fission process, allow to quantify the global mass of actinides. However, these measurements give no information on the nature of isotopes in most cases. We are currently developing a method to identify actinides (235U, 238U, 239Pu), based on the detection of delayed gammas emitted by fission products. The delayed gamma spectrum can be regarded as a "fingerprint" of the irradiated sample. Qualitative and quantitative analysis of peaks allow an identification of actinides. The main purpose of this paper is twofold. First, basis of this method of differentiation are described. Then, experimental results obtained in fission and photofission are presented, in particular in the case of mixtures containing several actinides.
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ABSTRACT: This paper deals with the application of non-destructive neutron measurement methods to control and characterize 200l radioactive waste drums filled with a concrete matrix. Due to its composition, and particularly to hydrogen, concrete penalizes the use of such methods to quantify uranium (U) and plutonium (Pu) components, which are mainly responsible of the α-activity of the waste. The determination of the alpha activity is the main objective of neutron measurements, in view to verify acceptance criteria in surface storage. Calibration experiments of the Active Neutron Interrogation (ANI) method lead to Detection Limit Masses (DLM) of about 1mg of 239Pueff in the total counting mode, and of about 10mg of 239Pueff in the coincidence counting mode, in case of a homogeneous Pu source and measurement times between one and two hours. Monte Carlo calculation results show a very satisfactory agreement between experimental values and calculated ones. Results of the application of passive and active neutron methods to control two real drums are presented in the last part of the paper. They show a good agreement between measured data and values declared by the waste producers. The main difficulties that had to be overcome are the low neutron signal in passive and active coincidence counting modes due to concrete, the analysis of the passive neutron signal in presence of 244Cm in the drum, which is a strong spontaneous fission neutron emitter, the variation of the active background with the concrete composition, and the analysis of the active prompt neutron signal due to the simultaneous presence of U and Pu in the drums.Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 09/2011; 269(18):1956-1962. · 1.19 Impact Factor
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ABSTRACT: Characterization of nuclear waste packages is crucial to optimize waste management (temporary storage, transport, final repository). Passive and active non-destructive methods are well-adapted to this problem and their coupling can be extremely useful in order to optimize data analysis. Photon activation analysis (PAA), based on the photofission process and on the detection of delayed particles emitted after this reaction, is a powerful tool for the analysis of bulky concrete waste packages. Methods developed around PAA allow to locate, identify and quantify the mass of actinides (<sup>235</sup>U, <sup>238</sup> U, <sup>239</sup>Pu) present in a given package in order to estimate its alpha activity. In this article, we present experimental and simulated results obtained in PAA during the characterization of a real nuclear waste package in the SAPHIR facility (Active Photon and Irradiation System). For the first time, several non-destructive methods (passive gamma-ray spectrometry, high-energy radiography) are combined with traditional PAA techniques (altitude scan, global photofission, photofission tomography) in order to optimize the characterization process.IEEE Transactions on Nuclear Science 01/2011; · 1.46 Impact Factor