Year
2003
Abstract
We have studied the destructive assay for determination of retained curium, plutonium and uranium in leached hulls in order to verify the performance of the High Level Neutron Coincidence Counter (HLNCC). HLNCC cannot determine the amount of plutonium and curium simultaneously in the presence of extremely high fission product activities. HLNCC is therefore used to determine curium based on the neutron measurement. In order to convert curium neutrons into plutonium, the ratio of curium and plutonium is necessary. ORIGEN code is used evaluation of the ratio of curium and plutonium (Cm/Pu) in the present system. Therefore it is important to evaluate Cm/Pu in the hulls with destructive assay to improve the reliability of HLMCC. Dissolving method of the hull and separation technique for curium and plutonium in leached hull were established. We employed sulfate fusion for dissolving the hull. Then remained sulfate was dissolved in nitric acid. Curium and plutonium in the solution were purified and measured by alpha spectrometry. Uranium was analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES), introducing the diluted sample solution directly. In order to compare Cm/Pu in dissolver solution with that in the retained materials in the hull, concentration of curium and plutonium were measured by alpha spectrometry and isotopic dilution mass spectrometry (IDMS), respectively. We calculated Cm/Pu in spent fuel by ORIGEN-79. It was found that the Cm/Pu in retained material was not agreed with that of calculated. The amount of uranium, plutonium and curium in the retained material were very small compared with adhered one. The adhered material could come from the dissolver solution, whose Cm/Pu was agreed well with that of calculated. It can be said that calculated Cm/Pu is applied for determination of plutonium in the hulls by HLMCC.