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Studies On Some Techniques In Quality Control Of NDA Working Standards

Posted on:2002-09-29Degree:DoctorType:Dissertation
Country:ChinaCandidate:X Y WangFull Text:PDF
GTID:1102360062480786Subject:Nuclear Fuel Cycle and Materials
Abstract/Summary:PDF Full Text Request
Nondestructive Assay (NDA) techniques have become powerful tools for quantitative determination of special nuclear materials (SNM), and played an important role in nuclear material control and accounting (MC&A), also in inspection of Nuclear Safeguards.In order to meet the requirements of NDA measurement, the Laboratory of Technical Research for Nuclear Safeguards of China Institute of Atomic Energy (CIAE), is being in charge of developing four sets of NDA standards: one set of segmented gamma-ray scanner(SGS) uranium standard, one set of SGS plutonhim standard, one set of plutonium isotopic standard, and one set of Active Well Coincidence Counter(AWCC) standard.In this dissertation some pivotal techniques on quality control in developing of NDA nuclear standards above were emphatically studied.NDA standards are an essential part of successful application of NDA techniques, almost NDA instruments and methods require standards to make efficiency calibration and various response corrections. Compared with the destructive assay (DA), NDA has some obvious advantages: it is easy to make measurement automatically without sampling and changing the physical and chemical state of nuclear material, low cost, less operator exposure of radiation, much faster than chemical analysis and no hazards and wastes generated.Preparing NDA standards is expensive and time-consuming. If a set of standards is prepared incorrectly, it is a waste of both time and money; in addition, SNM waste is generated and it must be disposed of or recovered. Therefore it should be planned carefully. The properties of SNM (nuclide mass, isotopic composition, distribution, matrix, etc.) are significant to NDA instrument response, these physical properties must be well known throughout the preparation procedure.For the purpose to assure the quality and to achieve the expected technical performances we have formulated a detailed NDA standards preparation scheme, and studied certain important quality control techniques in preparation and characterization of NDA standards, those are the foundations in developing NDA standards.[4]Metal uranium standards for AWCC will be applied to determine the uranium content in scrap of uranium-aluminum alloy. The thinner uranium foil is better for neutron measurement, so the standards is designed to be made into thin disc(thickness 1mm and diameter 40mm) and will be combined with matrix properly to simulate the item which to be measured. We use Monte-Carlo method to simulate the processes of neutron interrogating uranium by AWCC with ^Am-Li neutron source for calculating the relationship of neutron coincidence count rate vs. the thickness of uranium foils, the result shows that such standards can satisfy the demands of measurement. The simulation can be divided into three processes sequentially: calculating the induced fission neutron rate of uranium and space distribution by MAm-Li neutron source, computing the total uranium fission neutron count rate and time distributions of 42 3He tubes, and calculating the neutron coincidence counting rate.For SGS phitonium standards and phitonium isotopic standards, in order to weigh the PuO2 exactly, the materiel must be calcined at high temperature (1100癈) to guarantee the water not to be picked up by PuO2 before enclosing container.Since the difficulty of dissolving the calcined PuO2 completely is a factor to affect the exact characterization, so we studied the method of catalyzed electrochemical Pu02dissolution and performed the experiments under the condition of room temperature (30±3?), electrolyte of HNO3, catalytic agent of Ag and constant current. The result ofexperiment is that about 100 mg of Pu02 can be dissolved in about 3 hours.The method of catalyzed electrochemical dissolution has the advantages: dissolving quickly and thoroughly, working at the environmental temperature, no hydrofluoric acid (HF) and low acidity (HNO3), etc. It can be widely applied in dissolution of Pu02 and mixed oxide spent fuel element, the leaching of p...
Keywords/Search Tags:Nondestructive assay standards, Quality control, Monte-Carlo simulating calculation, Catalyzed electrochemical dissolution, Characterization, a panoramic analysis of impurity, spark source mass spectrometry
PDF Full Text Request
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