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RISS 인기검색어
- 검색키워드
- 저자 : Jeremy M. Osborn (검색결과 3 건)
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Jeremy M. Osborn,Kevin J. Glennon,Evans D. Kitcher,Jonathan D. Burns,Charles M. Folden III,Sunil S. Chirayath 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.6
The growing nuclear threat has amplified the need for developing diverse and accurate nuclear forensicsanalysis techniques to strengthen nuclear security measures. The work presented here is part of aresearch effort focused on developing a methodology for reactor-type discrimination of weapons-gradeplutonium. To verify the developed methodology, natural UO2 fuel samples were irradiated in a thermalneutron spectrum at the University of Missouri Research Reactor (MURR) and produced approximately20 mg of weapons-grade plutonium test material. Radiation transport simulations of common thermalreactor types that can produce weapons-grade plutonium were performed, and the results are presentedhere. These simulations were needed to verify whether the plutonium produced in the natural UO2 fuelsamples during the experimental irradiation at MURR was a suitable representative to plutonium producedin common thermal reactor types. Also presented are comparisons of fission product and plutoniumconcentrations obtained from computational simulations of the experimental irradiation at MURRto the nondestructive and destructive measurements of the irradiated natural UO2 fuel samples. Gammaspectroscopy measurements of radioactive fission products were mostly within 10%, mass spectroscopymeasurements of the total plutonium mass were within 4%, and mass spectroscopy measurements ofstable fission products were mostly within 5%.
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Jeremy M. Osborn,Kevin J. Glennon,Evans D. Kitcher,Jonathan D. Burns,Charles M. Folden III,Sunil S. Chirayath 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.2
An experimental validation of a nuclear forensics methodology for the source reactor-type discriminationof separated weapons-useable plutonium is presented. The methodology uses measured values of intraelementisotope ratios of plutonium and fission product contaminants. MCNP radiation transport codeswere used for various reactor core modeling and fuel burnup simulations. A reactor-dependent library ofintra-element isotope ratio values as a function of burnup and time since irradiation was created fromthe simulation results. The experimental validation of the methodology was achieved by performing twolow-burnup experimental irradiations, resulting in distinct fuel samples containing sub-milligramquantities of weapons-useable plutonium. The irradiated samples were subjected to gamma and massspectrometry to measure several intra-element isotope ratios. For each reactor in the library, a maximumlikelihood calculation was utilized to compare the measured and simulated intra-element isotope ratiovalues, producing a likelihood value which is proportional to the probability of observing the measuredratio values, given a particular reactor in the library. The measured intra-element isotope ratio values ofboth irradiated samples and its comparison with the simulation predictions using maximum likelihoodanalyses are presented. The analyses validate the nuclear forensics methodology developed
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Evans D. Kitcher,Jeremy M. Osborn,Sunil S. Chirayath 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.5
A recently published nuclear forensics methodology for source discrimination of separated weaponsgradeplutonium utilizes intra-element isotope ratios and a maximum likelihood formulation to identifythe most likely source reactor-type, fuel burnup and time since irradiation of unknown material. Sensitivity studies performed here on the effects of random measurement error and the uncertainty inintra-element isotope ratio values show that different intra-element isotope ratios have disproportionatecontributions to the determination of the reactor parameters. The methodology is robust to individualerrors in measured intra-element isotope ratio values and even more so for uniform systematic errorsdue to competing effects on the predictions from the selected intra-element isotope ratios suite. For aunique sample-model pair, simulation uncertainties of up to 28% are acceptable without impedingsuccessful source-reactor discrimination. However, for a generic sample with multiple plausible sourceswithin the reactor library, uncertainties of 7% or less may be required. The results confirm the critical roleof accurate reactor core physics, fuel burnup simulations and experimental measurements in the proposedmethodology where increased simulation uncertainty is found to significantly affect the capabilityto discriminate between the reactors in the library.
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