scholarly journals AN ASSESSMENT OF THE SPATIAL VARIATION OF ISOTOPIC RATIOS IN A CANDU REACTOR FOR NUCLEAR TREATY MONITORING

2021 ◽  
Vol 247 ◽  
pp. 04025
Author(s):  
Aaron W. Burkhardt ◽  
James E. Bevins ◽  
Stephen H. Baxter
Keyword(s):  
Spatial Variation ◽  
Isotopic Analysis ◽  
Isotopic Ratios ◽  
Spent Fuel ◽  
Discrete Energy ◽  
Accurate Representation ◽  
The Core ◽  
Fuel Bundle ◽  
Treaty Monitoring ◽  
Initial Results

A 3-D Quarter-Core CANDU-6 is modeled using Serpent 2 for nuclear treaty monitoring. The spatial variation of flux spectra and isotopic concentrations is analyzed to determine the potential isotopic distribution of key radionuclides from standard reactor operations relevant to non-proliferation. The initial results of the model show a 46% difference in overall flux magnitude throughout the core as well as a 2-30% difference in discrete energy flux. The coupled production rate (magnitude) and spectral differences can contribute to significant spatial variations in isotope ratios throughout the core. Initial results indicate 239Pu/240Pu ratios vary by as much as 51% across a single CANDU-6 fuel bundle at final burnup. The model is currently being used to develop an accurate representation of spent fuel to perform spatial isotopic analysis across the entire CANDU-6 core.

TRU Recycling Options for Environmentally Friendly and Proliferation-Resistant Nuclear Fuel Cycle of FBR

2010 ◽  
Author(s):  
Sidik Permana ◽  
Mitsutoshi Suzuki
Keyword(s):  
High Performance ◽  
Fuel Cycle ◽  
Operation Time ◽  
Nuclear Nonproliferation ◽  
High Level Waste ◽  
Minor Actinide ◽  
Spent Fuel ◽  
Closed Fuel Cycle ◽  
The Core ◽  
High Level

The embodied challenges for introducing closed fuel cycle are utilizing advanced fuel reprocessing and fabrication facilities as well as nuclear nonproliferation aspect. Optimization target of advanced reactor design should be maintained properly to obtain high performance of safety, fuel breeding and reducing some long-lived and high level radioactivity of spent fuel by closed fuel cycle options. In this paper, the contribution of loading trans-uranium to the core performance, fuel production, and reduction of minor actinide in high level waste (HLW) have been investigated during reactor operation of large fast breeder reactor (FBR). Excess reactivity can be reduced by loading some minor actinide in the core which affect to the increase of fuel breeding capability, however, some small reduction values of breeding capability are obtained when minor actinides are loaded in the blanket regions. As a total composition, MA compositions are reduced by increasing operation time. Relatively smaller reduction value was obtained at end of operation by blanket regions (9%) than core regions (15%). In addition, adopting closed cycle of MA obtains better intrinsic aspect of nuclear nonproliferation based on the increase of even mass plutonium in the isotopic plutonium composition.

scholarly journals Advanced Contemplation of the Impure: Reflections on a Capstone Event in the Meditation Sutra

Religions ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 386
Author(s):  
Michel Mohr
Keyword(s):  
Chinese Text ◽  
Cultural Factors ◽  
Fifth Century ◽  
Direct Perception ◽  
Pure Land ◽  
Specific Nature ◽  
True Nature ◽  
The Core ◽  
Mental Construct ◽  
Initial Results

The present article explores the form of meditation called contemplation of the impure (Skt aśubha-bhāvanā; Ch. bújìng guān 不淨觀) and its meticulous description in a Chinese text produced in the early fifth century CE. It illustrates the problematic nature of the pure-impure polarity and suggests that, ultimately, “purity” refers to two different things. As a generic category, it can be understood as a mental construct resulting from the mind’s discursive functioning, which tends to be further complicated by cultural factors. The other avenue for interpreting “purity” is provided in this meditation manual, which describes how meditation on impurity leads to the direct perception of purity, and to the vision of a “pure land.” This stage is identified as a “sign” marking the completion of this contemplative practice. Examining the specific nature of this capstone event and some of its implications lies at the core of the research whose initial results are presented here. Although this particular Buddhist contemplation of the impure begins with mental images of decaying corpses, it culminates with the manifestation of a vision filling the practitioner with a sense of light and purity. This high point indicates when the practice has been successful, an event that coincides for practitioners with a time when they catch a glimpse of their true nature. The last section of this article further discusses the extent to which positing an intrinsically pure nature—one of the major innovations introduced by Buddhism in fifth-century China—could inform ethical views.

scholarly journals RADIONUCLIDE CHARACTERISTICS OF RDE SPENT FUELS

2018 ◽  
Vol 20 (2) ◽  
pp. 69 ◽  
Author(s):  
Ihda Husnayani ◽  
Pande Made Udiyani
Keyword(s):  
Thermal Power ◽  
Neutron Production ◽  
Cooling Time ◽  
Spent Fuel ◽  
Release Rates ◽  
Radiation Dose Rate ◽  
The Core ◽  
Spent Fuel Storage ◽  
Fuel Storage

Reaktor Daya Eksperimental (RDE) is a 10 MWth pebble-bed High Temperature Gas-cooled Reactor that is planned to be constructed by National Nuclear Energy Agency of Indonesia (BATAN) in Puspiptek complex, Tangerang Selatan. RDE utilizes low enriched UO2 fuel coated by TRISO layers and loaded into the core by means of multipass loading scheme. Determination of radionuclide characteristics of RDE spent fuel; such as activity, thermal power, neutron and photon release rates; are very important because those characteristics are crucial to be used as a base for evaluating the safety of spent fuel handling system and storage tank. This study is aimed to investigate the radionuclide characteristics of RDE spent fuel at the end of cycle and during the first 5 years cooling time in spent fuel storage. The method used to investigate the radionuclide characteristics is burnup calculation using ORIGEN2.1 code. In performing the ORIGEN2.1 calculation, one pebble fuel was assumed to be irradiated in the core for 5 cycles and then decayed for 5 years. At the end of the fifth cycle, it is obtained that the total activity, thermal power, neutron production, and photon release rates from all radionuclides inside one spent fuel are approximately 105.68 curies, 0.41 watts, 2.65 x 103 neutrons/second, and 1.79 x 104 photons/second, respectively. The results for the radionuclides characteristics during the first 5 years cooling time in the spent fuel storage show that the radioactivity characteristics from all radionuclides are rapidly decreasing at the first year and then slowly decreasing at the second until the fifth year of cooling time. The results obtained in this study can provide data for safety evaluation of fuel handling and spent fuel storage, such as the calculation of sourceterm, radiation dose rate, and the determination of radiation shielding.Keywords: RDE, spent fuel, radionuclide activity, thermal power, neutron production, photon releaserates KARAKTERISTIK RADIONUKLIDA DI DALAM BAHAN BAKAR RDE. Reaktor Daya Eksperimental (RDE) adalah reaktor tipe Reaktor Temperatur Tinggi Berpendingin Gas dengan daya termal 10MW yang akan dibangun oleh BadanTenagaNuklirNasional (BATAN) di kawasanPuspiptek, Tangerang Selatan. RDE menggunakan bahan bakar UO2 yang dilapisi dengan lapisan TRISO dan dimasukkan ke dalam teras RDE menurut skema multipass (5 siklus). Penentuan karakteristik radionuklida di dalam bahan bakar RDE; seperti aktivitas, daya termal, laju produksi neutron dan pelepasan foton; adalah sangat penting karena informasi karakteristik ini diperlukan sebagai dasar untuk melakukan evaluasi keselamatan system penanganan dan penyimpanan bahan bakar bekas. Penelitian ini bertujuan untuk menganalisis karakteristik radionuklida bahanbakar RDE setelah 5 siklus dan pada 5 tahun pertama pendinginan ditempat penyimpanan bahan bakar bekas. Metode yang digunakan dalam menghitung karakteristik radionuklida adalah menggunakan program ORIGEN2.1. Satu bola bahan bakar RDE diasumsikan diiradiasi selama 5 siklus dan kemudian meluruh selama 5 tahun. Pada akhir siklus, diperoleh hasil aktivitas total, daya termal, laju produksi neutron dan pelepasan foton dari seluruh radionuklida di dalam satu bola bahan bakar RDE sebesar 105,68 curies, 0,41 watts, 2,65 x 103 neutron/detik, dan 1,79 x 104 foton/detik. Hasil untuk karakteristik radionuklida selama 5 tahun penyimpanan menunjukkan bahwa karakteristik radioktivitas radionuklida menurun dengan cepat pada tahun pertama dan kemudian menurun lebih lambat pada tahun kedua hingga tahun kelima. Hasil perhitungan karakteristik radionuklida dari penelitian ini dapat digunakan sebagai basis untuk analisis keselamatan penanganan dan penyimpanan bahan bakarbekas RDE.Kata kunci:RDE, bahan bakar bekas, aktivitas radionuklida, daya termal, produksi neutron, laju foton

scholarly journals Spatial variations of Sr–Nd isotopic ratios, mineralogical and elemental compositions of cryoconite in an Alaskan glacier

2018 ◽  
Vol 59 (77) ◽  
pp. 147-158
Author(s):  
Naoko Nagatsuka ◽  
Nozomu Takeuchi ◽  
Ki-Cheol Shin ◽  
Takanori Nakano
Keyword(s):  
Spatial Variation ◽  
The Other ◽  
Isotopic Ratios ◽  
Organic Fraction ◽  
Nutrient Source ◽  
Silicate Mineral ◽  
Elemental Compositions ◽  
Mixing Ratios ◽  
Local Sources ◽  
Phosphate Silicate

ABSTRACTTo understand the geological origins of minerals in cryoconite and the nutrients sources for microbes on glaciers, we analyzed the Sr–Nd isotopic ratios of the four mineral fractions in cryoconites including saline, carbonate, phosphate, silicate and the organic fraction obtained from Gulkana Glacier in Alaska. The isotopes in the silicate mineral fraction exhibited spatial variation within the glacier (87Sr/86Sr: 0.704533–0.709563, εNd (0): −16.0 to 0.5), which can be explained by the different mixing ratios of the two distinct sources: one of the sources is lateral and terminal moraines or soil, and the other is the medial moraine of the glacier. The minerals in the cryoconite at the lower sites in the glacier are likely derived from the former source, whereas those at the upper sites are from latter sources. The mineralogical and elemental compositions also support mixing of the silicate minerals from the two local sources. The Sr isotopic ratios of the organic fraction also showed spatial variation on the glacier in the middle sites – a trend similar to those of the phosphate fraction. The results suggest that the organic matter is mostly the byproducts of microbes using the phosphate minerals as a nutrient source.

Long.Term Reactivity Change and Control: On.Power Refuelling

2021 ◽  
pp. 33-44
Author(s):  
Wei Shen ◽  
Benjamin Rouben
Keyword(s):  
Residence Time ◽  
Thermal Flux ◽  
Computer Code ◽  
Fuel Burnup ◽  
The Core ◽  
Time Integral ◽  
Fuel Bundle ◽  
Computer Codes ◽  
Neutron Exposure ◽  
And Control

There are 2 concepts related to the “age” of fuel: irradiation (fluence) and fuel burnup. The fuel irradiation in a given fuel bundle, denoted ω, is defined as the time integral of the thermal flux in the fuel during its residence time in the core. Another term for irradiation is fluence. Irradiation is also known as the thermal-neutron exposure of the fuel. The units of irradiation are neutrons/cm2, or more conveniently, neutrons per kilobarn, n/kb. Since the cut-off of the thermal-energy range may be defined differently in different computer codes, the fuel irradiation may vary from computer code to computer code, and caution must therefore be exercised when comparing irradiation values using different codes. In documents, it has been more and more usual to report values of fuel burnup rather than fuel irradiation, as burnup does not suffer from differences in definition between codes.

An Experimental and Numerical Study of Pressure Drop and Hydraulic Behavior in Scaled-Down Fuel Bundle

2013 ◽  
Vol 275-277 ◽  
pp. 409-412
Author(s):  
Duen Sheng Lee ◽  
Kai Ting Hsieh ◽  
Po Chih Tsao ◽  
Tzu Chen Hung ◽  
Yi Tung Chen ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Numerical Study ◽  
Spent Fuel ◽  
Rod Bundles ◽  
Cfd Simulations ◽  
Fuel Bundle ◽  
Acceptable Deviation ◽  
Spent Fuel Pool ◽  
Computational Fluid Dynamics Cfd ◽  
The Relationship

This study presents a scaled-down single fuel assembly experiment to simulate the fuel in the spent fuel pool (SFP). From experiment results, this study obtained the relationship among pressure drop and velocity, the viscous resistance and inertial resistance factor. In computational fluid dynamics (CFD) simulations, the large number of fuel rod bundles is approximated with porous medium technique that imposes similar flow resistance to the motion of the fluid. Difference of the pressure drop between numerical and experimental results is within acceptable deviation.

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