Towards Optimal In-Core Fuel Management of Thorium-Plutonium-Fuelled PWR Cores

2013 ◽  
Author(s):  
Nurjuanis Z. Zainuddin ◽  
Benjamin A. Lindley ◽  
Geoffrey T. Parks
Keyword(s):  
Nuclear Waste ◽  
Cycle Length ◽  
Feasibility Studies ◽  
Fuel Management ◽  
Loading Pattern ◽  
Burnable Poison ◽  
The Core ◽  
Mox Fuel ◽  
Operational Characteristics

Plutonium is a significant proliferation concern as well as a major contributor to the long-term toxicity of nuclear waste. Partial incineration in PWRs with uranium-MOX fuel is often considered to mitigate these concerns. Thorium-MOX is an alternative fuel with superior material properties and higher plutonium destruction rates, as shown in multiple feasibility studies. However, the core performance and operational characteristics (e.g. discharge burn-up, feasibility of controlling the core) are ultimately dependent on the core loading pattern (LP) and burnable poison (BP) design. In this paper, the LP for Th-Pu fuel of various compositions is optimized for (1) discharge burn-up, (2) radial form factor (RFF), (3) cycle length, (4) moderator temperature coefficient (MTC), and (5) reactivity swing over cycle. Maximizing the cycle length makes the discharge burn-up and reactivity swing worse due to placement of once- and twice-burnt fuel near the core periphery. It also makes the MTC less negative. The harder neutron spectrum of Th-Pu fuel compared to conventional U fuel favours the use of distributed integral burnable poisons to control the reactivity swing over the cycle. This leads to a significant amount of dissimilarity between LPs with relatively similar performance measures, and between optimal LPs for different Pu loadings in the fuel. The RFF can vary throughout the cycle but a careful placement of the assemblies can mitigate this. The cycle reactivity swing is controlled using enriched soluble boron, which makes the MTC worse, and this constrains feasibility for high Pu loading in the fuel.

scholarly journals Thorium based fuel loading pattern for PWR reactor

2019 ◽  
Vol 108 ◽  
pp. 01028 ◽  
Author(s):  
Mikolaj Oettingen
Keyword(s):  
Monte Carlo ◽  
Numerical Model ◽  
Pressurized Water Reactor ◽  
Fuel Management ◽  
Fuel Loading ◽  
Pressurized Water ◽  
Loading Pattern ◽  
The Core ◽  
Continuous Energy ◽  
Numerical Tools

The Monte Carlo Continuous Energy Burnup Code was used for numerical simulations of the pressurized water reactor (PWR) with mixed U-Th fuel. The thorium fuel was introduce to the core of the Westinghouse 4-loop PWR in order to investigate the time evolutions of fissile 233U, 235U, 239Pu, 241Pu and of fertile 232Th and 238U. The core loading pattern was designed using the Whole Assembly Seed and Blanket (WASB) approach. The following calculations show the feasibility of the proposed incore fuel management patter using the available numerical tools, developed numerical model and methods.

Transmission electron microscopy of alpha-decay damage and alteration of betafite

1987 ◽  
Vol 45 ◽  
pp. 376-377
Author(s):  
G. R. Lumpkin ◽  
R. C. Ewing
Keyword(s):  
Nuclear Waste ◽  
Pyrochlore Structure ◽  
Alpha Decay ◽  
Structure Type ◽  
Waste Form ◽  
Natural Analogue ◽  
The Core ◽  
Transmission Electron ◽  
Pyrochlore Group

The pyrochlore structure type occurs as a constituent of crystalline nuclear waste form assemblages proposed for the long term isolation of actinides. Betafite, the Ti-rich end-member of the pyrochlore group, is a natural analogue similar in composition to waste form pyrochlores. This study examines the effects of alpha-recoil damage and geochemical alteration on a specimen of betafite from Antanifotsy, Madagascar (Harvard no. 87876, UNM no. 205).Electron microprobe analyses were performed using a JEOL 733 Superprobe operated at 15 kV and 20 nA sample current crushed fragments of the sample were dispersed on holey-carbon grids and examined with a JEOL 2000 EX TEM operated at 200 kV. Phase compositions were checked using a Tracor TN5500 EDS.The 1.5 cm diameter betafite crystal displays an unusual zonal sequence of alteration. The core consists of relatively unaltered betafite containing ca. 27 wt.% U02 and 2.5 wt.% CaO (TABLE 1, analysis 1).

scholarly journals Application of Evolutionary Simulated Annealing Method to Design a Small 200 MWt Reactor Core

2021 ◽  
Vol 10 (4) ◽  
pp. 16-23
Author(s):  
Tran Viet Phu ◽  
Tran Hoai Nam ◽  
Hoang Van Khanh
Keyword(s):  
Simulated Annealing ◽  
Power Plant ◽  
Nuclear Power ◽  
Cycle Length ◽  
Reactor Core ◽  
Loading Pattern ◽  
The Core ◽  
Fuel Assemblies ◽  
Full Power ◽  
Annealing Method

This paper presents the application of an evolutionary simulated annealing (ESA) method to design a small 200 MWt reactor core. The core design is based on a reference ACPR50 reactor deployed in a floating nuclear power plant. The core consists of 37 typical 17x17 PWR fuel assemblies with three different U-235 enrichments of 4.45, 3.40 and 2.35 wt%. Core loading pattern (LP) has been optimized for obtaining the cycle length of 900 effective full power days, while minimizing the average U-235 enrichment and the radial power peaking factor. The optimization process was performed by coupling the ESA method with the COREBN module of the SRAC2006 system code.

Mixed Reload Design Using MOX and UOX Fuel Assemblies

2002 ◽  
Author(s):  
J. Ramo´n Rami´rez Sa´nchez ◽  
R. T. Perry
Keyword(s):  
Conceptual Design ◽  
Cycle Length ◽  
Multiplication Factor ◽  
The Core ◽  
Mox Fuel ◽  
Fuel Assemblies ◽  
Current Cycle ◽  
Full Power ◽  
Control Rods ◽  
Mixed Load

As part of the studies involved in plutonium utilization assessment for a Boiling Water Reactor, a conceptual design of MOX fuel was developed, this design is mechanically the same design of 10×10 BWR fuel assemblies but different fisil material. Several plutonium and gadolinium concentrations were tested to match the 18 months cycle length which is the current cycle length of LVNPP, a reference UO2 assembly was modeled to have a full cycle length to compare results, an effective value of 0.97 for the multiplication factor was set as target for 470 Effective Full Power days for both cycles, here the gadolinium concentration was a key to find an average fisil plutonium content of 6.55% in the assembly. A reload of 124 fuel assemblies was assumed to simulate the complete core, several load fractions of MOX fuel mixed with UO2 fresh fuel were tested to verify the shutdown margin, the UO2 fuel meets the shutdown margin when 124 fuel assemblies are loaded into the core, but it does not happen when those 124 assemblies are replaced with MOX fuel assemblies, so the fraction of MOX was reduced step by step up to find a mixed load that meets both length cycle and shutdown margin. Finally the conclusion is that control rods losses some of their worth in presence of plutonium due to a more hardened neutron spectrum in MOX fuel and this fact limits the load of MOX fuel assemblies in the core, this results are shown in this paper.

Observation by Sem/edxs of Leached Layers on SRL-165 Glass from 5-Year MIIT Test

1992 ◽  
Vol 294 ◽  
Author(s):  
Pedro B. Macedo ◽  
Andrew C. Buechele
Keyword(s):  
Nuclear Waste ◽  
Predictive Modeling ◽  
Thickness Measurement ◽  
Metal Interface ◽  
Partial Loss ◽  
The Core ◽  
Glass Corrosion ◽  
Glass Metal ◽  
Reliable Basis

ABSTRACTLong-term tests on the durability of nuclear waste glasses, both under laboratory conditions and in actual burial environments, have shown that after periods of several months or years the rates of glass corrosion can show unexpected increases. In burial tests in brine environments the growth of the thickness of the surface layer during years 3 to 5 as revealed by SIMS and SEM measurements was found to be faster than expected on the basis of findings during the first 2 years. In this paper we report on our SEM-EDXS observations of a 5 year burial sample of SRL-165 glass from the MIIT test, and compare our findings to those of other studies, especially SIMS measurements. Our average thickness measurement for the leached layer at the glass-metal interface is 3.70 μm, but wide variation is observed, as well as evidence of partial loss of the leached layer in some areas. A thicker, better retained layer is observed on the glass-brine interface near the core heater averaging 8 to 12 μm in thickness with occasional local attack producing leached layers of greater depth, in one case nearly 40 μm. These findings show that it is important to extend durability tests to long periods in order to establish a reliable basis for predictive modeling of long-term glass durability.

Russia’s Development Strategy: Guidelines and Restrictions

2008 ◽  
pp. 119-130 ◽  
Author(s):  
V. Senchagov
Keyword(s):  
Economic Development ◽  
Development Strategy ◽  
Conceptual Basis ◽  
The Core ◽  
Economic Development Strategy ◽  
Socio Economic Development ◽  
Rates Of Growth

The core of Russia’s long-term socio-economic development strategy is represented by its conceptual basis. Having considered debating points about the essence and priority of the strategy, the author analyzes the logic and stages of its development as well as possibilities, restrictions and risks of high GDP rates of growth.

scholarly journals Solubility Product of Vanadinite Pb5(VO4)3Cl at 25 °C—A Comprehensive Approach to Incongruent Dissolution Modeling

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 135
Author(s):  
Justyna Topolska ◽  
Bartosz Puzio ◽  
Olaf Borkiewicz ◽  
Julia Sordyl ◽  
Maciej Manecki
Keyword(s):  
Nuclear Waste ◽  
Solubility Product ◽  
Geochemical Modeling ◽  
Incongruent Dissolution ◽  
Mineral Solubility ◽  
Actual Application ◽  
Universal Approach ◽  
Solubility Constant ◽  
First Time

Although vanadinite (Pb5(VO4)3Cl) occurs in abundance in various terrestrial geochemical systems of natural and anthropogenic origin and is seriously considered as a potential nuclear waste sequestering agent, its actual application is severely limited by a lack of understanding of its basic thermodynamic parameters. In this regard, the greatest challenge is posed by its incongruent dissolution, which is a pivotal hurdle for effective geochemical modeling. Our paper presents an universal approach for geochemical computing of systems undergoing incongruent dissolution which, along with unique, long-term experiments on vanadinites’ stability, allowed us to determine the mineral solubility constant. The dissolution experiments were carried out at pH = 3.5 for 12 years. Vanadinite has dissolved incongruently, continuously re-precipitating into chervetite (Pb2V2O7) with the two minerals remaining in mutual equilibrium until termination of the experiments. The empirically derived solubility constant Ksp,V,298 = 10–91.89 ± 0.05 of vanadinite was determined for the first time. The proposed modeling method is versatile and can be adopted to other mineral systems undergoing incongruent dissolution.

Advanced First Core Design for the Westinghouse AP1000

2009 ◽  
Author(s):  
Robert J. Fetterman
Keyword(s):  
Fuel Cycle ◽  
The United States ◽  
Pressurized Water ◽  
Loading Pattern ◽  
The Core ◽  
Low Leakage ◽  
Fuel Assemblies ◽  
Cycle Loading ◽  
Water Reactors ◽  
Under Construction

As the nuclear renaissance is now upon us and new plants are either under construction or being ordered, a considerable amount of attention has also turned to the design of the first fuel cycle. Requirements for core designs originate in the Utilities Requirements Document (URD) for the United States and the European Utilities Requirements (EUR) for Europe. First core designs created during the development of these documents were based on core design technology dating back to the 1970’s, where the first cycle core loading pattern placed the highest enrichment fuel on the core periphery and two other lower enrichments in the core interior. While this sort of core design provided acceptable performance, it underutilized the higher enriched fuel assemblies and tended to make transition to the first reload cycle challenging, especially considering that reload core designs are now almost entirely of the Low Leakage Loading Pattern (LLLP) design. The demands placed on today’s existing fleet of pressurized water reactors for improved fuel performance and economy are also desired for the upcoming Generation III+ fleet of plants. As a result of these demands, Westinghouse has developed an Advanced First Core (AFCPP) design for the initial cycle loading pattern. This loading pattern design simulates the reactivity distribution of an 18 month low leakage reload cycle design by placing the higher enriched assemblies in the core interior which results in improved uranium utilization for those fuel assemblies carried through the first and second reload cycles. Another feature of the advanced first core design is radial zoning of the high enriched assemblies, which allows these assemblies to be located in the core interior while still maintaining margin to peaking factor limits throughout the cycle. Finally, the advanced first core loading pattern also employs a variety of burnable absorber designs and lengths to yield radial and axial power distributions very similar to those found in typical low leakage reload cycle designs. This paper will describe each of these key features and demonstrate the operating margins of the AFC design and the ability of the AFC design to allow easy transition into 18 month low leakage reload cycles. The fuel economics of the AFC design will also be compared to those of a more traditional first core loading pattern.

Semantic Desktop for the End-UserSemantic Desktop für Anwender

i-com ◽  
2009 ◽  
Vol 8 (3) ◽  
pp. 25-32 ◽  
Author(s):  
Gunnar Aastrand Grimnes ◽  
Benjamin Adrian ◽  
Sven Schwarz ◽  
Heiko Maus ◽  
Kinga Schumacher ◽  
...  
Keyword(s):  
Knowledge Management ◽  
Knowledge Work ◽  
Personal Knowledge ◽  
Term Study ◽  
The Core ◽  
Personal Knowledge Management ◽  
Long Term Study ◽  
Core Components

AbstractThis article describes the Semantic Desktop. We give insights into the core services that aim to improve personal knowledge management on the desktop. We describe these core components of our Semantic Desktop system and give evaluation results. Results of a long-term study reveal effects of using the Semantic Desktop on personal knowledge work.

Contrasting effects of fire on populations of two small rodent species in fragments of Atlantic Forest in Brazil

2004 ◽  
Vol 20 (2) ◽  
pp. 225-228 ◽  
Author(s):  
Marcos de Souza Lima Figueiredo ◽  
Fernando Antonio dos Santos Fernandez
Keyword(s):  
Atlantic Forest ◽  
Feedback System ◽  
Rodent Species ◽  
Primary Forest ◽  
Small Rodent ◽  
Forest Species ◽  
The Core ◽  
Higher Temperature ◽  
Disturbed Habitats

Habitat fragmentation causes a sharp increase in the forested area affected by edge effects (Murcia 1995). Compared with the core of the forest, edges present higher litterfall rates, air and soil humidity reduction, higher temperature and increased wind incidence (Bierregaard et al. 1992, Didham & Lawton 1999, Laurance et al. 1998, Matlack 1993). These features of edges may increase the probability of fire occurrence, especially if the surrounding vegetation is composed of grasses (D'Antonio & Vitousek 1992, Freifelder et al. 1998). After a fire, the damaged edge will grow substantial amounts of herbaceous vegetation, extending the inflammable area into the forest, and thereby creating a positive feedback system of fire susceptibility and intensity (Cochrane & Schulze 1999, Cochrane et al. 1999). Fires may affect the structure and composition of the vegetation (Cochrane & Schulze 1999, Didham & Lawton 1999, Sanaiotti & Magnusson 1995), favouring, in the long-term, the dominance of the community by species characteristic of disturbed habitats and making the habitat unsuitable to primary forest species (Malcolm 1994, Possingham et al. 1994). Unfortunately, there are few studies on the effects of fires on neotropical small-mammal populations (Borchert & Hansen 1983, Ojeda 1989, Vieira & Marinho-Filho 1998). The objective of this study was to analyse the influence of a fire on populations of two rodent species, Akodon cursor (Winge) and Oecomys concolor (Wagner) in two fragments of Atlantic Forest in Brazil.

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