Imperial College London

Dr Andrew Buchan

Faculty of EngineeringDepartment of Earth Science & Engineering

Honorary Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 7325andrew.buchan

 
 
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Location

 

4.91Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

37 results found

Buchan AG, Pain CC, 2016, An efficient space-angle subgrid scale discretisation of the neutron transport equation, Annals of Nuclear Energy, Vol: 94, Pages: 440-450, ISSN: 1873-2100

Journal article

Heaney CE, Buchan AG, Pain CC, Jewer Set al., A reduced order model for criticality problems in reactor physics varyingcontrol rod settings, Proceedings of the 24 th UK Conference of the Association for Computational Mechanics in Engineering

Conference paper

Dargaville S, Goffin MA, Buchan AG, Pain CC, Smedley-Stevenson RP, Smith PN, Gorman Get al., 2015, Solving the Boltzmann transport equation with multigrid and adaptive space/angle discretisations, ANNALS OF NUCLEAR ENERGY, Vol: 86, Pages: 99-107, ISSN: 0306-4549

Journal article

Adam A, Buchan AG, Piggott MD, Pain CC, Hill J, Goffin MAet al., 2015, Adaptive Haar wavelets for the angular discretisation of spectral wave models, Journal of Computational Physics, Vol: 305, Pages: 521-538, ISSN: 1090-2716

A new framework for applying anisotropic angular adaptivity in spectral wave modelling is presented. The angular dimension of the action balance equation is discretised with the use of Haar wavelets, hierarchical piecewise-constant basis functions with compact support, and an adaptive methodology for anisotropically adjusting the resolution of the angular mesh is proposed. This work allows a reduction of computational effort in spectral wave modelling, through a reduction in the degrees of freedom required for a given accuracy, with an automated procedure and minimal cost.

Journal article

Buchan AG, Calloo AA, Goffin MG, Dargaville S, Fang F, Pain CC, Navon IMet al., 2015, A POD reduced order model for resolving angular direction in neutron/photon transport problems, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 296, Pages: 138-157, ISSN: 0021-9991

Journal article

Xiao D, Fang F, Buchan AG, Pain CC, Navon IM, Muggeridge Aet al., 2015, Non-intrusive reduced order modelling of the Navier-Stokes equations, COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING, Vol: 293, Pages: 522-541, ISSN: 0045-7825

Journal article

Goffin MA, Buchan AG, Dargaville S, Pain CC, Smith PN, Smedley-Stevenson RPet al., 2015, Goal-based angular adaptivity applied to a wavelet-based discretisation of the neutral particle transport equation, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 281, Pages: 1032-1062, ISSN: 0021-9991

Journal article

Buchan AG, Jewer S, Farrell PE, Pain CC, Cacuci DG, Moatamedi Met al., 2014, Simulating coupled neutron-fluid-heat transfer for the study of unintended operatingscenarios in pressure water reactors using an immersed body modelling technique, NAFEMS

Conference paper

Goffin MA, Buchan AG, Belme AC, Pain CC, Eaton MD, Smith PN, Smedley-Stevenson RPet al., 2014, Goal-based angular adaptivity applied to the spherical harmonics discretisation of the neutral particle transport equation, ANNALS OF NUCLEAR ENERGY, Vol: 71, Pages: 60-80, ISSN: 0306-4549

Journal article

Merton SR, Smedley-Stevenson RP, Pain CC, Buchan AGet al., 2014, Adjoint eigenvalue correction for elliptic and hyperbolic neutron transport problems, PROGRESS IN NUCLEAR ENERGY, Vol: 76, Pages: 1-16, ISSN: 0149-1970

Journal article

Jewer S, Buchan AG, Pain CC, Cacuci DGet al., 2014, An immersed body method for coupled neutron transport and thermal hydraulic simulations of PWR assemblies, ANNALS OF NUCLEAR ENERGY, Vol: 68, Pages: 124-135, ISSN: 0306-4549

Journal article

Xiao D, Fang F, Buchan AG, Pain CC, Navon IM, Du J, Hu Get al., 2014, Non-linear model reduction for the Navier-Stokes equations using residual DEIM method, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 263, Pages: 1-18, ISSN: 0021-9991

Journal article

Buchan AG, Farrell PE, Gorman GJ, Goddard AJH, Eaton MD, Nygaard ET, Angelo PL, Smedley-Stevenson RP, Merton SR, Smith PNet al., 2014, The immersed body supermeshing method for modelling reactor physics problems with complex internal structures, ANNALS OF NUCLEAR ENERGY, Vol: 63, Pages: 399-408, ISSN: 0306-4549

Journal article

Ardjmandpour N, Pain CC, Fang F, Buchan AG, Singer J, Player MA, Xu X, Navon IM, Carter Jet al., 2014, Reduced order borehole induction modelling, INTERNATIONAL JOURNAL OF COMPUTATIONAL FLUID DYNAMICS, Vol: 28, Pages: 140-157, ISSN: 1061-8562

Journal article

Buchan AG, Pain CC, Fang F, Navon IMet al., 2013, A POD reduced-order model for eigenvalue problems with application to reactor physics, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Vol: 95, Pages: 1011-1032, ISSN: 0029-5981

Journal article

Baker CMJ, Buchan AG, Pain CC, Tollit BS, Goffin MA, Merton SR, Warner Pet al., 2013, Goal based mesh adaptivity for fixed source radiation transport calculations, Annals of Nuclear Energy, Vol: 55, Pages: 169-183, ISSN: 0306-4549

Journal article

Merton SR, Buchan AG, Pain CC, Smedley-Stevenson RPet al., 2013, An adjoint-based method for improving computational estimates of a functional obtained from the solution of the Boltzmann Transport Equation, ANNALS OF NUCLEAR ENERGY, Vol: 54, Pages: 1-10, ISSN: 0306-4549

Journal article

Xiao D, Fang F, Du J, Pain CC, Navon IM, Buchan AG, ElSheikh AH, Hu Get al., 2013, Non-linear Petrov–Galerkin methods for reduced order modelling of the Navier–Stokes equations using a mixed finite element pair, Computer Methods in Applied Mechanics and Engineering, Vol: 255, Pages: 147-157, ISSN: 0045-7825

Journal article

Buchan AG, Pain CC, Tollit TS, Gomes JLMA, Eaton MD, Gorman GJ, Cooling CM, Goddard AJH, Nygaard ET, Angelo PL, Smith PNet al., 2013, Simulated spatially dependent transient kinetics analysis of the Oak Ridge Y12 plant criticality excursion, Progress in Nuclear Energy, Vol: 63, Pages: 12-21

In June 1958 an accidental nuclear excursion occurred in the C-1 Wing of building 9212 in a process facility designed to recover enriched Uranium U(93) from various solid wastes. The accident was caused by the inadvertent flow of enriched uranyl nitrate into a 55 gallon drum which established a prompt critical nuclear excursion. Following the initial fission spike the nuclear system oscillated in power. The reaction was eventually terminated by the additional water which was flowing into the drum. The criticality excursion was estimated to have lasted approximately 20 min based upon nearby radiation measurement equipment with an estimated total fission yield of 1.3 × 1018 fissions of which the first fission spike contributed 6 × 1016 fissions.The traces from the radiation measurement devices indicated that most of the fissions occurred in the first 2.8 min, in which case the average power required for the observed fission yield was approximately 220 kW. After the first 2.8 min the system was postulated to have boiled causing a sharp decrease in density and reactivity of the system. This boiling probably reduced the power output from the system to a low level for the final 18 min of the excursion. This paper will aim to investigate the subsequent evolution of the Y12 excursion using the fundamentally based spatially dependent neutron/multiphase CFD kinetics simulation tool - FETCH. The reconstruction of the Y12 excursion using FETCH will follow the evolution of the excursion up until the uranyl nitrate starts to boil. The results of the FETCH simulation are presented and compared against the known measurements of the excursion from the radiation detection instruments located near the drum.

Journal article

Baker CMJ, Buchan AG, Pain CC, Farrell PE, Eaton MD, Warner Pet al., 2013, Multimesh anisotropic adaptivity for the Boltzmann transport equation, Annals of Nuclear Energy, Vol: 53, Pages: 411-426

This article presents a new adaptive finite element based method for the solution of the spatial dimensions of the Boltzmann transport equation. The method applies a curvature based error metric to locate the under and over resolved regions of a solution and this, in turn, is used to guide the refinement and coarsening of the spatial mesh. The error metrics and re-meshing procedures are designed such that they enable anisotropic resolution to form in the mesh should it be appropriate to do so. The adaptive mesh enables the appropriate resolution to be applied throughout the whole domain of a problem and so increase the efficiency of the solution procedure. Another new approach is also described that allows independent adaptive meshes to form for each of the energy group fluxes. The use of independent meshes can significantly improve computational efficiency when solving problems where the different group fluxes require high resolution over different regions. The mesh to mesh interpolation is made possible through the use of a ‘supermeshing’ procedure that ensures the conservation of particles when calculating the group to group scattering sources. Finally it is shown how these methods can be incorporated within a solver to resolve both fixed source and eigenvalue problems. A selection of both fixed source and eigenvalue problems are solved in order to demonstrate the capabilities of these methods.

Journal article

Goffin MA, Baker CMJ, Buchan AG, Pain CC, Eaton MD, Smith PNet al., 2013, Minimising the error in eigenvalue calculations involving the Boltzmann transport equation using goal-based adaptivity on unstructured meshes, Journal of Computational Physics, Vol: 242, Pages: 726-762

This article presents a method for goal-based anisotropic adaptive methods for the finite element method applied to the Boltzmann transport equation. The neutron multiplication factor, keff, is used as the goal of the adaptive procedure. The anisotropic adaptive algorithm requires error measures for keff with directional dependence. General error estimators are derived for any given functional of the flux and applied to keff to acquire the driving force for the adaptive procedure. The error estimators require the solution of an appropriately formed dual equation. Forward and dual error indicators are calculated by weighting the Hessian of each solution with the dual and forward residual respectively. The Hessian is used as an approximation of the interpolation error in the solution which gives rise to the directional dependence. The two indicators are combined to form a single error metric that is used to adapt the finite element mesh. The residual is approximated using a novel technique arising from the sub-grid scale finite element discretisation. Two adaptive routes are demonstrated: (i) a single mesh is used to solve all energy groups, and (ii) a different mesh is used to solve each energy group. The second method aims to capture the benefit from representing the flux from each energy group on a specifically optimised mesh. The keff goal-based adaptive method was applied to three examples which illustrate the superior accuracy in criticality problems that can be obtained.

Journal article

Buchan AG, Pain CC, Umpleby AP, Smedley-Stevenson RPet al., 2012, A sub-grid scale finite element agglomeration multigrid method with application to the Boltzmann transport equation, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Vol: 92, Pages: 318-342, ISSN: 0029-5981

Journal article

Buchan A, Eaton MD, Goddard AJH, Pain CCet al., 2012, Simulated transient dynamics and heat transfer characteristics of the water boiler nuclear reactor SUPO with cooling coil heat extraction, Annals of nuclear energy, Vol: 48, Pages: 68-83

The term “water boiler” reactor refers to a type of aqueous homogeneous reactor (AHR) that was designed, built and operated by Los Alamos in the 1940s. This was the first type of liquid fuelled reactor and the first to be fuelled with enriched Uranium. For security reasons the term “water boiler” was adopted and three versions were built: LOPO (for low power), HYPO (for high power) and SUPO (for super power) which were spherical shaped reactor vessels. The name was appropriate as the reactors appeared to boil although this was actually due to the release of radiolytic gas bubbles; although SUPO was operated during some studies close to the boiling point of uranyl nitrate. The final water boiler “SUPO” was operated almost daily as a neutron source from 1951 until its deactivation in 1974-23 years of safe, reliable operation. Many of the key neutron measurements needed in the design of the early atomic weapons were made using LOPO, HYPO and SUPO. More recently SUPO has been considered as a benchmark for quasi-steady-state operation of AHRs with internal cooling structures.This paper presents modelling and analysis of the coupled neutronic and fluid time dependent characteristics of the SUPO reactor. In particular the quasi-steady-state dynamics of SUPO have been investigated together with its heat transfer characteristics. In the simulations presented the SUPO reactor is modelled using the spatially dependent neutron/multiphase CFD simulation tool, FETCH, at a quasi-steady-state power of 25 kW. SUPO also possessed a cooling coil system that fed cooling water through the reactor for the extraction of the fission and decay heat. This cooling system, and the heat extraction, is modelled in the simulations using a new sub-modelling approach that is detailed here. The results from this simulation, such as gas fraction, gas generation rate, coolant rate and average temperature, are compared against the available experimental information.

Journal article

Baker CMJ, Buchan AG, Pain CC, Tollit B, Eaton MD, Warner Pet al., 2012, Quadratic inner element subgrid scale discretisation of the Boltzmann transport equation, Annals of Nuclear Energy, Vol: 45, Pages: 124-137

This paper explores the application of the inner element subgrid scale method to the Boltzmann transport equation using quadratic basis functions. Previously, only linear basis functions for both the coarse scale and the fine scale were considered. This paper, therefore, analyses the advantages of using different coarse and subgrid basis functions for increasing the accuracy of the subgrid scale method. The transport of neutral particle radiation may be described by the Boltzmann transport equation (BTE) which, due to its 7 dimensional phase space, is computationally expensive to resolve. Multi-scale methods offer an approach to efficiently resolve the spatial dimensions of the BTE by separating the solution into its coarse and fine scales and formulating a solution whereby only the computationally efficient coarse scales need to be solved. In previous work an inner element subgrid scale method was developed that applied a linear continuous and discontinuous finite element method to represent the solution’s coarse and fine scale components. This approach was shown to generate efficient and stable solutions, and so this article continues its development by formulating higher order quadratic finite element expansions over the continuous and discontinuous scales. Here it is shown that a solution’s convergence can be improved significantly using higher order basis functions. Furthermore, by using linear finite elements to represent coarse scales in combination with quadratic fine scales, convergence can also be improved with only a modest increase in computational expense.

Journal article

Nygaard ET, Pain CC, Eaton MD, Gomes JLMA, Goddard AJH, Gorman GJ, Tollit B, Buchan AG, Cooling CM, Angelo PLet al., 2012, Steps Towards Verification and Validation of the FETCH Code for Level 2 Analysis, Design and Optimization of Aqueous Homogeneous Reactors, PHYSOR

Conference paper

Buchan AG, Pain CC, Eaton MD, Gomes JLMA, Gorman GJ, Cooling CM, Goddard AJH, Nygaard ET, Glenn DE, Angelo PLet al., 2011, Dynamics and heat transfer characteristics of the water boiler reactor - SUPO, International Conference in Nuclear Criticality

Conference paper

Buchan AG, Pain CC, Eaton MD, Gomes JLMA, Gorman GJ, Cooling CM, Goddard AJH, Nygaard ET, Glenn DE, Angelo PNet al., 2011, Simulated spatially dependent transient kinetics analysis of the oak ridge Y12 Plant criticality excursion, International Conference in Nuclear Criticality, International Conference in Nuclear Criticality

Conference paper

Baker CMJ, Buchan AG, Pain CC, Tollit B, Goffin MA, Eaton MD, Merton SR, Smedley Stevenson PN, Warner Pet al., 2011, Anisotropic mesh adaptivity for eigenvalue calculations using energy dependent meshes, International Conference in Nuclear Criticalit

Conference paper

Merton SR, Smedley-Stevenson RP, Pain CC, ElSheikh AH, Buchan AGet al., 2011, An Adjoint Based Scheme for Eigenvalue Error Improvement, International Conference on Mathematics, Computational Methods & Reactor Physics

Conference paper

Buchan AG, Merton SR, Pain CC, Smedley-Stevenson RPet al., 2011, Riemann boundary conditions for the Boltzmann transport equation using arbitrary angular approximations, ANNALS OF NUCLEAR ENERGY, Vol: 38, Pages: 1186-1195, ISSN: 0306-4549

Journal article

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